Pathology and causes of death of cetaceans stranded in Canary islands (1999-2005)

Abstract

In the Canary Islands waters, 28 cetacean species have been identified of which 24 species have been found stranded. During a 6 year-period (1999- 2005) 233 stranded whales and dolphins of 19 different species were recovered for scientific studies. Using a systematic standardized necropsy protocol, 138/233 stranded cetaceans were subjected to a complete or partial necropsy. Of these, 71/138 (51.45%) carcasses were in a very fresh or fresh status, 28/138 (20.29%) in moderate autolysis and 39/138 (28.22%) in advanced autolysis. Pathological studies were conducted by the Institute of Animal Health (University of Las Palmas de Gran Canaria) in order to identify lesions and to determine a morphological diagnosis, identify aetiological agents, and, ultimately, to reach an etiological diagnosis. As a result of these processes, cause(s) of death (defined as pathological entities) were identified wherever possible. From a total of 233 cetaceans stranded in the Canary Islands (1999-2005), in 59,23% of the cases a morphological diagnosis was done, in 56,22% an etiological diagnosis could be established and, finally, we were able to classify 51,07% within natural or anthropogenic pathological entities. Etio-pathologically, 62,32% of the 138 studied cetaceans were diagnosed as natural (i.e. non-anthropogenic) pathological entities that included infectious diseases, neonatal pathology, intra- and interspecific interactions and typical mass strandings. Another 33,33% of cases were diagnosed as anthropogenic entities including fishing interaction (by-catch), atypical mass-stranding linked to naval exercises, ship collisions, and other anthropogenic-related pathology. A cause of death could not be ascribed in only 4,35% of the 138 animals examined.