Spatiotemporal accumulation of fatal pharyngeal entrapment of flatfish in harbour porpoises ( Phocoena phocoena ) in the German North Sea

PeerJ

article

Stephanie Gross¹  Marco Roller¹  Holger Haslob²  Miguel Grilo¹  Jan Lakemeyer¹  Anja Reckendorf¹  Peter Wohlsein⁴  Ursula Siebert¹ 

[1] Institute for Terrestrial and Aquatic Wildlife Research ,(ITAW), University of Veterinary Medicine Hannover, Foundation;Thünen-Institute of Sea Fisheries;CIISA—Centre for Interdisciplinary Research in Animal Health, University of Lisbon;Department of Pathology, University of Veterinary Medicine Hannover, Foundation

关键词: Odontocetes;    Common sole;    Asphyxiation;    Bolus death;    Post-mortem examination;   

DOI  :  10.7717/peerj.10160

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

The evolution of a permanent separation of the upper respiratory and digestive tract is one of the adaptions cetaceans evolved for their aquatic life. Generally, it prevents odontocetes from choking on either saltwater or foreign bodies during ingestion under water. Nevertheless, several sporadic single case reports from different parts of the world show that this separation can be reversed especially by overly large items of prey. This incident can have a fatal outcome for the odontocetes. The German federal state of Schleswig-Holstein has a year-round, permanent and systematic stranding network that retrieves stranded marine mammals from its shorelines and constantly enables post-mortem examinations. In 2016, with nine affected animals, a high incidence of fatal pharyngeal entrapment of flatfish in harbour porpoises (Phocoena phocoena) occurred during spring and early summer on the German North Sea island of Sylt. All flatfish were identified as common sole (Solea solea). A retrospective post-mortem data analysis over a 30-year period from the North and Baltic Sea revealed similar yearly and seasonally case accumulations on the same island in the 1990s as well as several single case events over the whole timespan. All cases except one were caused by flatfish. When flatfish speciation was performed, only common sole was identified. From 1990 to 2019, of all examined harbour porpoises, 0.3% (2/713) from the Baltic Sea and 5.5% (45/820) from the North Sea died due to fish entrapped in the pharynx. On the North Sea coast, the occurrence of fatal obstruction shows high yearly variations from 0 to 33.3%. Years that stand out are especially 1990 to 1992, 1995, as well as 2016. The majority of all cases generally occurred between April and July, indicating also a seasonality of cases. This study evaluates the occurrence of fatal pharyngeal entrapment of fish in two geographically separated harbour porpoise populations. Additionally, common sole is clearly identified as a potentially risky item of prey for these small odontocetes.

【 授权许可】

CC BY