Effectiveness of Using Summer Thermal Indices to Classify and Protect Brook Trout Streams in Northern Ontario

Abstract

Abstract We tested five thermal indices for their ability to differentiate streams containing brook trout Salvelinus fontinalis from streams not containing brook trout in forested watersheds of the Precambrian Shield, northern Ontario, with the goal of identifying and protecting riparian areas of thermally sensitive trout streams during timber harvesting. Logistic regression was used to predict brook trout presence and absence, with maximum summer temperature, mean summer temperature, mean sampling temperature, mean maximum summer temperature, and thermal stability as independent variables. Brook trout streams were cooler and thermally more stable than non-brook-trout streams, but temperatures overlapped considerably between the two types of stream. Correct classification of streams ranged from 60.3% for summer temperature stability to 67.1% for maximum summer and mean sampling temperatures. The models yielded correct predictions more often for brook trout absence (∼80%) than for brook trout presence (≤50...