All over the world, people are talking about protecting sharks. Tuna falls a litte by the wayside.
How’d they catch it? Is it high in mercury? A guide to the tuna that surfaces in supermarkets, eateries, and sushi bars. In 1950, when tuna usually ended up in sandwiches and casseroles, the worldwide catch totaled an estimated 660,000 tons (600,000 metric tons). Today that annual number has grown to more than 7 million tons (6.6 million metric tons) as the fish has gone gourmet and demand has soared.
The tuna boom has led to a host of concerns about the global fishing business, the state of our oceans, and the health impact of consuming an apex predator. Which kind of tuna is best to buy is a complicated question because it involves a number of conflicting factors. “There are health concerns and culinary needs as well as choices based on sustainability,” says Valerie Craig, who manages the National Geographic Seafood Decision Guide. “How can you know about all those issues for every species?” The first thing to know is that what we call tuna is actually several different kinds of fish. Each has been affected by the fish’s boom in popularity, but some are suffering drastic declines in population. Bluefin tuna, for instance—featured in the March issue of National Geographic magazine—have been so overfished that they can’t reproduce fast enough to replace what’s caught. If you care about sustainability, they should be on your do-not-eat list.
How fish are caught also affects their sustainability. Longlining can be especially devastating because it involves one line that can have 3,000 baited hooks and stretch for up to 50 miles (80.5 kilometers). The hooks dangle at a depth between 328 feet (100 meters) and 492 feet (150 meters), where the largest tuna—such as the threatened bluefin—tend to swim. The hooks also catch more than 80 kinds of non targeted creatures, including endangered sea turtles, which often die on the line before the fishing vessel reels in the catch.
Going after the biggest fish also serves up health concerns to the people who eat them. Big tunas like bluefin feed high on the food chain, so they ingest all the mercury that their prey and their prey’s prey have taken in. The U.S. government offers guidelines for pregnant women, nursing mothers, and small children, but other consumers are also concerned about how to balance the health benefits of eating fish against the adverse effects of mercury. A good general rule: The bigger and older the fish, the bigger the risk.
The best advice is to study up before you go to the supermarket or a restaurant. A good guide outlines the kinds of tuna, where they’re fished, and what kinds of gear are used to catch them in different parts of the world. It may also make suggestions about the greenest and healthiest choices.
In Cans or Pouches
Tuna labeled “light meat” is most likely skipjack, classified biologically as a cousin of true tunas. Skipjack makes up about 70 percent of the canned or pouched tuna. It’s plentiful, so sustainability isn’t an issue. And it’s cheap. It’s also a small, fast-maturing fish that’s relatively low on the food chain, so the level of mercury in its flesh is low. The downside to canned skipjack is that the texture is often mushy, and the taste can be aggressively fishy. Albacore has a mild taste and produces firm chunks of meat. It’s labeled “white meat,” and accounts for about 30 percent of the canned-tuna market. Many albacore are now caught by longlining, so sustainability and mercury content may be issues.
At a Restaurant
With a firm texture and mild flavor, yellowfin tuna often appears on restaurant menus. It may be called “ahi,” a Hawaiian word for tuna. The term “ahi” is also used for bigeye, which may occasionally land on a menu when available. More about them below.
A number of yellowfin populations are overfished now, so only pole-caught fish are considered a good choice for sustainability. Mercury is a concern for those caught by longline. Tuna is a popular food. More than one million tons of tuna are consumed annually in the United States and Japan, the world’s two largest tuna markets. Tuna is the most popular fish in the American diet and is second only to shrimp as the most popular seafood. The average American eats more than three pounds of tuna every year.
If you are a fish eater, there are good reasons to eat tuna. It is very healthy, with lots of protein and very little fat compared to other meats, and it is a good source of omega-3 fatty acids. (Vegetarian sources include some seed oils, purslane, algae, and nut oils.) There are also good reasons not to eat tuna. Like many other ocean fish, it contains mercury, which is toxic to humans. For this reason the U.S. Food and Drug Administration recommends limiting the amount you eat, especially if you are a pregnant woman.
Fish eaters and vegetarians alike also recognize that decades of overfishing of tuna throughout the world has caused some tuna populations to collapse and has pushed others to the brink of collapse. Eating a threatened or endangered species of tuna only serves to hasten the day when it becomes extinct. Finally, the methods used by large commercial fishing vessels to remove tuna from the oceans in species-threatening numbers also result in the killing of countless numbers of other kinds of marine animals—such as dolphins and birds—as bycatch.
The best way to help ensure the recovery of tuna populations and to minimize the harm to other marine life caused by commercial tuna fishing is to avoid eating tuna altogether and to encourage others to do the same. Short of that, educating yourself about the choices you make at supermarkets and seafood restaurants can help to give tuna a fighting chance at a future. Truly conscientious tuna consumers will know what kind of tuna they eat, where it has been, and how it was caught.
Know your tuna
Bluefin. The bluefin is the largest tuna, growing to a length and weight of about 14 feet (4.3 m) and 1,800 pounds (800 kg). It is also the most expensive, owing to its popularity as a sushi delicacy; in Japan, a single fish can fetch more than $60,000. The two main species of bluefin, the Southern and the Northern, are both severely overfished and exploited in all areas, especially the Atlantic. They are listed as critically endangered.
Albacore. Another large species, Albacore is a favorite source of canned tuna. Often marketed as white tuna, it has been called the “chicken of the sea” for the quality of its meat. Its popularity has led to a state of overfishing worldwide that is threatening populations in the Atlantic Ocean.
Skipjack. The relatively small skipjack, which grows to about 3 feet (90 cm) and 50 pounds (23 kg), is the most commonly consumed species of tuna. Although a few populations are stable, it is considered fully-fished to overfished in most areas.
Yellowfin. The second most commonly fished tuna, the yellowfin is a large, fast-swimming fish. The species is considered overfished worldwide. Because of the steadily decreasing size of the fishes being caught, there are fears that not enough yellowfin are reaching reproductive age, which could lead to the collapse of their populations.
Bigeye. Similar in size and appearance to the yellowfin, the bigeye is a popular source of sushi and sashimi. This species is considered to be fully exploited or overfished in every ocean of the world.
Know where your tuna has been
Tuna are found in all of the world’s oceans, but their status in different oceans can vary widely. Most tuna species are in the poorest shape in the North Atlantic and the South Atlantic, including the Mediterranean Sea. Years of overfishing for American and European markets have led to severe reductions in the populations of bluefin, albacore, and yellowfin tuna. Although the Atlantic fishery is highly regulated, illegal fishing off coastal waters continues, especially near Africa, where developing countries cannot afford the patrols necessary to enforce the law. Most tuna populations in the Pacific Ocean and the Indian Ocean are in slightly better shape, especially in the case of albacore. But even in the world’s largest oceans, tuna populations are in decline, and some are in danger of collapsing under the continued weight of large-scale commercial fishing.
Tuna consumers should avoid eating fish that were caught in the Atlantic or the Mediterranean.
Know how your tuna was caught
The vast majority of fished tuna is caught by large commercial fishing vessels using one of two methods: long-line fishing and purse seining. Both methods produce bycatch in large numbers. Other methods have significantly smaller environmental impact but are responsible for only a tiny fraction of the fish available to consumers in the United States and Europe.
Long-line fishing. This method involves releasing extremely long fishing lines—some of them extending for miles—with shorter lines and thousands of baited hooks attached. Although the method is very effective at catching tuna, it’s also effective at catching many other species, among them seabirds that go after the bait in shallow waters. The birds, snared by the hooks, usually drown.
Another problem with long-line fishing is the lines themselves. Made of non-biodegradable monofilaments, the lines are often lost and can drift at sea indefinitely, snagging, entangling, and killing marine life years after they were last touched by human hands.
Purse seining. This method is particularly effective at catching yellowfin tuna. It involves laying out a very large net in a wide circle, which is then drawn inward, capturing the marine life inside. It also produces a significant bycatch—most notably dolphins, since they feed on the same fish as the tuna. Indeed, one reprehensible method, known as “dolphin fishing,” actually targets dolphins themselves, since yellowfin tuna are almost always found in deeper waters beneath them. Although regulations are in place to prevent the deaths of dolphins in purse seines, thousands are killed annually in this practice.
Pole catching. Pole and line fishing, or bait-boat fishing, is the oldest fishing method. Used by local fishermen and sport fishers, it causes far less harm to the environment than commercial methods do. Fish caught in this way, however, are very likely to be sold in local markets and not processed and shipped worldwide.
Ironically, in many areas, ruthlessly efficient commercial fishing has drastically depleted fish populations, forcing local fishermen to abandon sustainable, environmentally-friendly methods that had been used to support families and communities for generations.
Fish farming. Tuna are not naturally suited to being raised in fish farms. As large, predatory open-water fish, they require lots of room and even more food to grow large enough for market. Because this practice is still developing, the majority of farmed tuna are actually caught in the wild to begin captive fish stocks. It remains to be seen whether or not fish farming will have any positive effect on world tuna populations.
Summarize:
If you are a fish eater, there are good reasons to eat tuna. It is very healthy, with lots of protein and very little fat compared to other meats, and it is a good source of omega-3 fatty acids. There are also good reasons not to eat tuna. Like many other ocean fish, it contains mercury, which is toxic to humans. Fish eaters and vegetarians alike also recognize that decades of overfishing of tuna throughout the world has caused some tuna populations to collapse and has pushed others to the brink of collapse.
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