The once-thriving New England gray seal population was decimated by the mid-20th century because of hunting, with Massachusetts keeping a seal bounty on the books until the 1960s. But scientists say conservation efforts, an abundance of food and migration from Canada combined to revive the population.

Environmentalists cheer the resurgence, saying the gray seal boost is good for biodiversity and a boon for popular seal watch tours in coastal New England. But many fishermen say the seals interfere with fishing charters and steal catch. Beachgoers bemoan the 600-plus-pound seals taking over large stretches of shore, befouling beaches and attracting sharks, which feed on seals.

Some residents of Nantucket are so fed up over the huge seal population that now calls the affluent island home that they have suggested a controlled hunt, similar to the way states manage deer.

Nantucket resident and recreational fisherman Peter Krogh, whose Seal Abatement Coalition has collected 2,000 signatures asking federal officials to amend laws that prevent dispersion of gray seals, said gray seals are a threat to fishing and tourism on the island.

Asked if he supports a seal cull, Krogh said “all options” should be on the table for managing the population.

“This is a real threat to the traditional way of life on this island,” Krogh said.

Conservationists scoff at the idea of providing amendments to the Marine Mammal Protection Act, which protects seals. They say culling the herd would undo the results of the act, which allowed the species to recover in New England.

The seals’ burgeoning population is a blessing for at least one industry.

Business is booming for Keith Lincoln, who operates a seal watch ferry to Monomoy Island off Cape Cod. Seal sightings have skyrocketed from about 50 per trip in 1989 to about 2,000 per trip now, he said. The curious seals frequently come close to the boats, a thrill for gawking tourists, he said.

“Once the word spread out, the word spread quick,” Lincoln said. “The cuteness of them is what draws everybody.”

Some also believe the seals’ negative impact on fishing is overstated. Brian Sharp, the manager of marine mammal rescue for the Cape Cod-based International Fund for Animal Welfare, said gray seals feed mostly on fish species of little commercial value, like sand lance.

Others in the commercial fishing industry don’t see seals as a threat. Lobstermen off Rockland, Maine, where gray seals are often spotted, say the seals and fishery coexist with little strife.

“Culls of gray seals have not been shown to increase fish populations. It’s not that simple,” Sharp said. “What we’re seeing is a normal growth curve of seals repopulating an area.”

The gray seals, also called horsehead seals, can grow to more than 10 feet long and inhabit both sides of the North Atlantic Ocean. They are sometimes found in the same areas as their smaller cousins, harbor seals.

Encounters with humans frequently don’t end well for the seals, Sharp said. They sometimes become entangled in fishing gear, and six of them were illegally shot and killed on the southern ridge of Cape Cod in 2011, he said.

For now, the seal population is flourishing, and its ability to sustain seal watch businesses off Massachusetts and Maine is evidence that it can have an economic benefit, said Gordon Waring, fishery research biologist at the Northeast Fisheries Science Center in Woods Hole, Massachusetts.

“Seals are just another large marine predator, and they are part of the diversity of the marine environment,” he said. “And they are able to thrive and recover.”