PROVINCETOWN — As the waters off Outer Cape Cod warm and beaches fill, John Chisholm, the man working the virtual tip line at Sharktivity, knows his workload is about to go up.

The Atlantic White Shark Conservancy (AWSC), a Chatham-based nonprofit that sponsors scientific research and public education about white sharks, launched the popular shark-tracking app in 2016 with the idea that it would get the public involved in its research and spur interest in the species’ return to its historic range — a conservation success story, even though it’s one that makes humans instinctively uncomfortable. The sharks have been protected by federal law since the 1990s.

One thing Sharktivity isn’t: a real-time safety tool. Since great white sharks are so widespread, it’s very hard to estimate their numbers, according to the International Fund for Animal Welfare. Some estimates put the global population at just a few thousand, while other studies put the number at twice that or more.

According to a paper by AWSC scientist Megan Winton published last year in Marine Ecology Progress Series, some 800 Atlantic white sharks visited the waters off Cape Cod from 2015 to 2018. The conservancy has tagged about 300 in eight years. In the past week, the app has had 10 sightings, predations, or “pings” from across the world.

It has become the second most popular shark-tracking app out there, with over 1.2 million downloads and about 9,000 current daily users, according to data on Apple’s app store. That’s rare for something with a regional focus, said Virgil Zetterlind, the co-founder of Conserve.io, the Florida-based software company that developed the application.

What you see when you open Sharktivity on your phone is a map dotted with icons that denote white sharks or suspected white shark activity. Click on an icon and you may see a photo of a dead seal, an aerial view of a white shark taken from a tour plane, or a short description of a sighting. The app also alerts the public about beach closures.

Sharktivity depends, in part, on crowdsourcing: people report sightings through its tip line. AWSC does not collect information on app users’ locations, but the highest number of tips come from Cape Cod. And, once submitted, all tips end up on Chisholm’s desk at the New England Aquarium.

The Other Side of the Tip Line

Even with white shark numbers increasing, most sightings submitted to Sharktivity are not actually white sharks, according to Chisholm.

Chisholm, who has been vetting shark sightings since the late 1970s, told the Independent that all sorts of animals are mistakenly identified as white sharks, including ocean sunfish, sturgeon, and even seals. Other species of sharks, including basking, mako, brown, and tiger sharks, also are misidentified in tips. (Sharktivity exclusively monitors white sharks.)

Chisholm says the best tips include a photo of either a white shark, which he can identify by the dorsal fin, or a predation photo — usually a dead seal. He scrutinizes those images to see if the bite marks on the seal match a white shark’s tooth pattern.

“I’ve been doing this for a long time, longer than anybody,” he said. “And white sharks leave very distinct bite marks.”

Sometimes, breaking the news that the terrifying shadow someone saw in the water was not actually a white shark can be the hardest part of the job. “People just get so disappointed, because everyone wants to see a white shark,” Chisholm said.

Blurry photos or vague descriptions that cannot be validated are logged as “unconfirmed shark sightings.”

Chisholm said that he also received the occasional prank sighting, including dogs and humans in shark costumes.

“What they don’t realize is when they send me their information, I get their location and contact info,” said Chisholm.

Tech and Tags

It took Zetterlind’s team only a few months to build Sharktivity because the company had already designed a similar app called Whale Alert.

But they’re adapting its features to the needs of shark scientists — and to the demands of big tech: Zetterlind said that Sharktivity has to be updated two to four times per year. Otherwise, it will become obsolete and be taken off the Apple and Google app stores.

That kind of maintenance is not cheap. Zetterlind would not say how much it costs to run Sharktivity each year, but he said organizations typically commit $50,000 to $100,000 per year to run something like it.

Zetterlind said that his team had to design the app to handle extreme waves of traffic. For example, when a beach closure is announced, Zetterlind said the app can be opened over 10,000 times in just a few minutes.

Winton said that the app’s data are constantly being updated by AWSC scientists spotting sharks on research trips and through its tagging system.

Winton said AWSC has about 100 acoustic receivers in the waters off Cape Cod. Those receivers, which are housed in yellow buoys, record the time and location of any shark tagged with a transmitter swimming by.

The AWSC team doesn’t catch sharks. They’re tagged from boats while they’re swimming. But they do work with a charter fisherman in Hilton Head, S.C. who has found a way to consistently and safely catch white sharks and tag them with fin-mounted satellite tags.

When a shark with a fin-mounted tag breaches the surface, the device sends out a signal, allowing AWSC scientists to chart the shark’s path as it swims — even for hundreds of miles.

LeeBeth is perhaps the most famous shark on the app. A 14-foot female tagged last December, she made history as she swam farther into the Gulf of Mexico than any other shark the app’s fans could follow. According to her swim path log, LeeBeth was in the waters off Cape Cod in mid-June before heading north.

LeeBeth is swimming off the northern coast of Prince Edward Island, according to the latest ping recorded on July 3.

Skeptical Surfers

Several Outer Cape surfers who spend significant time in the water told the Independent they had mixed feelings about Sharktivity.

Florian Perrelt has been surfing on the Outer Cape for six years. When he started, he said he used to check the Sharktivity app but hasn’t downloaded it again after getting a new phone.

Rather than constantly checking the app for the small fraction of white sharks it tracks, Perrelt said, he has come to accept the fact that sharks are always present in the water.
“It’s a point of anxiety more than something useful,” he said.

Sara Moran, who has been surfing Outer Cape waves for 10 years, said she also has had Sharktivity on her phone “off and on” but generally elects to follow lifeguard advice about whether to go in at a specific beach or not.

“Surfers don’t really use it,” said Olaf Valli, the owner of Sickday surf shop in Wellfleet.

On the AWSC website, a disclaimer reads: “This app does not contain or constitute and should not be interpreted as advice as to what beaches or parts of water are safe. The only way to completely rule out a close encounter with a shark is to stay on shore.”

The app is “a good way for people to get a feeling for peak activity periods off the coast of Cape Cod,” said Winton. “We know we’re never going to go out and tag every shark in the population.”