Entanglement

Entanglement poses a major threat to cetaceans worldwide.

On the B.C. coast, the habitats of whales, dolphins and porpoises often overlap with human activities that can have harmful impacts on individual cetaceans, and populations as a whole. Entanglement in commercial fishing and aquaculture gear (both active and derelict) can cause significant injuries to whales, affecting their ability to swim and feed. Whales can also be anchored in place by fishing gear such as crab and prawn traps and aquaculture gear, causing them to drown. Entanglement is a significant threat to cetacean populations on the coast of British Columbia, and worldwide.

Entanglement specifically refers to the wrapping of lines, netting, or other materials of anthropogenic origin around body of an animal1, while bycatch refers to the unintentional capture of species such as small cetaceans in fishing nets. Worldwide, both entanglement and bycatch in fisheries operations poses a major risk for 86% of the world’s toothed whales, according to the Convention on the Conservation of Migratory Species of Wild Animals2. 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.

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 gear2. 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.

The critically endangered vaquita, found only in the Gulf of Mexico, is at high risk of extinction due to bycatch and entanglement in fishing gear.  It is estimated that only 30 inviduals remain (photo credit: World Wildlife Fund).

For humpback whales, entanglement is a common occurrence.

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.

Humpback whale locally known as “Twister” entangled in prawn traps through the mouth. (Photo credit: Doug Sandilands)

Entanglement in British Columbia

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 BC, 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.

With entanglements, there can be a lot going on under the surface of the water.  Not only is attempting to disentangle a whale on your own increadibly dangerous, cutting only the ropes on the surfaces makes the entanglement less obvious, and greatly reduces a whale’s chance of recieving help.  Call the Marine Mammal Incident Response Network immediately and stay with the whale so that it can be located easily. 

What can you do to help?

If you see an entangled cetacean in B.C., the best thing is to report the situation as soon as possible to the Marine Mammal Incident Response Network at 1-800-465-4336. The best course of action after contacting the authorities is to monitor the position of the whale at a distance so that the experts will be able to locate the distressed animal. Fisheries and Oceans Canada has a disentanglement team that is sent out who specializes in whale disentanglements. Additionally, the Ocean wise Cetacean Research Lab, Cetus Research and Conservation Society and Strawberry Isle Research are important partners in the efforts to reduce entanglements.

 One simple way to help reduce toothed whale mortality due to entanglement around the world is to choose seafood from sustainable fisheries with minimal bycatch.  In British Columbia, the Ocean Wise Sustainable Seafood Program works with seafood suppliers and restaurants to ensure that they have the most current scientific information regarding seafood and helping them make ocean-friendly buying decisions.   Sustainable options are highlighted on menus and at super markets with the Ocean Wise symbol. 

Report Entanglements!

Report an entanglement for any marine mammal or sea turtle; call the BC Marine Mammal Response Network hotline 24 hours a day at 1-800-465-4336, Remain with the animal so that it can be easily located. Do not attempt to disentangle the whale yourself.

Clean up Debris!

Help reduce the amount of debris and abandoned fishing gear in BC waters by participating in the annual Great Canadian Shoreline Cleanup, or organizing a cleanup event in your community.

Shop Sustainably!

Choose seafood from sustainable fisheries with minimal bycatch. The Ocean Wise Sustainable Seafood Program marks ocean-friendly options at restaurants and supermarkets.

References:

  1. IWC. (2010). Report of the workshop on welfare issues associated with the entanglement of large whales. Paper IWC/62/15 presented to the meeting of the International Whaling Commission, June 2010, Agadir, Morocco [To be published in: Journal of Cetacean Research and Management Supplement 13]. Retrieved from http://www.icmbio.gov.br/cma/images/stories/CIB__SORP/CIB/IWC_62_15.pdf
  2. Convention on the Conservation of Migratory species of Wild animals (UNEP/CMS)
  3. Nielson, J. L., Straley, J. M., Gabriele, C. M., & Hills, S. (2009). Nonlethal entanglement of humpback whales (Megaptera novaeangliae) in fishing gear in northern Southeast Alaska. Journal of Biogeography, 36(3), 452-464.
  4. Unpublished research, Marine Education and Research Society and Fisheries and Oceans Canada
  5. Groom, C., & Coughran, D. (2012). Entanglements of baleen whales off the coast of Western Australia between 1982 and 2010: patterns of occurrence, outcomes and management responses. Pacific Conservation Biology, 18(3), 203–214.
  6. Benjamins, S., Harnois, V., Smith, H.C.M., Johanning, L., Greenhill, L., Carter, C. &
  7. Wilson, B. (2014). Understanding the potential for marine megafauna entanglement risk from renewable marine energy developments. Scottish Natural Heritage Commissioned Report No. 791.
  8. Hall, A., Ellis, G., Trites, A.W. (2002). Harbour Porpoise Interactions with the 2001 Selective Salmon Fisheries in Southern British Columbia and License older Reported Small Cetacean By-Catch. Selective Salmon Fisheries Science Program Report. Fisheries and Oceans Canada.
  9. Driscoll, J., Rob, C., and Bodtker, K. (2009).  Bycatch in Canada’s Pacific Groundfish Bottom Trawl Fishery: Trends and Ecosystem Perspectives. A Report by Living Oceans Society. (link)
  10. Cotrell, P., personal communication, September 20th, 2017.