ABSTRACT

Traditional age-based population models have been widely used both in ecology and fisheries management. But age-based models have been difficult to apply to fishes and other organisms where survivorship and fecundity depend more strongly on size than age. In fishes, recruitment variation is often high and has important population implications. The mechanisms controlling survival and recruitment of fishes appear to operate at the level of the individual, so modeling this process may best be done using individual-based models. Individual-based models have been widely used in fish behavioral and physiological ecology, but the population implications of variation among individuals have not been carefully examined.

Our studies of recruitment mechanisms of Lake Michigan bloater (Coregonus hoyi) have shown the importance of body size and growth rate variation to recruitment. Based on a literature review, body size and growth variation in larval fishes seems to be of widespread importance. An individual-based model for predation on larval bloaters suggests that variation among individuals in growth rate can influence cohort survival and size structure. Size-dependent mechanisms controlling recruitment in fishes may be successfully integrated using individual-based models.