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Distribution and Population Characterization of Clinch Dace (Chrosomus sp. cf. saylori) in the Upper Clinch River System, Virginia
Moore, Michael James
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The Clinch Dace Chrosomus sp. cf. saylori is a species of minnow known from only two counties in Virginia. Prior surveys established the species' presence in just eight tributaries to the upper Clinch River. A management plan, which should include both population monitoring and habitat restoration, is still lacking for the species. Population monitoring must balance high detection probability with low risk of injury to captured individuals. I sampled 98 sites in 2014 and 2015 within the putative range of Clinch Dace to refine estimates of its distribution. I sampled 70 of the 98 sites with multiple gears and replication in an occupancy modeling framework. Clinch Dace occupied low-gradient headwater streams with relatively low conductivity in forested watersheds. My surveys uncovered two new tributaries occupied by Clinch Dace, and I was unable to find Clinch Dace in two historically occupied streams. Species detection probability was higher with backpack electrofishing than minnow trapping. N-mixture models suggest that Clinch Dace are more abundant in watersheds with high forest cover although forest cover is highly correlated spatially in the nested stream network. Density estimates from mark-recapture sampling suggest that Clinch Dace occur at low densities in approximately 31.5 km of headwater streams. The mean estimate of global population size was 6,706 individuals. Some populations could be affected by low genetic diversity. I conclude by developing a prioritization framework for restoration and protection of 15 candidate conservation areas. Managers should work with private landowners to implement best management practices in high priority watersheds.
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