The relationship between water temperature and bull trout distribution and abundance

An assessment of the relationship between bull trout abundance and stream temperature indicated that mean temperature was effective at describing bull trout abundance. Bull trout were always present where mean temperature was less than 10.0°C but were not present at any sites where mean temperature was greater than 12.0°C. Bull trout were the only salmonid present when mean temperature was less than 7.0°C, whereas the percentage of salmonids that were bull trout was variable at mean temperatures between 7.0 and 12.0°C. Bull trout densities greater than 10.0 fish/100 m2 occurred at mean temperatures between 5.7 and 8.6°C. Minimum groundwater temperature was found to be effective at describing the distribution of juvenile bull trout within small stream basins. Juvenile bull trout were always present when the minimum groundwater temperature was less than 4.1°C but were not present in any stream basins where the minimum groundwater temperature was greater than 6.1°C.