Aquaculture is the raising and harvesting of fresh- and saltwater plants and animals. The most economically important form of aquaculture is fish farming, an industry that accounts for an ever-increasing share of world fishery production. Formerly a business for small farms, it is now also pursued by large agribusinesses, and by the early 2000s it had become almost as significant a source of fish as wild fisheries. Common products of aquaculture are catfish, tilapia (St. Peter’s fish), trout, crawfish, oysters, shrimp, and salmon, and tropical fish for aquariums. Some are raised in huge freshwater tanks or ponds; others require the running water of rivers or streams. Saltwater species are often raised in saltwater ponds, in enclosed bays, or in pens placed in coastal or deeper seawater.