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Role of Mariculture in worldwide food production
Mariculture is the term used when referring to the farming of marine species by man. The broader term called 'aquaculture' is what is used to describe all types of production of aquatic species, both seawater and fresh water. Some types of mariculture are truly historical whereas others are more modern-day. Mariculture is the commercial farming of marine organisms. This form of farming has a long history in Australia and has made a significant contribution to the nation's marine products ($AUS708 million 2003/2004).
Mariculture includes a wide range of species and culture methods. It is growing fast on a global scale. At the same time the world population is rising and with it the need for dietary protein. The expansion of mariculture can reduce pressure on wild fish, shrimps and molluscs, because they reduce their market price and by this the investments in fishing fleets, or they can increase the pressure due to the use of fishmeal in feed for some mariculture-species. Some of the important aspects to go for this technique are:
- The farming & husbandry of marine plants & animals in brackish water/marine environments.
- Output is growing globally, & its practices have important implications for marine & coastal biodiversity on the level of genes, species & ecosystems. Increased from 9M tonnes in 1990 to > 23M tonnes in 1999.
- Increase is a result of higher production of a few spp.
- Provides good quality food, more efficient than many other forms of food production farms.
- Humans consume < 1% of terrestrial 1° organic matter production, (which totals ~ 132B tons, & < 0.02% of the 82 billion tons of 1° production of the oceans)
- Fish can replace terrestrial animals at ~ ½ the level of feed inputs. Hence, mariculture is a more efficient user of primary productivity than the farming of livestock.
- Brackish water aquaculture production is dominated by shrimp but also includes finfish & molluscs.
- Marine aquaculture is dominated by seaweed (Japanese kelp), and molluscs, Pacific cupped oyster and salmon.
Types of Mariculture
Coastal Mariculture:Marine resources in many coastal regions are overexploited. Mariculture, the deliberate production of marine plants and animals, may offer one solution to this problem; principles of agriculture can be applied to improve yields of selected marine species.
Algal Turf Mariculture:Recent research by the Smithsonian Institution's Marine Systems Laboratory (MSL) has shown that mariculture of fine algal turfs, commonly found on highly productive coral reefs and similar hard bottom communities, is biologically feasible. Under proper environmental conditions simulating reef process, algal turfs may be grown on screens. This production can serve as feed for marine animal grazers that, in turn, could be consumed by humans.
Closed system:Closed systems in commercial mariculture are 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), it may guarantee high quality and product freshness. Also important is that such a technology is considered environmentally friendlier when compared to the inshore cage culture.
Cage culture:Mariculture in cages began in Japan in the 1950s but developed largely as a result of the salmon farming industry in northern Europe and North America during the past two decades. Cages account for about 60% of coastal fish culture, and if considering Mediterranean aquaculture it account above 90% of all seabass and seabream production. The main advantages of cages when compared to conventional land-based systems include low capital costs and simple management. However, their vulnerability (storm weather, poachers and vandals) characterising such a production risky.
Different techniques of Mariculture
Seaweed Mariculture:During winter all the seaweed found in the intertidal rocks, at low tide are burnt by the seaweed farmers. Then the new seaweed grown are called sea lettuce (Ulva). This is one of the prized edible seaweeds. The collection of seaweeds are done with a pair of baskets then spread out in the sun to dry. The 'cakes' of dried seaweed are packed in burlap bags and sold to brokers in San Francisco’s Chinatown. This little known mariculture operation went on for about 100 years (1860-1960) in Central California.
Abalone Mariculture: This process generally takes four to five years before a marketable product is ready. Right now the marketable product is either live abalone or vacuum packed abalone steaks. The abalone brood stocks are kept in large tanks and treated with seawater. After the formation of veliger larval stage, these microscopic planktonic larvae settle and begin life as a bottom dwelling (benthic) abalone. The Abalone Farm takes a keen interest in the health of the offshore kelp beds and works hard to maintain these natural resources so that they can remain as a natural food source for the growing abalone. When the abalone is 4-5 years old and 3.5 - 4.5 inches across they are harvested and sold as live abalone or as prepared steaks. Each steak is about an ounce and four make up one serving of a main course. The cost for prepared steaks is between $70 to $100 per pound.
Oyster Mariculture:Oysters the commonly cultured shellfish are treated with warm water and cool water by mariculture farms worldwide. They are eaten raw or cooked. These bivalves have international appeal. With native populations declining in many areas the mariculture of oysters can be a booming business if the company has access to a clean and proper seawater supply.
Lobster Mariculture: There are few places in the world where lobster mariculture is successful. This is mainly because lobsters have several planktonic larval stages which may each require slightly different conditions and food. But, one of the biggest obstacles to raising lobsters is that they are cannibalistic as juveniles and thus must be separated into individual containers while growing. Because of this it is very time consuming and thus costly to raise lobsters in an artificial environment.
Salmon/Steelhead Mariculture:The Feather River Fish Hatchery, in northern California, operates to improve the stocks of Chinook salmon and steelhead trout in the natural environment. This hatchery is operated by the California State Department of Fish and Game under contract with the Department of Water Resources.
Mariculture is an expanding industry in Australia and recent graduates are employed on farms in the areas of operation, management, research and development. State departments of primary industry or agriculture or resource sciences employ officers in the areas of environmental planning, policy development, implementation and biological & ecological monitoring and research. Federal agencies, for example CSIRO and the Australian Institute of Marine Science, and universities are the main employers of researchers, while universities also employ lecturers to teach mariculture. Furthermore, opportunities exist for experienced people to work as consultants to this developing industry.
The mariculture industry inevitably faces, and at the same time causes, considerable problems. For example, the developement of fish farming is in direct conflict with other uses of the same coastal resources, e.g. reclamation, amenity, recreation and navigation. Pollution has also directly or indirectly caused a substantial loss to the mariculture industry. From 1976 to 1986, it was estimated that some 532 tonnes (valued at US$ 4.6million) were lost to the industry in 106 fish kills. Of these, 36 incidents were attributed to oxygen depletions, algal boom and red tidal and another 16 incidents to direct pollution effects.
The National Center for Mariculture (NCM), located on the North Beach of the town of Eilat develops technologies for rearing marine fish and other marine species having a high economic value. Studies carried out at NCM provide the infrastructure for the development of mariculture in Israel as a novel agricultural branch utilizing marine and brackish water and for the establishment of associated biotechnological industries. The main research effort at NCM today focuses on developing an environmentally friendly land-based system for rearing fish in seawater ponds. This novel technology includes biological purification of the effluents of the system, which are partly recycled through the grow-out systems with the remainder being returned to the sea without causing any environmental damage.
Mariculture is also an element of the elaborated programme of work on marine and coastal biological diversity. Mariculture production worldwide is growing at the rate of about 5 to 7 per cent annually. Mariculture can play an important role, especially in rural areas for food security, economic and social welfare. In heavily populated coastal areas mariculture is in competition with other human activities for space and other resources.
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