Ultrasonic Antifouling Devices Found Damaging to Whales

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Research off the coast of Mexico’s Guadalupe Island in the Pacific Ocean has revealed ultrasonic antifouling (UA) devices as a new form of noise pollution that threatens the habitats of whales and possibly other marine mammals.

Acoustic ecologist Jennifer Trickey of the University of California San Diego’s Scripps Institution of Oceanography has been leading a long-term acoustic study of Cuvier’s beaked whales in the Guadalupe Island Biosphere Reserve with the aid of a seafloor-mounted acoustic recorder.

The researchers chose to study Cuvier’s beaked whales at Guadalupe Island, about 150 miles west of Mexico’s Baja peninsula, because they appeared to be non-migratory, year-round residents of the area.

“When we first went back to recover the first year of data, I came across that antifouling signal right away. At first, I was completely baffled. I thought the instrument had failed,” said Trickey, a member of the Scripps Acoustic Ecology Lab. But after further analysis she realized the signal was real.

The bay along the northeast coast of Guadalupe Island where Trickey deployed her instrument is a popular white shark cage-diving destination. She and her team quickly suspected some of the cage-diving boats as the signal’s source.

“It took some sleuthing to figure out what that sound actually was because none of us had even heard of an ultrasonic antifouling device. I had no idea that even existed,” Trickey said of the devices, which help keep hulls free of algae, barnacles, and other marine organisms through pressure and vibration.

“They’ve been around for probably close to a decade now and most people who work with marine mammal bioacoustics had also never heard of these devices. Now they’re pervasive,” said Trickey.  The devices also use the same frequency band that marine mammals use to communicate, find prey, and navigate their environment.

The COVID-19 pandemic created logistical hassles for the research team. But it also resulted in a year of data taken during a normal tourism season with the antifouling signal present and one year without. The data showed a sharp decline in acoustic presence of the whales that coincided perfectly with visits from cage-diving boats equipped with UA systems.

“COVID-19 closed the island to tourism. The shark boats weren’t there,” Trickey said, and the acoustic presence of the whales returned. “That was the proof. It turns out that the decline in the acoustic presence of the whales wasn’t some natural seasonal pattern. It was due to that antifouling signal.”

The UA devices have a negative effect, Trickey said, but there are places where they could be used with minimal habitat impact, “but marine sanctuaries and protected areas are biologically rich, productive habitats. Those are what we’re trying to protect.”

Cuvier’s beaked whales are relatively unknown among scientists and the general public alike.

“Usually, when you think of a whale, you think of something like a humpback or blue whale, something that's very obvious and very showy at the surface,” Trickey said. “But beaked whales do not follow that theme. They spend most of their lives down at depth. And they’re also not very conspicuous at the surface, so they’re easy to miss.”

Trickey and seven co-authors recently detailed their acoustic findings, collected from November 2018 to October 2020, in the journal Communications Biology. The co-authors include Gustavo Cárdenas-Hinojosa, a marine mammal researcher at Mexico’s National Commission of Natural Protected Areas (CONANP).

“The findings of our paper were published with perfect timing: the update of the management plan of the Biosphere Reserve of Guadalupe Island is ongoing,” Cárdenas-Hinojosa said. “Our findings were included as justification to propose regulations to ban the use of ultrasonic antifouling systems by vessels to avoid disturbance of the population of Cuvier’s beaked whales off Guadalupe Island.”

The UA systems have become widespread globally on various types of ships.

“Cruise ships, in particular, seem to be using this technology heavily and it’s completely unregulated,” Trickey said. “We’ve now shown that it can be a problem to marine life, so how do we go about managing them better?”

Manufacturers have touted these devices as eco-friendly alternatives to antifouling paints, which contain toxic chemicals.

“We hope our findings will help raise awareness about the sensitivity of Cuvier’s beaked whales, and possibly other marine fauna, regarding the negative impact of UA systems on species—which rely on acoustics to survive their world—in other marine protected areas around the world,” Cárdenas-Hinojosa said.

Trickey stressed that only one of the cage-diving operators at Guadalupe Island uses the UA system. The Communications Biology paper lists the company’s name. Also named are several cruise ships that have been detected using UA systems.

“My message would be to do your homework before you sign up for a cruise or a cage-diving trip or an ecotourism trip of some kind,” Trickey said. “Be careful who you choose as the operator when you do these activities.”

Co-authors of the study also included Lorenzo Rojas-Bracho of Mexico’s National Commission of Natural Protected Areas (CONANP); Gregory Schorr and Brenda Rone of Marine Ecology and Telemetry Research; and Eva Hidalgo-Pla, Ally Rice, and Simone Baumann-Pickering of Scripps Oceanography. Funding was provided by the Marisla Foundation, the Office of Naval Research, the PADI Foundation, and CONANP.