Mercury in Fish of Natural Lakes of Northern Québec

Abstract

Mercury (Hg) concentrations in fish have been documented for over 180 sampling stations located in natural lakes and rivers of northern Quebec. Mean Hg concentrations were estimated for fish of standardized length and of the following species: longnose sucker (Catostomus catostomus), white sucker (Catostomus commersoni), lake whitefish (Coregonus clupeaformis), northern pike (Esox lucius), walleye (Stizostedion vitreum), and lake trout (Salvelinus namaycush). Mean concentrations for 400-mm non-piscivorous fish of various lakes, ranging from 0.05 to 0.30 mg kg-1, were always well below the Canadian marketing standard of 0.5 mg kg-1 wet weight. For piscivorous species, concentrations often exceeded this standard, with mean levels ranging from 0.30 to 1.41 mg kg-1 for standardized lengths of 400 to 700 mm (depending on the species). Inter-lake variability within the same region is important for all fish species, as estimated mean concentrations often vary by factors of 3 to 4 for neighboring bodies of water. In the Nottaway-Broadback-Rupert region, where lakes and rivers display a wide range of physical and chemical properties, higher fish Hg concentrations were usually found in bodies of water with high organic content as described by color and concentrations of tannins, as well as total and dissolved organic carbon.