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Recovery Strategy for Blue, Fin, and Sei Whales in Pacific Canadian Waters [Proposed]

5. Threats

Blue, fin, and sei whales share both historic and current threats. These species are currently threatened by a variety of anthropogenic sources, including ship strikes, acute and chronic noise, possible pollution effects, and fishing gear interactions. The influence of some or all of these threats may result in reduced use of available habitat and/or reduced reproduction. Habitat may also be altered by medium and long-term shifts in ocean climate.

5.1.  Whaling

Commercial whaling devastated the populations of blue, fin, and sei whales in every ocean of the world in less than 80 years. Whaling continues in a variety of forms including subsistence hunts and scientific research (Clapham et al. 1999). Recent genetic analysis of midden contents in the Pacific Northwest indicate that aboriginal whaling in Pacific Canadian waters did not target balaenopterid species (A. D. McMillan, personal communication. Department of Anthropology, Douglas College, P.O. Box 2503, New Westminster, BC, V3L 5B2). Scientific whaling (i.e., by Japan) is likely to remain directed at more abundant species (i.e., minke, Bryde’s and sperm whales (Physeter macrocephalus)). Therefore whaling is not presently considered a threat to blue, fin or sei whales in the eastern North Pacific.

Blue whales were the first target of modern commercial whaling and their populations were severely depleted in all oceans of the world. The species was protected worldwide in 1966 by the IWC. An estimated 325,000-360,000 blue whales were killed in the Antarctic during the first half of the 20th century, nearly extirpating the Southern Hemisphere population. In the North Pacific, blue whales were hunted by both coastal, shore-based whalers and pelagic whaling fleets, taking an estimated 9500 animals. Almost half of these were killed off the west coast of North America (Sears and Calambokidis 2002).

There is clear evidence that whaling depleted the populations of blue whales off British Columbia. Shore-based stations operating in British Columbia from the early 1900’s through 1967 killed at least 650 blue whales, though the annual catch declined rapidly as the population was depleted (Figure 2). From 1948 to 1965, mean lengths of blue whales killed from British Columbia shore stations declined significantly along with pregnancy rates (Gregr et al. 2000).

Fin whale populations off the coast of British Columbia were reduced by whaling in parallel with blue whales, following the introduction of modern whaling. Local populations suffered further loss when the coastal fleet was upgraded in the 1950s (Figure 2). At least 7605 fin whales were taken by British Columbia coastal stations between 1908 and 1967 (Gregr et al. 2000). Fin whales were most heavily exploited through the 1950s and 1960s, when the annual catch from the North Pacific ranged from 1000 to 1500 animals. Until 1955, most whaling off the west coast of North America was off British Columbia, after which catches began to increase off California. Fin whales in the North Pacific were protected by the IWC in 1976 (Mizroch et al. 1984).

Although not a primary target for whalers until blue and fin whale populations were severely depleted, sei whales were heavily exploited during the last decades of commercial whaling. Following the depletion of blue and fin whales, over 110,000 sei whales were killed in the Antarctic between 1960 and 1970. In the North Pacific, catches peaked at over 25,000 animals per year in the late 1960s. The last year of sanctioned whaling for sei whales in the North Pacific was 1975. On the Pacific coast, at least 4002 sei whales were taken by coastal stations in British Columbia between 1908 and 1967, with the majority taken after 1955 (Gregr et al. 2000) . The total sei whale catch from the North Pacific was almost twice the fin whale catch, and close to 20 times the blue whale catch between 1925 and 1985 (IWC Database, J. Breiwick, pers. comm.).