EFFECTS OF TROPHIC POSITION AND LIPID ON ORGANOCHLORINE CONCENTRATIONS IN FISHES FROM SUB-ARCTIC LAKES IN YUKON-TERRITORY

Concentrations of organochlorines in lake trout (Salvelinus namaycush) , burbot (Lota lota), and northern pike (Esox lucius) from subarctic l akes in Yukon Territory varied significantly among populations, and th ese differences could not be ascribed to size or age of the fishes. Fo r each species, lipid content and trophic positioning (measured by sta ble 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, co ncentrations of Sigma PCB, Sigma DDT, chlorinated bornanes (CHB), chlo rdane (Sigma CHL), chlorobenzenes (Sigma CBZ), and hexachlorocyclohexa ne (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 lipophi lic contaminants (Sigma PCB, Sigma DDT, CHB), indicating that they bio accumulate to a greater degree than less lipophilic contaminants. Lipi d significantly predicted organochlorine concentrations both within an d among populations of lake trout, and the slopes did not vary signifi cantly with contaminant lipophilicity. Among-lake differences in Sigma HCH in trout muscle were removed by adjusting concentrations by the c ovariate lipid. Lipid-adjusted concentrations of CHB, Sigma PCB, Sigma DDT, Sigma CHL, and Sigma CBZ in lake trout remained significantly di fferent between lakes, and these differences were attributed to variab le food chain lengths.