If you’ve recently opened a tin of mackerel and thought there was something fishy going on, you may have been right. An overfishing crisis means that instead of traditional mackerel, some now contain a different fish with a similar name, prompting concerns that shoppers are being short-changed.

Over the past year big brands such as Princes, as well as some supermarket own labels, have replaced traditional tinned mackerel fillets with jack mackerel fillets.