© 2005 International Council for the Exploration of the Sea
Estimation of harp seal (Pagophilus groenlandicus) pup production in the North Atlantic completed: results from surveys in the Greenland Sea in 2002
a Institute of Marine Research PO Box 6404, N-9294 Tromsø, Norway
b Science Branch, Department of Fisheries and Oceans, Northwest Atlantic Fisheries Centre PO Box 5667, St. John's, Newfoundland, Canada A1C 5X1
*Correspondence to T. Haug: tel: +47 776 09722; fax: +47 776 09701. e-mail: toreha{at}imr.no.
From 14 March to 6 April 2002 aerial surveys were carried out in the Greenland Sea pack ice (referred to as the "West Ice"), to assess the pup production of the Greenland Sea population of harp seals, Pagophilus groenlandicus. One fixed-wing twin-engined aircraft was used for reconnaissance flights and photographic strip transect surveys of the whelping patches once they had been located and identified. A helicopter assisted in the reconnaissance flights, and was used subsequently to fly visual strip transect surveys over the whelping patches. The helicopter was also used to collect data for estimating the distribution of births over time. Three harp seal breeding patches (A, B, and C) were located and surveyed either visually or photographically. Results from the staging flights suggest that the majority of harp seal females in the Greenland Sea whelped between 16 and 21 March. The calculated temporal distribution of births were used to correct the estimates obtained for Patch B. No correction was considered necessary for Patch A. No staging was performed in Patch C; the estimate obtained for this patch may, therefore, be slightly negatively biased. The total estimate of pup production, including the visual survey of Patch A, both visual and photographic surveys of Patch B, and photographic survey of Patch C, was 98 500 (s.e. = 16 800), giving a coefficient of variation of 17.9% for the survey. Adding the obtained Greenland Sea pup production estimate to recent estimates obtained using similar methods in the Northwest Atlantic (in 1999) and in the Barents Sea/White Sea (in 2002), it appears that the entire North Atlantic harp seal pup production, as determined at the turn of the century, is at least 1.4 million animals per year.
Keywords: abundance, aerial surveys, birth distribution, Greenland Sea, harp seal, pup production
Received 6 July 2004; accepted 23 July 2005.
1 Current address for P. J. Corkeron: Bioacoustics Research Program, Cornell Laboratory of Ornithology, 159 Sapsucker Woods Road, Ithaca, NY 14850, USA.