Do introduced brown trout affect native fishes in western United States streams?

Authors: Nora K. Burbank, Charles P. Hawkins

Year: 2010 (xlii)

Abstract

Introduced brown trout (Salmo trutta) are known to negatively affect native fish species. However, these effects have typically been observed in systems where other trout species are absent. In many North American streams, fish species have evolved with other Salmonids, and it is unclear what effects brown trout have on these species. We analyzed the relationship between brown trout and the distribution and abundance of sculpins (Cottus spp.) and speckled dace (Rhinichthys osculus) to assess if brown trout have affected these native species. We used the same methods to analyze the relationship between native cutthroat trout (Oncorhynchus clarkii) and sculpins and speckled dace to see how the effect of brown trout compares to the effect of a native trout species. We found that sculpins were positively associated with cutthroat trout, but not associated with brown trout. For speckled dace, we found no relationship with brown trout, and a weakly negative relationship with cutthroat trout. The lack of a negative relationship with brown trout implies that sculpins and speckled dace possess behaviors and/or adaptations that allow them to coexist with brown trout.