Grey whale (Eschrichtius robustus) COSEWIC assessment and status report: chapter 6

Distribution

Global range

Grey whales are restricted to the northern hemisphere. Subfossil skeletal remains (Mead and Mitchell 1984), as well as historical accounts (Mead and Mitchell 1984; Lindquist 2000) document the existence of a now-extirpated population of grey whales in the North Atlantic. In the eastern North Atlantic, grey whales were present in the Baltic and North Seas and the English Channel (Mead and Mitchell 1984), as well as the waters around Iceland (Lindquist 2000). In the western North Atlantic, subfossil remains were found from southeastern Florida north to Long Island (Mead and Mitchell 1984; Reeves and Mitchell 1988). Atlantic grey whales may have visited Canadian waters, including the Scotian Shelf, Gulf of St. Lawrence, and Grand Banks, and even entered Hudson Bay (Reeves and Mitchell 1988). Grey whales appear to have been extirpated from the eastern Atlantic around 1730 (Bryant 1995; Lindquist 2000), and from the western Atlantic in the mid- to late 18th century (Mead and Mitchell 1984).

In the North Pacific, grey whale fossils date to at least 50 000 years before present (Barnes and McLeod 1984). North Pacific grey whales fall into two distinct populations: the eastern or California population winters in a series of shallow lagoons (primarily Laguna Guerrero Negro, Laguna Ojo de Liebre, Laguna San Ignacio, and Bahia Magdalena) along the west coast of Baja California, Mexico (Rice et al. 1981). Grey whales are also regularly observed in the Gulf of California and along the coast of the Mexican mainland in winter and spring (Tershy and Breese 1991; Silber et al. 1994; Sánchez-Pacheco et al. 2001). Between January and May, the animals leave the winter breeding grounds and head north along the west coast of North America, usually travelling within a few kilometres of shore (Braham 1984; Herzing and Mate 1984; Poole 1984a; Green et al. 1995). Most of the population passes through Unimak Pass in the Aleutian chain between May and June (Pike 1962) to feed in the shallow waters of the Bering, Chukchi and Beaufort seas. The primary summer feeding ground of the eastern population (Figure 2) extends from Cape Bathurst (Northwest Territories; Rugh and Fraker 1981) west to Mys Billingsa in the East Siberian Sea (Miller et al. 1985; Kochnev 1998) and includes all of the shallow waters of the Bering Sea south to Unimak Pass (Braham 1984). A small part of the eastern North Pacific population of grey whales, termed the summer-resident community, spends the summer feeding in temperate near-shore waters (Figure 3) from northern California to southeastern Alaska (Pike 1962; Patten and Samaras 1977; Flaherty 1983; Darling 1984; Mallonée 1991; Avery and Hawkinson 1992; Calambokidis et al. 1994).


Figure 2. Map of the North Pacific showing the distribution and migration route of the eastern North Pacific population of grey whales.

Figure 2. Map of the North Pacific showing the distribution and migration route of the eastern North Pacific population of grey whales.

 


Figure 3. Map of the eastern North Pacific showing the migration route and known feeding sites of grey whales off British Columbia, Canada.

Figure 3. Map of the eastern North Pacific showing the migration route and known feeding sites of grey whales off British Columbia, Canada.


Much less is known about the western Pacific, or Korean, population of grey whales. This population was greatly reduced by whaling and its current size is estimated at 100 individuals (Weller et al. 2002a). A feeding ground has recently been discovered off the coast of Sakhalin Island (Weller et al. 1999; Weller et al. 2002a). Western Pacific grey whales probably migrate along the coasts of Japan, Korea and China to breeding grounds off southern China (Wang 1984; Clapham et al. 1999). There appears to be no genetic exchange between the eastern and western North Pacific populations (LeDuc et al. 2002).

Canadian range

Only grey whales belonging to the eastern North Pacific population occur in Canadian waters. Virtually the entire population (approximately 18,000 animals in 2002) passes through the coastal waters of British Columbia in spring and fall on their migration between summer feeding grounds and winter breeding grounds (Fig. 3). Northbound migrants generally arrive in British Columbia waters west of Carmanah Point on Vancouver Island (Darling 1984; Gisborne, pers. comm.), then follow the island’s west coast north to Cape Scott (Darling 1984). The migration route north of Vancouver Island is poorly understood, but the majority of animals probably cross Queen Charlotte Sound north to Cape St. James and follow along the east and west coasts of the Queen Charlotte Islands (Pike 1962). The animals cross Dixon Entrance and leave Canadian waters. Many animals have been observed feeding inshore during the northbound migration (Pike 1962; Sund 1975; Darling 1984). The southbound migration follows much the same route, although the animals tend to travel further offshore and little feeding is observed (Pike 1962; Darling 1984).

Pike (1962) first noted that some grey whales did not complete the full migration to arctic feeding grounds, but spent the summer feeding in temperate waters off the British Columbia coast. Such summer-resident grey whales have since been reported from many other areas off the west coast of North America (Patten and Samaras 1977; Flaherty 1983; Mallonée1991; Averyand Hawkinson 1992; Calambokidis et al. 1994). Summer-resident grey whales have a high degree of site fidelity and tend to return to the same feeding sites year after year (Darling 1984; Calambokidis et al. 1994; Calambokidis et al. 2002). The presence of summer-resident grey whales along the entire west coast of Vancouver Island is well documented (Darling 1984). Summer-resident grey whales are also often seen along the north coast of Vancouver Island from Cape Scott to Cape Sutil, as well as along the British Columbia mainland from Shelter Bay to Cape Caution (Deecke 1996). Due to much lower observer effort, the occurrence and distribution of grey whales in the summer months on the north coast of British Columbia is poorly understood. In the Queen Charlotte Islands, grey whales are frequently seen feeding on herring spawn in Skidegate Inlet and the east coast of South Moresby Island between May and July (Nichol and Heise 1992; Ford et al. 1994). Reports of feeding grey whales in the summer months come from the west coasts of Calvert Island (Darling, per. comm.), as well as Dundas and Aristazabal Islands (Ellis, pers. comm.; Ford, pers. comm.), and known British Columbia summer-residents have been photographed in the McMullin Group, as well as Sitka Sound, southeastern Alaska (Deecke 1996; 2003; Calambokidis et al. 2002). Summer-resident grey whales have also been sighted in the inside waterways of British Columbia, primarily in Boundary Bay (Deecke 1996; Ford, pers. comm.), as well as occasionally in Haro and Georgia Straits (Calambokidis and Baird 1994; Malcolm 1999).

While the primary arctic feeding ground of the eastern North Pacific population lies mainly within the waters of Russia and the USA, it also includes the waters off the Northwest Territories and possibly western Nunavut. Grey whales have been observed feeding off Cape Bathurst (Rugh and Fraker 1981), and are listed as a species in Tuktut Nogait National Park (Alvo, pers. comm). The role of the Canadian Beaufort Sea as a summer feeding ground for grey whales is currently poorly understood. Further research appears warranted, especially since the importance of this area as a feeding ground may increase in the future if the carrying capacity of the western Beaufort, Chukchi and Bering Seas for grey whales is reached.

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