Monitoring Report: Bruneau Hot-spring Springsnail (Pyrgulopsis bruneauensis)

This report presents the 1994 monitoring results from four sites near the Indian Bathtub that contain populations of the Bruneau Hot-spring Springsnail (Pyrgulopsis bruneauensis). Three of these sites were monitored in 1990 and 1991 by Mladenka (1992), in 1992 by Robinson et al. (1992), and in 1993 by Royer and Minshall (1993). An additional seep at Site 3 was included in the 1994 monitoring efforts.

Populations were reduced drastically in Hot Creek (Site 1) by a major runoff event in July 1992 and have since failed to recover (Royer and Minshall 1993). Sites 2 and 3 appeared to have maintained population densities similar to those in previous years, with fluctuations being mainly attributable to seasonality of temperature. Site 3 (New Seep) maintained a highly variable population density. Temperatures were stable at sites 1 and 2. Temperatures at Site 3 were often below 24°c and may potentially affect local snail reproductive success.