CHATHAM, Mass. -- Ted Ligenza, a fisherman here for nearly 40 years, was intrigued when he first started seeing gray seals bobbing in the harbor for the very first time about three decades ago. "We thought they were kind of pretty looking," he said.
He did not know then that the sweet-faced creatures would eventually become a Cape Cod ubiquity like the harbor-side clam shack, mountainous hydrangea and sightings of Kennedys. These days, they emerge by the thousands on sandbars or pop up in small groups along the shoreline. They delight visitors who watch their heads bob above the waves. But they invade fishermen's nets, draw sharks closer to the shore and are rankling those who make their living by the sea so much that some are calling for blood.
"I guarantee those seals have caught a hell of a lot more cod than the port of Chatham has," said John Our, a fisherman who, like others, thinks it is time to consider controlling the population. "Think about it -- we cull everything else," he said. "You have harvests of deer, farmers get to kill the locusts."
The return of the gray seals to Cape Cod is a dramatic success story for animal protection. Before the early 1980s, gray seals were mostly absent from North American waters, their numbers low in part because of the bounties in Massachusetts and Maine that researchers estimate killed up to 135,000 before the last was lifted in 1962. Ten years later, the federal Marine Mammal Protection Act outlawed seal hunting. With new protections also in place in Canada, the gray seal population slowly began to grow and thrive in Maine and on Cape Cod's sandbars and long stretches of protected beach, where they face few predators.
A survey in 1994 spotted 2,035 seals in Cape Cod waters. In 2011, surveyors counted more than 15,700, according to the National Marine Fisheries Service. Some scientists suggest the number of gray seals in United States waters may now be at its highest point in history.
Local businesses have capitalized, offering seal tours, while the National Park Service has posted volunteers meant to educate the public about the hundreds of seals they can see from parts of the National Seashore on the Cape's eastern edge, thrilling tourists like Jen Mitchell, a computer programmer from Worcester, Mass., who used her phone to take a picture of hundreds of seals on a sandbar in Truro one afternoon this summer.
"I've been coming here for decades, and I've never seen this many," she said while the seals howled, almost mournfully. "Wonderful!"
But many fishermen here wonder if the price of seal protection may be their own extinction. One gray morning this summer, Ernie Eldredge pulled up a small boat alongside his fishing weir, a huge, bowl-shaped net strung between wooden posts that jut out of the water here like crooked teeth. A gray seal bobbed inside, its wide eyes belying its intruder status, while Mr. Eldredge's daughter, Shannon, examined part of the net that had been shredded by seal claws.
"They drive the fish away from the weir before they even have a chance to go in," said Mr. Eldredge, who extracted a measly catch of several dozen menhaden and squid that day, a far cry from the 30,000 pounds of fish he once caught daily. "We can't catch anything because of the seals."
Mr. Eldredge and many of his colleagues acknowledge the role overfishing and environmental change have played in the paucity of fish in the Gulf of Maine, but they say seals have prevented fish stocks from rebounding even as stiff new quotas are imposed on the fishermen's activities. Seals eat up to 6 percent of their body weight each day -- which, for an 800-pound male, could be about 50 pounds of food, including prized fish like cod and flounder.
"It's devastating," said Tom Smith, who has been gill netting bluefish out of Provincetown and Hyannisport since 1981. "They're eating our fish we're trying to catch, they're eating them out of the nets."
Rick Thompson, a seafood distributor who works on Chatham's fish pier, is among many here who would like to see a return of the bounties, or at least of some kind of controlled harvest.
"I'm not a murderous kind of guy or whatever," he said. "It's not going to be done in front of the harbor or whatever. You're going to go out in open water and try to get them."
Many researchers contend that seals have not invaded, but are a natural part of the ecosystem that humans have not had a chance to understand fully.
"Gray seals have literally been absent from the Gulf of Maine for the entirety of modern ecology," said Dave Johnston, a research scientist at Duke University, who worked this summer with a team to tag gray seals in Cape Cod. "Since they've been absent for so long, they're also absent from the memory of the people here. It's a really hard thing to communicate to people who have spent their whole lives in a place and know it really well."
Gray seals' federally protected status means an act of Congress would be required for any seal harvest. "You have a better chance of running over a busload of children than clubbing or shooting a seal, let's be realistic," Mr. Our said.
That does not mean seals are never killed. In 2011, about half a dozen seals were shot in the head, their bodies found bloodied on Cape Cod beaches. But illegal hunting is rare and, apparently, difficult.
"I know guys that have shot at them," Mr. Our said. "If you shoot at them, they'll never come back. They're not stupid. "
This article originally appeared in The New York Times.