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Research Document - 2014/057

Estimating Pup Production of Northwest Atlantic Harp Seals, Pagophilus groenlandicus, in 2012

By G.B. Stenson, M.O. Hammill, J.W. Lawson, J-F. Gosselin


Photographic and visual aerial surveys were conducted off Newfoundland and in the southern Gulf of St. Lawrence to determine pup production of Northwest Atlantic harp seals in 2012. Repeated surveys of three whelping concentrations were carried out between 27 February and 16 March. Visual surveys in the southern Gulf resulted in pup production estimates ranging from 117,600 (SE=31,800) to 137,300 (SE=48,400) animals, after correcting estimates for pups born after the surveys were flown. Photographic estimates varied from a low of 71,300 (SE=9,000) from a survey flown on 4 March to 111,500 (SE=20,000) pups from a survey flown on 2 March. The 4 March estimate is considered to be negatively biased because a significant number of pups appeared to be outside of the survey area. Mortality of pups may also have occurred between the two surveys. Excluding the 4 March survey, estimated pup production in the southern Gulf was 115,500 (SE=15,000) animals. Multiple photographic surveys of seals that pupped on ice that was originally in the Strait of Belle Isle and at the Front resulted in estimates of 74,100 (SE=12,400) and 601,400 (SE=66,900) pups, respectively. Combining the number of pups found in all three areas resulted in an estimated total pup production of 790,000 (SE=69,700, CV=8.8 %). This estimate is approximately half of the estimated number of pups born in 2008, likely due to lower reproductive rates in 2012 compared to 2008. Only 15 % of the pups were born in the southern Gulf where years of poor ice conditions have been increasing in frequency over the past decade. Ice conditions observed during 2012, were similar to those observed in 1969, 2010, and 2011 and are among the worst on record. This continuing trend of poor ice conditions has serious implications for survival of harp seal pups and the longer-term persistence of breeding seals in the southern Gulf of St. Lawrence.

Key words: harp seal, Pagophilus groenlandicus, pup production, survey, abundance, birth distribution, Northwest Atlantic, ice conditions

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