Tesco is removing several lines of John West tuna from its shelves. So what varieties are sustainable, how should they be caught and from where?

For those who want to shop responsibly, fish is the PhD. Ideally, we would rely on retailers to make the judgment. Just this week, Tesco decided to remove “a number of core John West lines” from its shelves after concluding that the company’s tuna does not meet its standards.

Facebook Twitter Pinterest John West tuna: no longer meets Tesco’s standards. Photograph: Stuart Clarke/Rex/Shutterstock

In practice, however, the picture is bewildering. It is hard to be sure of what you are buying. If you shop somewhere else, you may know even less. The Marine Stewardship Council’s blue tick can be relied on, when you can find it, but much sustainable fish does not have it yet. The Marine Conservation Society’s free Good Fish Guide app contains all the information you need, but it is far from simple. “All seafood is a minefield,” admits Sam Stone, who is fisheries and aquaculture programme coordinator at the MCS. So what should you consider if you want to buy sustainable tuna in the UK?

Species



There are seven varieties of tuna you might buy: albacore, bigeye, skipjack, yellowfin, Atlantic bluefin (farmed and wild), southern bluefin (farmed and wild) and Pacific bluefin. One rule here is simple: avoid all bluefin tuna. Some are critically endangered species, and even farmed bluefin have to be captured from the wild. So no bluefin. Ever.

Albacore can be sustainable, bigeye and yellowfin rarely are, so the best tuna variety to choose is generally skipjack, a fast-growing species that is still quite plentiful around the world and makes up most of the tinned tuna you will find. The problem here, however, is how it’s caught.

Why bluefin tuna have no 'fair' price Read more

Fishing method



Even healthy tuna stocks can be fished in such a way that lots of other animals – such as dolphins, sharks, seabirds and turtles – get killed in the process. Dragging a short line through the water means it can be aimed carefully, and checked more often, so it is better at catching tuna only. The names of these better methods are handline, pole-and-line or troll fishing. Fishing with a long line – often tens of kilometres long – is less safe, as it is hard to control and stays in the water for longer.

Fishing with a big net is generally even worse, as other animals get scooped up indiscriminately. However, it is not always unsustainable. Tuna caught by purse seine or pelagic trawl is sometimes fine. On the whole, you should avoid tuna caught by gillnet or drift net. To complicate things, using a Fad – or fish aggregation device – makes any fishing method worse. This can be almost anything, such as a raft, which floats in the open sea, encouraging fish to gather beneath it – including juveniles and other species. Fad-assisted fishing is usually done with a purse seine.

Location



Where the tuna is caught matters for two reasons. First, stocks may be close to collapse in some places but not in others. Yellowfin tuna is dangerously overfished in the Indian Ocean, for instance, but more numerous in the Pacific. Second, fishing methods vary from place to place. So while there are plenty of skipjack tuna in the western and central Pacific, they are too often fished there with nets and Fads that also catch bigeye tuna by mistake.

So, for instance, Tesco Every Day Value tuna chunks are good, because they are skipjack that was caught with a pole and line. Whereas Waitrose yellowfin tuna steaks are um, don’t know, because they might have been caught by handline in the western and central Pacific (good) or they might been caught on long lines in the Indian Ocean (bad). They also cost 10 times as much.