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IBI METRIC DEVELOPMENT FOR STREAMS AND RIVERS IN WESTERN FORESTED MOUNTAINS AND ARID LANDS
Citation:
Whittier, T R., R M. Hughes, AND G. A. Lomnicky. IBI METRIC DEVELOPMENT FOR STREAMS AND RIVERS IN WESTERN FORESTED MOUNTAINS AND ARID LANDS. Presented at Oregon Chapter American Fisheries Society, Sunriver, OR, February 18-20, 2004.
Description:
In the western USA, development of metrics and indices of vertebrate assemblage condition in streams and rivers is challenged by low species richness, by strong natural gradients, by human impact gradients that co-vary with natural gradients, and by a shortage of minimally-disturbed reference sites in mid- to low-elevation streams and medium to large rivers. The indicator development process benefits by an evaluation of assemblage data at sites representing the least- disturbed and the most-disturbed conditions along the range of natural gradients. We compared vertebrate assemblage characteristics from least-disturbed and most-disturbed sites sampled by EMAP in the Forested Mountains and Arid Lands ecoregions of the West to guide the development of quantitative metrics and indices of condition. We selected these sites to encompass the primary natural gradients of elevation, slope and stream size typical of the West. In small, mid- to high-elevation streams we were unable to construct reliable metrics because no vertebrates were collected at about half of the sites, regardless of stream condition. Least disturbed medium-sized streams in the forested mountains ecoregions had numerous native salmonids along with one or two moderately intolerant native benthic fish species, and in some areas, an amphibian species. Most-disturbed sites had few or no native salmonids and tolerant native sucker species, or non-native and/or land-based amphibians. Least-disturbed large rivers sites had one or more native salmonids, and upwards of five other native species which include intolerant or moderately intolerant benthic species, while most-disturbed sites had large numbers of non-natives, and tolerant species, and lacked native salmonids.