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.

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.