Anthropogenic causes of mortality of sea turtles in the Canary Islands: A multidisciplinary approach to the conservation of endangered sea turtles

Abstract

Because all species of sea turtles are included on the Red List of the World Conservation Union, the efforts to conserve sea turtles, the advances in their medical management, and the studies on diseases and causes of mortality and/or stranding of sea turtles must to be increased. A multidisciplinary approach to this focus carried out by veterinarians, biologists, and scientists, is necessary in order to compile data that prove the main threats for these endangered reptiles, and to design adequate strategies of conservation. This chapter lists the pathological findings and causes of mortality of 49 sea turtles (46 Caretta caretta, 2 Chelonia mydas, and 1 Dermochelyscoriacea) stranded on the coasts of the Canary Islands, Spain, between 2002 and 2009.Of these, 12 turtles (24.49%) had died of spontaneous diseases including different types of hepatitis, pneumonia, and septicemic processes. However, 37 turtles (75.51%) died from lesions associated with human activities: ingestion of hooks and monofilament lines (34.69%), entanglement in fishing nets (24.49%), and boat-strike injuries (16.33%). In addition, polychlorinated biphenyls (PCBs 28, 31, 52, 101, 138, 153, 180, and 209) and DDT and its metabolites (o,p'-DDT, o,p'-DDE, and o,p'-DDD) were measured in liver and fat from 32 sea turtles. Tissues from these turtles contained higher levels of PCBs and o,p'-DDT than those reported in turtles from other geographical regions. Statistically, a positive correlation was detected between ΣPCBs concentration and cachexia, and between ΣDDT concentrations and cachexia. No histological lesions exclusively attributed to the acute effects of PCBs and DDTs were described. However, chronic effects of organochlorines can not be discarded.