FIELD INVESTIGATIONS OF THE EARLY-LIFE STAGES OF MARINE FISH

This chapter discusses the field investigation of the early life stages of marine fish. The motivations for investigations have changed little over the intervening period, being mainly the assessment of adult spawning biomass and distribution, and the desire to understand how environmental variations and changes in the abundance of other species interact to regulate the abundance in particular fish populations. In many cases, the annual recruitment of new juveniles into the population is the most important process governing population fluctuations. The factors affecting recruitment, particularly those affecting the survival of the eggs and larvae, are therefore perceived to be of key importance. In the review of the chapter, the progress of field research on the early life stages of marine fin fish is examined. The objectives of field studies are briefly stated in the chapter, followed by a review of sampling methodology, analytical techniques, and the methods for assessing adult spawning biomass from egg and larval abundance data. This chapter also discusses the field evidence for variability in the growth, survival, and behavior in relation to biological and physical oceanographic conditions concentrating on larvae but including eggs were relevant. Finally, the match-mismatch and member-vagrant hypotheses, and the role of density-dependence in early life stage regulation, are considered in the light of the field evidence. © 1992, Academic Press Limited