Skip to content

Connect with WHOI:

Keeping an ear out for entangled whales

New navigation system helps autonomous vehicles find their way

By Evan Lubofsky | August 24, 2021

Sea Shepherd's Enrico Salierno (right) and his colleagues attempt to disentangle "Fury" from an illegal drift net in 2019 off the coast of Sicily. (Image by the Italian Coast Guard)

The Search for Entangled Whales May Get Easier

By Evan Lubofsky | August 24, 2021

Sperm Whale
Divers attempt to disentangle "Fury" the whale from an illegal drift net in 2019 off the coast of Sicily. (Image by the Italian Coast Guard)

Enrico Salierno didn’t need a bigger boat. He needed a bigger knife.

Fury, a juvenile sperm whale the size of a small ship, thrashed its tail up and down as Salierno braced himself and began slicing through fistfuls of the nylon drift net wrapped around the whale’s body. Salierno, a diver with the marine conservation non-profit Sea Shepherd Italia, was no stranger to whales caught illegal fishing gear. But this was the first time he actually jumped in the water to attempt a disentanglement.

Salierno didn’t have a lot to work with. Mainly a knife, a pair of scissors, and a bit of help—his diving partner, Carmelo Isgrò, a marine biologist at the Museum of the Sea in Sicily, jumped in with him. But Fury, aptly named, was agitated. The massive mammal wriggled relentlessly to try to free itself, which worsened the tangles, particularly around its tail. It looked like the target of a silly string attack.

“Fury was having trouble swimming, and was losing blood from its tail,” says Salierno. “An Italian coastguard boat had accompanied us, so we tried to put a really thick, strong rope around the tail and connect it to the boat to keep Fury stationary. But it was very powerful and angry and broke the rope immediately. It clearly didn’t want to be stopped or have people around.”

Despite the danger, Salierno and Isgrò somehow kept on hacking away at the mesh netting as the writhing whale kept on. After a few hours, Fury’s head and body were free. But by that time, his tail had been wrapped many times over.

 

According to the United Nations, the Mediterranean Sea is the most overexploited in the world, with more than 60% of its fish stocks in collapse. Illegal fishing is among the main culprits—an estimated 40% of fish in the Mediterranean market come from these fisheries. And in Italy specifically, the use of large mesh drift nets which has been banned since 2002, continues to take its toll on whales like Fury. This, despite the fact that the European Union has paid fishers not to use them.

“Wildlife conservation groups in Sicily have been reporting a growing number of sperm whales with nets wrapped around their bodies and tails,” says Alex Bocconcelli, a senior research specialist at WHOI. “These illegal drift nets target tuna and swordfish, but they’re a real problem for marine mammals and megafauna such as sharks, sunfish and turtles that can easily become ensnarled in them.”

Stefano Marsala, a volunteer with Sea Shepherd, holds an illegal fishing net he pulled from the ocean with WHOI scientist Alex Bocconcelli in the Aeolian Islands. (Photo by Nicole El Haddad, Woods Hole Oceanographic Institution)

Alex Bocconcelli
Stefano Marsala, a volunteer with Sea Shepherd, Italy, pulls up an illegal fishing net with WHOI scientist Alex Bocconcelli in the Aeolian Islands. (Photo by Nicole El Haddad, Woods Hole Oceanographic Institution)

Entanglement-related sperm whale mortalities in the Mediterranean Sea, according to recent research, went from roughly 20-30 cases per year prior to 1990, to more than 100 cases per year in 2010.

One of the biggest problems with drift nets is their size. They often extend from the ocean’s surface to the bottom for hundreds of feet, and can run horizontally for dozens of miles. These massive mesh walls can block the paths of sperm whales, sea turtles, sharks and, ironically, even fishing boats.

Drift nets can also be incredibly tough and resilient. Many of the nets used today are made from synthetic monofilament material that is roughly the thickness of fishing line. These tend to be easier for whales and other animals to free themselves from, and for disentanglement teams to cut through. But many older-style nets are made with a twisted, knotted nylon mesh, which can be much harder to break through and tends to slice into an animal’s skin over time.

Bocconcelli, an Italy native, has investigated the impacts of underwater noise on whales of the coast of Sicily, which he says “makes it impossible for them to hunt and reproduce.” Through an association with Sea Shepherd, he became more aware of the additional threat of fishing net entanglements in the region and the lack of policing.

“Enforcement has no presence at sea,” he says. “I did a two-week cruise in the Aeolian Islands off of Sicily this past July and never once met or saw an enforcement agency boat.” The Italian government, he says, doesn’t have the resources to adequately police the waters off Sicily.

Salierno, who Bocconcelli met through his association with Sea Shepherd, is also concerned about the lack of enforcement. He notes that Sicily has been slammed with migrant arrivals by sea, which hasn’t helped.

“The sea is just so huge and Sicily is so close to line of people arriving from Africa,” he says. “The Coast Guard is very stressed from all the migration.”

 

Six hours had passed since Salierno and Isgrò began slicing through the drift net. It had become so thickly layered around Fury’s tail that no matter how hard the divers worked at it, it was impenetrable. And Fury’s increasingly erratic behavior made the job even harder. The whale continued to thrust its tail violently up and down, the sheer force of which could injure or kill a person. “Fury was trying to get us away using its tail,” says Salierno.

As "Fury" surfaces, his body and head are free from entanglement but his tail remains wrapped in the mesh netting. (Photo courtesy of Enrico Salierno, Sea Shepherd Italia)

Whale
"Fury" surfaces with his body and head freed from entanglement, but his tail is still tightly wrapped in the mesh netting. (Photo courtesy of Enrico Salierno)

It’s typical behavior for sperm whales when perceived enemies are present. Female sperm whales, for example, defend their babies from killer whales by forming a marguerite flower-like circle around the young calves. Then, they thrash their tails about the perimeter to keep the predators away.

Salierno and Isgrò were physically exhausted and needed a break from disentangling Fury. They asked members of Filicudi WildLife Conservation who had arrived at the scene to stay with Fury and watch over it so they could eat and rest up for what was likely going to be a long night.

 

Alex Bocconcelli is disgusted with rampant illegal fishing in his homeland. He knows he can’t stamp out the problem, but wants to help mitigate what he can. He has recently banded together with Salierno’s team at Sea Shepherd, the Anton Dohrn Stazione Zoologica, Filicudi WildLife Conservation, and the CIMA Research Foundation, to come up with potential solutions.

One idea is to attach a digital acoustic recording tag (DTAG) to drift nets that have trapped whales or other marine mammals. The non-invasive tags are roughly the footprint of a mobile phone, and are designed to track the behavior of whales and record their vocalizations and ambient noise as they dive.

“We can use DTAGs as tracking beacons for entangled whales so we can keep track of the injured animal while waiting for disentanglement crews to arrive,” says Bocconcelli. “These particular whales are deep diving and can reach depths of at least 6000 feet. But eventually they come back up to surface, and when they do, the tags will emit VHF signals that we can track in real time.”

Bocconcelli envisions attaching DTAGs to drift nets in a similar fashion to tagging whales. From a Zodiac boat, he and one or two other researchers will follow an entangled whale and then carefully approach it from behind. Once the whale emerges, the tagger will use an eight-foot carbon fiber pole to attach the DTAG to the top edge (or cork line) of the net. The beacon will also collect data on the whale’s sound production and movements to provide insights into some of the physiological impacts of entanglement.

 

Salierno and Isgrò motored back out to the site around 9pm. At that point, it was too dark to see Fury so they attached a small light to its tail in order to see its movements. Then, they jumped back in the water. Fury clicked and creaked in rapid succession, another sign of his distress, and began slowly trying to swim north.

The divers worked through the night. But by morning, they only had 20% of the net removed from Fury’s tail. The Italian coastguard returned to the site, this time with a group of professional divers from the Coast Guard. They told Salierno that they would take over the operation. As difficult as it was, he and Isgrò left Fury and headed back to their homes.

“It was frustrating to see such a magnificent animal struggling to swim, and all for human fault,” recalls Salierno.

Within a few hours, Fury dove down into the water column. The whale never resurfaced.

 

Bocconcelli plans to go back to the Aeolian Islands this Fall to test out the acoustic beacon technology. He and colleagues will first survey for sperm whales around the Aeolian Islands aboard the M/Y Conrad, Sea Shepherd’s 17-meter-long catamaran. The survey will involve visually searching for whales through binoculars, and dropping towed arrays with microphones known as hydrophones into the water to listen for them.

“The data we collect has the potential to be used for fisheries management and even possibly the establishment of a Marine Protected Area,” says Bocconcelli. He says that this type of protection is warranted since the Mediterranean sperm whales are considered a genetically distinct population and are listed as Endangered on the IUCN Red List.

Salierno will accompany Bocconcelli on the cruise, and wonders if perhaps Fury will make a surprise appearance. He believes he spotted the whale in November, 2020 in an area near where he and Isgrò first encountered Fury—more than four months after Fury first disappeared.

“I really hope to one day free Fury, and that we find a way to live and swim together in the sea,” he says. “It will be beautiful!”