The cultivation of fresh-water and marine species (the latter type is often referred to as mariculture). Aquacultural ventures occur worldwide. China grows macroalgae (seaweeds) and carp. Japan cultures a wide range of marine organisms, including yellowtail, sea bream, salmonids, tuna, penaeid shrimp, oysters, scallops, abalone, and algae. Russia concentrates on the culture of fish such as sturgeon, salmon, and carp. North America grows catfish, trout, salmon, oysters, and penaeid shrimp. Europe cultures flatfish, trout, oysters, mussels, and eels. Presently, plant aquaculture is almost exclusively restricted to Japan, China, and Korea, where the national diets include substantial amounts of macroalgae.
The worldwide practice of aquaculture runs the gamut from low-technology extensive methods to highly intensive systems. At one extreme, extensive aquaculture can be little more than contained stock replenishment, using natural bodies of water such as coastal embayments, where few if any alterations of the environment are made. Such culture usually requires a low degree of management and low investment and operating costs; it generally results in low yields per unit area. At the other extreme, intensive aquaculture, animals are grown in systems such as tanks and raceways, where the support parameters are carefully controlled and dependence on the natural environment is minimal. Such systems require a high degree of management and usually involve substantial investment and operating costs, resulting in high yields per unit area.
A unique combination of highly intensive and extensive aquaculture occurs in ocean ranching, as commonly employed with anadromous fish (which return from the ocean to rivers at the time of spawning). The two most notable examples are the ranching of salmon and sturgeon. In both instances, highly sophisticated hatchery systems are used to rear young fish, which are then released to forage and grow in their natural environment. The animals are harvested upon return to their native rivers.
Intensive aquaculture brings with it high energy costs, necessitating the design of energy-efficient systems. As this trend continues, aquaculture will shift more to a year-round, mass-production industry using the least amount of land and water possible. With this change to high technology and dense culturing, considerable knowledge and manipulation of the life cycles and requirements of each species are necessary. Specifically, industrialized aquaculture has mandated the development of reproductive control, hatchery technology, feeds technology, disease control, and systems engineering.
Regardless of the type of system used, aquacultural products are marketed as are fisheries products (which are caught in the ocean), except for some advantages. For one, fisheries products often must be transported on boats and may experience spoilage; whereas cultured products, which are land-based, can be delivered fresh to the various nearby markets. Also, intensively cultured products through genetic selection can result in a more desirable food than those caught in the wild, with uniform size and improved taste resulting from controlled feeding and rearing in pollution-free water. Agriculture Marine fisheries