Ecoregion Description

122: Upper Snake

Major Habitat Type:

temperate upland rivers

Author:

Text modified from Abell et al. 2000. Freshwater Ecoregions of North America: A Conservation Assessment. Island Press, Washington, DC, USA.

Countries:

United States

Boundaries:

This ecoregion is defined by the Snake River above the 30,000-60,000 year-old Shoshone Falls, which serve as a total barrier to the upstream movement of fish (McPhail & Lindsey 1986). The ecoregion boundary lies about 50 km downstream of the falls in order to include the Wood River, a tributary to the Snake. The ecoregion is predominantly restricted to the southeastern part of Idaho, but also extends into eastern Wyoming, northeastern Nevada, and the extreme northwestern corner of Utah.

Drainages flowing into:

The Snake River is the largest tributary of the Columbia River, although prior to the Pleistocene it may have drained the Mohave Basin, Sacramento-San Joaquin system and Klamath River (McPhail & Lindsey 1986).

Main rivers or other water bodies:

In addition to the Snake River, major freshwater habitats include Jackson Lake and other lakes of Grand Teton National Park.

Topography:

Originating near the Continental Divide, the upper Snake River follows a course through a rugged landscape of mountain ranges, canyons and plains.

Climate:

The ecoregion’s climate is mostly semiarid in the Snake River Plain, with mean annual precipitation ranging from 200 - 255 mm. Mountain elevations can receive more than 1500 mm of annual precipitation during the winter months as snow (Clark et al. 1998).

Terrestrial Habitats:

Shrub-steppe is the dominant vegetation type throughout much of the ecoregion, including sagebrush (Artemisia spp.), wheatgrasses (Agropyron spp.) and Idaho fescue (Festuca idahoensis) (Franklin and Dyrness 1988). In the eastern edge of the ecoregion coniferous forest is the dominant vegetation type at higher elevations (Ricketts et al. 2000).

Fish Fauna:

More than twenty fish species are found in this ecoregion, many of which are found nowhere else in the Columbia River basin but are shared with the adjacent Bonneville ecoregion [127]. Only 35% of the fish fauna of the Snake River above Shoshone Falls, and 40% of the Wood River fish fauna, are shared with the lower Snake River (McPhail & Lindsey 1986).

Description of endemic fishes:

The Wood River contains the endemic Wood River sculpin (Cottus leiopomus), and in the Snake River between the Wood River and Shoshone Falls lives the endemic Shoshone sculpin (C. greenei) (McPhail & Lindsey 1986).

Other noteworthy fishes:

The Snake River sucker (Chasmistes muriei) is known from a single specimen collected from the Snake River below Jackson Lake, Wyoming, and is apparently extinct (McPhail & Lindsey 1986).

Other noteworthy aquatic biotic elements:

Additionally, the upper Snake is an area of high freshwater mollusk endemism; Frest and Johannes (1995) identify over twenty snail and clam species and subspecies of special concern, 15 of which are apparently restricted to single clusters.

Justification for delineation:

Ecoregion boundaries are taken from Abell et al. (2000) and are based on subregions defined by Maxwell et al. (1995).

References/sources:

Abell, R., Olson, D., et al. (2000). "Freshwater ecoregions of North America" Washington, D.C.: Island Press.

Clark, G.M., T.R. Maret, M.G. Rupert, M.A. Maupin, W.H. Low and D.S. Ott (1998). "Water Quality in the Upper Snake River Basin, 1992-1995"

Franklin, Jerry F. (1988)"Pacific Northwest forests" In Barbour, M.G.;Billings, W.D. (Ed.). North American terrestrial vegetation.. (pp. 103-130) Cambridge: Cambridge University Press.

Franklin, Jerry F. and C.T. Dyrness (1988). "Natural vegetation of Oregon and Washington" Corvallis, OR: Oregon State University Press.

Frest, T. J.,Johannes, E. J. (1995). "Interior Columbia Basin mollusk species of special concern" Seattle, WA: Deixis.

Maxwell, J. R., Edwards, C. J., et al. (1995) "A hierarchical framework of aquatic ecological units in North America (Nearctic Zone)". St. Paul, MN. North Central Forest Experiment Station, USDA Forest Service.

McPhail, J. D.,Lindsey, C. C. (1986)"Zoogeography of the freshwater fishes of Cascadia (the Columbia system and rivers north to the Stikine)" In Hocutt, C.H.;Wiley, E.O. (Ed.). The zoogeography of North American freshwater fishes. New York: John Wiley.

Ricketts, Taylor H. Dinerstein Eric Olson David M. Loucks Colby J. (1999). "Terrestrial ecoregions of North America: A conservation assessment" Washington, D.C.: World Wildlife Fund.