American Fishcncs Society Symposium ?:I-16. 1987

Use of Fish Eggs and Larvae in Probing Some Major Problems in and REUBENLASKER National Marine Fisheries Service, Sourhwest Fisheries Center , 92038, USA

Abstracr.Studies of the early life history of marine fishes have progressed greatly in the quarter century since the pioneering work of Sette, Ahlstrom, and others. A brief history of this recent era points out the many ways in which eggs and larvae have been used to address central problems of dynamics, management, and culture. Challenges and opportunities await early life histori- ans in the areas of fish distribution, biomass estimation. species identification, recruitment, species interactions, aquaculture, enhancement, pollution assessment, definition of subpopulations, and production. Early life history studies have acquired considerable relevance to society as well as to science.

I was pleased and flattered to be asked to be the and larvae. These people are becoming fewer and keynote speaker to this meeting of the Early Life those with an early vision of the importance of History section of the American Fisheries Soci- this field to are no longer with us. ety. The papers of this meeting are very impres- I am referring to scientists like Elbert H. Ahl- sive and comprehensive, much more so than strom, Milner B. Schaefer, and , those of the very first Larval Fish Conference in each of whom would have made a better speaker the , which was held at Lake Arrow- than I. However, I did have substantial contact head, California, in October 1963. The proceed- with each of them and I would like to start this ings of that early conference appeared in volume talk with a few anecdotes which should give you X of the California Cooperative Oceanic Fisheries an impression of how important they were to the Investigations Reports of 1965. Figure 1 is a study of the early life history of fishes in relation photograph of the conference contributors. to fisheries. In 1%3, although we had some data which Sette (Figure 2) was a fishery biologist for the showed that fish eggs and larvae could be impor- U.S.Fish and Wildlife Service who believed that tant tools in the study of fish populations, we still an understanding of fish eggs and larvae and what had much to prove. Now, many of the papers affected them in the sea would lead us to an ability being given at this 1986 conference are proof of to predict the size of incoming year classes. When this early premise. This paper is a personal per- the population of Pacific Sardinops sagax spective on studies of early life history of fish. It is (then known as S. caerufea)suffered from its now intended to give a historical view of some of the famous collapse in the 1940% he was sent by the reasons fishery scientists find the subject interest- federal government to set up a U.S. initibtive to ing and to suggest what the future may hold for find out what happened. Figure 3 is from his 1943 those of us who continue with it. Although I paper (Sette 1943b) on setting up a research cannot possibly cover every aspect of the early program to determine how affected the life history of fishes, I hope to make the point that sardine resource. In it you can see all the elements fisheries science has benefited a great deal from for determining what factors affect an incoming the subject. year class to a fishery. In particular, the impor- The need for is one good tance of fish eggs and larvae is clearly pointed out. reason to bring us together and I would like to aim Ahlstrom (Figure 4) was Sette's collaborator, my remarks towards that end, recognizing, of and it was he who was given the day-to-day course, that foremost we are biologists trying to responsibility to cany out systematic ichthyo- answer the important basic question of how fish plankton surveys. This was the origin of the now eggs and larvae survive in natural waters. unique larval fish time series of California and Baja California species which began in 1939. Sette, Ahlstrom, and Schaefer Ahlstrom believed that at least two imponant In California, I was able to meet and associate questions could be answered with these surveys: with some of the pioneers in the study of fish eggs How is the Pacific sardine distributed? and How is I FIGUREI .-Participants in the first conference on the early life history of fishes, Lake Arrowhead. Calilornia. October 1963. Left IO right: George 0.Schuniann (La Jolla). Wilhelm Einsele (Austria), Fred Holliday (Aberdeen). John lsaacs (La Jolla), Horst Schwassman (La Jolla). James E. Shelbourne (Lowestoft),John Blaxter (Aberdeen), Elbert ti. Ahlstrbm (La Jolla), Reuben Lasker (La Jolla). Gotlhilf Hernpel (). the Pacific sardine population changing with time? only to look for Pacific sardine eggs but, because To our everlasting benefit, Ahlstrom chose not of his deep interest in systematics and ontogeny. set out to name and identify all of the eggs and larvae that were caught by the plankton nets deployed for Pacific sardine. In a less complicated world where direct con- tact with Washington for assistance was possible, funds were always ample for these surveys. Join- ing with the Fish and Wildlife Service was the Scripps Institution of , headed in the 1950s by Roger Revelle, who saw the enor- mous value in such surveys not only for- monitor- ing fish populations but for describing the ocean- ography and of the California Current system. The California State Legislature provided funds for the Marine Life Research Group at Scr-ipps Institution of Oceanography at the re- quest of a former director, Harald Sverdrup. and it continues today as a partner in what is known as the California Cooperative Oceanic Fisheries In- vestigations or CalCOFI. From the surveys we learned that the collection and identification of fish eggs and larvae can tell us where fish reside, when they spawn, and how they are related to each other numerically and ontogenetically. Schaefer (Figure 5) was one of the original FIGURE2.-Oscar Elton Sette, about 1949. Pacific sardine investigation scientists with Sette IMPORTANCE OF EARLY LICE HISTORY STUDIES 3

I RECRUITMENT I I I ./

juveniles reaching commercial size Juvenlle 2 Certaln oceanographic 2 - survival 4 condltlonr. - Planktonic food 7 reaching post-

Abundance of Danalty of competlng or , f juveniles - predatory forms

Number of larvae reaching post- I planktonic stage Certaln oceanographic conditions: survival Planktonic food 7 Drift 7 eggs hatched

Certain meteorological conditions: Wind 7 ::::::e I ::::::e I I Climatic cycles 7

Number of

conditions: survival Drift 7 Temperature 7

Flsurvival rate ) Potential spawning capacity I Certain OceanOgrSphiC Abundance and conditions: age composition of commercial Temperature 7 commercial stock Planktonic food 7

FIGURE3.--Sette's plan to study recruitment of the Pacific sardine, 1943.

I_ 4 LASKCR

(1) Distrihirtion: Where are the fish? (2) Biotiicrss ~.stirnoiion:How many fish are in the sea? (3)Specic7.s idcvrtiJiccrrion: What fish are there? (4) Rc,c.riritnrc.ri/: How many fish will be avail- able to a lishery next year'? This question sub- sumes others. Can the magnitude of recruitment be predicted? What are the biotic and abiotic factors alFecting recruitment? To what extent can we fish a population without endangering succes- sive year classes'! How and why do populations nuct uat e ? (5) Sprcio.r ititc~rcic~fio,i.s:Does the presence of one species hinder or enhance the survival or reproduction of another species? (6) Aqimcdture: Can we insure domesticated crops of desired species'? (7)Eiihcr,rc~c~nic,,rf~ Can we release fish eggs and larvae into the sea and therehy increase stocks'? (8) fdhtioti; Do pollutants alfect fish popula- tions through their elfects on fish eggs and larvae? (9) S~ihp~~prtltrtio,~.~:Do more than one stock contribute to a fishery? FIGURE4.--Elbert H. Ahlstrom. about 1969. (IO) Prodrrctiotr: How many fish can a body of water produce and support?

in 1946 but. to my knowledge. he never worked on fish eggs or larvae. Why then. do I include him in this essay? The reason, quite simply, is that he had the major role in writing the section on fisheries for the National Academy of Sciences report on "Oceanography in the 1960s." The post-Sputnick era promised increased money for science and it was Schaefer who pointed out the potential importance of the study of fish eggs and larvae to aquatic science and fisheries in particu- lar. We probably all owe a debt to him. I make no claim that the following is an exhaus- tive survey of who has done what in this remark- able field. Kather. I have chosen to talk about the attempts niadc at solving some major problems in fisheries science by studying fish eggs and larvae. Examples are taken niostly from the west coast of the USA with which 1 am personally familiar.

Some Major Problems in Fisheries Science The major scientific problems in fisheries sci- ence today. by my definition. are those which fishery scientists agree need to be solved to facil- itate rational management of fisheries throughout the world. I have listed those which I believe are the most pressing; attempts to solve them have involved fish eggs and larvae. It is surely not an exhaustive list. FIGURE5.-Milner R. Schaefer. about 1970. IMPORTANCE OF EARLY LIFE HISTORY STUDIES 5

Distrihitrion even clearer idea of how spawning ranges change, Sette did one of the first, if not the first. sometimes coincident with a major environmental comprehensive ichthyoplankton surveys off the event like the 1983 El Nino, a warming of the U.S. east coast to study the Pacific over a vast area (Figure 7). Charts of these S(.omhrr .sc~ornhrris.His plan for the Pacific sar- distributions in California waters have been pub- dine. in modified and extended form. has been lished in atlases tKrarner and Ahlstrom 1968; continued for 40 years. Figure 6 indicates the use Ahlstrorn 1969: Kramer 1970; Ahlstrom and of the ichthyoplankton survey off California and Moser 1975) and in many other publications. We B+ja California to assess the distribution of a know now that when ihe Pacific sardine popula- population and how it changes with time. In tion was on the brink of collapse, the remainder of recent years. the Southwest Fisheries Center has the population retreated into the Southern Cali- done ;I finely spaced egg survey which gives an fornia Bight. making the remnants even more

JACK MACKEREL LARVAE J’ JACK MACKEREL LARVAE 1

.....

an Francisco

...... Cumulative Totals ...... E311a1.lo1 .10 100 loo0 ...... *::y - - ...... mover loo0 ..... - Stations occuoied 115 14io FIGURE6.-Distribution of larval jack mackerel Trnclrirrrrs symntt.rric I(.\ off California. 1953 and 1954. Data are larvae per standard tow. 6 LASKER

t 0

FIGURE7.-Egg distributions for northern anchovy Engraulis midax off California during February (02)or March (03) 1980-19%5. Dots represent sampling stations; surface isotherms arr in T.(From Ficdler et al. 1986.) vulnerable to fishing (Murphy 1977). The Peruvian with other fisheries laboratories, we have sought anchovy anchovetta Engraulis ringens exhibited an ichthyoplankton method which would be more this same behavior just prior to its collapse (Val- precise and with which we could assign errors to divia 1978). every biological parameter. We devised such a Paul Smith, Geoffrey Moser and Larry Eber are method for the northern anchovy, which we call taking the distribution information much further. an egg production method (Lasker 1985). Briefly, Using CalCOFI data from 7 years of intensive the idea is to encompass the spawning habitat of sampling, they have analyzed changes in the the population and to sample about 1,OOO times distribution and abundance of major components within the habitat with a small, rapidly retrieved of the larval fish assemblage off California and plankton net (Figure 8). The eggs caught are then Baja California in response to dramatic changes in related to female fecundity and the frequency of oceanographic conditions. spawning (Figure 9). That is an all-too-brief char- acterization of a method that takes 40 d of ship Biomass Estimation time, retrieval of anchovy eggs &om plankton SeveraI marine scientists have used the number samples, staging and aging of the eggs in the of fish eggs or larvae to estimate the spawning laboratory, histological preparation and examina- biomass of commercial species in the sea (e.g., tion of the female gonads, and mathematical anal- Saville 1964). The difficulty has always been with ysis of the data. The advantages of the method are the assumption that the number of larvae or eggs that no assumptions are made about the of is proportional to the abundance of females the fish and it takes 100 fewer days of ship time spawning them. In our laboratory, in common than our normal larval survey. This technique is IMPORTANCE OF EARLY LIFE HISTORY STUDIES 7

- k’k’PW RFE

CALVET SURVEY B SPAWNING BIOMASS ANCHOVY EQGS PER TOW k1 SURFACE AREA OF OCEAN OVER WHICH P IS ESTIMATED (units of 0.05 m2)

k2 CONVERSIONFACTORFORGRAMSTO SHORT TONS

P DAILY EGG PRODUCTION (eggs per 0.05 m2) W AVERAGE WEIGHT OF MATURE FEMALES (grams) R SEX RAT0 (fraction females based on weight) F SPAWNtNG FRACTION (fraction of mature females that are day-1 port-ovulatory) E BATCH FECUNDITY (eggs per mature female)

FIGURE9.-Equation and parameters for the egg production method of estimating the biomass of spawn- ers (Lasker 1985).

through the technique of demonstrating morpho- logical similarities between growth stages. In the last decade, sophisticated rearing techniques have permitted identification of larvae heretofore uni- FIGURE8.-An egg survey for northern anchovy dentifiable. Over 200 species of larvae have been biomass assessment off California in 1982. Surface iso- identified in the California Current to date, and therms (“C) are superimposed on the egg distribution. so have been named to family. (From Picquelle and Hewitt 1983.) another 60 or Numerous publications on the identification and developmental life stages have appeared from the now being applied to a variety of fish stocks Ahlstrom-Moser laboratory; recently, the volume including the Peruvian anchovetta, the North Sea “Ontogeny and Systematics of Fishes” was pro- sprat Clupea sprattus, the Sardinella off Brazil. duced by Ahlstrom’s colleagues and dedicated to and the Pacific sardine, and a program is planned his memory (Moser et al. 1984). The ichthyo- for the Spanish sardine Sardina pilchardus. plankton survey in the Ahlstrom style has been adopted as a scientific tool throughout the world. Species Identification The ichthyoplankton survey had its origin in the Recruitment work of the Norwegians, English, and Germans at As a fishery problem, the prediction of recruit- the end of the 19th century. Notable in using ment is foremost in the minds of fishery scientists. plankton nets for determining what plankton were Fishery theory has it that if we could accurately present were Hensen (1895). Schmidt (I-), and predict recruitment a year in advance for most Buchanan-Wollaston (191 1). In the United States, commercial fishes, management would be that Sette (1943a) used the survey technique to study much more precise and risks by the and the Occurrence of Atlantic mackerel off New processors would be greatly reduced. I leave the England from 1927 to 1932. As I have said, it was economics of that to the economists but I would Sette who outlined the survey program for Cali- like to comment on the hypotheses about recruit- fornia, but it was Ahlstrom who honed it to such ment, specifically on those that involve the sur- a degree that the California Current now is one of vival of fish eggs and larvae. the best chqcterized for fish species in the Hjort (1926) suggested the “critical period” world. These studies were unique for their time hypothesis: “. . . those individuals which at the because the surveys covered the habitat of an very moment of their being hatched did not suc- entire population (the Pacific sardine) and have ceed in finding the very special food they wanted told us what species were associated with it. From would die from hunger. . . . in other words the monthly cruises over a 10-year-span, the spawn- origin of a rich year-class would require the contem- ing seasons of the Pacific sardine and many other porary hatching of the eggs and the development of species were delineated. The other species were the special sort of plants or nauplii which the newly identified by the construction of life histories hatched larva needs for its nourishment.” Hjort 8 LASKER suggested this hypothesis because the early culture immediate environment. Furthermore, as aqua- work of the French scientists Fabre-Domergue and culturists know, even foods which are readily Biktrix (1905) showed that larvae of sole Solea ingested do not necessarily support growth and vulgaris (= Solea solea) started to look for food survival. Work off California showed that there even before their yolk sacs were absorbed; if they was also a threshold number of food particles did not find food nght away, they became which had to be in the larva’s immediate sur- “anaemic” (as they called it) and died of starvation. roundings before it could be assured a meal. This experimental result, when coupled with the When these facts about the first-feeding larva’s observation that good year classes of several dif- needs and behavior are considered, prediction of ferent species of fish sometimes coincided in the survival becomes a much more complicated mat- Norwegian fisheries, suggested the “critical period” ter because the measurement of all of these fac- concept to Hjort (1914). tors over a spawning season is a formidable task. Sette’s work did not support the critical-period The argument about density-dependent and den- concept for first-feeding Atlantic mackerel larvae. sity-independentrecruitment has also occupied fish- He found that the greatest mortality occurred late in ery biologists. Those believing in density depen- the larval period, when the animals were about 9 dency say that we have to take into consideration mm long or about 1 month old. But laboratory work the number of fish in the population, the number of on sardine, anchovy, and larvae seemed to eggs spawned, and how these numbers have an give results similar to what Fabre-Domergue and effect on the number of fish that finally survive. Biktrix found with sole larvae, and the testing of the Those convinced that density-independent effects Hjort hypothesis continues to this day. are the most important have ample evidence to Fishery scientists are convinced that at least show that even unfished populations undergo wide two processes must prevent fish from surviving to variation in population size, hence recruitment. a fishable size: starvation and predation. A lot of Hjort also recognized that sometimes very small fish effort has been expended in recent years trying to populations could give rise to very strong year decide which is more important and whether the classes and in, recent times, we have the examples conditions that cause one or the other can be of the Japanese and Chilean subspecies of Pacific predicted. As an example, my own work showed sardine, the North Sea Herring Chpea harengus that food for first-feeding northern anchovy larvae harengus, the chub mackerel Scomber japonicus in was highly variable in the environment, and, at California, and many others Fires 10,ll). least in the Bight, was re- The environment seems to regulate the food stricted to nearshore areas (Lasker 1975). Labo- available for first-feeding northern anchovy lar- ratory experiments by my colleagues (Scum and vae. Stable Ocean conditions favor aggregation of Jerde 1977) indicated that these larvae could not suitably sized food organisms so that above- or would not eat diatoms or microflagellates and threshold numbers of food particles become avail- relied on dinoflagellates or micronauplii in their able to the larvae. I found that when a strong

250 E 1 JAPANESE SARDINE e 200

0 -2 150

.,.,,, 1905 10 15 20 25 30 35 40 45 50 55 80 85 70 75 80 YEAR FIGURElO.-Catches of Pacific sardine off Japan, 1905-1981. The 1984 catch was 420 x 104 tomes. IMPORTANCE OF EARLY LIFE HISTORY STUDIES 9

1,800 starvation each day. Theilacker (1986) also / showed histologically and morphologically that / 1,400 I/ first-feeding jack mackerel are mostly starving in I an oligotrophic part of the species’ spawning I I habitat (Figure 13). Close to islands, evidence of 1.200 I starvation drops off considerably; in this case, we SARDINE / must invoke predation as the main cause of mor- a I 5 1.000 I tality (see also Hewitt et al. 1985). - As far as northern anchovies off California are c) I z I concerned, it is clear that the kind of food avail- I( 800 I - I able is of paramount importance too. We have I 0 demonstrated that a particular dinoflagellate, I- a 800 Gonyaulax polyedra. was the dominant food 0 available to first-feeding larvae in 1975 but, in the laboratory, the larvae could not survive on it 400 (Lasker 1981). That year was an interesting one. Primary production in 1975 was far higher than in 200 any previous or subsequent year but it produced one of the worst year classes of 20 consecutive 0 ones measured. Upwelling brought in diatoms 1970 1975 1980 after sweeping out the bloom of Gonyaulax poly- YEAR OCT. edra, but diatoms are not eaten by northern FIGUREIl.

OFFSHORE AROUND ISLANDS 100

50

0

lrn[ FIRST REDING FIRST FEEDING >- 50 na of Ill n 0 I- z 100 C I- W 3.5- <4.m 3.5- <4.0mm zW n 50

0

FIGUREI3.-Mortality. starvation. and survival of developing jack mackerel larvae off California. (From Theilacker 1986.)

predators on fish eggs and larvae? Hunter and rings on otoliths has opened some new avenues to Kimbrell (1980) have shown that adult northern study recruitment of larvae. The important paper anchovies feed on northern anchovy eggs and by Methot (1983) showed us how we might corre- probably the larvae as well. Many other authors late survival and mortality of larvae with environ- have shown how vulnerable fish larvae are to mental changes. In e'ssence, Methot showed that invertebrate predators (Lillelund and Lasker monthly larval production over a spawning season 1971; Theilacker and Lasker 1974; Bailey 1984; could be compared to the birthdate frequency of Purcell 1985) but we have no tool yet that would juveniles, i.e., the surviving recruits. For those allow us to quantify the effect of these predators. months in which most survivors had hatched, An immunoassay technique to detect the degree correlations can be sought with specific events in of euphausiid shrimp predation on yolk-sac larvae the environment (Figures 14, 15). It is the fist has just been developed by Theilacker et al. time we have been able to analyze events within a (1986). The field data are very promising, and this spawning season, rather than averaging variables may be what we need to solve the quantitative over an entire spawning season. This idea forms aspect of predation. Something like this approach the basis of an international program called is certainly needed now for postyolk-sac larvae. SARP, the sardine-anchovy recruitment project, Our growing expertise in calibrating and read- an initiative of the Intergovernmental Oceano- ing the ages of larvae and juveniles from the daily graphic Commission and the Food IMPORTANCE OF EARLY LIFE HISTORY STUDIES 11

...... :.:.;;.:.:.:. ;:a

MONTH 0.0

1977 11078 n I FIGURE15.-Methot’s (1983) actual data for larval production and birthdates of juvenile northern ancho- vies during the 1977-1978 spawning season off Califor- nia.

is a body of literature on competition for habitat among adult fish, particularly on coral reefs, but how can fish eggs and larvae help us decide whether and to what degree competition occurs? First, one has to have some indication that there is MONTH a reciprocal relationship between species; then FIGURE14.4eneralized curves of northern anchovy one can proceed to an analysis of causal mecha- larval production over a spawning season off California. nisms. As an example, MacCall (in Lasker and and distributions (bars) of birthdates of surviving juve- MacCall 1983) studied Pacific sardine and north- niles. The top panel shows the birthdate distribution that em anchovy scales in anaerobic sediment cores would occur if there were no major environmental collected from the Santa Barbara Basin, Califor- perturbations during the spawning season. The lower nia. He found that northern anchovy scales were panel shows the distribution that might occur if environ- mental factors atfected survival at various times during smaller when sardine populations were large and the spawning season. larger when sardine populations were small. This kind of presumptive evidence suggests a compe- and Agriculture Organization under the Interna- tition for food among the adults. Does such a tional Recruitment Program (IREP). competition between species occur in the larval To summarize this recruitment section, it seems stages? to me that we are on the threshold of making great The CJCOFI data base lists and enumerates strides in understanding how fish larvae are con- the fish larvae of myctophid species, some of trolled by their physical and biotic environment which spend their entire lives in the dark and are and to quantify the roles that environmental fac- by necessity carnivorous. Some of these popula- tors play in recruitment. I think Hjort would be tions are enormous by number if not by biomass pleased with the progress made in the last 15 and must exert great predation pressure on pe- years, but he would also admonish us because the lagic fish larvae of all kinds. Some fish larvae, definitive test of the critical period hypothesis has e.g., those of chub mackerel, can eat northern not yet been made. At the very least the SARP anchovy larvae handily in laboratory tank envi- initiative may be the way to accept or reject the ronments. Competition between individuals of “critical period” hypothesis for anchovies and different species for food somehow seems un- . We have a very long way to go to do the likely because fish larvae are usually such a small same for the other important commercial species. component of the plankton, but what do we really know? Not much. I think it is clear that this is an Species Interactions area of research that requires much more atten- Competition is extremely difficult to observe in tion and may have very important implications for pelagic and benthic systems. We know that there rnultispecies management of commercial species. 12 LASKER

Atpncitl~rrre I think the evidence is very good now that aquaculture is a proven technology for a variety of organisms and is paying off in real money for various cat-ps and tilapias. striped mullet MitRil c~eplriilrts.madai Pngrrts mtijor, black porgy Acon- tlroptigrits sclrlegeli, European bass Morone lo- hrtrx, and a host of others, but there are many species which have defied propagation and CUI- ture. It is interesting to read the joiirnals devoted to aquaculture. Papers on fish larvae abound. and techniques for raising particular larvae are out- lined in great detail. The challenge to early life history scientists is to reduce mortality and insure rapid growth of the egg and larval stages of those species that are desirable for human food and commerce. The use of the rotifer Brtrc~lriototsplic.crri1i.r for larval food was introduced in Japan in IY65 and was a breakthrough for fish rearing. although the species originally was considered a noxious zoo- plankter in eel culture ponds (Hirdno 1969; Hirata 1979). Brachionits pliccirilis has succeeded almost everywhere it has been tried with marine species. In La Jolla, we have used a clone isolated from FIGURE16.-Spencer F. Baird. first U.S. Commis- the highly saline inland Salton Sea (Theilacker sioner of Fisheries. (From Allard 1978.) and McMaster 1971) to rear northern anchovy larvae; nauplii of the euryhaline crustacean Arre- (Figure 16). In 1871, Baird persuaded Congress to ntici scilino have probably been used even more as create the commission and then willingly accepted a larval fish food and also with notable success the charge of countering the decline of fish olf (May 1971a). Copepods are very desirable for this southern New England. The next year. he was purpose but culturing them in appropriate quanti- given the charge of ai-tificially propagating lish to ties is a more formidable problem. replenish and restock depleted freshwater and Aquaculturists would be the first to say that marine areas. There were some successes with. their task is not easy and that the road to success for example, various salmonids and common carp is filled with obstacles, but we have seen remark- Cyprinrts ccirpio, and. in 1878, a major program able progress in fish rearing during the last three was started with marine species. Baird did not decades. This has been accomplished in great part think that there would be much success in the by academic and applied scientists who have had open sea but he was convinced that there would an interest in determining the behavior and the be some impact in local coastal areas, such as fastidious environmental and food requirements from the several million larvae of Atlantic cod of fish larvae in freshwater and marine systems. 1 Grtlits niorliito that were released into Gloucester was an early skeptic, but I am convinced now that harbor, Maswchusetts. There was little evidence the culture of marine fishes has seen. and will of any effect, however. I am not sure we have yet continue to see, some real successes such as we learned the important lesson, now over years have had with freshwater species. I00 old, that any attempt to enhance natural systems requires us also to determine what proportion of Enhiincement stocked animals survives. The failure to do this One of those areas of rearing that needs partic- was really the undoing of the marine enhancement ular attention is the trend toward enhancement of program Baird had so laboriously erected (Allard natural stocks. lhis leads us back in time to the 1978). work of the first Administrator of the U.S. Com- In the early years of the Fish Commission. mission of Fish and Fisheries, Spencer F. Baird Baird was an active participant in the American IMPORTANCE OF EARLY LIFE HISTORY STUDIES 13

Fish Cultural Association, which, after 1884, was What can fish eggs and larvae tell us about con- known as the American Fisheries Society. Thus tiguous populations which are close to one an- the Early Life History Section of the American other but genetically separate? Does it make Fisheries Society has important historical roots. sense to use these developmental stages when the adults are available for analysis? I think not, but Pollution the ease of capturing the spawn provides genetic Surprisingly, we do not yet have a larval fish material when it is virtually impossible to capture analog of the laboratory white rat. With all the the adults-for example, before a fishery is initi- rearing of larvae going on at present, one would ated on a species whose adults live in deep waters have expected that some larval fish would have but whose eggs and larvae occur at or near the made the perfect test organism for pollutants. In surface. 1%5, when the Santa Barbara, California, oil spill In 1%2, I had the opportunity to work with occurred, I used northern anchovy larvae as test Blaxter and Holliday on larvae of Altantic her- organisms in the laboratory to see if the dispersant ring. My introduction to this species was in , used by the oil companies was in any way toxic. It where had arranged for me to was no surprise that the dispersant was highly collect some larvae. I was astonished to find that toxic to larvae in concentrations as low as 2 mgL newly hatched Atlantic herring larvae were only (Anonymous 1969). I then received funds to see if about one third the size at Kiel that they were in northern anchovy larvae could be used to evalu- the North Sea. Clearly, this species has evolved ate other pollutants. The work resulting from that remarkably different subpopulations within a few program showed that the larvae take up chlori- hundred kilometers of each other. nated biphenyls directly from sea water (Scura The use of larvae in subpopulation studies and Theilacker 1977). My own agency considered deserves much more attention. this work a very low priority at that time, how- ever, and it was terminated. Production Granmo (1981) reviewed some of the reasons I have spent a great deal of my professional life for using fish eggs and larvae in pollution studies, pursuing an understanding of fisheries production, and listed the following. (1) Fish are economically trying to evaluate the steps in the marine food important. (2) Fish eggs and larvae are sensitive to chain leading to harvestable fish. It took me about pollutants. (3) It is relatively inexpensive, quick, 20 years to realize that this is much more difficult and easy to run toxicity tests on fish larvae. (4) than I had naively thought. It will take many more We know a lot about fishes. In my opinion, there years and much more effort to come to any real is another reason: fish eggs and larvae may be the conclusions about production dynamics. key stages in determining the magnitude of fish In 1%9, Ryther published a harvest prediction populations. for marine fisheries. With admittedly rough calcu- What has eluded fishery scientists is some deter- lations, incorporating what we knew at that time mination of how populations of fish are affected by about primary and secondary production in the pollutants. This question should be central to most sea, the efficiency of transfer through trophic of the work going on in lakes and the sea, but few levels, and the productive areas of the world’s studies are aimed in that direction. Currently, in my oceans. he concluded that the potential sustained own laboratory, Michael merand Alec MacCall yield of fish to humans would not exceed 100 are looking for correlations between historical million tonnes (Ryther 1969). Eighteen years trends in fish stocks (as indicated by collections of later, we find that Ryther (considered by fishery fish eggs and larvae) and contaminant inputs into scientists the pessimist of his time) gave us a California coastal waters. To what extent the mor- figure which seems grossly optimistic. Today the tality of fish eggs and larvae might be involved in harvest is barely 70 million tons and increasing at these correlations requires field experiments no one an infinitesimal rate (Figure 17). One must con- is really ready to do, yet it is most likely that it is clude that we have been doing something wrong these sensitive stages of development which bear or that the assumptions we have made, e.g., that the brunt of ocean and lake pollution. the efficiency of nutrient transfer seen in the laboratory can be extrapolated to the sea, are Subpopulations incorrect. My own work has shown that the Fishery managers always want to know magnitude of primary production may have little whether a fishery is based on one stock or several. relation to the size of a resultant fish year class 14 LASKER

are just as much fun as any other but carry the WORLD CATCH added benefit of being important to society as a whole. In early life history studies of fish we have that added benefit: our work is relevant to fisheries and aquaculture. I have tried to point out some of the significant problems that our laboratory and field studies can address. The papers being given at this meeting illustrate broad recognition of these points. This was not the case 25 years ago, however, and we needed the pioneers I mentioned who had the foresight to persevere with early life history studies. Without them, our work would have been of academic interest only and might never have shown its potential in solving some of society’s most pressing aquatic resource ques- tions.

References 50 55 60 65 70 R 00 Ahlstrom, E. H. 1%9. Distributional atlas of fish larvae in the California Current region: jack mackerel, YEAR Truchurus symmetricus, and Pacific hake, Merluc- FIGURE17.-Actual and predicted world fish har- cius productus, 1951 through 1966. California Co- vests. (From Darr and Hennemuth 1985.) operative Oceanic Fisheries Investigations Atlas 11. Ahlstrorn, E. H., and H. G. Moser. 1975. Distributional (Lasker 1981) and that this discrepancy may be atlas of fish larvae in the California Current region: flatfishes, 1955 through 1960. California Coopera- rooted in the behavior and physiology of the tive Oceanic Fisheries Investigations Atlas 23. larvae. We do not know enough about the inner Allard, D. C., Jr. 1978. and the workings of the larvae of most commercial fish, U.S. Fish Commission. Am0 Press, New York. nor do we know much about how primary produc- Anonymous. 1969. BCF scientists assess effect of oil tion is partitioned among groups of organisms. We spillage in Santa Barbara channel. U.S. National now know that most euphausiids (Lasker 1966) Marine Fisheries Service Commercial Fisheries Re- view 31(3):6-7. and copepods (Cowles and Strickler 1983; Price et Bailey, K. M. 1984. Comparison of laboratory rates of al. 1983; Koehl 1984; Strickler 1984) are preferen- predation on five species of marine fish larvae by tially carnivores or at least selective feeders just three planktonic invertebrates: effects of larval size like fish larvae, yet most food chain models are on vulnerability. Marine Biology 79:303-309. based on their empirically derived filtering rates. Buchanan-Wollaston, H. J. 1911. On a new form of Notwithstanding the problems we have with mea- plankton net designed to make truly vertical hauls suring primary production, we have to conclude in any weather. Publications Circonstance Conseil Permanent International pour I’Exploration de la that the measurement of secondary production is Mer 29:9-14, Copenhagen. in a very dire condition and requires new insights, Cowles. T. J., and J. R. Strickler. 1983. Characteriza- new techniques, and a fresh look. tion of feeding activity patterns in the planktonic copepod Centropuges rypicus Kroyer under vari- Conclusions ous food conditions. Limnology and Oceanography 28:106-115. At a student’s exam at Scripps Institution, Russ Dam, D. R.. and R. C. Hennemuth. 1985. Forecasting Doolittle, a biochemist, asked if the problem the for resources in forestry and marine fisheries in the student had chosen for a doctoral project was a year 2000. American Statistician 39(4, part 2):384- significanr one. Doolittle explained that, as a 392. student himself, he had worked for professors Fabre-Domergue, and E. Bi6trix. 1905. Developpement de la Sole (Soleu vulgaris). Introduction A I’etude who seemed to be wrapped up in trivia, trying to de la pisciculture marine. Travail du Laboratoire de find out more and more about less and less. The Zoologie Maritime de Concarneau. Vuibert et lesson he was trying to convey was that there are Nony, Paris. many important problems to be worked on which Fiedler, P. C., R. D. Methot, and H. P. Hewitt. 1986. IMPORTANCE OF EARLY LIFE HISTORY STUDIES I5

Effects of California El Nido on the northern an- Reunions. Conseil International pour 1'Exploration chovy. Journal of Marine Research M317-338. de la Mer 178:375-388. Granmo, A. 1981. Overview-pollution. Rapports et Lasker, R., editor. 1985. An egg production method for Proces-Verbaux des Reunions, Conseil Interna- estimating spawning biomass of pelagic fish: appli- tional pour I'Exploration de la Mer 178:61-63. cation to the northern anchovy, Engruulis mordux. Hensen, V. 1895. Methodik der Untersuchungen bei der NOAA (National Oceanographic and Atmospheric Planktonexpedition. Ergebnisse Planktonexpedi- Administration) Technical Report NMFS (National tion Humboldt-Stiftung Band I, 1-200. Marine Fisheries Service) 36. Hewitt, R. P., G. H. Theilacker, and N. C. H. Lo. Lasker. R., and A. MacCall. 1983. New ideas on the 1985. Causes of mortality in young jack mackerel. fluctuations of the clupeoid stocks off California. Marine Ecology Progress Series 26: 1-10. 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