Population assessment of Pacific Harbour Seal (Phoca vitulina richardsi) in the Strait of Georgia

Abstract

Harbour Seals fulfil an important ecological role in the Strait of Georgia (SOG). They are a key prey species for Transient (also known as Bigg’s) Killer Whales and current information on abundance and distribution of Harbour Seals has been identified as an important component of Transient Killer Whale habitat. They are also a major predator of several commercially important fish species in the SOG, including salmon, herring and Hake. Fisheries and Oceans Canada (DFO) has been conducting standardized aerial surveys during the pupping season since the early 1970s to determine Harbour Seal abundance and distribution in Canadian Pacific waters. Harbour Seal populations in the SOG increased exponentially at a rate of about 11.5% during the 1970s and 1980s, and then stabilized in the mid-1990s. Abundance increased from ~3,600 in 1973 to ~39,000 during 1994–2008. Based on surveys flown in 2014, Harbour Seal abundance in the SOG is estimated to have remained stable at ~39,000 (95% CI 35,000–42,100). Although overall numbers are stable in the SOG, there is evidence of continuing redistribution among haulout sites. In addition to ongoing population monitoring, further analysis of changes in Harbour Seal distribution and behaviour are required to support Transient Killer Whale recovery, assess fishery interactions, and identify potential impacts of proposed development in the SOG.