A diplomatic row over fish is playing out between the US and UK governments in response to provocations from Russia.

The feud could lead to an import ban on Patagonian toothfish, also known as Chilean sea bass, which US officials insist is being caught illegally near Antarctica.

Russia last year rejected toothfish catch limits proposed by the 26-member Commission on the Conservation of Antarctic Marine Living Resources.

The UK responded by issuing licenses to four British-flagged vessels to fish for the toothfish.

US officials say that move violates commission rules and it will not allow the fish to be imported.

The diplomatic feud, which has not been previously reported, intensified after the UK quietly issued the licenses off the coast of South Georgia, a remote, uninhabited UK-controlled island some 870 miles east of the Falkland Islands.

As a result, for the first time since governments banded together 40 years ago to protect marine life near the South Pole, deep-sea fishing for Chilean sea bass is proceeding this season without any catch limit from the 26-member Commission on the Conservation of Antarctic Marine Living Resources (CCAMLR).

The move essentially transformed overnight one of the world’s best-managed fisheries into a France-sized stretch of outlaw ocean — at least in the eyes of US officials threatening to bar UK imports from the area.

“In a world beset by conflict, the UK is playing a risky game,” said Will McCallum, head of oceans at Greenpeace UK.

“The history of Antarctic protection is one of peaceful co-operation for the common good of humanity. Russia’s consistent willingness to abuse the process cannot excuse unilateral action by other members. We trust that countries who have previously imported South Georgia toothfish will not accept the catch of what is now an unregulated fishery.”

For decades, the fishery near South Georgia was a poster child for international fisheries co-operation, one that brought together sometimes adversarial powers like Russia, China and the US to protect the chilly, crystal blue southern ocean from the sort of fishing free-for-all seen on the high seas.

Last year, as tensions with the West were rising over Ukraine, Russia took the unprecedented step of rejecting the toothfish catch limits proposed by CCAMLR scientists. The move was tantamount to a unilateral veto because of rules, common to many international fisheries pacts, that require all decisions to be made by unanimous agreement.

But critics say the UK’s response — issuing licenses without a CCAMLR-approved catch limit — is unlawful under the commission’s rules and weakens the Antarctica Treaty established during the Cold War to set aside the continent as a scientific preserve.

US officials have also privately told their UK counterparts that they would likely bar imports of any toothfish caught near South Georgia, according to correspondence between US fisheries managers and members of Congress seen by The Associated Press.

The fight underscores how Russia’s attempts to undermine the West have extended to even obscure forums normally removed from geopolitical tussles. It also risks reviving Britain’s tensions with Argentina, which invaded South Georgia in 1982 as part of its war with the UK over the Falkland Islands.

But the outcome could not be more consequential; with fish stocks across the globe declining due to overfishing, consumers are demanding greater transparency about where the filets on their plates are sourced. Central to that effort is rules-based international fisheries management on the open ocean and environmentally sensitive areas like the polar regions.

“It sets a dangerous precedent,” said Evan Bloom, who for 15 years, until his retirement from the State Department in 2020, led the US delegation to CCAMLR.

“What the Russians did clearly violates the spirit of science-based fisheries management,” added Mr Bloom, who is now an expert on polar issues at the Wilson Centre in Washington. “But that doesn’t necessarily mean that the UK can act unilaterally.”

Three of the four vessels authorised by the UK to fish near South Georgia starting from May 1 belong to Argos Froyanes, a British-Norwegian company that pioneered techniques credited with dramatically reducing seabird mortality in the south Atlantic.

One of its customers is New York-based Mark Foods, the largest US supplier of sea bass certified by the Marine Stewardship Council, the industry’s gold standard for sustainability.

CEO Barry Markman declined an interview request but said his company would not import any product deemed illegal by US authorities.

“We have been working collaboratively with US officials to resolve this situation in a favourable manner,” he wrote in an e-mail.

Chilean seabass — the commercial name of Patagonia toothfish — from South Georgia is sold at both Whole Foods and Orlando-based Darden Restaurants, which operates the fine-dining chains Eddie V’s and The Capital Grille. Neither company responded to a request for comment.

An official from the government of South Georgia and the South Sandwich Islands, which issued the licenses in co-ordination with the UK Foreign Office, said it took action so as not to give in to obstructionist tactics by Russia that it does not expect will end anytime soon.

The fishery is one of the best managed in the world, with catch limits set by South Georgia below even the quota recommended by CCAMLR. In addition, all vessels authorised to fish near the island have observers and tamper-proof electronic monitoring equipment on board.

Officials say closing the fishery would have taken valuable resources away from research and monitoring because about 70% of the island chain’s budget comes from the sale of licenses.

They point out that the population of toothfish — a bottom-dwelling species capable of living up to 50 years — almost collapsed in the 1990s from poachers drawn to the high prices paid for the bottom-dwelling fish, which can weigh over 200 pounds.

However, thanks in part to the multinational efforts of CCAMLR, the species has bounced back.

“The solution isn’t ideal but it is in the best interest of the fishery,” according to the official who declined to be identified by name.