[en] The North Sea represents a major ecosystem for the harbour porpoise (Phocoena phocoena) and the harbour seal (Phoca vitulina). The grey seal (Halichoerus grypus) occurs more occasionally in the southern part of the North Sea. Their population over this last decade has experienced major fluctuations likely linked to prey availability and seal epizootics. Despite being banned more than 30 years ago, levels of polychlorinated biphenyls (PCBs) in marine mammals are still of concern due to historical contamination of the North Sea.
Politique Scientifique Fédérale (Belgique) = Belgian Federal Science Policy ; Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS