Aquaculture and fish farming has emerged as one of the fastest-growing -- and most controversial -- areas of agribusiness. Though it's often perceived as an economically viable alternative to wild fisheries, the environmental and health risks of the typical fish farm can't be ignored.
Aquaculture: Facts and Figures
Aquaculture refers to the production of dozens of water-born products: food fish, ornamental fish like koi and aquarium fish, bait fish, mollusks, crustaceans, aquatic plants, algae including spirulina -- even alligators and turtles are included. These plants and animals are grown in several climates, from deserts to freshwater lagoons, and in fresh or salt water.
According to the U.S. Department of Agriculture, the overall value of aquaculture production in America rose to nearly $1 billion over the past two decades, and in 2005 (the latest year for which data are available) a USDA Census of Aquaculture found that farm-level sales of aquacultural products reached $1.1 billion.
Over 40 percent of all U.S. aquaculture sales are for catfish, the largest single product in aquaculture and concentrated in the southeastern United States. Other popular food fish include trout, salmon, tilapia, striped bass, sturgeon, walleye and yellow perch. Most of these are grown in freshwater ponds (salmon are hatched in fresh water, then raised in saltwater pens).
Freshwater crayfish and shrimp are also popular aquacultural products, as are mollusks such as abalone, oysters, clams and mussels. Though the United States is a major aquaculture producer, it still imports many products, especially shrimp, salmon and tilapia.
Worldwide, the aquaculture market reached an estimated $86 billion in sales in 2009. China is reportedly the single largest producer, generating over 70 percent of the world's aquacultural output.
Feeding a Hungry World - At a Price
As the world population passes 7 billion people, there's no doubt that aquaculture will continue to play an important role in providing healthy, low-fat protein for hungry mouths. And the health benefits of fish -- especially cold-water fish high in omega-3 fatty acids -- cannot be denied.
However, the environmental impacts of aquaculture also can't be denied. Worldwide, critical habitats like mangrove forests are being destroyed to support shrimp farms. Over 400,000 hectares of Asian mangrove forests -- which are necessary for erosion control, water quality and natural habitat for many species -- have been razed for shrimp production.
Like any factory farm, a fish farm requires the use of synthetic feed and chemicals. The use of antibiotics is a particular concern, since these drugs are often used without oversight and contribute to the rise of antibiotic-resistant "superbugs." These drugs, and other compounds like pesticides, then enter the natural ecosystem where they can have unknown (or deadly) consequences on wild species.
Feeding millions of fish and other species requires a lot of food -- and much of it comes from wild fish. Salmon, for example, are carnivores, and producing a pound of salmon requires three to five pounds of wild fish. Between 1985 and 1995, the world's shrimp farmers used an estimated 36 million tons of wild fish to produced just 7.2 million tons of shrimp. Thus, like beef production and other sources of animal proteins, aquaculture can be notoriously inefficient and is contributing to the depletion of fisheries worldwide.
Aquaculture and Pollution
Intensive agricultural practices, including aquaculture, produce immense amounts of pollution. One source of this pollution is leftover food -- because food is generally broadcast over the water in fish feeding operations, any leftover food just settles to the bottom where it slowly rots away. This creates a kind of underwater cesspool, where many bottom-dwelling plants and animals can't survive; the problem is especially acute in inland lakes, though it's also been documented in coastal aquaculture facilities.
In addition to food waste, fish excrement and fecal waste reach extremely high levels in aquaculture facilities. When tons of "fish poop" mixes with decomposing fish food, it changes the chemistry of the water across a large area, increasing nitrogen levels while reducing the amount of oxygen in the water. This causes explosive growth in algae (aka algal blooms) and makes it nearly impossible for many animals to survive.
While there are technological fixes to many of the problems presented by aquaculture -- introducing species like scallops and sea cucumbers to reduce fish waste, for example -- many fish farms aren't closely regulated, or are located in countries where there are no regulations. As a result, many environmentalists continue to voice concerns about the growth of aquaculture and other factory-farming techniques.