Retrospective study of foreign body-associated pathology in stranded cetaceans, Canary Islands (2000-2015)

Abstract

The Canary Islands (CIs) shelter up to 30 different cetacean species. Marine pollution has increased exponentially worldwide due in part to the use of plastic since half of the last century (2). Thirty-six out of 465 (7.74%) cetaceans necropsied, referring to 15 species stranded in the CIs from January 2000 through December 2015, presented at least one foreign body (FB). Occurrence of FBs was higher in Risso’s dolphins (4/12; 33.33%), sperm whales (6/28; 21.43%), Mesoplodon sp. (4/19; 21.05%), followed by Cuvier’s beaked whales (5/33; 15.15%) and mysticetes (2/17; 11.76%). Eight out of nine cetacean species affected by FB (88.89%) are present year-round. Main FB-associated lesions included ulcerative gastritis with presence of luminal blood (14/36; 38.89%), impacted stomach (9/36; 25%), gastro-intestinal perforations (3/36; 8.33%), ulcerative glossitis (2/36; 5.56%), stomatitis (2/36; 5.56%), cicatrized ulcers (2/36; 5.56%) and petechias (1/36; 2.78%). Plastics were present in 80.55% of FB cases (eg. bags), ropes/threads (19.44%), metal filaments (8.33%), cloth elements (2.78%), electric wires (2.78%) and glass fragments (2.78%) were found in the gastric compartments. FB was directly associated with death in 13 out of 36 (36.11%) animals. Poor body condition and deep diving behavior were found to be a risk factor for FB ingestion (FBI) meanwhile the adult age was a protective factor. This study reveals detrimental effects of anthropogenic marine debris on free-ranging cetaceans in the CIs and may poses scientific fundament for future conservationist policies.