Associations of stream water acidity and other environmental factors with the spatial distribution of Brown Trout in a mesoscale boreal stream network

Boreal stream networks are embedded in a mosaic of wetlands and lakes interspersed in the forest landscape. This mosaic results in complex and dynamic water chemistry that varies depending on stream size, catchment characteristics, season and flow. Spatiotemporal variations in stream acidity are however frequently predictable based on spatial patterns in the terrestrial watershed, and acidity has been found to limit the spatial distribution of brown trout (Salmo trutta) in some Scandinavian streams. This study compares the distribution of brown trout with stream acidity and other environmental factors using 47 sites distributed throughout the Krycklan stream network, a 67 km boreal catchment in northern Sweden. We tested whether local factors (stream water chemistry and stream site physical habitat from field surveys) or large-scale factors (whole-catchment characteristics derived from a GIS) were more closely correlated with the spatial distribution of brown trout as determined by electrofishing survey.