Can swimmers and sharks coexist? Smarter maps can help



Medici’s death was the first death of a shark in Massachusetts since 1936. “We’re on our way, aren’t we?” says Doyle. “It’s been three bites in 14 months.” After the fear of a rowing friend, Doyle coexisted Cape Cod Ocean community, a group that eventually became a non-profit organization dedicated to increasing public safety. The group helped connect pilots with lifeguards to warn them of possible sharks. She raised funds for drones and giant car-sized balloons with high-resolution cameras that could spot sharks, and advocated for devices like Smart buoy, a sea surveillance and alert system that detects large marine life in the water.

But six months study commissioned by the cities of Outer Cape and released in October 2019, it looked at the effectiveness of more than two dozen shark mitigation strategies, including smart buoys, as well as nets, virtual barriers, shark deterrent electromagnet devices and drones. The report eventually concluded that most either do not have enough evidence that they actually worked, have limited efficiency, or will not work on the Cape Cod coast – except for one: modifying human behavior.

It was the primary way public safety officials have mitigated the risk of sharks over the past eight to nine years, said Suzanne Grout Thomas, director of utilities for Wellfleet, a fishing village about 25 kilometers from the top of Cape Cod. Since Medici’s death, cities have tightened their protocols, limiting how many people can swim further and closing beaches for swimming sometimes several times a day. Rescuers and even some citizens are trained to “stop the bleeding“Bite practices, while signs warn of the presence of sharks. “Our biggest contribution to this is educating the general public about how sharks can be expected to behave,” says Thomas. And she’s already seeing signs that she’s doing it. People swim closer to shore or don’t swim at all and react faster when lifeguards whistle into whistles to clear the water.

Last summer Wellfleet had two buoys that sent a signal to rescuers. If the tagged shark is found at 200 meters, they could invite swimmers out of the water. “Last summer, there were hundreds and hundreds of sharks pinging those buoys,” Thomas says. Her goal is to have one on each beach.

But this approach, she admits, has its limitations. Not every great white shark is tagged, and the mobile network service on the beaches of the Outer Cape is still spotted at best, meaning any live notification system is hard to share widely.

While researchers and residents consider the best mitigation strategies, one strategy – selection – has remained out of the table. That is the approach some countries tried. Western Australia, on the one hand, implemented a regional policy in 2012 to monitor, capture and destroy sharks that posed an “immediate threat” to beach visitors. According to File for international shark attack, global database, shark attacks in western Australia are on a downward trend, but have risen again in recent years. Although impact assessment is difficult, many experts say they are projects of rejection they do not work.

Now technological advances and a growing understanding of animal intelligence are giving researchers hope that there could be another management option on the table, one that seeks to understand rather than modify shark behavior.

The ocean floor The cape is an immeasurable patch of sandstone, shallows and deep trenches. Sharks have learned how to navigate this underwater maze. They now hunt in what some call a “trough,” a deep water area that forms like the letter C between the outer sand bar and the beach. Because seals are often found in these shallow waters near the shore, sharks have learned how to attack sideways, rather than ambush from below. In fact, unlike other parts of the world, sharks on Cape Cod spend approximately half of their time in 15-foot shallow water, according to a recent study which analyzed data collected on eight brilliant whites.


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