Research Document - 2016/085

Preliminary analysis of human-induced injury and mortality to cetaceans in Atlantic Canada

By D. Themelis, L. Harris, and T. Hayman

Abstract

Information on human-induced injuries to cetaceans occurring in Atlantic Canada is required to evaluate the effectiveness of recovery strategies for species at risk and to support management decisions on mitigation measures to reduce risk of entanglement of cetacean species from commercial fisheries. Fisheries and Oceans Canada (DFO) undertook an analysis of available data to calculate the average annual rate of human-caused serious injury and mortality of marine mammals (excluding pinnipeds) in Atlantic Canada over the period of 2008 to 2014. Observed incidents of injured and dead cetaceans were compiled from opportunistic sightings of marine mammal strandings and human interactions reported to marine mammal response networks, entanglements recorded by at-sea observers during commercial fishing, and mortalities reported from platforms of opportunity such as Transport Canada pollution patrols and PAL Surveillance flights for DFO Conservation and Protection Division.

More than 800 incidents were reported by marine mammal response networks. Small odontocetes (Pygmy Sperm Whale, White-sided, Common, Risso’s, Striped and White-beaked dolphins and Harbour Porpoise) were most commonly reported, followed by baleen whales (North Atlantic Right, Humpback, Minke, Fin, Sei, Blue, and Bowhead whales) and large odontocetes (Beluga, Northern Bottlenose, Sowerby’s Beaked, Sperm, and Pilot whales). The animal was reported dead in 65% of all observed incidents and the cause of death was unknown for 80% of these mortalities. A third of all observed incidents were attributable to fishing operations or collisions with vessels. Entanglement in fishing gear was the most common type of incident reported for North Atlantic Right Whale and Humpback Whale and for approximately half of the incidents reported for Minke Whales and Harbour Porpoise. Identifiable gear types were pot and trap (crab or lobster trap), fixed traps (capelin, cod, mackerel, weir), and nets (seine, gillnet). The estimated annual injury rate for North Atlantic Right Whale exceeds the potential biological removal estimated for the population. Fisheries-specific bycatch of small odontocetes could be estimated from at-sea observations of fishing operations, but coverage is low and data were not available from all regions of Atlantic Canada. Standardizing data collection and reporting protocols, prioritizing the collection of detailed information and necropsies, and enhancing the existing national database would improve identifying the causes of human-induced mortality and implementation of mitigating strategies.

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