Skagerrak, Kattegat, Baltic Proper, Gulf of Bothnia

Seal abundance

The study is part of the National Environmental Monitoring Programme and focuses on the population development of ringed seals and harbour seals in the Kattegat-Skagerrak. Both species are top-predators in respective ecosystems, and thus vulnerable for bioaccumulating substances. Ringed seal females have suffered from reproductive disturbances since the 1960s and 30 to 40% were still sterile at the beginning of the 1990s. The reproductive capacity of the population is the main reason for the hampered development of the stock. Increasing prevalence of bone lesions (paradontitis and exostosis) since the 1960s has been documented in the Baltic and west coast populations of harbour seals. Also these changes are most probably caused by exposure to environmental pollutants. Trends in developments of the populations are used for detecting changes in the ecosystem. The reproductive output is measured in all regions of harbour seal distribution.

Harkonen, T (1997) BIOMAD 6.4. Seal Population Data from the West Coast Area 1989-1995,

Swedish Meteorological and Hydrological Institute
Folkborgsvagen 1
Norrkoping

SE-601 76
Sweden