The tag is one of about a dozen transmitters that are still sending data to the foundation, executive director Greg Jacoski said. The tags are used to research the sharks’ migration patterns and are worth about $4,000 each, Jacoski said.

The satellite tag had been placed in May on the dorsal fin of a 6-foot mako shark, which was tagged near Ocean City, Md., the Guy Harvey Ocean Foundation said. But since mid-August, the device has been sending signals exclusively from a North Falmouth neighborhood near New Silver Beach.

Commercial fishermen off Cape Cod may have caught a shark this month that was carrying an expensive piece of tracking technology, and a nonprofit organization is offering a $1,000 reward for the equipment’s return.


A satellite tag. Guy Harvey Ocean Foundation

“We’re pretty confident it’s with the fishermen,” Jacoski said. “We get reports of where the tags are reporting from, and they’re accurate to within a couple hundred yards.”

The tags are seldom found and seldom returned, Jacoski said.

“We do our best to get the tags back when we can,” Jacoski said. “We offer a reward just because these tags are so expensive. It’s more cost-effective to get an old tag back, refurbish it, download the information it has collected, and send it back out.”

About 30 percent of the tagged makos are caught by commercial fisherman, Jacoski said.

“That’s one of the issues facing makos right now; they’re tasty,” Jacoski said. “So it is legal to fish them, and there is a market for them.”

Fishing makos requires a special permit from the National Oceanic and Atmospheric Association, the foundation said.

Contact information for the foundation is on the tag.

Dylan McGuinness can be reached at dylan.mcguinness@globe.com. Follow him on Twitter at @DylMcGuinness.