Between 2007 and 2015, we recorded three cases of asphyxiation of grey seals Halichoerus grypus caused by a fish lodged in the respiratory tract. In all cases, the fish involved was a common sole Solea solea, which had found its way to the trachea of the unfortunate seal, as such completely blocking it. That this fish species was involved, is not surprising: it has a very agile body, with a spectacular ability to bend longitudinally into a circular shape, as well as laterally into the form of a cigar - the way it was found in the gluttonous grey seals. The common sole currently occurs abundantly in coastal waters of the southern North Sea, and it constitutes an important part of the diet of grey seals in this area. Asphyxiation due to fish has been described in odontocetes, including in harbour porpoise Phocoena phocoena, bottlenose dolphin Tursiops truncatus, and very recently in long-finned pilot whale Globicephala melas. To our knowledge however, this cause of death has not been described before in grey seals. Furthermore, the significance of this cause of mortality in a single population has not been documented, with in particular aspects of prey abundance, seal behaviour and the limited number of stranded adult grey seals that are being investigated to be considered. Keywords: grey seal; Halichoerus grypus; common sole; Solea solea; asphyxiation; respiratory tract

Abstract of an Oral Presentation or a Poster