Entanglement specifically refers to the wrapping of lines, netting, or other materials of anthropogenic origin around the body of an animal ¹, while bycatch refers to the unintentional capture of species such as small cetaceans in fishing nets. Worldwide, both entanglement and bycatch in fisheries operations pose a major risk for 86% of the world’s toothed whales, according to the Convention on the Conservation of Migratory Species of Wild Animals ². This review of the status of the world’s odontocetes (toothed whales) found that the primary threat for 62 of the 71 extant species is by-catch in fisheries operations, a major increase from the 2001 report that estimated only 70.4% (50 species) were affected by this risk.

Entanglement is a pressing and longstanding threat to the wellbeing of cetaceans globally. Entanglement doesn’t only cause injury and distress in whales, and restrict life-sustaining day-to-day activities; whales can also be anchored in place by fishing gear such as crab and prawn traps and aquaculture gear, causing them to drown. Various forms of fishing gear such as gillnets, driftnets, traps, weirs, purse-seine nets, long-lines, trawls and others were implicated with causing entanglement that may lead to suffocation and death of whales, dolphins and porpoises. Globally, over 300,000 small cetaceans die each year due to entanglement in fishing gear ² . Several species are at high risk of extinction due to bycatch, including the vaquita in the Gulf of Mexico and Maui’s dolphins in New Zealand.

Humpback whales (Megaptera novaeangliae) are one of the most commonly entangled species of baleen whale and well known for entanglement in fishing gear around the world. For humpback whales, half of the individuals in some large whale populations are entangled at least once in their life, including 52–78% of humpbacks in southeast Alaska³. An initial pilot study by the Marine Education and Research Society (MERS) and Fisheries and Oceans Canada (DFO) in B.C. suggest that 47% of humpbacks have scarring on their tailstocks and indicated that they have been entangled and have survived⁴. Humpback whales are especially prone to entanglement due to their morphology (e.g. long pectoral fins) and near coastal migration patterns⁵. Presence of rigid structures on the body or extremities (e.g. bumps on the head and flippers) and their comparatively rigid bodies reduces their ability to flex and maneuver free of confinement⁶. Risks from entanglement include tissue damage and infection from injury or starvation as being restrained may result in difficulties foraging and possibly reproducing.

Closer to home, on the west coast of Canada, the extent of the problem has not been extensively studied. Our vast and unpopulated coastline means that many entanglements likely go undetected or unreported; therefore understanding the scope of the problem is difficult.  In B.C., harbour porpoises are probably the most affected small cetacean. Anna Hall and colleagues estimated that approximately 80 harbour porpoises died in the South Coast salmon gillnet fishery in 2001⁷.  Of the confirmed cases of porpoise bycatch, almost half were released alive.  This bycatch included Pacific white-sided dolphins, common dolphins, and unidentified dolphin and porpoise species⁸. In 2008, Fisheries and Oceans Canada formalized the Marine Mammal Incident Response Network in British Columbia to help learn about and respond to a variety of incidents, including entanglements, which are affecting local cetaceans and pinnipeds.  The majority of entanglements reported in B.C. last year are of large baleen whales; however, entanglements of dolphins and porpoises have also been reported in the past. As of September 2017, there have been 12 confirmed whale entanglements and 640 incidents reported to the marine mammal Incidence Response Network during the year⁹. This is the largest number of whale entanglements in a single year to date. Due to the remote nature of most of the coast, mounting a quick response can be very difficult; however, where a quick response is initiated, there has been success. In other parts of North America, the issue of cetacean entanglement is better understood.  Dr. Jon Lien, a scientist at Memorial University in Newfoundland, first disentangled a whale in 1976 and brought light to the issue in Newfoundland.  Between 1979 and 2008, 1,209 large whale entanglements were recorded in Newfoundland and Labrador, mostly humpback whales (80%) and minke whales (15%). The fisheries implicated in these entanglements have shifted from primarily cod prior to the early ‘90s to the offshore snow crab fishery¹⁰. This program, the Whale Release and Stranding Network, continues operations in Newfoundland and Labrador today and also works directly with fishermen to find solutions to the problem.