Lahontan Cutthroat Trout in Fragmented Watersheds

Locating pit tagged fish through the ice during winter.

We used contiguous whole stream surveys and Digital Elevation Models to examine how landscape topography and in-stream habitat affected the distribution, growth, and survival of Lahontan Cutthroat Trout (Oncorhynchus clarki henshawi) in a High Dessert Watershed. The work was carried out in a sub-basin of the Quinn River system, McDermitt Creek, which drains the sagebrush desert of southeastern Oregon and northern Nevada. Our results showed that topography affected LCT distribution in all reaches. LCT numbers were highest in areas with greater numbers of nick-points (the transition zones between less confined and more confined valley segments) and greater valley confinement. Additionally, in downstream portion of our headwater reaches, more LCT were found in nick-points than expected based on the availability of this habitat type. Our data suggest that hyporheic inputs may be high in such areas, thus providing LCT with shelter from warm water in the summer, anchor ice in the winter and shallow stream depths during all seasons.

We found greater trout growth, but lower survival, in relatively warmer and more open reaches than in cooler reaches. Additionally, undercut banks (predation shelter) were more important to trout in cooler stream reaches than in warmer ones, where habitat choice responded first to cold water upwelling (which was influenced by topography). Our results will be useful in identifying and describing areas of high quality LCT habitat in low order streams throughout the Great Basin, thus allowing informed management decisions to facilitate the recovery of the species.

Additional Research Information:

Landscape topography and the distribution of Lahontan cutthroat trout (Oncorhynchus clarki henshawi) in a high desert stream
by George D. Boxall, Guillermo R. Giannico and Hiram W. Li