Nearly 90% of humpback whales off Long Island scarred by entanglements, Stony Brook survey finds

A six-year survey of humpback whales that are increasingly lingering in the waters off Long Island found almost 90% carried scars from entanglement in fishing ropes or nets. A smaller but still significant number, particularly young whales, had been wounded by ship propellers.

Researchers from Stony Brook University used drones to take images of the whales swimming off the South Shore, which allowed them to capture a more comprehensive view of the animals’ bodies than is generally possible when taking photos from a boat.

Between 2018 and 2024, they collected clear images of 122 whales, and found about 87% of them — both adults and juveniles — bore entanglement scars. Of the juveniles, 14% had the unmistakable slash marks caused by a ship’s propeller; 2% of the adults had been cut by propellers, according to their study, published last month in the peer-reviewed journal PLOS One.

Entanglements from commercial fishing gear and vessel strikes in shipping lanes are thought to be the leading causes of whale mortality on the East Coast.

"It's sobering to realize how often these animals are interacting with fishing gear," said Lesley Thorne, the director of the Thorne Lab at Stony Brook University’s marine science department and the lead scientist on the study. And "even more sobering," she said, "was the proportion of juveniles that had evidence of vessel strike scars."

Summering off Long Island

Thorne cautions that once a wound has healed, it’s hard to know where these whales, which migrate between the Caribbean in winter and as far north as Labrador, Canada, in summer, got entangled or injured by a propeller.

But in the past 15 years, more humpbacks have been spending their summers foraging off Long Island, a response in part to more abundant prey like menhaden, Thorne said. And that places them in and around one of the busiest shipping lanes in the world.

More than 255 humpback whales have been found dead along the East Coast since 2016, according to the National Oceanic and Atmospheric Administration, which led the agency to declare an "unusual mortality event" in 2017 that has not abated. A disproportionate number of those deaths and strandings have occurred on New York’s shores. 

The scar study doesn’t reveal the extent of the ship strike problem, Thorne noted, because drone footage can’t detect "blunt force injuries" — which are often fatal. But her previous research showed that the higher death toll is a fatal combination of more whales in the area and "marked increases in vessel traffic going into the port of New York." 

She found no evidence that offshore wind developments were implicated in these deaths.

The entanglements she documented, on the other hand, may well have happened in waters far from Long Island, possibly in the whales' traditional feeding grounds in the Gulf of Maine.

Most of the danger comes from fixed gear fisheries — gill nets and traps that are set at the ocean bottom and left for days or a week at a time, said Regina Asmutis-Silvia, executive director of Whale and Dolphin Conservation (North America), based in Plymouth, Massachusetts. The vertical buoy lines tethered to lobster, conch or other traps and wide gillnet panels can snag a passing whale; often, they panic when they realize they are caught, but their thrashing and twisting only pulls the ropes tighter.

"Entanglements are a pervasive threat" to humpbacks and other whale species, Asmutis-Silvia said.

Some animals drown if they can’t reach the surface to breathe. Others may drag along a net or rope and the attached lobster pots for months, hindering their swimming and feeding. During their surveys, Thorne said she and her colleagues "encountered a severely entangled whale," which they reported to disentanglement teams. But the whale was emaciated, and Thorne said she suspects the animal died shortly after.

Over time the gear can also cause severe abrasions and deep lacerations, which can become infected. "All of these are painful injuries," Thorne said. A rope wrapped tightly around a fluke or fin can slowly amputate it.

Protecting whales with ship speed limits

NOAA has set speed limits for places whales are likely to be feeding and traveling: Ships 65 feet or longer must travel at 10 knots or slower. (The agency encourages smaller boats to observe the limits too, as even a pleasure boat can injure a whale.) The limits were established to protect the critically endangered North Atlantic right whale, but other species benefit as well.

Ships must observe the speed limit from November through April in a patch of ocean that includes the far western part of Long Island and another that stretches from Montauk Point to Martha’s Vineyard. Most of Long Island’s coastal waters aren’t restricted.

And whales have been altering their habits — probably in response to shifting prey movement and warming oceans, marine biologists say — so the protected zones no longer precisely match the areas where whales are swimming. NOAA has established "dynamic managed areas" for these changing habitats, where slow speeds are recommended. While NOAA’s speed zone dashboard shows vessels generally abide by the limits when traveling through mandatory protected zones, Asmutis-Silvia said "compliance with the [voluntary] recommendations is really low."

Whale and Dolphin Conservation and other groups have been fighting for years to expand the mandatory slowdown zone, but in January, before President Joe Biden left office, NOAA withdrew a proposal to set mandatory speed limits in the dynamic zones. Not surprisingly, research shows that slower speeds reduce severe injuries and fatalities.

New fishing gear to reduce entanglements

Entanglements can be reduced with sophisticated fishing equipment. Five years ago, NOAA established a "lending library" of 10 different models of electronic fishing gear in Woods Hole, on Cape Cod, and invited local lobstermen to try them out.

Instead of marking their submerged traps with a buoy, the lobster harvesters locate them with a GPS or acoustic signal and recall them by remote control, which — depending on the model — deploys an inflatable lift bag, pop-up buoy or buoyant spool.

No buoy lines suspended in the water column means no hazard to passing whales, sea turtles or other marine animals. Now more than 50 boats are using these whale-safe traps, according to Asmutis-Silvia, whose group collaborated with NOAA on the project, and the lobstermen’s suggested modifications have been incorporated into the manufacturers’ designs. "They've been really helpful in improving the gear dramatically," Asmutis-Silvia said. "It's been really, really promising and a really viable way forward."

Those devices are far more expensive than standard gear, as Beth Casoni, executive director of the Massachusetts Lobstermen's Association, pointed out, and they can be time-consuming to use. The association opposes the existing restricted zones because of the impact on fishermen's livelihoods. But Casoni, who is a member of the Atlantic Large Whale Take Reduction team, formed by NOAA 30 years ago, said her group nevertheless has been working to develop techniques that could reduce entanglements. One method, for which the association has received a federal grant, is to use a GPS locator on fishing gear but then to retrieve the trap with a simple grappling hook.

"It's a tool in the toolbox for the fishermen to use," Casoni said, which could "help mitigate serious injury and mortality to the large whales."