Science Advisory Report 2009/039
Recovery Potential Assessment for West Coast Transient Killer Whales
Summary
- Mammal-eating ‘transient’ killer whales off Canada’s Pacific coast are listed as Threatened under the Species-at-Risk Act.
- This Recovery Potential Assessment for West Coast Transient (WCT) killer whales is intended to provide a scientific basis for recovery planning and is based on an archive of 219 individually photo-identified WCT whales collected from 1479 sightings between 1974 and 2006.
- These analyses indicate that the WCT population grew rapidly from the mid-1970s to mid-1990s as a result of a combination of high birth rate, survival, as well as greater immigration of animals into the nearshore study area. The rapid growth of the WCT population in the mid-1970s to mid-1990s coincided with a dramatic increase in the abundance of the whales’ primary prey, harbour seals, in nearshore waters. Population growth began slowing in the mid-1990s and has continued to slow in recent years.
- The recent slowing of WCT population growth suggests a carrying capacity of 250 to 300 whales. The Potential Biological Removal (PBR) is estimated at only 1.60 animals/year implying that the population would decline if human-induced mortality exceeds this rate.
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