Research Document - 2005/068

Reduced rate of increase in grey seals at Sable Island: an estimate of 2004 pup production

By Bowen, W.D., J.I. McMillan, and W. Blanchard

Abstract

Grey seal pup production on Sable Island, Nova Scotia, has been increasing exponentially since the early 1960s and by 1997 the Sable Island colony was the largest of this species worldwide. Using the same method as in previous years (i.e., an aerial photographic survey), we estimated pup production in January 2004 to determine if this exponential rate of increase in pup production had continued. A total of 33 268 pups was counted on the colour positives. When corrected for the proportion pups seen on the imagery (1.106 for the 12th; 1.527 on the 13th), proportion of pups that died prior to the survey (0.029) and the proportion of pups born before the survey (east colony 0.966, west colony 0.962), estimated total pup production was 41 500 with SE = 4 380. The 2004 estimate indicates that pup production on Sable Island has continued to increase, but at a reduced rate (r = 0.07 compared to previous 0.128), for almost five decades.

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