Establishing Relationships Between Fish Traits and Capture Efficiency: Implications for Watershed-Scale Monitoring

The alarming trends in extinction rates of freshwater fishes require that stream researchers and managers act with a sense of urgency to devise sound conservation strategies. Aquatic organisms possess combinations of morphological, behavioral, and life-history traits that have evolved together for adaptations that maximize fitness. Understanding relationships between fish traits and the stream environment can improve sampling and monitoring protocols. Fishes that have similar morphology and behavior are assumed to have similar sampling-gear catchability. We used hierarchical clustering with bootstrapping to group stream fishes of the Ozark Highlands based on fifteen ecomorphological traits. Cluster analysis resulted in 8 distinct ecomorphological groups that reflected both the morphology and behavior of member species. We tested the assumption of equal catchability between fish species within each ecomorphological group by sampling with multiple gears across a range of environmental conditions. Results indicate that the equal catchability assumption is valid for seventy percent of the species across all groups. The groups containing Cyprinids will require additional splitting before proceeding with a watershed-scale capture-efficiency model. Additionally, we demonstrate how these ecomorphological groups are useful for identifying how combinations of life-history traits explain differences in abundance of similar stream-fish species across a flow-regime gradient.