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Aquaculture

Aquaculture, also known as aqua farming, is the farming of aquatic organisms such as fish, crustaceans, mollusks and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the harvesting of wild fish. Mari culture refers to aquaculture practiced in marine environments.

Methods

Mariculture

Mariculture is the term used for the cultivation of marine organisms in seawater, usually in sheltered coastal waters. In particular, the farming of marine fish is an example of mariculture, and so also is the farming of marine crustaceans (such as shrimps), molluscs (such as oysters) and seaweed.

Integrated

Integrated Multi-Trophic Aquaculture (IMTA) is a practice in which the by-products (wastes) from one species are recycled to become inputs (fertilizers, food) for another. Fed aquaculture (for example, fish, shrimp) is combined with inorganic extractive (for example, seaweed) and organic extractive (for example, shellfish) aquaculture to create balanced systems for environmental sustainability (biomitigation), economic stability (product diversification and risk reduction) and social acceptability (better management practices).

“Multi-Trophic” refers to the incorporation of species from different trophic or nutritional levels in the same system. This is one potential distinction from the age-old practice of aquatic polyculture, which could simply be the co-culture of different fish species from the same trophic level. In this case, these organisms may all share the same biological and chemical processes, with few synergistic benefits, which could potentially lead to significant shifts in the ecosystem. Some traditional polyculture systems may, in fact, incorporate a greater diversity of species, occupying several niches, as extensive cultures (low intensity, low management) within the same pond. The “Integrated” in IMTA refers to the more intensive cultivation of the different species in proximity of each other, connected by nutrient and energy transfer through water.

Ideally, the biological and chemical processes in an IMTA system should balance. This is achieved through the appropriate selection and proportions of different species providing different ecosystem functions. The co-cultured species are typically more than just biofilters; they are harvestable crops of commercial value.  A working IMTA system can result in greater total production based on mutual benefits to the co-cultured species and improved ecosystem health, even if the production of individual species is lower than in a monoculture over a short term period.

Sometimes the term “Integrated Aquaculture” is used to describe the integration of monocultures through water transfer.  For all intents and purposes however, the terms “IMTA” and “integrated aquaculture” differ only in their degree of descriptiveness. Aquaponics, fractionated aquaculture, IAAS (integrated agriculture-aquaculture systems), IPUAS (integrated peri-urban-aquaculture systems), and IFAS (integrated fisheries-aquaculture systems) are other variations of the IMTA concept.

Species groups

 Fish

The farming of fish is the most common form of aquaculture. It involves raising fish commercially in tanks, ponds, or ocean enclosures, usually for food. A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species’ natural numbers is generally referred to as a fish hatchery. Fish species raised by fish farms include salmon, big eye tuna, carp, tilapia, catfish and cod.

In the Mediterranean, young blue fin tuna are netted at sea and towed slowly towards the shore. They are then interned in offshore pens where they are further grown for the market.  In 2009, researchers in Australia managed for the first time to coax tuna (Southern blue fin) to breed in landlocked tanks.

Crustaceans

Commercial shrimp farming began in the 1970s, and production grew steeply thereafter. Global production reached more than 1,600,000 tonnes (1,570,000 LT; 1,760,000 ST) in 2003, representing a value of nearly 9,000 million U.S. dollars. About 75% of farmed shrimp is produced in Asia, in particular in China and Thailand. The other 25% is produced mainly in Latin America, where Brazil is the largest producer. Thailand is the largest exporter.

Freshwater prawn farming shares many characteristics with, including many problems with marine shrimp farming. Unique problems are introduced by the developmental life cycle of the main species, the giant river prawn.

Algae

Microalgae, also referred to as phytoplankton, microphytes, or planktonic algae constitute the majority of cultivated algae. Macroalgae, commonly known as seaweed, also have many commercial and industrial uses, but due to their size and specific requirements, they are not easily cultivated on a large scale and are most often taken in the wild.

Types of Aquaculture Systems

There are many types of systems and farm designs used to grow fish. These include; ponds, net cages in lakes or oceans, rectangle raceway tanks, circular (round) tanks, earthen tanks lined with plastics or clays and other forms of containment. Basic Land based fish farms involve the use of one or more types of tanks or ponds and generally have water piped in and out to maintain life support for the fish and to flush the tanks of waste products. Basic designs may also include mechanical aeration equipment for adding oxygen to water.

In recent years land based farms have advanced in technology to become more eco-friendly and to provide greater security and control of the farming process. The most advanced of these are known as water recirculation systems or RAS designs. Advancements in design and technology are being driven in part by the need to develop alternative methods for aquaculture and by the demand for more fish and secure supplies.