Quantification of the Vital Rates, Abundance, and Status of a Critical, Endemic Population of Bonneville Cutthroat Trout

Abstract

Most subspecies of cutthroat trout Oncorhynchus clarkii are imperiled or extinct due to the combined effects of habitat degradation and interactions with exotic species. To quantify abundance and vital rates and evaluate trends, we selected a large population of Bonneville cutthroat trout O. clarkii utah from the Logan River of northern Utah, a river characterized by high-quality and connected habitat. Over a 5-year period, we completed a comprehensive population assessment, including depletion-based abundance estimates and a mark-recapture study (1,050 tagged fish) of site fidelity, growth, and survival. Population density exceeded 1,500 cutthroat trout/km at high-elevation sites; this is substantially higher than most other reported densities of inland, stream-type cutthroat trout. Fish demonstrated extremely high rates of site fidelity on average (92%; SE ¼ 6%), and growth rates were also high (up to 0.50 g/d; mean ¼ 0.09 g/d). Cormack-Jolly-Seber survival rates (fish ! 100 mm) increased with age-class (group effect) and condition (individual covariate) and ranged from over 64% at high-elevation sites to approximately 30% at lower-elevation sites. Population growth rates (k) appeared to be declining overall; however, 95% confidence intervals of k frequently overlapped 1.0, indicating high variability that limited conclusions about future status. Both survival rate and fish density were consistently lower at sites where Bonneville cutthroat trout were sympatric with exotic brown trout Salmo trutta. The continuity, connectedness, and large size of this habitat fragment of the Logan River have clearly contributed to the persistence of this population. Our results provide important conservation and recovery benchmarks for identifying rangewide limiting factors of cutthroat trout. We recommend a precautionary approach to management of this endemic and important population; potential options include habitat protection or restoration and the removal of exotic brown trout.

Movement Patterns, Habitat Use, and Survival of Lahontan Cutthroat Trout in the Truckee River

“…While the annual apparent survival rate of 0.36 found in this study was lower than survival rates for wild cutthroat populations, this is largely driven by the extremely low survival observed during January. If the estimate for apparent survival for January is removed, annual estimates of apparent survival for Lahontan cutthroat trout in the Truckee River would be 0.62, which is within the range of average survival rates for Bonneville cutthroat trout O. clarkii utah and bull trout Salvelinus confluentus of similar size and age (Budy et al 2007;Al-Chokhachy and Budy 2008). Ultimately, this suggests that conditions during January may be limiting Lahontan cutthroat trout, a pattern worth further investigation.…”

Annual Variation of Spawning Cutthroat Trout in a Small Western USA Stream: A Case Study with Implications for the Conservation of Potamodromous Trout Life History Diversity

“…Bonneville Cutthroat Trout are native to Spawn Creek and the Logan River watershed, which has been identified as one of the largest remaining strongholds of this subspecies (Lentsch et al 2000;Budy et al 2007). The majority of Bonneville Cutthroat Trout spawning in the upper Logan River likely takes place in Temple Fork and Spawn Creek (Budy et al 2007(Budy et al , 2012.…”

“…The majority of Bonneville Cutthroat Trout spawning in the upper Logan River likely takes place in Temple Fork and Spawn Creek (Budy et al 2007(Budy et al , 2012. Both resident and fluvial life history forms of Bonneville Cutthroat Trout spawn in Spawn Creek (Bernard and Israelsen 1982;Budy et al 2007).…”

“…The majority of Bonneville Cutthroat Trout spawning in the upper Logan River likely takes place in Temple Fork and Spawn Creek (Budy et al 2007(Budy et al , 2012. Both resident and fluvial life history forms of Bonneville Cutthroat Trout spawn in Spawn Creek (Bernard and Israelsen 1982;Budy et al 2007). The mean length of Bonneville Cutthroat Trout based on 5 years of electrofishing surveys throughout the watershed was 236 mm (SD = 44, n = 1,531: Budy et al 2007 upstream to a series of beaver dams ( Figure 1).…”

“…Both resident and fluvial life history forms of Bonneville Cutthroat Trout spawn in Spawn Creek (Bernard and Israelsen 1982;Budy et al 2007). The mean length of Bonneville Cutthroat Trout based on 5 years of electrofishing surveys throughout the watershed was 236 mm (SD = 44, n = 1,531: Budy et al 2007 upstream to a series of beaver dams ( Figure 1). All but the lower 200 m of this section of stream was fenced in 2006 to exclude cattle grazing (Hansen and Budy 2011).…”