Many tinned mackerel products sold in British supermarkets no longer contain any of the oily fish, as concerns over sustainability have pushed retailers to replace it with Chilean jack mackerel, a different species with lower nutritional value. Tesco and J Sainsbury supplier Princes switched its branded mackerel range to Chilean jack mackerel last year, which contains roughly half as much omega-3 and about 100 fewer calories per 100g than true mackerel. Customers have complained about differences in taste and texture, including bigger bones and less oily flesh.

Lidl has been transitioning to sustainably sourced Chilean jack mackerel, while Waitrose stopped sourcing fresh, chilled and frozen true mackerel in April citing overfishing concerns, with canned products being phased out as existing stocks are sold. The shift follows a years-long dispute over quotas, known as the "mackerel war", involving the UK, Iceland, Greenland, Norway, the Faroe Islands, the EU and Russia. Mackerel catch in the North-East Atlantic has been 39 per cent above scientific advice since 2010, and stocks have fallen by about three-quarters in the past decade, according to the International Council for the Exploration of the Sea (Ices).

Chilean jack mackerel is Marine Stewardship Council certified, unlike the depleted North-East Atlantic stock. British retailers are following a broader European retreat from true mackerel, with Albert Heijn and Jumbo in the Netherlands and Axfood in Sweden also replacing mackerel-in-tomato products with jack mackerel. Until December 2025, UK labelling laws prohibited marketing Trachurus species as "jack mackerel", but Defra changed the rules weeks after Princes launched its product, permitting the new labelling while prohibiting "Atlantic" mackerel claims.

Critics argue the change risks confusing consumers and blurs the distinction between true mackerel and jack mackerel.