The number of unprovoked shark attacks worldwide is lower than expected for the second year in a row, say scientists. Warming ocean temperatures could be the reason.
“Climate change could very well be a factor,” said Florida Atlantic University professor Stephen Kajiura, who has been doing aerial surveys of blacktip shark migrations for the past decade.
In 2015, the number of unprovoked attacks hit a record high with Florida — as always — leading the globe in the number of times sharks bit surfers, swimmers and beachfront splashers. The worldwide total was 98, with 30 of them occurring in Florida.
But in 2018, the number of attacks worldwide dipped to 62, and last year the number was 64, according to the International Shark Attack File at the University of Florida. The number that occurred in Florida last year: 21.
Generally speaking, the two factors that fuel the number of shark attacks are the presence of a lot of sharks and the presence of a lot of people, according to Gavin Naylor, director of the Florida Museum of Natural History’s shark research program. The number of people going in the water hasn’t dropped, so there’s been a change in the sharks.
Most of the attacks in Florida are by one species, blacktip sharks, that migrate in the tens of thousands along the state’s Atlantic coast this time of year, Naylor said. There appears to be a change in the blacktips’ migration, so there aren’t as many swimming by Florida as there were in prior years.
“It could be the temperature of the water, and it could be climate change, but we can’t say definitively,” Naylor said.
In January, February and March, Kajiura zooms into the air in a Cessna to fly over the blacktips checking their numbers.
“We’ve seen a dramatic drop," he said. “Over the past 10 years we’ve seen fewer and fewer sharks out there. Their movements are tightly tied to temperature.”
That’s not because the sharks care about the warm water, he said, but because their prey’s movements are connected to it. The baitfish they like to eat spawn when the water hits a certain temperature range, but as the oceans warm, the spawning may not occur at the same time or location as before, he said.
“The whole food web is related to temperature,” he said. “As the oceans continue to warm, we will continue to see changes in their migratory pattern.”
While the the U.S. led the world in shark attacks with 41 bites, the only two fatal shark attacks occurred overseas, with one in the waters of Reunion, an island in the Indian Ocean, and one in the Bahamas.