Some Like It Cold: A General Habitat Association Model for Smallmouth Bass in Stratified Lakes

Abstract

Models describing associations between fish distribution and environmental or spatial gradients at the population level have the potential to be transferrable if model parameters are stationary among populations and over years. Further, population-level habitat association models represent the scale of effect—habitat relevant to within-population distribution and processes. Here we show that for a widely recognised warm water fish species (smallmouth bass; Micropterus dolomieu Lacepède, 1802), habitat use extends into the metalimnion and hypolimnion of lakes. Lake depth at net sites and temperature at capture depth were used to model habitat use in a multi-lake set (n = 11 lakes) and for a large lake with three surveys over a decade. In the multi-lake set, a depth model was top ranked with little difference among lakes. In the lake with multiple surveys over a decade, a quadratic temperature model was top ranked but resulted in among-year differences in occupancy levels at any given temperature. The second ranked depth model produced consistent occupancy patterns with depth and matched parameter values from the multi-lake model. This consistency points to a general habitat association model based on depth for smallmouth bass during the summer season. We provide guidance for habitat managers based on this stationarity.