Comparing the influence of different habitat factors on fish communities in channelized headwater streams in Indiana and Ohio

Background/Question/Methods

Conservation practices, such as herbaceous riparian buffers, pesticide management, and conservation tillage, are implemented to reduce nutrient, pesticide, and sediment loadings within agricultural streams. The impact of these practices is uncertain because previous studies have focused on evaluating the hydrological and chemical responses. Furthermore, the influence of water chemistry on stream communities is not well understood and creates further uncertainty regarding the impacts of conservation practices. Understanding the relative influence of different habitat factors on stream communities will assist with predicting the influence of conservation practices. We compared the influence of riparian habitat, instream habitat, and water chemistry on fish communities within channelized headwater streams in Cedar Creek, Indiana and the Upper Big Walnut Creek, Ohio. Our hypothesis is that physical habitat variables, such as riparian or instream habitat, will influence fish communities within channelized headwater streams more strongly than water chemistry. We measured riparian habitat, instream habitat, water chemistry, and fishes from July 2005 to November 2007. 
Results/Conclusions

Multiple regression analyses indicated that fish community structure was more strongly correlated with instream habitat than riparian habitat or water chemistry. We also observed that 11 fish community metrics, such as species richness and abundance, were positively correlated with a habitat gradient of water depth, wet width, and percentage herbaceous vegetation within the water. Our results suggest that agricultural conservation practices that alter the instream habitat of channelized headwater streams will exhibit a greater impact on fish communities than practices that do not alter the instream habitat.