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THE RELATIONSHIP BETWEEN TEMPERATURE, PHYSICAL HABITAT AND FISH ASSEMBLAGE DATA IN A STATE WIDE PROBABILITY SURVEY OF OREGON STREAMS
Citation:
Herlihy, A. T., P R. Kaufmann, D P. Larsen, AND R M. Hughes. THE RELATIONSHIP BETWEEN TEMPERATURE, PHYSICAL HABITAT AND FISH ASSEMBLAGE DATA IN A STATE WIDE PROBABILITY SURVEY OF OREGON STREAMS. Presented at Oregan Chapter annual meeting, American Fisheries Society, Sunriver, OR, February 26-March 1, 2002.
Description:
To assess the ecological condition of streams and rivers in Oregon, we sampled 146 sites
in summer, 1997 as part of the U.S. EPA's Environmental Monitoring and Assessment Program.
Sample reaches were selected using a systematic, randomized sample design from the blue-line network depicted on 1: 100,000 scale USGS maps. Reaches were sampled for a number of indicators including fish assemblages, water temperature, and physical habitat. Continually recording temperature monitors were placed in 90 of the study sites. In this subpopulation, 48% of the stream length exceeded Oregon's 17.8 C temperature criterion. Across the state, a simple multiple regression model using watershed area, bankside canopy cover, mean depth, and residual pool volume predicted the summer maximum 7 day average temperature with an R~0.71 (RMSE=2.5 C). Cutthroat trout and rainbow trout were the two most common species in Oregon (found at the most sites). Using estimates from the probability design, salmonids were observed in 86% of the 13,500 km of stream east of the Cascade Crest and in 66% of the 41,700 km of stream west of the Cascade Crest. When looked at regionally, salmonid presence/absence and abundance (catch per unit effort) were only weakly related to either the stream temperature at the time of sampling or the 7 day average maximum temperature during the summer. Habitat variables like stream substrate composition, stream size, and nutrient concentrations were more strongly related to salmonid abundance than temperature.