Potential Effects of Global Climate Warming on the Growth and Prey Consumption of Great Lakes Fish

We used fish bioenergetics models to assess the effect ofglobal climate warming on the growth and prey consumption of warm-, cool-, and coldwater fishes at three sites spanning the range of thermal environments in the Great Lakes. Historical air and water temperature data and projected air temperature changes from three global climate models were used as input to regression models, which generated projections of water temperature changes before and after climate warming that would result from a doubling in atmospheric CO2 concentration. The bioenergetics simulations indicated that annual growth by yearling fish would increase with climate warming if prey consumption increased, but would decrease if prey consumption was constant. Changes in growth would be most pronounced in spring and autumn owing to a lengthening of the period during which fishes may behaviorally thermoregulate to find their optimal temperature for growth. Fish unable to thermoregulate (e.g., due to hypolimnetic oxygen depletion) would undergo decreased growth or weight loss in summer in warmer areas of the Great Lakes, where near-surface water temperatures would increase above the fishesˈ optimum. We conclude that food web dynamics and the potential for thermoregulation will greatly influence the direction and magnitude of changes in fish growth as the climate warms.