DDE, PCB, AND MERCURY CONCENTRATION TRENDS IN LAKE-ONTARIO RAINBOW SMELT (OSMERUS-MORDAX) AND SLIMY SCULPIN (COTTUS-COGNATUS) - 1977 TO 1988

Whole body concentrations of DDE and total PCB in Lake Ontario smelt, and PCB concentrations in Lake Ontario sculpin, displayed no significant time trend from 1977 to 1988. Conversely, DDE concentrations in sculpin have decreased. Mercury concentrations in both smelt and sculpin whole fish samples decreased with a half life of about 10 years, similar to the rate of decrease in lake trout. The ratios of DDE and PCB concentrations in lake trout to those in smelt have decreased. This decrease correlates with a drop in lake trout lipid concentrations suggesting that food intake by trout may have decreased, and growth efficiency increased. DDE and PCB concentrations in both smelt and alewives were higher in the western end of Lake Ontario than in the eastern end, similar to the spatial trend observed for lake trout.