Tuna

Tuna is mackerel’s cousin – the cousin who grew to be bigger, race faster and smell more refined. From the subclan’s humblest member, the half-metre-long bullet that is mackerel’s nearest cognate, to the bluefin going for top dollar at Tokyo’s boisterous fish auctions, tuna, like mackerel, are Scombridae – as is the bonito, included here for ease of reference. Indeed, at the edges of the tuna constellation, identities become somewhat blurred. In some taxonomies, and particularly for commercial purposes, the bullet tuna is in fact a mackerel; while the bonito is, in effect, a tuna.

Present in various incarnations across fishing zones, tuna are apex predators. They feed on many fellow marine creatures, mackerel included; by contrast, few others feed on tuna. These hunters live long, swim fast and migrate far. Their muscular flesh runs to deep pinks and crimsons; the skin is like sun-baked aluminium, streaked with greyish blues.

Tuna are large – often very large – fish, which means they’re never eaten whole. Much as for the big land animals that form part of modern diets, cuts run the gamut of desirability. The marbled, exquisitely flavoured, fattier parts from the belly of the fish – known as ventresca in Italy and otoro in Japan – tend to be the most prized: they are to tuna what Kobe fillet is to beef.

Cuts aside, different species have different uses. Prices rise in line with prestige (though it’s fair to say these hierarchies have varied with the decades: as with lobster, for example, shifting fashions have moved erstwhile workaday species up the value chain). At entry level, we find the stuff that supplies most markets with canned tuna. Best friend to students, singles and Sunday cooks, this is generally the pale albacore in its superior version, and a slightly rougher, oilier skipjack at the more democratic end. Thailand is the world’s top canned tuna exporter, cranking out billions of dollars’ worth in 2020.

Yellowfin, the next step up on the marketing ladder, is a versatile fish, available as steak or sushi; bigeye tuna provides a higher grade of the latter. Both are known in Hawaii and the wider United States of America as ahi – and dominate the canned segment in Italy. Most exclusive of all is bluefin, whose lush, gamey flesh winds up as the choicest sashimi: here, the raw fish is given star billing, without the admixture of rice or vinegar. Japan alone concentrates four-fifths of the market.

With tuna being the highly migratory fish that they are, roaming across multiple jurisdictions, regional fisheries bodies have been set up to issue binding rules for sustainable management. Because of its premium appeal, bluefin has long concentrated efforts. Pacific Small Island Developing States (PSIDS), for example, have teamed up to cap fishing licenses. Meanwhile, “ranching” of bluefin – that is, catching young individuals and raising them in captivity – has been spreading since the early 1990s. Farming bluefin from eggs, long thought a technical impossibility, is also shaping up as a viable option.

Such practices have somewhat relieved pressure on wild stocks. In 2021, the International Union for Conservation of Nature (IUCN) declared Pacific bluefin “of least concern” (though still severely depleted, at less than 5 percent of its original biomass) and Atlantic bluefin “near-threatened” – an improvement for both. Southern bluefin is endangered, though no longer critically so. Overall, ethically minded buyers may wish to approach bluefin with a discerning mind.