A year after a Globe investigation found restaurants and stores across Massachusetts were routinely selling cheaper, lower-quality fish than they promised customers, a new round of DNA testing shows the vast majority are still mislabeling seafood.

Ken’s Steak House in Framingham again served Pacific cod instead of a more expensive Atlantic species. Slices of fish sold as white tuna at Sea To You Sushi in Brookline were again actually escolar, an oily species nicknamed the “ex-lax’’ fish by some in the industry because it can cause digestion problems. H Mart, an Asian supermarket chain found to have sold mislabeled red snapper last year, this time was selling inexpensive freshwater Nile perch as pricier ocean grouper at its Burlington store.

The results underscore an ongoing lack of regulation in the nation’s seafood trade — oversight so weak restaurants and suppliers know they will not face punishment for mislabeling fish. Over the past several months, the Globe collected 76 seafood samples from 58 of the restaurants and markets that sold mislabeled fish last year. DNA testing on those samples found 76 percent of them weren’t what was advertised.

Advertisement - Continue Reading Below

Some restaurant operators who repeatedly mislabeled fish blamed suppliers. Others said naming inconsistencies were the result of clerical errors. Several made only partial revisions to their menus. Some, like at Hearth ’n Kettle in Attleboro, corrected their menus, but waitstaff still wrongly described the fish as local. And a few said the issue was not a priority.

“We’re too busy to deal with such silliness,” Janet Cooper, of Ken’s Steak House, said after several phone interviews during which she could not explain why the restaurant was still selling far less expensive Pacific cod as locally caught fish.

After the Globe’s “Fishy Business” series last fall, state and federal lawmakers pledged quick action to strengthen oversight of the seafood industry. US Representative Ed Markey, Democrat of Malden, filed a bill in July to require traceability of fish from the boat to the dinner plate, but the legislation hasn’t moved out of House subcommittees.

Elsewhere, little progress has been made to protect consumers from paying too much for inferior fish. The Food and Drug Administration, which maintains a list of acceptable market names for fish species, has historically focused efforts on food safety, rather than economic fraud such as seafood substitution. The agency recently began conducting its own DNA testing, but the results so far have provided little insight into where mislabeling occurs in the supply chain.

The Globe hired the Biodiversity Institute of Ontario at the University of Guelph to conduct DNA testing on the fish samples, as it did for the initial round of tests in 2011. The testing focused on certain species, such as red snapper and cod, because they have been identified by regulators as more likely to be substituted.

Seafood mislabeling persisted at the Sand Bar & Grille on Martha’s Vineyard, where the Globe last year found farmed hybrid bass was switched for striped bass, and tilapia was misrepresented as red snapper.

Mike Wallace, who runs the Oak Bluffs restaurant, said he talked with his sushi chef after the Globe’s initial investigation and believed the issue was resolved. But DNA testing this year showed samples of albacore and red snapper were both tilapia, one of the cheapest farmed fish on the market.

“I’m obviously disappointed,” Wallace said. “You can’t sell something that it’s not. It would be like if I was saying Angus beef on my menu and it wasn’t Angus beef. I’m now going to have to verify it myself.”

While fish mislabeling routinely costs consumers money, it involves more than economics. Such deception can cause diners to unknowingly violate dietary restrictions, eat illegally caught species, or consume chemical additives banned in the United States.

Much of the substitution occurs with imported fish, which now makes up about 91 percent of the seafood Americans consume. Disease outbreaks linked to imported fish have increased in recent years, according to the Centers for Disease Control and Prevention, making it more urgent to better regulate the supply chain.

“The public should be frustrated. How can we trust the food we eat when we can’t even trust basic information on the label or a menu?” said Beth Lowell, a campaign director with Oceana, a nonprofit in Washington, D.C., that focuses on fighting fish mislabeling.

Some restaurants responded to the Globe series last year by changing menus or buying the correct fish. Bertucci’s Italian Restaurant found a new supplier after DNA testing last year revealed the chain misrepresented hake as baby cod. Not Your Average Joe’s in Westborough, Durgin-Park in Faneuil Hall, and Stewart’s Seafood Tavern in Eastham all had properly labeled fish this year after serving the wrong seafood, according to last year’s DNA testing.

The Globe also visited some new restaurants this year and found mislabeling problems. At Symphony Sushi — selected by Boston Magazine as one of the city’s best neighborhood restaurants in 2010 — a $15.95 crispy red snapper meal turned out to be tilapia. At Boston Children’s Hospital, the fish sandwich described by a cafeteria clerk as cod tested as less-expensive pollock. Instead of “fresh Boston cod” promised on the menu, Jerry Remy’s Seaport served Pacific cod, which is often previously frozen, cheaper, and hauled thousands of miles to New England.

Symphony Sushi did not return six calls made over several weeks, and Children’s Hospital blamed a clerical error.

It’s usually a long journey from the ocean to diners’ plates, with fish making numerous stops — including processing plants, warehouses, distributors, and restaurants. That can make it difficult to determine where deception takes place.

“I’m a bit surprised,” Chris DeVoe of the Cronin Group said of the results at Jerry Remy’s Seaport. But the company would not share invoices or provide details on how the substitution may have occurred.

Following last year’s Globe story, Minado Restaurant, a popular sushi restaurant in Natick, changed the red snapper sign at its buffet to read “tilapia,” the fish it was actually serving. But “white tuna” was written next to the word “escolar” — as if the two were interchangeable. They are not. Sea to You Sushi, after being contacted by the Globe this year, added a note on its website indicating white tuna is a “nickname” for escolar.

Blue Ginger in Wellesley was a rare example where celebrity chef Ming Tsai advertised an expensive species — sablefish — as cheaper butterfish because he liked the way the name “rolls off the tongue.”

In response to the newspaper series, Tsai modified the menu to read “Sablefish (a.k.a. Butterfish).” But when the Globe visited the restaurant on several occasions this year, the reference to sablefish had been removed. After Blue Ginger was told in August of the new DNA results, the restaurant restored “Sablefish (a.k.a. Butterfish)” to the menu.

The FDA, which oversees the labeling of fish, this year conducted its own DNA testing at wholesalers and seafood processors. Haddock and cod samples collected from 25 businesses in New England all were accurately labeled, according to an agency spokeswoman.

Earlier this year, the Massachusetts Department of Public Health began distributing brochures to local health inspectors to make them aware of seafood substitution, although it is unclear how many are cracking down on the problem. In addition, the state agency is collaborating with Legal Sea Foods to launch a pilot program next year in several communities that would track fish through the supply chain to ensure its authenticity.

At Doyle’s Cafe in Jamaica Plain, previously frozen chunks of Pacific cod took the place of fresh New England cod, according to last year’s Globe testing. The same problem showed up at the landmark tavern this year. Owner Gerry Burke said he was not able to revise the menu — at a cost of $1,500 — until this fall after the Globe’s most recent testing.

“I did take it seriously,” Burke said, “even if everyone else didn’t.”