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Right whales’ survival rates plummet after severe injury from fishing gear

Whale survival rates plummet after serious gear injury

“Gannet,” a reproductive female North Atlantic right whale, was sighted in 2011 with serious entanglement injuries. She was never seen again. Credit: New England Aquarium, taken under DFO license

Most North Atlantic right whales seriously injured by entanglement in fishing gear die within three years, a new study led by scientists from the New England Aquarium and Duke University shows.

North Atlantic right whales are a critically endangered species whose populations have been shrinking in recent decades. Scientists estimate that fewer than 350 of the iconic whales still live in the wild.

To investigate the role fishing gear entanglements played in the species’ decline, the researchers tracked the results of 1,196 entanglements involving 573 whales between 1980 and 2011, and categorized each call based on the severity of the injury sustained.

The data showed that male and female whales with serious injuries were eight times more likely to die than males with minor injuries, and only 44% of males and 33% of females with serious injuries survived beyond 36 months.

Females that did survive had much lower birth rates and longer calving intervals, a worrying trend for the long-term survival of the species.

“This species is headed for extinction because of human activity,” said lead author Amy Knowlton, senior scientist at the New England Aquarium. “This study sheds more light on the role of fishing gear entanglement in their decline. Even if a whale survives an entanglement, the injuries it sustains will continue and can affect its health.”

“Our findings underscore the urgent need for changes in fixed-gear fishing,” said Robert Schick, a research scientist at Duke’s Nicholas School of the Environment, who was co-lead author of the study.

Knowlton, Schick and their colleagues published their study in the journal Conservation and Practice

Entanglements from North Atlantic right whales usually occur in fixed fishing gear, including lobster and crab pots and gillnets, after an animal has collided with ropes in the water. The resulting injuries can range from superficial wounds with no equipment still attached to the whale’s body, to cases where the fishing line wraps tightly around the body, possibly many times, causing deep wounds, reduced nutrition and much higher energy expenditure for the whale. caused. it drags the heavy equipment through the open ocean.

While most gear interactions only produce scars, the new study shows that the number of serious entanglements — those with attached equipment or serious injuries — is increasing and that the sub-lethal effects of these entanglements are more pronounced than previously reported.

“What really surprised us was the reduction in survival regardless of whether the gear is attached or not, which was especially evident in women,” Schick said.

While whales have shown they can adapt to many threats, including how climate change is making the prey species they depend on for food less predictable and harder to find, the new findings suggest they have a harder time adapting to changes in fishing activities, including expanding fishing effort and strengthening ropes. These findings bolster other recent research suggesting that human activities, particularly gear entanglement, are the leading cause of death and serious injury of North Atlantic right whales and the main driver of the current population decline.

“Saving the right whale from imminent extinction requires drastic changes in the way fixed gear operations are currently conducted,” Knowlton said. “We believe these changes will require support from both the US and Canadian governments to help the fishing industry transition to equipment that will enable the industry to operate in a way that is safer for whales and other marine species. ,” she said.

A wave of entanglements in whales could inform regulation

More information:
Amy R. Knowlton et al, Gear entanglement threatens recovery of critically endangered North Atlantic right whales, Conservation and Practice (2022). DOI: 10.1111/csp2.12736

Provided by Duke University

Quote: Right whale survival rates plummet after serious gear injury (2022, June 14) retrieved June 14, 2022 from https://phys.org/news/2022-06-whales-survival-plummet-severe-injury.html

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