A hierarchical approach to modeling the salmon and steelhead fisheries of the Columbia River Basin

Abstract

The Columbia River Basin is the site of a unique regional effort to rebuild populations of Pacific salmon and steelhead trout (Oncorhynchus spp.) that have suffered because of extensive hydroelectric development within the basin. This restoration effort is a highly expensive proposition with an uncertain outcome. Models are needed that can help ensure prudent expenditure of public funds by providing quantitative estimates of the projected impacts of alternate management strategies. As a guide for future model development, an integrated approach to constructing a three-level, nested hierarchy of models is proposed that addresses the varying information needs of resource managers, and is consistent with a hierarchical concept of ecosystem structure. Conceptually, models are arranged within the hierarchy according to the spatial and temporal resolution of the processes simulated by each model. Higher-level models impose constraints on lower-level models, while simultaneously incorporating the attenuated dynamics of the lower-level models. A single system model, at the highest level in the hierarchy, simulates the long-term dynamics (over several decades) of multiple species and stocks at a coarse level of resolution. At the next level, life-cycle models simulate the interannual dynamics of single species or stocks in more detail..