DYNAMICS OF FISH POPULATIONS WITH DIFFERENT COMPENSATORY PROCESSES WHEN SUBJECTED TO RANDOM SURVIVAL OF EGGS AND LARVAE

It is widely believed that abundance of fish populations is determined during the larval stage, for larval abundance is high, there is high variability in larval survival, and small changes in larval abundance could have large effects on population abundance. In this study, hypot hesized population regulation processes were quantified in a mathemati cal model that was applied to study the importance of compensatory pro cesses during the larval stage by replacing them with random survival. The hypothesized population regulation processes were food-limited gr owth, size-dependent mortality, and age at maturity dependent on size. Variation in population abundance resulting from variation in egg and larval survival depends on the population regulation process. In popu lations where mortality depends on size of individuals, variation in s urvival of young has little effect on abundance of adults. If age at m aturity is flexible, variation in survival of young causes large fluct uations in abundance and the fluctuations follow a pattern of occasion al large year classes that are slowly attrited over their lifespans. I f age at maturity is not flexible, and if mortality is not size depend ent, variation in survival of young causes population abundance to flu ctuate widely without a clear pattern. Compensation during the larval life stage was not necessary for regulation of fish population size.