Density-dependent coexistence in fish communities

A set of stage-structured competition models is considered. The models are parameterized using allometric relationships specific to four fish life his tory strategies, constraining the model to biologically plausible regions i n parameter space. Using a coupled consumer-resource competition model, I g et the paradoxical result that two populations can coexist in equilibrium o n an identical resource base, without recourse to temporal or spatial parti tioning. In contrast to much theory on limiting similarity, the model also predicts that fish populations of similar life history strategies can coexi st in equilibrium with complete resource overlap. This form of coexistence (called density-dependent coexistence) requires that life history strategie s differ such that an advantage at one stage of the life cycle implies a di sadvantage at another stage in the life cycle. These exact life history tra de-offs appear in small-bodied fish. Furthermore, it is postulated that thi s result may be applicable to other taxa.