Movements of nonnative brook trout in relation to stream channel slope
Abstract.We provide new insights on the ability of naturalized brook trout Salvelinus fontinalis to ascend steep, headwater streams in the western USA. We tested hypotheses that upstream movements by brook trout are limited or absent in reaches of steep streams and are more prevalent and longer in gradually sloping streams. We compared brook trout movements in headwater streams in Idaho at sites with varied channel slopes (averages of <1-12%). After eradicating fish from 200-m stream sections, we assessed immigration of marked fish into these sections. Contrary to our hypothesis, upstream movements were more prevalent than downstream movements during the summer, even in steep streams. Marked brook trout ascended stream channels with slopes of 13% that extended for more than 67 m and 22% for more than 14 m; they also ascended a 1.2-m-high falls. Nearly vertical falls, rather than steep slopes per se, apparently inhibited upstream movements. Our hypothesis that upstream movements would decrease with increasing channel slope was partially supported; fish did not move as far upstream in steep as in gradual sites, and upstream movements through steep channels were dominated by larger fish (.135 mmtotal length). Immigration by marked fish smaller than 95 mm was uncommon in all sites. Slopes up to 13% do not ensure against upstream dispersal, although other mechanisms may inhibit brook trout invasion in steep channels. In very steep channels, fewer dispersing fish and slower upstream movement rates may increase the time required for successful invasion and reduce its likelihood of occurrence.
Requesting Print Publications
Publication requests are subject to availability. Fiscal responsibility limits the hardcopies of publications we produce and distribute. Electronic versions of publications may be downloaded, distributed and printed.
Please make any requests at email@example.com.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
- Our online publications are scanned and captured using Adobe Acrobat. During the capture process some typographical errors may occur. Please contact the SRS webmaster if you notice any errors which make this publication unusable.
- To view this article, download the latest version of Adobe Acrobat Reader.