American restaurants serving shark are feeding an international demand to hunt them, said opponents of the practice. Several eateries in Boston’s Chinatown neighborhood, as well as in East Falmouth and Quincy, serve shark fin, according to the Animal Welfare Institute.

Both federal and state law prohibit the practice of slicing off a shark’s fins, known as “shark finning,” but a market still exists for them in the United States, where a bowl of shark fin soup can sell for more than $100, according to animal welfare groups.

Governor Deval Patrick will sign a bill Thursday banning the possession and sale of shark fins in the state, officials announced Wednesday. The bill, approved in the State House this month, would make Massachusetts the ninth state to pass legislation criminalizing the shark fin trade.


The sharks are usually alive when the fins are cut off, said Laura Hagen, deputy director of advocacy for MSPCA-Angell. Poachers throw the shark back into the water because the meat in the rest of the body is worth only a fraction of the fin. Unable to swim, the sharks suffer slow deaths.

Ninety percent of fins sold in the United States come from Hong Kong, where fins originating from about 80 countries are brought to be bleached and cleaned before being shipped out again, said Meghan Jeans, director of conservation at the New England Aquarium.

The sharks are usually hunted in countries with lax or nonexistent finning laws, she said.

In China and other parts of East Asia, shark fin, usually served in soup, is a delicacy, Hagen said. Poachers will hunt any of the more than 400 species of sharks that roam the ocean, which means that some of those that are endangered, such as the scalloped hammerhead , can end up in American restaurants, she said.


This month the scalloped hammerhead, which is prized both for its fin and meat, became the first shark species protected by federal conservation law.

Because sharks have low birthrates, higher rates of hunting in recent years have caused the population to decline rapidly, Hagen said. According to a study published last year in the Marine Policy journal, about 100 million sharks are killed annually, though the number can range from 63 million to 273 million.

A small shark population could spell disaster for the entire marine ecosystem, Jeans said.

“They’re top predators,” she said. “With their decreasing number, it has cascading effects in the ecosystem.”

In a statement, Patrick hailed the initiative.

“With the passing of this law, Massachusetts builds upon its long history of animal protection and environmental stewardship,” he said.

A coalition of ocean conservation and animal welfare groups, including MSPCA-Angell, the Aquarium, The Humane Society of the United States, and Fin Free Massachusetts, had been lobbying to pass the bill, which imposes on violators a fine between $500 and $1,000, as well as up to 60 days in jail.

State Senator Jason M. Lewis, Democrat of Winchester, spearheaded the effort.

Perhaps the bill’s most notable proponent is 9-year-old Sean Lesniak of Lowell. Sean became interested in sharks watching the Discovery Channel, a habit he started when he was 3 years old, his father, Jeff, said.

Last summer, a documentary on the declining shark population inspired Sean to write a letter to state Representative David M. Nangle, Democrat of Lowell, asking him to introduce a bill banning finning.


“Sean said ‘What can I do about that?’ ” Lesniak said. “I told him you put your name on it and work toward something you believe in.”

And that he did. A few weeks after penning the letter, Sean was invited by Nangle to speak in front of 400 people at a House Judiciary Committee hearing, where he explained the importance of saving sharks.

When the House approved the legislation months later, in May, Sean, who made his father take him to several hearings at the State House, received another standing ovation. He hopes to become a marine biologist one day, his father said.

“He’ll say things that I won’t even know,” Lesniak said. “It’s very interesting to him. Book after book about sharks.”

Oliver Ortega can be reached at oliver.ortega@globe.com. Follow him on Twitter @ByOliverOrtega.