Cape Cod shark detections rising as researchers tag more: 118 great whites detected last year
By RICK SOBEY | rick.sobey@bostonherald.com | Boston Herald
PUBLISHED: May 31, 2021 | UPDATED: June 2, 2021
The total number of great white sharks detected along the Cape has ballooned over the last few years as researchers continue to tag more of the apex predators each summer season.
Going back to 2013, there were only 11 individual sharks detected by the Atlantic White Shark Conservancy off the Massachusetts coast, according to archived data from its new white shark logbook.
Then jumping ahead seven years to 2020, the Atlantic White Shark Conservancy detected 118 individual sharks last year.
The total number of recorded shark detections has also climbed at a similar pace during the last decade. There were only 10,803 detections recorded in 2013, compared to 134,631 detections last year.
Only three acoustic receivers were deployed in 2010, while researchers deployed 65 receivers last year.
“It’s important to remember that the receivers can only detect sharks tagged with acoustic transmitters, and there are still a lot of white sharks out there that haven’t been tagged,” said Megan Winton, research scientist with the Atlantic White Shark Conservancy.
“As scientists, we use the data collected from tagged sharks to give us an idea of what the population is doing as a whole,” she added. “People should think of the data provided by the Logbook the same way — as a proxy for shark activity off the coast.”
Overall, 231 individual great white sharks have been tagged with acoustic transmitters — “think of it like an EZpass for sharks,” Winton said — by the Massachusetts Division of Marine Fisheries since 2010.
However, the local researchers have documented more than 500 white sharks from underwater video footage, Winton said.
“Many sharks come back year after year, but not all of them use our waters the same way,” she said.
The average length of the 231 tagged sharks is 11.6 feet, and the female shark to male shark ratio is 1.3 to 1.
The acoustic receivers are deployed all along the Outer Cape, Cape Cod Bay, South Shore and even a couple receivers off the southern New Hampshire coast.
“When you look at the detection data, there are two immediately clear takeaways: White shark activity is highest along Cape Cod, and the Outer Cape in particular, where seal densities are highest, and white sharks have been detected all along the coast of Massachusetts,” Winton said. “They don’t occur exclusively off of Cape Cod.”
The top two spots where sharks were detected last year was Chatham Harbor Inlet South — where 91 individual sharks were detected for a total of 10,700 detections — and Truro, with 65 individual sharks and 9,024 total detections.
The most shark detections last year were in August (55,954 detections), followed by September (27,453), October (21,006), July (16,412), November (11,818), and June (1,485).
The most detections have been in August during the last four years. Before then in 2016, the most detections were in September. In 2013, the most detections were during July.
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