Spatial distributions of 33 fish species in the mainstem rivers of the south Saskatchewan river basin under changing thermal regimes

Abstract

The impact of climate change on longitudinal distributions of 33 fish species in the mainstem rivers of the South Saskatchewan River Basin was assessed. Mean July water temperature was the most common variable in multivariate logistic regression models of present-day species' presence followed by slope, nitrate-nitrite, phosphate, turbidity, and channel width. Most water control barriers in the rivers cause an abrupt change in the presence of at least one fish species. Most species' associations were positive, but may not be due to causal relationships. Water temperatures were estimated using a downscaled model of air and water temperatures using climate scenarios from CRCM 3.5 for 2040 and 2080. Local extinctions were predicted for five species and major habitat losses were predicted for three more species under future climates. Substantial expansions in ranges were predicted for eight warm-adapted species and one cool­adapted species. Water control barriers altered future distributions of six species.