Bill Greene/Globe Staff

Janilga Alves filleted halibut at North Coast Seafoods in Boston, one of the region’s biggest seafood suppliers. Several well-known restaurants blame North Coast for promising one kind of fish but delivering another after DNA testing revealed the restaurants were serving less expensive species than advertised. North Coast, however, said all the restaurants got the fish listed on delivery invoices. Janilga Alves filleted halibut at North Coast Seafoods in Boston, one of the region’s biggest seafood suppliers. Several well-known restaurants blame North Coast for promising one kind of fish but delivering another after DNA testing revealed the restaurants were serving less expensive species than advertised. North Coast, however, said all the restaurants got the fish listed on delivery invoices.

Bill Greene/Globe Staff

Norm Stavis, president of North Coast, sampled a fresh oyster during a tour of his fish processing business. Stavis said the company can’t control how restaurants label seafood it delivers, but added that the vast majority don’t misrepresent what they sell.

Brian Feulner for The Boston Globe

At The Union Oyster House, the country’s oldest restaurant, fish labeled as freshly-caught New England cod was actually Pacific cod, which is usually much cheaper -- and to many palates, less tasty. Union Oyster House operators said they ordered Atlantic cod from the supplier.

The Boston Globe

Line cook Charles Ferreira prepared fish and chips at the Union Oyster House. Restaurant operators said they thought they were serving fresh Atlantic cod, but DNA tests showed it to be Pacific cod, a species that typically sells for $4 less a pound.

Bill Greene/Globe Staff

Paddy’s Pub in Newton switched to North Coast several years ago after the company offered a cheaper price on haddock than its old supplier. But DNA testing on a fish sample revealed it was Pacific cod. Paddy’s owners claim they only order haddock and produced dozens of invoices. North Coast said the restaurant must have orderd the wrong fish on one occassion and pointed to a delivery bill that listed cod.

The Boston Globe

The Hilltop restuarant in Saugus also switched to North Coast to supply haddock after the firm pitched a cheaper price. But the haddock advertised was actually Pacific cod. North Coast officials said Hilltop knew it was getting chowderfish — a mix of cod and haddock scraps.

The Boston Globe

At-Smith&Wollensky in Boston, company officials were surprised to learn they were not serving red snapper as listed on the menu, but a lesser-valued spotted rose snapper. North Coast said invoices given to the restaurant simply said “snapper” and the firm did not misrepresent the fish it was selling. But there are dozens of varieties of snapper and the restaurant chain said it agreed to specifically buy red snapper.

Debee Tlumacki for the Boston Globe

At East Bay Grille in Plymouth, Pacific cod was misrepresented as grouper. Restaurant operators blamed the supplier, but North Coast officials said it’s nearly impossible to mistake cod for grouper and the invoices listed grouper.