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RANGE AND DENSITY OF ALIEN FISH IN WESTERN STREAMS AND RIVERS, US
Citation:
Lomnicky, G. A., R M. Hughes, T R. Whittier, AND D V. Peck. RANGE AND DENSITY OF ALIEN FISH IN WESTERN STREAMS AND RIVERS, US. Presented at Oregon Chapter American Fisheries Society, Sunriver, OR, February 18-20, 2004.
Description:
Alien fish have become increasingly prevalent in Western U.S. waters. The EPA Environmental Monitoring and Assessment Program's Western Pilot (12 western states), which is based upon a probabilistic design, provides an opportunity to make inferences about the range and density of alien fish in streams and rivers across the West. Reported data includes 515 sites sampled during 2000 -2001. Fish status (native/alien) was determined using species ranges identified in the literature and was confirmed from voucher specimens. Alien presence and density, grouped by political and ecoregional boundaries, and by stream sizes are presented. Approximately 36% of the West's 209,381 km of stream containing alien fish with California harboring the most collected alien species (18). Twenty percent of the stream length contains greater than 50% aliens. Proportionally, 5th order streams are more likely to contain aliens than 1st order streams (75% vs. 25%). Brook trout and Brown trout are predominant aliens, each found in over 10% of the stream length. Other common aliens include common carp, green sunfish, fathead minnow, and rainbow trout. Three ecoregions were evaluated (Western Forest, Xeric and Plains). The Xeric region contained the fewest alien species (18) while the Western Forest and Plains contain 25 and 26 species respectively.