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Entangled in Fishing Gear

The entanglement of small and large cetacean species in fishing gear and other man-made materials has long been a major problem world-wide which has only increased with enhanced technology in the fishing industry and the introduction of synthetic materials since the mid 20th century. While entrapments are often fatal for individuals, which is a tragedy in itself, such anthropogenic impacts can seriously jeopardize the recovery of critically endangered species such as the Vaquita (Phocoena sinus) or the North Atlantic right whale (Eubalaena glaciali), of which only a few hundred animals are left.

Great efforts are being made to minimize possible trappings by enhancing fishing gear or developing scaring devices called pingers, to keep animals away. But we are far from solving the problem. Still today, about 300 000 large and small cetaceans are facing needless death in by-catches and entanglements in  fishing gear worldwide.

Many giants die later

For large whales, such incidents are not immediately fatal as they can carry heavy loads of gear for some time. Yet, nets and ropes wrapped around their mouths, heads, flippers, peduncles, and tails restrict their swimming, diving and feeding abilities. If the animal can't free itself somehow, death might occur months later as a result of starvation or chronic infection. Some fishing gear is heavy enough to immobilize a whale, especially one of a smaller size such as a minke whale. If this happens below the surface, the animal will drown.

Whales at our mercy

Despite the collapse of the commercial fisheries in the originally rich waters off the east coast, ten thousand whales are still dying in fishing gear. Off Maine, humpback whales and right whales and off Newfoundland, mainly humpback and minke whales  get entangled. Off New England, not all species are exposed at the same scale as 55% of reported cases involved humpback whales, 29% Northern right whales, 12% minke whales, and 4% finback whales.

It also seems that juveniles are significantly more likely to become trapped than adults. In Newfoundland, Jon Lien reported a mortality rate of 16% in humpback whales but, due to their smaller size, 70% in minke whales, suggesting that the probability of lethal entrapments may vary by species. Additionally, evidence suggests that a history of entanglement reduce the reproductive rate of female humpback whales which might apply to other species just as well.

Dedicated efforts to save at least those found

In the 1970s, Jon Lien from Memorial University in St. John, pioneered the disentanglement of large whales off Newfoundland by creating a network of trained rescuers and fishermen. In 1984, they were joined by the Center for Coastal Studies in Provincetown, Massachusetts. In other areas worldwide a growing number of rescue networks developed in past years such as theRéseau québecois d'urgences pour les mammifères marins monitoring the St. Lawrence Gulf.

Personal opinion

by Ursula Tscherter

One might ask if it makes sense to save one whale’s life. I believe that yes, we are morally committed to try a rescue within the limits of the specific situation, especially when the threat is caused by human activities. Especially  as saving an individual might be crucial for the species’ survival like the North Atlantic right whales or the minke whales in the Sea of Japan.

However, following the present policy a rescue shall only be undertaken by trained people without putting human lives in danger and only if the entanglement is life-threatening to the animal. This is not always assessable from the surface as the sad end of Tryphon, the best-known sperm whale of the St. Lawrence, proves. After a not fully successful disentanglement in 2008 the ropes left on the whale lead to its death within a couple weeks.