A Habitat Suitability / Area-per-Individual Approach for Estimating the Productivity of a Fish Community

Estimating the productivity of multiple, interacting fish species, as opposed to focussing on single populations, is an increasing necessity for studying and managing fisheries. A great challenge inherent to multi-species modelling is apportioning a limited set of resources (i.e. habitat, prey, cover) among an assemblage of competing species. A traditional approach often involves estimating interaction coefficients between species pairs to rank competitive abilities. However, these can rarely be estimated without extensive field work, and are often beyond the scope of management questions. Here we present a simple approach that relies on the quality of fish habitat and the size of the average individual to determine the competitive ability of a particular species relative to the fish community. This approach allows ecologists to define interaction strengths from a mechanistic foundation, and resource managers to predict how environmental change will affect levels of fishery production. We present this model for a riverine fish community, and demonstrate how the competitive abilities of two piscivores change as we move our focus from the main stem into a headwater tributary. We also present the multiple ways this model can be applied to common management scenarios.