PCBs, mercury, and organochlorine concentrations in lake trout, walleye, and whitefish from selected tribal fisheries in the Upper Great Lakes region.

The purpose of this study was to determine the concentrations of environmental contaminants in the edible portion of fish tissue consumed by Ojibwa residing in the Upper Great Lakes region. Lake trout, whitefish, and walleye were collected from Lake Superior, Lake Huron, Lake Michigan, and selected inland lakes. These fish were harvested by either commercial fishing or spearfishing techniques and analyzed for environmental contaminants. Samples were pooled by species and location of collection and were analyzed as composites. The concentrations of congener-specific polychlorinated biphenyl (PCB), total mercury, and 17 other organochlorine compounds of the pooled samples were determined using gas chromatographic and atomic absorption techniques. Differences were noted in both the concentration and composition of contaminants depending on the geographic location of collection and the species examined. Lake trout and whitefish contained higher concentrations of organochlorine compounds than did walleye; and samples from Lakes Michigan and Huron had much higher concentrations than did Lake Superior fish. Conversely, mercury was much higher in walleye (580 ppb) when compared with lake trout (117 ppb) and whitefish (10 ppb). Several PCB congeners were commonly found in all fish samples; these included PCBs 138 + 163, 153, 66 + 95, 118, 77 + 110, 180, and 101. Lake trout accumulated the highly chlorinated PCB congeners, whereas walleye and whitefish accumulated certain lower tri- and tetrachlorobiphenyl congeners. In conclusion, the fish harvested and consumed by Ojibwa tribal members contained both mercury and organochlorine compounds. The concentrations of contaminants found in fish tissue differed among species and sampling sites. Consequently, it is imperative to sample fish that best represent those being consumed by tribal members and to continue long-term monitoring of fish from ceded waters. Therefore, risk assessment and risk management strategies need to take into account geographic location of the fish and unique preparation methods and to be directed at the contaminant(s) of concern for given locations. Copyright 2002 Wiley Periodicals, Inc.