Effects of trophic position and lipid on organochlorine concentrations in fishes from subarctic lakes in Yukon Territory

Concentrations of organochlorines in lake trout (Salvelinus namaycush), burbot (Lota lota), and northern pike (Esox lucius) from subarctic lakes in Yukon Territory varied significantly among populations, and these differences could not be ascribed to size or age of the fishes. For each species, lipid content and trophic positioning (measured by stable nitrogen isotope ratios; delta(15)N) were significantly differ-nt across populations, and the latter differences could not be attributed to variable delta(15)N at the base of the food webs. Across lakes, concentrations of Sigma PCB, Sigma DDT, chlorinated bornanes (CHB), chlordane (Sigma CHL), chlorobenzenes (Sigma CBZ), and hexachlorocyclohexane (Sigma HCH) in lake trout and northern pike muscle and burbot liver were significantly related to their delta(15)N. Th, slopes, of these log organochlorine delta(15)N relations were greatest for more lipophilic contaminants (Sigma PCB, Sigma DDT, CHB), indicating that they bioaccumulate to a greater degree than less lipophilic contaminants. Lipid significantly predicted organochlorine concentrations both within and among populations of lake trout, and the slopes did not vary significantly with contaminant lipophilicity. Among-lake differences in Sigma HCH in trout muscle were removed by adjusting concentrations by the covariate lipid. Lipid-adjusted concentrations of CHB, Sigma PCB, Sigma DDT, Sigma CHL, and Sigma CBZ in lake trout remained significantly different between lakes, and these differences were attributed to variable food chain lengths.