Tracking great white sharks off Cape Cod could help protect beachgoers
Shark experts are once again gearing up to hit the waters off Cape Cod in the coming weeks to continue their research on the presence of great white sharks.
But this season, researchers aren’t merely focusing on the number of apex predators returning to the region; they’re also trying to better understand the hunting and feeding habits of the marine animals, an intensive effort that comes the summer after one man was attacked, and another killed, while in the water near the coastline.
“If we can understand the nature of how [feeding] happens, we can try to prevent people being confused for prey items,” said Greg Skomal, senior fisheries scientist with the state Division of Marine Fisheries.
For the last five years, Skomal and state officials have teamed up and worked closely with the nonprofit Atlantic White Shark Conservancy on a population study of the sharks locally.
The aim of the study is to capture an “accurate picture of how many sharks take up seasonal residency in the waters off Cape Cod,” according to the conservancy. The results of the study, the organization said earlier this month, are nearing completion, and are expected to be released soon.
With that portion of their work wrapping up (they’re in the “analytical phase”), Skomal and the conservancy are continuing their partnership on this “new wave of research to better understand shark behavior,” officials said this month.
“It is critical to get a better idea of hunting and feeding behavior,” said Cynthia Wigren, the conservancy’s chief executive, in a statement. “If sharks are feeding at certain times of the day or stages of the tide, for example, we can use that information to identify periods when the risk of interactions between sharks and recreational water users may be highest.”
To track this type of activity, researchers will use special tags, called “Acceleration Data Loggers,” that will be attached to the dorsal fins of great whites, Skomal told the Globe in a telephone interview this week. The tags will automatically fall off after a few days, and ping researchers as to their whereabouts so they can be retrieved and their data downloaded.
“We will be able to put these on for a couple of days and then examine the data and how many predatory attempts may have happened and when they happened — at dawn, dusk, at night, during the day,” Skomal said. “We’ll be looking for a pattern, or if it’s random.”
They can correlate those events with other factors like water temperature and tide.
Some of the devices will have cameras, providing “direct observations of the behavior” of the sharks, Skomal said.
The devices will allow researchers to get a snapshot of the “fine-scale movements” of the sharks, the conservancy added.
“Data will be used to estimate feeding frequency; identify environmental conditions that relate to feeding; and will be combined with population estimates,” said Megan Winton, a staff scientist with the conservancy, in a recent statement.
Other facets of the upcoming work could include examining how the topography of a specific area where a shark feeds influences behavior. Skomal hopes this “habitat mapping” will be done in partnership with the Provincetown-based Center of Coastal Studies or US Geological Survey — or both.
“If seals are close to shore and sharks are trying to get in close to shore, how do they use channels and sand bar systems? Are there areas that are more conducive to that than others?” Skomal said. “Last year, the incidents that happened were not far from the shoreline, so how did the sharks get there? Are they using underwater channels; is it tidally dependent? We are interested in that.”
Skomal said his work with the conservancy will also expand into Cape Cod Bay this year, following frequent reports last year of sharks snagging fish caught by passengers on charter boats. Experts in the past had been mostly focused on shark activity on the outer Cape.
“We don’t believe it’s a separate population,” Skomal said. “We just want to look at the connectivity between the Bay and the outer Cape.”
All of this, Skomal said, will be done with the goal of ensuring and enhancing public safety in mind.
“We believe — and the scientific community believes — that the better we understand the relationship between sharks and seals, the better we can provide information to beach managers and public safety officials on trying to prevent incidents like those that occurred last year,” he said.