Aquaculture is the breeding, rearing, and harvesting of fish, shellfish, plants, algae and other organisms in all types of water environments. As the demand for seafood has increased, technology has made it possible to grow food in coastal marine waters and the open ocean. Aquaculture is a method used to produce food and other commercial products, restore habitat and replenish wild stocks, and rebuild populations of threatened and endangered species. There are two main types of aquaculture—marine and freshwater. Marine aquaculture produces numerous species including oysters, clams, mussels, shrimp, seaweeds, and fish such as salmon, black sea bass, sablefish, yellowtail, and pompano. There are many ways to farm marine shellfish, including “seeding” small shellfish on the seafloor or by growing them in sinking or floating cages. Marine fish farming is typically done in net pens in the water or in tanks on land. Freshwater aquaculture primarily takes place in ponds or other manmade systems. According to the Food and Agriculture Organization (FAO), aquaculture "is understood to mean the farming of aquatic organisms including fish, molluscs, crustaceans and aquatic plants. Farming implies some form of intervention in the rearing process to enhance production, such as regular stocking, feeding, protection from predators, etc. Farming also implies individual or corporate ownership of the stock being cultivated. The reported output from global aquaculture operations in 2014 supplied over one half of the fish and shellfish that is directly consumed by humans; however, there are issues about the reliability of the reported figures.Further, in current aquaculture practice, products from several pounds of wild fish are used to produce one pound of a piscivorous fish like salmon.