Andrew Cummings, a charter boat captain and an oyster farmer in Wellfleet, said he believed voracious seals were depleting fish stocks.

“It’s a very, very, very serious issue,” Mr. Cummings said. “I’m not saying they should be shot, but I think there are other ways to possibly control and manage the seal population.”

When he heard about the Truro shooting last fall, he said, “My opinion was, well someone finally has had enough.”

Mr. Cummings added that the great white sharks that have been spotted off the cape might eventually help keep the seal population down, but he doubted there were enough to do so yet.

Others worry that a real-life “Jaws” episode is inevitable. Massachusetts has not had a fatal shark attack since 1936, but sightings of great whites brought about the closing of Cape Cod beaches several times last summer. A fisherman spotted the first great white of the season off Martha’s Vineyard in May, earlier than usual.

“I’m like, ‘Oh no,’ ” said Mr. Eldredge, who takes his small skiff out to watch seals. He talks to them and they listen, he said. “I love seals, but I hate the great whites.”

Harassing or injuring seals is a federal crime under the 1972 Marine Mammal Protection Act. But from the late 1800s until 1962, Massachusetts placed a bounty on seals, paying up to $5 per nose and thinning the population.