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A BIOINTEGRITY INDEX FOR COLDWATER STREAMS OF WESTERN OREGON AND WASHINGTON
Citation:
Howlin, S., R M. Hughes, AND P R. Kaufmann. A BIOINTEGRITY INDEX FOR COLDWATER STREAMS OF WESTERN OREGON AND WASHINGTON. TRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY. Allen Press, Inc., Lawrence, KS, 133:1497-1515, (2004).
Description:
We created, tested, and applied an index of biological integrity (IBl) for fish and amphibian assemblages in coldwater streams of the Oregon and Washington Coast Range. A randomly selected set of 104 wadeable sites was quantitatively sampled for fish and amphibian assemblages, and physical and chemical habitat from 1994-1996. Natural gradients and anthropogenic disturbances were assessed through use of existing digital data for road density and vegetation cover at the catchment scale, along with site scale habitat data. A set of 109 candidate metrics were evaluated for variance properties and responsiveness to multivariate measures of disturbance, resulting in the selection of 8 metrics. The IBI itself was subsequently evaluated for variance and responsiveness to disturbance, then compared against an independently selected set of reference sites that had minimal anthropogenic disturbance. Our IBI was fairly precise, with a signal/noise ratio of 4.7, and significantly correlated with multivariate estimates of anthropogenic and elevation/anthropogenic disturbance. Reference sites had significantly higher IBI scores than the non-reference sites. Using this IBI, we assessed biological integrity in the Coast Range, inferring our results to all mapped (1:100,000- scale) wadeable streams in this region. Depending on the biological criterion used, 35% - 82% of stream kilometers (7,924 - 18,500 km) were classified as impaired. High IBI scores clustered near national parks and wilderness areas.