Distribution and ecology of the endemic and relict mollusc fauna of Idaho TNC's Thousand Springs Preserve

Call Number:

Keywords:

Abstract:

A freshwater mollusc survey of the Thousand Springs Preserve was conducted in late June and early July 1991. Seventy-three sites were formally defined, and many others were sampled less systematically. The Preserve's freshwater mollusc fauna comprises 22 taxa, one of which is nonnative. Three candidate mollusc species currently live on the Preserve, and a fourth may have done so until recently. Aside from candidate taxa, sizable colonies of four other sensitive mollusc species are Preserve inhabitants. The Preserve is currently the best protected refugium for all of these taxa and has the largest known occurrence of the Bliss Rapids snail. Available information on ecology and species biology of the middle Snake River endemic, relict, and sensitive cold water species is summarized. All taxa prefer and most are restricted to unpolluted, highly oxygenated, clear, and cold-water lotic habitats. Most species are lithophiles and perilithon grazers. Two are more characteristic of oxygenated mud substrates, one is primarily a detritivore, and several are at least partially periphyton grazers as well. The native middle Snake River cold-water mollusc fauna has suffered serious declines in recent years in both sites and abundance, primarily due to changes in water quality. Declines are also evident for most or all on the Preserve, but are not as severe as in the mainstem Snake River. Management and monitoring methods are suggested to stem declines, enhance populations, and increase basic biological knowledge of the Preserve's sensitive taxa. Competition with the introduced New Zealand mudsnail, Potamopyrgus antipodarum, may have negatively impacted some of the sensitive taxa. Improvement of water quality is the most feasible way to address this problem also. Fish predation seems unlikely to be a major problem tor the Preserve's sensitive molluscs. The Preserve has a small land snail fauna of at least 7 taxa. Fossil deposits indicate that at least one of the candidates may have been present on the Preserve for the last 12,000 years. The fossil mollusc fauna includes both land and freshwater taxa, perhaps indicative of cooler climates. At least two of the fossil taxa (one a candidate) could survive as relicts on the Preserve.

Notes:

ELECTRONIC FILE - Zoology: Invertebrates

Generic citation: Frest, T. J., and E. J. Johannes. 1992. Distribution and ecology of the endemic and relict mollusc fauna of Idaho TNC's Thousand Springs Preserve. Final Report. Deixis Consultants, Seattle, WA. 291 p. Prepared for: The Nature Conservancy of Idaho. Contract no.: IDFO 050291-A