Grey seal (Halichoerus Grypus) pup production at the Inishkea Island Group, co. mayo, and Blasket Islands, co. kerry

Abstract

The grey seal breeding assemblies on the Inishkea Island Group and Blasket Islands in western Ireland were studied in 1995 and 1996. A census of pup production in each area provided data on the timing of breeding and site selection at these island groups in addition to birth and mortality parameters. An estimated 154 pups were born at the Inishkea Group in 1995 and 155 pups at the Blasket Islands in 1996-97. These figures correspond to minimum all-age population estimates of 539-693 and 543-697 animals, respectively. These minimum estimates are similar to those derived in previous work at these islands, suggesting little change in the breeding population size at these colonies since 1983. Observed mortality was approximately 7.8% at the Inishkea Group and 2.6% at the Blasket Islands, though the true mortality may have been higher. Changes in breeding site use since 1980-83 were observed at the Inishkea Group in 1995. These are thought to be a result of past human interference. More effective coverage of the breeding season and long-term monitoring of these sites would contribute more accurate estimates and facilitate the determination of population trends. ́ ROYAL IRISH ACADEMY.