Science Advisory Report 2017/011
Identification of Habitats of Special Importance to Resident Killer Whales (Orcinus orca) off the West Coast of Canada
- Southern Resident (SRKW) and Northern Resident Killer Whales (NRKW) were listed as Endangered and Threatened, respectively, in 2003 under the Species at Risk Act (SARA) and a Recovery Strategy for these populations was completed in 2011. The goal of the 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”.
- The Recovery Strategy included identification of an area of critical habitat for each of the populations. The main function of these habitats is for foraging and feeding on the whales’ primary prey, Chinook Salmon, during summer and fall.
- The Recovery Strategy recognized that critical habitat for these populations was only partially identified, and provided a schedule of studies to identify additional critical habitat areas for Resident Killer Whales.
- Field studies conducted since the Recovery Strategy was completed have yielded new information sufficient to identify two habitats of special importance that may be necessary for the survival or recovery of SRKW and NRKW populations. These areas are located off southwestern Vancouver Island (an extension of existing SRKW critical habitat) and in western Dixon Entrance. ‘Bounding boxes’ are provided here that encompass these areas of special importance.
- Vessel surveys and passive acoustic monitoring (PAM) of whale vocalizations indicate that the habitat identified as being of special importance off southwestern Vancouver Island is used throughout the year by both SRKWs and NRKWs. Resident Killer Whales were detected acoustically in the area on one out of every three days, on average, during 2009–2011. The area is important for SRKWs during summer, when groups of whales make foraging excursions to the west of the currently designated critical habitat, and in winter when whales are mostly absent from the identified critical habitat, but frequently use this area. NRKWs also frequent this area during spring, when they are mostly absent from their designated critical habitat off northeastern Vancouver Island.
- Chinook Salmon, which occur seasonally in relatively high densities off southwestern Vancouver Island, is the predominant prey species consumed in the area during summer. Predation has also been documented on other salmonid species and sablefish.
- Vessel surveys and PAM demonstrate that waters of western Dixon Entrance, north of Graham Island in Haida Gwaii, provide a habitat of special importance for NRKWs throughout the year. As with southwestern Vancouver Island, this area is used most extensively by NRKWs when they are mostly absent from their legally identified critical habitat off northeastern Vancouver Island during late winter and spring. The area is also used by NRKW pods that rarely utilize the designated critical habitat at any time of the year.
- Chinook Salmon is the predominant prey of NRKWs in this habitat area during summer and probably other times of year. Western Dixon Entrance has long been known as a productive commercial troll fishing ground for Chinook Salmon as well as an important area for recreational Chinook fishing.
- The features and attributes of these important habitat areas include sufficient quantity and quality of critical prey species, particularly Chinook Salmon, water quality of a sufficient level so as not to result in loss of function, and an acoustic environment that does not interfere with communication or echolocation or cause disturbance and avoidance responses.
- Activities that are likely to result in the loss of functions of these important habitat areas include those that would result in reduced prey availability, acoustic disturbance, environmental contamination, and physical disturbance.
- Although the habitats of special importance identified in this report, together with previously legally identified critical habitat, are necessary for the survival or recovery of RKWs, it is unclear whether these habitats are sufficient to meet the goals of the Recovery Strategy related to Resident Killer Whales, particularly for NRKW. Further studies are needed to identify additional areas that may be critical at certain times of year or for particular groups within the populations of Resident Killer Whale.
This Science Advisory Report is from the February 23-26, 2016 National Marine Mammal Peer Review Committee (NMMPRC): Habitat Requirements for Killer Whale (Northeast Pacific northern and southern resident populations), Fin Whale (Pacific), and Blue Whale (Atlantic). Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.
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