Threatened Bliss Rapids snail's susceptibility to desiccation: Potential impact from hydroelectric facilities

Water levels in the regulated Snake River, southern Idaho, U.S.A. can fluctuate daily and seasonally due to hydroelectric demands. The federally listed threatened Bliss Rapids snail, Taylorconcha serpenticola Hershler et al., 1994 (Family: Hydrobiidae), survives in and near these fluctuation zones. Remaining T. serpenticola populations occur only in sections of the Snake River that are impacted by these hydroelectric facilities and associated springs. Because effects of rapid draw-down in fluctuation zones on T. serpenticola are unknown, we conducted a laboratory experiment to evaluate potential impacts of desiccation. Our experiment compared desiccation resistance at several air temperatures, on dry and wetted substrates, and for ‘small’ vs. ‘large’ snails. Probit regression-maximum likelihood models estimated lethal time (LT50) values. Survival was significantly greater on wetted substrate than on dry substrate and was lowest at temperatures <0°C and at 37°C on dry substrate. Survival was greatest at 17...