Document Type

Article

Publication Version

Version of Record

Publication Date

2010

Departmental Paper Identifier

550-F

Abstract

The aquatic nuisance diatom Didymosphenia geminata was established in Rapid Creek in the Black Hills of South Dakota in 2002. Shortly thereafter, large declines (>50%) of the naturalized brown trout Salmo trutta population were observed. We evaluated the influence of water resources and D. geminata on (1) declines in brown trout biomass, (2) changes in food resources, and (3) diet of brown trout in Black Hills streams. Drought conditions were largely responsible for trout declines in Black Hills streams. However, comparison of brown trout sizestructure between the pre-D. geminata and post-D. geminata periods revealed that juvenile brown trout abundance increased while adult abundance decreased in Rapid Creek. Changes in food resources in D. geminata-impacted areas were thought to favor juvenile brown trout and negatively impact adults. In the presence of D. geminata, macroinvertebrate abundance was composed of fewer, larger taxa and higher numbers of smaller taxa (i.e., chironomids). Brown trout in Rapid Creek consumed fewer ephemeropterans and a high amount of dipterans. Nonetheless, diet analysis showed that brown trout in Rapid Creek consumed as much or more prey than trout from two other streams unaffected by D. geminata. Moreover, relative weight of brown trout from Rapid Creek was high (>100), implying that food availability was not limiting. These findings imply that D. geminata did not negatively impact feeding and condition of brown trout in Rapid Creek, although mechanisms affecting size-structure in Rapid Creek remain unknown.

Publication Title

Proceedings of the Wild Trout X Symposium - Conversing Wild Trout

First Page

169

Last Page

175

Format

application/pdf

Language

en

Rights

A work produced within the official duties of an employee of the United States Government are not subject to copyright within the U.S.

Download

Share

COinS