Evaluating the Influence of Climatic and Hydrologic Variables on Fish Communities in Channelised Agricultural Headwater Streams in the Midwestern <scp>USA</scp>

ABSTRACT Channelised headwater streams are common in agricultural catchments in the Midwestern United States, Canada and Europe and serve as fish habitat despite being impacted by agriculture. The influence of climatic variables on fish communities in channelised agricultural headwater streams has not been documented. Our research objectives were to identify the relationship between fish community structure and climatic variables in channelised agricultural headwater streams in northeast Indiana and central Ohio and to determine if fish community structure is better predicted by climatic variables or stream variables. We sampled fishes, compiled climatic data and measured water temperature and several stream hydrologic variables from 10 channelised agricultural headwater streams in northeast Indiana and central Ohio for 14 years. Mixed effects modelling indicated that fish diversity and relative abundance of warmwater fishes, coolwater fishes, intermediate tolerant fishes, Cyprinidae, Percidae, invertivores and brood hiders were positively correlated ( p &lt; 0.05) with precipitation and fish abundance and the relative abundance of planktivores and guarder substrate choosers were negatively correlated ( p &lt; 0.05) with precipitation. Fish abundance and the relative abundance of invertivores, planktivores and brood hiders were positively correlated ( p &gt; 0.05) with air temperature. In general, stream variables were better predictors of fish community structure than climatic variables. Our results provide insights into the relationships of fish communities with climatic and stream variables in channelised agricultural headwater streams that can be applied to help prioritise monitoring and management strategies for these small streams.