Life history variation among 60 Ontario populations of lake trout (Salvelinus namaycush), walleye (Sander vitreus), cisco (Coregonus artedii), and yellow perch (Perca flavescens) is presented and interpreted using a biphasic model of individual growth that specifically accounts for the significant shift in energy allocation that accompanies sexual maturity. We show that the constraints imposed on life history variation by the character of the biphasic growth model are such that optimal life histories will exhibit associations among growth parameters, reproductive investment, and mortality that are largely consistent with associations evident in both our data set and earlier empirical studies; the von Bertalanffy growth parameter k varies with reproductive investment, and both k and investment vary with adult mortality. Our analysis suggests that within a food web, life history parameters will shift in a predictable fashion with the decreases in mortality expected as one moves from primary consumers up toward top predators. This expectation is supported by the differences in life history parameters that we observe between the two top predators in our data set (lake trout and walleye) and the two mid-trophic level consumers (cisco and yellow perch).
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