When Greg Skomal tagged his first great white shark in 2004, shark sightings in Massachusetts waters were rare, maybe once a year at most.

“It was not uncommon to have a couple years go by and see no white sharks off the Massachusetts coast,” said Skomal, a senior researcher with the state Department of Marine Fisheries.

That’s changed. Last Monday, Skomal and his team tagged their 100th shark off the eastern coast of Cape Cod, a testament to the predators’ surging population.

“We’ve identified as many as 21 individual sharks in one day,” Skomal said. “So there’s definitely been a dramatic change.”


His team started regularly tagging sharks in 2009 as part of a “movement ecology” study, which observes their migratory patterns. In 2014, the team started another study focused on population and abundance.

That’s when Skomal began collecting data of sightings off Cape Cod. The team identified 80 sharks in 2014 and 141 in 2015. (He doesn’t tag every shark the team identifies).

Skomal credited the Marine Mammal Protection Act of 1972, a law that afforded high levels of protection to sea mammals, for the growing population. The law allowed the seal population off Massachusetts to boom, which in turn attracted their most famous predator.

Skomal wouldn’t say how many sharks the team has found in 2016, but said he and his team plan to finish the season in two or three weeks.

Skomal, who started with the Department of Marine Fisheries in 1987, said he never would have imagined how many sharks he now finds.

“I’m pleasantly surprised at the success we’ve had,” Skomal said.

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