Movement Patterns, Habitat use, and Survivorship of Lahontan Cutthroat Trout (Oncorhynchus clarkii henshawi) in the Truckee River.

Abstract

Populations of Lahontan cutthroat trout (Oncorhynchus clarkii henshawi, hereafter LCT), along with most other cutthroat trout subspecies, are in decline throughout their range. Habitat fragmentation, hybridization, and competition with non-native salmonids are viewed as major threats to LCT. Understanding LCT movement and habitat use behaviors will be a useful step in the reintroduction and establishment of a naturally reproducing LCT population in the Truckee River. Little is known about the movement patterns of LCT, which are listed as threatened under the U.S. Endangered Species Act (ESA). In this work, weekly radio telemetry monitoring was used to examine movement patterns, habitat use, and survivorship of hatchery-reared LCT in a 16.5 km stretch of the mainstem Truckee River, Nevada, across three reaches separated by dams. Nearly all fish movements took place during autumn and winter tracking seasons with significantly higher total movement during the autumn.Fish weight did not influence total movement or home range size. Males and females did not differ in home range size or total movement. Turnover rates were higher for males than females; however the difference was not significant. Turnover rates were similar for LCT among reaches.Location in the watershed influenced total movement and home range sizes of fish, with fish moving the largest distances in the middle section (Crystal Peak Park) followed by the upper section (Fleish). Nearly all fish movements were in an upstream direction, into large pools formed below the dam structures. No fish moved upstream over dams/barriers. Fish used slow water habitat units more than fast water habitat units in all three sections. Body size also influences habitat use, with larger fish using pools more frequently than other habitat types. AIC model rankings indicated season, flow rates, and stream temperature covariates to have the most influence on survival. Monthly survival was lowest during the autumn season (October to January), which coincided with the lowest flow rates and temperatures during the entire study period. These results verify the mobility of LCT, highlighting the importance of barrier-free movement corridors within the Truckee River. The differential movement patterns between reaches could be useful to resource managers in future habitat restoration efforts and reintroduction attempts of LCT into the Truckee River.