ICES CM 2010/F:04 Not to be cited without prior reference to the author Relationship between biological, pathological and toxicological parameters and the cause of death in harbour porpoises (Phocoena phocoena) stranded on the coast of Belgium and northern France Jauniaux T. 1, 2 , Das K. 3 , Haelters J. 2 , Jacques T. 2 , Kiszka J. 4 , Pezeril S. 5 , Stekké V. 1 , Weijs L. 6 and Coignoul F. 1 (1) Department of Veterinary Pathology, University of Liege, Sart Tilman B.43, 4000 Liege, Belgium tel.: +3243664074, fax.: +3243664565, e-mail: t.jauniaux@ulg.ac.be (2) Royal Belgium Institute of Natural Sciences, Management Unit of the North Sea Mathematical Models, Gulledelle 100, 1200 Brussels, Belgium tel.: +3227732113, fax: +3227732114; e-mail: T.Jauniaux@mumm.ac.be (3) Laboratory for Oceanology-MARE Center, University of Liège B6C, 4000 Liège, Belgium (4) University of La Rochelle LIENSS (Littoral, Environnement et Sociétés) UMR 6250 CNRS-Université de La Rochelle. 17071 La Rochelle, France and Direction de l'Environnement et du Développement Durable, Collectivité Départementale de Mayotte. BP 101. 97600 Mayotte (5) OCEAMM, 5 Place de la Gare – 59123 Zuydcoote, France (6) Laboratory of Ecophysiology, Biochemistry and Toxicology, Department of Biology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium and Toxicological Centre, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium The Marine Animals Research & Intervention Network (MARIN) investigated the cause of death of marine mammals stranded on the coastline of the southern North Sea (Belgium and northern France) or as bycatch delivered by fishermen. The aim of the study was to compare biological, pathological and toxicological parameters involved in the cause of death (traumatic or infectious) of harbour porpoises (Phocoena phocoena) collected between 1990 and 2008. In total, 520 porpoises were necropsied and sampled. Two causes of death appeared to prevail: firstly infectious diseases 191 animals had severe parasitosis and pneumonia, and secondly bycatch in fishing nets: 120 porpoises had died of trauma, mostly due to bycatch in fishing gear. Most strandings and bycatches occurred in winter, and there were more males than females. The majority of