Abundance of grey seals in Icelandic waters, based on trends of pup-counts from aerial surveys

Abstract

Grey seals (Halichoerus grypus Fabricius, 1791) are distributed all around the Icelandic coast. The majority of the population breeds on the west- and northwest shores, with a second high density in the breeding distribution on the southeast coast of Iceland. During the last 5 decades the Icelandic grey seals have dispersed from the west- to the northwest-, the north- and the northeast-coast. The breeding period occurs from the middle of September to early November, with a maximum in mid October. The time of peak pupping shows some variation, beginning earlier along the west coast and later in the north and southeast. Seven aerial surveys to estimate pup production in Iceland were flown during October to November during the period from 1980 to 2004. Pup counts of the Icelandic grey seal, at all breeding sites combined, have been decreasing annually by about 3% (±1% s.e.), during the period 1982-2002. During the period 1990-2002, this downward trend doubled to about 6% annually. The abundance of the grey seal around Iceland in the year 2002 was estimated to be 4,100 to 5,900 animals. This is higher than estimates of around 2,000 animals during the 1960s, but much less than the estimated population of 8,000 to 11,500 in 1982.