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ESTIMATED CHANGES IN NATIVE FISH RICHNESS AND THE INDEX OF BIOTIC INTEGRITY IN WILLAMETTE VALLEY STREAMS
Citation:
Baker, J P., J Van Sickle, AND P. Haggerty. ESTIMATED CHANGES IN NATIVE FISH RICHNESS AND THE INDEX OF BIOTIC INTEGRITY IN WILLAMETTE VALLEY STREAMS. Presented at 2002 Joint Annual Meeting Oregon Chapters American Fisheries Society and the Wildlife Society, Portland, OR, February 14-16, 2001.
Description:
The landscape of the Willamette Valley differs greatly from that prior to European settlement. Forty-three percent of the Valley Ecoregion has been converted to agricultural uses; 13% for urban and residential development. How have these changes in land use/land cover (LULC) affected fish communities in Willamette Valley streams? We focused on two indicators of fish community condition: native fish richness and the Index of Biotic Integrity (IBI). Empirical models relating fish richness and IBI to landscape parameters were derived from recent survey data available for 151 streams. The models were applied to all 2nd to 4th order streams in the Valley (2389 km total stream length) using GIS coverages of 1990 and historical LULC. LULC in upstream riparian areas was a better predictor of fish community condition than was LULC in the entire watershed or LULC immediately adjacent to the sampled reach. LULC conversions in riparian areas mirror those that have occurred in the valley overall. Currently, 41% of the land area within 120-m buffers around all 1st to 4th order streams in the valley is used for agriculture; 10% for urban or residential development. As a result of these land conversions, the median native fish richness in 2nd to 4th order valley streams is estimated to have decreased from 6.7 species (6.1-7.2, 90% confidence interval) pre-European settlement to 4.9 species (4.6-5.1) in 1990. The median IBI for valley streams is estimated to have declined from 68 (61-75) to 47 (43-50).