Grey whale (Eschrichtius robustus) COSEWIC assessment and status report: chapter 7
Habitat
Habitat requirements
As a migratory mammal, grey whales require different habitats for foraging and for reproduction. The winter habitat of grey whale primarily comprises subtropical lagoons along the west coast of Baja California, Mexico. These calving lagoons are characterized by shallow (generally less than 4 m) water depths and have sandy or muddy bottom covered in places by eelgrass beds and mangrove swamps (Rice et al. 1981). The breeding lagoons have winter water temperatures between 15 and 20°C and are hypersaline due to evaporation (Gardner and Chávez-Rosales 2000). Total area of the four breeding lagoons is 2241 km2 (Laguna Ojo de Liebre and Guerrero Negro 366 km2; Bahia Magdalena 1700 km2; and Laguna San Ignacio 175 km2).
On arctic feeding grounds, grey whales are almost exclusively benthic feeders and are restricted to shallow (generally < 60 m) soft bottom habitats (Moore and Ljungblad 1984; Moore and DeMaster 1997; Moore et al. 2000). In the Bering Sea, grey whales are seen from 0.5 to 166 km from shore and tend to avoid areas of heavy ice (Clarke et al. 1989). Grey whales are also observed to enter shallow coastal lagoons to feed (Gill and Hall 1983).
In areas where they feed on amphipods (mainly Ampelisca sp., Atylus sp.) and ghost shrimp (Calianassa californiensis), summer-resident grey whales off British Columbia similarly prefer shallow nearshore habitats with mud or sand bottom. Feeding on ghost shrimp usually occurs in sheltered bays and inlets with muddy bottom and water depths below 3 m, whereas amphipods are found in sandy bays on the exposed outer coast in water depths of less than 35 m (Oliver et al. 1984; Weitkamp et al. 1992; Darling et al. 1998; Dunham and Duffus 2001; 2002). In addition, summer-resident grey whales are frequently seen over rock and boulder substrates in water of less than 30 m depth, and in kelp beds where they primarily feed on mysid shrimps or crab larvae (Wellington and Anderson 1978; Nerini 1984; Deecke 1996; Darling et al. 1998; Dunham and Duffus 2001; 2002). Eelgrass beds are the primary habitat where grey whales feed on the eggs and larvae of herring (Ford et al. 1994; Darling et al. 1998). It therefore appears that summer-resident grey whales feeding in temperate waters probably use almost all of the near-shore habitats along the outer coast of British Columbia (Darling et al. 1998) and also some sheltered bays in the inside waterways.
Trends
As a primarily coastal species, grey whales are threatened to some degree by increased human use of coastal marine ecosystems (Reeves and Mitchell 1988). Habitat deterioration is a concern for grey whales (see section ‘Limiting factors and threats’), and oil exploration is currently the main threat to grey whale habitat along the west coast of North America.
Protection/ownership
Since grey whales are restricted to shallow near-shore waters, virtually all grey whale habitat along the west coast of North America lies within the exclusive economic zones (200 nm limits) of Mexico, the USA, and Canada.
In Mexico, three of the four major breeding lagoons for grey whales are protected. Laguna Guerrero Negro and Laguna Ojo de Liebre are part of the Reserva de la Biosfera “El Vizcaino” (El Vizcaino Biosphere Reserve). Whale-watching is regulated in the reserve by a permit system and confined to the entrance to the lagoons (Reeves and Mitchell 1988). In 1979, the Mexican government declared Laguna San Ignacio a grey whale refuge and restricted commercial traffic to the lower part of the lagoon (thus protecting the main nursing and calving areas) between December and March (Reeves and Mitchell 1988). No protective measures are currently in place in Bahia Magdalena.
Grey whale habitat is protected in the US as part of the Marine Protected Areas Program. Parts of the migratorycorridor, as well as parts of the arctic and temperate feeding grounds lie within Marine Sanctuaries (Channel Islands, Monterey Bay, Gulf of the Farallones, Olympic Coast), marine components of US National Parks (Channel Islands, Redwood, Olympic, Bering Land Bridge) and a number of National Wildlife Refuges. All these prohibit or restrict some types of activities within their boundaries (US Dept. of Commerce 2000).
Jurisdiction over Canada’s exclusive economic zone lies with the federal government. There are currently few marine protected areas in Canadian waters. Pacific Rim National Park recently extended protection to adjacent waters out to the 20 m depth contour, thus gaining the ability to limit some commercial activity in a portion of the migratory corridor and feeding habitat for summer-resident grey whales. A similar marine component is planned for South Moresby/Gwaii Haanas National Park Reserve. Both national parks and to a lesser extent Tuktut Nogait National Park along with several provincial parks protect lands adjacent to grey whale habitat and thus restrict development of the shoreline. In 1998, Race Rocks became Canada’s first pilot marine protected area, and this general area is occasionally used by grey whales (Malcolm 1999).
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