Sustained exponential population growth of grey seals at Sable Island, Nova Scotia

Grey seal pup production on Sable Island, Nova Scotia, has been monitored since the early 1960s. We estimated pup production on Sable Island in 1997 using aerial photography with a correction for detection of pups on the imagery and a statistical model to account for the proportion of pups not born...

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Bibliographic Details
Published in:ICES journal of marine science 2003, Vol.60 (6), p.1265-1274
Main Authors: Bowen, W.D, McMillan, J, Mohn, R
Format: Article
Language:English
Subjects:
environmental
grey seal
Halichoerus grypus
Marine
population
pup production
variablility
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Summary:Grey seal pup production on Sable Island, Nova Scotia, has been monitored since the early 1960s. We estimated pup production on Sable Island in 1997 using aerial photography with a correction for detection of pups on the imagery and a statistical model to account for the proportion of pups not born at the time of the survey. A total of 20 863 pups were counted on the colour positives. When corrected for the proportion of pups seen on the imagery (0.96) and the proportion of pups born before the survey (east colony 0.94, west colony 0.66), estimated total pup production was 25 400 with approximate 95% confidence limits of 23 500 and 26 900. The 1997 estimate indicates that pup production in this population, now the largest grey seal colony in the world, has been increasing exponentially at an annual rate of 12.8% for four decades in the face of considerable environmental variability.
ISSN:1054-3139
1095-9289
DOI:10.1016/S1054-3139(03)00147-4