The truth about tinned tuna

It’s the nation’s favourite tinned fish, but how much do we know about tuna? The United Nations declared last Monday as World Tuna Day, to draw attention to the one-third of tuna stocks that are overfished. Not so surprising, perhaps, given that one in five of us eats it at least once a week, and last year Brits bought nearly 62,000

tonnes of tinned or jarred tuna in the supermarket, according to a recent report by fish sustainability organisation the Marine Stewardship Council (MSC).

Tins of tuna are a store-cupboard staple, a last-minute lunch or lazy supper. More recently, upmarket cans and jars from the continent have turned tuna into a treat worthy of a dinner-party starter.

The good news is that a recent report by the Marine Conservation Society (MCS) pointed out that tinned fish, if caught sustainably, could be one of the most sustainable and healthy fish to eat. True, tuna is higher up the food chain than the other tinned favourites, such as sardines, pilchards and mackerel, which makes it more vulnerable to accumulating mercury contamination from the pollution in the seas. For this reason pregnant women are advised not to eat more than four tins a week –which is a lot of tunamayo sandwiches, let’s face it.

There are five main varieties of tuna eaten, ranging from the critically endangered bluefin, which can weigh more than 1,300lb, to skipjack, not a true tuna, weighing up to 77lb. In between come yellowfin, bigeye and albacore. Then there is the little bonito (not to be confused with bonito del norte, another name for albacore), which is sometimes substituted for tuna and weighs only around 13lb.

Yet despite this range, the vast bulk of the tins we sling in our trolley are marked simply ‘tuna’. Perhaps the manufacturers think we just don’t care, but as it turns out, all tuna is not equal, in flavour or the sustainability stakes.

BLUEFIN TUNA This sometimes turns up in jars in posh delis labelled ‘tonno rosso’, an Italian name that refers to the dark-red flesh. It’s endangered, so off my shopping list, although there are cheering reports that bluefin stocks in the waters around the north-east of England are improving.

ALBACORE Labelled ‘white tuna’ in the States, this has a mild flavour and meaty texture, and is considered by many to be the best tinned tuna. Msc-certified albacore is considered a top (dark green) choice by the MCS.

BIGEYE TUNA Along with yellowfin, this is labelled as ‘light tuna’ in the States. It has more flavour than albacore, without being overpowering, and a higher fat content than yellowfin. The dark meat tastes much stronger than the paler flesh. Considered a vulnerable species by the World Wildlife Fund, it contains twice as much mercury as yellowfin tuna.

YELLOWFIN This is sweet and mild flavoured, similar to bigeye, with a tendency towards dryness. Msc-certified yellowfin tuna gets a top green rating from the MCS, but much of the uncertified tuna including most that’s caught in the Indian Ocean is red – fish to avoid.

SKIPJACK Amounting to 60 per cent of the world’s ‘tuna’ catch skipjack isn’t even a true tuna, but a different genus from the other four types of tuna – Katsuwonus rather than Thunnus. Skipjack has a more pronounced flavour than other varieties and a firm, dry texture. Msccertified skipjack gets a top green rating from the MCS, but net-caught skipjack from the Pacific and Indian Oceans is a red, so ‘fish to avoid’.