What's Left to Eat?

Fish: Net Results

Seafood provides about 20 percent of the animal protein eaten by Earth's 6.2 billion people. Overfishing, pollution, and some effects of fish farming threaten this crucial food source.

Things looked grim for North Atlantic swordfish in 1999. Decades of overfishinghad caused the population to crash, and biologists wondered if this important food source could survive. So in 1999 a diverse group of nations, including the United States, teamed up to protect swordfish.

The countries agreed that only 10,000 metric tons (11,020 tons) of swordfish could be taken from the North Atlantic each year. That's about a quarter of the amount caught during the peak year of 1995. In addition, the U.S. forbade the use of longlines, which can catch hundreds of fish at a time, in a huge swath of its territorial waters.

The plan seems to be working. By 2003 the number of swordfish in the North Atlantic had skyrocketed. Biologists estimated that the population was 94 percent of the way toward being large enough to survive.

You can learn more about this potential success story from National Geographic News and ICCAT (International Commission for the Conservation of Atlantic Tunas).


Fish section of an international grocery store in Virginia. Photo by Ken Hammond, USDA
Fish section of an international grocery store in Virginia.
Photo by Ken Hammond, USDA

Seafood is one of the most important and healthy parts of the human diet. Eating fish supplies us with proteins as well as amino acids and omega-3 fatty acids that are essential for healthy tissues. Worldwide, people get twice as much of their animal protein from seafood (fish, shrimp, and shellfish) as they do from beef.

Consumption of fish. Source: BBC News Online
Source: BBC News Online

Nearly a billion people, especially in developing countries, rely on fish as their chief source of proteins.


Some fish are still caught in the wild, and are probably the only animals in our regular diet that live in the wild. Catching them can be tough work. In fact, commercial fishing is one of the most dangerous jobs in the United States. For a look at life aboard a Maine fishing boat, check out A Diary of Danger on the Seas.


Fishing crew on the Indian Ocean. Photo by Jose Cort, NOAA
Fishing crew on the Indian Ocean.
Photo by Jose Cort, NOAA


Like farms on land, modern fishing has become highly industrialized. Some of today's fishing "boats" are longer than a football field! These fishing factories, using fast boats and efficient netting methods, can capture fish from deeper and deeper parts of the ocean and from larger areas of the ocean. Such ships often work in fleets comprising "catching vessels" (which haul in the fish) and a "mother ship" (which processes them).

Many of these factory fleets quick-freeze their catches while still at sea. Workers clean the fish, then freeze them almost instantly. Such frozen-at-sea (FAS) fish still have water in their tissues, which helps protect their flavor. Indeed, FAS fish may actually be tastier and healthier than "fresh" fish sold a few days after being caught.


"From giant blue marlin to mighty bluefin tuna, and from tropical groupers to Antarctic cod," biologist Ransom Myers told National Geographic News, "industrial fishing has scoured the global ocean." Myers and other scientists argue that larger fish, of all types, have been particularly decimated, with catches yielding 90 percent fewer large fish now than in 1950.

Likewise, the average size of many kinds of fish is declining. Twenty years ago, the average swordfish brought to market weighed 120 kilograms. Today it's 30 kilograms—one-quarter the previous weight. There has been recent hope for swordfish, however, as you can learn from the sidebar at the right.

United Nations findings are similarly bleak. The UN classifies two-thirds of the world's fishing areas as "fully exploited" or "overexploited." In many areas, overfishing has been so drastic that not enough fish remain to mate and renew the population. This is called recruitment overfishing.

Cod, the key ingredient in Britain's beloved fish-and-chips, offers an example of a fish in hot water. The North Sea, which lies to the east of Great Britain, was once a prime site for catching cod. Now fishing crews are lucky to catch even a tenth of what they could haul in 30 years ago. Even using satellite-tracking equipment and other sophisticated technology, fishing fleets have trouble finding cod. The situation is even worse in the Grand Banks, off the eastern shores of Canada. The last commercially-significant cod there vanished in the early 1990s.

Recruitment overfishing appears to be one of the main culprits. Most cod caught these days are 2-4 years old. That's too young to have reached sexual maturity.

Chilean Sea Bass are also affected by market demand. They normally live as many as fifty years, but pirate fishermen who ignore government regulations catch huge numbers of these fish—called "white gold" because of their popularity with consumers—before they have an opportunity to reproduce. The result: dramatic declines in the Chilean Sea Bass population.


Have you ever wound up thinking, "Well, it seemed like a good idea at the time?" That's the way some people feel about fish farming, also known as aquaculture (and sometimes mariculture). Like farmers on land raise cattle and chicken, people are raising fish, shrimp, and oysters, under controlled conditions in contained areas, either in ponds on shore or in netpens(net cages) located in bays or in the open sea.

Fish farm in Thailand. Photo by R. Faidutti,  United Nations
Fish farm in Thailand.
Photo by R. Faidutti, United Nations

Since the 1970s, aquaculture has been the fastest growing sector of animal food production in the world. As of 2003, fish farms provided nearly a third of all seafood consumed by humans. Farmed fish have also become an important source of protein for animal feeds.

Does aquaculture have its merits?

Yes and no. Aquaculture advocates point out that it's an essential tool for feeding the world's growing population, especially in developing countries, and that fish farms offer an alternative to overfishing the oceans. The overall impact of fish farming depends on the species, how it's raised and fed, and where the farm is located. Tilapia, for example, is a plant-eating fish raised on farms, that doesn't harm the environment.

On the other hand, most aquaculture introduces new problems:

  • Producing fish pellets to feed fish in fish farms requires catching, and potentially depleting, "fish food" species.
  • Fish food may have high levels of contaminants, including POPs (persistent organic pollutants) such as PCBs (Polychlorinated biphenyls) and pesticides.
  • Creating space for fish farms often destroys other ecosystems and threatens biodiversity. Southeast Asians, for instance, have cleared thousands of acres of marshes and mangrove forests that grew at the water's edge. These forests—now replaced by shrimp farms—had served as natural coastal barriers and home to native fishing communities. Learn more about mangroves at San Diego Museum of Natural History's Ocean Oasis.

    video_iconLearn how deforestation threatens fishermen on the awesome Amazon River.
    56k | 220k (RealPlayer required)
    Source: Journey to Planet Earth

  • Crowding huge numbers of fish into a pen can breed disease. To fight disease, fish farmers rely heavily on antibiotics and chemicals, that escape ponds and pens and seep into open waters.
  • Fish waste disrupts natural aquatic systems. Experts estimate that a 200,000-fish salmon farm generates as much waste as a 600,000-person city (without a sewage system).
  • Farm fish can escape through breaks in the nets and wreak havoc on local ecosystems by competing with natural wild fish for food and reproduction.

Find out more about fish farming at Seafoodwatch.


Curbing the widespread growth of aquaculture and dealing with the problems related to overfishing can seem insoluble. But, scientists have identified various actions that would help improve matters:

  • Governments can make and enforce limits on the amount and size of wild fish that are caught.
  • Nets, designed with larger mesh, allow small fish, nonfood fish, such as dolphins, to escape and reproduce. (Undesireable and discarded catch, called bycatch, increasingly depletes the sea's wildlife.)
  • Improving the design and management of aquaculture facilities can reduce and prevent disease and avoid reliance on antibiotics.
  • Developing plant-based food for farm fish would reduce the need to capture "fish food" species.
  • Ecolabels and other government policies can encourage consumers to buy seafood produced via organic aquaculture which does not use chemicals and antibiotics, and allows fish to live in clean, healthy water.
  • The ancient practice of polyculture, raising fish, plants, and animals near each other, could make it easy to use fish wastes to fertilize plants. So would hydroponics, or growing plants in water instead of soil.

One person has given all of us a new way to make a difference. While doing field research around the world, Smithsonian Institution marine biologist Carole Baldwin became highly concerned about what she saw. Baldwin decided to help solve the worldwide problem of overfishing by creating recipes for the dinner table. The book (One Fish, Two Fish, Crawfish, Bluefish: The Smithsonian Sustainable Seafood Cookbook) focuses on fish that are fished or farmed in an ecologically-sound manner, and are not endeangered. From a list of 230 fish species in the U.S. that passed her ecology test, she narrowed the list to 96, and sent it to chefs across the U.S. to ask for recipes. The theory: If people select from a broad range of well-managed species, then we can help relieve the burden on overfished species and prevent others from being fished out.



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