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Entanglements of endangered leatherback sea turtles overwhelmingly caused by active fishing gear: Report

A sea turtle is entangled in fishing gear.
Sean Whelan
A sea turtle is entangled in fishing gear.

Over the last 15 years, boaters, environmentalists, and fishermen have reported sightings of entangled sea turtles in Massachusetts waters. For the first time, data for 280 of those entanglement cases have been analyzed, revealing new insights about one of the endangered sea turtle species on the planet.

The study, with contributions from the New England Aquarium, the Center for Coastal Studies, International Fund for Animal Welfare (IFAW), and NOAA Fisheries, examines what gear sea turtles are getting entangled in most frequently, who most often reports the incidents, and how well the animals fare after disentanglement. It also addresses what body parts are most likely to be entangled, which will help scientists “figure out how it happened so that we can try to make some changes that will help prevent the entanglement,” said New England Aquarium scientist Kara Dodge, the lead researcher.

The scientists, who published their work in Endangered Species Research, found that of 280 confirmed sea turtle entanglements documented from 2005 to 2019 in Massachusetts waters, 272 involved leatherback turtles. Leatherbacks, the largest turtles in the world, are often called “living dinosaurs” because they have existed for nearly 100 million years.

Around 95 percent of the sea turtles studied were entangled in actively fished, commercial pot/trap gear that was set to catch lobster, whelk, and other fish — rather than ghost gear or debris. All entanglements involved the turtles’ necks and/or front flippers.

Those insights, Dodge said, have implications for future fishery management.

“All of that is really important to know when you're starting to look at things like gear modifications or changes to fishing gear,” she said. “Without having that data from the field, it's impossible to do that.”

Researchers say replacing single, fixed-gear fishing traps with trawls, and transitioning to ropeless fishing gear could reduce entanglements in the future.

Current efforts to make fisheries safer are often designed for whales, Dodge added, but they’ll need to expand to protect smaller sea creatures, like leatherbacks.

“We have the North Atlantic right whale getting entangled in basically the same type of fishing gear,” Dodge said. “And I feel like that's where a lot of the effort has gone.”

For example, she said, weak ropes that commercial lobstermen are now required to use in Massachusetts to protect critically endangered right whales are designed to break when exposed to 1,700 pounds of tension, but even the biggest leatherbacks only reach six feet in length and weigh around 1,000 pounds.

“The way they're currently configured, they're set to break for a much larger, more powerful animal,” Dodge said. “So I do think there's a misconception that some of these fixes provide benefit to leatherback turtles where there really isn't a benefit. And what I'm hoping is that [this research] will shine a light on that and [policymakers will] say, ‘Oh, we need to think about some turtle specific gear modifications to help these animals.’ It's not just going to be a side benefit from changes made for right whales.”

The study did include two bright spots. First, researchers found that in cases with sufficient documentation, 88 percent of completely disentangled turtles were predicted to have a “low or intermediate risk of death based on their degree of injury.”

In fact, many sea turtles that were tagged after disentanglement were confirmed to be alive weeks to years later.

Also, researchers revealed, recreational boaters have become unlikely saviors of leatherback sea turtles entangled in fishing gear.

The study found that 60 percent of entanglement reports over the last 15 years have came from recreational boaters, “which was a little bit of a surprise to me,” Dodge said. Fishermen reported 12 percent of cases.

“It makes us realize that we're really quite reliant on the boating public to help us understand what's going on out there.”

As the weather warms and mariners get back out on the water, researchers ask that all entanglements off southern New England be reported immediately to local responders, including the Center for Coastal Studies hotline (1-800-900-3622).

Attempts to disentangle a turtle without training should never be attempted, given dangers both to humans and animals.

Eve Zuckoff covers the environment and human impacts of climate change for CAI.