Growth and contaminant dynamics of Lake Superior lake trout

Lean lake trout (Salvelinus namaycush) and the endemic siscowet are ecologi cally distinct phenotypes of char inhabiting Lake Superior To examine growt h and contaminant concentration dynamics of these fishes, and to assess the ir utility as indicators of environmental contamination, length, weight, es timated age, and muscle tissue lipid and organochlorine (OC) chemical conce ntration data were analyzed. Lean lake trout grew faster in length and weig ht than siscowet. Siscowet muscle tissue lipid concentrations were on avera ge greater than in lean lake trout and increased with length and age, while lean lake trout muscle tissue lipid concentrations decreased in larger, ol der fish. Polychlorinated biphenyls (PCBs) were the most often detected con taminant, found in 95% of the lean lake trout analyzed and 100% of the sisc owets. PCBs attained the highest concentration of the OC compounds quantifi ed, followed by p,p'-DDE, dieldrin, and trans-nonachlor, respectively. Sisc owet had greater total concentrations of PCBs at length than lean lake trou t, but siscowet and lean lake trout had similar concentrations of PCBs at a ge. Based on 1990s growth and contaminant data, it is estimated that an 88 cm total length (16-year-old) lean lake trout and a 62 cm total length (15- year-old) siscowet from Lake Superior will exceed the 2.0 mg/kg "Action Lev el" for total concentrations of PCBs set by the United States Food and Drug Administration. Study results show phenotypic differences in growth and co ntaminant dynamics between leak lake trout and siscowet, findings that may improve our understanding and management of Lake Superior's aquatic resourc es.