Fishing gear entanglements are now the leading cause of serious injury and death for the critically endangered North Atlantic right whales, according to researchers.
The scientists from the New England Aquarium and Duke University tracked the outcomes of 1,196 fishing gear entanglements involving 573 right whales between 1980 and 2011 — and grouped each run-in based on the severity of the injury.
The data revealed that male and female right whales with severe injuries were eight times more likely to die than males with minor injuries. Also, only 44% of males and 33% of females with severe injuries survived longer than 36 months.
Health impacts from entanglements are also reducing reproductive success in the critically endangered species, with an estimated population of less than 350 individuals.
“This species is heading quickly towards extinction because of human activities,” said Amy Knowlton, a senior scientist at the New England Aquarium. “This study sheds further light on the role of fishing gear entanglements in their decline. Even if a right whale survives an entanglement, the injuries it sustains endure and can impact their health.”
Entanglements of North Atlantic right whales typically occur in fixed fishing gear, including lobster and crab pots and gillnets after the whale collides with ropes in the water.
The resulting injuries can range from superficial wounds with no attached gear to cases in which the line becomes tightly wrapped multiple times around the whale, resulting in deep wounds, impaired feeding, and energetic costs caused by dragging the heavy gear.
For this study, the researchers investigated the effects of all entanglements, including cases with only scars, which comprise the majority of documented entanglement events.
“Previous work has shown reduced survival when the whale is carrying gear, but what really surprised us was the reduction in survival regardless of whether gear was present, which was especially apparent in females,” said Rob Schick, a research scientist at Duke University.
Female right whales with severe injuries who survived had the lowest birth rates. As the health of reproductively active females declined, their calving intervals also increased — a worrisome trend for the long-term survival of the species.
“If we are going to save right whales from imminent extinction, dramatic changes to how fixed fishing gear activities are presently conducted are needed,” Knowlton said. “We believe these changes will require support from both the U.S. and Canadian governments to help the fishing industry transition to gear that will allow the industry to operate in a manner that is safer for whales and other marine species.”
