A Spatial and Temporal Evaluation of PHABSIM in Relation to Measured Density of Juvenile Atlantic Salmon in a Small Stream

Abstract

We evaluated the relationship between weighted usable area (WUA) predicted by the physical habitat simulation (PHABSIM) model and the population density of juvenile Atlantic salmon Salmo salar in Catamaran Brook, New Brunswick, Canada. Various temporal and spatial scales of study were used to establish whether a positive linear relationship existed. The PHABSIM model was applied to 19 sites representing four habitat types, and various streamflow scenarios were used to calculate the amount of available WUA. Maximum WUA values for different habitat types and different reaches usually occurred at flows representing 85% of mean annual flow. Fish densities at the 19 sites were estimated by electrofishing in the summer and late autumn for 3 years. Few positive, significant relations were established between Atlantic salmon density and WUA; r2 values ranged from 0.18 to 0.95, with the best relations occurring at the scale of habitat type (5 of 16 comparisons were significant, P < 0.05). The WUA values calculated from the 15-d average flow before fish sampling displayed the best associations with fish density.