Fish Responses to Flow Alteration Metrics

Numerous studies have attempted to identify metrics that best represent hydrologic alteration, but there is no consensus on how these hydrologic indices are linked to ecological processes and fishes.  We conducted a literature review with the primary objective to identify biological responses of fish, which are linked to stream flow and stream flow alteration metrics.  We summarized metrics used to link flow alteration to direct biological responses from over 400 references from peer-reviewed literature, agency reports and flow assessment programs from 1980 to 2011.  Completion of our literature review identified less than 100 studies that directly related biological responses to flow.  Of these, 42 studies linked biological responses of fish to flow alterations.  Our review identified over 300 occurrences of stream flow metrics used and approximately 200 significant biological responses to varying flow components.  More common metrics linked to biotic responses included changes in mean annual flow, peak flows, low flows and flow variability.   The most common biotic metrics linked to stream flow included abundance and diversity metrics.  Our review will help identify future research needs and help managers identify specific stream flow metrics associated with biotic responses that can be incorporated into ecological flow assessments.