Overview: The Columbia pebblesnail, or great Columbia River spire snail, is a member of the Hydrobiidae family, which includes several species of endangered aquatic snails. All species of this family have gills, and thus require streams with a relatively high dissolved oxygen content. Suitable streams for hydrobiid snails must be relatively pristine as well, since high turbidity levels may injure or clog their fragile gill tissue. Due to these requirements, the Columbia pebblesnail is only found in the colder, clear streams of the Snake-Columbia River system. Columbia pebblesnails graze on submerged gravel, scraping algae off the rocks with a toothed appendage called a radula. These snails are quite short-lived, usually reaching sexual maturity within a year, at which time they breed and die. Because about 90 percent of the population turns over annually, a disruption or disturbance during the breeding season can have devastating effects. Hydroelectric projects along the Snake and Columbia Rivers significantly reduced populations of this snail due to the increase of water agitation below dams as well as decreased levels of aquatic primary producers.
Distribution: Historically,
Columbia pebblesnails were widespread throughout the Lower Snake and Columbia
Rivers, as well as their larger tributaries. Today, however, this
species is limited to the relatively few reaches of the Columbia River
system that remain free-flowing. Recent surveys have confirmed the
presence of this species in a few sites along the Columbia, Okanogan, Wenatchee
and Methow Rivers in Washington, as well as the Deschutes River in Oregon,
and the Snake River in Idaho.
References:
Hershler, Robert and Terrence J. Frest, 1996. A Review of the
North American Freshwater Snail Genus Fluminicola (Hydrobiidae).
41 pages. Washington: Smithsonian Institution Press.
Neitzel, Duane A. and Terrence J. Frest, 1990. Survey of Columbia River
Basin Streams for Columbia Pebblesnail and Shortface Lanx.
Fisheries 15(2). 1990: pp. 2-3.