Predicting the impact of climate change on the spatial pattern of freshwater fish yield capability in eastern Canadian lakes

Equations of fish yield in lakes as a function of mean annual air temperature have been published for lake whitefish, northern pike, and walleye. Using the contouring and modelling features of a geographic information system (Tydac Technologies' SPANS), we prepared maps of (i) species distribution, (ii) mean annual air temperature, and (iii) temperature increases predicted by the Goddard Institute for Space Studies' global climate model (GISS-GCM). We combined these maps with the yield equations for the three study species to form a regional model predicting the spatial distribution of yield capability in eastern Canada with and without climate change. The GISS-GCM predicts temperature increases of 2.5 to 7.7 °C (mean = 4.5 °C) in eastern Canada, midway between the values predicted by two other GCMs considered. The regional model predicts a substantial spatial re-distribution of fishery capabilities. Areas now supporting high yields become marginal and areas at the margin of, or outside, the current species range become optimal. Without efforts to prevent temperature increases or large artificial efforts to redistribute preferred fish species, Canadian freshwater fisheries will suffer major disruptions given the temperature increases predicted by the GISS-GCM.