Walleye, whitefish and whitefish livers, lake trout, and siscowet lake trout were collected from the Apostle Islands Region of Lake Superior. Carp were obtained from a Lake Michigan tributary near Oshkosh, Wisconsin, USA. Each fish species was analyzed for 89 polychlorinated biphenyl congeners, 12 selected organochlorines, and total lipids. Congener profiles varied greatly between the fish species. Carp and whitefish contained tri‐ and tetra‐chlorobiphenyl congeners, such as 28 + 31, 63, and 66+95 in the highest concentrations. Siscowet trout contained the more heavily chlorinated penta‐, hexa‐, and hepta‐chlorobiphenyl congeners such as 153, 89, 138 + 163, 180, 182 + 187, and 170. In addition to the highly chlorinated PCB congeners routinely examined in Great Lakes fish, many lower chlorinated, ortho‐substituted PCB congeners are also commonly found. These lower chlorinated congeners have known effects in laboratory animals but may be overlooked by analytical techniques in which Aroclor standards or mixtures of selected congeners are used for quantitation. A congener‐specific approach including both the lower chlorinated ortho‐substituted PCB congeners and the more highly chlorinated congeners should be implemented to better assess the interactions and toxicities of individual congeners and other persistent compounds.

Abstract-Walleye, whitefish and whitefish livers, lake trout, and siscowet lake trout were collected from the Apostle Islands Region of Lake Superior. Carp were obtained from a Lake Michigan tributary near Oshkosh, Wisconsin, USA. Each fish species was analyzed for 89 polychlorinated biphenyl congeners, 12 selected organochlorines, and total lipids. Congener profiles varied greatly between the fish species. Carp and whitefish contained tri-and tetra-chlorobiphenyl congeners, such as 28ϩ31, 63, and 66ϩ95 in the highest concentrations. Siscowet trout contained the more heavily chlorinated penta-, hexa-, and hepta-chlorobiphenyl congeners such as 153, 89, 138ϩ163, 180, 182ϩ187, and 170. In addition to the highly chlorinated PCB congeners routinely examined in Great Lakes fish, many lower chlorinated, ortho-substituted PCB congeners are also commonly found. These lower chlorinated congeners have known effects in laboratory animals but may be overlooked by analytical techniques in which Aroclor standards or mixtures of selected congeners are used for quantitation. A congener-specific approach including both the lower chlorinated ortho-substituted PCB congeners and the more highly chlorinated congeners should be implemented to better assess the interactions and toxicities of individual congeners and other persistent compounds.