Linking life history theory, environmental settings and individual-based modeling to compare responses of different fish species to environmental change

Abstract.-We link life history theory, environmental setting, and individual-based modeling to compare the responses of two fish species to environmental change. Life history theory provides the framework for selecting representative species, and in combination with information on important environmental characteristics, it provides the framework for predicting the results of model simulations. Individual-based modeling offers a promising tool for integrating and extrapolating our mechanistic understanding of reproduction, growth, and mortality at the individual level to population-level responses such as size-frequency distributions and indices of year-class strength. Based on the trade-offs between life history characteristics of striped bass Morone saxatilis and smallmouth bass Micropterus dolomieu and differences in their respective environments, we predicted that young-of-year smallmouth bass are likely to demonstrate a greater compensatory change in growth and mortality than young-of-year striped bass in response to changes in density of early life stages and turnover rates of zooplankton prey. We tested this prediction with a simulation experiment. The pattern of model results was consistent with our expectations: by the end of the first growing season, compensatory changes in length and abundance of juveniles were more pronounced for smallmouth bass than for striped bass. The results also highlighted the dependence of model predictions on the interplay between density of larvae and juveniles and characteristics of their zooplankton prey. Predicting the responses of fish populations to In this paper we link life history theory, envienvironmental change continues to be a major ronmental setting (i.e., the spatial and temporal challenge in fisheries science. Populations are rou-characteristics of the abiotic and biotic compotinely challenged by natural and anthropogenic nents of the local environment), and individualchanges in the environment, such as variations in based modeling to compare the responses of two temperature and runoff and changes in stocking fish species to environmental change. Life history and fishing practices. In trying to interpret popu-theory provides the framework for selecting replation responses to such changes, scientists are resentative species, and in combination with infaced with a diversity of life history strategies, life formation on important environmental characterstages, and environmental settings (Winemiller and istics, it provides the framework for predicting the Rose 1992); limited understanding of mechanisms results of model simulations. Individual-based involved in regulation of populations and com-modeling offers a promising tool for integrating munities (Rothschid 1986); and evidence indicat-and extrapolating mechanistic understanding of ing that differences among individuals are likely reproduction, growth, and mortality at the indito be important and differences in the environments of these two 45