Critical Killer Whale Habitat Identified

Researchers propose that two marine areas of British Columbia be legally designated as critical habitat for resident killer whales under Canada's Species at Risk Act (SARA). An analysis of over 5880 encounters since 1973 in which killer whales were individually identified finds that orcas congregate along migrations of their main prey, chinook and chum salmon.

For the threatened northern population, 905 km² of critical habitat centres on Johnston Strait, where 90 percent of northern resident whale observations have been recorded. For the endangered southern killer whale population, a region of 3390 km² encompassing Canadian portions of Juan de Fuca and Haro Straits appears critical.

Probably also important for the northern orcas are Caamano Sound and Fitz Hugh Sound, areas the whales frequent during early chinook migrations before heading to Johnston Strait. Since these sites are much less studied, too little is presently known to propose them as critical habitat.

The waters identified all lie along the routes taken by major chinook stocks headed for rivers such as the Fraser, Bella Coola and Dean. Characteristic of all the sites are geographic features that force salmon to become concentrated for the first time during their migration. The natural funnels have particularly strong tidal currents, steep shorelines and narrow ocean passages around islands which all contribute to making the salmon easier for whales to catch.

Most killer whales stay in these areas only for the summer chinook and fall chum salmon runs. Whale whereabouts during winter and early spring are not well documented, so there may be other important resident orca habitats yet to be discovered.

Reference

J.K.B. Ford. 2006. An Assessment of Critical Habitats of Resident Killer Whales in Waters off the Pacific Coast of Canada. Research Document - 2006/072. Fisheries and Oceans Canada, Canadian Science Advisory Secretariat. Ottawa, ON. Research Report

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