Ringed Seal and Harbour Population Data (1989-)

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.

本研究属于国家环境监测计划的一部分，聚焦于卡特加特-斯卡格拉克海域环斑海豹和港海豹的种群发展。两种物种在其各自的生态系统中均为顶级捕食者，因此易于生物累积有害物质。自20世纪60年代以来，环斑海豹雌性便遭受了繁殖干扰之苦，至20世纪90年代初，仍有30%至40%的个体处于不育状态。种群繁殖能力成为阻碍种群发展的主要因素。自20世纪60年代起，波罗的海和西海岸港海豹种群中骨病变（牙周炎和骨疣）的发病率逐渐上升，这些变化很可能是由暴露于环境污染物所引起。通过对种群发展趋势的监测，用以探测生态系统中的变化。港海豹的繁殖产出在分布的所有区域均进行了测量。