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Recovery Strategy for the Northern and Southern Resident Killer Whale

Executive Summary

Two distinct populations of killer whales (Orcinus orca), known as the northern and southern residents, occupy the waters off the west coast of British Columbia.  In 2001, COSEWIC designated southern resident killer whales as ‘endangered’, and northern resident killer whales as ‘threatened’.  Both populations are listed in Schedule 1 of the Species at Risk Act (SARA).  These two populations are acoustically, genetically and culturally distinct.

Resident killer whale populations in British Columbia are presently considered to be at risk because of their small population size, low reproductive rate, and the existence of a variety of anthropogenic threats that have the potential to prevent recovery or to cause further declines. Principal among these anthropogenic threats are environmental contamination, reductions in the availability or quality of prey, and both physical and acoustic disturbance.  Even under the most optimistic scenario (human activities do not increase mortality or decrease reproduction), the species’ low intrinsic growth rate means that the time frame for recovery will be more than one generation (25 years). 

The southern resident killer whale population experienced declines of 3% per year between 1995 and 2001, and has increased since then to 85 members in 2003 [1].  During the summer and fall, southern residents are primarily found in the trans-boundary waters of Haro Strait, Boundary Pass, the eastern portion of the Strait of Juan de Fuca, and southern portions of the Strait of Georgia.  This area is designated as ‘critical habitat’ based on consistent and prolonged seasonal occupancy.  Some members of the population typically remain in the same general area in winter and spring, but others appear to range over much greater distances, and have been reported as far south as Monterey Bay, California, and as far north as Haida Gwaii (the Queen Charlotte Islands).  Winter and spring critical habitat has not been identified for the latter group.  During the summer and fall, the principal prey of southern residents appears to be chinook and chum salmon (Oncorhynchus tshawytscha and O. keta); little is known of their diet in the winter and spring.   The lack of information about winter diet and distribution of the southern residents is a major knowledge gap that impedes our understanding of the principal threats facing the population.

The northern resident killer whale population experienced a decline of 7% between 1997 and 2003, and similar to southern residents, has since increased to 205 members in 2003.  The population appears to spend the majority of its time from Campbell River and Alberni Inlet northwest to Dixon Entrance, but has been sighted as far south as Grays Harbor, Washington, and as far north as Glacier Bay, Alaska (C.M. Gabriele, personal communication).  A portion of the population is regularly found in Johnstone Strait and southeastern portions of Queen Charlotte Strait (and adjoining channels) during the summer and fall, and this area is identified as critical habitat based on this consistent seasonal occupancy.  Other areas are likely very important to northern residents during this time but they have yet to be clearly identified.  Similarly, areas that may constitute critical habitat during the winter and spring are not yet known.  Northern residents also appear to target chinook and chum salmon during the summer and fall.  However, like southern residents, very little is known of their winter distribution and diet, and this knowledge gap must be addressed to fully understand the principal threats affecting the population.

The goal of the resident killer whale recovery strategy is to:

Ensure the long-term viability of resident killer whale populations by achieving and maintaining demographic conditions that preserve their reproductive potential, genetic variation, and cultural continuity [2].

In order to achieve this goal, four principal objectives have been identified. These include:

Objective 1: Ensure that resident killer whales have an adequate and accessible food supply to allow recovery.

Objective 2: Ensure that chemical and biological pollutants do not prevent the recovery of resident killer whale populations.

Objective 3: Ensure that disturbance from human activities does not prevent the recovery of resident killer whales.

Objective 4: Protect critical habitat for resident killer whales and identify additional areas for critical habitat designation and protection.

Numerous broad strategies are outlined herein to achieve these objectives.  However, significant gaps in knowledge about killer whales remain and numerous actions have been identified to address these knowledge gaps and to identify further directions for recovery. Six recovery implementation groups (RIGs) are recommended to address the threats and issues of knowledge gaps regarding 1) resident killer whale population dynamics and demographics, 2) reduced prey availability, 3) environmental contaminants, 4) physical disturbance, 5) acoustic disturbance, and 6) critical habitat.  These RIGs will develop an appropriate action plan within two years of the acceptance of the recovery strategy by the competent minister.

[1]  Note that there are also small discrepancies in the southern resident counts in the literature due to different methods of recording when whales are considered to enter or leave the population. For example Krahn et al. (2004) report 83 southern residents in 2003.

[2] Culture refers to a body of information and behavioural traits that are transmittedwithin and between generations by social learning