Cetacean Strandings in the Canadian Maritime Provinces, 1990-2008

Abstract

Organized cetacean stranding networks function to respond quickly and efficiently to strandings, to coordinate live releases, to gather and analyze data, and to educate the public. Stranding networks in the three Canadian Maritime provinces (New Brunswick, Nova Scotia, and Prince Edward Island) recently cooperated to form the Marine Animal Response Network. The resulting collaborative database provides an opportunity to assess patterns of cetacean strandings encompassing 19 years (1990-2008 inclusive) from across the region. During this period, a total of 640 stranding events involving 19 species and 881 individuals of both sexes and varying age groups were reported. Stranding events primarily involved single animals, although several mass strandings were recorded, the largest involving 60 Long-finned Pilot Whales (Globicephala melas). The number of strandings was found to vary substantially over time and among the three provinces. In part, this is likely a reflection of differences in local network effort among regions. Most animals were found dead ashore. Entanglement in fishing gear occurred in over 10% of the incidents. Relatively more mysticetes were found dead ashore or at sea and entangled in fishing gear than expected by chance, while more odontocetes were found stranded alive than expected. Harbour Porpoises (Phocoena phocoena) appear to be especially vulnerable to entanglement in fishing gear. Necropsies, performed on a subsample of the stranded animals, suggest that Harbour Porpoises die significantly more often from disease than mishap, while Long-finned Pilot Whales and Atlantic White-sided Dolphins (Lagenorhynchus acutus) suffer equally from mishap and disease. Refloating was attempted for 23% of animals, with an apparent success rate of 83%, although there are no data on long-term survival. Neither sex nor age of the refloated animals was found to be an indicator of subsequent short-term survival.