Is there evidence of increased pup production in northwest Atlantic harp seals, Pagophilus groenlandicus ?

Abstract

Photographic and visual surveys of the whelping (pupping) concentrations off eastern Newfoundland (“Front”) and in the Gulf of St Lawrence (“Gulf”) were conducted during March 1994 to determine whether pup production of Northwest Atlantic harp seals has increased since the decline in hunting during the mid-1980s and early 1990s. Photographic counts were corrected for misidentified pups by comparing multiple readings of photographs made by two or more readers. Survey estimates were also corrected for pups absent from the ice at the time of the survey using the occurrence of distinct age-related developmental stages. Multiple estimates were available for three of the ten whelping concentrations. Pup production was estimated to be 446 700 (s.e.=57 200) at the Front, 57 600 (s.e.=13 700) in the northern Gulf and 198 600 (s.e.=24 200) in the southern Gulf (Magdalen Island) for a total of 702 900 (s.e.=63 600). This result is greater than estimates obtained in the late 1970s and early 1980s using mark-recapture techniques. The 1994 estimate can be compared directly with the 1990 estimate of pup production (578 000, s.e.=38 800) which was obtained using similar aerial survey methods. The null hypothesis of no increase in pup production (one-tail t-test) was rejected (p=0.03) indicating that pup production has increased.