Trends of legacy and emerging-issue contaminants in Lake Simcoe fishes

The temporal trends of legacy contaminants (i.e., mercury, PCBs, and DDT) and the current status of both legacy and emerging-issue (polybrominated diphenyl ethers (PBDEs) and polychlorinated naphthalenes (PCNs)) chemicals were examined in sport fishes from Lake Simcoe. Mercury concentrations decreased statistically significantly with time in lake trout, cisco, smallmouth bass, and yellow perch, consistent with assumed loading patterns. In contrast, mercury in largemouth bass, northern pike, and walleye showed a random relationship with time and increased statistically significantly with time in whitefish. Such differences among species suggest the influence of food-web processes (e.g., nutrient inputs and invasive species) in controlling temporal patterns of mercury in Lake Simcoe fishes. Concentrations of total-PCB and total-DDT in lake trout and whitefish generally followed an exponential decay pattern, with concentrations stabilizing during the 1990s. Current concentrations of legacy contaminants were, for the most part, below fish consumption guidelines for the general population. The risk associated with fish consumption to the sensitive population of women of child bearing age and children under 15 was of more concern for the larger, predatory fishes due to elevated mercury and PCBs. Recent measurements of PCNs and PBDEs were not of concern to Lake Simcoe sport fish consumers, although continued monitoring of fish contaminant levels is recommended in light of possible further loadings to this system. Contaminant related issues in Lake Simcoe sport fishes were of less or similar concern compared with the North American Great Lakes.