PARENT SESSION
Session #2: Local ecosystem effects of climate change: The interaction between climate, societal decisions, and ecosystems. Organized by: J.S. Baron, D.S. Ojima, N.T. Hobbs, and A.C. Covich.
Monday, August 6, 2001. Madison Ballroom A

Climate change and implications for the recovery of greenback cutthroat trout in Colorado.

Covich, Alan^1,2, Cooney, Scott¹, Harig, Amy¹, Fausch, Kurt¹, ^{1 2}

ABSTRACT- If rapid directional changes in climate significantly alter regional hydrology and temperatures over the next several decades, distributions of native fishes will likely be altered. We examine how increases in water temperature may be linked to future distributions of the federally listed greenback cutthroat trout (Oncorhynchus clarki stomias ) in the Rocky Mountains of Colorado. Low summer temperatures as well as habitat size and quality appear to limit greenback distributions. Current populations persist only in remote high-elevation habitats above steep waterfalls that restrict access to these rivers and lakes by non-native salmonids. Present greenback distributions apparently have been greatly modified through competitive displacement by introduced species as well as by physical factors such as water depth and temperature. Establishing additional stable populations of greenbacks through translocation is a current strategy for expanding their geographic range. These restoration plans must consider how climate change may either enhance or degrade high-elevation habitats. Earlier peak discharge from more rapid snow-melt and warmer water temperatures during summer months may increase available habitat for greenbacks in some locations. Using data from streams currently with greenbacks, we developed regression models to predict mean July water temperatures as a function of pool morphology, number of pools, channel length, watershed area, slope, and aspect. These habitat variables were then related to thermal tolerance, temperature preference, and the number of degree days needed for growth and over-winter survival of the young-of-the-year age class. If river waters warm over several decades at high elevations, some current greenback sites are predicted to have reduced habitat availability, while other additional new, high-elevation sites would likely provide stable populations, once non-native species are excluded from these topographically complex habitats.

KEY WORDS: climate warming, native species conservation, thermal preferences