For Greg Skomal, when a great white shark returns to the waters off Cape Cod, it’s like seeing an old friend.
On Monday, Skomal, a senior biologist with the state Division of Marine Fisheries, and researchers from the Atlantic White Shark Conservancy retagged a 13-foot female great white shark that is familiar to the area.
Named Avery, the shark was first spotted in June of last year. Skomal and researchers tagged her in September with a temporary transmitter that provided valuable information about the shark’s recent activity.
With that “pop-up” transmitter’s mission complete, Monday’s encounter was an opportunity to attach a different tag that will send researchers more detailed information about Avery’s visits to the area.
Avery returned to Chatham this week, swimming as close as a quarter-mile from the beach near Monomoy Island. Skomal was able to attach a permanent acoustic tag, which emits a high-frequency sound that is picked up by receivers stationed in various locations off Cape Cod.
“These tags give us a better sense of what the shark is doing more locally,” he said. “What beaches is it hanging out at? Does it hang out at beaches at all? Does it just stay in Chatham? Does it come close to the shore during the day, or at night? Is it nearby during high tide or low tide?”
The pop-up satellite tag first placed on Avery last year was programmed to come off, and it finally dislodged last month, Skomal said.
That particular type of tag gives biologists studying the species a sense of the broad movements of the animals. It stays on the shark’s fin and collects information about what the shark is doing, how deep underwater it goes, and what the temperature is at certain depths of the ocean.
It transmits its data to a satellite when it finally detaches from the shark.
Monday’s tagging came just a couple of weeks after state researchers and members of the Atlantic White Shark Conservancy, a nonprofit group, spotted the first great white of the season swimming 200 yards off Chatham’s South Beach.
Skomal said this year’s shark season, which began June 15 for researchers, has been slow. But on Monday they spotted three sharks, including Avery.