The breeding and distribution of the grey seal ( Halichoerus grypus Fab.) in the Baltic Sea, with observations on other seals of the area

Abstract

The grey seal (Halichoerus grypus Fab.) is considered to be one of the rarest species of the seals. The area of greatest abundance is centred around the coasts of the British Isles where the species has been established for a considerable period. The Grey Seals Acts of 1914 and 1932 gave protection to the species in British waters during the breeding months of September to December. But this seal also occurs in other countries in the North Atlantic, notably in Eastern Canada, often on ice (figures 12, 13, plate 4), Iceland, the Faroes, Norway, the Kola peninsular and the Baltic Sea. The total population is estimated (Smith 1966) to be ca. 52 500. Since the last deglaciation considerable changes have occurred in the Baltic region, but at the present time in this tideless sea - which embraces the Gulfs of Bothnia, Finland and Riga, and in waters of a salinity as low as per thousand, of an area of 400000 km$^{2}$- the grey seal breeds in March on ice, as does the ringed seal in the same month and also on ice, though the common seal breeds in June on sandbanks or rocks. Within the area is a valuable and productive fishery and an inevitable conflict has for long existed between man and the seals, both predators of economically valuable fish, e.g. herring, cod, eel, salmon and other species, leading to the imposition of bounty payments for seals killed. Over the years very large numbers of grey and ringed seals have been killed, chiefly by fishermen in Sweden and Finland, to obtain bounties from the authorities. Unlike the planned culling undertaken in some British colonies, the Baltic killings have been made at random and little is known of its effect upon the survival of the species. In the Baltic it is not possible to undertake counts of seals owing to the scattered nature of their breeding and the unpredictability of the winter ice coverage.