Chlorinated hydrocarbon concentrations and the ecology and behavior of harbor seals in Washington State waters
Calambokidis, J., K. Bowman, S. Carter, J. Cubbage, P. Dawson, T. Fleischner, J. Shuett-Hames, J. Skidmore, B. Taylor, and S.G. Herman. 1978. Chlorinated hydrocarbon concentrations and the ecology and behavior of harbor seals in Washington State waters. (Select for PDF, 3 MB file) Final report to the National Science Foundation, Washington, D.C. 121pp.
The Pacific harbor seal (Phoca vitulina richardii), occurs along the north and west coasts of North America from the Bering Sea to northern Baja California, Mexico (Scheffer 1958). Scheffer and Slipp (1944) have done the most extensive study of the harbor seal in Washington State. More recent research in Washington State has focused on Gertrude Island in Southern Puget Sound and on the outer coast (Arnold 1968, Newby 1971, 1973a, 1973b, Johnson and Jeffries 1977).
Newby (1973a) reported a decline in the Washington State harbor seal population between 1942 and 1972 and the abandonment by this specie of the Nisqually Delta, previously a major haul out area of the harbor seal in Southern Puget Sound. Between 1923 and 1960 Washington State paid a bounty on harbor seals; over 10,000 were killed between 1947 and 1960 (Washington State bounty records). The Marine Mammal Protection Act of 1972 includes the harbor seal among the fully protected species.
Harbor seal behavior has been touched upon in most studies, with emphasis on activities at haul out areas (Venables and Venables 1955, 1957, 1959, Newby 1971, Bishop 1967, Scheffer and Slipp 1944). Certain aspects of behavior, e.g. mother-pup interactions, have been studied in detail (Finch 1966, Wilson 1974a), but behavior has not been fully described. Food habits were studied between 1927-1930 by Scheffer and Sperry (1931) but no comprehensive food habit study has since been reported.
The pupping season of harbor seals along the west coast of North America becomes progressively earlier both north and south Puget Sound (Bigg 1969b). The different seal haul out areas in Puget Sound, a complex network of channels and inlets, provides an excellent opportunity to further research the phenology of harbor seal pupping.
Newby (1971, 1973b) reported a high incidence of prenatal and neonatal deaths, including some associated with birth defects, in harbor seals from Gertrude Island in Southern Puget Sound. Arndt (1973) found significantly higher concentrations of the chlorinated hydrocarbon PCB (polychlorinated biphenyls) in the blubber and liver of harbor seals from Southern Puget Sound and Grays Harbor in Washington State, and speculated PCBs might be causing the high pup mortality. The distribution of PCBs in cottids, mussels, and sediment from Southern Puget Sound has been discussed (Mowrer et al. 1977). Highest concentrations of PCB were found at sites nearest industrial and populated areas.
Chlorinated hydrocarbons have been shown to cause reproductive failure in a variety of animals; the effects of PCB have been reviewed by Stendell (1976). Chlorinated hydrocarbons have been linked to premature births in California sea lions (Zalophus californianus). Interaction between these chemicals and disease agents is a possible mechanism (DeLong et al. 1973, Gilmartin et al. 1976). Helle et al. (1976b) found significantly higher concentrations of PCB and DDE in the blubber of ringed seals (Pusa hispida) that had uterine occlusions and stenosis than in females that did not. This population of ringed seals in the Baltic had been experiencing low reproductive success, apparently because of the occlusions. Similar uterine abnormalities were also seen in grey seals (Halichoerus gryphus) and harbor seals from the Baltic.
We investigated the ecology and behavior of harbor seals and the concentration of the chlorinated hydrocarbons PCB and DDE in harbor seals and their food in Washington State, from March 1977 through January 1978. Our primary objectives were too:
- Determine the distribution, habitat, and population size of harbor seals in Northern Puget Sound, Hood Canal, and extreme Southern Puget Sound.
- Examine the reproduction, including the pupping season and birth and mortality rate of harbor seals in these regions.
- Describe the behavior of harbor seals.
- Determine the principal fish species eaten by harbor seals in or study areas.
- Study the effect of human incursion on populations of harbor seals at our study areas.
- determine the distribution of PCB and DDE in tissues of harbor seals from different areas of Washington State and examine the possibility that a correlation exists between concentrations of contaminants and reproductive success.
- Determine the concentration of these contaminants in fish and harbor seal scat and examine the dynamics of contaminant accumulation in the harbor seal.