Harbour porpoises are protected as a species of Annex II of the Habitats Directive. The harbour porpoises recorded up to now in Area I are presumably in winter individuals of the severely endangered eastern harbour porpoise population of the central Baltic Sea. This subpopulation totalling only about 500 individuals uses the area as a migration and wintering habitat. Mother-calf pairs have also been sighted here. These sightings are of particular importance as there are very few of these highly endangered small whales in the central Baltic Sea. Especially in cold winters, the area is important for the survival of individuals immigrating from Baltic Sea regions covered by ice. Existing obligations for Germany within the framework of the Agreement on the Conservation of Harbour Porpoises (within ASCOBANS) and the Habitats Directive have laid down the binding aim of restoring populations of this kind that are endangered in German waters and of safeguarding important habitats.