Temperature selection by young lake trout after chronic exposure to PCB's and DDE

Temperature selection tests were conducted with fry of Lake Michigan lake trout (Salvelinus namaycush) exposed to PCB's, DDE and a combination of these contaminants in food and water at levels 25 times the ambient levels in plankton and water in Lake Michigan. The observed effect of the contaminants was a lowering of the preferred temperature. After 98 days of exposure, mean preferred temperatures were 10.3A?C for fry exposed to PCB's, 9.8A?C for those exposed to DDE, and 8.7A?C for those exposed to PCB's + DDE, as compared with 11.2A?C for control fry. Frequency distributions of residence temperatures were significantly (P < 0.01) different among all treatments. Such a change in the preferred temperature caused by a contaminant could reduce the energetic efficiency of a fish and thereby reduce growth and survival.