A genetic comparison of West Greenland and Baffin Island (Canada) walruses: Management implications

Abstract

Until recently Atlantic walruses (Odobenus rosmarus rosmarus) have been subject to relatively intense exploitation in West Greenland. Animals in this stock have also been hunted in Nunavut/Canada. However, the demographic identity of these animals and their connection with walruses in neighbouring areas is poorly resolved, hampering the determination of sustainable harvest levels. It has been suggested that walruses in West Greenland are genetically linked with walruses at SE Baffin Island (Canada) where they are also hunted for subsistence purposes. To determine the relationship(s) between walruses in these areas we conducted a genetic analysis including recent samples from West Greenland, Southeast Baffin Island in western Davis Strait, Hudson Strait in Canada and Northwest Greenland in northern Baffin Bay. Seventeen microsatellite markers were applied to all samples. Walruses in West Greenland and at Southeast Baffin Island did not differ from each other and therefore may be regarded as belonging to the same stock. However, walruses in these two areas differed genetically from both Northwest Greenland and Hudson Strait walruses. These findings support (1) that there are subunits within the range of walruses in the Hudson Strait-Davis Strait-Baffin Bay region and (2) that walruses along E Baffin Island and W Greenland constitute a common population that receive some influx from Hudson Strait. Thus, sustainable catch levels in Southeast Baffin Island (Nunavut) and in West Greenland must be set in light of the finding that they belong to the same stock, which is exploited in these two areas. This requires Canadian-Greenlandic co-management of the W Greenland-SE Baffin Island walrus stock.

Estimates of Minimum Population Size for Walrus near Southeast Baffin Island, Nunavut

“…3) in the season when maximum numbers were expected to occur based on IQ. In 2007, major haulouts were also examined at surface level during a boat-based research (Dietz et al 2014). …”

“…2) included the main area of occupancy of walrus tagged in West Greenland and in the SE Baffin study area in 2007 (Fig. 4 of Dietz et al 2014). It also included the 37 presumed active haulout sites illustrated by Born et al (1995: Figs.…”

“…4). In 2007, as part of tagging studies (Dietz et al 2014) several of the known SE Baffin haulouts were visited by boat. Surface level estimates were made from a vantage point on land above the haulout, and from boats, sometimes below the lowest walrus on shore according to the stage of the tide.…”

“…1), two of which are shared with Greenland (Born et al 1995, NAMMCO 2006, Stewart 2008, Andersen et al 2009, Dietz et al 2014). The Hudson Bay-Davis Strait (HB-DS) stock, part of the central-Arctic population of walrus in Canada (Shafer et al 2014) ranges from West Greenland to eastern Baffin Island and into Hudson Strait, although it is thought the occupancy range in this region has diminished in modern history (COSEWIC 2006).…”

“…The survey area concentrated on SE Baffin as the most likely area where walrus arriving from Greenland would be hunted, an assumption subsequently borne out by tracking data (Dietz et al 2014). …”