There is evidence that fish in Canadian wilderness areas exhibit elevated mercury levels because of the oligotrophic nature of the lakes they inhabit (BROUZES et al. 1977). D'ITRI et al. (1971) reported higher levels of mercury in trout from oligotrophic waters than in trout from eutrophic waters in unpolluted areas. They attributed part of the difference to differences in the food of the fish in the two types of waters. Position on the trophic scale is an important factor determining the degree of bioaccumulation of mercury by aquatic organisms, especially fish.

Elevated mercury levels have been reported in fish from three wilderness lakes in northern Maine (NORMANDEAU ASSOCIATES 1978). Concentrations exceeding 0.50 ~g/g were detected in the muscle tissue of many of the fish.

We report the levels of mercury in the muscle tissue of brook trout (Salvelinus fontinalis) and lake trout (S. namaycush) from three northern Maine lakes. Mercury levels in fish from two wilderness lakes in the same drainage basin were compared with each other, and in turn with those in fish from a lake in a separate drainage basin. The fish species composition in one of the wilderness lakes, Cliff Lake, is different from that in the other two lakes, enabling us to analyze the effects of trophic structure on mercury concentration in top carnivores. It is unlikely that mercury from agricultural, geological, or local industrial sources occurs in these lakes.