Volume 69 Number 1 Fishery Bulletin U.S. DEPARTMENT OF COMMERCE 69 '^'^ National Oceanic and Atmospheric AdministJ^gpj^g gj^i^gj^g, ^^^^^^^^^^ NatJona! Marine Fisheries Service LIBRA- MAY 171971 WOODS HOLE, .vJASS. Vol. 69, No. 1 January 1971 ROEDEL, PHILIP M. In Memoriam — Wilbert McLeod Chapman and Milner Baily Schaefer . 1 AHLSTROM, ELBERT H. Kinds and abundance of fish larvae in the eastern tropical Pacific, based on collections made on EASTROPAC I 3 SMILES, MICHAEL C, JR., and WILLIAM G. PEARCY. Size structure and growth rate of Euphausia pacifica off the Oregon coast '^9 THOMAS, WILLIAM H., and ROBERT W. OWEN, JR. Estimating phytoplankton production from ammonium and chlorophyll concentrations in nutrient-poor water of the eastern tropical Pacific Ocean 87 CLUTTER, ROBERT I., and GAIL H. THEILACKER. Ecological efficiency of a pelagic mysid shrimp; estimates from growth, energy budget, and mortality studies 93 ROTHSCHILD, BRIAN J., and JAMES W. BALSIGER. A linear-programming solu- tion to salmon management ^^'^ DUBROW, DAVID L., and BRUCE R. STILLINGS. Chemical and nutritional char- acteristics of fish protein concentrate processed from heated whole red hake, Urophycis chitss '■^'■ DUBROW, DAVID L., NORMAN L. BROWN, E. R. PARISER, HARRY MILLER, JR., V. D. SIDWELL, and MARY E. AMBROSE. Eflfect of ice storage on the chemical and nutritive properties of solvent-extracted whole fish — red hake, Urophycis cJuiss 145 CREAR, DAVID, and IRWIN HAYDOCK. Laboratory rearing of the desert pupfish, Cyprinodon inacularius ^^^ HAYDOCK, IRWIN. Gonad maturation and hormone-induced spawning of the gulf croaker, Bairdiella icistia l" ' SECKEL, GUNTER R., and MARION Y. Y. YONG. Harmonic functions for sea-surface temperatures and salinities, Koko Head, Oahu, 1956-69, and sea-surface temperatures, Christmas Island, 1954-69 181 JELLINEK, GISELA, and MAURICE E. STANSBY. Masking undesirable flavors in fish oils 215 COOK, HARRY L., and M. ALICE MURPHY. Early developmental stages of the brown shrimp, Penaeus aztecxts Ives, reared in the laboratory 223 KOURY, BARBARA, JOHN SPINELLI, and DAVE WIEG. Protein autolysis rates at various pH's and temperatures in hake, Merluccius productus, and Pacific herring, Clupea harengus pallasi, and their effect on yield in the preparation of fish protein concentrate 241 Notes EMILIANI, DENNIS A. Equipment for holding and releasing penaeid shrimp during marking experiments 247 TOPP, ROBERT W., and FRANK H. HOFF. An adult bluefin tuna, Thimnus thynnua, from a Florida west coast urban waterway 251 U.S. DEPARTMENT OF COMMERCE Maurice H. Stans, Secretary NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION NATIONAL MARINE FISHERIES SERVICE Philip M. Roedel, Director FISHERY BULLETIN The Fishery Bulletin carries technical reports on investigations in fishery science. The Bulletin of the United States Fish Commission was begun in 1881; it became the Bulletin of the Bureau of Fisheries in 1904 and the Fishery Bulletin of the Fish and Wildlife Service in 1941. Separates were issued as documents through volume 46; the last document was No. 1103. Beginning with volume 47 in 1931 and continuing through volume 62 in 1963, each separate appeared as a numbered bulletin. A new system began in 1963 with volume 63 in which papers are bound together in a single issue of the bulletin instead of being issued individually. Bulletins are distributed free to libraries, research institutions, State agencies, and scientists. Some Bulle- tins are for sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402. EDITOR Dr. Reuben Lasker Scientific Editor, Fishery Bulletin National Marine Fisheries Service Fishery-Oceanography Center La Jolla, California 92037 Editorial Committee Dr. Elbert H. Ahlstrom National Marine Fisheries Service Dr. William H. Bayliff Inter-American Tropical Tuna Commission Dr. Daniel M. Cohen National Marine Fisheries Service Dr. Howard M. P'eder University of Alaska Mr. .John E. Fitch California Department of Fish and Game Dr. Marvin D. Grosslein National Marine Fisheries Service Dr. J. Frank Hebard National Marine Fisheries Service Dr. John R. Hunter National Marine Fisheries Service Mr. John C. Marr Food and Agriculture Organization of the United Nations Dr. Arthur S. Merrill National Marine Fisheries Service Dr. Virgil J. Norton University of Rhode Island Mr. Alonzo T. Pruter National Marine Fisheries Service Dr. Theodore R. Rice National Marine Fisheries Service Dr. Brian J. Rothschild University of Washington Dr. Oscar E. Sette National Marine Fisheries Service Mr. Maurice E. Stansby National Marine Fisheries Service Dr. Majmard A. Steinberg National Marine Fisheries Service Dr. Roland L. Wigley National Marine Fisheries Service rfi"^ CONTENTS Vol, 69, No. 1 January 1971 ROEDEL, PHILIP M. In Memoriam — Wilbert McLeod Chapman and Milner Baily Schaefer 1 AHLSTROM, ELBERT H. Kinds and abundance of fish larvae in the eastern tropical Pacific, based on collections made on EASTROPAC I ^ SMILES, MICHAEL C, JR., and WILLIAM G. PEARCY. Size structure and growth rate of Euphausia pacifica off the Oregon coast ^^ •THOMAS, WILLIAM H., and ROBERT W. OWEN, JR. Estimating phytoplankton production from ammonium and chlorophyll concentrations in nutrient-poor water of the eastern tropical Pacific Ocean 87 CLUTTER, ROBERT I., and GAIL H. THEILACKER. Ecological eiBciency of a pelagic mysid shrimp; esti- mates from growth, energy budget, and mortality studies 93 ROTHSCHILD, BRIAN J., and JAMES W. BALSIGER. A linear-programming solution to salmon management . 117 DUBROW, DAVID L., and BRUCE R. STILLINGS. Chemical and nutritional characteristics offish protein concentrate processed from heated whole red hake, Urophycis chuss 141 DUBROW, DAVID L., NORMAN L. BROWN, E. R. PARISER, HARRY MILLER, JR., V. D. SIDWELL, and MARY E. AMBROSE. Effect of ice storage on the chemical and nutritive properties of solvent-extracted whole fish — red hake, Urophycis chuss 145 CREAR, DAVID, and IRWIN HAYDOCK. Laboratory rearing of the desert pupfish, Cyprinodon macularius . . 151 HAYDOCK, IRWIN. Gonad maturation and hormone-induced spawning of the gulf croaker, Bairdiella icistia 157 SECKEL, GUNTER R., and MARION Y. Y. YONG. Harmonic functions for sea-surface temperatures and sa- linities, Koko Head, Oahu, 1956-69, and sea-surface temperatures, Christmas Island, 1954-69 181 JELLINEK, GISELA, and MAURICE E. STANSBY. Masking undesirable flavors in fish oils 215 COOK, HARRY L., and M. ALICE MURPHY. Early developmental stages of the brown shrimp, Penaeus aztecus Ives, reared in the laboratory 223 KOURY, BARBARA, JOHN SPINELLI, and DAVE WIEG. Protein autolysis rates at various pH's and temper- atures in hake, Merluccius producUis, and Pacific herring, Clupea harengus pallasi, and their effect on yield in the preparation of fish protein concentrate 241 Notes EMILIANI, DENNIS A. Equipment for holding and releasing penaeid shrimp during marking experiments .... 247 TOPP, ROBERT W., and FRANK H. HOFF. An adult bluefin tuna, Thunnus thynnus, from a Florida west coast urban waterway "^l Wilbert McLeod Chapman Milner Baily Schaefer IN MEMORIAM Wilbert McLeod Chapman and Milner Baily Schaefer '0^: lea / - < Ilu I LIBRARY \':^\ «^. A ^ Fisheries science in particular and society in general suffered two tragic losses within the period of only a month with the deaths of W. M. Chapman on June 25, 1970, and M. B. Schaefer on July 26, 1970. It is indeed a strange and sad commentary that these two men whose careers were intimately entwined since college days should pass within such a short time of each other. Death is never easy to accept; it is particu- larly hard to do so when it occurs at an untimely age. Both of these brilliant men, we would have hoped, would have been with us for years to come. Both were unique, each in his own way, and while the world adjusts to such events, each is in a very real sense irreplaceable. I had the opportunity to work rather closely with both of them in California over most of the past two decades. Wib Chapman was a member of the California Marine Research Com- mittee for many years, during most of which I served as that body's secretary. It was a chal- lenge to try to capture the essence of his re- marks. The breadth of his knowledge and the incisiveness of his thinking stimulated all of us to higher goals, and we who were close to him are better today for the good fortune of his friendship. "Benny" Schaefer was equally brilliant. His expositions on the scientific method and pop- ulation dynamics before the Inter-American Tropical Tuna Commission were models of trans- lation into lay terms of highly complex mathe- matical theories applied to living resources. Again a personal note. A few years ago Benny was a consultant to the California Department of Fish and Game during the formation of that body's Fish and Wildlife Plan and we worked closely in developing the philosophy behind the sections concerned with living marine resources. His imprint is deeply ingrained in that docu- ment and in subsequent legislation, as well as in my thinking. And, as Wib Chapman had a large input in that task, so did Benny into the deliberations of the Marine Research Committee. Meantime both worked diligently as members of the Cal- ifornia Marine Advisory Committee on Marine and Coastal Affairs. While these men will right- fully be remembered for their major contribu- tions to national and international affairs, their energy and interests were such that they en- compassed an amazingly broad spectrum. Each of their contributions to the State of California is more than most men could accomplish in a lifetime devoted to that pursuit alone. One hears parallel stories throughout the scientific and fisheries communities. Wilbert McLeod Chapman was born in Ka- lama, Washington, on March 31, 1910. He died in San Diego, California, on June 25, 1970, and is survived by his wife of 35 years, Mary Eliza- beth, and five of their six children. He did both his undergraduate and graduate work at the University of Washington, obtaining his Ph.D. (fisheries) in 1937. His publications, ranging from morphology and systematic ich- thyology through fisheries economics and inter- national law, number some 250. One of these. Fishing in Troubled Waters, is a book recounting his experiences as a fisheries development oflicer in the South Pacific during World War II. It is fascinating reading and makes one regret all the more that the other books he had in mind will never be forthcoming. He was particularly proud of his papers on systematics and morphol- ogy and always spoke fondly of that part of his career. His honors were many: among them he was a Fellow of the Guggenheim Foundation and of the California Academy of Sciences, .Man of the Year of the National Fisheries Institute in 1966, and the recipient of the First Sea Grant College Award in 1968. He began his professional career in 1933 with the International Fisheries (now Halibut) Com- mission. He was later employed by the Wash- ington State Department of Fisheries, the U.S. Fish and Wildlife Service, and, in 1943, by the California Academy of Sciences where he was Curator of Fishes until 1947. It was during this period that he served in a civilian capacity in the South Pacific, his job being to develop sub- sistence fisheries at advanced island bases. In 1947, Dr. Chapman became director of the School of Fisheries at the University of Wash- ington. He left there in 1948 to become the first Special Assistant to the Under Secretary of State for Fish and Wildlife. In 1951 he be- came Director of Research for the American Tunaboat Association; a decade later he joined the Van Camp Sea Food Company as Director of the Division of Resources. When Van Camp was acquired by the Ralston Purina Company in 1968, he became Director, Marine Resources, of that firm, a position he held until his death. Milner Baily Schaefer was born in Cheyenne, Wyoming, on December 14, 1912. He died in San Diego, California, on July 26, 1970. He is survived by his wife, Isabella, and three children. Dr. Schaefer obtained his B.S. degree cum laude from the University of Washington in 1936 and his doctorate from the same institution in 1950. He worked for the Washington State Department of Fisheries from 1935 to 1938 and for the International Pacific Salmon Fisheries Commission from 1938 until 1942. Following wartime duty with the Navy, he joined the U.S. Fish and Wildlife Service in 1946, serving first as a fishery research biologist in the South Pacific Fisheries Investigations at Stanford, and from 1948 to 1950 as Chief, Research & Development, Pacific Oceanic Fish- ery Investigations in Honolulu. He became Director of Investigations of the Inter-American Tropical Tuna Commission in 1951, holding that post until he became Director of the Institute of Marine Resources and Pro- fessor of Oceanography, Scripps Institution of Oceanography, University of California, in 1962. He remained there until his death save for an 18-month period in 1967-69 during which he was Science Adviser to Secretary of the Interior Stewart Udall. Among other honors, he was a fellow of the California Academy of Sciences and a member of the National Academy of Sciences. He wrote more than 100 scientific papers, particularly in the area of population djTiamics and fisheries development and utilization. He served on a multitude of panels at the international, national and state levels. Despite his huge workload, he always found time to discuss individual problems with people both large and small, and to ad- minister and develop first the Inter-American Tropical Tuna Commission and later the Insti- tute of Marine Resources in an exemplarj' man- ner, setting standards for each that others will be hard-pressed to equal. This recitation cannot give a measure of these men: their unflagging energy, their knowledge in fields far apart from fisheries, their ability as raconteurs, their good fellowship. Nor does it give a measure of their contributions to the nation and to the world, contributions that will help make it a better place in which to live for a long time to come. Philip M. Roedel KINDS AND ABUNDANCE OF FISH LARVAE IN THE EASTERN TROPICAL PACIFIC, BASED ON COLLECTIONS MADE ON EASTROPAC I Elbert H. Ahlstrom' ABSTRACT This paper deals with kinds and counts of fish larvae obtained in 482 oblique plankton hauls taken over an extensive area of the eastern tropical Pacific on EASTROPAC I, a four-vessel cooperative survey made during February-March 1967. On the basis of abundance of larvae, the dominant fish group in oceanic waters are the myctophid lanternfishes (47 %), gonostomatid lightfishes (23 %), hatchetfishes, Stemoptychidae (6 %), bathylagid smelts (5 %). Scombrid larvae ranked fifth, and ex- ceeded 2 % of the count. Two kinds of larvae were outstandingly abundant : larvae of the lantemfish Diogenichthys latematus made up over 25 % of the total, while larvae of the gonostomatid genus Vinciguerria made up almost 20 %. More fish larvae were obtained per haul, on the average, in the eastern tropical Pacific than were obtained per haul in the intensively surveyed waters of the California Current region off Cal- ifornia and Baja California. EASTROPAC I was the first and most wide- ranging of a series of cooperative cruises made in tlie eastern tropical Pacific between February 1967 and April 1968. A vast expanse of the eastern tropical Pacific was surveyed on EAS- TROPAC I, extending from lat 20° N to 20° S, and from the American coasts ofi'shore to long 126° W (Fig. 1). Four research vessels par- ticipated in EASTROPAC I: Alaminos oper- ated by Texas A & M, occupied the inner pat- tern, while Rockaway operated by the U.S. Coast Guard, David Star?- Jordan operated by the Bureau of Commercial Fisheries (now the National Marine Fisheries Service), and Argo operated by the Scripps Institution of Ocean- ography, occupied patterns successively seaward. The oceanographic, biological, and meteorolog- ical data collected on EASTROPAC cruises will be graphically presented in a series of EAS- TROPAC atlases, including generalized charts dealing with fish eggs and larvae. The present paper is the result of a chain of events that began 2 decades ago, at the initiation of CalCOFI (California Cooperative Oceanic Fisheries Investigations) in which a large-scale sea program was set up to investigate the distri- ' National Marine Fisheries Service Fishery-Ocean- ography Center, La JoUa, Calif. 92037. bution and abundance of sardine spawning, and the factors underlying fluctuations in survival of the early life-history stages of sardines. The plankton collections not only contained eggs and larvae of sardine but those of most other pelagic fishes in the California Current region. A de- cision was made to attempt to identify and enu- merate all fish larvae in the collections in order to obtain more precise information about the eco- logical associates of the sardine. At that time few fish larvae, other than those of the sardine and anchovy, could be identified. Within a few years most kinds of fish larvae were identified to genus or species. Once the larvae were identified and enumerated, it be- came obvious that this was an exceptionally use- ful tool for evaluating fish resources. Most oceanic fishes have pelagic eggs and/or larvae that are distributed in or just below the photic zone, i.e. within the upper 150 to 200 m of depth. At no other time in their life histories are so many kinds of fishes associated together — deep- sea fishes (mesopelagic and bathypelagic) as well as epipelagic species — where they can be collected quantitatively with a single type of gear, a plankton net. Once the larvae of the pelagic fish fauna of a region, such as those in the California Cur- rent region, are known, there is a large trans- Manuscript received September 1970. FISHERY BULLETIN: VOL. 69, NO. I, 1971. FISHERY BULLETIN: VOL. 69. NO. I 90° 80° Figure 1. — Location of plankton stations occupied by four research vessels participating in EASTROPAC I. Symbols for vessels indicated in legend above. Samples collected from Argo are numbered as 11.000 series (as 11.022, 11.173), samples from David Starr Jordan as 12.000 series, Rockaway samples as 13.000 series and Alaminos samples as 14.000 series. f erence of the accumulated knowledge and skills for work in other areas, such as, in this in- stance, the eastern tropical Pacific. My study was undertaken to demonstrate the value of identifying all elements of the fish fauna of tropical regions, rather than restricting interest to scombrid larvae. Much information can be gained for little extra expense (a few percent of the cost of collecting the material at sea) . Of equal consequence, identification of all kinds of fish larvae can be made more critically in- cluding scombrid larvae. METHODS OF MAKING ZOOPLANKTON COLLECTIONS Three nets, differing in size and in coarseness of mesh, were employed to collect zooplankton and micronekton on EASTROPAC cruises. In this paper I am concerned primarily with oblique hauls made with the net of intermediate size and mesh — a net, 1-m mouth diameter, con- structed of 505 /J. nylon (Nitex) cloth, with ap- proximately a 5 to 1 ratio of effective straining surface (pore area) to mouth area. This net was paired in an assembly frame with a finer- 4 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC meshed net when hauled obliquely, but was used alone for taking surface hauls. The finer- meshed net was 0.5 m in diameter at the mouth, constructed of 333 /^ Nitex cloth, with approx- imately an 8 to 1 ratio of effective straining surface to mouth area. The third net, used for collecting micronekton, had a 5-ft square mouth opening and was constructed of mesh measuring approximately 5.5 X 2.5 mm; this net could not be operated from the research vessel Rock- away on EASTROPAC I but was employed from the other three vessels. Usually four zooplankton collections were made at each "biological" station: an oblique collection and a surface collection with the 1-m net, an oblique collection with the 0.5-m net, and an oblique collection with the micronekton net. In taking oblique plankton hauls, the 1-m net was paired in an assembly frame with the 0.5 m net. The assembly of nets was fastened to the towing cable by a bridle about 5 m above a 100-lb weight. The assembly was lowered to depth by paying out 300 m of towing cable at the controlled rate of 50 m of wire per minute. The assembly remained at depth for 0.5 min and then was retrieved at a uniform rate of 20 m per min. Total towing time was about 21.5 min. Towing speed was ca. 2 knots. The depth reached by the net was estimated from the angle of stray (departure from the vertical) of the towing cable. We sought to maintain an angle of stray of 45°, which lowered the assembly to a depth of approximately 210 m. Our con- cern was to sample the upper 200-m stratum. The average depths of hauls taken by the four research vessels are summarized in Table 1. Over 80 % of the hauls made on EASTROPAC I were lowered to depths of 200 m or more, and nearly 95 ''r reached depths of 180 m or greater. However, two hauls were exceptionally shallow (71-90 m) , and nine additional hauls were taken to depths of less than 150 m. Usually four paired net-assembly hauls were taken per day, spaced at about 6-hr intervals. Although the four hauls were planned to be taken at about midnight, dawn, noon, and sunset, the timing of hauls was not coordinated between research vessels. The middle-of-the-night hauls Table 1. — Depth of paired oblique plankton hauls taken by the four research vessels on EASTROPAC I. (Net lowered by paying out 300 m of towing cable) Number of houls token to eoch depth interval from Average depth of houl Argo D avid St Jordan arr Rockaway Alaminot All vessels M 70.1. 80.0 __ 1 80.1- 90.0 _, _. _. 1 90.1-100.0 __ __ .. __ __ 100.1-110.0 _^ 1 110.1-120.0 .. __ __ _. ._ 120.1-130.0 2 __ 3 130.1-140.0 1 __ __ 1 140.1-150.0 1 __ _. 150.1-160.0 __ __ 1 2 3 160.1-170.0 2 __ 2 2 6 170.1-130.0 2 2 2 1 7 180.1-190.0 15 5 4 5 29 190.1-200.0 21 10 11 10 52 200.1-210.0 41 59 58 30 188 210.1-220.0 26 44 57 41 168 220.1-230.0 9 _. 3 5 17 230.1-240.0 -' — 1 — 1 Toral 119 121 139 103 482 were all taken before midnight (2201-2400) on Rockaway, for example, while on Argo most hauls, were made after midnight (be- tween 0001 and 0400 hr). The time of day of occupancy of stations (based on the midtime of each haul) is summarized by hourly intervals in Table 2. At least some hauls were taken during every hour of the day, although fewer than 10 (2-8) were obtained during six of the hourly intervals. Fewest hauls were obtained between 0901 and 1000 hr (2 hauls) and be- tween 2101 and 2200 hr (4 hauls), whereas the largest number of hauls were taken between 2201 and 2300 hr (59 hauls) and between 1001 and 1100 hr (53 hauls). Hauls were made with equal frequency during the four periods of the day on Argo, Jordan, and Rockaway; most plankton hauls were taken near midnight or noon from Alaminos. The numbering system for observations em- ployed on EASTROPAC cruises made use of five digits divided into two groups, as 11.022, 12.002, etc. The outer digit preceding the period is the cruise number common to all vessels participat- ing in a given EASTROPAC cruise; for EAS- TROPAC I, this number is 1. The other digit preceding the period is the identifying number given to each research vessel, with the lowest FISHERY BULLETIN: VOL. 69. NO. I Table 2. — Hour of day that paired oblique plankton hauls were taken from the four research vessels par- ticipating in EASTROPAC I. (Midtime of haul used.) Hours of day Number of hauls token during each hour of the day frorr Argo David Starr Jordan Rockaway Alaminos All vessels 0001-0100 7 10 3 20 01 01 -0200 8 7 2 17 0201-0300 5 2 7 0301-0400 9 7 16 0401-0500 1 1 17 1 20 0501-0600 2 9 10 3 24 0601-0700 7 10 1 1 19 0701-0800 13 10 23 0801-0900 7 7 0901-1000 2 2 1001-1100 1 26 26 53 1101-1200 1 5 5 10 21 1201-1300 7 22 3 1 33 1301-1400 12 3 1 4 20 1401-1500 8 a 1501-1600 1 1 12 1 15 1601-1700 10 3 13 1701-1800 8 6 12 6 32 1801-1900 7 19 1 27 1901-2000 10 1 11 2001-2100 3 3 6 2101-2200 1 3 4 2201-2300 2 2 23 32 59 2301-2400 9 11 5 25 Total 119 121 139 103 482 number given to the offshore vessel. The three digits following the period are numbers given to observations made from each vessel during a cruise, numbered sequentially. Not all "stations" included obliqne plankton hauls; hence there are gaps in numbers applied to plankton collections. The locations of plankton stations occupied by the four research vessels participating in EASTROPAC I are showTi in Figure 1. Sam- ples collected from the Argo are designated as the 11.000 series, samples from the David Stan- Jordan as 12.000 series, Rockaway samples as 13.000 series and Alaminos samples as 14.000 series. In tables to follow, the series of samples taken by each vessel is designated by the above identifying series numbers. The aggregate of stations occupied by each vessel is referred to in text discussions as its pattern. PROCESSING SAMPLES ASHORE As noted above, only samples from 1-m oblique net hauls were sorted routinely for fish eggs and larvae. As a rule the entire sample was sorted; in fact only six collections out of 482 were aliquoted — four collections were split into 50 ^r aliquots, two collections into 2.5 '^r aliquots. The author made all identifications and counts of lan'ae from EASTROPAC I collections. Ac- tual counts of larvae rather than standardized values (see below) are used in tabulation throughout this paper, except one (Table 7). There are several reasons why I chose to do this. As indicated previously, all hauls were made in a roughly comparable fashion. In many studies the investigator is interested in the presence or absence of the larvae of a given species or as- semblage of species as such relate to water masses, community composition, time of day, etc. Such information is most readily obtained from records of actual counts. Some statistical tests require the use of original counts rather than standardized data. For persons interested in deriving standardized counts comparable with those employed for CalCOFI data (Ahlstrom, 1953), standard haul factors for the 482 oblique hauls taken with the 1-m net on EASTROPAC I are given in Appendix Table 7. Two major considerations in the quantitative sampling of fish larvae for resources evaluation are (1) how well has their depth range been covered and (2) how effectively have the larvae been sampled within this layer? We do not have direct answers to either of these questions from EASTROPAC cruises. No studies were made on depth distributions of fish eggs and larvae in the EASTROPAC area. As will appear, fewer fish larvae wei'e obtained during daylight hours than in night hauls; how- ever, we lack information on how completely larvae were sampled in night hauls. DEPTH DISTRIBUTION OF FISH LARVAE Although collecting methods used on EAS- TROPAC did not permit a study of depth distri- bution of fish larvae, such information for the California Current region off California and Baja California and in a less detailed way for the NORPAC Expedition of 1955 are available (Ahlstrom, 1959). In the California Current region, most fish eggs and larvae were distributed within the up- AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC per mixed layer or in the upper portion of the thermocline, between the surface and approxi- mately 125 m. Of the 15 most common kinds of fish larvae taken in vertical distribution ser- ies, 12 were so distributed (ibid., p. 134). Two of the kinds that occurred most commonly below the thermocline were bathylagid smelts, closely related to the two common bathylagid smelts taken on EASTROPAC I. On the NORPAC Expedition of August 1955, two depth strata were sampled at most stations ; a closing net, fastened to the towing cable 200 m below a standard open plankton net, sampled the level between 262 and 131 m on the average, while the upper net sampled from the surface to approximately 131 m deep. Only about one- ninth as many larvae were taken in the closing net hauls as in the upper net hauls; fully half of these were larvae of hatchetfish, family Ster- noptychidae, largely absent from upper net hauls. The two most abundant kinds of fish larvae taken on EASTROPAC I were those of the myctophid lanternfish, Diogenichthys kitem- atics, and of the gonostomatid lightfish, Vinci- guerria spp. In NORPAC collections, only 3 % of the larvae of D. laternatus were taken in the closing net hauls and only 2 % of the Vinciguer- ria larvae. Among the kinds of larvae common to both the NORPAC and EASTROPAC sur- veys that occurred in significant numbers in the deeper NORPAC collections were those of Chaul- iodus (72 % taken in closing net hauls), Proto- myctophum (48 %) and I diacanthus (32 %). Inasmuch as the vertical distribution studies in the California Current region had pointed up the importance of the thermocline in the depth distri- bution of larvae, the pattern of thermocline depth was analyzed for EASTROPAC I (Table 3). Thermocline depth was invariably shallow in the inner pattern occupied by Alaminos (data not included in Table 3) ; the greatest depth recorded was only 40 m, and the majority of observations were at depths shallower than 20 m. Along the six station lines covered in Table 3, thermocline depths were shallowest near the equator, and usually were deepest at the north- ern (20-15° N) and southern (15-20° S) ends of the lines. The thermocline also deepened off- shore; approximately three-fourths of the rec- ords of thermocline depths of 50 m or greater were from the tw^o outer lines, occupied by Argo. Most oblique plankton hauls taken on EAS- TROPAC I sampled to depths of 200 m or more (Table 2), hence sampled considerably deeper than the thermocline in all parts of the EAS- TROPAC area. EFFECTIVENESS OF SAMPLING FISH LARVAE IN DAYLIGHT HAULS AS COMPARED WITH NIGHT HAULS Fewer fish larvae were obtained in hauls made during daylight hours than at night (Table 4). Original (unstandardized) counts of larvae av- eraged 2.76 times as many in night hauls as in day hauls, 285 larvae per occupancy as compared with 103 larvae. Hauls made within 1 hr of sunrise or sunset contained intermediate num- bers of larvae, averaging 217 larvae per oc- cupancy. Table 3. — Summary of records of thermocline depths along six station lines occupied by the research vessels Rockaway, David Starr Jordan, and Argo on EASTROPAC I. Station line along longitude Range in depth of thermocline (m) at latitudes 15-10° N 5° N-0° 0-5" S 5-10° S 10-15° S 15-20° S All latitudes 92° W 0-1 S 7-14 5-29 0-16 15-40 24-45 30-54 0-54 98° 16-30 13-68 23-t4 5-13 2-27 13-32 20-48 40-60 2-68 105* „ 37-50 27-14 0-20 0-28 23-45 24-55 54-66 0^56 112° 8-42 41-79 32-58 0-37 2-22 33-52 .. 0-79 119° 3«hS7 44-90 42-55 0-85 0-65 34-76 50-73 30-71 0-90 126° 52-116 45-79 35-49 0^2 0-60 40-71 43-71 43-70 0-116 % obs. with T. D. shallower than 10. 1 m 17 % 8 % 7 % 46 % 43 % 20 % % obs. w T. D. deep thon 49.9 th m 56 % 46 % 9 % 11 % 9 % 25 % 35 % 63 % 26 % FISHERY BULLETIN: VOL. 69, NO. I 3 O 2 Average number per occupancy IP C O 1-0 Average number per occupancy i-_a III 3 o o> z IZ Average number per occupancy (N) II |a° "5 -C D a Average Total number per larvae occupancy (D) 111 3 o^ Z a i > ) n ■* »o rx ■* (N r*v ro 'O *o r^ ^ ul — Ul 03 D CO 1^ ■^ ro w — lO o ^ CM ^ "O r-^ - (M O^ CO <3 *o o. c^ _ _ -^j- O -O CNI — ^ O C^ — C3 r*. lo -v CM *o *o <> lo -d i< CN — d "S o> r^ rv -o wi — rv. (N CM CM O' 'O CM CO — rs. CO -o rCT^'O'O'O'OiM o o -c -K - "> > >- O « n I" 2 = CM to ; f DO p CO o^ "* n '^ CM -^ O* CO <— CO ^ CM CN -O — CM O^ hv CO ~ o- r-* ^ o CM i^ r^ "^ — CO ^ ■O — -. (O -^ IS. O; CM 00 «0 ■^ ^ CS ^ c^ CO — CM CO -fl- ^N CO O CO -^ CM — <0 CN rs 00 "* ■O O- r*^ CM — CM ■V — <>t in 0 •O lO UO O "^ CO -o CM ■v -(J- — rs ■v-^cjcno — o*-* CO CO CO CM CM CM CO ■O UO to ^s CO ^ CO O o _ lO — lO o CM CM -O rv CM O -O CM — — C3 CO -O CO «0 Co' cm" — CO • — CO "^ o- o- o- o — CO CO 00 lO CO . o «* 4) O ■a o o , S.S s = tt) i to * hv CO O* — CM lO c ^O O CM — CO CO c ^O "O CO ^ — ■^ ' lO *0 "O -e CO O; UO CO CO C> O >0 r^ rs CM rsi c*i CM wi XT) — — — ■— CO CO lO O — CN 'O CO o rs. ro CO o IN. — rs ■>}■ — ^ o lOiOCMt^COCMOCS 3 tT (x Tj- o, CM >0 5 CO CO Ov' " K "i CN CO " — --^ hs! ^ CO ** CO CO CO In. 'O 2 *0 CN O^ CM O^ ^O O O UO O* -^ ■«r "1 -O O O ' ■O ^O lO 00 — "■ >0 "O CM CO -^ CO — d N." 'O d — — 00 CO ■^ CM lo (^ lo -o CM rs — — -o "O o lO CO CO o v CM IN. CO ^ 00 p rs CO io — d —■ ■v d CO MD K O In O* rs — ^ 00 00 "O — o 0> O >0 CO CO &• CO CMCMO^|N.-^COIOCO corstocoooco-o ■^^^COCOCM — -^ lO CM CO CO — — CN "tr "O lo o« o* CO ^ CM >0 *0 -O — "O CO CO "* I o*' rv CM lo o* fN o CO ■v o — o- — o o«. o- -^ 0« "O '^ o- o. _ CM "sr CO p p ■^" CO CM CM — CO CS MO CO CO "O *o o 2 -o' o^ (d -^ ^* d O O 0> — fN N. CO rs. o CO o* o o« "O >0 — CO ^ CO CM 00 00 CO — ~ CO -,7? "O o o ! qSOwcoSwO'" to o - <; O o •; • -&S 1 X S o . U) HI S w) < AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Larvae of some families of fishes were sampled almost as well in day hauls as in night hauls — including Sternoptychidae, Bathylagidae, and Melamphaidae. In contrast, less than one- fourth as many gonostomatid larvae and one- third as many myctophid larvae were taken in day hauls, on the average, as in night hauls. Catches of scombrid larvae were more variable with regard to time of sampling — the night-day ratio in the outer half of the EASTROPAC area was only about 1.5 to 1, whereas the ratio jumped to about 7.5 to 1 in the inner pattern occupied by Alaminos. Larvae collected about in equal amounts in day and night hauls were those known to occur principally below the thermocline. Despite the lower abundance of larvae in day hauls as compared with night hauls, the per- centage of hauls containing larvae of most fam- ilies was only slightly lower (Table 5). The most marked day/night difference in frequency of occurrence was for scombrid larvae, these Table 5. — Percentage of hauls containing larvae of the more abundant fish families on EASTROPAC I, grouped by day, night and dawn or sunset. Family Day hauls Night hauls Dawn or sunset hauls (± 1 hr) All hauls % % % % Myctophidae 97.4 97.8 99.0 97.9 Gonostomctidae 92.7 97.3 95.2 95 Sternoptychidae .70.5 76.1 67.6 69.9 Bathylagidae 61.1 65.2 61.9 62.9 Melamphaidae 60.6 65.2 58-1 61.8 Scombridae 31.1 45.1 40.0 38.4 All others 94.8 99.5 97.1 97.1 Total 97.9 100.0 100.0 99.2 were taken in 45 % of night hauls, but in only 31 '/'c of day hauls. In the discussions that fol- low I make use of all collection data, irrespective of time of collection. NUMBERS OF FISH LARVAE OBTAINED ON EASTROPAC I Fish larvae were obtained in 478 of 482 oblique plankton tows made with the 1-m plank- ton net on EASTROPAC I. The number of larvae per collection ranged from to 2,197, averaging 197 larvae (actual counts). Differences in abundance of larvae with lat- itude are summarized for the four series in Table 6. Fish larvae were obtained in largest num- bers, on the average, in an equatorial band ex- tending from about lat 10° N to 5° S. The least productive waters for fish larvae were in the central water mass of the South Pacific, espe- cially between lat 15° and 20° S. Abundance of fish larvae also decreased off- shore,' averaging only 130 larvae per haul in the outer pattern, occupied by Argo, as com- pared with 246 larvae per haul in the inner pattern, occupied by Alaminos. Tropical waters and oceanic waters are usu- ally considered to be relatively unproductive, compared with temperate coastal regions such as the California Current region (Ryther, 1969). Hence, it is surprising to find that the average number of fish larvae obtained per haul on EASTROPAC I was larger than either on the CalCOFI cruises from the California Current region (Ahlstrom, 1969) or on NORPAC (un- Table 6. — Total catches of fish larvae (actual counts) taken by the four research vessels on EASTROPAC I, summarized by latitude. Argo n.OOO Series David S(flrr Jordan 12.000 Series Ro(kaway 13.000 Series Alaminos 14.000 Series Total EASTROPAC 1 Latitude No. hauls No. larvae No. hauls No. larvae No. hauls No. larvae No. No. hauls larvae No. houls No. larvae Average no. larvae per haul 20° N-15° N 16 1,070 20 4,128 5 462 __ __ 41 5,660 138.0 15° N-10° N 14 1,372 23 3,130 26 5,508 -- -- 63 10,010 158.0 10° N- 5° N 14 2,516 14 3,344 29 10,104 15 5,167 72 21,131 293.5 5° N- 0° 14 4,797 15 4,403 14 4,331 27 11,329 70 24,860 355.1 0° 5° S 14 2,089 18 5,454 14 4,350 17 5,042 63 16,935 268.8 5° S-10° S 13 1,370 15 1,051 14 2,360 16 2,113 58 6,894 118.9 10° 3-15° S 14 1,512 8 863 15 2,337 28 1,673 65 6,385 98.2 15° 3-20° S 20 793 8 513 22 1,928 — - 50 3,234 64.7 Total 119 15,519 121 22,886 139 31,380 103 25,324 482 95,109 197,3 FISHERY BULLETIN: VOL. 69, NO. 1 published data) . Standard haul totals of larvae are used in this comparison (Table 7) not ori- ginal counts. CalCOFI cruises repeatedly sur- veyed a coastal area extending 200 to 300 miles offshore between San Francisco, California, and Magdalena Bay, Baja California. NORPAC was the first comprehensive survey of the North Pacific, made in August-September 1955; the area surveyed by four CalCOFI vessels partici- pating in NORPAC was between lat 20° and 45° N and offshore to long 150° W. Table 7. — Comparison of the average number of fish larvae obtained per haul (standard haul values) EAS- TROPAC I, NORPAC, and CalCOFI cruises. Number hauls Averoge Total depth number of of hauls fish larvae' Average number larvae/haul EASTROPAC 1 1967 482 CO. 200 m 274,131 569 NORPAC 1955 196 CO. 260 m 27,000 "138 CalCOFI cruises 1956 1,407 CO. 140 m 408,140 290 1957 1,493 CO. 140 m 493,550 331 1958 1,852 ca. 140 m 456,020 246 1959 2,182 CO. 140 m 470,450 216 1960 1,826 CO. 140 m 504,980 277 ^ Standard houl totals. 2 Data from two net hauls combined: on overage of 124 larvae per haul were token in upper net hauls (0 to 130 m) and an average of 14 larvae per haul in closing net hauls,, sampling between co. 260 and 130 m. EASTROPAC hauls sampled a somewhat deeper stratum than hauls made on CalCOFI cruises, ca. 200 m as compared to ca. 140 m. As indicated previously, information is available for the majority of NORPAC stations on the rel- ative abundance of fish larvae in the level be- tween ca. 130 and 260 m (closing net hauls) as compai'ed with the level above, to 130 m. Only about one-ninth as many larvae were taken in the deeper hauls. The difference between catches of larvae on EASTROPAC I and NORPAC are particularly marked — four times as many larvae were taken per haul, on the average, on EASTROPAC I as on NORPAC (both nets combined). For com- parison with shallower CalCOFI hauls, I am as- suming that 10 % of the EASTROPAC larvae were obtained in the level between ca. 140 and 200 m. The adjusted value for EASTROPAC larvae, 512 larvae per haul, on the average, is 1.55 times as large as the highest CalCOFI val- ue listed (331 larvae per haul in 1957) and 2.35 times as large as the lowest value (216 larvae per haul in 1959) . The majority of EASTROPAC larvae were those of fishes which never attain a large size as adults — myctophids, gonostomatids, sternopty- chids, etc. — hence numbers of larvae, per se, cannot be considered reliable indices of biomass. The familial composition of larvae was not dis- similar on NORPAC and EASTROPAC, how- ever; hence this comparison of relative abun- dance of larvae is more relevant, as regards biomass, than the comparison with CalCOFI fauna. KINDS OF FISH LARVAE OBTAINED ON EASTROPAC I The kinds of larvae obtained on EASTRO- PAC I are summarized by family and vessel pattern in Table 8, the principal summary table in this paper. Larvae of more than 50 families are listed, but larvae of 10 families contributed 90 9f of the total. The myctophids were the dominant group with 47.2 % of the larvae oc- curring in nearly 98 % of the collections. Gono- stomatid lai-vae were about half as numerous, contributing 23.2 % of the larvae while oc- curring in 95 % of the collections. Hatchetfish larvae (Sternoptychidae) ranked third in abundance with 6 % of the larvae taken in 70 % of the hauls. Bathylagid larvae also exceeded 5 % of the total and occurred in 63 % of the collections. Scombrid larvae ranked fifth and exceeded 2 % of the count, followed by Breg- macerotidae, 1.9 %, Paralepididae, 1.7 %, Idia- canthidae, 1.0 Yc, Nomeidae, 1.0 %, and Mel- amphaidae, 0.9 %. About one-third of the re- maining larvae were too poorly preserved (dis- integrated) to identity. On the basis of larval abundance, the domi- nant orders of fishes in oceanic waters are the Myctophiformes and Salmoniformes, making up between 85 and 88 'li ; the latter value assumes a proportionate representation of larvae of these groups in the "disintegrated" category, i.e., larvae too damaged or disintegrated to identify with certainty. Despite the dominance of fishes of the above two orders, a number of other groups of fishes are represented in the oceanic pelagic fish fauna. The berycoid fishes are rep- 10 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC i < OJ M ^ 1 ri U e > 01 1 ' •a = « ■SSs ^ 1 3 M C 41 CO *" ' z i 3 3 5) J) 5 5 >. E D u COOOOCO^OO — "COO"^ — ^cow — — CN eqo-o — O^'O O^-O CO — CO CO — CIO CN CMcocTO — ooooo* — O — dC9CNeoN.cn — o-"^rvO« — 1 — eo ■V — to-^ -ow — — sS*o c*i Ovooco"^ •— — — Mi O. — C4 — COCN^O — ^ — iifOlOr) — OO'OO— NO'CM-* — coo O N"*OCO -O >0 CO ■OOO'OCN rv VCN fcO'O'ffrO-* lOCOCN*OC*)- - coV CN — lOOOUlO — O — OCN"0 CO — N OJCN — CN COCM CO f^ O CO— CNVl — CO -^ jiOO'^CO- ■^O'V- -COCNCtTj-O-OCNO-OO -M'^OCMCN'^'O'OkO- O^cO'O'^COCNOCN- O'OOO'O^COCNOO^OOOCNOOCO'OIV^O-O — O-OCOiOOOOO^^-iOrON. loo-co- NO'to rvio o . cm -o — cn'^ .© — — cnco— ■* — — — iocnco ■^fs^rv CO— cMuo — — CO n co co tta3"*00'000>ONOO — coKcoOcN — o— '^rooOOOco'O^'Orv OJ uo CO^OO oocM'^rcoco-orNNrsOOcocNO'^c — CO-OCN CO"*!-^ O'^CNO CN-OO ~ OCN -O-OCOOOOOCO — oo -00100000CON>0 -vn— CNiO -oo— oo^ "S" "^■^ — — - CNCMCMeNeNCNCNCSCNO4C0C0C0nC0C0COC0C0CT^"0>OioiOiO«0 11 FISHERY BULLETIN: VOL. 69, NO. I resented by Melamphaidae, a family of fishes that is almost as ubiquitous as the myctophids or gonostomatids. Fishes of the gadoid family, Bregmacerotidae, also are widely distributed in the warmer waters of all oceans. Among the ubiquitous epipelagics are the flyingfishes, Ex- ocoetidae. Only a moderate number of perciform fishes are widely distributed in offshore, oceanic wa- ters. Among the more important are fishes of the families Scombridae, Gempylidae, Trichiur- idae, Istiophoridae, Coryphaenidae, Bramidae, Nomeidae, Apogonidae, Chiasmodontidae, and Tetragonuridae. Larvae of some demersal fishes have a much wider offshore distribution than one would asso- ciate with the known distribution of adults. In- cluded in this group are larvae of bothid and cynoglossid flatfishes, and larvae of Scorpaeni- dae, Gobiidae, and Labridae. Another widely distributed gi-oup in oceanic waters are the bizarre ceratioid fishes. The rotund larvae of these fishes were taken in about 30 % of the EASTROPAC collections, always in small numbers. The basic data on the kinds and numbers of fish larvae obtained in the 482 EASTROPAC I collections are contained in six appendix tables, whose contents are summarized below, and keyed to Table 8 and to other tables in this report. Appendix Table 1. — Counts of fish larvae, tabulated by family, for all stations occupied on EASTROPAC I. This table contains 22 categories, mostly families, but for complete- ness, a category is included for "other identi- fied larvae," one for "unidentified larvae" and one for "disintegrated larvae" (i.e., larvae too damaged or disintegrated to identify with any certainty) . Appendix Table 2. — Myctophid larvae, tab- ulated by genus or species, for all stations oc- cupied on EASTROPAC I. Myctophid larvae are tabulated by species for 12 kinds, and by genus for 8 kinds. Also included are cate- gories for unidentified myctophids, and total myctophids. A summary of this appendix table is contained in Table 15. Appendix Table 3. — Counts of selected ca- tegories of fish larvae by station. Table con- tains 23 categories including 10 species, 10 genera, 2 families, and 1 suborder; 9 of these were included in the category "other identi- fied larvae" in Appendix Table 1. Appendix Table 4. — Summary of occur- rences and numbers of larvae of eight families limited in distribution to a broad coastal band or around offshore islands. Only positive stations are included. These eight families also were included in the category " other identified larvae" in Appendix Table 1. Appendix Table 5. — Numbers and kinds of larvae of Gempylidae-Trichiuridae obtained in EASTROPAC I collections. Only positive stations are included. A summary of this ap- pendix table is given in Table 19. Appendix Table 6. — Numbers and kinds of flatfish (Pleuronectiformes) larvae obtained in EASTROPAC I collections. Only positive hauls are included. A summary of this ap- pendix table is given in Table 22. Appendix Table 7.— Standardized haul factors for the 482 oblique 1-m net hauls taken on EASTROPAC I. These factors adjust ori- ginal counts of larvae to the comparable stan- dard of numbers of larvae in 10 m3 of water strained per meter of depth fished. I will not attempt to comment on all 58 cate- gories (family or larger grouping) summarized in Table 8, but will limit my discussion to 31 of these. In order to tie the text discussion closely to this table, I i-etain the numbers for categories as given in Table 8; those discussed in the text ai-e preceded by an asterisk in this table. COMMENTS ON LARVAE OF THE MAJOR FISH FAMILIES COLLECTED ON EASTROPAC I 1. CLUPEIDAE ( 10 occurrences, 81 larvae) Three species of clupeid larvae were taken in EASTROPAC I collections — Opisthonema sp. 12 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC (5 occurrences, 12 larvae), Etrumeus acumina- tus Gilbert (2 occurrences, 6 larvae), and Sar- dinops sagax (Jenyns) (3 occurrences, 63 larvae). The latter two species were collected in the vicinity of the Galapagos Islands. 2. ENGRAULIDAE (10 occurrences, 205 larvae) The majority of the engraulids (5 occurrences, 174 specimens) were those of the Peruvian an- chovy, Engraulis ringens Jenyns, collected at coastal stations between lat 6° and 13.5° S. Al- though larvae from only a few surface hauls have been sorted as yet, one haul was outstand- ing: the surface tow taken at station 14.069 contained 10,466 larvae and transforming speci- mens of Peruvian anchovy, E. ringens. Speci- mens ranged in size from 3.5 to 37.5 mm ; most were between 4.0 and 7.5 mm in length but even transforming specimens, 20.0 to 37.5 mm long, were rather common (83 individuals). In the oblique 1-m haul at this station, 97 anchovy larvae were obtained. 3. ARGENTINIDAE (43 occurrences, 87 larvae) Three kinds of argentinid larvae were ob- tained: Argentina sp. (1 specimen), Nansenia sp. A (84 lai-vae), and Nansetiia sp. B. (2 larvae) . The specific identities of the two kinds of Nansenia larvae are still uncertain. On EASTROPAC I, Nansenia sp. A was taken most commonly in an equatorial band between lat 5° N and 5° S (Fig. 2). Larvae of Nansenia sp. A also occur in the southern portion of the area surveyed on cruises of CalCOFI, particularly to the south of Point San Eugenio, Baja California. A Nansenia larva with markedly different pig- mentation pattern was obtained at station 11.154 in the central water mass of the South Pacific. A similarly pigmented Nanseyiia larva was ob- tained on NORPAC from the central water mass of the North Pacific. 4. BATHYLAGIDAE ( 304 occurrences, 4,880 larvae) Although two kinds of Bathylagus larvae were obtained, one species was taken in only two con- tiguous southern stations, 12.142 and 12.144. The eyes of the latter were carried on short stalks. The distribution of larvae of the com- monly occurring species, B. nigrigenys Parr (296 occurrences, 2,987 larvae), was almost identical with that of the myctophid, Diogenich- thys laternatus (Garman) (Fig. 3). The larvae of neither species occurred in the central South Pacific water mass; on the four outer lines, sur- veyed by Argo and Jordan, the occurrences of B. nigrigenys larvae ended at about lat 5° S. In the portion of the EASTROPAC area in which larvae of this species were distributed, they occurred in three-fourths of the stations occupied. In the innermost pattern occupied by Alami- nos, larvae of Leuroglossus stilbius urotranus (Bussing, 1965) were common (37 occurrences, 1,890 larvae). All but four specimens were obtained between lat 10° N and 10° S, and most within 300 miles of the coast (Fig. 2). 5. GONOSTOMATIDAE (459 occurrences, 22,046 larvae) Areal occurrence and relative abundance of gonostomatid larvae on EASTROPAC I are summarized in Table 9. They were obtained in 95 % of the hauls and made up approximately 23.2 % of the larvae. As noted earlier, gonostomatid larvae were markedly more abundant in night hauls than in day hauls: 4.35 times as many, on the aver- age. In contrast, larvae of the closely related hatchetfishes, Sternoptychidae, were taken in only slightly larger numbers at night (1.24 times as many as in day hauls). In the section dealing with depth distribution of fish larvae it was pointed out that the gonostomatid, Vinci- guerria spp. occurred no deeper than ca. 130 m in NORPAC collections, whereas sternoptychid larvae were inhabitants of the aphotic zone be- low 130 m. An interesting exception should be noted: gonostomatid larvae of the subfamily Maurolicinae had depth distributions similar to sternoptychid larvae on NORPAC. Larvae of two Maurolicinae, Mauroliciis and Araiophos, genera were taken on EASTROPAC. Although the depth distribution of these genera has not 13 FISHERY BULLETIN: VOL. 69, NO. I 90° 80" Figure 2. — Distribution of larvae of the argentinid, Nansenia spp., and of the bathylagid, Letiroglossiis stilbius urotranus (Bussing) on KASTROPAC I. Records of occurrence of A'awscnto larvae are shown as open circles with dot in center, while those of Leuroglossus larvae are open squares with dot (1 to 100 larvae) or closed squares (101 to 490 larvae). Small solid circles represent other stations occupied on EASTROPAC I. Table 9. — Areal occurrence and relative abundance of lari'ae of Gonostomatidae on EASTROPAC I. Argo David Starr Jordan Rod away jilaminoj Total 11.000 series 12.000 series 13.00C series 14.000 series EASTROPAC 1 Lalilude No. No. No. No. No. No. No. No. No. No. Average no. pOSitiVQ positivo positive positive positive larvae per positive haul hauls larvae hauls larvae hauls larvae hauls larvae hauls larvae 20° H\S° N 14 418 20 1,534 5 115 .. 41 2,067 50.4 15° N-10° N 14 380 22 745 24 607 __ 60 1,732 28.9 10° N- 5° N 13 185 13 242 27 2.085 14 417 67 2,929 43.7 5° N- 0° 14 2,112 IS 637 14 1,825 27 1,882 70 6,456 92.2 0° - 5° S 14 409 18 912 14 1,577 16 1,036 62 3,934 635 5° S-I0° S 13 202 14 161 14 799 10 647 51 1,809 35.5 )0° S -IS- S 14 635 8 368 IS 524 21 490 58 2,017 34.8 IS" S-20° S 20 322 8 183 22 597 — — SO 1.102 22.0 Totol lis 4,663 118 4,782 135 8,129 88 4,472 459 22,046 48.0 14 AHLSTROM : FISH LARVAE IN EASTERN TROPICAL PACIFIC 130* 120° 110° 100° 90° 80° Figure 3. — Distribution of larvae of Bathylagus nigrigenys Parr on EASTROPAC I. Two orders of abundance are shown: open circles with dot in center represent counts of 1 to 25 larvae, large solid circles represent counts of 26 or more larvae. Small solid circles represent negative hauls. been determined, they were sampled more fully during daylight hours than other gonostomatids; the night/day ratio for Maurolmis and Arai- ophos larvae was ca. 1.6 and 2.0 respectively. Larvae belonging to six gonostomatid genera were common to abundant (Table 10) and larvae of several additional genera were taken occasionally. Larvae of two genera were of outstanding importance in the EASTROPAC area — Vinciguerria and Cyclothone. Vinciguer- ria occurred in 87.5 % of the collections, Cyclo- thone in 62.4 %. Charts showing the distribution and relative abundance of larvae of Gonostomatidae and Sternoptychidae (combined) on EASTROPAC I will be included in the EASTROPAC Atlas. Araiophos eastropas Ahlstrom and Moser ( 18 occurrences, 529 larvae) Larvae of A raiophos eastropas were obtained only on the outermost pattern to the south of lat 10° S (Fig. 4). Within this limited area it was the most common gonostomatid. The spe- cies taken on EASTROPAC represented an un- described species in a genus that previously 15 FISHERY BULLETIN: VOL. 69. NO. 1 Table 10. — Frequency of occurrence and relative abundance of the kinds of gonostomatid larvae on EASTROPAC I. Argo DavU St arr Jordan Rork away AlaminoJ Total 11.000 series 12.000 series 13.00C series I4.00C series EASTROPAC 1 Gonostomatid larvae No. No. No. No. No. No. No. No. No. No. positive positive positive positive positive hauls larvae hauls larvae houls larvae hauls larvae hauls larvae liraiaphos eastropaj 18 529 18 529 Cydothone spp. 94 697 71 582 89 735 47 167 301 2,181 Diplopkos taenia IS 51 40 107 14 24 1 I 73 183 Ichthyococcu! spp. 7 9 11 16 18 31 5 5 41 61 Maurolicui muelleri 11 43 19 143 13 78 43 264 VincigutTria spp. 96 3,339 109 4,011 131 7,179 86 4,211 422 18,740 Other gonostomotids 13 38 9 23 12 17 8 10 42 88 Total IIS 4,663 118 4,782 135 8,129 88 4,472 459 22,046 FiGUKE 4. — Distribution of larvae of three species of Gonostomatidae on EASTROPAC I. Records of occurrence of larvae of Araiophos eastropas Ahlstrom and Moser are shown as triangles, Diplophos taenia (Giinther) as large open circles, and Maurolicus muelleri (Gmelin) as squares. Solid triangles and squares are for counts of 26 or more larvae. Small solid circles represent negative hauls. 16 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC was known from a single collection made off Hawaii (Grey, 1961). Adults and larvae were described by Ahlstrom and Moser (1969). Cyclothone spp. (301 occurrences, 2,181 larvae) Larvae of Cyclothone spp. were taken least frequently in the northern quarter of the EAS- TROPAC pattern (betweeen lat 10° and 20° N, and in the inner pattern occupied by Alaminos (Table 11 and Fig. 5). In the former area, less than 20 Sf of the hauls (20 of 103) con- tained Cyclothone larvae; in the inshore pat- tern only about 45 % of the hauls (47 of 103) contained Cyclothone larvae. Over the remain- der of the EASTROPAC I pattern Cyclothone larvae occurred at most stations (234 of 276). The lowest number of larvae per positive haul, 2.15 larvae, was obtained in the northern sec- tion; the next lowest, 3.55 larvae per positive haul, in the Alaminos pattern. Over the re- mainder of the pattern, 8.42 larvae were ob- tained per positive haul. No attempt was made to identify the larvae of Cyclothone to species, and our hauls did not extend deep enough to collect adults. Diplophos taenia Giinther (73 occurrences, 183 larvae ) A study was made of larval and adult speci- mens of Diplophos in an attempt to determine whether the Pacific specimens should be as- signed to D. taenia or retained as a distinct species, D. pacificus Giinther. Grey (1960) had placed Pacific specimens in D. taenia but later she (Grey, 1964, p. 89) developed reservations because of the consistently lower photophore count of the ventral series in Pacific specimens. Without detailing my observations on Diplophos, which I plan to publish separately, I have con- cluded that our eastern Pacific Diplophos is not separable from the Atlantic D. taenia. Larvae of Diplophos were taken most com- monly to the north of lat 10° N — 36 occurrences, 105 larvae (Fig. 4). The remaining 37 occur- rences, 78 larvae were distributed throughout the EASTROPAC I pattern. Ichthyococcus spp. (41 occurrences, 61 larvae) Two kinds of Ichthyococcus larvae were taken on EASTROPAC L The specific identity of the more common form has been determined as /. irregularis Rechnitzer and Bohlke; the other form has yet to be identified to species. Maurolicus muelleri (Gmelin) (43 occurrences, 264 larvae ) Larvae of this species were taken only on an equatorial band between lat 5° N and 5° S and were not taken in the outer pattern occupied by Argo (Fig. 4). This distribution, without additional information, could be misleading. Maurolicus is known to have a wide latitudinal distribution in the South Pacific. For example, Maurolicus larvae were obtained at lat 33° S on MARCHILE VL the portion of EASTRO- PAC II occupied by the Chilean vessel Yelcho. We also have collections from south of New Zealand, obtained on an Eltanin cruise. The species may be carried northward oflF South America in the Humboldt Current and then off- shore in the equatorial current system. Table 11.— Area occurrence and relative abundance of larvae of Cyclothone spp. on EASTROPAC I. Argo 1 1 .000 series David Starr Jordan 12.000 series Rockaway 13.000 series Alaminos 14.000 series Total EASTROPAC 1 Latitude No. positive hauls No. larvae No. positive hauls No. larvae No. positive hauls No. larvae No. positive hauls No. larvae No. positive hauls No. larvae Average no. larvae per positive haul 20° N-10° N 12 31 4 8 4 4 20 43 2.2 10° N- 0° 24 136 25 137 33 235 23 69 105 577 5.5 0° -10° S 24 179 29 246 20 117 13 43 86 585 6.8 10° S-20° S 34 351 13 191 32 379 11 55 90 976 10.8 Total 94 697 71 582 89 735 47 167 301 2,181 7.2 17 130° T — \ — I — I — r -| — I — I — I — I — I — I — I — r 100" -I — I — \ — TTT — I — I — I — I — I — r— T — I— T — I — I — I — 1—1 — I — I — I — I — I — I I I — r FISHERY BULLETIN: VOL. 69, NO. 1 90° 80° 20' 10' 10" ® e @ © © VM4NZANILL0 20" s Q®®® ® 1^ A 3® © 0001 I L_ I I I J 1—1—1 I I I I I I 130° 120" no* 100* 90* 80" Figure 5. — Distribution of larvae of the gonostomatid Cyclothone spp. on EASTROPAC I. Collections of 1 to 25 larvae are shown as circles with dot in center, collections of 26 or more larvae as large solid circles; neg- ative hauls are shown as small solid circles. Vinciguerria spp. (422 occurrences, 18,740 larvae ) Larvae of Vinciguerria occurred in more hauls than those of any other genus and ranked sec- ond in abundance to the myctophid genus Dio- genichthys. The distribution of Vinciguerria larvae is shown in Figure 6. Although most of the material unquestionably is V. bicetia (Garman) , some of the collections from offshore and particularly from the central South Pacific water mass between lat 5° and 20° S represent V. nimbaria (Jordan and Williams) . The larvae of V. nimbaria are indistinguishable from those of V. lucetia (Ahlstrom and Counts, 1958), hence identification must be made on meta- morphosing specimens, juveniles, and adults. The two species are closely allied, but readily separable from V. poweriae (Cocco) and V. attenuata (Cocco), the other two species of Vinciguerria, at all stages of development. A trenchant difference between the two "pairs" of species is the development of a pair of sym- physeal photophores under the lower jaw in V. lucetia and V. nimbaria and the absence of this pair in V. poweriae and V. attenuata. The two characters most readily used for distinguishing 18 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC 130' 120° MO" Figure 6. — Distribution of larvae of the gonostomatid, Vindguerria spp. on EASTROPAC I. Collections of 1 to 100 larvae are shown as circles with dot in center, collections of 101 or more larvae as large solid circles; negative hauls are shown as small solid circles. between V. lucetia and V. nimbaria are (1) number of gill rakers and (2) number of IV (and OV) photophores. Material of V. nim- baria studied from the eastern North Pacific (ibid.) had 5 to 6 +15 gill rakers and 23 to 24 IV photophores (13 to 14 OV photophores) whereas V. lucetia had 8 to 10 + 18 to 23 gill rakers and 20 to 23 IV photophores (10 to 13 OV photophores) . In the EASTROPAC area, V. lucetia maintained the high gill raker counts, but usually had 21 IV (11 OV) photophores. The offshore form referred to V. nimbaria usu- ally had 22 IV (12 OV) photophores (1 less per group than in V. nimbaria from the temper- ate North Pacific) and 6 to 7 + 15 to 16 gill rakers (a slightly higher count). In most areas the adults of the two species of Vindguerria did not co-occur, hence the larvae can be assigned with some assurance to one or the other. For example, all collections made between lat 5° and 20° S from Argo and Jordan patterns were exclusively V. nimbaria. On these patterns the plankton hauls were sup- plemented by micronekton net hauls, and the latter contained material of Vindguerria ju- veniles and adults from most stations occupied 19 FISHERY BULLETIN: VOL. 69. NO. I at night. Unfortunately, the micronekton net was not used on Rockaway (12.000 series), and insufficient numbers of older stages (metamor- phosing specimens and juveniles) were taken in plankton hauls to permit a meaningful separa- tion of the two species in waters to the south of lat 5° S in this series. Vinciguerria poweriae (Cocco) co-occurred with V. nimbaria in the central water mass of the North Pacific (Ahlstrom and Counts, 1958), but no material of V. poweriae was obtained in EASTROPAC collections. However, material of V. attenuata (Cocco) was obtained from farther south in the eastern Pacific on the "Downwind Expedition" — hence all four spe- cies of Vinciguerria do occur in the eastern Pacific. Other gonostomatids (42 occurrences, 88 larvae) Included in this category are larvae of two identified genera, Gonostoma and Woodsia, and several kinds of larvae that are unmistakably gonostomatid, but not identified as to kind. 6. STERNOPTYCHIDAE (337 occurrences, 5,687 larvae) Hatchetfish larvae ranked third in abundance (5.98 /f of total), exceeded by larvae of Mycto- phidae and Gonostomatidae. The majority of hatchetfish larvae were those of Sternoptyx di- aphana Hermann, and most of the remainder of Argyropelecus lychmis Carman. Because larvae of Sternoptychidae are more fragile than most other kinds and are usually in poor condition, no attempt was made to identify them to genus or species. Areal occurrence and relative abun- dance of sternoptychid larvae on EASTROPAC I are summarized in Table 12. Larvae were not only taken in markedly more collections between lat 10° N and 10° S— 94 9^ of the collections were positive as compared with only 41 % in the remainder of the pattern — but more larvae were taken per positive haul — 21.1 larvae as compared with 5.2. 7. ASTRONESTHIDAE (12 occurrences, 13 larvae) Several kinds of astronesthid larvae were collected in the EASTROPAC area: only one kind had heavy pigmentation on the body; the others were lightly, but characteristically pig- mented. Larvae of Astronesthidae are similar in appearance to other stomiatoid larvae; they have a slender, elongated body, and a long in- testine that underlies the body for about Yiq or more of the standard length, and usually has a free terminal, trailing portion that can be quite long, often trailing beyond the caudal fin. As- tronesthid larvae can be distinguished readily from other stomiatoid larvae by the forward po- sition of the dorsal fin in relation to the anal fin. Developmental series of astronesthid larvae have not been described in literature. Eleven of the 12 occurrences of astronesthid larvae were taken within 10° ± of the equator. 8. CHAULIODONTIDAE (80 occurrences, 165 larvae j Larvae of Chaidiodus are readily identifiable to genus, but are difficult to separate at the spe- Table 12. — Areal occurrence and relative abundance of larvae of Sternoptychidae on EASTROPAC I. Areo 1 1 .000 series David St 12.000 arr Jordan series Ro." Syacium has a distinctive larva with heavy opercular spination, a sphenotic spine on either side of 41 FISHERY BULLETIN: VOL. 69, NO. I the head, and 5 to 8 elongated anterior dorsal rays. Larvae of the closely related genus, Cy- clopsetta, also develop opercular and head spina- tion. The opercular spination Is more pro- nounced in Syachim — particularly an antlerlike spine that develops on the posterior border of the preoperculum. The three anterior rays of the left pelvic fin become only moderately elon- gated in Syacium larvae; the rays are of about equal length, firmly joined together by a mem- brane, and pigmented distally. The full com- plement of dorsal and anal fin rays usually are laid down before the larvae attain a standard length of 10 mm; the largest specimens studied, ca. 20 mm long, were undergoing metamor- phosis. Citharichthys-Etropus (26 occurrences, 50 larvae) Before discussing problems in identification of Citharichthys-Etropus larvae from the EAS- TROPAC area, some background information will be given on Citharichthys larvae in the Cal- COFI region. Illustrations of larvae of three spe- cies of Citharichthys were given in Ahlstrom (1965). Two species, Citharichthys sordidus (Girard) and C. xanthostigma Gilbert, develop 2 elongated dorsal rays and also 2 elongated vent- ral rays on larvae larger than about 5 mm ; the other species never develops such rays. Another species that occurs off central and southern Baja California, C. fragilis Gilbert, also develops 2 elongated rays on the dorsal and ventral fins. Two species of Citharichthys, C. gilberti Jenkins and Evermann, and C. platophrys Gil- bert, and the widely distributed Etropus cros- sotus Jordan and Gilbert are known to occur in the EASTROPAC area. Three kinds of larvae were taken in EASTROPAC collections refer- able to Citharichthys or Etropus. The most common kind developed 3 elongated dorsal rays, a less common form developed 2 elongated dorsal rays, and some specimens lacked elongated rays. The form with 3 elongated dorsal rays is almost certainly referable to Citharichthys. Larvae of a common Atlantic species, C. arctifrons Goode, develop 3 elongated dorsal rays, confirming the presence of this combination in Citharichthys larvae. A cleared and stained specimen from station 13.040 with 3 elongated dorsal rays pos- sessed 10 + 25 vertebrae, 78 dorsal rays, and 59 anal rays. The meristics of the dorsal and anal fins could fit either C. platophrys or C. gil- berti. Yet so little is known of C. platophrys that I would hesitate to refer the common Citharichthys larvae in EASTROPAC material to this species. A similar problem attends larvae of the form that lacks elongated dorsal rays. Two specimens, 11.5 and 12.0 mm, from station 14.014 each had 88 dorsal and 67 anal rays; vertebrae counts were 10 + 23 and 10 + 24. These counts best fit E. crossotus, except that the vertebral counts are low. No material of the form with 2 dorsal rays (undoubtedly a Citharichthys) has been cleared and stained for precise meristics. A definite identification has yet to be made on all three kinds of larvae. 55. CYNOGLOSSIDAE (63 occurrences, 304 larvae) Only one cynoglossid genus, Symphurus, oc- curs in the eastern Pacific. Five or more kinds of Symphurus larvae were obtained in EAS- TROPAC collections; these were obtained in more collections than larvae of bothid flatfishes (63 as compared with 56) , and made up a larger percentage of the total flatfish larvae (ca. 60 '^,'r ) . A moderate number of recently transformed specimens of Symphurus were obtained in EASTROPAC collections; in contrast, all spe- cimens of bothid flatfish were pretransformation larvae. The distribution of Symphurus larvae in EASTROPAC I is shown in Figure 13. ACKNOWLEDGMENTS I am indebted to a number of persons for as- sistance during the preparation of this manu- script. Kenneth Raymond prepared the distri- bution charts. Amelia Gomes helped in many facets of the work including the preparation of cleared and stained specimens of flatfishes and other groups. H. Geoff"rey Moser has worked closely in studies of larvae of Myctophidae and Gonostomatidae. W. L. Klawe has been help- 42 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC ful in many ways; he graciously has permitted me to include station information on occurrence and numbers of larvae of Auxis sp. and skip- jack tuna. I wish particularly to thank David Kramer and H. Geoffrey Moser for reviewing the manuscript. LITERATURE CITED AHLSTROM, Elbert H. 1953. Pilchard eggs and larvae and other fish larvae, Pacific Coast - 1951. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 102. 55 p. 1959. Vertical distribution of pelagic fish eggs and larvae off California and Baja California. U.S. Fish Wildl. Serv., Fish. Bull. 60: 107-146. 1965. Kinds and abundance of fishes in the Cal- ifornia Current region based on egg and larval surveys. Calif. Coop. Oceanic Fish. Invest. Rep. 10: 31-52. 1969. Mesopelagic and bathypelagic fishes in the California Current region. Calif. Coop. Oceanic Fish. Invest. Rep. 13: 39^4. AHLSTROM, Elbert H., and Robert C. Counts. 1958. Development and distribution of Vinciguerria lucetia and related species in the eastern Pacific. U.S. Fish Wildl. Serv., Fish. Bull. 58: 363-416. AHLSTROM, Elbert H., and H. Geoffrey Moser. 1969. A new gonostomatid fish from the tropical eastern Pacific. Copeia 1969(3): 493-500. Alverson, Franklin G. 1961. Daylight surface occurrence of myctophid fishes off the coast of Central America. Pac. Sci. 15(3): 483. Beebe, William, and Mary Vander Pyl. 1944. Eastern Pacific expeditions of the New York Zoological Society. XXXIII. Pacific Myctophi- dae. (Fishes.) "Zoologica (New York) 29(2): 59-95. Berry, Frederick H., and Herbert C. Perkins. 1966. Survey of pelagic fishes of the California Current area. U.S. Fish Wildl. Serv., Fish. Bull. 65(3) : 625-682. Bruun, Anton Fr. 1937a. Monolene danae, a new flatfish from Pan- ama, caught bathypelagically. Ann. Mag. Natur. Hist, 10th Ser. 19(110): 311-312. 1937b. Chascanopsetta in the Atlantic; a bathy- pelagic occurrence of a flatfish, with remarks on distribution and development of certain other forms. Vidensk. Medd. Dansk Naturhist. Foren. 101: 125-136. Bussing, William A. 1965. Studies of the midwater fishes of the Peru- Chile Trench. In George A. Llano (editor). Bi- ology of the Antarctica Seas II, p. 185-227. Ant- arctic Res. Ser. 6. Nat. Acad. Sci. Nat. Res. Counc. Publ. 1297. d'Ancona, Umberto, and Geminiano Cavinato 1965. The fishes of the family Bregmacerotidae. Dana Rep. Carlsberg Found. 64, 92 p. Ebeling, Alfred W. 1962. Melamphaidae I. Systematics and zoogeogra- phy of the species in the bathypelagic fish genus Melamphaes Glinther. Dana Rep. Carlsberg Found. 58, 164 p. Ebeling, Alfred W., and Walter H. Weed III. 1963. Melamphaidae III. Systematics and distri- bution of the species in the bathypelagic fish genus Scopelogadus Vaillant. Dana Rep. Carls- berg Found. 60, 58 p. Ege, Vilh. 1953. Paralepididae I {Paralepis and Lestidium) . Dana Rep. Carlsberg Found. 40, 184 p. Fraser-Brunner, a. 1949. A classification of the fishes of the family Myctophidae. Proc. Zool. Soc. London 118(4) : 1019-1106. Garman, S. 1899. Reports on an exploration off the west coasts of Mexico, Central and South America, and off the Galapagos Islands, in charge of Alexander Agassiz, by the U.S. Fish Commission steamer "Albatross," during 1891, Lieut. Commander Z. L. Tanner, U. S. N., commanding. XXVI. The fishes. Mem. Mus. Comp. Zool Harvard Coll. 24, 431 p. Gibbs, Robert H., Jr. 1964. Family Idiacanthidae. In Fishes of the western North Atlantic, p. 512-522. Mem. Sears Found. Mar. Res. 1, Part 4. 1969. Taxonomy, sexual dimorphism, vertical dis- tribution, and evolutionary zoogeography of the bathypelagic fish genus Stomias (Stomiatidae). Smithsonian Contrib. Zool. 31, 25 p. Grey, Marion. 1955. The fishes of the genus Tetragonurus Risso. Dana Rep. Carlsberg Found. 41, 75 p. 1960. A preliminary review of the family Gonos- tomatidae, with a key to the genera and the de- scription of a new species from the tropical Pa- cific. Bull. Mus. Comp. Zool. Harvard Coll. 122(2) : 55-125. 1961. Fishes killed by the 1950 eruption of Mauna Loa, Part V, Gonostomatidae. Pac. Sci. 15 (3) : 462-476. 1964. Family Gonostomatidae. In Fishes of the western North Atlantic, p. 78-240. Mem. Sears Found. Mar. Res. 1, Part 4. KuME, SusuMU, and Milner B. Schaefer. 1966. Studies on the Japanese long-line fishery for tuna and marlin in the eastern tropical Pa- cific Ocean during 1963. Inter-Amer. Trop. Tuna Comm. Bull. 11(3): 101-170. 43 FISHERY BULLETIN: VOL. 69. NO. 1 Kyle, H. M. 1913. Flat-fishes (Heterosomata). Rep. Dan. Oceanogr. Exped. 1908-10 Mediter. Adjacent Seas 2(A.l), 150 p. MosEH, H. Geoffrey, and Elbert H. Ahlstrom. 1970. Development of lanternfishes (family Myc- tophidae) in the California Current. Part I. Spe- cies with narrow-eyed larvae. Bull. Los Angeles County Mus. Natur. Hist, Sci. 7, 145 p. Nafpaktitis, Basil G., and Mary Nafpaktitis. 1969. Lanternfishes (family Myctophidae) col- lected during cruises 3 and 6 of the R/V Anton Bruun in the Indian Ocean. Bull. Los Angeles County Mus. Natur. Hist., Sci. 5, 79 p. Norman, J. R. 1934. A systematic monograph of the flatfishes (Heterosomata). Vol. 1, Psettodidae, Bothidae, Pleuronectidae. British Museum (Natural His- tory), London, viii + 459 p. Perkins, Herbert C. 1963. Redescription and second known record of the bothid fish, Monolene asaedai Clark. Copeia 1963(2) : 292-295. Pertseva-Ostroumova, T. A. 1964. Come morphological characteristics of mycto- phid larvae (Myctophidae, Pisces). [In Russian]. (Transl., 1966, In T. S. Rass (editor). Fishes of the Pacific and Indian Oceans, biology and distri- bution, p. 79-97. (Available Clearinghouse for Federal Scientific and Technical Information, Springfield, Va., as 65-50120.) Rofen, Robert R. 1963. Diagnoses of new genera and species of alepisauroid fishes of the family Paralepididae. Aquatica 2, 7 p. Ryther, John H. 1969. Photosynthesis and fish production in the sea. Science 166(3901): 72-76. Strasburg, Donald W. 1964. Postlarval scombroid fishes of the genera Acanthocybium, Nealotus, and Diplospinus from the central Pacific Ocean. Pac. Sci. 18(2) : 174- 185. Taning, a. Vedel. 1918. Mediterranean Scopelidae (Saurus, Aulopus, Chlorophthalmus and Myctophiim) . Rep. Dan. Oceanogr. Exped. 1908-10. Mediter. Adjacent Seas 2(A.7), 154 p. Voss, Nancy A. 1954. The postlarval development of the fishes of the family Gempylidae from the Florida Current. I. Nesiarchiis Johnson and Gempylus Cuv. and Val. Bull. Mar. Sci. Gulf Carib. 4(2) : 120-159. 44 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 1. — Counts of fish larvae, tabulated by family, for all stations occupied on EASTROPAC I. s § V3 % E o CD s o o u 1 s CO i n a> c o u < H c o 1 1 o s c o 2 'o i 3 w u O a; '2 % o s 0} ■5 a 2 u > a E ca u 1 s E ■a .060 5 26 59 4 1 18 2 3 2 120 .062 7 8 1 44 5 1 1 8 5 3 83 .064 15 71 6 2 274 21 1 2 1 1 5 7 406 .065 2 72 6 4 31 6 1 1 4 1 128 .067 7 54 3 I 34 6 1 1 107 .069 37 60 33 1 6 99 7 7 1 3 3 257 .071 37 572 8 1 8 6 318 9 8 1 14 6 3 1 13 7 3 1015 .073 42 167 53 2 27 1 172 27 11 3 7 10 1 1 16 7 8 555 .075 8 21 3 1 39 25 6 1 2 1 1 1 4 113 .077 59 38 2 89 14 2 1 5 3 3 1 2 2 36 257 .079 135 43 69 3 3 2 1 5 6 I 268 .081 2 164 13 1 16 2 1 8 4 1 3 215 .083 5 43 4 17 1 6 1 1 78 .085 2 1 17 20 .087 66 6 1 37 1 1 3 115 .089 26 29 105 2 1 2 3 15 183 .091 11 2 1 1 49 6 3 2 2 1 1 3 2 17 101 .093 3 8 2 13 .095 6 146 4 1 29 3 195 1 2 4 7 10 7 6 12 2 4 439 .097 3 103 11 7 2 205 2 2 6 4 1 5 1 4 9 2 1 368 .099 16 7 1 1 48 1 1 6 1 1 83 13.101 3 11 1 45 2 3 1 7 7 4 1 85 .103 1 162 6 1 3 4 255 5 5 3 7 3 14 3 7 479 .105 50 4 1 1 166 2 3 1 2 1 4 5 2 242 .107 1 13 1 1 16 .109 12 27 2 41 .111 18 1 49 1 1 1 71 .113 30 2 1 72 2 2 1 2 112 .115 8 25 1 1 1 1 37 .117 9 4 4 52 1 2 1 3 1 1 1 2 81 .119 36 4 86 4 4 134 .121 17 3 22 1 2 45 .123 3 2 3 1 1 2 2 14 .125 1 1 2 1 5 .127 20 2 3 39 1 1 1 1 1 69 .129 11 1 2 14 28 .131 6 7 3 16 .133 5 4 9 1 2 21 .135 56 I 1 78 2 1 1 140 .137 40 1 50 1 2 2 96 .139 12 1 8 1 1 1 24 .141 4 8 12 .143 76 2 86 1 1 I 6 173 .145 20 2 2 44 2 2 72 .147 17 33 3 4 2 3 3 65 .149 14 6 29 2 1 3 59 .151 22 3 1 72 1 2 1 1 103 .153 103 1 1 3 1 394 2 1 1 5 3 1 2 17 1 3 539 .155 8 4 16 2 2 2 4 38 .157 8 8 1 45 1 1 1 2 67 .159 12 5 8 53 1 1 1 4 2 2 2 1 92 .161 24 6 65 3 2 2 102 .163 5 2 14 1 22 .165 4 17 24 1 2 48 50 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 1. — Counts of fish larvae, tabulated by family, for all stations occupied on EASTROPAC I.- Continued. •c 3 n s z z o p < S5 8 g 3 § o O s s i i u to < c o 1 1 0} 1 5 'a 1 a u to 3 E CO SI (0 o H 13.334 37 21 17 1 116 2 3 1 1 5 3 1 208 .338 9 49 26 295 1 2 5 8 24 3 422 .340 4 11 23 2 47 4 4 1 4 100 .342 9 24 21 2 76 4 1 3 4 1 2 147 14.001 39 97 1 1 1 6 867 4 5 2 194 9 1 12 261 15 195 1710 .006 32 19 38 1 66 2 3 2 10 15 25 8 226 .008 34 4 32 2 1 86 1 2 1 1 2 25 4 2 197 .010 14 19 40 4 2 198 1 2 3 1 12 2 3 301 .012 6 1 7 1 1 57 1 3 1 2 2 4 4 90 .014 42 4 9 1 67 1 9 2 30 5 28 198 .016 19 1 20 8 2 4 2 44 16 5 121 .017 17 2 16 1 61 1 2 4 1 105 .018 41 48 64 2 2 424 4 5 24 1 19 634 .020 6 10 12 1 229 1 2 10 54 325 .022 7 22 14 3 80 5 1 1 32 4 169 .024 6 47 1 1 29 5 22 111 .027 23 31 42 3 387 2 7 9 6 87 34 19 650 .029 24 42 25 5 382 1 1 2 6 1 3 1 119 47 26 685 .031 30 43 46 9 2 594 15 2 6 1 1 3 75 5 43 875 .033 21 5 2 26 1 1 9 3 3 71 .040 48 2 2 36 8 3 4 6 1 21 3 21 155 .043 65 17 2 1 159 8 8 1 22 1 3 15 7 4 313 .047 111 3 4 4 22 3 2 3 9 6 7 44 218 .051 225 27 1 1 5 78 3 1 1 46 11 1 I 3 25 429 .055 154 2 2 40 4 8 210 .060 139 18 1 2 54 2 15 231 .066 13 1 II 1 26 .069 20 2 97 119 .076 3 1 11 15 .073 .081 2 16 I 18 37 .084 2 3 4 1 I 2 13 .086 2 1 7 3 13 .088 3 3 .091 2 40 1 43 3 2 91 .095 2 3 1 50 1 1 I 59 .099 2 3 1 15 21 14.103 .106 3 11 14 .110 8 27 1 1 37 .112 1 2 1 1 5 .114 2 2 .115 2 6 1 5 1 2 17 .117 2 I 1 1 5 .118 .120 1 6 1 15 1 1 25 .122 2 11 1 1 19 I 1 36 .123 7 23 7 51 1 1 1 2 9 102 .124 7 76 6 152 4 2 3 2 12 4 268 .126 3 20 1 2 6 53 1 3 2 3 4 1 15 114 .127 5 5 1 22 2 3 3 3 44 .128 5 60 3 9 145 5 6 1 ] 13 248 .130 3 44 1 1 7 45 2 2 4 3 2 1 5 3 4 15 142 52 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 1. — Counts of fish larvae, tabulated by family, for all stations occupied on EASTROPAC I.- Continued. a s t % « S Z § < -a 1 o g a o 1 IS :o § (0 < c o 1 1 o % c n 3 2 "3 o 1 O u O o s 2 rt -5 S. V 0. o u d •B o c o C in o c c g to 3 ■a u "9 c a, in s rt §■ 3 & rt o c rt 2 c 3 a a to s 3 JZ a o 2 > > c a « U & (0 d E J 8 o > H o £ > w s o 8 1 Q. & g 3 o JZ t >> E •a a> c o o £ U bo Q^ c CO •a 2 a o O E ■< c 2 s a g u c s o be S e a 3 s o "o o p £ a ■a lo ^ S o a u s o O S ^ rt ►J 3 2 g o Z O Z 0. ^ h c 3 I 11.022 1 1 c 1 1 4 .025 1 1 1 4 4 11 .027 1 1 4 4 C 1 1 14 .030 c c 1 .032 6 13 C c 19 .034 2 10 16 C ' 35 .036 2 1 c 3 .038 2 10 4 C 1 2 2 21 .040 5 4 39 C 1 4 2 55 .044 1 4 C c 5 .046 4 41 ) C 4 1 50 .048 1 6 c 13 20 .050 33 c 1 1 I 36 .052 56 c 2 58 .054 3 147 c c 159 .056 56 c 8 3 67 .058 27 c c 1 28 .060 4 53 1 3 c 1 1 72 .062 16 1 2 1 I 21 .064 2 43 ) c 2 3 1 51 .066 4 14 ) 2 9 4 20 3 4 I 2 63 .068 67 33 14 2 4 7 4 21 32 1 21 8 14 229 .070 1 15 8 e C 1 48 6 2 4 5 96 .072 28 6 22 1 12 7 44 21 2 24 7 4 178 .076 23 ) c c 2' 20 5 1 1 13 90 .080 1 18 2 1 c e 3 2 1 1 1 36 .084 63 0' i: 1 3 2 42 131 .088 2 10 £ c 6' 1 7 2 2 3 104 .094 5 8 4 c 32 9 1 1 4 2 66 .098 3 107 2 50 lOS 1 404 12 1 180 8 10 9 1 1 9 907 11.102 21 3 26 12 26 1 10 99 .106 6 c C 7 4 1 22 .110 41 8 c 7 I 1 1 1 57 .114 182 c 31 1 11 1 1 2 2 243 .118 70 c ; 3 84 .120 8 c 1 9 .124 37 c r 1 3 I 66 .128 1 31 c 2£ 2 6 16 1 8 98 .130 1 11 c 4 1 8 1 29 .132 4 3 C c 1 4 16 .134 26 39 3C 2 6 6 109 .136 30 39 4 8 2 60 15 168 .138 10 • 2 1 1 2 1 2 21 .140 2 c ( 3 1 12 .142 4 6 le 31 2 9 69 .146 10 3 c 1 2 1 17 .148 5 ) 1 c 4 3 13 .150 4 3 15 13 38 .152 10 13 i IS 1 2C 1 3 43 2 115 .154 1 e 5 3 15 54 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 2. — Myctophid larvae, tabulated by genus or species, for all stations occupied on EASTROPAC I. — Continued. t K 11.156 .158 .159 .161 .163 .167 .169 .171 .173 .175 .177 .179 .181 .183 .185 .187 .189 .191 .195 .197 .199 11.201 .203 .205 .207 .209 .211 .213 .215 .217 .219 .221 .223 .226 .228 .234 .238 .242 .246 .250 .254 .258 .262 .266 .270 .278 .282 .285 .287 .289 1 i % a ^ % 9 (0 a CB s B CO O o & o 4 8 19 3 2 1 1 1 1 3 2 3 4 3 14 1 5 7 3 17 4 1 3 4 2 9 1 1 (D 3 1 "3 ED >i > 5 fl •a U S « Q a 14 14 5 1 1 1 1 5 13 4 9 1 16 2 26 2 1 1 1 2 4 3 9 17 33 I I i g t s *• eo o Use I i 5 I g 8 111 U X s a -2 s s Z bo 14 3 58 62 17 18 32 57 19 8 51 14 7 2 17 1 2 1 1 1 2 2 1 4 « 2 1 2 1 5 2 2 9 23 16 2 1 3 6 2 13 6 13 5 11 3 4 7 1 9 14 15 30 1 2 3 7 6 14 19 1 I 8 9 7 17 2 6 1 1 2 1 7 6 1 11 6 2 7 3 1 4 3 1 5 5 5 a 2 2 4 2 1 2 2 13 98 8 4 20 5 1 20 19 6 4 1 3 4 2 2 2 1 1 1 4 1 1 2 2 1 2 1 3 1 3 4 5 3 2 1 1 2 1 1 2 16 11 85 4 3 7 26 6 16 1 2 8 2 6 4 3 1 2 3 3 13 3 1 18 12 1 4 2 5 27 25 4 1 1 1 6 2 1 2 8 3 4 2 17 7 5 3 19 6 2 3 1 2 1 4 36 1 1 8 2 5 14 1 1 2 5 1 4 1 1 11 2 2 2 1 29 19 103 22 117 10 2 20 3 1 5 4 3 13 13 4 24 19 2 4 60 9 8 17 40 21 12 28 71 44 16 10 74 20 7 16 46 10 95 6 198 57 149 108 85 38 17 1 116 82 8 30 3 87 12 131 55 FISHERY BULLETIN; VOL. 69, NO. I Appendix Table 2. — Myctophid larvae, tabulated by genus or species, for all stations occupied on EASTROPAC I. — Continued. Q •B s c c a (0 o E E a o o C bi bi o > >, O X X en CO H O c en n a H £ ffl rt J hJ - 2 11.291 .293 .295 .297 .299 11.301 .303 .306 .308 .310 .312 .314 .316 .318 .320 .322 .324 .326 .328 13 36 94 263 23 5 42 37 6 13 16 15 2 26 1 21 2 2 3 6 2 4 3 2 2 55 1 3 16 1 2 18 3 2 1 2 2 1 1 5 1 12 4 17 6 7 I 1 20 1 1 1 2 4 1 6 14 2 39 50 130 297 29 8 44 40 13 15 26 27 8 34 11 115 13 31 55 12.002 .004 .006 .008 .010 .012 .014 .016 .018 .020 .022 .024 .026 .028 .030 .032 .033 .035 .037 .039 .041 .043 .045 .047 .049 .051 .053 .055 .057 63 7 13 6 24 18 8 7 20 60 8 1 24 29 6 10 21 14 22 17 107 82 33 48 53 35 1 2 12 69 22 45 73 12 13 38 65 60 13 72 80 1 22 6 1 6 13 1 2 9 7 13 6 6 32 1 10 22 11 2 4 6 3 1 1 9 37 85 33 88 121 31 23 69 137 74 16 97 121 13 24 20 87 23 36 17 108 94 33 61 61 51 6 7 37 56 AHLSTROMt FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 2. — Myctophid larvae, tabulated by genus or species, for all stations occupied on EASTROPAC I. — Continued. as u s e o c o i 1 Si m O , >i c c bj (fl Q P Q CD 3 E 3 B 3 3 C i u 1 a a DQ > fi e JZ c u o > O a: X f^ & 3 U a> > Sa n a fc; t: en J vJ s- rt E c o 5 3 o > s s ■2 S 12.059 .061 .063 .065 .067 .069 .071 .075 .077 .079 .081 .084 .087 .090 .092 .094 .097 12.100 .103 .106 .109 .112 .115 .118 .120 .122 .124 .126 .128 .130 .132 .134 .136 .138 .140 .142 .144 .146 .148 .150 .152 .154 .156 .158 .160 .162 .164 .184 .186 .188 28. 2 5 1 10 6 19 4 3 1 7 3 11 1 26 32 104 555 4 337 195 2 25 16 204 6 65 18 80 7 103 27 127 38 5 12 62 36 33 67 10 277 4 41 1 12 5 14 5 19 28 2 2 3 1 6 11 21 2 5 47 7 2 e 1 7 15 2 3 25 48 7 1 1 1 1 7 14 4 1 4 1 1 5 1 1 3 13 1 2 1 1» 1* 1 1 2 2 25 3 2 4 1 2 2 1 1 1 1 1 2 1 2 2 12 7 9 2 12 42 3 2 1 1 5 10 1 7 5 3 1 56 5 25 17 14 15 11 1 5 37 30 12 7 20 140 27 5 35 25 8 1 17 54 7 6 14 6 1 1 2 3 2 3 4 13 1 1 4 5 2 6 10 1 1 1 1 48 3 2 11 22 2 6 3 2 6 10 4 12 11 1 2 6 34 9 3 3 3 2 2 1 3 1 1 1 2 3 3 2 1 1 4 2 1 2 1 7 2 3 17 4 6 11 11 10 10 16 13 2 4 35 6 1 3 1 3 5 1 1 1 4 3 3 6 2 13 1 2 4 2 1 3 20 2 6 3 39 8 2 3 1 1 3 7 3 1 2 2 14 2 1 3 3 1 11 1 5 4 7 5 1 3 3 18 6 3 193 1 1 1 7 20 2 3 2 3 5 3 1 1 1 6 4 2 5 2 2 4 2 1 99 41 109 614 366 227 71 294 110 129 389 207 64 18 71 377 101 56 124 319 65 32 72 107 15 30 29 108 49 12 8 20 19 10 69 84 72 11 11 86 37 12 14 41 19 5 36 45 5 57 FISHERY BULLETIN: VOL. 69. NO. I Appendix Table 2. — Myctophid larvae, tabulated by genus or species, for all stations occupied on EASTROPAC I. — Continued. c c t % n o V £ s 0} 09 O o s; <0 n u =1 H g i 3 E 1 CO a > h h 5 J D a c bl O tq E 5) m B U 0) > rt l3 a c f-i H ^ ^ a g- e to rt 2 £ rt rt c i (fl u > (D 0) 3 > o O o o 2; 2: s t 12.190 .192 .194 .196 .198 12.200 .203 .212 .215 .218 .221 .224 .227 .230 .233 .235 .238 .240 .242 .244 .24fi .248 .250 .252 .254 .256 .258 .260 .262 .264 .265 .268 .270 .272 .274 .276 .278 .280 .282 .284 13 1 2 1 1 1 1 1 80 10 28 92 92 22 102 315 22 126 194 2 145 10 7 6 7 9 5 127 3 17 57 12 1 17 7 6 2 23 14 17 205 43 38 13 22 11 38 26 24 15 31 44 35 61 25 8 19 5 10 11 2 5 1 1 1 1 1 1 1 1 1 1 1 4 3 63 5 1 1 1 1 1 1 1 54 11 16 40 3 13 2 2 3 1 2 1 2 13 39 4 1 5 3 17 5 8 9 2 13 10 21 35 176 98 61 47 471 30 16 107 61 42 5 1 10 16 5 6 12 16 2 1 40 2 3 1 1 7 I 2 1 1 1 1 6 18 105 10 2 2 3 16 8 1 7 2 8 1 5 5 2 6 6 3 4 17 11 2 2 15 2 2 2 6 1 2 6 12 5 30 2 1 4 3 2 2 9 1 3 2 12 1 5 6 1 1 1 12 2 5 35 3 1 7 2 1 1 1 3 2 6 2 3 11 38 4 1 6 3 6 1 1 2 4 1 1 1 6 45 16 22 12 36 91 36 70 300 202 127 209 1089 162 49 250 280 225 54 25 105 248 51 54 44 84 23 43 74 161 26 54 156 60 81 85 20 45 5 8 16 13.001 .003 .005 .007 .009 .011 31 315 1020 115 470 372 6 34 21 6 21 2 12 24 7 1 10 1 41 385 1075 133 494 374 58 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 2. — Myctophid larvae, tabulated by genus or species, for all stations occupied on EASTROPAC I. — Contimied. < El o s CQ e 1 01 CO o o CO Q) PQ u QQ r) 3 E 1 rt rt tn 00 > > .c ^ ^ F F 4= x: a >i o £1 £^ « CO e 0) rt > CO en 3 3 , (0 o o ^ 2 S bo 13.013 .015 .017 .019 .021 .022 .028 .030 .032 .034 .036 .038 .040 .042 .044 .046 .048 .050 .052 .054 .056 .058 .060 .062 .064 .065 .067 .069 .071 .073 .075 .077 .079 .081 .083 .085 .087 .089 .091 .093 .095 .097 .099 13.101 .103 .105 .107 .109 .111 .113 432 407 9 25 13 45 20 15 6 29 30 2 1 6 17 1 1 3 2 4 5 1 2 2 1 12 I 11 21 4 10 46 19 1 15 17 26 186 477 550 715 2 24 44 142 11 122 408 271 79 44 160 71 42 36 33 50 54 22 191 12 24 73 284 122 28 60 50 11 13 9 1 9 2* 18 2 I 12* 6 4 1 2 3 1 4 2 1 3 1 15 2 2 2 6 3 2 1 1 1 1 3 2 1 3 2 10 1 45 33 5 6 42 22 2 2 5 1 20 2 5 9 16 2 18 47 25 14 28 76 25 14 20 43 16 1 7 18 8 2 10 20 40 5 23 8 3 2 3 7 3 1 19 5 1 1 3 5 2 2 5 2 1 5 1 6 1 1 2 15 18 3 11 5 2 7 1 1 1 3 7 8 19 11 5 12 8 1 1 1 4 7 1 21 37 7 4 16 7 1 2 1 1 1 1 1 21 1 3 5 4 7 13 1 1 1 1 7 9 4 4 2 4 2 2 1 1 7 1 3 6 18 34 8 2 30 24 5 10 26 33 1 1 2 1 10 4 4 12 5 3 10 1 2 5 5 3 2 1 3 6 6 5 6 24 1 4 2 2 1 4 2 1 5 3 21 5 2 3 1 I 32 3 5 1 10 4 2 1 2 207 479 559 13 1219 409 2 24 44 158 13 142 469 307 109 105 300 133 79 77 144 83 59 44 274 31 34 99 318 172 39 89 69 16 17 17 37 105 49 8 195 205 48 45 255 166 13 27 49 72 59 FISHERY BULLETIN: VOL. 69. NO. I Appendix Table 2. — Myctophid larvae, tabulated by genus or species, for all stations occupied on EASTROPAC I. — Continued. a H < ■3 $ Si s a u CO a a F F 3 3 X o O X en « « R c O ■s !5 a. O £: «! -1 _; 5 o £ 2 S M =■ C OJ C 13.115 .117 .119 .121 .123 .125 .127 .129 .131 .133 .135 .137 .139 .141 .143 .145 .147 .149 .151 .153 .155 .157 .159 .161 .163 .165 .167 .169 .171 .173 .175 .179 .183 .187 .191 .195 .199 13.203 .207 .211 .215 .219 .223 .227 .231 .235 .237 .239 .241 .243 2 4 4 2 1» 2 3 1 4 2 25 2 20 18 7 1 1 3 52 7 56 2 3 6 3 1 4 4 86 6 1 1 1* 4 I 2 1 2 2 1 22 2 1 3 1 1 2 7 3 3 2* 4 4 3 5 1 1 4 2 39 7 4 1 2 14 2 1 2 2 7 2 1 2 1 I 2 9 12 35 1 1* 1 11 7 1 5 2 2 78 5 13 3 2 2 6 2 6 9 2 50 3 2 1 2 8 1 1 1 3 1 1 8 15 21 6 2 4 5 7 2 5 I 1 13 2 2 86 16 6 4 2 4 2 2 8 44 2 5 2 2 2 3 2 3 1 10 1 33 2 2 2 1 1 2 3 5 5 3 1 2 29 43 6 2 4 3 2 1 1 3 1 I 72 83 172 7 30 23 9 7 26 1 n 8 3 14 394 4 2 2 4 4 16 11 19 1 1 4 2 1 2 4 45 12 16 3 1 7 7 2 5 53 27 11 1 4 1 4 4 10 1 2 65 1 2 3 1 6 1 14 3 6 1 2 3 8 I 24 16 2 2 3 1 8 1 33 115 1 8 2 20 1 1 17 4 169 5 13 54 1 7 2 8 3 11 104 2 98 13 1 2 1 4 121 1 168 1 52 1 2 18 2 245 122 1 7 2 1 133 64 3 7 1 2 2 1 80 49 2 11 1 3 I 67 78 2 43 3 126 4 34 125 2 1 16 182 I 31 4 2 12 3 2 55 7 1 3 3 4 1 1 20 1 72 12 8 1 24 1 2 1 4 3 129 3 40 5 1 9 3 1 2 4 68 2 1 « 2 2 7 6 1 3 1 11 18 I 9 1 2 1 32 2 90 1 3 15 2 1 1 6 121 29 2 39 4 3 1 2 2 82 1 64 1 3 14 1 5 7 3 1 1 5 106 133 4 34 8 1 1 2 1 5 189 131 1 29 7 4 2 5 179 52 1 1 1 1 1 2 59 67 1 21 1 3 93 60 AHLSTROM: FISH LARVAE IN ELASTERN TROPICAL PACIFIC Appendix Table 2. — Myctophid larvae, tabulated by genus or species, for all stations occupied on EASTROPAC I. — Continued. % s o s o cd E DQ 1 1 % c (0 m 1 E © m o i E I E 3 £ X d d ID z % 09 u > 0. CL > OQ % c i d m E 1 K d oa ■0 i y E -0 4) c -0 c 3 BQ •a §■ CO 1 CJ >^ E H 1 < QQ 3 § CJ m o ed Q> O a a (0 CO p 1 5 (D > c bd o 5 CO > o c g ■q & n g w c (h £ § bx >, X £ a E I 1 & CO c •0 E n ►J z D s C4 ►J ■D ! & .2 c « t U .5 Q. M E D f 8 > > i .c "o Z CD .2 & u w z 1 £ 5 % 1 E CO CO s B t u ■a a 'rt u tc CJ ;s CO 5 13.245 37 20 57 .247 17 9 26 .249 43 1 2 46 .251 15 10 25 .253 5 1 6 .255 12 11 4 2 29 .257 4 5 1 10 .259 16 2 1 4 23 .261 8 4 1 13 .263 33 5 8 46 .265 11 2 1 14 .266 14 14 .268 12 19 2 33 .270 5 3 1 9 .272 11 2 13 .274 26 33 4 63 .276 38 48 D 1 2 89 .278 2 4 1 7 .280 23 6 2 31 .282 80 7 1 1 89 .284 13 7 13 1 34 13.318 1 2 3 .320 3 11 4 18 .322 ,0 C .324 c 25 1 26 .326 5 39 44 .328 28 7 35 .330 24 24 .332 62 1 63 .334 111 1 4 116 .338 274 15 1 1 2 1 1 295 .340 33 5 3 3 1 1 1 47 .342 62 6 2 3 1 1 1 76 14.001 4( 1 725 1 49 18 5 17 6 867 .006 9 43 3 1 2 8 66 .008 78 3 5 86 .010 6 179 2 4 6 1 198 .012 47 2 7 1 57 .014 6£ 1 67 .016 8 8 .017 54 1 1 4 1 61 .018 246 I 148 23 4 1 1 424 .020 22E 2 1 1 229 .022 7C 3 2 1 80 .024 34 13 47 .027 372 11 4 387 .029 ) 371 6 382 .031 ) 54C 1 1 19 13 6 2 1 7 594 61 FISHERY BULLETIN: VOL. 69. NO. I Appendix Table 2. — Myctophid larvae, tabulated by genus or species, for all stations occupied on EASTROPAC I. — Continued. 1 1 c o c a a a o 1 s c 1 tn 3 s o o o a a m m z n g > o c OQ 3 ■i in o d rt § to o 3 c o Hi > S n 3 g 2 o E 5 a. s o to V) 3 o > c to 3 "o .Q g > a tn § s d £ g a ^> > to > •a c o i s (0 & d to E s § 1 cS > w E O .C s i (A 2 1 to f o >^ E -a c to ■o f V e to •a i H X J= (U O w g s Q Q ^ rt (A o ^ JZ 0) < c a D ti tl o c o O E B D '£ ^ y "o O O £ Q •D « rt H u o o > > M rt flji o > o O L. ^ 'u C o m n u b Q b U o K X J ,J J ►J '^ s 2 2 0. (- 3 Q H 14.033 21 c C 2 G G 1 2 26 .040 1< i 4 5 G 9 G G 1 36 .043 2 ; s 40 G 41 25 G 2 3 1 9 159 .047 ) c 4 8 G 1 G 22 .051 ) 3 c G 27 12 G 1 1 6 78 .055 ) 3 1 1 G G 2 G G G G 40 .060 ) 1 1 c G G G G G G 1 G 18 .066 c G G G G G G G 1 .069 ) c G G G G G G G G .076 c G G G 1 .078 ) c G G G G G .081 ; c 8 G G 3 1 1 18 .084 1 c G G 4 .086 c c ( G G G 1 7 .088 ) c c G G G G 3 .091 ) c G 40 G 1 1 43 .095 ) 1 1 c G C 1 G 1 G 19 12 50 .099 7 c 7 G 1 15 14. 103 ) c c G .106 ) c G G .110 5 c 14 G G 1 6 27 .112 ) c c 2 G G 2 .114 c 1 G G 2 .115 ) c 4 G G 1 5 .117 ) c c G 1 1 .118 ) c ( G G .120 • G G 4 2 15 .122 1 G G I G 9 1 1 19 .123 ] 6 4 1 G 1 16 1 13 51 .124 1 1 40 18 1 2 1 2 51 1 10 152 .126 5 1 5 3 21 1 13 S3 .127 I 2 1 G 1 5 9 1 22 .128 I 1 33 c 2 G G 4 3 72 9 2 145 .130 3 G G 5 2 G 21 5 45 .131 GOO G G G 2 2 .132 GOO 2 G 3 1 I 8 .134 C G G 1 2 11 .136 ) 4 G G 43 .138 ) 1 ] G 11 G G G 2 29 .142 ) 10 G G G G 1 1 110 .146 ) 15 5 13 G 6 G 176 .150 ) 3 6 G G G G G 2 5 52 .154 4S G G G 16 8 2 3 92 .158 G G G 2 G G G 4 30 .164 3C G G 5 1 2 G 2G 135 .172 2 6 G G G 1 1 G G 26 .174 ] 4 G G 2 3 1 G 26 .177 C G G G G G G G G G .183 1 G G G 1 G G I 4 .188 3 18 3 4S G G 6 2 9 5 6 261 62 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 2. — Myctophid larvae, tabulated by genus or species, for all stations occupied on EASTROPAC I. — Continued. a n s 2 Z o c V c a c E o tn o 5 c o (0 c CO § V ta O 3 en £ > o c Vi 3 O i rt rt to 1 X u c & c en > E s a u rt E 3 E £ D 1 a a « rt c a -a « B > c rt 1 s s D o rt u el u rt c a. & 6 3 c rt > "rt > s o (0 c •g c i £ to o u g- E 8 1 c c rt > » e o & a a w « g 3 O £ O §• u £ 2 rt u to CO T3 1 O O >> E H ^ J= 0) CJ u c o" a 1^ ^ 5 3 w o ^ J= o c < c 2 i g § o C s bf £ £ '5 3 s o o o p £ Q ■o rt H a o o > > rt rt o o 2 > o o ^ U c o u n U S s s u o E .J ►J J J s Z z s. H 3 s H 14.194 ) 155 I C 7 C 158 2 12 4 8 5 5 1 1753 .195 24. ! 2 c c 3 4 252 .199 1 ) c 2 1 2 16 14.203 9( ) C 1 6£ 3 1 3 4 4 1 7 179 .209 2. ) c c 2 25 .213 18] c D C 2E 206 .218 16f C 8 1 177 .220 ) 2( ) ( c 2 22 .220 4 ; 1 c 2 49 .224 9 ) G c 21 2 2 115 .228 2f c 1 1 30 .230 ) 3 ) c c c 1 1 41 .232 2 c c c 1 31 .234 9« c c c 81 1 48 228 .236 3( ) c c 4 34 .240 7( ) c 4 c 12 1 20 2 2 1 1 3 116 .243 2 i c 2 C 14 2 2 1 44 .247 ) 4 c c c 2' 5 2 1 6 1 86 .251 ) 1 ) c 1 c c :; 1 1 25 .255 21 3 C 1 c c 2 3 3 1 227 .259 ) 4 ; c c e 2 1 3 1 53 .263 9- 1 c c c IC 1 105 .267 1 c c c : 1 8 .276 ) c c 1 6 2 1 13 .280 ) 5 C 2 C c 2 26 3 5 44 .283 ) 1 ! C c c c 8 1 1 22 .287 ) C c c 4 1 2 4 1 15 .291 ) ) C c c c .295 ) 4 ) C c c 15 1 65 .300 ) 1 i C I c c c 1 18 .303 ) 18 i C c c 5 3 3 200 .306 ) 2 J c c 1 4 32 .310 6 c 2 C c 8 1 5 4 14 96 .314 ) 3i i c c c I'S 5 2 59 .318 ) 49 c 7 C c 38 23 5 2 566 .323 14 ) c c c 2 3 3 165 .326 i 57 ) c c c 7: 1 4 5 659 .330 ) ( ) 2 ! C c c 1 c 23 63 FISHERY BULLETIN: VOL. 69, NO. 1 Appendix Table 3. — Counts of selected categories of fish larvae, tabulated by station, EASTROPAC I. n 10 u tt E n 2 3 E g 1 u z o > u u u 'c m *> .s & 1 1' 1 C 2 _3 § 1 c B a 1 I s o u E i 1 i w 3 D E « t o "3 'u 1 a u Q. o. tA 1 < CD 1 "o o CO 1 i 1 1 c 1 o o 3 s 2 CO si E E CTi Q a "Z X o. CO ca E i ■3 2 11.022 ) ( 10 .025 ) f 46 1 .027 ) J 34 1 I .030 ) ( 1 .032 1 ) ( 15 D .034 1 ) ( 88 .036 ) ( 26 .038 4 ) ( 22 e .040 ) 1 1 18 c 1 1 .044 2 ) ( 9 .046 3 ) 1 57 c 1 .048 12 ) 41 c .050 24 ) 1 22 c .052 15 ) 2 c .054 U ) ^ .056 10 ) 8 .058 10 ) 2 1 .060 13 ) 1 ' 1 3 1 .062 ) C .064 ) 1 C 2 .066 ) 2 c 2 2 1 1 11 1 .068 5 ) 6 1 7C 1 3 3 4 .070 1 ) 6 1 1" 3 1 1 8 1 .072 2 ) 2 6 2 6£ • 1 9 1 .076 6 ) 5 2 682 1 4 .080 7 ) 2 1 139 1 .084 11 ) 3 358 1 3 2 .088 1 ) 9 31E 1 1 2 .094 ) 9 41 1 1 1 2 .098 2 ) 2 ) 8- I 1 11.102 6 ) 3 8 4 2 .106 1 1 K 4 2 .110 8 ) c c .114 1 J 1 2 c 44 3 1 .118 4 ) 2 e 4 c 2 .120 1 3 2 1 D 1 1 .124 5 7 1 c r 1 .128 3 6 c 95 2 1 .130 3 6 c 1 .132 1 5 1 c 2 1 .134 3 3 24 c 1 1 166 2 .136 3 2 I 2 c 20 2 .138 3 1 3 c 2 1 .140 3 4 c ] .142 3 9 c 4 1 .146 3 20 2 c 3 .148 3 61 1 5 c 1 .150 a 70 1 c 1 4 .152 3 89 3 i 1 c 9 1 1 1 2 1 .154 » 2 5 3 c 1 .156 B 83 J c .158 3 20 1 3 f 1 .159 70 2 I c 6 3 .161 3 1 3 D c 2 1 64 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 3. — Counts of selected categories of fish larvae, tabulated by station, EASTROPAC I. — Continued. 1 m u E n 3 0> 1 § CO > c .§ t. tl c CO ">, 3 u i o g 3 5 c c nl z « o % < o o >, o & (0 o I a S 3 o o o 3 E M 3 "o u 3 3 "a c c £ .2 s oil 2 1 s o u « to 1 i m E 3 « o 1 E 1 ■e o % 1; u Q. a 1 < u E "Z to 1 i 1 n i c 1 o o u o o -a z J2 E Q m % 1 & E 3 c o u u s 2 u o 11. 163 8 a 1 .167 25 9 4 1 .169 3 1 1 r .171 11 .173 9 1 .175 1 .177 5 1 .179 4 1 1 .181 13 1 .183 3 2 D .185 4 .187 19 3 c 1 .189 20 1 c .191 1 c .195 4 10 c .197 8 32 5 2 1 c c 1 1 c 3 .199 5 1 2 c c 11.201 2 1 c c .203 8 12 3 2 I c c .205 22 20 2 9 3 c c .207 10 5 c c 1 .209 3 3 1 1 .211 35 4 1 c 1 .213 13 10 1 12 1 3 1 .215 3 2 D 1 3 1 .217 3 5 1 1 .219 1 .221 18 2 36 1 1 .223 8 5 .226 2 3 .228 1 2 c 1 .234 2 7 2 8 1 2 1 1 1 .238 3 5 1 D .242 4 13 1 36 c 4 .246 2 15 36 } 1 I 1 .250 1 1 12 8 3 1 1 c 1 .254 5 15 1 c 2 .258 3 1 8 46 3 c 1 .262 2 10 58 D c c .266 3 3 30 3 c .270 4 1 17 D 7 : c .278 13 1 13 142 ) 1 c c .282 1 6 1 20 1 ] ] c .285 9 5 5 2 1 1 1 c 1 .287 1 4 14 1 2 3 2 C 2 .289 7 4 5 3 1 IS c 6 .291 1 1 I 3 4 C .293 7 1 1 2 3 6 14 1 .295 10 5 10 3 3 1 1 3 2 .297 5 3 9 D 3 2 1 1 4 .299 27 2 3 5 3 1 1 11.301 1 13 3 1 3 3 .303 12 2 45 1 3 1 .306 4 64 1 3 1 65 FISHERY BULLETIN: VOL. 69, NO. I Appendix Table 3. — Counts of selected categories of fish larvae, tabulated by station, EASTROPAC I. — Continued. o s E E o g § p 1 fa (0 9 10 3 m O t 3 rt c & m O JZ g s > CO 1 1 in 3 g g 3 E [0 1 s 3 i 'C ,1 u c u _3 1 1 C & E u n a 1 o u 1 d. & E 3 to o 1 1 V s 3 ■§. u o V JZ (0 1 1 re o CO 1 1 d & c JZ g o o o 3 ■a (0 B rt o s E E ri a s §■ E 3 o s o m (0 ^J Z < o ia s > B s m M !- < X o z B f~ u 11.308 1 J 4 2 1 .310 4 J ( 6 1 .312 ) 1 59 1 1 1 .314 5 1 32 1 1 .316 ) 3 1 1 .318 ) 2 .320 1 ) 10 1 .322 ) 33 .324 ) 19 1 .326 ) 36 .328 ) 31 12.002 3 ) 11 1 .004 3 ) n 3 .006 2 ) 3 12 5 2 .008 3 ) 6 59 2 1 .010 8 ) 97 .012 4 ) 8 16 1 1 .014 4 ) 5 33 2 .016 8 ) 4 178 4 1 2 .018 ) 199 7 1 .020 3 ) 3 20 4 1 .022 ) 4 11 1 1 .024 3 ) 8 234 32 I .026 4 ) 2 99 3 .028 ) 31 2 3 1 .030 6 ) 12 1 3 .032 ) 13 1 7 3 .033 3 ) 36 3 6 1 .035 1 ) ] 72 4 5 2 2 .037 9 1 10 1 2 .039 4 3 3 .041 3 2 20 3 3 1 .043 28 2 3 1 .045 7 3 c .047 1 2 2 3 1 1 .049 2 2 52 1 2 .091 68 1 .053 1 18 2 1 .055 c 7 2 .057 2 c 13 .059 21 12 66 1 .061 8 6 .063 8 .065 11 44 .067 2 A 31 2 19 7 3 1 .069 5 6 c 1 11 1 2 1 7 .071 9 2 16 I 1 .075 19 6 1 119 1 2 1 2 1 1 2 .077 13 ; c 23 2 1 1 4 .079 17 24 c 2 21 2 42 3 2 .081 29 15 c 59 2 30 2 1 .084 14 5 6 8 .087 1 3 ( ) 6 10 1 66 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 3. — Counts of selected categories of fish larvae, tabulated by station, EASTROPAC I. — Continued. ED tn 10 E £ E 2 -> 3 e o a .1 u 1 3 (0 3 m 1 3 1 n c c « 2 1 'rt < i o 1 a 5 ! 3 a o o o > s 3 E 3 s i « i- u .5 > O n c B s E en 1 n s 1 1 C/3 a. a. E « o I i u 3 o 1 s a a a m 1 < CO E re Ij a i 1 1 o o o u 3 •o QJ rt u i 2 rt 4) E a ri & E 3 c o t 1 "3 ■3 rt o u 12.090 4 1 7 e c .092 4 41 c 1 .094 3 3 t 1 124 c .097 3 8 46 c D 1 1 12.100 1 2 ( 1 10 c 1 1 1 1 .103 ( 1 33 c .106 2 B ( ) f 35 1 1 3 .109 16 .112 ) 1 4 .115 1 J ( 12 36 3 1 .118 ) 18 141 1 1 11 2 3 1 .120 4 3 .122 ) 1 4 .124 5 D 1 .126 ) 4 18 1 D .128 ) C 8 .130 ) C •) .132 ) 1 6 .134 ) IC 18 .136 13 .138 ) c 12 .140 18 2 2 .142 ) 22 86 1 1 .144 ) IE 147 1 1 .146 ) C 12 1 .148 ) C 3 .150 ) 28 6 1 16 1 .152 ) E 5 2 .154 ) 8 3 D .156 ) 7 1 3 .158 ) 42 8 2 1 1 .160 ) 19 .162 ) 1 1 .164 24 15 1 .184 ) 31 17 1 .186 ) 1 1 1 .188 2 1 .190 ) 10 2 .192 14 1 5 .194 4 1 .196 1 .198 2 12.200 3 3 1 1 13 D .203 1 3 1 .206 ) D 15 1 1 .209 3 2 1 2 .212 1 17 17 5 1 .215 16 2 27 1 2 12 1 I .218 9 2 11 6 4 .221 IS 4 9 16 1 .224 ) C 48 2 201 2 2 .227 C 8 5 81 1 1 1 1 1 .230 i C 1 4 1 .233 4 i C ( ; 1 2 46 67 FISHKRY BULLETIN: VOL. 69, NO. I Appendix Table 3. — Counts of selected categories of fish larvae, tabulated by station, EASTROPAC I. — Continued. at c aj u M E £ e o n 3 E 1 a u > c c *£ EC 3 n m O 1 a a. 8- C i z Q. « o 1 < to Vi o § Q Q I o 1 3 £ w 3 O £ S i .5 'C u u p 1 n c E u HI & £ 1 u a o £ s o u m n 2 3 CO s, D o & o E 1 •£ o •a u 1: i i < 1 a c o ffl i c s o o u o o -o w s o « z to rt "a! E E rt D 1 d m e 3 c 1 o 12.235 25 ) 1 9 c 49 11 1 .238 17 ) 7 31 1 1 17 .240 11 ) 1 3 2 14 1 23 1 2 1 .242 ) 2 ' 2 12 1 3 .244 ) f 2 4 2 1 9 2 22 5 .246 11 ) 1 I 8 1 7 2 .248 ) 6 f 1 : 2 1 .250 ) 6 C .252 ) 2 c .254 ) 2 c .256 3 ) 1 2 1 .258 ) C .260 2 ) 1 15 C 2 2 .262 2 ) 5 97 1 .264 2 ) 6 14 1 1 .265 3 ) 7 11 1 .268 ) 2 103 1 2 2 .270 1 ) 29 C .272 4 ) 5 38 c 2 .274 ) 4 36 I .276 ) 138 c .278 1 ) 1 164 c .280 ) 2 20 c .282 1 ) 2 21 c .284 ) 1 118 c 13. 001 8 ) 3 90 c 1 .003 14 ) 3 J 1130 1 1 2 1 .005 54 ) 6 1 300 c 3 1 .007 9 ) 2 11 c 7 I .009 8 ) 9 c 7 .011 (i 2 1 .013 13 ) 8 c 1 1 .015 4 ) c 4 .017 16 ) 61 1 I 8 1 .019 9 ) 82 c 9 33 1 1 .021 4 ) 2 c 20 .022 1 ) c 1 .028 4 ) 6 c 1 .030 7 ) c 7 2 .032 ) 24 c 52 8 .034 23 ) 60 c 4 41 1 3 .036 8 ) c .038 28 ) c 2 .040 20 ) 5 10 1 20 1 .042 11 ) 5 6 c 1 4 .044 10 1 3 11 c I 1 .046 10 ) 5 73 4 1 1 .048 29 ) 1 ) 291 2 1 1 1 4 .050 10 ) 5 36 1 .052 i:i ) 1 J 1 181 c 4 1 5 .054 14 ) I 9 1 5 76 4 3 11 1 .056 33 ) I 2 ) 2 27 454 16 1 1 6 .058 6 ) J 3 8 I 10 319 1 7 68 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 3. — Counts of selected categories of fish larvae, tabulated by station, EASTROPAC I. — Continued. c IS s g s m :3 s 1 u 2 O 1 1 c e 1 3 3 ta 3 o "5 g 1 ffl c o c d 2 d n o 1 < i 1 o "o >, o & o g a Q d a m 3 i o f — 3 E 3 £ d a ft u 1 > u w 3 m 1 1 o ffl B 1 a o i m E a o w B IS 3 •g. t o u ! 1 < 1 1 o » c s 3 d D. c s 1 o o u o 3 •a o u rt u u 3 §. IS u B i o rt % 1 d at E 3 o o 13.060 5 2 2 14 8 17 a .062 7 c 3 1 .064 15 5 18 43 1 .065 2 4 1 11 56 1 .067 7 2 c C 52 .069 37 1 2 c 13 45 1 1 .071 37 17 c C 553 6 1 14 4 1 .073 42 13 c C 153 1 3 4 5 .075 8 3 c 18 1 e 1 .077 c 59 2 5 2 .079 1 c 134 5 1 .081 2 c 164 1 .083 5 c 43 .085 c 2 .087 2 c 64 2 .089 9 c r 2 .091 11 2 I 1 .093 : .095 6 25 1 120 2 1 10 1 .097 3 11 1 87 1 1 1 c .099 4 1 11 13.101 3 1 7 1 .103 1 36 125 1 2 2 6 .105 20 30 1 2 .107 1 .109 1 11 1 .111 7 1 .113 12 18 1 1 1 1 .115 4 4 1 .117 4 1 4 1 1 1 .119 26 3 6 .121 10 6 1 .123 3 .125 1 c .127 13 7 1 c .129 9 2 c .131 4 c .133 4 c .135 46 10 1 c .137 12 28 c .139 3 9 c .141 2 2 c .143 21 55 1 5 .145 12 8 .147 1 16 3 .149 6 8 1 1 .151 7 15 .153 44 59 3 .155 8 2 .157 3 3 1 .159 8 1 3 1 4 .161 11 13 .163 ) 5 c .165 3 4 c 69 FISHERY BLLLETIN: VOL. 69, NO. I Appendix Table 3. — Counts of selected categories of fish larvae, tabulated by station, EASTROPAC I. — Continued. 1 CD h B E e g o u g p < 00 >, c bi ca CO 1 a 3 ca _3 ■£ 3 CO o t 1 i a c s 5 z 09 1 o CO u < i g 6 d CQ g 1 a 5 a. & to a i — 3 s CA 3 y cfl s C8 r at g i > u t£ en 3 5 CQ a "3 c c E e m Q O 2 1 .2 6. & E to § CO 1 u E (0 3 o f 1; CO a. Q. 1 < 03 E a c « i c o x; o o Li o 3 •a a 3 CO 2 m rt E a — 1 X E 3 c o a 1 2 13.167 5 14 .169 7 c 76 .171 2 c 16 13 .173 7 ( c e 4 1 6 .175 22 6 c 169 1 1 45 1 1 .179 15 6 c 105 1 7 1 .183 50 3 c c 36 c 6 .187 43 2 c 26 c 1 .191 10 6 2 lis c 1 7 1 .195 10 f c 194 c .199 5 2 2E c 1 13.203 3 1 2 9 5 c .207 11 1 ' 14: c .211 5 6 1 27 c 1 .215 6 1 c .219 9 8 c .223 2 3 £ 15 c 1 .227 9 1' I 4 20 3 1 .231 9 1 5 C 29 c .235 9 1 C 31 c 1 1 .237 6 1 c 3: 1 7 1 1 .239 3 7 c 34 c .241 2 c 4 c 1 .243 11 c 13 c 1 .245 7 c 13 c 1 .247 9 c 11 c 1 2 1 .249 1 c c .251 6 c 10 2 c 3 .253 20 c 2S 4 c .255 7 c 29 c 1 15 1 3 .257 8 c 3 2 c .259 17 c le c 5 .261 8 c 36 c .263 19 c 54 c 1 11 .265 6 1 c c 12 8 c 1 1 .266 c 2 c 2 .268 3 26 c 1 .270 4 2 18 3 c 12 1 1 .272 2 c 3 2 c .274 1 3 49 6 3 1 1 .276 5 2 89 3 c 3 19 .278 1 1 20 2 c .280 8 3 5 c .282 3 33 6 c I I .284 18 60 2 1 13.318 13 1 c 1 1 .320 8 16 c 13 .322 C 5 c 1 9 1 .324 10 4 c 2 4 .326 13 9 c 18 1 .328 2 9 c 7 .330 4 12 c .332 1 1 ) 0-2 c 2 1 70 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 3. — Counts of selected categories of fish larvae, tabulated by station, EASTROPAC I. — Continued. — QJ •c a V u 6. & 3 a £■ h cd ^ 05 ? 8 O > 3 JZ S o o o p <0 6 o "H ^ 3 (8 ^ £ < U u t; > « CO rt d o ft a ta u h o o a i5 1 o "E £ 3 "o u i a C u s > Li m 1 o H n 1 o 3 E CO CO 13 1 ri D 3 3 1 3 *S u: U Z EC H 14. 131 14 .132 8 17 1 1 2 .134 1 3 1 .136 1 18 .138 9 2 90 9 .142 1 53 4 I 1 .146 16 30 111 1 8 .150 33 1 2 1 45 4 1 5 .154 28 6 9 1 372 1 7 3 .158 4 1 219 1 1 .164 8 4 1 48 3 6 1 .172 1 2 5 90 12 .174 3 1 3 33 .177 3 .183 1 1 .188 34 4 9 155 1 2 36 1 1 .194 161 7 22 98 1 22 1 4 .195 54 16 2 .199 15 5 196 1 20 3 14. 203 3 2 1 1 .209 5 2 10 .213 34 10 86 11 1 .218 27 1 38 2 1 4 2 .220 2 3 13 .222 2 4 2 I .224 9 3 6 31 1 7 1 .228 2 5 2 .230 1 5 9 .232 9 49 12 .234 9 2 867 1 161 1 .236 3 16 1 10 .240 21 1 4 31 85 1 .243 24 1 7 19 5 .247 4 13 39 1 .251 8 3 1 1 23 1 6 .255 1 209 10 76 59 1 6 .259 16 40 1 5 .263 2 2 231 2 .267 3 33 1 2 3 .276 9 6 52 2 1 .280 7 3 59 2 2 6 .283 3 13 1 1 .287 5 3 59 9 .291 .295 4 1 63 2 5 .300 1 286 1 .303 3 490 2 8 1 1 1 .306 12 22 2 .310 70 21 9 12 1 .314 24 1 24 .318 32 2 2 66 1 1 .323 n 24 1 .326 15 12 1 65 8 .330 1 72 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 4. — Summary of occurrences and numbers of larvae of eight families, limited in distribution to a broad coastal band or around offshore islands. « S z o H < CO 0) eg •o a u "a 1 c o c >v CO -a '5) u o 4) ■V 1 ►J "B 1 o a; a "B "c & o o CO a m z z c < CO '3 c o o "a be c W n c o 1 CO 8 CO 1 u u eg V rt 'u Si rt .J B o O "5 c & o eg 11.076 1 14.001 5 1 1 84 55 11 11.246 1 .006 1 5 1 .008 2 5 12. 020 1 .010 3 2 .024 1 4 .012 1 1 1 .026 10 .014 6 4 11 1 .028 3 3 .016 34 .030 1 1 .017 1 .031 7 .018 3 10 4 .033 1 2 1 2 1 2 1 1 .020 n 1 1 1 .035 6 5 3 1 .022 14 1) 2 1 .041 1 1 .024 4 6 5 6 .059 1 .027 n 3 5 1 4 36 9 12.221 CI 2 .029 7 2 12 9 37 .256 1 .031 3 3 1 18 4 .262 1 .033 1 1 1 2 .264 1 .040 6 5 1 .268 1 e .043 1 2 .047 1 1 3 13.003 1 1 6 .051 1 .005 1 1 .055 1 .007 1 .060 52 2 .011 9 1 .066 11 .019 13 1 70 49 2 47 12 .069 97 n .021 2 7 11 3 3 1 .076 11 .030 1 2 14.106 3 .032 e 12 8 .110 1 .034 9 23 3 .154 5 .040 1 .158 5 1 8 3 .042 1 .164 9 a .054 1 .172 2 11 22 3 n .056 1 .174 1 9 4 2 1 .062 « 11 2 .177 60 a 2 6 1 1 13.235 1 .194 1 1 1 9 .237 1 n .195 2 .239 2 .199 9 2 1 .245 13 14.209 1 a .247 5 .213 3 .249 1 .220 I 1 .253 72 .222 1 .255 2 1 2 2 3 .224 3 1 .257 1 .228 1 4 .261 41 .230 2 2 .263 3 2 .232 2 .265 1 .234 9 3 8 3 .266 1 .236 1 .268 a 1 .240 1 1 .274 3 .243 1 .276 2 .247 2 13. 320 1 1 7 3 14.303 1 1 .328 2 1 .314 9 1 .330 4 .318 10 4 2 43 5 .334 1 .323 1 3 1 .338 17 .326 13 2 23 73 FISHERY BULLETIN: VOL. 69, NO. I Appendix Table 5.— Numbers and kinds of larvae of Gempylidae-Trichiuridae obtained in EASTROPAC I collections. 03 3 « IS i K "E m s § .1 u m B o c & 03 3 a "a E 01 3 C S 03 u a m s 1 u 2 o D3 ta 3 1 03 3 £ 03 a o ta u < 13 £ O 5 < Z 1 a S 3 i 11.056 1 13.107 1 .064 1 .119 1 3 .072 1 .137 2 11.114 1 .139 1 .138 1 .147 1 e .140 1 .153 1 .146 1 .159 2 8 .158 1 .167 1 fl .159 1 .171 1 ( 11.213 1 .173 1 .219 1 .175 I .228 1 .179 3 .234 1 .187 2 .295 2 .191 1 .297 2 13.235 1 11.318 5 .245 1 .320 1 .280 1 .324 1 .326 2 14.001 1 .010 1 12.004 1 .012 1 .014 1 .029 1 1 1 .020 1 .031 1 .047 2 .095 .081 1 14.122 12.115 1 .123 .118 6 1 .124 1 1 .120 1 .126 1 .144 1 .127 3 .150 3 .128 6 .152 1 .130 3 .158 1 .131 1 .188 1 .134 1 1 12.246 2 .138 3 .260 1 .142 2 .262 1 .146 2 .272 1 .150 1 .276 1 .164 1 .188 1 13. 048 1 2 .194 2 .054 17 .195 1 .056 2 14.222 1 .071 6 e .224 1 .073 7 .234 8 1 .075 2 .240 1 .077 3 .259 3 .081 8 .280 1 4 1 .083 1 .283 1 .095 7 .287 1 2 .097 1 4 .295 1 .101 1 6 14.318 1 2 .103 7 .326 1 .105 2 .330 1 74 AHLSTROM; FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 6.— Numbers and kinds of flatfish (Pleuronectiformes) larvae obtained in EASTROPAC I collections. 5 t- w 1 t3 w a, en 1 C3 a £ U O U W Cfi s 12.028 1 14.001 1 5 1 35 .030 1 .006 1 2 .031 2 e .008 1 3 .033 4 1 6 6 .010 1 1 1 .035 3 .014 2 4 .045 1 .016 5 1 .017 2 .013 1 1 13.007 1 .020 5 .009 1 .022 1 3 1 .011 1 .024 1 9 .013 5 .027 1 6 1 3 9 .015 1 1 .029 1 5 2 24 .019 6 1 1 25 31 1 .031 1 30 .021 2 2 13 8 .033 1 2 .030 4 .040 1 2 4 .032 8 .047 1 .034 2 4 9 .055 1 2 .036 1 14.164 1 1 .040 1 2 1 3 .174 1 .042 1 1 6 1 .183 1 .054 1 .194 1 13.245 1 .195 1 .251 1 .199 1 .253 4 4 14.209 1 .255 3 1 9 .213 1 .257 1 .220 3 .259 1 1 .228 1 3 .261 1 1 1 .230 1 .263 1 3 8 .232 1 .265 2 1 .234 2 2 3 1 13.318 2 1 1 .236 1 2 .320 2 2 .240 1 .322 5 .259 2 .324 1 .295 1 .326 1 2 14.300 1 .328 1 .303 1 1 1 .334 1 .306 1 .314 1 .318 1 2 1 19 .323 1 3 2 2 .326 1 4 3 .330 1 75 FISHERY BULLETIN: VOL. 69, NO. 1 Appendix Table 7. — Standardized haul factors (SHF) : These factors are used to adjust original counts of larvae to the comparable standard of numbers of larvae in 10 m" of water strained per meter of depth fished. Station SHF Station SHF Station SHF Station SHF Station SHF 11.022 3.06 LI. 156 2.74 11.291 3.46 12.061 3.33 12.192 3.27 11.025 2.87 11.158 3.12 11.293 2.93 12.063 3.27 12.194 3.45 11. 027 2.38 11.159 2.64 11.295 3.16 12.065 3.23 12.196 3.32 11.030 2.47 11.161 3.35 11.297 2.86 12.067 3.36 12.198 3.40 11.032 3.01 11.163 2.64 11.299 3.57 12.068 3.39 12.200 3.18 11.034 3.64 11.167 2.97 11.301 3.31 12.071 3.34 12.203 3.29 11.036 3.04 ] 11.169 3.27 11.303 3.19 12.075 3.33 12.206 3.53 11.038 2.80 11.171 2.92 11.306 3.22 12.077 3.42 12.209 3.51 11.040 3.32 ] 11.173 2.94 11.308 3.15 12.079 3.56 12.212 3.32 11.044 2.81 ] 11.175 3.47 11.310 3.19 12.091 3.53 12.215 3.27 11. 046 3.24 ] 11.177 1.36 11.312 3.42 12.084 3.73 12.218 3.02 11.048 3.08 ] 1.179 3.37 11.314 3.18 12.087 3.86 12.221 3.07 11.050 2.36 ] LI. 181 2.74 11.316 2.84 12.090 3.10 12.224 2.58 11.052 2.86 ] 1.183 2.92 11.318 3.27 12.092 2.55 12.227 2.96 11.054 2.54 ] 1.185 3.19 11.320 3.34 12.094 2.29 12.230 3.72 11.056 2.90 ] 1.187 2.75 11.322 3.01 12.097 3.01 12.233 2.66 11.058 3.28 : 1.189 3.00 11.324 3.02 12.100 2.48 12.235 3.56 11.060 3.15 ] 1.191 3.79 11.326 2.84 12.103 3.28 12.238 3.21 11.062 3.72 ] 1.195 3.11 11.328 2.62 12.106 3.55 12.240 3.22 11.064 3.01 ] 1.197 3.14 12.109 3.39 12.242 3.41 11.066 2.12 ] 1.199 2.46 12.002 3.12 12.112 3.43 12.244 3.36 11.068 2.62 ] 1.201 3.27 12.004 3.02 12.115 3.48 12. 246 3.14 11.070 2.25 ] 1.203 3.09 12.006 3.31 12.118 2.45 12. 248 3.07 11.072 3.43 ] 1.205 3.20 12.008 3.08 12.120 3.46 12.250 2.49 11.076 2.92 ] 1.207 3.65 12.010 3.13 12.122 3.43 12.252 2.33 11.080 2.45 ] 1.209 3.06 12.012 3.17 12.124 3.17 12. 254 3.30 11.084 2.70 ] 1.211 3.39 12.014 3.28 12.126 3.47 12.256 3.26 11.088 3.19 ] 1.213 2.87 12.016 3.17 12.128 3.30 12.258 3.26 11. 094 3.61 ] 1.215 3.13 12.018 3.13 12.130 3.35 12.260 3.51 11.098 1.78 ] 1.217 2.90 12.020 3.12 12.132 3.38 12.262 2.98 11.102 2.72 ] 1.219 3.36 12. 022 3.43 12.134 3.29 12.264 3.38 11.106 1.36 ] 1.221 2.92 12.024 3.11 12.136 3.22 12.265 3.27 11.110 2.95 ] 1.223 3.71 12.026 3.30 12.138 3.38 12.268 3.35 11.114 3.35 ] 1.226 3.05 12.028 3.44 12.140 3.00 12.270 3.36 11.118 4.65 ] 1.228 3.29 12.030 3.44 12.142 3.42 12.272 3.12 11.120 3.68 ] 1.234 3.65 12.032 3.32 12.144 3.20 12.274 3.28 11.124 3.67 ] 1.238 3.41 12.033 3.21 12.146 4.36 12.276 3.34 11.128 2.85 ] 1.242 3.77 12.035 3.35 12.148 3.21 12.278 3.00 11.130 3.80 ] 1.246 3.01 12.037 3.20 12.150 3.14 12.280 3.39 11.132 3.37 ] 1.250 2.77 12.039 3.47 12.152 3.17 12.282 3.58 11.134 3.22 ] 1.254 2.51 12.041 3.42 12.154 3.27 12.284 3.41 11.136 3.24 ] 1.258 2.86 12.043 3.33 12.156 3.28 11.138 3.38 ] 1.262 3.23 12.045 3.35 12.158 3.22 13.001 2.26 11.140 2.77 ] 1.266 2.91 12.047 3.42 12.160 3.49 13.003 2.45 11.142 3.35 ] 1.270 3.69 12.049 3.39 12.162 3.21 13.005 1.42 11.146 3.25 1 1.278 3.09 12.051 3.31 12.164 2.98 13.007 2.42 11.148 2.54 ] 1.282 3.99 12.053 3.27 12.184 3.22 13.009 2.56 11.150 3.45 ] 1.285 3.20 12.055 2.84 12.186 3.22 13.011 3.68 11.152 2.59 ] 1.287 3.45 12.057 3.22 12.188 3.35 13.013 2.29 11.154 3.40 ] 1.289 3.12 12.059 3.41 12.190 3.39 13.015 2.76 76 AHLSTROM: FISH LARVAE IN EASTERN TROPICAL PACIFIC Appendix Table 7. — Standardized haul factors (SHF) : These factors are used to adjust original counts of larvae to the comparable standard of numbers of larve in 10 m' of water strained per meter of depth fished. — Continued. Station SHF Station SHF Station SHF Station SHF Station SHF 13.017 2.16 13.119 2.67 13.249 3.46 14.047 4.10 14. 203 3.15 13.019 1.88 13.121 3.14 13.251 3.46 14. 051 2.93 14. 209 3.23 13.021 2. 12 13.123 3.06 13.253 3.13 14. 055 3.77 14.213 3.26 13.022 2.72 13.125 3.50 13.255 3.58 14. 060 3.58 14. 218 2.87 13.028 1.53 13.127 3.30 13.257 3.68 14. 066 3.81 14.220 3.42 13.030 2.50 13.129 4.01 13.259 3.42 14. 069 3.65 14. 222 3.64 13.032 3.05 13.131 3.64 13.261 1.85 14.076 3.61 14. 224 3.77 13.034 3.21 13.133 3.84 13.263 3.49 14. 078 3.64 14. 228 3.87 13.036 2.34 13.135 2.51 13.265 3.29 14. 081 3.39 14. 230 2.96 13.038 2.25 13.137 2.58 13.266 3.31 14.084 3.86 14. 232 2.70 13.040 2.85 13.139 3.57 13.268 3.47 14.086 3.95 14.234 0.72 13. 042 2.74 13.141 3.36 13.270 3.30 14. 088 3.54 14. 236 2.96 13. 044 2.58 13.143 3.23 13.272 3.06 14. 091 3.08 14. 240 3.43 13. 046 3.08 13.145 3.49 13.274 3.73 14.095 3.87 14. 243 3.55 13. 048 2.71 13.147 3.58 13.276 3.54 14.099 3.70 14. 247 3.52 13.050 3.02 13.149 3.56 13.278 3.16 14.103 3.57 14.251 3.49 13.052 2.91 13.151 3.11 13.280 3.48 14.106 3.68 14.255 3.64 13.054 3.07 13.153 3.25 13.282 3.37 14.110 3.55 14.259 3.54 13.056 2.87 13.155 3.34 13.284 3.36 14.112 3.66 14.263 3.68 13.058 2.75 13.157 3.40 13.318 3.17 14.114 4.84 14.267 3.04 13.060 3.62 13.159 3.00 13.320 2.93 14.115 3.24 14.276 3.47 13. 062 3.15 13.161 3.30 13.322 3.22 14.117 4.29 14. 280 3.56 13.064 2.76 13.163 2.70 13.324 3.12 14.118 4.03 14. 283 3.60 13.065 2.81 13.165 3.22 13.326 3.05 14.120 3.76 14.287 3.53 13.067 2.67 13.167 3.64 13.328 3.15 14.122 3.78 14. 291 3.11 13.069 2.12 13.169 3.25 13.330 3.03 14.123 3.51 14.295 2.28 13. 071 2.61 13.171 3.12 13.332 3.13 14.124 3.38 14.300 3.58 13.073 3.11 13.173 2.80 13.334 2.85 14.126 3.69 14.303 3.48 13.075 3.42 13.175 2.71 13.338 3.02 14.127 3.89 14.306 3.29 13.077 2.72 13.179 2.46 13.340 3.00 14.128 3.66 14.310 2.85 13.079 2.53 13.183 3.39 13.342 3.03 14.130 3.62 14.314 3.60 13. 081 2.75 13.187 3.31 14.131 3.56 14.318 3.51 13.083 3.06 13.191 3.53 14.001 0.99 14.132 3.56 14.323 3.15 13.085 4.11 13.195 3.02 14. 006 2.94 14.134 3.67 14.326 1.51 13.087 2.87 13.199 2.77 14. 008 3.56 14.136 3.47 14.330 3.49 13. 089 2.65 13.203 2.60 14.010 5.83 14.138 3.83 13.091 2.97 13.207 3.31 14.012 3.50 14.142 3.69 13.093 2.87 13.211 3.01 14.014 3.51 14.146 3.75 13.095 2.81 13.215 2.97 14.016 3.28 14.150 3.60 13.097 3.02 13.219 2.44 14.017 4.19 14.154 4.24 13.099 2.64 13.223 3.01 14.018 3.13 14.158 2.45 13.101 2.75 13.227 3.32 14.020 2.89 14.164 1.01 13.103 2.77 13.231 2.42 14.022 3.45 14.172 3.55 13.105 2.77 13.235 3.05 14.024 3.55 14.174 3.57 13.107 2.76 13.237 3.56 14.027 3.55 14.177 3.88 13.109 2.90 13.239 3.51 14.029 2.63 14.183 3.94 13.111 2.88 13.241 3.55 14. 031 2.03 14.188 2.15 13.113 2.85 13.243 3.42 14.033 5.05 14.194 1.57 13.115 3.46 13.245 2.98 14. 040 3.65 14.195 1.39 13.117 2.99 13.247 3.27 14.043 3.53 14.199 1.54 77 SIZE STRUCTURE AND GROWTH RATE OF Euphausia pacifica OFF THE OREGON COAST' Michael C. Smiles, Jr.^ and William G. Pearcy' ABSTRACT Euphaiisia pacifica (Hansen) oflf Oregon has a maximum life expectancy of about 1 year. During this time it grows rapidly to a length of 22-24 mm. Furcilia larvae were found throughout the year but were most abundant during the autumn months. The population density and the proportion of juve- niles was higher within 25 miles of the coast than in offshore oceanic waters. Growth rates off Oregon are about twice those previously reported for this species from other re- gions. Spawning also appears to be later in the year. All these features may be explained by the high primary production which is extended throughout the summer by coastal upwelling and by the lack of wide seasonal fluctuations of water temperatures along the Oregon coast. Euphausia pacifica is one of the most abundant euphausiids in the North Pacific Ocean. Dense populations are found in Subarctic and Transi- tional waters (Brinton, 1962a; Ponomareva, 1963) and off the Oregon coast (Hebard, 1966; Osterberg, Pearcy, and Kujala, 1964 ; Pearcy and Osterberg, 1967). Euphausiids are important food for many marine carnivores (see Mauchline and Fisher, 1969, and Ponomareva, 1963, for reviews) , and Euphausia pacifica is no exception. It is preyed upon by salmon (Ito, 1964), baleen whales (Ne- moto, 1957, 1959; Osterberg et al, 1964), her- ring (Ponomareva, 1963), sardine and mack- erel (Nakai et al, 1957, as cited by Ponomareva, 1963; Komaki,1967),rockfish ( Pereyra, Pearcy, and Carvey, 1969), pasiphaeid and sergestid shrimp (Renfro and Pearcy, 1966), pandalid shrimp (Pearcy, 1970), and myctophid fishes (Tyler, 1970). Studies on the growth of several species of euphausiids are reviewed in the monograph by Mauchline and Fisher (1969). Data on the ' This research was supported by the National Science Foundation (GB-5494) and the Atomic Energy Com- mission (AT (45-1) -1750; RLO 1750-50). ° Formerly, Department of Oceanography, Oregon State University; present address: Biology Depart- ment, State University of New York, Farmingdale, N.Y. 11735. ' Department of Oceanography, Oregon State Uni- versity, Corvallis, Oreg. 97331. growth and life history of E. pacifica are lim- ited. Nemoto (1957) presented some growth data for E. pacifica from the Japanese-Aleutian area. Ponomareva (1963), in her study on the distribution and ecology of euphausiids of the North Pacific, estimated the growth of E. po/- cifica from plankton samples collected during the winter and spring. Lasker (1966) deter- mined the growth of E. pacifica reared in the laboratory. Preliminary growth rates of E. pa- cifica based on some of our data were also pre- sented by Small (1967). Because growth rates are needed to under- stand the ecology and energetics of a species, we undertook this study on the abundance, size structure, and growth rate of E. pacifica off Oregon. COLLECTION METHODS We made a total of 174 collections using 1-m mouth diameter plankton nets between June 1963 and July 1967 at stations located 15, 25, 45, and 65 miles off Newport, Oreg. In addition, 25 collections were obtained from stations 85-285 miles off Newport. These provided samples of E. pacifica for all seasons of the year over a 4-year period. Nets had 0.57 1-mm mesh open- ings and were used with a flowmeter placed in Manuscript received September 1970. FISHERY BULLETIN: VOL. 69, NO. I, 1971. 79 FISHERY BULLETIN: VOL. 69. NO. 1 the mouth to measure the amount of water filt- ered. The first 20 samples were from oblique tows, and the other 154 were from vertical tows. This change to vertical tows was made to ensure equal sampling at all depths throughout a tow. Com- parison of the catches of several oblique and vertical tows taken during the same night indi- cated little difference in the number and size of E. pacifica per unit volume filtei'ed. Because euphausiids may avoid nets in the daytime, all tows were taken during nighttime when visual avoidance would be minimal (Brint- on, 1967) . This is also a period when E. pacifica presumably has migrated into the upper 100 m of the water column. E. pacifica captured in several 6-ft Isaacs-Kidd midwater trawls were measured to see if large eui:)hausiids that were possibly avoiding the small vertical meter net could be captured. There was no indication that the maximum size of trawl-caught was larger than meter net-caught euphausiids. The maximum depth of our tows was usually 200 m. Because Ponomareva (1963) suggested that E. pacifica adults inhabit the 200-500-m layer in their second winter and no longer mi- grate daily to the surface, tows were taken to 1000 m with both the midwater trawls and vertical meter nets. These deeper tows, how- ever, did not contain any larger animals. Twelve vertical meter net samples from de])ths of 200 m or 1000 m to the surface did not show appre- ciable differences in size structure. Therefore, we assumed that a representative sample of the E. pacifica population was caught in the upiier 200 m at night. The entire plankton sample was preserved at sea in neutralized 10 'r Formalin. In the lab- oratory ashore, all euphausiids were removed from each sample unless the number of euphau- siids was large (more than 200 individuals). In such cases the samj^le was usually divided in half with a Folsom plankton splitter (Mc- Ewen, Johnson, and Folsom, 1954), and euphau- siids were sorted from only one-half the sample. Males and females were not differentiated. The length of each individual E. pacifica was measured to the nearest 0.1 mm from behind the eye to the posterior margin of the carapace, and each animal was then assigned to a 0.3-mm size-group. Total lengths (from the posterior of the eye to the tip of the telson) were also measured from randomly selected individuals of various lengths to enable comparisons of our data with those of others. A least squares fit of 146 comparisons gave the equation: Y = 2.54 X + 0.66 where Y = total length and X = carapace length. The variance was 248.19. Our measure- ments are all given as total lengths. RESULTS RECRUITMENT AND ABUNDANCE Although larval E. pacifica occurred during almost all months of the year, definite trends in abundance were evident over the 4-year per- iod ( Fig. 1 ) . Larvae were usually most abun- dant between October and December. During some years recruitment began as early as June and was also prominent in the summer months. No major concentrations of larvae were found during winter or spring. These larval forms of E. pacifica were f urcilia of about 7 mm or less, agreeing with Boden's (1950) size measurements and description of E. pacifica furcilia. Furcilia are found 16-18 days after spawning, usually within the upper 100 m of the water column (Ponomareva, 1963; Brint- on, 1967). Catch curves (Fig. 2) show the average num- ber of different size-groups of E. pacifica col- lected during the entire study. All sizes of E. imcifica were much more abundant i)er m^ in- shore over the continental shelf than in oceanic offshore waters. Individuals larger than 15 mm were rare at station 65 miles or farther offshore. Our finding that larvae were less abundant at offshore than inshore stations agrees with Brinton (1962b), who also noted that E. pa- cifica was more abundant inshore than oflFshore of California. Thus, despite the wide oceanic distribution of E. pacifica, the density of near- 80 SMILES and PEARCV : GROWTH RATE OF Eufhauna farifia 4000 3000 2000 1000 O 3000- 5 2000- (t 1000 g 3000 2000 1000 1000 I I I I I I I I I I I I I I I I I NH-15 I I I I I I I I I I I I I I I I I I I I I I I H I I I I I I I 10 o o oi— I oHo OOP OO P SlSL Us) 13.900 NH-25 o|— 10 0_0 NH-45 X\ r— lO I — I Q I — IQ Q □ Q .J3. TO Q^ 27000 _Q ^-~0 L. n Ql IQ 0. Or- lO O- n^ 1963 1964 oelUl |io| |i2| loil |04| ioeTloal fio] |i2 |o2| M W H MoMi^ lo^lW W M lio| jiF |oi| H M 1965 pa] [iol [IF |o2| |o4| 1966 1967 Figure 1. — Number of furcilia of E. pacifica collected at four stations off Newport, Oregon (NH-15, 25, 45, 65) during 1963-67. "0" indicates no sample taken for that month. • INSHORE {NH-15, NH-25) ALL STATIONS ▲ OFFSHORE (NH-65. NH-> 65) TOTAL LENGTH (mm) Figure 2. — Catch curves : the logarithm of the average number of various sizes of E. pacifica caught per lO'^ m'^ for all samples during the study. shore populations may be considerably higher than offshore populations in the same region. Although inshore tows were generally made only to 50 m and 130 m at the 15- and 25-mile stations respectively because of depth of water, euphausiid abundance at these stations was ap- proximately 10 times greater than at offshore stations. This difference is too great to be ex- plained by the differences in sampling depths even assuming that all euphausiids were con- centrated in the upper 50 m at night. GROWTH RATE The extended spawning season and variability of catches of E. pacifica made interpretation of growth difficult. Three related methods, all based on progressions of size-frequency histo- grams, generally gave similar growth rates (Table 1) and led to the same conclusion: E. pacifica lives for a period of about 1 year and attains a maximum size of about 22-24 mm total length. We tenuously assumed for all these analyses that we sampled the same population, or populations with similar age structures and growth rates. Two illustrations of growth based on monthly 81 FISHERY BULLETIN; VOL. 69. NO. 1 Table 1. — Summary of average growth rate estimated from the progression of modes or means (see Figs. 3 and 4). Year class Recruitmenf month Number monHis followed Growth rotes Modes (Fig- 3 for 1965 and 1966 year classes) Modes (Fig. 4) Mm/month 1963 09 10 1.6 1.9 1.6 1964 10 9 2.0 2.0 1.9 1965 10 8 2.1 2.2 2.0 1966 11 5 2.9 2.S 2.4 1967 03 3 2.6 2.5 2.5 size-fre(iuency histograms of all stations com- bined (Fig. 3) illustrate the increasing modal lengths between December and June for the 1965 and 1966 year classes. Recruitment of small E. pacifica is also obvious during the spring of 1966 and 1967 and also shows a shift in modes with time. The 1963 and 1964 year classes (not shown here) showed similar trends. A modified histogram plot (Fig. 4) was used to show the data for all 4 years and all 4 stations together. The advantage of this method is that one can follow the main modes of different sizes throughout the 4-year period. A disadvantage is that these plots are distorted by the arbitrary constraints that (1) at least 50 individuals per 103 m3 of water within one size-group had to be present for plotting and (2) concentrations above 5000/103 m3 were plotted only as 5000/ 103 m3. All of the years represented in Figure 4 show some similarity. The main recruitment pulses are in the fall and summer, and the max- imum size attained is approximately 22-24 mm length. After about 1 year, late in the second summer or fall, these large individuals dis- appeared from our collections. Interestingly, many of the modes that were composed of small euphausiids during the spring and early summer disappeared or were undiscernible by the fall. Either these individuals were subjected to high- er mortality than the fall recruits or were trans- ported out of the area. Apparently they made no major contribution to the local adult popu- lation. Average lengths of size modes were also calculated for each collection using the com- puter techniques described by Hasselblad (1966). The means were generally close to the values for the modal lengths of various col- lections shown in Figures 3 and 4 and, therefore, are not illustrated here but are given in Table 1. Our estimates of the growth of E. pacifica by all these methods are summarized in Table 1. As expected, estimates are similar for the same year classes. Growth varied from 1.6 to 2.9 mm per month among year classes, averaging about 2.0 mm per month. Growth rates were fastest for young stages. Year-classes 1963 and 1964 had slower average rates (1.6 and 2.0 mm/ month) and were calculated over a longer period. Year-classes 1966 and 1967, on the other hand, were represented for the shortest periods of time and had the fastest average rates (2.9 and 2.6 mm month) . This deceleration of growth at the larger sizes is also apparent in Figure 3 where the growth rate from January to March 1966 was about 3.2 mm/month, while from March to June it was about 2.0 mm/month. Our estimates are biased in several ways. They favored the recruitment pulses of the fall because the smaller modes of young that ap- peared earlier (June through September) did not comprise a good series of modal sequences. Moreover, the modes and means of the smaller sizes of E. pacifica are probably slightly over- estimated since catch curves (Fig. 2) indicate escapement from our nets of individuals below 6 mm. This may cause an underestimation of growth rates. DISCUSSION Generalized growth curves of E. pacifica for three regions of the North Pacific are con- trasted in Figure 5. On the basis of bimodal size-frequency distributions of winter and spring samples, Ponomai-eva (1963) concluded that E. pacifica lives for a period of 2 years. She found predominantly 8 and 14-15 mm indi- viduals in the winter and 12-13 mm (her 1- yearolds) and 19 mm (2-year olds) in the spring. Off Oregon not only were 12-13 mm individuals rare or absent in sirring samples, but also 13-14 mm individuals, the size that Ponomareva would expect to find in the summer and fall, were ab- sent. Moreover, our data, unlike Ponomareva's, show no large seasonal fluctuations of growth with retarded growth of the 13-14 mm sizes 82 SMILES and PEARCY: GROWTH RATE OF Euphamia padfica 3S00- 20CX)- 1000- 400- 100- 10- 0-^ I I I I I I I I I I I I I I I I I OCTOBER 1965 _ \m\^ 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 NOVEMBER 1966 mn 3500- NOVEMBER 1965 n rfT}n->-. r^ rn 1^ - J~ '-. DECEMBER 1966 _ 3500- Id DECEMBER 1965 _ _ \im. 3500- I § I JANUARY 1966 _ _ rniiiirrrh E im^ FEBRUARY 1967 _ ~h-h-r-i 3500- 0- 3500- FEBRUARY 1966 rfTTrmrrm MARCH 1967 "hrhm rrTil il>n 3500- MARCH 1966 APRIL 1967 TffHi m I ITTti n F 0- 3500- APRIL 1966 On MAY 1967 THth F =HTlTTTT^>rTTTnn JUNE 1966 rm ii nmTn — — _ — — Cg(\J(sj I I I I I i I I I T IT tf>O)Or>Jrnio^<0ooO0)OO (\J (NJ OJ TOTAL LENGTH (mm) Figure 3. — Size frequency distributions of E. pacifica from all stations for the 1965 year class (left) and the 1966 year class (right). 83 FISHERY BULLETIN: VOL. 69, NO. 1 361 |0e| 1 10 1 |I2| b2| M |06| |08| 1 10 1 ||2| |02| |04| |06| 1963 ' 1964 ' 1965 1966 Toil lo4l bel 1967 Figure 4. — Size frequency histograms for all stations, 1963-67. Dashed lines are an estimate of average growth of individual year classes. "0" indicates no samples for that month. 22 20 ^'^ § 12 -J 8 6 2 S OUR RESULTS OUR RESULTS >'l I I I I I.I I I I I I M I I I I I I I I I I 6 8 10 12 2 4 6 8 10 12 2 4 6 8 10 I MONTHS I Figure 5. — Comparison of generalized growth curves of E. pacifica. in the summer and fall. Nemoto (1957 and per- sonal communication) believes that E. pacifica grows rapidly, reaching a length of 17-18 mm after 1 year. Many individuals spawn after 1 year and then may continue to live for another year, reaching a maximum of 22 mm after 2 years. We find no convincing evidence, how- ever, for continuation of large adults through a second year. Large euphausiids disappeared from our samples by the winter (Fig. 4). Thus our results indicate a faster growth rate and shorter life cycle than those of Ponomareva and Nemoto for the northwestern Pacific but a similar maximum size. Our growth rates off Oregon averaged 0.065 mm/day for the entire life span, about twice those for the other field studies of E. pacifica. Maximum rates for rap- idly growing juveniles were 0.095 mm /day. These rates are higher than Lasker's (1966) maximum rates for juvenile E. pacifica reared in the laboratory, suggesting that growth in nature may exceed "optimal" conditions in the laboratory. Although our estimates of the growth of E. pacifica are higher than previousl.v reported, they approximate the estimates for .sevei'a! other species of euphausiids. A length of about 22 mm after 1 year was also found by Mauchline ( 1966) for Thysanoessa raschii; by Ruud (1936), Mauchline (1960), and Einarsson (1945) for Meganyctiphanes norvegica; by Einarsson (1945) for Thysanopoda aciitifrons; by Ruud 84 SMILES and PEARC\- : GROWTH RATE OF Eupham,a pa„fica (1932), Bargmann (1945), and Marr (1962) for Euphausia superba; and by Baker (1959) for Enphau^ia triacantha. Most of these species have a maximum life expectancy of 2 years, reproduce each year, and grow slowly during the winter. Other species are known to have a life expectancy of 1 year (Mauchline and Fisher, 1969). Development, growth, and sexual maturity of the same species of euphausiid are known to vary among geographic iropulations (Einarsson, 1945; Nemoto, 1957; Ponomareva, 1963; Mauchline and Fisher, 1969). Mauchline and Fisher (1969) stress that this variability is probably directly related to differences in food and temperature. Hence, the rapid growth of E. pacifica off Oregon may be related to the high productivity of the region and the lack of large seasonal temperature fluctuations in nearshore waters. Small, Curl, and Glooschenko' report high values for primary productivity in the coastal waters off Oregon. Curl and Small' found that standing stocks of chlorophyll-n averaged high- est inshore and steadily decreased offshore. High production and stocks persist through the summer, the upwelling season, in inshore waters, whereas offshore waters have a tyijical summer productivity minimum (Anderson, 1964). Note that those seasonal and inshore-offshore gradi- ents in phytoplankton are correlated in time and place with the spawning of E. pacifica off Ore- gon, mostly inshore and protracted over the summer and fall months. Ponomareva (196?.) believes that phytoplankton is not only im- portant as food for euphausiid larvae, but also may be necessary in the diet for development of reproductive products of E. pacifica. Water temperatures along the Oregon coast are fairly uniform throughout the year and lack the extremes found along the eastern coasts of continents at similar latitudes. Advection of cool water to the surface (upwelling) during the summer and warm water toward shore dur- * L. F. Small, H. Curl, Jr., and W. A. Glooschenko. Seasonal primary production in a region of upwelling. III. Effects of solar radiation and upwelling on daily production. Unpublished MS. ^ H. Curl, Jr., and L. F. Small. MS. ing the winter moderates the usual seasonal variations. Pattullo, Burt, and Kulm (1969) observed that the seasonal range of heat con- tent was twice as large offshore as inshore (with- in 65 miles) of the Oregon coast. The absence of severe winter temperatures may help to ex- plain the rapid growth of E. pacifica through- out the year off Oregon. Conversely the slow and seasonally variable growth of E. pacifica found by Ponomareva (1963) was in the Far Eastern Seas of Asia where temperatures are often lower and where thermal variations are greater. The fact that E. pacifica is the only widespread euphausiid that spawns in the sum- mer, when the phytoplankton bloom was almost over, indicates that this boreal species may be poorly adapted to the cold marginal Far Eastern Seas (Ponomareva, 1963). The main pulses of larvae, hence spawning, of E. pacifica were in the fall, and not in the spring and summer as found by Ponomareva (1963), Nemoto (1957) off Japan, and Barham (1957) in Monterey Bay, Calif. Brinton (per- sonal communication) notes larval recruitment throughout the year off Southern California. The later spawning off Oregon, like the rapid growth, may again be related to the prolonged production cycle caused by upwelling off Oregon and the moderate fall and winter water temper- atures. ACKNOWLEDGMENTS We are grateful to J. Mauchline for his sug- gestions and to T. Nemoto for providing his growth curve for E. pacifica. LITERATURE CITED Anderson, George C. 1964. The seasonal and geographic distribution of primary productivity off the Washington and Oregon coasts. Limnol. Oceanogr. 9(3) : 284-302. Baker, A. de C. 1959. The distribution and life history of Euphaus- ia triacantha Holt and Tatersall. Discovery Rep 29: 309-340. Bargmann, Helens E. 194.5. The development and life-history of ado- lescent and adult krill, Euphausia superba. Dis- covery Rep. 23: 10,3-176. 85 FISHERY BULLETIN: VOL. 69. NO. 1 Barham, Eric George. 1957. The ecology of sonic scattering layers in the Monterey Bay area, California. Ph.D. Thesis, Stanford Univ. 192 p. Univ. Microfilms, Ann Arbor, Mich. Publ. 21, 564. BoDEN, Brian P. 1950. The post-naupliar stages of the crustacean Euphausia pacifica. Trans. Amer. Microsc. Sec. 69(4) : 373-386. Brinton, Edward. 1962a. The distribution of Pacific euphausiids. Bull. Scripps Inst. Oceanogr. Univ. Calif. 8(12) : 51-270. 1962b. Variable factors affecting the apparent range and estimated concentrations of euphausiids in the North Pacific. Pac. Sci. 16(4) : 374-408. 1967. Vertical migration and avoidance capability of euphausiids in the California Current. Limnol. Oceanogr. 12(3): 451-483. EiNARSsoN, Hermann. 1945. Euphausiacea. 1. North Atlantic species. Dana Rep. Carlsberg Found. 27, 1-185. Hasselblad, Victor. 1966. Estimation of parameters for a mixture of normal distributions. Technometrics 8(8) : 431- 444. Hebard, J. F. 1966. Distribution of Euphausiacea and Copepoda off Oregon in relation to oceanic conditions. Ph.D. Thesis, Oregon State Univ., Corvallis. 85 p. Ito, Jun. 1964. Food and feeding habit of Pacific salmon (genus Oncorhynchits) in their oceanic life. Bull. Hokkaido Reg. Fish. Lab. 29: 85-97. Komaki, Yuzo. 1967. On the surface swarming of euphausiid crustaceans. Pac. Sci. 21(4): 433-448. Lasker, Reuben. 1966. Feeding, growth, respiration, and carbon utilization of a euphausiid crustacean. J. Fish. Res. Bd. Can. 23(9) : 1291-1317. Marr, James. 1962. The natural history and geography of the Antarctic krill {Euphausia superba Dana). Dis- covery Rep. 32: 33-464. Mauchline, J. 1960. The biology of the euphausiid crustacean, Meganyctiphaves norvegica (M. Sars). Proc. Roy. Soc. Edinburgh, Sect. B. (Biol.) 67: 141-179. 1966. The biology of Thysanoesaa raschii (M. Sars), with a comparison of its diet with that of Meganyctiphanes norvegica (M. Sars). 7n Harold Barnes (editor), Some contemporary studies in marine science, p. 493-510. George Allen and Unwin Ltd., London. Mauchline, John, and Leonard R. Fisher. 1969. The biology of euphausiids. In Frederick S. Russell and Maurice Yonge (editors), Advances in marine biology. Vol. 7, 454 p. McEwEN, G. F., M. W. Johnson, and Th. R. Folsom. 1954. A statistical analysis of performance of the Folsom plankton sample splitter, based on test observations. Arch. Meteorol. Geophys. Bioklima- tol., Ser. A. 7: 502-527. Nemoto, Takahisa. 1957. Foods of baleen whales in the northern Pa- cific. Sci. Rep. Whales Res. Inst. 12: 33-90. 1959. Food of baleen whales with reference to whale movements. Sci. Rep. Whales Res. Inst. 14: 149-290. Osterberg, Charles, William Pearcy, and Norman Kujala. 1964. Gamma emitters in a fin whale. Nature (London) 204(4962): 1006-1007. Pattullo, June G., Wayne V. Burt, and Sally A. KULM. 1969. Oceanic heat content off Oregon: Its vari- ations and their causes. Limnol. Oceanogr. 14 (2) : 279-287. Pearcy, William G. 1970. Vertical migration of the ocean shrimp, Pa7idalus jordani: A feeding and dispersal mech- anism. Calif. Fish Game 56(2): 125-129. Pearcy, William G., and Charles L. Osterberg. 1967. Depth, diel, seasonal, and geographic vari- ations in zinc-65 of niidwater animals of Oregon. Int. J. Oceanol. Limnol. 1(2): 103-116. Pereyra, Walter T., William G. Pearcy, and Forrest E. Carxtiy', Jr. 1969. Sebastodes flai'idus, a shelf rockfish feeding on mesopelagic fauna, with consideration of the ecological implications. J. Fish. Res. Bd. Can. 26(8) : 2211-2215. Ponomareva, Larisa Natal'evna. 1963. Euphausiids of the North Pacific, their dis- tribution and ecology. Akad. Nauk SSSR Inst. Okeanol. (Translated by Israel Program for Sci- entific Translations, Jerusalem 1966, IPST cat- alog no. 1368, 154 p.) Renfro, William C, and William G. Pearcy. 1966. Food and feeding apparatus of two pelagic shrimps. J. Fish. Res. Bd. Can. 23(12): 1971- 1975. Ruur, John T. 1932. On the biology of southern Euphausiidae. Hvalradets Skr. 2. 105 p. 1936. Euphausiacea. Rep. Dan. Oceanogr. Exped. 1908-1910 Mediter. Adjacent Seas 2D6(Biol.), 86 p. Small, Lawrence F. 1967. Energy flow in Euphausia pacifica. Nature (London) 215(5400): 515-516. Tyi-er, H. R., Jr. 1970. The feeding habits of three species of lant- emfishes (Myctophidae) off Central Oregon. Master's Thesis, Oregon State Univ., Corvallis. 64 p. 86 ESTIMATING PHYTOPLANKTON PRODUCTION FROM AMMONIUM AND CHLOROPHYLL CONCENTRATIONS IN NUTRIENT-POOR WATER OF THE EASTERN TROPICAL PACIFIC OCEAN"° William H. Thomas" and Robert W. Owen, Jr.* ABSTRACT Previous work has shown that nitrogen is the limiting nutrient in poor (nitrate-free) water in the eastern tropical Pacific Ocean and has suggested that ammonium is the principal nitrogen source for phytoplankton in this water. Enrichment and uptake experiments with various concentrations of ammonium have provided values for the half-saturation constant, Kg, and the maximum growth rate, /i^ax' which can be used to calculate actual growth rates with the hyperbolic model relating growth rate to limiting nutrient concentration. At two stations, growth rates calculated from ammonium con- centration agreed well with those calculated from chlorophyll and 14c production, and the hyperbolic equation could be combined with that using production and chlorophyll to calculate production alone. In this paper calculated production rates are compared with those observed from 14c uptake mea- surements for a number of EASTROPAC cruises. The regression between calculated production and observed production is highly significant and the slope is close to 1.0, indicating reasonable agreement, particularly when all of the errors in the calculation, especially in Ks, are considered. The results suggest rather close control of phytoplankton production by the limiting nutrient, ammonium, in these near-surface, nutrient-poor waters. This paper describes how concentrations of a limiting nutrient in sea water and some mea- sure of the standing crop of phytoplankton can be used to estimate phytoplankton production. Estimated production is compared with observed i'*C production, and the two sets of values are shown to agree reasonably well when all the errors in the estimation are considered. The EASTROPAC Expedition series has de- lineated particularly well areas that are rich in nutrients and that are nutrient-poor in the eastern tropical Pacific Ocean. Rich areas in- ' Contribution from the Scripps Institution of Ocean- ography. " This work was part of the research of the STOR (Scripps Tuna Oceanography Research) Program. It is also a result of the EASTROPAC Expedition, a co- operative study of the biological, chemical, and physical oceanography of the eastern tropical Pacific Ocean. The work was supported by National Science Foundation Grant No. GB-8618 to the senior author and by contracts #14-17-0007-963 and #14-17-0007-989 between the Bu- reau of Commercial Fisheries (now the National Marine Fisheries Service) and the Institute of Marine Resources. ' Institute of Marine Resources^ Scripps Institution of Oceanography, University of California, San Diego, La Jolla, Calif. 92037. * National Marine Fisheries Service Fishery-Ocean- ography Center, La Jolla, Calif. 92087. Manuscript received September 1970. FISHERY BULLETIN: VOL 69, NO. I, 1971. elude the Peru Current, the Costa Rica Dome, and an area of equatorial upwelling extending across the EASTROPAC area (from the Amer- ican coast to long 119° W). Poor areas lie to the north and south of the equatorial upwelling zone and to the west of the Peru Current and Costa Rica Dome. Rich and poor near-surface waters were mapped in previous papers (Thom- as, 1969, 1970b) and will be shown in detail in the EASTROPAC Atlas (Thomas, unpub- lished data) . Nutrient values for rich and poor water are also given in Table 1 of Thomas (1970a). Corresponding areal and seasonal changes in the phytoplankton production in this region have been observed and attributed in part to mecha- nisms of nutrient supply (Owen and Zeitzschel, 1970). No accounting has been possible, how- ever, for the variations observed within the nutrient-poor surface layer of the region. Near-surface water in poor areas is especially low in nitrate-nitrogen; this nutrient is gener- ally not detectable (<0.1 /ng-at./liter). Ammo- nium-N is present in concentrations ranging up to 1 /ng-at./liter and organic nitrogen can reach 87 FISHERY BULLETIN: VOL. 69, NO. 1 concentrations of 17 /.ig-at. /liter, but this latter nitrogen source is probably not utilized by phy- toplankton (Thomas, Renger, and Dodson, in press). Prior to EASTROPAC (pre-1967) low ni- trate/phosphate ratios in tropical Pacific poor water suggested that nitrogen was a limiting nutrient although ratios were increased when ammonium was included along with nitrate, and it was suggested that this latter nutrient alle- viated N deficiency (Thomas, 1966). Recent EASTROPAC enrichment experi- ments provided direct evidence for N limitation. Phytoplankton growth occurred in experiments where nutrients were added singly to sea water samples only with N addition, and if N was de- leted from an otherwise complete enrichment, little or no growth resulted (Thomas, 1969, 1970b). The fact that photosynthetic assimi- lation ratios were only slightly (but signifi- cantly) decreased in poor water as compared with rich water testified further to the allevi- ation and control of deficiency by ammonium (Thomas, 1970a). Having established which nutrient is com- monly limiting, one can use a quantitative nu- trient requirement in an appropriate math- ematical model to estimate growth rates (pro- duction) from concentration of the limiting nu- trient. Recent work (Caperon, 1967; Dugdale, 1967) indicates that the best model is hyperbolic: (1) K, + S where /j. is the phytoplankton specific growth rate, Mj is the maximum rate which is un- limited by low nutrient concentration, S is a measured limiting nutrient concentration in sea water, and Kg is the "half-saturation constant" — a nutrient concentration that supports a rate equal to /:tma.x/2. This equation is equivalent to the Michaelis-Menton formulation for enzyme kinetics and was first applied to bacterial growth rates by Monod (1942). Many biological pro- cesses follow the hyperbolic model and since growth is the result of a series of coupled en- zymatic reactions, the hyperbolic model is the model of choice. A previous paper (Thomas, 1970b) provides information on /umax and Kg (for ammonium) from which /i can be calculated. To obtain these values we enriched samples of nutrient-poor Pa- cific sea water from a depth of 10 m with a com- plete mixture of non-nitrogenous nutrients to which various concentrations of ammonium were added. The samples were then incubated in natural light approximating the intensity that would be found at 10 m depth. Growth was es- timated by successive daily measurements of in vivo chlorophyll (Lorenzen, 1966) in each treatment, and rates integrated over a daily peri- od were calculated from the maximum increases in chlorophyll. These rates were plotted against ammonium concentrations to fit a hyperbolic model and values of A',, and /xmax were obtained from the plot. These values and their 95% con- fidence limits are given in Table 1 for two such experiments. Kg values can also be determined from uptake experiments since recent work has shown that A'., values for growth and uptake are equivalent (Eppley and Thomas, 1969). Also included in Table 1 are uptake Kg values obtained by Maclsaac and Dugdale (1969) for nutrient-poor tropical Pacific water. Their val- ues for Vniax. the maximum uptake rate, are not equivalent to /imax ^'id thus are not included Table 1. — Rate parameters for growth and uptake on ammonium in nutrient-poor tropical Pacific sea water. Cruise Station ilM) 95 percent limits ''max 95 percent limits (Doublings/day) EASTROPAC 76 007 1.68 ± 3.28 1.12 ± 0.83 Thomos (1970b) EASTROPAC 76 173 1.47 i: 0.91 1.22 ± 0.27 Thomas (1970b) Thompson 26 IS 0.10 -- - - Maclsoac and Dugdale (1969) Thompson 26 3« 0.5S - ~ ~ Maclsoac and Dugdale (1969) Te Vega 13 651.a 0.62 ~ — ~ Maclsaac and Dugdola (1969) Meon volues 0.88 1.17 95 % limits of mean 1.33 O.U 88 THOMAS and OWEN; ESTIMATING PHVTOPLANKTON PRODUCTION in Table 1. It will be noted that confidence lim- its for Ks values in given experiments are large as is the confidence limit for the mean of all five values which is used in subsequent calculations (see Results and Discussion). This can be at- tributed to lack of precision in measuring either growth or uptake; even in controlled experi- ments with laboratory cultures, A'., values are imprecise (Eppley, Rogers, and McCarthy, 1969; Eppley and Thomas, 1969). The integrated daily growth rate, fi, can also be calculated from ^^C production estimates and chlorophyll concentrations using the following equation: 3'.32 [log,o(/? • chl + Prod ) - logio(/? • chl)] ^ = 1 day (2) as has been done for laboratory cultures by Thomas (1964) and McAllister, Shah, and Strickland (1964). In this equation R is the carbon/chlorophyll ratio; R chl thus is the standing stock of phytoplankton carbon. The constant 3.32 converts logarithms to the base 10 to logarithms to the base 2 and allows /x. to be expressed as doublings of phytoplankton carbon per day. In the previous paper (Thomas, 1970b), ^ calculated from ammonium (equation 1) was compared with /j, calculated from l^c production and chlorophyll (equation 2) for the two EAS- TROPAC stations where Ksand /^max were de- termined from enrichment experiments. At station 76.007, /x calculated from ammonium was 0.385 doublings/day while that calculated from •^■^C uptake and chlorophyll was 0.365 doublings/ day. At station 76.173 both values were iden- tical — 0.276 doublings/day. For the calcula- tion we used an R value of 98, that found by Eppley (1968) for nitrate-free water off La Jolla. This excellent agreement suggested that we could set equation (1) equal to equation (2) and solve for production as a function of ammonium and chlorophyll using A's and fimax ^s constants. The new equation thus derived is /q\ Prod = chl • R antilog [^max L \3.32 3.32 Ks+ S 1 This expression allows a direct comparison cal- culated and measured ^'*C production (see Re- sults and Discussion). METHODS Methods for determining A's and ^ma.x were given previously (Thomas, 1970b; Maclsaac and Dugdale, 1969) — see also the previous sec- tion. Chlorophyll and production samples were taken from the depth of the 50 % light level, which was always in the upper mixed layer and varied from 9 to 16 m. This depth was determined by multiplying the depth at which the Secchi disc disappeared by 0.38. This factor employs the assumption that the Secchi disc disappears at 16 % of surface light in- tensity (Strickland, 1958). Chlorophyll was determined in these samples by filtration on glass fiber filters, followed by 90 % acetone extraction of the filters, and mea- surement of fluorescence of the extract ( Yentsch and Menzel, 1963; Holm-Hansen, Lorenzen, Holmes, and Strickland, 1965) using equations developed by Lorenzen (1966). Simulated in s'itw production was measured by adding 20 ^c Na^^'^COs solution to the samples (Steemann Nielsen, 1952) and incu- bating them in a tubular shipboard incubator space in which natural light intensity was at- tenuated to 50 % of that incident. Incubation was started at noon and continued until sunset at sea surface temperature. Following incuba- tion the samples were filtered through HA Mil- lipore®' filters and their radioactivity assayed ashore by G-M counting of the filters. The l^c solution was standardized by liquid scintillation counting and the efficiency of the G-M counter for these filters was determined by combusting some of these and measuring the evolved ^^C02 with an ionization chamber. Daily uptake was determined by multiplying the activity by 2; we also corrected for the isotope effect by mul- tiplying by 1.05. Darkened samples were incu- bated with illuminated samples and dark uptake was subtracted from light uptake. No cor- ° The use of trade names is merely to facilitate de- scriptions: no endorsement is implied. 89 FISHERY BULLETIN: VOL. 69, NO. I rections for respiration by phytoplankton were made. Ammonium was measured ashore in frozen samples from a depth of 10 m by the method of Richards and Kletsch (1964). Some labile amino-N which is probably available to phyto- plankton is measured along with ammonium by this method. RESULTS AND DISCUSSION For the comparison of calculated and mea- sured ^''C production, we have used samples from 10 m incubated at light intensities approx- imating those at 10 m to determine Ks and fimax. and actual ^^C values from the 50% light level. We did this so that light intensities would not be a factor in the comparison — that is, light was presumed to be at saturating intensities but not inhibitory, which would be the case if surface samples had been incubated in the growth experiments and compared with surface production. Ammonium was not determined at all pro- duction stations, and we selected those pro- duction values where data were available for / / / / / / - Calcu loted Prod. = 1.057 (Observed Prod.)^ / / ^~7 / 10 / / / y / ''' / / / ^ y / / / m / / • X / / / " / y • /^ 5 — • • • • • / / • // • • . // • '/ • * / • //• • . • • • • /^ • • • • • • // • • • /y *• A - • • • • — 1 — i — 1 — 1 , , , , 1 . OBSERVED '*C PRODUCTION {Mg C/m'/Day) 10 Figure 1. — Phytoplankton production calculated from ammonia and chlorophyll con- centrations at 10 m compared with simulated in situ ^^C production at the 50 7o light level in northerly nutrient-poor water in the eastern tropical Pacific Ocean. The dashed line is the regression that would be expected if agreement between the two sets of pro- duction values were perfect. 90 THOMAS and OWEN : ESTIMATING PHYTOPLANKTON PRODUCTION ammonium and where nitrate was undetectable. One hundred and five such production stations were available from 10 EASTROPAC cruises in this nutrient-poor water. Production calculated from equation 3 is com- pared with measured ^*C production in Figure 1. There is a highly significant (P<.01) rela- tionship between the two sets of values. The slope of the regression line is 1.057, which is very near to the value 1.0 which would be ex- pected if agreement were perfect. Nevertheless, there is a large amount of scatter in the values of Figure 1; that is, the calculation overesti- mates in some cases and underestimates in others. Table 2. — Errors in the calculation of production. Parameter Standard errors Reference Chlorophyll ± 12% Holmes, Schaefer, and Shimada (1958) R ± 17% Eppley (1968) ± 6% Table 1 (this paper) S ± 5% Richards and Kletsch (1964) K, ± 76% Table 1 (this paper) Total ± 79% 95% confidence limits ± 152% Errors in the values used in the calculation are given in Table 2. To figure total error these have been converted to variances and summed. The 95% confidence limit shows that any cal- culated production value can vary by ± 1.5 fold. Thus, one would expect quite a large scatter in Figure 1. Most of the error is in Ks. When only the Ks values of Thomas (1970b) are used the cal- culation generally underestimates the observed •''*C production. Use of the mean of the Ks values of Maclsaac and Dugdale (1969) results in an overestimation. Since there is no reason to doubt either set of Kg values, we have used the overall mean Kg from Table 1. In applying this method to any other nutrient-limited waters, it would be well to obtain several values of Kg so that the error due to lack of precision in measuring Kg can be recognized. Part of the scatter in Figure 1 may also be due to the fact that the parameter Kg is species — and temperature — dependent (Eppley, Ro- gers, and McCarthy, 1969) and that variations in species composition of the crop or slight var- iations in temperature may have affected the calculation. The parameters ^max and R are also probably dependent upon the species com- position of the crop and on temperature. Be- cause of these factors, which are unknown, it is perhaps surprising that the relationship be- tween calculated and observed production is so good when constant values of Kg, ^ma.x.and R are used. This evidence supports the hypothesis that phytoplankton production in the upper mixed layer is controlled by the limiting nutrient, ammonium, and shows that the hyperbolic model describes this control very well. In this latter connection it should be noted that if a linear model having a term "S/Smax" in equation 3 (where Smax is that concentration supporting a maximum growth rate and which has a value near 10.0 ^M from the data of Thomas, 1970b) is used rather than the term "S/ (Kg + S)," the calculation very much underestimates the ^^C production. The linear model was used previously by Riley (1963) and Steele (1958) but should now be considered obsolete in view of more recent work using the hyperbolic model. ACKNOWLEDGMENTS We appreciate the assistance of many persons in gathering these data. Ammonium analyses were performed by Mr. Edward Renger, and Mrs. Anne Dodson aided in the determination of /-max and Kg. Sampling and incubation for production measurements and determination of chlorophyll concentrations were carried out by the following: Messrs. Tapuni Mulitauaopele, Michael Kruse, David Justice, James McCarthy, Lawrence Klapow, David Judkins, Gerald John- son, Eric Forsbergh, and Jack Metoyer. Dr. Bernt Zeitzschel and Mr. Michael Kruse helped to process and edit the ^'*C and chlorophyll data. Most of these data were collected aboard the NMFS vessel David Starr Jordan and we appre- ciate the assistance of Capt. C. W. Forster and his crew. 91 FISHERY BULLETIN: VOL. 69. NO. 1 LITERATURE CITED Capeeon. John. 1967. Population growth in micro-organisms lim- ited by food supply. Ecology 48(5) : 715-722. DUGDALE, R. C. 1967. Nutrient limitation in the sea: Dynamics, identification, and significance. Limnol. Oceanogr. 12(4): 685-695. Eppley, Richard W. 1968. An incubation method for estimating the carbon content of phytoplankton in natural sam- ples. Limnol. Oceanogr. 13(4) : 574-582. Eppley, Richard W., and William H. Thomas. 1969. Comparison of half-saturation constants for growth and nitrate uptake of marine phytoplank- ton. J. Phycol. 5(4): 375-379. Eppley, Richard W., Jane N. Rogers, and James J. McCarthy. 1969. Half-saturation constants for uptake of ni- trate and ammonium by marine phytoplankton. Limnol. Oceanogr. 14(6): 912-920. Holmes, R. W., M. B. Schaefer, and B. M. Shimada. 1958. SCOPE measurements of productivity, chloro- phyll "a", and zooplankton volumes. In Robert W. Holmes, and other members of the Scripps Cooperative Oceanic Productivity Expedition, Physical, chemical, and biological oceanographic observations obtained on Expedition SCOPE in the eastern tropical Pacific, November-December 1956, p. 59-68. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 279. Holm-Hansen, Osmund, Carl J. Lorenzen, Robert W. Holmes, and John D. H. Strickland. 1965. Fluorometric determination of chlorophyll. J. Cons. Cons. Perma. Int. Explor. Mer 30(1): 3-15. Lorenzen, Carl J. 1966. A method for the continuous measurement of in vivo chlorophyll concentration. Deep-Sea Res. Oceanogr. Abstr. 13(2): 223-227. MACISAAC, J. J., AND R. C. DUGDALE. 1969. The kinetics of nitrate and ammonia uptake by natural populations of marine phytoplankton. Deep-Sea Res. Oceanogr. Abstr. 16(1) : 45-57. McAllister, C. D., N. Shah, and J. D. H. Strickland. 1964. Marine phytoplankton photosynthesis as a function of light intensity: A comparison of methods. J. Fish. Res. Bd. Can. 21(1) : 159-181. Monod, J. 1942. Recherches sur la croissance des cultures bacterienne. Hermann et Cie, Paris. Owen, R. W., and B. Zeitzschel. 1970. Phytoplankton production: seasonal change in the oceanic eastern tropical Pacific. Mar. Biol. 7(1) : 32-36. Richards, Francis A., and Richard A. Kletsch. 1964. The spectrophotometric determination of ammonia and labile amino compounds in fresh and sea water by oxidation to nitrite. In Yasuo Miyake and Tadashiro Koyama (editors). Ken Sugawara festival volume; recent researches in the fields of hydrosphere, atmosphere and nuclear geochemistry, p. 65-81. Maruzen Company, Ltd., Tokyo. Riley, G. A. 1963. Theory of food-chain relations in the ocean. In M. N. Hill (editor) , The sea. Vol. 2, p. 438-463. Interscience Publishers, New York. Steele, J. H. 1958. Plant production in the northern North Sea. Scot. Home Dep., Mar. Res. 7, 36 p. Steemann Nielsen, E. 1952. The use of radio-active carbon (C^*) for measuring organic production in the sea. J. Cons. Cons. Perma. Int. Explor. Mer 18(2): 117-140. Strickland, J. D. H. 1958. Solar radiation penetrating the ocean. A review of requirements, data and methods of measurement, with particular reference to photo- synthetic productivity. J. Fish. Res. Bd. Can. 15(3) : 453-493. Thomas, William H. 1964. An experimental evaluation of the C-'^'* meth- od for measuring phytoplankton production, using cultures of Dunaliella primolecta Butcher. U.S. Fish Wild. Serv., Fish. Bull. 63(2): 273-292. 1966. Surface nitrogenous nutrients and phyto- plankton in the northeastern tropical Pacific Ocean. Limnol. Oceanogr. 11(3): 393-400. 1969. Phytoplankton nutrient enrichment experi- ments off Baja California and in the eastern equatorial Pacific Ocean. J. Fish. Res. Bd. Can. 26(5): 1133-1145. 1970a. On nitrogen deficiency in tropical Pacific oceanic phytoplankton: Photosynthetic param- eters in poor and rich water. Limnol. Oceanogr. 15(3) : 380-385. 1970b. Effect of ammonium and nitrate concen- tration on chlorophyll increases in natural trop- ical Pacific phytoplankton populations. Limnol. Oceanogr. 15(3): 386-394. Thomas, W. H., E. H. Renger, and Anne N. Dodson. In press. Near-surface organic nitrogen in the eastern tropical Pacific Ocean. Deep-Sea Res. Oceanogr. Abstr. Yentsch, Charles S., and D. W. Menzel. 1963. A method for the determination of phyto- plankton chlorophyll and phaeophytin by fluor- escence. Deep-Sea Res. Oceanogr. Abstr. 10(3): 221-231. 92 ECOLOGICAL EFFICIENCY OF A PELAGIC MYSID SHRIMP; ESTIMATES FROM GROWTH, ENERGY BUDGET, AND MORTALITY STUDIES ' Robert I. Clutter^ and Gail H. Theilacker^ ABSTRACT The net ecological efficiency (yield/assimilated) of a population of Metamysidopsis elongata (Crus- tacea, Mysidacea) is estimated to be 32 %. The gross ecological efficiency (yield/ingested) is probably between 19 % and 29 %. Energy use by the field population was calculated from estimates of age specific natural mortality rates and data on growth, molting, reproduction, and respiration. Average growth and molting rates were determined by rearing the mysids in the laboratory. Size specific fecundity was determined from field and laboratory observations. The calorie contents of the mysids, their molts, eggs and larvae were estimated by bomb calorimetry and in part from biochemical composition. The energy used in metabolism was calculated from size specific respiration and data on body composition. Biological systems are organized by the flow of energ-y. Trophic structui-e, numbers of steps in food chains, and numbers of conjunctions in food webs depend on the amount of energy passed through populations to other populations. Energy units provide a means of expressing productivity in terms common to all organisms. The energy produced in the breakdown of biomass by organisms is stored as chemical en- ergy in the pyrophosphate bonds of adenosine triphosphate (Horowitz, 1968). The overall thermodynamic efficiency of this process is sim- ilar in all animals, about 60 to 70 '}t according to Krebs and Romberg (1957). It has been suggested (e.g. Slobodkin, 1961, 1962) that the efficiency of energy transfer between popula- tions of animals is also fairly constant. This efficiency is necessarily of lower order because, for example, there are losses involved in syn- thesizing macromolecules, in continually resyn- thesizing proteins that undergo thermal dena- turation, in transforming foodstuff energy into work energy (about 65 ^r efficiency), and in the degradation of energy during the perform- ' This research was supported in part by NSF Grant GB 7132. ' Formerly of National Marine Fisheries Service Fish- ery-Oceanography Center, La Jolla, Calif. 92037. ^ National Marine Fisheries Service Fishery-Oceanog- raphy Center, La Jolla, Calif. 92037. Manuscript received September 1970. FISHERY BULLETIN: VOL. 69. NO. 1, 1971. ance of work. All energy that passes through a population is either lost as heat or passes on to another trophic level. If one assumes that all mortality is caused by predation, the gross ecological efficiency (Phillipson, 1966) of energy transfer through that population is the ratio of the energy yield in mortality to the energy ingested. Through laboratory studies of growth, molt- ing, reproduction, respiration, body composition, and energy content, we have constructed an energy budget for the pelagic mysid shrimp Metamysidopsis elongata (Holmes). Various aspects of the distribution, behavior, and pop- ulation biology of this species have been de- scribed by Clutter (1967, 1969) and Fager and Clutter (1968). The energy budget data, to- gether with estimates of natural population mortality rates, are used to estimate net and gross ecological efficiencies for the field popu- lation. GROWTH AND DEVELOPMENT Metamysidopsis elongata is a member of the Mysidae, a family that is ubiquitous and often very abundant in most of the neritic zones of the world ocean. This species is free-swimming and occurs in shoals and swarms just above the sand bottom in areas where surf is common 93 FISHERY BULLETIN: VOL. 69, NO. 1 (Clutter 1967, 1969). As is characteristic of mysids, the eggs and larvae are held by the oostegites (brood pouch) of the adult females until they develop into juve- niles that are similar in form to the adults. The juveniles grow by shedding their exoskel- etons (ecdysis) at intervals that become pro- gressively longer until they reach maturity. Males and females develop distinguishable morphological features during the period of rapid growth prior to maturity. Growth be- comes progressively slower after maturity. Al- though there is no evidence that death occurs because of physiological aging, the maximum age observed was about 9 months. Most animals survive less than 3 months in the natural en- vironment . We assume that most of the na- tural mortality is caused by predation, especially by fishes. Some growth experiments have been reported for other species of Mysidae. Blegvad (1922) determined the growth rates of a few individu- als of My sis inernils from first stage juveniles through early maturity. Nouvel and Nouvel (1939) made disjunct determinations of time between molt stages for some size groups of Praunus flexuosis. Nair (1939) observed the time sequence in the egg and larva development of Mesopodopsis orientalis, determined the size and age at liberation, and noted the size at sex- ual maturity of males and females. In his review of growth in some marine Crustacea, Kurata (1960) presented the results of growth studies made by Ishikawa and Oshima on Neo- mysis japonica and by Matsudaira et al. on Gastrosaccus vulgaris. Mauchline (1967) main- tained adult Schistomysis spiritus in the labora- tory, estimated the time they take to attain sex- ual maturity, and estimated the minimum incu- bation time. Considering differences between species, sizes, and environmental temperatures, these reported patterns of development and size increase per molt are compatible with the results of our study. CULTURE METHODS Experimental animals were collected during the day from the middle of their habitat with nets (Clutter, 1965; Fager, Flechsig, Ford, Clutter, and Ghelardi, 1966). They were placed in large (20-50 liter), opaque plastic containei's with covers and transported to the laboratory within 1 to 2 hr after the time of capture. The culture methods were about the same as those described by Lasker and Theilacker (1965) for euphausid shrimps. Individual animals were placed in rectangular clear plastic containers in about 500 ml of sea water. The small con- tainers were partly immei-sed in trays of run- ning sea water. Since the running sea water was pumped continuously into the aquarium from midwater ofl'shore, within the Metamysi- dopsis habitation zone, the laboratory temper- atures ( 14°-20° C) were about the same as those that the animals would have experienced in their natural environment. Animals of both sexes and of several sizes were selected for the e.xperiments. Young ju- veniles were procured by j^lacing pregnant fe- males in containers and recovering the young on the day following their release from the brood pouch, which occurred at night. These young were then placed in separate containers. To determine the incubation time, i.e. the time from fertilization of the eggs to release from the brood pouch as juveniles, pregnant females with known times of fertilization were placed in in- dividual containers so that larval development could be observed. Mysids of all ages were fed freshly hatched nauplius larvae of brine shrimp, (Artemia sa- lina). Twice each week the mysids were re- moved while their containers were emptied of excess food and cleaned with hot fresh water followed by a sea water rinse. They were then provided with excess quantities of fresh nauplii in clean sea water. The containers were examined every day for the presence of molts or, occasionally, carcasses. The molts and carcasses were removed and placed individually in small vials of 5 % Forma- lin for subsequent microscopical examination and measurement. OOGENESIS AND INCUBATION Since Metamysidopsis has a transparent cara- 94 CLUTTER and THEILACKER: PELAGIC MYSID SHRIMP pace and body wall, it is possible to observe the late stages of oogenesis in live animals without dissecting them. The ovary (cf. Nair, 1939, for description) is situated in the interspace be- tween the alimentary canal and the pericardial floor. Its most obvious feature is the pair of larger tubes that lay side by side. It is in these tubes that the eggs to be extruded into the brood pouch are invested with yolk. The process of yolk formation takes about a week in Metamysi- dopsis and is completed just before the female molts and copulates. By observing the ova in these tubes it is possible to estimate the size or age at first reproduction in maturing females, and to count the number of eggs that will be spawned by reproducing females of all ages. Copulation occurs at night within 2 to 3 min after the mature female molts, during which time sperm are passed into the empty brood pouch by the attending adult male. The eggs are subsequently extruded into the brood pouch where they are fertilized. The eggs hatch from the vitelline membrane after 2 to 3 days. Ac- cording to Manton (1928) and Nair (1939) a larval ecdysis occurs in the brood pouch shortly before the larvae are liberated. These late stage larvae have movable appendages and pigmented eyes that show through the transparent ooste- gites of the brooding female. The small quantity of yolk that is present after the larval ecdysis is absorbed, or nearly so, prior to liberation from the brood pouch. After liberation the larvae tend to sink, then, according to Nair (1939), they undergo a sec- ond larval ecdysis after which the statocysts appear and they are capable of swimming. The mysids assume this highly mobile juvenile form within a few minutes after liberation. Although we did not attempt to distinguish sexes of larvae and juveniles, the observations of Nair (1939) indicate that dimorphism is exhibited by the ant- ennules and abdominal appendages even though neither the brood pouch nor the penis is de- veloped. Incubation time was determined in the lab- oratory. Adult females and adult males were observed in an aquarium during molting and copulation. Ten females were caught after be- ing observed in copulo and were placed in sep- arate containers of sea water at the temperature of their natural environment at that time (17°- 19° C). Five of them were removed, at var- ious times, to determine the stages of develop- ment of the young. The remaining five all re- leased their young as juveniles on the tenth day after fertilization. In addition, a large number of nonpregnant adult females were kept in separate containers for various periods up to 157 days. The range of intermolt periods in 218 observations was 5 to 13 days; the median and modal values were both 10 days. There was no obvious temper- ature effect. The adult females molt just before fertilization and just after liberation of the young; therefore, the average incubation time was taken to be 10 days. This is intermediate between incubation times given for Mysidae that live and reproduce at higher and lower temper- atures. Nair (1939) determined the incubation time of Mesopodopsis orientaUs to be 4 days at 25° to 29° C. Mauchline (1967) reports a min- imum incubation time of 3 weeks for Schisto- mysis spiritus at 12.5° C. MOLTING To avoid handling and possible injury of the experimental animals, the growth rates were determined by measuring molts. The molts suf- fered no appreciable decomposition because they were collected on the day following ecdysis. The morphological development of the animals was usually discernable from their molts. But the molts are fragile, split just back of the cara- pace where the animals emerge, and easily stretched out of shape. Therefore, to measure growth it was necessary to measure a part of the molt that always retained its form and bore a consistent relationship to the body length. Uropod-Body Length Relationship The exopod of the uropod (tail fan) was used to estimate the body length of each animal for its previous intermolt period. The uropods were measured from the base (end of last abdominal segment) to the tip, not including spines, which were sometimes broken, with an ocular micro- 95 FISHERY BULLETIN: VOL. 59, NO. I meter, at 27.5 x magnification. The relationship between uropod length and body length was established from a selected ser- ies of 94 animals that had been collected in the field and pi-eserved. The series included ani- mals that ranged in body length from 0.8 mm to 7.2 mm, and included late stage larvae, juveniles, immatures, and adults. Both sexes were in- cluded; there was no difi'erence between sexes in this relationship. The body length was measured from the end of the last abdominal segment (base of uropod) to the anterior edge of the carapace, behind the insertion of the eyestalk. Mysids tend to curl when preserved, and they can be distorted to appear longer if they are stretched when meas- ured. To avoid this we chose specimens that were at most only slightly curved, and measured the length of the arc through the midline of those that had significant curvature, rather than the straight line distance between head and tail. As shown in Figure 1, the relationship be- tween uropod length and body length is linear. The body length is 4.5 times the uropod length. Table 1. — Frequency of molting periods observed for Metamysidopsis in the laboratory. FiGUKB 1. — Relationship between uropod length and body length of Metamysidopsis. Molting Frequency Average intermolt periods were estimated from 414 observations, 146 on males and 268 on females. In many cases several observations were made on the same animal. The maximum period of laboratory survival for a single ani- mal was 157 days, and the maximum number of molts observed for a single animal (not the same Infermo t Period (dc ys) Sex and length 3 4 5 6 7 8 9 10 11 12 13 o c D 1 c o Females 2 3 4 4 4.0 1 3 6 2 4 4 4.3 jr 4 5 3 1 4 4-5 4.6 ai £ 5 3 7 7 1 5 2 5-6 6 6.2 i 6 10 7 9 13 13 28 17 5 8 10 9-10 9.2 " 7 11 8 6 9 16 12 28 9 9 11 10 9.4 Males E 2 11 3 3 3.0 ^ 3 2 II 1 4 4 3.9 JZ ? '^ 2 15 8 1 1 4 4 4.4 ~ 5 6 29 20 4 5 5-6 5.4 m 6 6 II 8 7 3 5 5-6 5.7 animal) was 21. The molting frequency data for animals reared in the laboratory are sum- marized in Table 1. The sex of the juveniles was established after they had grown large enough to develop obvious morphological dif- ferences. Supplementary data on molting frequency in the field population were obtained indirectly. Over a period of 3 days, 1,211 juveniles + im- matures and 2,979 adults were brought into the laboratory late in the day and placed in large aquaria. The following morning all the animals and their molts were collected and counted. Of the juveniles + immatures 218 or 18 % had molted, and of the adults 356 or 12 % had molted. The recii)rocal of the relative number molting is an estimate of molting period. The observed reciprocals were 5.6 for juveniles + immatures and 8.3 for adults. Since these values are mid- way in the ranges shown by laboratory animals (3-8 days for juveniles + immatures and 4-13 days for adults) we assume that the laboratory observations are valid estimates of molting fre- quency in the population as a whole. Although our observations were made from February to October, and the water tempera- tures in the rearing troughs varied from 14° to 20° C, we were unable to detect any obvious effects of temperature or time of year on molting 96 CLUTTER and THEILACKER: PELAGIC MYSID SHRIMP frequency or growth rates. Nouvel and Nouvel (1939) stated that the intermolt period for Praunus flexiiosis is least during the warmest months, and the incubatory period is 15 days in August and 3 to 4 weeks in September. Las- ker (1966) showed that Euphausia pacifica in- termolt ijeriods varied as the water temperature fluctuated, and that the intermolt period was shortened by an artificially produced warm per- iod, but that temperatures above 12° C did not accelerate molting further. Since we do not have evidence to the contrary, we must assume that our laboratory observa- tions on molting frequency provide adequate average values. From the median values given in Table 1 and estimated average growth rates (see below) we have estimated the molting schedules of females and males from juveniles to mature adults as follows: Females: first six molts — 4 days seventh molt — 5 days eighth molt — 6 days ninth molt — 8 days tenth molt and thereafter — 10 days IVIales: first four molts — 3 days fifth to eighth molts — 4 days ninth and tenth molts — 5 days eleventh molt and thereafter — 6 days GROWTH AND MATURATION Evidence of the temporal sequence of growth and maturation can be obtained from following peaks of abundance of size groups in natural populations. We sequentially sampled the my- sids in the field and observed some shifting peaks. But we consider that the results are not very reliable because of temporal changes in age- specific mortality rates (Fager and Clutter, 1968). Therefore, all the age-specific growth estimates presented here were obtained from laboratory studies. Observed Gro'wth A few mysids were reared in the laboratory from fertilized egg to adult. Several were reared from egg through the juvenile stage. In addi- tion, larger numbers of various sizes were col- lected in the field and kept in the laboratory for several molts. The growth data from these animals were combined as shown in Figure 2 (females) and Figure 3 (males). The sexes were separated because the growth and molting rates of males and females are different. As they are shown in Figures 2 and 3, these individual growth curves are simplified and slightly incorrect rep- resentations of true growth, for two reasons. First, the growth of the body integument is represented to be continuous, whereas it actually occurs in discrete increments. Second, the age Figure 2. — Observed growth in length (from molts) of Metamysidopsis females in the laboratory. Figure 3. — Observed growth in length (from molts) of Metamysidopsis males in the laboratory. 97 FISHERY BULLETIN: VOL. 69, NO. I shown is the age of the animal at the time it molted, rathei- than the age at the time that the molted integument was first formed. The pro- cedure for combining the various growth curves of individual animals was to first plot the growth of the animals of known age, and then plot the other gro\vth curves (actual ages unknown) in a manner that showed the least variation from the apparent trend. Some of the apparent variability in growth rates may be attributable to differences in the temperature at which the growth occurred, but we did not detect any obvious temperature efl^ect. Considerable individual variability occurred among animals of the same size or age that were reared simultaneously. Maturation Changes in morphology in relation to size, and known or estimated age, wei'e observed in the molts of animals reared in the laboratory. Ob- servations were made on live females collected from the field population to determine the size at which yolk invested ova first appear in the ovaries. Supplementary observations on the re- lationship between size and body form were made on preserved animals that had been col- lected in the field. There is some evidence from previous samples taken for other purposes (Clutter, 1967, 1969) that the relationship be- tween size and stage of development may vary seasonally. But during the period of observa- tions reported here, this did not appear to be significant. In particular, we wished to determine (1) the size (and subsequently the age) at which males and females were easily distinguishable by their secondary sexual characteristics, (2) the size at the onset of maturity, and (3) the size at which spawning and brooding of eggs and larvae occurs. The external characteristics that most obviously separate males from females of this species are the enlarged oostegites (brood pouches) of the females and the enlarged pleo- pods (abdominal legs) and antennae of the males. There is some variability in the size at which the stages of development occur. Therefore, our estimates are average values. The larvae are released and juvenile form is attained at age 10 days; at this time both sexes are about 1.2 mm long (body length; excluding antennae, eyes, and tail fan). Males exhibit sub-adult morphology when about 3.7 mm long, and be- come mature at 4.3 mm. Females exhibit sub- adult form at 4.0 mm, the ova become infused with yolk at 4.5 mm, and the eggs are extruded into the brood pouch, fertilized, and incubated at slightly less than 5.2 mm. Average Growth in Length Average continuous growth curves were fitted by eye to the combined growth data plotted in Figures 2 and 3. These curves are represented by the lower curves (fine, continuous unbroken lines) in Figure 4 (females) and Figure 5 (males) . These continuous curves represent the size of the molt at the time — days from fertili- zation — that the molt was shed. Actually the integument of the animal had attained that size by the beginning of the intermolt period in question. The true growth of the integument of the average animal is represented by the stair- step pattern, which is based on the molting fre- quency analysis. The broken curved line of con- tinuous growth (Fig. 4 and 5) represents the probable pattern of temporal change in average organic weight of the animal. This curve con- nects the points halfway betw^een the beginnings and endings of the intermolt periods. Since the average sizes at various stages of development were determined, it was possible to estimate the average time schedules of ma- turation and reproduction for females and males on the basis of the growth curves. The average female begins to develop a brood pouch at the seventh molt, 39 days after becoming a fertilized egg. Yolk invested ova begin to be formed at 45 days, during the ninth intermolt period; the ova are extruded into the developed brood pouch and fertilized at the beginning of the tenth in- termolt period, at 53 days; and reproduction can occur at 10 day intervals thereafter. Males and females gi-ow at rates that are in- distinguishable up to the age of about 30 days, even though the juvenile males molt more fre- quently than juvenile females. After that the 98 CLUTTER and THEILACKER: PELAGIC MYSID SHRIMP Figure 4. — Average growth in length of female Meta- mysidopsis in the laboratory. The lower curve (fine continuous line) was fitted to molt size data (Fig. 2). The steps represent changes in integument size. The upper curve (heavy broken line) represents the average size of the animals, assuming that the addition of body tissue is continuous. - alongalion of pleopodi ond or'enna* 1 3B dart I Figure 5. — Average gro%vth in length of male Meta- mysidopsis in the laboratory. The lower curve (fine continuous line) was fitted to molt size data (Fig. 3). The steps represent changes in integument size. The upper curve (heavy broken line) represents the average size of the animals, assuming that the addition of body tissue is continuous. males grow more slowly. The males develop easily recogriized secondary sexual character- istics at an average age of 38 days and become sexually mature after about 48 days. Average age at maturity was estimated from observa- tions of testes and copulatory behavior in the laboratory as well as from external morphology. Average Growth in Weight To estimate gro\vth in terms of energy it is necessary to translate growth in length into growth in dry weight. This growth in dry weight is then translated into growth in organic (ash-free) weight and thereafter into calories. The dry weights of Metamysidopsis of body lengths ranging from 1.9 mm to 6.5 mm were determined. The animals were captured alive, measured, washed very briefly with distilled water, and dried at 60° C in an oven for 24 hr. They were then weighed individually on a Cahn electrobalance immediately after they were re- moved from the oven. The observed relationship between body length and dry weight is shown in Figure 6. Figure 6. — Relationship between body length and dry weight of Metamysidopsis. The equation for the relationship was deter- mined empirically by fitting a straight line to the logarithms of body length and dry weight by the method of Bartlett (1949). The rela- tionship is: log,, (weight) = -5.436 + 2.77 log,, (length) or weight = 0.00436 (length)^ " where weight is expressed in mg and length in mm. It is common to assume that body weight and body volume have a linear relationship, and that body volume is proportional to the third power of length. Therefore dry weight is expected to 99 FISHERY BULLETIN: VOL. 69, NO. 1 be proportional to the third power of body length (Bertalanffy, 1951). The observed relationship does not quite conform to the expected. The re- lationship between body length and body di- ameter appears to be linear (Fig. 7); therefore the body volume must be proportional to the third power of the body length. The observed relationship between weight and length could be the result of orthogonal growth of the ap- pendages, which become progressively larger as the animals mature. From the average length-weight relationship and the average continuous growth in length curves (Fig. 4 and 5) we have calculated the average growth in weight curves shown in Fig- ure 8. The average continuous growth in length curves represented by the heavy broken lines in Figures 4 and 5 were used to calculate growth in weight, because we assume that growth in organic weight is continuous during intermolt periods even though growth of the integument occurs in discrete steps. The estimated growth in weight of males was extrapolated by eye from age 175 days to age 204 days. We do not have laboratory growth estimates for these larger males, but they occurred in the field population. The average dry weight per egg (140 eggs in sample) was 5.5 fig. Larvae weigh slightly less than this because they lose weight through metabolism while in the brood pouch, even though their ash content is slightly higher than that of the eggs. Figure 7. — Relationship between body length and body diameter of Metamysidopsis. Figure 8.— Average growth in dry weight of Meta- mydisopsis females and males in the laboratory. REPRODUCTION Data on reproduction and associated energy use are easier to obtain for Mysidae than for most pelagic invertebrates. The eggs and larvae are carried in the brood pouch of the female, and the incipient eggs can be counted prior to their full development and extrusion because the body walls of the mysids are transparent. In addition, copulation and fertilization can be ob- served in the laboratory, and frequency of preg- nancy among mature females can be observed in the natural population through sequential sampling because all stages live in the same area while gestating as they do when not reproducing. Nevertheless, average reproduction rate in these animals is not easy to assess with absolute certainty. FECUNDITY Minimum Estimate The most straightforward way to estimate fecundity is to collect animals in the field, pre- serve them, and count the number of eggs or larvae carried by females of diff"erent sizes. Figure 9 shows the relationship between body lengths and number of young for 310 females collected in the field at various times during the year. The data include 125 females bearing eggs and 185 bearing larvae; we excluded ani- mals that had obviously lost young during cap- ture and preservation. For both eggs and lar- 100 CLUTTER and THEILACKER: PELAGIC MYSID SHRIM' number roung : 4 9(body langth] - 14 5 numb*r vgo* : S.4[body Unglh) -16.0 . the time of extrusion of the eggs and the esti- mated average age at which they were counted (7 days) was estimated to be about 0.91. The number of brood pouch young per female was adjusted to the equivalent number of eggs ex- truded per female by multiplying the number of young by 1/0.91 = 1.10. The relationship (Fig. 9) then becomes: number of eggs = 5.4 (body length, mm) - 16.0, which is shown in Figure 9 as the upper, dashed line. We consider this to be a minimum estimate of fecundity, because some females that had lost eggs and larvae from the brood pouches during collection and preservation were probably in- cluded, despite our attempt to exclude them. Figure 9. — Relationship between body length and num- ber of brood pouch young (eggs and larvae) of preserved animals that were collected in the field. The lower line (continuous) was fitted to the points by the method of Bartlett (1949). The upper line (dashed) represents the equivalent relationship for newly laid eggs, assuming a brood pouch mortality of 0.013/day (see text). vae, the number of young per female is highly variable. The average relationship between the size of the female and the number of young, calculated by the method of Bartlett (1949), is represented by the straight line: number of young = 4.9 (body length, mm) - 14.5. This estimate of fecundity is not quite cor- rect because it was made from counts of eggs and larvae that were a few days old. Some eggs and larvae apparently are lost from the brood pouch during the incubation period. Therefore, we adjusted the relationship to account for the mortality which occurs during the incubation period. To estimate the mortality during incu- bation, counts were made of the maturing ova in the ovaries of 40 adult females and counts were made of late stage larvae in the brood pouches of 27 females of the same size, collected at the same time. The ratio of mean number of larvae/mean number of ova was 0.90. The larvae were estimated to be 8 days old, giving an instantaneous mortality rate of 0.013/day. The average age of the eggs and larvae from the 310 preserved females (Fig. 9) was esti- mated to be 7 days. Therefore, the relative sur- vival of the young in the brood pouch between Maximum Estimate We observed that the females that had re- leased young during the laboratory experiments had a higher apparent fecundity than those that were collected and preserved in the field. It is possible that there was some bias in selecting animals for the laboratory experiments, but we were not aware of any. The number of young released per female is plotted against the body length of the female for those 17 specimens in Figure 10. The average relationship between K) numbe. oggt -- 5 5 ( bod, lengihl-ll? , ^ "^ 2i \,^ o I 30 ^■^ ^^^-"''''^ £> E IS 3 '^ z -^^^ \ Int^mb*' lo'.a* '- d.Slbody l*nglh ) - 10.4 10 s 1 1 l^ Figure 10. — Relationship between body length and num- ber of young released by experimental animals in the laboratory. The lower line (continuous) was fitted to the points by the method of Bartlett (1949). The upper line (dashed) represents the equivalent relationship for newly laid eggs, assuming a brood pouch mortality of 0.013/day (see text). 101 FISHERY BULLETIN: VOL. 69, NO. 1 body length and number of young, calculated by the method of Bartlett ( 1949) , was: number of young = 4.8 (body length, mm) -10.4. This is represented by the lower, unbroken straight line in Figure 10. This relationship gives estimates of fecundity that are about 1.5 to 2 young per female higher than the relationship calculated from preserved animals. But this is not quite a maximum esti- mate of fecundity because it does not include the reduction from mortality that occurs during incubation. As already demonstrated, we can assume a brood pouch mortality rate of 0.013 per day. The relative survival of young in the brood pouch during the 10 days between the extrusion of eggs and the release of larvae was therefore estimated to be 0.87. The number of young released per female was adjusted to the equiv- alent number of eggs extruded per female by multiplying the number of young by 1/0.87 = 1.15. The relationship (Fig. 10) then becomes: number of eggs = 5.5 (body length, mm) -11.9, which is shown in Figure 10, as the upper, dashed line. This relationship gives estimates of fecundity that are about four eggs per female higher than the minimum estimates calculated from pre- served animals. We consider this to be the max- imum estimate of fecundity. It is the same as that used by Fager and Clutter (1968). COPULATION AND FERTILITY The fecundity estimates given above apply only to the females that engage in copulation and are fertilized. Mature females that are not fertilized apparently extrude some eggs, but only about one-half the usual number. Many observations of copulation were made in the laboratory (Clutter, 1969). It occurs in artificial light as well as in the dark, but only at night, between about 2000 and 2400 hr. It oc- cui-s within only 2 to 3 min after the mature females molt, and apparently only when the fe- male exudes a pheromone to attract adult males of the same species. Ten females were captured immediately after they were observed in copulo and kept in sep- arate chambers for 10 days. Impregnation had been successful and the usual number of eggs were extruded in every instance. Some adult females that molt do not stimulate males to at- tend them. Ten adult females were captured after they had been observed to be unattended by males during molting and recovery. They later extruded only about one-half of the normal number of eggs, which eventually disappeared from the brood pouch, presumably because they were infertile. Therefore, the unfertilized fe- males expended only about half the amount of energy in eggs that the fertilized females ex- pended. Since the mature females are subject to fertil- ization for only a few minutes following molting, and they apparently do not always attract males during the time, copulation does not always oc- cur. Therefore, not all produce young every 10 days. In a large number of field collections during all seasons, the observed fraction of ma- ture females carrying eggs or larvae in their brood pouches varied from 18 ^r to 78 Sr I the mean was 51 '}r . We are not certain of the source of this variability; there is some evi- dence that it could be related to population den- sity (Clutter, 1969) . We have assumed an aver- age value of 50 fr for the purpose of calculating the amount of energy used in reproduction. On the average, mature females extrude the usual number of eggs about one-half of the time, and they otherwise extrude only one-half of the usual number of eggs. Therefore, the effective average fecundity, in terms of energy used in reproduction (but not in terms of the number of viable young produced), is 0.5 + (0.5) (0.5) = 75 % of the fecundity estimated from counts of young produced/female. For the purpose of calculating the amount of energy used in repro- duction the fecundity equations are: minimum — number of eggs = 4.1 (body length, mm) - 12.0 maximum — number of eggs = 4.1 (body length, mm) -8.9 The second of these relationships is used in the ensuing energy budget calculations. 102 CLUTTER and THEILACKER; PELAGIC MYSID SHRIMP RESPIRATION A polarographic oxygen electrode (Kanwish- er, 1959) was used in a closed system to measure the respiration rates of Metamysidopsis. Both temperature and oxygen were recorded contin- uously on a strip chart. The experimental animals were taken from large constant-flow holding tanks (temperature 14°. 17° C) and acclimated overnight at the tem- perature used in the experiments (13.8°-18.1° C) , to avoid the overshoot in oxygen consumption described by Grainger (1956). They were then washed in millipore-filtered seawater, counted, and transferred to previously filtered seawater in the oxygen electrode system. In each experi- ment an attempt was made to use animals of a limited size range. During the run they were held within a 10- ml chamber, baffled at each end with silk screen cloth of 282 /i mesh aperture size. The water in the closed system circulated through this chamber and then past the electrode at a constant rate. The whole system was im- mersed in a temperature-controlled water bath. Oxygen use by bacteria was measured by mak- ing blank runs with the same water both befoi-e and after each test run. Bacterial use amounted to less than 2 ^c . Oxygen consumption by the mysids was corrected for bacterial uptake. The decrease in relative oxygen tension with time was nearly linear in both the blank runs and the test runs. The results of the respiration experiments are shown in Table 2. Observed weight-specific Table 2. — Summary of respiration experiments on Metamysidopsis. Specimens Number Mean dry weight Water temper- ature Weight-specific resp ration rote Uncorrected Corrected^ Juveniles 99 Ml. 003 ° C. 13.8 (ill Oi/mg 7.71 dry wt hr) 7.54 Juvenile ond immature moles and females 176 0,07 18.0 5-40 4.76 " 297 297 132 0-08 0.08 0.14 18.1 18.1 138 5.03 6.78 3.92 4.48 5.93 3.82 Immature females 85 0.28 15.2 1.95 2.46 Males Brooding females 51 27 0.31 0.47 138 13.8 3.60 3.22 3.53 3.16 27 0.66 13.3 2.65 2.59 lOO BO _-«■ ^ : ^ . ""i^j... „,. cadu'*) -' ^^ \ T B = 27wO" -X V E {Boxlan p'ocaduia 1 V. 6- NJ i 30 X S. \^ 10 Figure 11. — Relation between respiration rate of Met- amysidopsis and size at 16° C. The symbol if' rep- resents respiration rate per dry unit weight (R/W). The lines were fitted to the circle points by two sta- tistical pocedures. The x points are values calculated from published data on other species of Mysidae: 1- Neo7nysis americana (RajTnont and Conover 1961) ; 2-Neomysis integer (Raymont, Austin and Linford 1966); 3-Hemimysis labornae (Grainger 1956). respiration rates (/tl Oj/mg dry weight hr) were corrected for the initial percent oxygen satura- tion and for temperature. In correcting for temperature, a Q,o of 1.9 was used (Grainger, 1956). All values were corrected to 16° C, which is about the median of the year-round temperatures that occur in the natural environ- ment of the mysids. The corrected weight-specific respiration data are plotted in Figure 11 on log-log scales. The symbol R' (Conover, 1960) represents the res- piration rate per unit dry weight (R/W). The average relationship between mean dry weight and R' was estimated by two statistical pro- cedures. First, a straight line was fitted to the logarithmically transformed data by the median procedure (Tate and Clelland, 1957). This gave the relationship: or R' = 2.0 H'-o-3« R = 2.0 (^"-ss ^ Corrected for oxygen saturation level and corrected to temperature of 16.0° C by using Qio = 1.9 (Grainger, 1956). where R = respiration rate in fi\ Oj/hr and W = mean dry weight in mg. Second, a straight line was fitted to the logarith- mically transformed data by the method of 103 Bartlett (1949). This gave the relationship: R' = 2.2 W-"-'^- or R = 2.2 f^»-«» Theoretically, the respiration rate is expected to be proportional to the % power of weight. Since our estimates are slightly above (0.68) and slightly below (0.62) the expected value of 0.67, we consider that the % power relationship is the best estimate for Metanujsidopsis and that the best estimate of respiration rate (/nl Oj/hr) is given by the equation: /? = 2.1 1^"" Estimates of weight -specific respiration for three other, somewhat larger, species of Mysidae are compared with Metamysidopsis in Figure 11. The upper four points ("1" on Fig. 11) represents results for Neomysis americana from Ravmont and Conover (1961) that were ad- justed from 4° C or 10° C to 16° C by using a Q,o value of 1.6 that was estimated from their data. The intermediate point is an estimate of the median value oxygen consumption rate cal- culated from 12 determinations on Neomysis integer (Raymont, Austin, and Linford, 1966) that had been adjusted to 16° C by using a Q,o of 1.9 (Grainger, 1956). The lower point was estimated from the results of Grainger (1956) for Hemimysis lamomae. The ranges of values for these three larger species are about the same as the range (1-3 ^il/hr) calculated from the seasonal change data of Raymont et al. (1966) that had been adjusted to 16° C. The estimates for Metamysidopsis and the other three Mysidae FISHERY BULLETIN: VOL. 69. NO. I all lie well above the relationships calculated for marine planktonic Crustacea by Conover (1960) . BODY COMPOSITION AND ENERGY CONTENT To estimate the amounts of energy used in respiration, molting, and reproduction it was necessary to determine the body composition of the mysids, their molts, and their young. For these analyses the animals were captured alive and, within 2 hr, placed in a constant-flow hold- ing tank at 15° to 17° C where they were kept for a short time prior to analysis. BODY COMPOSITION The estimates of body composition of dried animals and molts are summarized in Table 3. The estimates for ash, protein, lipid, carbohy- drate, and chitin are not considered to be accu- rate past the first decimal point. The fractional percentage values are entered so that the sums will equal 100 ^/c. The methods by which these values were determined will be explained item by item. To determine dry weights, the animals were washed very briefly with distilled water while still alive, then were oven-dried to constant weight at 60° C. Materials that were available only in small quantities were weighed on a Cahn electrobalance. Ash Ash content was estimated by incinerating Table 3. — Average composition and energy content of dry Metamysi- dopsis bodies, molts, eggs, and larvae. Tabulated values for composition are %, and for energy content are cal/mg. The sums of % ash, "pro- tein", lipid, carbohydrate and chitin = 100 %. Nitrogen Carbon Ash "Protein"* Lipid Carbo- hydrate Chitin Energy % % % % % % % Cal/mg Body, whole II.5 36.8 12.5 69.0 10.0 1.5 7.0 4.60 Body, organic 13.2 42.0 79.0 11,4 1,6 8.0 5.24 Molt, v^hole 23.5 44 8 30.9 24.3 2.48 Molt, organic 42.S 56 44.0 4.49 Egg, whole 58.0 6.0 35.2 588 7.16 Egg, organic 61.8 37.5 62.5 7.62 Lorva, whole 45.7 66 60.8 28.9 3.7 5.78 Larva, organic — 48.8 65.0 31.0 4.0 6.20 * "protein" may include free omino acids. 104 CLUTTER and THEILACKER, PELAGIC MYSID SHRIMP whole animals or molts in a muffle furnace at 500° C and weighing the residue. Ash determi- nations were made on six samples composed of mixed animals, juveniles, immatures, adult males, and adult females. The samples con- tained from 2.7 to 7.3 mg of dried animals ; the mean ash content was 12.5 % of the dry weight, and the range was 9.4 to 13.3 % . There was no obvious difference between age groups or sexes. This ash content is within the range, but slightly higher than the mean, of values re- ported for other Mysidae: Mysis flexuosa — 16 ^f (Hensen, 1887) and 11.9 '^h (Delff, 1912, quoted by Vinogradov, 1953); Neomysis integer — 7.9 % (Raymont, Austin, and Linford. 1964) ; Siriella aequiremis — 10.2 ^r (Omori, 1969). Molts used for ash determinations were col- lected in the laboratory immediately after they were shed. Two samples, weighing 1.1 and 0.6 mg, composed of molts from a wide size range of mysids of both sexes had ash contents of 44.4 % and 45.7 Sf; the mean was 44.8 %. Lasker (1966) reported a similar value (46 %) for Euphausia pacifica. This high ash content in the molts suggests that a large fraction of the total body ash resides in the integuments of the whole animals. From 10 observations, we have found that the dry weight of the molt is on the average 13 "^r of the dry weight of the animal that sheds the molt. Assuming that the ash content of the molt is the same as the ash content of the integument of the whole animal, we estimate that 47 % of the body ash resides in the integument. Ash content of brood pouch young was esti- mated fi-om a large number of specimens taken from live females. A dry sample of 0.6 mg of newly hatched larvae had an ash content of 6.1 %. A sample of 1.2 mg of late stage larvae had an ash content of 6.6 ',? Ash content of eggs was not determined; we assume that the ash content is slightly less than that of the newly hatched larvae, and we have used a value of 6.0 %. Nitrogen and Carbon Nitrogen content was determined by the micro-Kjeldahl method from three samples of mixed juvenile-adult animals. The dry weights of the samples were 12, 24, and 63 mg, and contained 13.1 %, 11.7%, and 11.2 % nitrogen respectively; the mean was 11.5 % of total dry weight. From a large number of determina- tions, Raymont et al. (1964) found a value of 11.4 % for Neo?nysis integer. Omori (1969) reported 11.0 % for Siriella aequiremis, and Jawed (1969) found 11.9 % for Neomysis rayii. Carbon content was determined with an F and M carbon analyser model 180, described by Lasker (1966). We assume that all organic carbon, including that in chitin, is liberated by this method. Three samples of females, without young, that weighed 0.2 to 0.4 mg, had carbon fractions be- tween 35.6 9f and 38.1 % of dry weight; the mean was 36.8 %. This estimate is intermedi- ate among other values reported for mysids: Lophogaster sp. (family Lophogastridae) — 46.8 % (Curl, 1962a); Neomysis integer — 30.2 % and 29.5 % (Raymont et al., 1964, 1966) ; mixed mysids and euphausids — 40.7 % (Beers, 1966); Siriella aequiremis — 42.4 (Omori, 1969). From his analysis of several kinds of arthropods, Curl (1962a) found an average of about 38 ':? of the dry weight as carbon. He points out that this is about % of the commonly assumed value of 50 % (Krogh, 1934). In our carbon analysis of molts and young, we found that a 0.2-mg sample of fresh dried molts had 23.5 ^'r carbon, a 0.4-mg sample of eggs had 58.0 % carbon, a 0.4-gm sample of midstage larvae had 47.1 % carbon. The carbon contents of the ash-free organic fractions of the material were calculated from these values. Lasker (1966) found 17 % carbon in the molts of Euphausia pacifica and 50 % carbon in the eggs. Macromolecular Components We assume that the body nitrogen of our spe- cies, Metamysidopsis , is present as protein, free amino acids, and chitin (Raymont, Austin, and Linford, 1968). We made no evaluation of chitin content, but used the value of 7 % de- termined for Neomysis integer by Raymont et al. (1964). The percent "protein" (may include free amino acids) was estimated by the follow- ing relationship, given that 16 % of "protein" 105 FISHERY BLLLETIN: VOL, 69, NO- I is nitrogen, 6.5 "^r of ciiitin is nitrogen, and 7 '/c of the dry body is chitin: 0.16 ("protein") + (0.065) (0.07) = 0.115. From this relation- ship, the "protein" content of the whole dry body was estimated to be 69 %, which is sim- ilar to the value to 71 % protein estimated di- rectly by Raymont et al. (1964) for Neomysis integer. According to the estimates of Raymont et al. (1968) , the percent nitrogen in proteins of Mysidae may be lower than the value of 16 % commonly assumed for animal tissues. They found 13.3 9r N in the body protein of Neomysis integer, and estimated that about 17 ^/c of what we would have designated as "protein" nitrogen was actually free amino acid nitrogen. They suggest that the amino acids may function in osmoregulation for Neomysis integer, which is a euryhaline-brackish water species. We know nothing directly about this for Metamysidopsis. Our species lives in a constant oceanic salinity, and we estimated the ash content to be higher than that of N. integer. Therefore, a high con- centration of free amino acids may not be ne- cessary for osmoregulation in our species. What- ever the ratio of protein/free amino acids may be in Metamysidopsis , our energy calculations should not be affected materially. The lipid content of the mysid bodies was esti- mated by placing samples of dried, crushed bodies successively for 1 hr in each of two 10-ml portions of ethyl alcohol and two 10-ml washes of petroleum ether. The lipid content was esti- mated as the difference in dry weight before and after extraction. Two dry samples of mixed animals, weighing 62.9 mg and 13.4 mg, gave values of 9 % and 11 % lipid respectively. A third sample, containing 24.1 mg of brooding females that had full complements of young in their brood pouches, gave a value of 19 Cr lipid. Linford (1965) found that large females of Neomysis integer carrying young had higher lipid contents than males. From our knowledge of the number of young per female and the esti- mated percent lipid in the young, we calculate that i/i. to 1/2 of the 19 ^r lipid value could be contributed by the brood pouch young. There- fore, we have excluded the 19 ^r value from our estimate, and we have used 10 '/c as the estimate of average lipid content of the dry bodies. This is slightly less than the value of 13 7r estimated for Neomysis integer by Raymont et al. (1964), but within the range of means for three species estimated from a large number of determina- tions by Linford (1965): Mesopodopsis slavveri — 9.0 % ; Neomysis integer- — 10.1 S^ ; Praimus neglectus — • 9.3 %. The carbohydrate content of the mysids was estimated as the amount of macromolecular material remaining after the average estimates for ash, protein, chitin, and fat are subtracted from the dry weight. This remainder is 1.5 %. Apparently the carbohydrate fraction is low in all pelagic Crustacea. Raymont and Conover (1961) found that 1 '? of the dry weight of Neomysis aniericana was glucose; Raymont and Krishnaswamy (1960) found 1.3 ^r carbohy- drate in dry Neomysis integer; and Raymont et al. (1964) found 2.4 9( carbohydrate in dry Neomysis integer. We did no detailed analyses of the composition of molts, but we assume that the molt is com- posed of structural materials rather than energy storage materials. Since we consider that carbo- hydrates and lipids are virtually absent, we entered zero values for them in Table 3. The "protein"/chitin relationship was determined in- directly. First, we estimated the smiount of carbon in the average protein of the mysids from the relationship: (■■f C as protein) = C/c C in body) — (% C as chitin) — (% C as lipid) — (% C as carbo- hydrate) . The percent carbon in the organic fraction of the body is 42 ""f , the chitin fraction is taken as 8 '( , the chitin is assumed to be 50 % carbon (Curl, 1962a), the lipid content of the organic fraction is 11 ""r , the lipid is assumed to be 77 ^c carbon (Lasker and Theilacker, 1962), the car- bohydrate fraction is about 2 % . and the carbo- hydrate is assumed to be 40 % carbon (Curl, 1062a). Therefore, the percent carbon in the 106 CLUTTER and THEILACKER: PELAGIC MYSID SHRIMP mysid protein is calculated as: % C (0.08) (0.50) -(0.11) (0.77) L[0.42 -0.79 — (0.02) (0.40)] = 0.364 = 36.4 % This is considerably less than the average value of 52 '( carbon in protein given by Hawk, Oser, and Summerson (1954), but similar to an esti- mate of 37 % made from the data of Lasker (1966), and higher than an estimate of 23 Sr made from the data of RajTiiont et al. (1964). The second step in finding the relationship between chitin and protein in the molts was to estimate the chitin fraction from the following relationship: (chitin fraction) (9f C in chitin) + (protein fraction) (9f C in pi-otein) = (% C in molt) where chitin fraction + protein fraction 1.0. The chitin fraction calculated from this rela- tionship is 44 % for the organic molt. The protein fraction is therefore estimated to be 56 ^,x . This result suggests that a large fraction of the chitin may be reabsorbed by the animals before molting. This seems reasonable because in Crustacea the new endocuticle is formed dur- ing the intermolt period (between 2 % and 46 % of the time between molts, according to Passano, 1960). To estimate the protein content of eggs and larvae, we have made some arbitrary assump- tions that seem reasonable, and that do not measurably affect our energy calculations in any event. We have assumed that the eggs do not contain a measurable amount of carbohydrate, and that they contain little or no chitin because the integument is not yet formed. Therefore, we have assumed that the organic fraction of the eggs is either protein or lipid. For late stage larvae we have also assumed that carbo- hydrate is absent, but that some chitin is pre- sent because they form integument and molt once before they are released. We have as- sumed that the organic fraction of the larvae contains half the amount of chitin as the adults, or 4 %. The protein-lipid composition of the eggs was calculated from the carbon content of the ash- free fraction. We have estimated (above) that 36.4 % of the mysid protein is composed of carbon, that 77 % of the lipid is carbon, and that 61.8 '~r of the ash-free egg is carbon. By using these values we calculate that the organic fraction of the eggs is 62.5 % lipid and 37.5 % protein. The carbon content of intermediate age brood pouch young (about 5 days old) was less than that of eggs and more than that of late stage larvae. For these intermediate age young we calculate a lipid content of 43 %. ENERGY CONTENT Juveniles - Adults The ash-free calorie content of Metamysidop- sis was determined in a Parr non-adiabatic cal- orimeter. The data, converted to ash-free values, are given in Table 4. Three of the samples contained so little material that Nujol supplement had to be added to raise the heat of combustion to a measurable level. All three of these measurements fell outside the 95 % con- fidence limits of the six determinations made without the Nujol supplement. The variability among the three supplemented determinations can be attributed to the ± 2 % variation of the caloric content of the Nujol supplement (10,791 ± 200 cal/g) , because the weight of the supple- ment greatly exceeded the weight of the sample material in each case. Table 4. — Ash-free' caloric content of Metamysidopsis. Specimens Dry weight Calorie content Ms Cal/i Young juveniles 1.0S 23028.9 Juveniles 2.45 =6462.6 Young females 4.80 =4242.3 Advanced juveniles 12.55 5021.7 Immature males 1 7 JO 5049.0 Immature moles 17.30 5358.0 Mature males 15.75 51238 Mature females 12.40 5185.7 Mature females 17.25 5699.1 ^ Ash content 12.5 % used in all calculations. 2 Nujol supplement used in determinotions. 107 FISHERY BULLETIN: VOL. 69, NO. 1 The mean for the six nonsupplemented sam- ples is 5,240 cal/g (shown as 5.24 cal/mg in Table 3). No significant differences in energy content among developmental stages nor be- tween sexes were found. This mean calorie content estimate is some- what lower than those reported for other Crus- tacea. Slobodkin and Richman (1961) gave values of 5.4 to 5.6 cal/ash-free mg; Lasker (1965) reported a range of 4.9 to 5.4 cal/mg (in- cluding ash) for two species of copepods. Our mean value is also lower than the value that can be calculated from the information on body composition, together with reported average values of the calorie content of animal pi-otein, fat, and carbohydi'ate. Conversion factors given by Horowitz (1968) are: protein, 5.5 cal/mg; fat, 9.3 cal/mg; and carbohydrate, 4.1 cal/mg. Since chitin is glucosamine, we have assumed that it, like carbohydrate, has a calorie content of 4.1 cal/mg. From these conversion factors and the composition data given in Table 3, we calculated an expected value of about 5.77 cal/ash-free mg. We use the empirical value, 5.24 cal/ash-free mg, in our subsequent energy budget calcula- tions. We consider this to be a conservative estimate, because it assumes that the mysid pro- tein has an energy content of only 4.8 cal/mg. This lower than expected estimate may be re- lated to the empirical observation that the mysid protein contains only 36 9^ carbon, rather than about 50 % as is commonly assumed for animal protein. The juvenile and adult Metamysidopsis con- tained 12.5 % ash; therefore, the energy in the whole dry body of an adult or juvenile is esti- mated to be: (4.6 cal/mg) x (dry weight, mg). Molts We estimated the energy content of molts in- directly, because it was difficult to obtain enough material for calorie measurements. The ash- free fraction (55 '.i ) of the molts was estimated to be composed of 44 % chitin and 56 9ir protein. By assuming that chitin has an energy content of 4.1 cal/mg, and that the mysid protein has an energy content of 4.8 cal/mg, we calculate that the ash-free fraction of the molts has an energy content of 4.5 cal/mg. From a sample of 10 animals and their molts we found that the dry weight of molts is on the average 13 % (range 9-19 /r) of the dry weight of the animals that shed them. Lasker (1964, 1966) and Jerde and Lasker (1966) found that the dry molts of a euphausiid were about 10 % of the dry weight of the animals that produced them (range 4-14 %). The energy lost by molting Metamysidopsis is thei'efore proportional to the size of the animal: (0.13) (0.55) (4.5 cal/mg) X (dry weight of animal, mg) or (0.32 cal/mg) x (dry weight of animal, mg). Eggs and Larvae We estimated that eggs were 6 ^r ash, 35 % protein, and 59 % lipid. The energy content of an egg is estimated to be: (0.35) (4.8 cal/mg) + (0.59) (9.3 cal/mg) = 7.16 cal/mg. A sample of 140 eggs was dried and weighed; the mean dry weight per egg was 0.0055 mg. The energy content per egg is tlierefore 0.039 cal- orie. We estimated that, just before being released from the brood pouch, the larvae are about 6 % ash, 61 '"r protein, 29 Sr lipid, and 4 ''/c chitin. The energy content of a late stage larva is esti- mated to be: (0.61) (4.8 cal/mg) + (0.29) (9.3 cal/mg) + (0.04) (4.1 cal/mg) = 5.78 cal/mg. The mean dry weight per larva, esti- mated from 110 individuals, was 0.0051 mg. The energy content per larva is therefore 0.029 calorie. ENERGY BUDGET AND EFFICIENCY OF ENERGY TRANSFER From the data on average growth, age-spe- cific fecundity, respiration rate, and energy con- tent we have calculated cumulative curves of energy use by individual mysids in attaining various stages of development. Data on age- specific natural mortality rates (Fager and Clut- ter 1968) were used to estimate Ix (probability 108 CLUTTER and THEILACKER: PELAGIC MYSID SHRIMP of animal being alive at age x) schedules and average generation time of the field population. The field and laboratory data were combined in an analysis of the efliciency of energy transfer through the Metamysidopsis population to the organisms that feed on them. CUMULATIVE ENERGY CURVES At age zero the egg contains about 0.04 cal. Ten days later, at the time it is released from the brood pouch, the larva contains about 0.03 cal. Thereafter the average calorie content in- creases in proportion to the dry weight (4.6 cal/ mg). The average schedules of energy incor- 16 - U - 1 12 - / 10 - / 5 a / >. 1 c 1 respiration 6 - / / 4 2 " ,^ / y//^^.^^'^ growth 1 1 1 10 30 50 70 90 Aga Idon) Figure 12.— Cumulative energy used by individual Meta- mysidopsis females. The curves are additive, i.e. the space between the lower two curves represents the cumulative energy lost in molts, the next higher space represents energy used to produce eggs (both fertilized and unfertilized), etc. — so that the upper curve repre- sents cumulative energy used for all processes. poration differ between males and females after about 30 days; the rate of incorporation becomes lower and levels off sooner in males. The ac- cumulation of body energy is shown as the low- est curves in Figure 12 (females) and Figure 13 (males). The amount of energy lost in molts varies with age because the size of the molt increases and the molting frequency decreases. Females and males have different cumulative losses of energy from molting because their growth rates are different after age 30 days, and their molting frequencies are different (Table 1.) Although the actual loss of energy in molting occurs at discrete intervals, we have plotted the cumula- tive energy loss as smooth curves, because the accumulation of energy for integument forma- tion probably is continuous. Cumulative energy loss in molting is shown as the second curve in Figure 12 (females) and Figure 13 (males). The cumulative energy curves are additive, i.e. the area between the first curve (body energy) and second curve (molting energy) represents the cumulative energy loss in molts. Figure 13. — Cumulative energy used by individual Meta- mysidopsis males. The curves are additive (see Fig. 12) . 109 FISHERY BULLETIN: VOL. 69. NO. 1 Males use a small amount of energy in pro- ducing sperm, but we assume that this is negli- gible. In females, the ova begin to be infused with yolk about age 45 days. The actual dis- charge of eggs occurs at discrete intervals of about 10 days, beginning at age 53 days. We assume that the accumulation of energy for re- production is more continuous than this, there- fore we have shown reproductive energy use as a smooth curve. The reproduction energy curve shown in Figure 12 is based on the maximum fecundity estimate given previously [number of eggs = 4.1 (body length, mm) — 8.9]. A repro- duction energy curve based on our minimum es- timate of fecundity [number of eggs = 4.1 (body length, mm) — 12.0] would be 0.12 cal (3.1 eggs) lower per spawning. This would make the minimum estimate 72 Sr of the maximum estimate at the age of first spawning (53 days) and progressively higher in percentage there- after, e.g. 85 9f at the age of fifth spawning (93 days). All our reproduction energy cal- culations take into account the observation that, on the average, mature females extrude the usual number of eggs only one-half of the time and otherwise extrude only one-half the usual num- ber of eggs. The amount of energy used in respiration was calculated from the weight-specific respiration equation: R' — 2.1 (dry weight, mg)-"'^^ and from energy conversion factors based on our estimates of body composition. We do not know what substrate Metamysidop- sis catabolizes. The organic fraction of the body is largely protein; the storage ])roduct (carbo- hydrate and lipid) content is low. Raymont and Krishnaswamy (1960) observed that the carbohydrate content of Neomysis integer de- creased slightly, from about 1.30 % (of dry weight) to 1.06 ^(, when a marked reduction in feeding occurred. For the same species, Lin- ford (1965) found no significant change in lipid level whether the animals were starved, fed a lipid-free diet, or fed a high lipid diet. Raymont et al. (1968) asserted that N. integer uses pro- tein as an energy source. We agree with Linford (1965) that it seems likely that the mysids must live largely on their daily ingestion. We think that the food they ingest has composition similar to their bodies. Therefore, our energy calculations assume that they use catabolic substrates in proportion to their presence in the body. This is supported by the results of Jawed (1969). To convert the amount of oxygen used in respiration into the equivalent energy lost as heat we have used the following values for calories lost//il Oq con- sumed (Hawk et al., 1954; Prosser, 1950): protein, 4.5 X 10"^; lipid, 4.7 X lO"'; car- bohydrate, 5.0 X 10 ~^ Therefore, our esti- mate of the average amount of energy used in respiration is about 4.5 X 10""'cal /A O2. The cumulative energy used in respiration is shown as the uppermost curve in Figure 12 (females) and Figure 13 (males). The area between that curve and the next lower curve represents the catabolic heat loss. These res- piration data were calculated for a temperature of 16° C, which was the median temperature of the natural environment of Metamysidopsis. Our respiration measurements were made in flowing water during the daylight hours. There- fore, they represent basal metabolism + energy expended in active swimming. There is some evidence (Clutter, 1969) that the mysids may be less active at night, even though they con- tinue to swim at all times. For this reason we think that the field population may use some- what less than this amount of energy in respir- ation. Our estimated rate of energy loss in catabo- lism is higher than that estimated by Jawed (1969) in his study of nitrogen excretion in Neoviysis rayii. He suggested that protein is catabolized in relatively large quantities, there- fore nitrogenous excretion may provide a good estimate of catabolism. He found an average catabolism of about 2.5 % of body nitrogen per day in adult animals that were probably 8 to 10 mg dry weight, that were held at 10° C. The rate for adult Metamysidopsis of average size (0.6-0.8 mg) was 5 to 6 % of the body energy i)er day. This disparity in catabolism may result from diff'erences between the size and between the environmental temperatures of the two species. Jawed (1969) showed that about 15 % of the nitrogen was excreted as amino acids. We did 110 CLUTTER and THEILACKER: PELAGIC MYSID SHRIMP not investigate this in Metamysidopsis, there- fore, our estimate of total catabolism could be slightly low because it includes only losses of heat energy. NET ECOLOGICAL EFFICIENCY Mortality and Generation Time Estimates of natural mortality in the field population were made during the same period that the laboratory growth experiments were done (Fager and Clutter, 1968). Brood pouch mortality rate was estimated to be 0.013/ day (maximum of 0.017/day). Mor- tality rates for juveniles, immatures, and adults were estimated from consecutive series of field collections. The field mortality rates varied during the year. Survival curves (Ix = proba- bility of being alive at age x) for periods of at least mortality, median mortality, and great- est mortality are shown in Figure 14. The mor- tality rates that we used to calculate these Ix curves are shown in Table 5. The greatest mortality rate results in a declining population; at the median mortality rate the population size remains about constant; and at the least mor- tality rate the population increases. An average female first reproduces at about age 53 days. The generation length for the population is somewhat longer because the fe- males reproduce more than once. The gener- ation length for the field population varied be- tween 67 days and 71 days; the median was 68 days (Fager and Clutter, 1968). Figure 14. — Age specific survival (l^ = probability of being alive at age x) of Metamysidopsis calculated from estimates of greatest, median, and least mortality in the field population (Table 5). Table 5. — Mortality rates (per day) used to calculate Ir schedules for the Metamysidopsis field population. Least Median Greatest Specimens mortality mortality mortality Brood pouch young 0.013 0.013 0.017 Juveniles 0.02 0.06 0.15 Immatures 0.02 0.05 0.14 Adults 0.02 0.04 0.13 Relative Energy Use by Individuals We determined the calories of energy used by average individual female and male mysids, and the fractions used for growth, molting, re- production, and respiration from the estimates of cumulative energy use (shown in part in Figures 12 and 13). The amounts and the per- centage distributions required to reach selected stages of development are shown in Table 6. Table 6. — Energy used by individual Metamysidopsis to reach selected stages of development. Age Energy Relative use Respira- tion Repro- duction Molt, ing Growth Days Cat % % % % Females: Egg yolk production First reproduction Generation i^ = 0.0 1 45 53 68 1103 2.7 4.6 8.7 18.4 52 49 50 55 9 15 19 8 7 7 7 40 35 28 19 Males: Maturity /^ = 0.01 48 1103 3.0 12.8 54 67 10 12 36 21 * Approximate age at which l^ = 0.01 in a nearly stable population (r-».0). Ill FISHERY BULLETIN: VOL. 69. NO. 1 The indicated age at which the probability of being alive reaches 0.01 applies to the stable population (median death rates). The males require less energy to reach ma- turity than females, but relatively more of this energy goes into molting and respiration and less is incorporated. Two-thirds of the energy used in reproduction remains in the population; one-third is lost as unfertilized eggs. The estimates of relative use of assimilated food by Metamysidopsis females during a life span are compared with estimates for a copepod and a euphausid (Corner, Cowey, and Marshall, 1967) in Table 7. The mysids apparently use a fraction of assimiliated energy for growth that is intermediate between the other two species, a lower fraction for metabolism, and a higher fraction for producing eggs. Table 7. — Use of assimilated food by Metamysidopsis females (life span 103 days) compared with the copepod Calanus finmarchicus^ (life span 10 weeks) and the euphausid Euphausia pacifica' (life span 20 months). Assimiloted energy used by Metamysidopsis Assimilated N used by Calanui Assimiloted C used by Euphausia Growth % 19 % 25.3 % 10.1 Metabolism 55 61.4 72.3 Molts 7 0.9 \6.6 Eggs 19 12.4 1.0 * From Corner, Cowey, and Morshcll (1967). - From Losker (1966), revised in Corner et al. Relative Energy Use by the Population The values of relative energy use given in Tables 6 and 7 apply to individuals, or to pop- ulations wherein all members live a full life span. They do not apply to the natural popu- lation, because some die during all stages of growth. We have estimated the relative amounts of energy that would be lost by populations in res- piration, production of infertile eggs, molting, and mortality at the observed minimum, median and maximum mortality rates shown in Table 5. This was done by calculating the fraction of the population that died during each intermolt period (A/^), and multiplying this times: (1) the mean body energy content for the midpoint of that period, (2) the quantity of cumulative energj' lost in infertile eggs \x\) to the midpoint of that period, and (4) the quantity of cumula- tive energj' used in respiration up to the mid- point of that period. The product values for each of these loss categories (mortality, molting, etc.) were then summed over all ages (to Zx ^ 0.001). The relative energy use values were calculated as fractions of the overall sum for all categories combined. We excluded fertilized eggs because this reproduction energy is retained in the population. The age specific distribution of energy use (representing energy loss, because fertilized eggs are excluded) by a population (females and males) of Metamysidopsis at the median mortality rate is illustrated in Figure 15. All the curves are plotted with reference to the base line, zero. The rate of energy loss is low among eggs and larvae, and much higher among the juveniles that have just emerged from the brood pouch and begun to swim. In the larger animals, the respiration per unit weight is low- er, but the respiration per animal is higher, so that the respiration rate per day is highest among the animals that are about 25 days old. The loss of energy per day from all causes is highest among the animals that are about 30 days old. After this the curve declines because the effect of larger size becomes less than the effect of smaller numbers. The estimated relative amounts of energy lost by the population of females, males, and both sexes combined, for each loss category and Ao* Id Figure 15. — Age specific distribution of energy loss by a Metamysidopsis population at the median mortality rate. Production of fertilized eggs is excluded. 112 CLUTTER and THEILACKER: PELAGIC MYSID SHRIMP for each of three mortality rates, are shown in Table 8. The percentages for females and males combined are not quite the same as the means of the separate pei-centages for females and for males. At the minimum death rate 55 S^ of the energy loss would pass through the female half of the population (58 ^'r if fertile eggs are in- cluded). At the median death rate 52 Sr would pass through the females, and at the maximum death rate, 50 %. Table 8. — Relative amount (%) of energy lost by Metamysidopsis populations in respiration, production of infertile eggs, molting, and mortality; at minimum, median and maximum mortality rates. Sex Death rate Respira- tion Infertile eggs Molting Mortality % % % % Females minimum 63.7 6.7 8.6 20,9 median 55.6 3.7 7.7 33.0 maximum 45.4 0.1 6.1 48.4 Moles minimum 67.4 0.0 12.6 20,0 median 58.3 0.0 9.9 31.8 maximum 47.9 0.0 6.5 45,6 Females and minimum 64.5 3.7 10.4 20,5 Males median 56.9 1.9 8.8 32,4 maximum 46.7 0.1 6.3 47.0 If we assume that all the mortality is yield to predators (Odum and Smalley, 1959; Engel- mann, 1961), our mortality fractions are an estimate of net ecological efficiency (energy yield/energy assimilated). Apparently some Crustacea regularly die from natural causes other than mortality (e.g. Daphnia, Slobodkin, 1959). Many mysids of all ages died in our laboratory cultures, but we do not attribute this to senescence. In the field and in the laboratory we observed Metamysidopsis much older than the oldest animals that are involved significantly in our energy calculations. Our best estimate of the net ecological efficiency of the mysid pop- ulation, for transfer of energy to a higher troph- ic level, such as fishes, is about 32 'Jr. The net efficiency of transfer to all trophic levels is 1 — respiration fraction = 43 S^- ASSIMILATION AND GROSS ECOLOGICAL EFFICIENCY Assimilation Efficiency Gross ecological efficiency (energy yield/en- ergy ingested) is the product of net ecological efficiency (energy yield/energy assimilated) X assimilation efficiency (energy assimilated/en- ergy ingested). Therefore, an estimate of as- similation efficiency is required to estimate gross ecological efficiency for the mysid population. We attempted to estimate the assimilation ef- ficiency of Metamysidopsis directly by a carbon- 14 method described by Lasker (1960). This failed because .the mysids did not filter sufficient amounts of radioactive phytoplankton. An ex- periment with another member of the family Mysidae, taken from the same area, was suc- cessful. This gave an estimate of 90 Tr assim- ilation efficiency. Lasker (1966) obtained a similar high value (84 Cf ) for the morphologically similar Eiiphau- siapacifica; and Marshall and Orr (1955) found values greater than 90 % for the copepod Cal- ami^ finmarchicm. In his detailed reviews of assimilation in zooplankton, Conover (1964, 1966) suggests that these values probably are too high. The very large number of observa- tions, many of them his own, that are cited by Conover seem to be evidence that, although var- iable, the mean assimilation efficiency for crus- tacean zooplankton is at least 60 % and perhaps greater. Gross Ecological Efficiency From the information presently available we consider that the assimilation efficiency of the mysids is between 60 9f and 90 ^r. Our best estimate of net ecological efficiency (yield/as- similated) is 32 Sf. Therefore, the minimum estimate of gross ecological efficiency (yield/in- gested) is 19 9r and the maximum estimate is 29 ^c. These estimates are well within the broad range of available estimates of gross ecological efficiency (see reviews by Patten, 1959; Slobod- kin, 1961; Phillipson, 1966; Reeve, 1966), and within the range of 8 '^'r to 30 'c that Engel- mann (1961) considers to be acceptable. They are about 2 to 3 times as high as the median value of 10 % that is suggested by Slobodkin (1961, 1962) , but lower than the values of 30 % to 50 % suggested for marine zooplankton by 113 FISHERY BLXLETIN: VOL. 69, NO. I Ketchum (1962), Steemann Nielsen (1962), and Curl (1962b). LITERATURE CITED Bartlett, M. S. 1949. Fitting a straight line when both variables are subject to error. Biometrics 5(3), 207-212. Beers, John R. 1966. Studies on the chemical composition of the major zooplankton groups in the Sargasso Sea off Bermuda. Limnol. Oceanogr. 11(4) : 520-528. Bertalanffy, Ludwig von. 1951. Metabolic types and growth types. Amer. Natur. 85(821) : 111-117. Blegvad, H. 1922. On the biology of some Danish gammarids and mysids. (Gammarus locusta, My sis flexiiosa, Mysis neglecta, Mysis inermis). Rep. Dan. Biol. Sta. 28, 103 p. Clutter, Robert I. 1965. Self-closing device for sampling plankton near the sea bottom. Limnol. Oceanogr. 10(2) : 293-296. 1967. Zonation of nearshore mysids. Ecology 48(2) : 200-208. 1969. The microdistribution and social behavior of some pelagic mysid shrimps. J. Exp. Mar. Ecol. 3(2) : 125-155. CoNOVER, Robert J. 1960. The feeding behavior and respiration of some marine planktonic Crustacea. Biol. Bull. 119(3) : 399-415. 1964. Food relations and nutrition of zooplankton. In Experimental marine ecology, p. 81-91. Grad. Sch. Oceanogr. Univ. R.I., Occas. Publ. 2. 1966. Assimilation of organic matter by zooplank- ton. Limnol. Oceanogr. 11(3): 338-345. Corner, E. D. S., C. B. Cowey, and S. M. Marshall. 1967. On the nutrition and metabolism of zooplank- ton. V. Feeding efficiency of Calanus finmarch- icus. J. Mar. Biol. Ass. U. K. 47(2): 259-270. Curl, Herbert, Jr. 1962a. Analyses of carbon in marine plankton or- ganisms. J. Mar. Res. 20(3): 181-188. 1962b. Standing crops of carbon, nitrogen and phosphorus and transfer between trophic levels, in continental shelf waters south of New York. Rapp. Proees-Verbaux Reunions, Cons. Perma. Int. Explor. Mer. 153: 183-189. Engelmann, Manfred D. 1961. The role of soil arthropods in the energetics of an old field community. Ecol. Monogr. 31(3) : 221-238. Eager, E. W., and R. L Clutter. 1968. Parameters of a natural population of a hypopelagic marine mysid, Metamysidopsis elon- gata (Holmes). Physiol. Zool. 41(3): 257-267. Eager, E. W., A. O. Flechsig, R. F. Ford, R. I. Clutter, AND R. J. Ghelardl 1966. Equipment for use in ecological studies using SCUBA. Limnol. Oceanogr. 11(4) : 503-509. Grainger, J. N. R. 1956. Effects of changes of temperature on the respiration of certain Crustacea. Nature (Lond- on) 178(4539) : 930-931. Hawk, Philip B., Bernard L. Oser, and William H. summerson. 1954. Practical physiological chemistry. 13th ed. McGraw-Hill, New York, xvi -f 1439 p. Hensen, V... 1887. Uber die Bestimmung des Plankton's oder des im Meere treibenden Materials an Pflanzen und Thieren. Ber. Komm. Wiss. Unters. Deuts. Meere, Kiel. 5: 1-107. Jawed, Mohammad. 1969. Body nitrogen and nitrogenous excretion in Neomysis rayii Murdoch and Enphatisia pa- cifica Hansen. Limnol. Oceanogr. 14(5) : 748-754. Jerde, Charles W., and Reuben Lasker. 1966. Molting of euphausiid shrimps: Shipboard observations. Limnol. Oceanogr. 11(1) : 120-124. Kanwisher, John. 1959. Polarographic oxygen electrode. Limnol. Oceanogr. 4(2) : 210-217. Ketchum, Bostwick H. 1962. Regeneration of nutrients by zooplankton. Rapp. Proces-Verbaux Reunions, Cons. Perma. Int. Explor. Mer 153: 142-147. Krebs, H. a., and H. L. Kornberg. 1957. Energy transformations in living matter, a survey. Springer, Berlin, p. 212-298. Krogh, August. 1934. Conditions of life at great depths in the ocean. Ecol. Monogr. 4(4): 430-439. KURATA, HiROSHI. 1960. Increase in size at moulting in Crustacea. Bull. Hokkaido Reg. Fish. Res. Lab. 22: 148. [In Japanese with English summary.] Lasker, Reuben. 1960. Utilization of organic carbon by a marine crustacean: Analysis with carbon-14. Science 131(3407) : 1098-lioO. 1964. Moulting frequency of a deep-sea crustacean, Euphausia pacifica. Nature (London) 203 (4940) : 96. 1965. The physiology of Pacific sardine embryos and larvae. Calif. Coop. Oceanic Fish. Invest. Rep. 10: 96-101. 1966. Feeding, growth, respiration, and carbon utilization of a euphausiid crustacean. J. Fish. Res. Bd. Can. 23(9) : 1291-1317. Lasker, Reuben, and Gail H. Theilacker. 1962. The fatty acid composition of the lipids of some Pacific sardine tissues in relation to ovarian maturation and diet. J. Lipid Res. 3(1) : 60-64. 1965. Maintenance of euphausiid shrimps in the 114 CLUTTER and THEILACKER: PELAGIC MYSID SHRIMP laboratory. Limnol. Oceanogr. 10(2): 287-288. LiNFORD, Eileen. 1965. Biochemical studies on marine zooplankton. II. Variations in the lipid content of some Mysi- dacea. J. Cons. Cons. Perma. Int. Explor. Mer 30(1): 16-27. Manton, S. M. 1928. On the embryology of a mysid crustacean, Hemimysis lamomae. Phil. Trans. Roy. Soc. London, Ser. B 216: 363-463. Marshall, S. M., and A. P. Orr. 1955. On the biology of Calanus finmarchicxis. VIII. Food uptake, assimilation and excretion in adult and stage V Calanus. J. Mar. Biol. Ass. U.K. 34(3): 495-529. Mauchline, J. 1967. The biology of Schistomysis spirittis [Crus- tacea, Mysidacea] . J. Mar. Biol. Ass. U.K. 47(2): 383-396. MoRowiTZ, Harold J. 1968. Energy flow in biology. Academic Press, New York, ix -f- 179 p. Nair, K. Bhaskaran. 1939. The reproduction, oogenesis and develop- ment of Mesopodopsis orientalis Tatt. Proc. In- dian Acad. Sci., Sect. B 9(4): 175-223. NouvEL, Henri, and Louise Nou\'el. 1939. Observations sur la biologie d'une Mysis: Praunus flexuosus (Miiller, 1788). Bull. Inst. Oceanogr. Monaco 761, 10 p. Odum, Eugene P., and Alfred E. Smalley. 1959. Comparison of population energy flow of a herbivorous and a deposit-feeding invertebrate in a salt marsh ecosystem. Proc. Nat. Acad. Sci. U.S.A. 45(4) : 617-622. Omori, Makoto. 1969. Weight and chemical composition of some important oceanic zooplankton in the North Pa- cific Ocean. Mar. Biol. 3(1): 4-10. Passano, L. M. 1960. Moulting and its control. In Talbot H. Waterman (editor), The physiology of Crustacea. Vol. 1, p. 473-536. Academic Press, New York. Patten, Bernard C. 1959. An introduction to the cybernetics of the ecosystem: The trophic-dynamic aspect. Ecol- ogy 40(2): 221-231. Phillipson, John. 1966. Ecological energetics. St. Martin's Press, New York. 57 p. Prosser, C. Ladd (editor). 1950. Comparative animal physiology. W. B. Saunders Company, Philadelphia, ix -|- 888 p. Raymont, J. E. G., J. Austin, and Eileen Linpord. 1964. Biochemical studies on marine zooplankton. 1. The biochemical composition of Neomysis integ- er. J. Cons. Cons. Perma. Int. Explor. Mer 28(3) : 354-363. 1966. Biochemical studies on marine zooplankton. III. Seasonal variation in the biochemical compo- sition of Neomysis integer. In Harold Barnes (editor), Some contemporary studies in marine science, p. 597-605. George Allen and Unwin Ltd., London. 1968. Biochemical studies on marine zooplankton. V. The composition of the major biochemical fractions in Neomysis integer. J. Mar. Biol. Ass. U.K. 48(3): 735-760. Raymont, J. E. G., and Robert J. Conover. 1961. Further investigations on the carbohydrate content of marine zooplankton. Limnol. Ocean- ogr. 6(2) : 154-164. RAY.MONT, J. E. G., AND S. Krishnaswamy. 1960. Carbohydrates in some marine planktonic animals. J. Mar. Biol. Ass. U.K. 39(2) : 239-248. Reeve, M. R. 1966. Observations on the biology of a chaetognath. In Harold Barnes (editor). Some contemporary studies in marine science, p. 613-630. George Allen and Unwin Ltd., London. Slobodkin, L. Basil. 1959. Energetics in Daphnia pulex populations. Ecology 40(2): 232-243. 1961. Growth and regulation of animal populations. Holt, Rinehart and Winston, New York, viii -|- 184 p. 1962. Energy in animal ecology. In J. B. Cragg (editor), Advances in ecological research. Vol. 1, p. 69-101. Academic Press, London. Slobodkin, L. B., and S. Richman. 1961. Calories/gm. in species of animals. Nature (London) 191(4785): 299. Steemann Nielsen, E. 1962. The relationship between phytoplankton and zooplankton in the sea. Rapp. Proces-Verbaux Reunions, Cons. Perma. Int. Explor. Mer 153: 178-182. Tate, Merle W., and Richard C. Clelland. 1957. Nonparametric and shortcut statistics. In- terstate Publishers and Printers, Inc., Danville, 111. ix 4- 171 p. Vinogradov, A. P. 1953. The elementary chemical composition of marine organisms. Mem. Sears Found. Mar. Res. 2, xiv -f 647 p. 115 A LINEAR-PROGRAMMING SOLUTION TO SALMON MANAGEMENT' Brian J. Rothschild^ and James W. Balsiger" ABSTRACT A linear-programming model was constructed to allocate the catch of salmon among the days of the salmon run. The objective of the model was to derive a management schedule for catching the salmon which would result in maximizing the value of the landings given certain constraints. These con- straints ensured that cannery capacity was not exceeded, and that escapement of both male and fe- male fish was "adequate." In addition to considering the allocation of the catch in the primal problem, the dual problem considered the shadow prices or marginal value of the various sizes of fish, eggs, and cannery capacity, thus enabling the manager to view his decisions in light of the marginal values of these entities. As an example, the model was applied to a run of sockeye salmon in the Bristol Bay system. In the particular example, which was chosen to replicate the 1960 run, the additional value of the catch owing to optimality amounted to an ex-vessel value of a few hundred thousand dollars. In addition it appeared that the required processing time could be reduced by several days. The op- timum allocation was obtained through conformance to the linear-programming model. The cost of this conformance was not, however, determined. The Pacific salmon fisheries have been cited as an example of irrational conservation (Crutch- field and Pontecorvo, 1969). Much of this ir- rationality is reflected in the dissipation of a sizable fraction of the available economic rent, a situation which results from the open- access nature of the fishery and legislated in- efficiency. The remedy for this situation is to alleviate the open-access and inefficiency problem. Such alleviation would require the dissolution of rather formidable institutional problems. In the present paper, we examine the salmon problem from a slightly different vantage point than Crutchfield and Pontecorvo. We examine the salmon problem under the status quo; we do not consider the optimal amount of gear or its efficiency (this should not, however, be construed as reflecting any diminution in the importance of these prob- lems); rather we consider, as an interim ap- proach, whether it is possible, under the strin- gent condition of knowing in advance the structure of the run, to increase the value of the fish on the dock by optimally allocating the ' Contribution No. 333, College of Fisheries, Uni- versity of Washington. " Center for Quantitative Science and Fisheries Re- search Institute, University of Washington, Seattle, Wash. 98105. ' Fisheries Research Institute, University of Wash- ington, Seattle, Wash. 98105. catch among the days of the run. The traditional approach to salmon manage- ment might be considered, at the risk of several simplifications, as consisting of (1) forecasting the magnitude of the run ; (2) setting an escape- ment goal and a catch implied by the forecast and the escapement; and (3) daily fishing closures and other devices which allocate the catch in varying quantities to the days of the run. The traditional approach, then, also in- volves an allocation of the catch to the days of the run. In the traditional approach, the allocations are usually based on the experience of management biologists. Although the ob- jectives of their allocations are not always clearly and explicitly stated, there is a tendency for the primary objective of management to be simply the attainment of the escapement goal. Our approach is to use the theory of linear pro- gramming to advise on a non-intuitive optimum allocation of the salmon catch among the days of the run where the objective of management does not explicitly involve escapement. Rather, we develop our allocation strategy to maximize the value of the catch on the dock given a va- riety of constraints which include the necessity for a given number of fish to escape the fishery. The objective of maximizing the value of the fish on the dock and the constraints explicitly define the objectives of the management scheme. Manuscript received October 1970. FISHERY BULLETIN: VOL. 69. NO. I, 1971. 117 FISHERY BULLETIN; VOL, 69. NO. I We consider these problems in three additional sections. In the first, we describe the linear- programming allocation model, which we be- lieve to be applicable, with simple modifications, to a variety of salmon management situations. In the second, we consider how the model might be applied to a run of salmon in the Naknek- Kvichak system of Bristol Bay, Alaska. As an example, we choose data from the 1960 run to that system and obtain an optimum allocation of large and small, male and female fish, on each day of the run to the daily catch. This optimum allocation served to maximize the value of the fish on the dock subject to constraints which ensured that the catch did not exceed the daily run, that the catch would be less than the can- nery capacity, and that an "adequate" escape- ment, both in terms of the number of eggs and sex ratio, passed the fishery. Thus, in addition to managing the run by a non-intuitive optimum allocation and satisfying an escapement goal, we also considered the quality of the run in terms of its sex and age composition. In order, how- ever, to achieve this optimum allocation we needed certain data on the structure of the run in advance and we also needed a mechanism by which we could select large and small male and female fish. It would most likely be im- practical to have either a precise prediction of the daily run or an ability to select, with high precision, large or small, male or female fish. We show that even if we had the necessary data, a technique for precise selection of the various entities of fish, and maintained the 1960 escape- ment and sex-ratio conditions, optimum alloca- tion would yield us a catch having a value of several hundred thousand dollars more than the actual catch. Thus given the cost of obtaining the necessary information to perform the op- timum allocation and the constraints extant in 1980, it is questionable whether biological man- agement could yield a better allocation than that which was obtained. This serves to re-empha- size the approach of Crutchfield and Pontecorvo, indicating that the system is most sensitive to variables which lie outside the objective and constraint equations specified in the present paper. On the other hand, our results show that it is possible, at least in terms of the model. to reduce the number of days during which the cannery operates and yet process the same num- ber of fish. Furthermore as previously indicated, we constrained our example to fit the statistics of the 1960 run and thus we had, in our ex- ample, a nearly 1:1 sex ratio; but as we indi- cate later, we could have caught a considerably larger number of male fish and still would have had sufficient male fish in the escapement to en- sure the efficient production of fertilized eggs. And finally the model was quite sensitive to de- creasing the escapement but unfortunately there is little guidance in the literature which would indicate the optimum escapement for the Nak- nek-Kvichak system and furthermore there ap- pears to be little hope of learning the magnitude, in the reasonably near future, of the optimum escapement for the Naknek-Kvichak system. Thus evaluation of the cannery processing time, catch problem, and relaxation of sex ratio and escapement constraints might result in an ad- ded value to the catch which would make some attempts at allocation practical. We also, in the second section, place some stress on in- terpretation of the shadow prices of the var- ious variables in the problem. This is of in- terest to operations researchers because it provides an example, in addition to those con- ventionally used, of an application of the inter- pretation of the linear-programming primal- dual relation. The shadow prices are of interest to the fishery manager because from them it is possible to impute values to the various resources under the manager's control, and, in making a decision, the manager can thus consider these values which, as we show, are not always intui- tively obvious. In the third and final section we conclude the paper with a general discussion of salmon management in a linear-programming setting. MODEL Most linear-programming models generally involve finding values A'j which maximize (or minimize) an objective function i;r,A',-, subject to a set of constraints each of which has the form :^PiXi « Lj, where the inequality can be in either direction or can, in fact, be an equality. 118 ROTHSCHILD and BALSIGER: LINEAR-PRCXSRAMMING SOLUTION The Pi's and the L/s are constants appropriate to a particular problem. The details of the LP (linear-programming) procedure can be found in the many treatises on the subject (e.g., Gass, 1964) or in most texts on operations research (e.g., Hillier and Lieberman, 1967). In our application of the LP model, we max- imize the following objective function A/ N Z = I Z CijXij, (1) where M refers to the total number of age-sex categories and N refers to the days of the run. The variable A',,- is the number of fish caught in the ith entity on the jth day of the run and cij corresponds to the value of the fish caught in the ith entity on the yth day (Table 1). The age-sex category classification results from the fact that salmon runs are comprised of a va- riety of age-groups. Because each age-group is usually of a different average size, the indi- Table 1. — Linear program model notation. Af — The total number of age-sex categories. N — The total number of days in the run. Xij — The number of fish in the t'th oge-sex category which are caught on day ; of the run. C-- — The value of a fish caught in the tth oge-sex category on day y of the run. R — The number of fish in the ith age-sex category which run past the fishery on day ; of the run. Kj — The copocity, in numbers of fish, of the canneries on day ;' of the run, K — The total seosonol copocity of the canneries in numbers of fish, J¥^j — The number of fish of the ith oge-sex category in the escape- ment on day ;' of the run. a — The overage number of eggs in each fish of the ith oge-sex category. T — The total number of eggs contained in the escopement and catch. £ — The minimum number of eggs required in the escapement, ^ — The totol number of moles in the escapement and catch. F — The average fecundity of the female oge-sex cotegories, ex- pressed in number of eggs, f{ — The sex ratio desired in the escapement, expressed as the number of females per mole. /.,- — The number of fish of the ith oge-sex category desired in the season's escapement. S — The number of fish in the totol season run of the ifh oge-sex category, P(j) — The proportion of the run thot arrives by doy ; of the run. P' (j) — The proportion of the run that orrives on day > of the run. viduals in each age-group also have a different average value which we denote by cij. It should be mentioned that size is not the only criterion which can be used for classification. For ex- ample, in the Naknek-Kvichak run of Bristol Bay, the sex of the fish can also be used be- cause within an age-group the male fish tend to be larger than the female fish and thus more valuable in terms of weight of fish-flesh; but, on the other hand, the eggs of the females are a valuable commodity and thus the per-pound value of females may be greater than the per- pound price of males. If the value of the fish were constant during the course of the run, we could replace the C;j with Cj and the allocation problem would become rather uninteresting. But the value, however, does tend to vary dur- ing the course of the run. One reason for this is a deterioration of the quality of fish, as in- dicated by declining oil content and reduction in color intensity with the progression of the run. Another way in which Cy could vary is that the average value of the fish on a par- ticular day would tend to vary during the course of the run because of a within-entity trend in the average size of the fish during the course of the run; this, however, is not considered in the present paper. It is obvious that, if we had sufficient information, we could establish a large number of different c,/s. As indicated previously, equation (1) is max- imized subject to a variety of constraints. For the salmon problem, the first set of constraints is rather obvious and constrains the catch, of any entity, on any day, to be less than, or equal to, the number of fish in that entity in the run. These constraints are of the form -namic programming or apply the outlined procedure in real time to handle the static nature of the programming problem, but unfortunately these approaches will present what can be quite complicated computational difficulties which may, in some instances, be in- surmountable. It is thus clear that we have made certain approximations, trading off real- ism for an easily computable solution which certainly provides management guidance. As we implied previously, we do not consider our departures from realism to seriously affect the utility of the model to provide guidance for decision making. Thus we believe that, for ex- ample, fixing the cannery capacity independent of the entities involved (or we could consider the cannery capacity to be fixed at a level which would accept a reasonable mixture of the en- tities) or using a simple average fecundity of the female entities to represent the average fecundity of the spawning females materially affects our conclusions. These, however, can be evaluated in direct applications by a sensi- tivity analysis. Having outlined some cautions with respect to assumptions, we can now examine some of the indications provided by the various trials of the procedure. These involve the value of the fish on the dock, a reduction in processing-season length, changing value of entities during the run, and finally future data needs. First with respect to the value of the total catch on the dock, we experimented with three value functions which set the daily value of each entity. Using the value functions to determine the value for each entity and day, and the actual distribution of the catch over the 1960 season, a total value of the catch was calculated which corresponds to the use of each of the three value functions. These values of the actual allocation of the catch were compared with the value of the optimal allocation as determined by the linear program as an indication of the value of op- timally allocating the catch over the season. The increased value of the optimally allocated catch ranged from approximately $350,000 to $420,000 dependent on which value-function curve was considered. Table 3 shows these results. In the table, a fourth value function is indicated, which is simply a straight-line function such that the value of each entity remained constant through the season. Each of the other value functions was determined such that the average value of each curve was equal to the constant value for that entity for the season. Table 3. — Comparison of the value of the optional al- location with the value of the actual allocation of the catch for the 1960 season. Value function P Value function 2^ Value function 3^ Value function 4* Optimal allocation Actual allocation $13,787,050 13,378,650 $13,927,860 13,506,250 $13,792,555 13,439,825 $13,517,870 13,517,890 Increased value $ 408,400 $ 421,610 $ 352,730 $ 'i-20 ^ After doy 6, the price dropped 3(f per pound. 2 The price was reduced by subtracting a logistic curve that reduced the price of eoch entity by 3tf per pound over the season. ^ The price was reduced by subtracting a quodratic curve that reduced the price of each entity by 3^ per pound over the season. * The price for each entity remained constant through the season (actual situation.) ^ Difference due to rounding in the linear programming algorithm. All three value functions had the effect of placing emphasis, in the optimal solution, on catching fish on the early days of the season. For tw'o of the functions the value for any entity of fish on a given day is less than the value for that entity on the previous day. This is not true in the step function and thus we do not have a unique allocation, but rather a set of alloca- tions under the high values and a set of allo- cations under the low values. But results are exactly the same; optimal allocations of fish are identical under the three value functions, al- though the total value of the catch changes some- what, according to the exact shape of the value- function curve. Again, we emphasize that these gains from allocation can only be obtained by 135 FISHERY BULLETIN: VOL. 69. NO. 1 knowing in advance of the run the information that we actually used in the allocation and having the ability to select the entities in the run as they are selected in the allocation. Next, an examination of the 1960 optimal allocation reflects that this optimal allocation not only increases the value of the fish on the dock, it also shortens the length of time which a cannery needs to operate. Thus, the same amount of fish could be processed in a shorter period of time, by the same labor force, etc. In the optimal allocation for the 1960 run, all of the fish could have been processed in the first 13 days of the season, 5 days less than the actual operation. Naturally, we need to assume that a policy of catching salmon only from the early part of the run would not aff"ect the genetic constituency of the stock. Furthermore, we must be careful here because, as we have em- phasized in several places, by our LP assump- tions, we cannot, a priori, let the cannery oper- ations on day ;/-l, for example, affect the can- nery operations on day / and we cannot at least in our formulation allow operating at peak ca- pacity to affect quality of the fish or overtime payments since the variables are external to our model. Another indication is that the values of fish change during the course of the season and that these values change in rather subtle ways de- pending upon the "rules" that we set forth (e.g., contrast Figures 8 and 9) and that in the fishery the marginal value of less valuable entities in Table 2 can be greater than the more valuable entities in Table 2. These changes in values need to be acknowledged in any management scheme. Thus, it appears that we have the opportunity to increase the economic efliciency of some salm- on runs. This is, of course, not a new concept, having been treated in some detail by, for ex- ample, Crutchfield and Pontecorvo (1969). Our approach is slightly different, however, in that we have concentrated on oiitimality only from the point of view of increasing the value, as we have defined it, of the fish on the dock. Any full treatment of the management problem must, of course, consider the distribution of fishing eff'ort and its ancillary fishing and economic implica- tions. Now if we accept the premise that conserva- tion is "optimum" allocation of resources in the times-space stream (c.f. Crutchfield and Ponte- corvo, 1969), and if we observe that mathema- tical programming provides guidance for optimal allocation, and note that LP is a special case of mathematical programming, and suggest that the kinds of information required to allocate salmon among the days of the run in an LP model are not going to be much different from the kinds of information required for more so- phisticated programming procedure, then we are led to the conclusion that perhaps we have not addressed ourselves to asking, in our research, the "right questions" concerning salmon man- agement. Following our argument, it would then be implicit that the right questions are con- tained in our formulation of the LP model. These answers must be feasible to obtain and they would contain either needed data or doc- umented policies which would be reflected in the right-hand side of the constraint ecjuations and, more importantly, provide an opportunity for enlightened dialogue. There is unfortu- nately a cost associated with asking right ques- tions. This cost involves the cost of doing new work, or that which inevitably results when ex- isting research activities are reallocated. Are these costs worth the expenditure? These, how- ever, are the kind of questions, the answers to which can be guided by the LP problem. For the salmon management model, we impute values to units of cannery capacity, etc., but, and per- haps of equivalent importance, we impute a val- ue, in meaningful terms, to information. Thus, for our salmon jn'oblem, we have cleverly avoid- ed indicating how we could catch Xij fish for some /,,/. But it is well known that catching can be approximated because it is i)ossible to catch salmon in traps (although this has never been done to any large extent in Bristol Bay) and, upon visual inspection, to distinguish between large and small, male and female fish, and doing this by virtue of ceteris paribus, the allocative process, we could add about 0.5 million dollars to the value of the salmon on the dock. This is, of course, not the full picture, because we would have to trade off the added value of salmon (it 136 ROTHSCHILD and BALSIGER: LINEAR-PROGRAMMING SOLUTION is a common opinion that salmon caught in traps are of better condition and higher vahie than the salmon which are taken by gill netting, for example), the reduction in cannery days used to process the fish, the cost of building traps, and the political problems which are described in some detail in Crutchfield and Pontecorvo (1969). It would not, however, be dithcult to determine the discounted present value of the various alternate ijrocedures and thus evaluate the wisdom of engaging in any. In this eval- uation, we need not be bound by what are per- haps extreme solutions such as traps, but we could examine the value of other selectivity pro- cedures such as modifying gill net selectivity, etc. In general, then, we can evaluate the value of information by approximating that informa- tion, employing it in the model, and contrasting the change in the objective function with the objective function when the information is not in the model. Additional information is needed on the pat- tern of the run. For the earlier years, this is available in Royce (1965), a publication which needs to be updated and implemented to obtain even rough estimates of the temporal movement of the fish of various entities through the fishery. This might be quite difficult to accomplish with present concepts, and the feasibility of a system which would acoustically monitor the passage of salmon through the entire river system and developing a central computer-oriented unit which would process the signals from all acoustic units and provide, in real time, through appro- priate algorithms, rules for catching fish and making observations on escapement is presently being explored. In our model, because of a lack of information, we used the total run and allocated this propor- tionately among the days of the fishery to de- termine the daily run. This emphasizes the need to have, for the purpose of management, a fairly accurate preseason guess of the total magnitude of the run and the Xij's. These guesses are already being made and the predictions need to be judged on the basis of whether the pre- dictions do better than simply averaging the run for cycle years and simply averaging the run for noncycle years and applying these aver- ages as predictions. The trick then may not be to estimate the average catch but rather to de- termine which years are cycle years. We have included cannery capacity in a rather simple way in our model and this is a subject that also needs additional data since the can- nery capacity constraint can be formulated in a variety of ways. It would be interesting to explore in a simulation setting the behavior of the slack variables in the cannery constraint. This is because it seems quite likely that there is a positive correlation between the cost of op- erating a cannery and the magnitude of the slack variable in the cannery constraint. If the run was constant from year to year, then it would be relatively easy to determine an optimal value for the magTiitude of the slack variable in the canneiy constraint. But the run varies con- siderably from year to year, and so in those years when the cannery constraint might be too low, we have an opportunity cost which appears as a slack variable in the dual formulation of the cannery constraint. It would seem then that t