Tuna swim faster than almost any other fish in the ocean—but not fast enough to escape the fishing fleets and farming of humanity. As a result of global demand, the giants of the sea known as bluefin tuna are shrinking in size, or in some cases disappearing altogether. In fact, off the eastern coast of Nova Scotia, where enormous bluefin tuna used to be visible deep beneath the waves, populations have dropped by 90 percent, according to the consortium of countries that make up the International Commission for the Conservation of Atlantic Tunas.

This week, the consortium’s Pacific counterpart—the Inter-American Tropical Tuna Commission—is meeting in Panama City, Panama, to determine the fate of the yellowfin tuna, known as hamachi to sushi connoisseurs and chunk light to American grocery shoppers. Although the fish are not considered threatened, the average size of yellowfins caught has begun to shrink, in the first sign of a crashing population. Environmental groups such as the World Wildlife Fund are calling on the commission to adopt closures to protect the fish and allow stocks to recover.

Yet the 16 countries that make up the commission have found it difficult to agree on conservation measures due to a lack of consensus. And some nations, such as Peru and Japan, are seeking to increase the size of their fishing fleets.

Scientific American's David Biello spoke with Richard Ellis, author of Tuna: A Love Story, about the problems facing the chicken of the sea.

Scientific American: In light of the meeting this week, what is happening with the yellowfin tuna?
Richard Ellis: It's a popular food fish. It is probably, in [the U.S.], the most popular tuna for grilling and for sashimi. Yellowfin is what you get when you order tuna sashimi or sushi in most Japanese restaurants. It is heavily fished... It is yellowfin that is at the top of most lists of concern for fish because it's [the] most heavily fished.

Is it endangered?
They don't know. One of the real problems with ... endangered species, [in] regards [to] fish, is that it's very hard to count them. Usually the count is done via decreased catch. Why is the catch going down? Maybe there aren't many left. But doing an actual survey is virtually impossible. From fishery records, however, primarily Japanese longline [fishing] records, scientists [have] realized that about 90 percent of all big predatory fishes are gone. What they are fishing is the remaining 10 percent. That goes for every large predatory fish: sharks, tuna, sailfish, cod... It's only through fishing that we have any idea how many fish are out there.

What is happening to the tuna generally?
The biggest and most spectacular [tuna] is the bluefin, and it is also the one that is most in trouble. But there are many smaller species that are hunted very strenuously, [such as yellowfin, which are] in many cases overfished and in many cases they're not. Tuna in a can, for example, labeled white meat tuna, it's from a fish called an albacore. It's the only tuna that can be labeled white meat tuna and it's not in trouble. Light meat tuna is skipjack: it's the most popular food fish in the world, just think of the cans of tuna in the world. And it's also not in trouble... But the ne plus ultra of tuna is the bluefin and it's in trouble because it is probably the favorite food of the Japanese.

What is so special about the bluefin tuna?
The bluefin tuna is one of the fastest, largest, smartest, most highly evolved fish on Earth, and it undertakes epic migrations... Admire it as I do, after all my book is called Tuna: A Love Story, I still eat it. And other people love it, not because it's fast or beautiful or intelligent, but rather because they like to see it on a plate...

It wasn't always that way. [At the] turn of the last century, [the bluefin] was considered inedible because of its bright-red meat. It was called horse mackerel. Open a can of it and it would look just like hamburger and that's not the tuna sandwich you want...

People tend to think the Japanese have been eating tuna [sushi] forever but Japanese sushi and sashimi [has existed] only since the 1960s when refrigeration was introduced. Prior to that fish had to be smoked or pickled.

Then people in Japan overdeveloped a lust for bluefin tuna, which has reached its epitome here in New York City where there's a restaurant called Masa [in which] a prix fixe lunch or dinner is $600. For $600, you get some fancy appetizers and a lump of raw fish—maguro, or bluefin tuna.

What is driving the loss of these fish?
The major threat [to] the bluefin is posed by the Japanese, and people attempting to fill the Japanese need have done some rather dramatic things... In the Mediterranean, [fishers] caught hundreds of thousands of half-grown tuna, put them in pens and fed them until they were market size. Then they killed them, froze them and shipped them to Japan. An enormous fortune was made in farming bluefin tuna.

But they are different from salmon, you cannot raise them from eggs. [The] only way to raise tuna [is] this kind of feedlot technology. But when you kill half-grown tuna in significant numbers you are cutting off the breeding cycle... Every single country on or in the Mediterranean, which is one of two breeding grounds for the Atlantic bluefin tuna, does this because there is so much money to be made in it. The largest industry in Croatia, for example, is tuna farming. 

Is it really just the Japanese driving this destruction?
It seems counterintuitive that all those people in the Mediterranean catching all those tuna could sell them all to a country the size of Japan. But then one goes there and visits Tsukiji fish market; 52 acres of fish market. Every day at five in the morning it opens for buyers to purchase the fish that [have] been brought there overnight from everywhere. You are looking at thousands of bluefin tuna that are six feet long and all are auctioned off and gone by 10 in the morning. It happens every singly day of the year. So the bluefin tuna is an endangered species.

What can be done to save the bluefin?
There seems to be, on the horizon, a modest way of solving [the food] part of the problem. Even if they run out of Mediterranean tuna, if they succeed in breeding them from eggs, this could represent some element in the solution [to] the problem. It doesn't protect the tuna but it could take the pressure off the wild fish. If the world were able to see the tuna in the same way as we see cattle, pigs, sheep and chickens: as domestic animals raised to be eaten...

In February of this year, I got an email from the people at Clean Seas Limited. They have succeeded in spawning southern bluefin tuna... It will be a couple of years before they know whether this has really succeeded. They have to figure out what they are going to do with a million six-inch-long tuna but it will change everything about tuna if it succeeds.

But tuna consume 20 kilograms (44 pounds) of smaller fish for every kilogram (two pounds) of their own weight. Is tuna farming going to end up exacerbating the overfishing of other species?
What they are feeding them is anchovies and sardines: foot-long fish. But there are studies being conducted in Japan, Europe and Australia to figure out how to feed them something that isn't foot-long fish. Because what will happen to the foot-long fish if the tuna farming industry increases exponentially? Then you are going to run out of these little fish...

Tuna are frenzy feeders. If you can get them eating then they will bite unbaited hooks. They used to chum up the water and the tuna would strike at a hook with nothing [attached]... It shouldn't be that hard to get tuna to eat. They are voracious eaters... Fooling fish into thinking something is food is the entire history of fishing. So we ought to be able to fool tuna into eating vitamin pills maybe shaped like fish.

Is the mercury in tuna reducing demand?
No. The fishing industry subverted [U.S. Food and Drug Administration] announcements of mercury in tuna by resisting its labeling on cans. If tuna was labeled dangerous, they felt the [product of the] whole fishing industry would become [perceived as] dangerous because people do not distinguish between one kind of tuna and another. The tuna with the most mercury is albacore and the [one with the] lowest [amount is] skipjack... Of course, the amount of mercury in tuna is not enough to kill you and the same fish [such as tuna and salmon] that are mercury-laden are the fish that provide omega-3 fatty acids. On balance, the omega-3 fatty acids may be better for you than the mercury is bad for you as long as you are not eating it every day.

What about dolphin-safe tuna?
Yellowfin tuna [spend] a lot of time swimming underneath spinner and spotted dolphins. So fishermen [would drop] a purse seine, a deep net, around the dolphins to catch the tuna... The tuna fishermen were killing all the dolphins, maybe two to three million dolphins a year.

Ultimately, the Americans regulated how many dolphins you were allowed to bring up in a tuna net ... and fishermen realized that it was too difficult to fish on dolphins because there were so many restrictions that they went west where the same species of yellowfin was not associating with dolphins. They went to the western Pacific and are having a fine old time without catching any dolphins and that's where most of the yellowfin are caught.

Is it too late for bluefin tuna in the wild? Can they recover?
It's too late [for wild bluefin] because, for one thing, I can't imagine anybody who is going to stop fishing for them. You could bring in a 900-pound tuna and sell it to the Japanese for $50,000... That is three times what you would earn in a year as a scallop [fisher] so you are going to drop a line whenever you see a tuna. The highest price ever paid for any fish was a fish sold in the market in Tokyo for $173,000 and that's before it got turned into sushi. By the time it got turned into sushi, that was a million–dollar fish.