Context-dependent responses of juvenile Atlantic salmon ( Salmo salar ) to forestry activities at multiple spatial scales within a river basin

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Deschênes, Julie, Rodríguez, Marco A, Bérubé, Pierre
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2007
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Canada; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1139/f07-077; http://www.nrcresearchpress.com/doi/pdf/10.1139/f07-077

We used classification trees and regression trees to relate the incidence and density of juvenile Atlantic salmon (Salmo salar) to forestry activities measured at four spatial scales (subbasin and 8, 2, and 0.5 km radii upstream of study sites) and environmental features in 120 stream reaches of the Cascapedia River basin, Québec, Canada. At all scales, incidence increased with reach size and accessibility to the reach from the river mainstem. Incidence declined with areal coverage of logging at all scales, but only in larger reaches. The time horizon over which logging effects were detected increased with spatial scale. At all scales, density in salmon-bearing reaches increased with accessibility. Density in more accessible reaches was negatively related to logging over the preceding 9 years at the subbasin and 8 km scales, but no effects of logging on density were detected at the 2 and 0.5 km scales. Overall, apparent effects of logging activities on salmon incidence and density were mostly negative and strong, but were both markedly scale-dependent and conditional on environmental context.