The growing shark population off the coast of Massachusetts has one researcher losing sleep.

Cape Cod experienced two separate shark attacks last year that left one man injured and a second man dead, marking the state’s first fatal shark attack since 1936.

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"I've seen what they do to people. That bothers me," Dr. Greg Skomal told Boston station WCVB-TV. "I'd be lying if I said I didn't lose sleep over this. I do and I've had nightmares about it."

The number of shark sightings have jumped 67 percent from 2017 to 2018, the station reported.

Skomal and other shark experts told the station via email that the rise in sharks is due to the growing seal population. Seals are estimated to number at least 50,000 along Cape Cod, making it a sufficient feasting ground for the sharks.

If the seal population goes unmanaged, some residents worry that it could lead to “more deaths,” surfer John Kartsounis told the station.

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Researchers weren’t expected to deliver a plan that deals with the shark problem until September, according to the station. Until then, experts are urging caution.

"As long as people are willing to take the risk and go out into deep water where these sharks are hunting, the probability of additional attacks is quite high," Skomal told WCVB.