The response of lake thermal stratification to climatic conditions and effects on fish growth

grantor: University of TorontoClimate change is expected to alter aspects of lake thermal stratification such as onset of stratification, epilimnion and hypolimnion temperatures and thermocline depth. Climate change effects on fish will likely be mediated through alterations to their thermal habitat. The long-term water temperature and meteorology data sets for South Bay of Lake Huron, Ontario, (1955-92) and for Lake Opeongo, Ontario, (1958-96) offer an empirical record of the historical covariations between climatic conditions, lake stratification patterns and fish growth. Generally, in warmer years the thermal structures of these lakes are characterized by an earlier onset of stratification, a warmer spilimnion, a shallower thermocline and a larger temperature difference between upper and bottom layers. These stratification patterns are associated with increased growth in smallmouth bass Micropterus dolomieui (warm water species), and in rainbow smelt Osmerdus mordax and yellow perch Perca flavescens (cool water species) and with reduced growth in lake trout Salvelinus namaycush (cold water species). The historical covariations between climatic conditions and stratification patterns between stratification patterns and fish growth suggest that climatic conditions filter to fish thorough the aspect of their thermal environment that is related to their behaviour or life history. The historical covariations provide patterns of association from which the response of thermal stratification and fish growth to climate change are forecast.Ph.D