The decline in the North Sea cod stock is a worrying development.
Sustainability certificates for North Sea cod are being suspended following declines in fish stocks, the Marine Stewardship Council (MSC) has said.
Cod stocks in the sea had been thought to be in good health but the latest scientific advice has revealed much lower amounts of fish, putting the fishery in increased danger of collapse.
It means North Sea cod is coming off the menu again for consumers who care their fish supper is sustainable, just two years after the fishery won the recognisable "blue tick" eco-label.
It is not clear what is fuelling the declines, though experts said it could be the result of factors such as warming waters driven by climate change and fewer young cod surviving into adulthood in the past two years.
As a result Marine Stewardship Council certification, which allows seafood to carry the blue tick that shows it comes from sustainable fisheries, will be suspended from all MSC-certified fisheries targeting North Sea cod.
Any cod caught from the date of suspension on October 24 will not be able to carry the label.
The news comes as a blow to the fishing industry which has put in initiatives to actively avoid catching young fish, such closing large spawning areas to fishing, trialling new nets, and avoiding areas where cod congregate to avoid catching them when fishing for other species.
These kind of initiatives helped the fishery win its sustainability certification in 2017, when stocks were assessed as reaching 152,207 tonnes, the highest levels since 1982 and a decade after they came close to collapse.
Stocks were forecast to hit 180,990 tonnes in 2018, but the scientific advice for that year included a far smaller estimate of the amount of cod in the North Sea.
And this year's expert advice from the International Council for the Exploration of the Sea (ICES) revealed estimates of only 81,224 tonnes, below the "safe biological level" for the stock and at increased danger of collapse.
Erin Priddle, UK and Ireland programme director for the Marine Stewardship Council said: "The decline in the North Sea cod stock is a worrying development, with the latest stock models suggesting that the fishery has not recovered as well as previously thought."
She said the latest scientific advice meant the North Sea cod fishery no longer met the MSC standard.
"While this news is devastating for industry, it is a testament to the MSC standard working as it should: to pick up on threats to stock sustainability, as is the case with North Sea cod.
"It is imperative that industry works collaboratively with fishery managers, non-governmental organisations and the wider seafood supply chain to introduce effective measures that will see this fishery once again achieve certification."
Mike Park, chairman of the Scottish Fisheries Sustainable Accreditation Group said: "The industry is concerned that, notwithstanding their best efforts to continue to rebuild North Sea cod, some developments are taking place that seem beyond their control.
"That said, they are committed to introducing balanced and proportionate measures in an attempt to reverse the decline."
The UK consumes 115,000 tonnes of cod a year, 37% of which carries the blue tick label.
Most of what is eaten here, some 94 percent, is imported, with sustainable options from outside the North Sea coming from areas such as Iceland, Norway and Russia, MSC said.
Emily Beament is the PA environment correspondent.