Types of Fish Farms

Commercial fish farms now raise nearly 40 percent of seafood eaten by consumers. Pelagic fish like salmon and tuna mature in holding pens rather than the open ocean. Catfish and tilapia on market shelves nearly always come from farms rather than wild fish populations. As fisheries dwindle, farms attempt to domesticate more and more species of fish and shellfish to meet a growing demand.

  1. Carnivorous Fish

    • Perhaps the most controversial fish farms raise salmon and tuna, both of which are carnivorous species living near the top of the natural food chain. Grown to maturity in open holding pens in coastal waters, the farm fish must be fed meals that include fish protein and oil from other wild-caught species. About 10 pounds of wild fish produces 1 pound of farm fish for the table, placing continuing pressure on the natural fisheries. Problems with disease and parasites among the tightly packed schools may have affected the health of their wild counterparts, contributing to an overall decline in those fisheries.

    Catfish

    • Subsisting in the wild on a varied diet, catfish adapt to vegetable protein feeds. Channel catfish raised in inland ponds in Mississippi, Arkansas and other states of the American Deep South tolerate pond conditions in a naturally balanced environment. The dense populations of catfish farm ponds require constant adjustment of oxygen levels and water quality to prevent disease and parasitic infection.

    Tilapia

    • Tilapia farms in the Americas raise tilapia--a native of the Middle East--in indoor tanks rather than outdoor ponds in order to lessen the chance that this fish will escape. If established in the wild, the prolific tilapia could displace many native American species. Most tilapia farms providing fish for the U.S. market are located in Central America.

    Shellfish

    • Farms producing oysters, clams and mussels rely on clean water in order to produce shellfish for human consumption. Feeding on plankton, the shellfish actually improve water conditions rather than becoming a source of pollution. Artificial clam beds of sand provide easy harvesting without damage to the environment. Oysters raised on nets lowered into coastal waters also have no harmful impact.

    Other Species

    • Worldwide, many other species now lead domesticated lives. Carp have long been a staple product of the ponds of Asia and Europe. In the U.S., trout farms supply restaurants and groceries as well as providing captive sport for fishermen. Many of Southeast Asia's mangrove forests have been replaced by temporary saltwater ponds along the coasts, where shrimp are grown for a few years until conditions become too polluted.