Integrating Expert Workshops and Causal Criteria Analysis to Develop General Flow-Ecology Hypotheses for Riverine Fishes

The fast pace of flow regime alteration, and the dire state of aquatic biota across the globe, requires development of regional environmental flow recommendations for rivers. The Ecological Limits of Hydrologic Alteration (ELOHA) framework synthesizes available information into ecologically based and socially acceptable goals by developing flow-ecology hypotheses for discrete stream types, and providing evidence from existing data for these relationships to support environmental flow recommendations. We present a set of fish target groups and related flow-ecology hypotheses that have emerged from expert workshops conducted for multiple ELOHA projects in the northeastern United States. Their transferability among projects suggests these general fish target groups and hypotheses may serve as a robust starting point for other ELOHA projects at regional or larger scales. However, difficulties associated with demonstrating cause-effect relationships in natural systems limit our ability to test many of these hypotheses. We used causal criteria analysis to assess the level of support from the published literature for each hypothesis. Results will support environmental flow projects by identifying broadly applicable flow-ecology hypotheses that are well supported, and identifying hypotheses with less support that can be targeted for future research.