Stream habitat and rainbow trout (Oncorhynchus mykiss) physiological stress responses to streamside clear-cut logging in British Columbia

The impacts associated with streamside clear-cut logging (e.g., increased temperatures and sedimentation, loss of habitat complexity) are potentially stressful to stream-dwelling fish. We examined stream habitat and rainbow trout physiological stress responses to clear-cut logging in north-central British Columbia using 15 streams divided into three categories: old growth (reference), recently logged (clear-cut to both banks 1-9 years prior to the study), and second growth (clear-cut 25-28 years prior to the study). We used plasma cortisol and chloride concentrations as indicators of acute stress, and interrenal nuclear diameters, impairment of the plasma cortisol response, and trout condition and length-at-age estimates as indicators of chronic stress. No statistically significant acute or chronic stress responses to streamside logging were found, despite increases in summertime stream temperatures (daily maxima and diurnal fluctuations) and a reduction in the average overall availability of pool habitat. Our observed stress responses were approximately an order of magnitude lower than what has previously been reported in the literature for a variety of different stressors, and trout interrenal nuclear diameters responses to the onset of winter were approximately five times greater than those to logging. The overall consistency of our results suggests that the impacts of streamside clear-cut logging are not acutely or chronically stressful to rainbow trout in our study area.