Supermarkets are increasingly replacing tinned mackerel with a cheaper, less nutritious alternative known as jack mackerel, according to a report by consumer group Which?. The substitution, described as an example of 'skimpflation', involves major retailers such as Princes and Lidl, which have switched to jack mackerel due to dwindling stocks of Atlantic mackerel and sustainability concerns.

The shift is driven by overfishing of Atlantic mackerel, with stocks having plummeted by roughly three-quarters over the past decade. The Marine Stewardship Council (MSC) has advised a 70% reduction in catches in 2026 to allow the stock to recover. Chilean jack mackerel, which is MSC-certified, is significantly cheaper, costing about one-third as much as Atlantic mackerel. However, it contains about half as much omega-3 and around a third as much vitamin B12 as traditional mackerel.

Princes announced in October 2023 that it was changing all its tinned mackerel products to jack mackerel, stating the species meets MSC sustainability standards. The company claims its products are 'clearly identified' and were introduced after extensive testing. Lidl is selling jack mackerel under its house brand, with the company stating it is 'committed to sourcing fish and seafood from responsibly managed fisheries'.

Consumer groups have raised concerns over the nutritional downgrade and potential confusion over labeling. Sue Davies of Which? warned that manufacturers have a responsibility to be transparent when changing product recipes, as shoppers may not realize a product has changed until they consume it. Some consumers have reported differences in taste and texture, with the Scottish Pelagic Fishermen's Association expressing concern over the potential for confusion.

The switch follows the so-called 'mackerel war', a long-running dispute over shared mackerel catch quotas between the UK, Iceland, Greenland, Norway, the Faroe Islands, the EU, and Russia. The countries have repeatedly failed to agree on catch limits in line with scientific advice, leading to overfishing and stock depletion. The Marine Conservation Society has called for urgent action, noting that Atlantic mackerel is at 'breaking point'.

The trend is not limited to the UK, with supermarkets in the Netherlands and Sweden also switching to jack mackerel. Waitrose suspended sales of fresh, chilled, and frozen mackerel in February 2024, citing overfishing concerns, while tinned products were phased out as existing stock was sold. The Marine Conservation Society praised this move as 'leading and decisive'.

The report highlights the broader implications of the shift, including potential environmental impacts and the need for greater transparency in food labeling. The full impact of the change on consumer health and the seafood industry remains unclear.