Status of marine mammals in the Strait of Georgia, Puget Sound, and Juan de Fuca Strait and potential human impacts

Citation

Calambokidis, J. and R.W. Baird. 1994. Status of marine mammals in the Strait of Georgia, Puget Sound, and Juan de Fuca Strait and potential human impactsp 282-303 In: Review of the marine environment and biota of Strait of Georgia, Puget Sound, and Juan de Fuca Strait.Proceedings of the BC/Washington Symposium on the Marine Environment, January 13 and 14, 1994. (R.C.H. Wilson, R.J. Beamish, F.Aitkens, and J. Bell, Ed.). Canadian Technical Report of Fisheries and Aquatic Sciences No. 1948.

Abstract

Nine species of marine mammals commonly occupy the transboundary waters of British Columbia and Washington (BC/WA). Individuals of all species move across this international border. Of the four pinniped species common to these waters, harbour seals are the most numerous and the only one that breeds in the transboundary area. Approximately 27,000 harbour seals occur in the transboundary area, and the population has been increasing at 5-15% per year. Elephant seals are found in the transboundary area in small numbers, and their occurrence in the area has increased in recent years. The number of California sea lions in the area increased in the 1980s and appears to have stabilized. While declining through most of its range, the number of Steller sea lions which use this area appears to be stable, although well below historical levels. Of the five cetacean species common to the waters, harbour and Dall's porpoise are the most abundant and number in the several thousands. Harbour porpoise numbers in some areas have declined since the 1940s, though little data are availalbe to assess current trends in populations of these two species. Two populations of killer whales utilize the transboundary area. The 'resident' population is growing and is currently larger than it was prior to a live-capture program in the 60s and 70s. Over 20,000 gray whales migrate past the entrance to Juan de Fuca Strait and some individuals spend prolonged periods feeding during the spring and summer in BC/WA waters. A small number of minke whales use this area for feeding, primarily during the spring, summer, and fall.

Marine mammals are vulnerable to human activities in the BC/WA transboundary waters. High concentrations of contaminants, especially chlorinated hydrocarbons and some metals, have been identified in these animals. Highest concentrations of contaminants have been found in harbour seals (from southern Puget Sound), harbour porpoise and killer whales. Determination of the impacts of these contaminants on marine mammals in these waters has been inconclusive, though in other areas contaminant exposure has been linked to reproductive failure and immunosuppression. Marine mammals are killed incidental to commercial fishing operations, particularly harbour porpoise and Dall's porpoise. Information to assess human impacts on most marine mammals and to adequately evaluate their current status is extremely limited.

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