Reducing Excess Rope Strength in Fishing Gear
Could Cut Whale Deaths from Entanglements by 72 percent
BOSTON (December 2015) - Along the U.S. East Coast and the Canadian Maritimes, reports of a whale entangled in ropes used in commercial fishing are a near weekly event. When a whale gets entangled in these ropes, the event can lead to either immediate death by drowning, or delayed death from impaired feeding or infection as a result of deep injuries. It can be a long, painful process of dying for these entangled whales.
In recent decades, the known deaths of endangered whales due to entanglements have exceeded legal federal limits every year. Now, a novel study initiated by the Consortium for Wildlife Bycatch Reduction and conducted by the New England Aquarium and the Center for Coastal Studies has found that employing ropes that break more easily under the force of a moving whale could be a solution to reducing life-threatening entanglements.
In the scientific journal, Conservation Biology, the Aquarium’s Right Whale Research Team scientist Amy Knowlton and colleagues examined ropes retrieved from live and dead whales entangled in fishing gear from 1994 to 2010. They concluded that switching to ropes that break at less than 1,700 pounds could reduce life-threatening entanglements for large whales by as much as 72 percent while still working sufficiently for a substantial portion of the fishing industry.
According to the authors, this is “the first evidence-based analysis that supports a modification to fishing gear that would reduce the incidence of serious whale entanglements in fixed fishing gear.” In their sampling, the scientists assessed 132 ropes retrieved from 70 large whale entanglement situations. They analyzed the rope diameters, polymer types, and breaking strengths. Gear was retrieved from right whales, humpbacks, minkes, and fin whales along the east coast of the U.S. and Canada.
The team showed that the severity of entanglement injuries increases with duration of the entanglement, the amount of gear being dragged by the whale, and whether the whale (in the case of a younger individual) grows into the constricting rope. The most important finding was that right and humpback whales were found entangled in ropes with a significantly higher breaking strength than smaller minke whales, and adult right whales were found in significantly stronger ropes than young right whales and all humpbacks. These patterns demonstrated that it is difficult for whales to break free from many ropes used in fishing
If reduced breaking strength (RBS) ropes were manufactured and used more widely by fishermen, dozens of whales will be saved each year. Entanglements will still happen, but they may not become as serious. Although RBS ropes are not suitable for all fishing locations, the team suggested that where they cannot be used, other alternatives such as rope-less fishing should be considered.
“Considering that entanglement is one of the most urgent conservation issues facing marine mammals, adopting this relatively simple gear modification is a promising option for reducing the number of unnecessary deaths and suffering by whales around the world,” the team concluded.
A free link to the paper can be found here: http://onlinelibrary.wiley.com/doi/10.1111/cobi.12590/abstract
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