Organochlorine Residues in Harp Seals (Pagophilus groenlandicus) Caught in Eastern Canadian Waters

From 1969 to 1971, 78 harp seals (Pagophilus groenlandicus), ranging in age from newborn to 18 years were obtained from the Gulf of St. Lawrence and the Newfoundland and Labrador coasts (Front). A further 12 seals captured in the Gulf died (in captivity) after being held for various periods of time.Total DDT and metabolites (Σ DDT) in the blubber of wild beaters and bedlamers from the Gulf were > 2 ppm, from the Front < 2 ppm. DDT levels increased to 8.7 ppm as the animals matured, and in females levelled off at 6.5 ppm when the breeding age was reached. Dieldrin levels were only 5% of those for Σ DDT, and did not accumulate appreciably in either wild or captive seals. PCB residues were only slightly less than Σ DDT and showed a similar increase with the age of the seal.Residues in tissues of captive seals were as much as eight times higher than in nature, indicating either that natural diets contain lower residues than the selected, often monospecific diet, or differing rates of assimilation of organochlorines in wild and captive animals. The differences between levels in wild seals from the Gulf and Front may offer evidence for sub-population groups in the harp seals of the North West Atlantic.In seals examined brain lipids contained between 7 and 20% of concentrations of all three chlorinated hydrocarbons found in the extractible fat of blubber, muscle, and liver, indicating a brain barrier.