Influence of a small instream wood addition on fishes and hydrology in channelized agricultural headwater streams in central Ohio

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The Ohio State University

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Instream wood is important for fish in headwater streams because it promotes the development of pool habitat and provides cover from predators during periods of low flow in the summer. The benefits of large instream wood for fishes have been extensively documented. However, little is known about small instream wood (diameter < 10 cm, length < 1 m), and its influence on fish communities and hydrology in channelized agricultural headwater streams in the Midwestern United States. Understanding this influence on fishes and hydrology can lead to multiple-use management strategies within agricultural headwater streams that consider the needs of fishes and other aquatic wildlife in addition to the needs of agriculture. In July 2011, one site containing one treatment pool and one control pool was established within each of four channelized agricultural headwater streams within the Upper Big Walnut Creek watershed in central Ohio. I sampled fishes and collected hydrology measurements in each site weekly for two weeks. After this first sampling period (pre-small instream wood addition), four to six pieces of small instream wood were added to each treatment pool and left undisturbed for approximately one month. In August 2011, fish and hydrology sampling resumed weekly for two weeks (post-small instream wood addition). No differences in fish community structure or hydrology occurred between control and treatment pool before or after the addition of small instream wood. Although the instream wood addition did not influence fish communities or hydrology, my results and the results of similar studies suggest that there may be a “threshold” density at which instream wood may be added that would benefit fish communities without influencing hydrology.



instream wood, channelized streams, fishes, hydrology, stream ecology