The striped dolphin epizootic in the Mediterranean Sea

From 1990 to 1992, an epizootic produced a massive die-off of striped dolphins in the Mediterranean Sea. The event started in mid-Spain but extended, through three apparently interconnected outbreaks, to finally coverthe whole western Mediterranean and the Tyrrhenian and Aegean Seas. Although more than 1000 carcasses of striped dolphins were collected during the event, the total toll remains unknown because of fragmentary coverage of rescue networks and because many carcasses never reached the shore. The primary cause of the episode was identified as an infection by a morbillivirus, the origin of which could not be ascertained. The dolphins affected were found to carry concentrations of pollutants higher than normal for the general population. This difference could not be explained by variation in nutritive condition or by sex or age composition. The dolphins that died at the beginning of the outbreak were in abnormally poor nutritional condition, and had increased prevalence of ectoparasites and epizoits. This suggested that these dolphins had recently undergone a period of restricted mobility, during which the ectoparasites had found attachment easier than under normal conditions. Abnormal weatherconditions, leading to depressed marine productivity, may have been the cause of some of these anomalies.