Extra fishy: your tinned mackerel may not be what you think it is

Some tinned mackerel is no longer real mackerel. Big brands such as Princes, and some supermarket own labels, now use jack mackerel instead. Jack mackerel is a different species and is much cheaper. It is often sold at a similar price to the real thing. The consumer group Which? calls this 'skimpflation'. The tins are labelled, but experts say shoppers may not notice the change until they get home.

Mackerel stocks have fallen after years of heavy fishing, so brands have looked for other fish. Jack mackerel tastes different and has different nutrients, making it a poor swap for the oily fish many people want. Skimpflation happens when a product is quietly changed or shrunk while the price stays the same. Which? says makers must be open with shoppers when they change a recipe. Tinned fish is a cheap source of protein for many households.

Shoppers pay the same for a lesser product. Families may also get fewer healthy oils than they expect from a cheap and popular source of protein.