Pup production of harp seals in the Northwest Atlantic in 2017 during a time of ecosystem change

Abstract

Photographic and visual aerial surveys were conducted off Newfoundland and Labrador (”the Front”), and in the Gulf of St. Lawrence (“Gulf”) in March 2017 to estimate pup production of Northwest Atlantic harp seals (Pagophilus groenlandicus). Traditionally, harp seals pup (whelp) in three general areas; the southern Gulf of St. Lawrence, the northern Gulf of St. Lawrence, and off the east coast of Newfoundland and Labrador. After extensive reconnaissance, four whelping areas were identified: one in each of the southern and northern Gulf, and two at the Front. We estimated a total pup production in 2017 of 746,500 (SE=89,900, CV=12%), the lowest since 1994. Most (96%) pups were born at the Front (714,600 pups, SE=89,700). Very few pups were born in the southern Gulf (18,300, SE=1,500) and no whelping concentrations were observed prior to March 5, approximately 1 week later than previously observed. This is far lower than the 2012 survey estimate of 115,500 (SE=15,100) for the same area. Pup production in the northern Gulf was also lower than in previous years, at 13,600 (SE=3,000). The timing of births in the southern Gulf was much later than normal in 2017, and unusually early pupping at the Front suggests that some females from the Gulf herd may have moved to the Front to whelp due to a lack of ice suitable for pupping (i.e., thin first year) in the Gulf. Harp seals whelp in large concentrations. While one large whelping concentration formed at the Front, approximately 15% of the pupping at the Front occurred in small, dispersed groups which formed later than observed in previous years. Given the unusual ice conditions, distribution of whelping seals, and timing of pupping, assessing the results of the 2017 surveys relative to other estimates of pup production in the Northwest Atlantic is challenging and indicates the ongoing difficulties of assessing a population that is being impacted by climate change.