INTRODUCTION 



Fishes are large and conspicuous members of marine communities. They 

 have important commercial and recreational value, and their abundance can 

 fluctuate widely in response to environmental variability or heavy exploitation. 

 Fluctuations in abundance of fishes usually are caused by large annual 

 differences in recruitment, which are related to mortality experienced by a 

 cohort during the larval stage (28, 29). It has been difficult to evaluate 

 potential factors that could affect recruitment in studies carried out on natural 

 populations at sea because of the problem in estimating egg or larval 

 abundances over extensive ocean areas, and because of an unpredictable 

 environment whose effects cannot be controlled. During the past 15 years a 

 capabihty has been developed by several laboratories to routinely culture 

 marine fish larvae beyond embryonic and yolk-sac stages to the juvenile stage. 

 Experiments on these laboratory cultured species has resulted in significant 

 advances in our understanding of how environmental factors affect survival and 

 growth of larvae. 



Several papers recently have reviewed aspects of marine fish larvae culture 

 (42, 50, 64, 65, 67). Although May's (67) evaluation of the critical period 

 hypothesis, and Iwai's (50) review of feeding by fish larvae, included 

 discussions of both laboratory and field-oriented studies, they did not 

 specifically make conclusions about larval requirements based on experimental 

 research. Blaxter's (14) general review of egg and larval development of fishes 

 did summarize results of laboratory studies. We review some important results 

 of recent experimental research on marine fish larvae and make conclusions 

 about effects of environmental factors based on laboratory studies. Emphasis is 

 on studies of species that have typical, pelagic larvae and includes the period 

 from initiation of feeding until transformation to juvenile. Research on embryo 

 and yolk-sac stages, aquaculture-oriented studies, and work on non-pelagic or 

 non-typical larvae are not emphasized, although important contributions have 

 been made in recent years. 



Two major areas of research are reviewed and discussed. These are 1) the 

 role of the food supply, the ability to feed, and the effects of predators; and 2) 

 the role of physical and chemical variables, other than those due to man's 

 impact on the environment. In addition, new techniques that hold promise for 

 advancing environmental research on fish larvae are outhned and discussed. 



FOOD REQUIREMENTS 



The most important advance in larval culture technology during the past 1 5 

 years has been the determination of kinds and concentrations of living prey 

 that give predictable survival and growth rates. The ability to undertake 



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