The answer depends on where you fall on the fairly broad political spectrum of the world’s different tuna watchers. The Fisheries Agency of Japan maintains that “Japan is committed to ensure the recovery” of the Atlantic bluefin and has stipulated it will support a complete shutdown of the bluefin fishery at next fall’s Iccat meeting, should the scientific committee recommend it. Greenpeace meanwhile has punted on the bluefin political process. “Others have failed our oceans,” Oliver Knowles told the press as he prepared his mini armada off Malta, “so Greenpeace will act.” Greenpeace is calling for a radical realignment of the high seas, to take stewardship away from regional fisheries-management organizations and establish 40 percent of the world’s ocean territory as a marine reserve, a kind of Antarctica-style agreement with shades of whale, where nations, instead of bargaining over quotas, would simply not be able to do any fishing at all in large areas of the oceans. Most other environmental organizations are behind the marine-reserve idea, but they vary in opinion on how big those reserves should be. The Blue Ocean Institute calls for a five-year moratorium on Atlantic bluefin fishing everywhere. TheWWF further advocates that the industrial fishing methods that spread during the Age of Tuna — the drift nets, long lines, purse seines and spotter planes — be done away with. In their view, the “artisanal” single-hook-and-line fishing practices of old are the only way to sustainably hunt big and naturally scarce predators like bluefin.

But if we are to embark on a global project of ramping down tuna fishing, what are we to eat?

Until the modern era, the response to wild-game decline has been a primitive one: widespread destruction of the animals that can’t stand up to our hunting followed by the selection of a handful of ones that we can tame. Out of the many mammals that our forebears ate before the last ice age, humans selected four — cows, pigs, sheep and goats — to be their principal meats. Out of all the many birds that darkened the primeval skies, humans chose four — chickens, turkeys, ducks and geese — to be their poultry.

And indeed, this is a process that is taking shape rapidly with fish. Atlantic salmon are now commercially extinct throughout almost the entirety of their range but have become one of the most widely farmed fish in the world.

But while leaps have been made in taming marine fish, tuna, particularly bluefin tuna, may not make very much sense for the farm. Bluefin ranching as it is practiced in the Mediterranean, and with the Pacific bluefin in Japan and the southern bluefin in Australia, rightly faces strong environmental criticisms since it relies on catching juveniles from the wild and denies those baby bluefin a chance to reach adulthood and breed. Now, however, the final steps of fully taming or “closing the life cycle” of bluefin tuna are under way, which will make it possible for bluefin to be grown from an egg in a laboratory to a full-size adult. In such a system, an isolated “domestic” family of bluefin can be established that need not have any interaction with the wild at all. For several years Japan has been producing small amounts of closed-life-cycle Pacific bluefin (known as Kindai tuna in the market). In Europe and Australia, scientists have used light-manipulation technology as well as time-release hormone implants invented by the Israeli endocrinologist Yonathan Zohar to bring about the first large-scale captive spawning of Atlantic and southern bluefin.

But there are considerable complications ahead. As Richard Smullen, an Australia-based feed-company specialist working to come up with a suitable diet for farmed bluefin, explained: “The thing is the metabolic rate of these fish is very high compared to other fish; they swim fast, they heat their brains and vital organs and are warmer than the surrounding water, so this is energetically expensive. An analogy is like trying to feed an ultramarathon runner — they have the potential to eat a lot and not put on any weight.” Though Smullen says that it is possible to bring feed-conversion ratios for bluefin down, currently it may take 15 pounds of feed to produce a single pound of tuna, roughly 10 times as much as is needed for farmed salmon.

As fisheries decline globally, more and more countries are trying to replace their wild fish with farmed ones. Today 30 million tons of small forage fish are removed from the oceans yearly, with the majority of it going to feed farmed fish. If we end up farming bluefin on the same scale as we now farm salmon, the tuna, with its poor feed-conversion rate, may end up taking the food of the remaining wild fish that we haven’t yet got around to catching.

In addition there is little evidence to suggest that taming a species saves its wild forebear. Tiger farms in China have not halted tiger declines in the wild. Hundreds of millions of farmed Atlantic salmon have not stanched wild Atlantic salmon’s continued decline. Just because we can tame something doesn’t mean we should. The example of whales again rises. As the science historian D. Graham Burnett points out in a coming book on the Save the Whales movement, collaborations between American nuclear scientists and marine biologists were once proposed in the 1960s whereby tropical atolls, leveled by nuclear testing, could be used as giant corrals for the commercial farming of cetaceans. But fortunately for the whale — and I think for us too — we have come to see the whale not as something we fish for, not as something we farm, but as something we appreciate and maybe empathize with. Instead of expanding our stomachs or our wallets, whales have expanded our consciousness, our very humanity. So we have to ask ourselves, is there any rational argument for humans to eat bluefin tuna, wild, ranched or farmed? Is the fish really so special that no substitute will do? If the Japanese adapted to a higher-fat diet in half a century, could they and all sushi lovers not shift gears again and adapt to a sustainable diet?