Case Study: Modeling Trout Population Response to River Management

This chapter describes the key characteristics of “inSTREAM” and how it represents adaptive trade-off decisions, and provides the background needed to understand its design and complexity. The initial purpose of inSTREAM was to assess how alternative reservoir operation rules, which produce different patterns of flow and temperature in downstream waters, affect populations of sympatric trout species. It quickly became apparent that such a model would also be useful for a variety of management applications and for exploring more general ecological questions. InSTREAM has evolved into a family of models, each focused on specific salmonid communities and management problems. These models have also proved useful as virtual laboratories for exploring more general questions, of both management and theoretical importance, for which inclusion of adaptive trade-off behavior is probably critical. These questions have included how multiple stressors interact to affect populations; how opposing effects of increased turbidity—reduced feeding success and reduced predation risk—interact to affect populations; how habitat fragmentation affects population persistence and size structure; and how useful habitat selection models are for predicting population responses.