mariculture

Fish cages containing salmon in Loch Ailort, Scotland.

Mariculture is a specialized branch of aquaculture involving the cultivation of marine organisms for food and other products in the open ocean, an enclosed section of the ocean, or in tanks, ponds or raceways which are filled with seawater. An example of the latter is the farming of marine fish, including finfish and shellfish e.g.prawns, or oysters and seaweed in saltwater ponds. Non-food products produced by mariculture include: fish meal, nutrient agar, jewelries (e.g. cultured pearls), and cosmetics.

Farming Methods

Seawater ponds

In seawater pond mariculture, fish is raised in ponds which receives its water from the sea. This has the benefit that the nutrition (eg microorganisms) present in the sea water can be used. This is especially a great advantage over traditional fish farms (eg sweet water farms) of which the farmers often need to buy feed themselves (which is expensive) and supply them manually to the fish. Other advantages are that waterpurification plants may be planted in the ponds to eliminate the buildup of nitrogen, ... (from fecal contamination). Also, the ponds can be left unprotected from natural predators so that another filtering can be done. ^[1]

Sea Ranching

The Japanese have developed a process for free ranching marine fish, called sea ranching. The principle is based on behavioral conditioning and the migratory nature of certain species of marine fish. The fishermen first raise fish hatchlings in a closely knitted net in a harbor. They sound an underwater horn before each feeding. When the young fish are old enough they are freed from the net to mature in the open sea. During spawning season, about 80% of these fish return to their birthplace. The fishermen harvest the fish by sounding the horn and then raising the net.

Algae Farming

Seawater algae such as Kelp can be farmed in at least two ways. They can be grown around a rope that is anchored to the sea floor so that they do not drift away. Off the coast of California, the top few feet of natural kelp beds are harvested by boats with mowers. Kelp provides alginin, an edible material used in ice cream and cosmetics. The industry also supplies the dietary supplement industry.

Species farmed

^[2]

Potential Benefits

With fishery catches on the decline, and Aquaculture products on the incline, Mariculture holds a great promise for the future both economically and environmentally. The broad perception by a large majority of fish consumers that fish is healthy and nutricious is an advantage to Mariculture. Another advantage is the naturalness that farmed fish possess is comparable to those that are harvested from the ocean. Mariculture farming helps the species that may be depleting in the wild such as trout, sea bass and salmon. The consistency of supply year round and more routine quality control has enabled Mariculture supply to be integrated in other food market channels. These benefits have also been able reach different socio-economic classes who may not have been able to purchase fish because of high prices. ^{[3] [4]}

Possible Effects of Mariculture on the Environment

With Mariculture on a rapid rise within the past couple decades it is important to address environmental issues that come along with this boom in the farming of marine life. Negative aspects of all forms of mariculture, regardless of physical structure or economic motivation, affect biodiversity. Mariculture can degrade habitat, disrupt trophic systems, deplete natural seedstock, transmit diseases and reduce genetic variability. These shifts in the natural habitats of the oceans affect the ecosystem as a whole. Most advocates of Mariculture believe that the ocean can be broken up into sections, one not affecting the other. However, this is not the case when considering the negative effects Mariculture has on the food chain and oceanic environment. For example, culture systems in open waters discharge their untreated wastes of feces or uneaten food directly into the water and often at levels higher than the environment can absorb. In the sheltered bays of Mariculture development the overloading of carbon-based nitrogen and phosphorous compounds may lead to blooms of phytoplankton, whose subsequent degradation can drastically reduce oxygen levels. If the algae are toxic, fish are killed and shellfish contaminated. ^{[3] [4] [5]}

Future for Mariculture

Mariculture development must be sustained by basic and applied research and development in all the major fields such as nutrition, genetics, culture system management, product handling, and socio-economics. The future of Mariculture will be focused on a “greener” mindset with the possible use of closed systems. Closed systems in commercial mariculture are seriously considered in some countries (i.e. France) as an alternative to widely accepted intensive cage farming. In theory, it can be constructed everywhere (artificial sea water), and it may guarantee high quality and product freshness. Also important is that such a technology is considered more environmentally friendly when compared to the inshore cage culture. However, investment and operational cost must be lowered for such a technology to show profitability. Otherwise, the use of closed systems will remain a part of the hatchery operations, while further rearing will, at least in the near future, take place in one of the existing conventional systems in which water and energy to heat are available at a low or no cost.^[3]

Scientific literature

Scientific literature on mariculture can be found in the following journals:

See also

• Aquaculture
• Fish farming
• Hydroponics
• Algaculture
• Oyster farming

References

External links

• Longline Environment
• Worldfishcenter -provides info on cultivating certain marine organisms
• Web based aquaculture simulations for shellfish in estuaries and coastal systems: Simulation modelling for mussels, oysters and clams.
• Mariculture guidelines and best practices: A coastal management perspective on mariculture development by the University of Rhode Island Coastal Resources Center.

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