Aerial Survey for Walrus in the Canadian North
The walrus family contains only one extant species, which is divided into two subspecies: the North Pacific walrus (Odobenus rosmarus divergens) and the North Atlantic walrus (Odobenus rosmaru rosmarus) (Riedman 1990). Once widely distributed in Canada, North Atlantic walruses were common south of the Gulf of St. Lawrence and Sable Island but were extirpated from these areas by the late 1700s.
Walruses are harvested for subsistence in Canada. They were assessed by the Committee on Species of Endangered Wildlife in Canada (COSEWIC) as a species of ‘‘Special Concern’’ in 2006 and are also listed under Appendix III of the Convention on International Trade in Endangered Species (CITES), which means that a permit from the Canadian CITES authorities is required to export walrus parts from Canada.
In Canada, Atlantic walruses can be divided into two populations based on genetic analysis, a High-Arctic population and a central Arctic population and these are further divided into 7 stocks for management purposes. A joint aerial survey was completed by the Quebec and Central & Arctic Regions in 2014 to determine walrus abundance in the Hudson Strait and northwestern Hudson Bay, which belong to what is known as the Hudson Bay-Davis Strait stock, as well as to determine walrus abundance in the south and east Hudson Bay. In spring 2014, community consultations were completed to obtain information on where walrus were known to appear and when would be the optimum survey period. From these consultations, September appeared to be the best time to fly the surveys. At that time, the day is still relatively long, and weather tends to be better than later in the fall. With support from the Polar Continental shelf Project, two de Havilland Twin Otters were used for the survey.
The total count for walrus belonging to the Hudson Bay-Davis Strait stock was 2144 animals. The total count for the south and east Hudson Bay stock was only 58 animals. Adjusting the count data for the proportion of the population hauled out at any one time (about 30% based on previous studies), the survey yielded an abundance estimate of about 7100 animals in the Hudson Bay-Davis Strait stock and about 200 animals in the south and east Hudson Bay stock. The counts from the south and east Hudson Bay stock appear to be low, but this only represents the first survey of this group. Clearly, additional work in this area is required.