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Published: 2004

Total Pages: 171

ISBN-13: 9780496123599

The greenback cutthroat trout (Oncorhynchus clarki stomias) is classified as a threatened subspecies under the U.S. Endangered Species Act. Non-native brook trout (Salvelinus fontinalis) displace greenback cutthroat trout in montane streams, but the mechanisms for displacement are not understood. In this study, data on population dynamics, body condition, and feeding ecology of greenback cutthroat and brook trout were used in investigating competition for food and predation as potential mechanisms for displacement of greenback cutthroat trout by brook trout. During 2000 and 2001, trout populations and physical habitat were surveyed at 10 stream reaches in the South Platte and Arkansas River drainages in Colorado. Study areas included sites with (1) cutthroat trout only, (2) brook trout only, (3) both species, and (4) both species with experimental removal of brook trout. Complementary techniques, including analysis of stomach contents, stomach fullness, body condition, and stable isotopes of C and N, were used to describe the trophic niche of each species across the 10 sites.