PROVIDENCE —Guess they heard it was Shark Week.
Four new great white sharks were detected swimming off Block Island recently, “pinging” the acoustic receivers placed around the island, the Atlantic Shark Institute announced Monday.
These newcomers have raised the total to 14 different great whites detected off Block Island since the Institute began studying their travels in Rhode Island waters in 2019, said institute executive director Jon Dodd.
However, these sharks are just day-trippers, not summer residents on Block Island. Dodd said that the research is showing that Block Island is merely along the sharks’ migration route from Long Island to the seal-hunting grounds of Cape Cod.
“The significant difference between Cape Cod and Block Island is that the Cape has thousands of seals, and Block Island lacks that. That’s the singular reason the sharks don’t spend time cruising Block Island,” Dodd said Monday. “Once they find a food source, they know how to go to the Cape. They have to be smart to survive, to stay healthy and continue to grow, and there’s no reason to stick around for a food source that doesn’t exist.”
Still, the 14 sharks detected so far are a sign that many others are going unseen, Dodd said. “Less than 5 percent of great whites are tagged, so that’s almost certainly a small fraction of what’s coming through,” Dodd said.
The four who swam through Rhode Island recently included a 12-foot female who had been tagged in Cape Cod in 2019 and an 11-foot female tagged in Canada this year.
Their presence is being detected on nine acoustic receivers placed around Block Island that can pick up tagged sharks within 1,000 yards. Fewer than 300 great whites in the northwest Atlantic have been tagged with this particular technology; each wears a tag with a unique code that tells researchers the size, gender, and date the shark was tagged.
None of the 14 sharks have been detected here before, but Dodd said the reasons may have more to do with the sharks’ vast migration route and the small area that the few acoustic receivers cover. “They detect a thousand yards. On land, that’s a lot, but in the ocean, we’re covering a very small percentage of the topography,” he said.
The more receivers they deploy, the more sharks they tag, Dodd said, the more they’ll learn about the great predators who are among us.
Even if they don’t stick around.
Dodd is speaking about tracking great whites around Block Island at the Block Island Maritime Institute on Aug. 10 from 7 to 8 p.m.