Decreasing sea ice conditions in western Hudson Bay and an increase in abundance of harbour seals (Phoca vitulina) in the Churchill River

Harbour seals (Phoca vitulina) occur in the Arctic but little is known of their population abundance and natural history. In western Hudson Bay, they occur at lower numbers relative to ringed seals (Pusa hispida) and their distribution is largely unknown. However, a reduction in the duration of periods of ice cover in Hudson Bay may be shifting the habitat suitability of the region towards one that favours harbour seals. Harbour seal counts from a known haul-out site at the upstream extent of the Churchill River estuary, located in northern Manitoba, were examined in relation to sea ice conditions in western Hudson Bay. The Churchill River estuary haul-out site was observed directly or remotely (via GigaPan (TM) photos) during the open-water seasons in 1996, 1999, 2000, and 2005, and from 2014 to 2016. We documented an increase in abundance over the study period; the maximum number of harbour seals observed hauled out at one time was 142 in 2016, compared to a maximum of 32 observed during monitoring activities conducted between 1996 and 2005. In addition, newly born harbour seal pups were observed at the haul-out site during the latter study years, an occurrence not observed from 1996 to 2005. We suggest that an increase in the abundance of harbour seals in Hudson Bay and potentially the entire Arctic may be observed if climate change related reductions in the duration of ice cover continue.