Event Title

Quantification of Survival, Site-Fidelity, Abundance, and Trend for a Critical Population of Endemic Cutthroat Trout

Location

Eccles Conference Center

Event Website

http://water.usu.edu/

Start Date

3-27-2006 10:10 AM

End Date

3-27-2006 10:15 AM

Description

Most sub-species of cutthroat trout are imperiled. In order to understand factors affecting abundance, survival, site-fidelity, and trend, we selected a large population of Bonneville cutthroat trout (Oncorhynchus clarkii utah) from a river drainage characterized by high quality, connected habitat for long-term monitoring. We completed a population assessment including depletion-based abundance estimation and mark-recapture survival estimation (> 1,050 tagged fish). Cutthroat trout densities were >1,500 trout/km at high elevation sites and were substantially higher than most reported for other inland, streamtype cutthroat trout. Most fish demonstrated extremely high rates of site-fidelity (97% overall). Cormack-Jolly-Seber survival rates (SCJS) increased with age class and condition; across sites, Scjs ranged from 64% at high-elevation sites to 30% at lower elevation sites. Scjs was on average 86% greater than apparent survival, highlighting the utility of individual tags and a maximum likelihood modeling approach for estimating survival. Based on our time series, population growth rates appeared to be declining at three, increasing at one, and stable at two sites. Both survival rates and fish densities were consistently lower at sites where cutthroat were sympatric with exotic brown trout. Our results provide important conservation benchmarks and information critical for identifying limiting factors of cutthroat trout range-wide.

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Mar 27th, 10:10 AM Mar 27th, 10:15 AM

Quantification of Survival, Site-Fidelity, Abundance, and Trend for a Critical Population of Endemic Cutthroat Trout

Eccles Conference Center

Most sub-species of cutthroat trout are imperiled. In order to understand factors affecting abundance, survival, site-fidelity, and trend, we selected a large population of Bonneville cutthroat trout (Oncorhynchus clarkii utah) from a river drainage characterized by high quality, connected habitat for long-term monitoring. We completed a population assessment including depletion-based abundance estimation and mark-recapture survival estimation (> 1,050 tagged fish). Cutthroat trout densities were >1,500 trout/km at high elevation sites and were substantially higher than most reported for other inland, streamtype cutthroat trout. Most fish demonstrated extremely high rates of site-fidelity (97% overall). Cormack-Jolly-Seber survival rates (SCJS) increased with age class and condition; across sites, Scjs ranged from 64% at high-elevation sites to 30% at lower elevation sites. Scjs was on average 86% greater than apparent survival, highlighting the utility of individual tags and a maximum likelihood modeling approach for estimating survival. Based on our time series, population growth rates appeared to be declining at three, increasing at one, and stable at two sites. Both survival rates and fish densities were consistently lower at sites where cutthroat were sympatric with exotic brown trout. Our results provide important conservation benchmarks and information critical for identifying limiting factors of cutthroat trout range-wide.

https://digitalcommons.usu.edu/runoff/2006/AllPosters/11