Research Document - 2012/155

Information in Support of the Identification of Critical Habitat for Transient Killer Whales (Orcinus orca) off the West Coast of Canada

By J.K.B. Ford, E.H. Stredulinsky, J.R. Towers, and G.M. Ellis

Abstract

Mammal-eating transient killer whales off Canada’s Pacific coast are listed as Threatened under the Species-at-Risk Act. A Recovery Strategy for transient killer whales was prepared by DFO in 2007, but insufficient information was available to identify critical habitat in that document. Here we present an assessment of the habitat use and requirements of West Coast Transient (WCT) killer whales in order to provide the basis for the identification of critical habitat for this population. For this assessment, we used an archive of photo-identifications of individual WCT whales collected during 3582 encounters between 1958 and 2011. Based on frequency of occurrence and distribution, we defined two putative subpopulations, a well-known inner coast subpopulation and an outer coast subpopulation that remains poorly known. The inner coast population was composed of 304 individuals identified during 2988 encounters between 1990 and 2011, and this dataset was used to analyse movement and habitat use patterns. The outer coast subpopulation comprised 217 individuals that were rarely encountered. These whales were found in deeper water, further from land, and closer to the continental shelf break than inner coast whales. WCT killer whales are highly mobile and range over the entire BC coast throughout the year. They forage for marine mammal prey in all marine habitats, primarily in close proximity to coastlines. We describe the biophysical functions, features, and attributes of this habitat, most of which involve feeding and adequate abundance and distribution of prey. Based on existing information, we suggest that a habitat area that includes Pacific coast marine waters up to 3 nautical miles (5.56 km) from shore is of sufficient extent to provide for the population and distribution objectives described in this population’s Recovery Strategy, at least for the inner coast subpopulation. This area encompasses the locations of over 90% of all individual identifications and predation events documented with the inner coast WCT subpopulation since 1990. It also includes 64% of identifications of the outer coast subpopulation. This area comprises 40,358 square km, or about 8.9% of Canadian waters off the west coast. Examples of activities likely to destroy critical habitat are described.

Complete document (PDF, 2,003 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.