Short-Term Effects of Beaver Dam Removal on Brook Trout in an Appalachian Headwater Stream

In North America, Castor canadensis (Beaver) impoundments of low-order streams greatly modify ecological processes, influence stream biota, and impact fish movement. We evaluated the short-term effects of removing a beaver dam from an Appalachian headwater stream on a Salvelinus fontinalis (Brook Trout) population. Prior to dam removal, we found only one marked trout that had navigated the dam moving upstream and no marked trout from above the dam moving downstream. Immediately following dam removal, trout abundance above and below the dam increased 67.1% and 46.0%, respectively. During later samples, however, declines in both trout abundance and relative weight suggest the initial large increases in our study sections after dam removal may have led to increased competition among trout, causing large numbers to move several hundred meters further upstream, beyond our study site, in order to find acceptable habitat. These results demonstrate that the presence and subsequent removal of a beaver pond on a Brook Trout stream can be considered both beneficial and harmful; thus, site-specific evaluation is necessary to determine best whether to retain or remove ponds.