РефератыИностранный языкAqAquaculture Essay Research Paper Aquaculture is the

Aquaculture Essay Research Paper Aquaculture is the

Aquaculture Essay, Research Paper


Aquaculture is the farming of aquatic organisms in fresh, or salt water. A wide


variety of aquatic organisms are produced through aquaculture, including fish,


crustaceans, mollusks, algae, and aquatic plants. Unlike capture fisheries,


aquaculture requires deliberate human intervention in the organisms’


productivity and results in yields that exceed those from the natural


environment alone. Stocking water with (juvenile organisms), fertilizing the


water, feeding the organisms, and maintaining water quality are common examples


of such intervention. Most aquacultural crops are destined for human


consumption. However, aquaculture also produces bait fishes, ornamental or


aquarium fishes, aquatic animals used to augment natural populations for capture


and sport fisheries, algae used for chemical extraction, and pearl oysters and


mussels, among others. Aquaculture is considered an agricultural activity,


despite the many differences between aquaculture and terrestrial agriculture.


Aquaculture mainly produces protein crops, while starchy staple crops are the


primary products of terrestrial agriculture. In addition, terrestrial animal


waste can be disposed of off-site, whereas in aquaculture such waste accumulates


in the culture environment. Consequently, aquaculturists must carefully manage


their production units to ensure that water quality does not deteriorate and


become stressful to the culture organisms. History Aquaculture was developed


more than 2000 years ago in countries such as China, Rome, and Egypt. Not long


after, aquacultural practices in Europe, China, and Japan commonly involved


stocking wild-caught seed?for example, carp fingerlings (juvenile fish)


captured from rivers?in ponds or other bodies of water for further growth.


Mollusk culture was advanced in the 1200s by the discovery in France that mussel


spat (newly settled juveniles) would settle on upright posts in the intertidal


zone, and in the 1600s by the discovery in Japan that oyster spat would settle


on upright bamboo stakes driven into the sea floor. The concept of pond


fertilization was developed in Europe about 1500. In this process, manure is


added to the water to encourage the growth of small organisms such as aquatic


invertebrates and plankton, which in turn are eaten by the fish. The United


States system of federal hatcheries for the breeding of anadromous fishes


(fishes that live and mature in salt water but reproduce in fresh water) was


established in the 1870s. Much of the current technology used to reproduce fish


in hatcheries has been developed by these federal hatcheries. In 1959 the first


marine shrimp hatchery and farm was established in Japan, and it was the


forerunner of the commercial shrimp-culture industry. The salmon-culture


industry in Europe and the channel-catfish-culture industry in the United States


both began in the 1960s. Methods Most fish and crustacean aquaculture is


undertaken in earthen ponds. These ponds are usually equipped with water inlets


and outlets that permit independent control of water addition and discharge.


Ponds are stocked with a specific quantity of juvenile aquatic animals.


Management practices range from pond fertilization, which increases the number


of natural food organisms, to provision of a complete, formulated feed that


supplies all nutrients necessary for growth. Animals that have reached market


size are harvested from the ponds. In a complete harvest, the pond is drained


and all animals are removed from the pond for processing. In a partial harvest,


only a portion of the animals are removed from a full pond using a seine net.


Additional juveniles are often stocked into the pond after a partial harvest,


and the production cycle is continued. Channel catfish grown in the United


States, and marine shrimp grown in China, Central America, and South America,


are often cultured in earthen ponds of about 5 to 10 hectares (about 12 to 25


acres). Fish can also be raised in cages and raceways (long, narrow earthen or


concrete ponds that receive a continuous flow of water from a nearby artesian


well, spring, or stream). Often, several raceways are built in series down the


slope of a hill. Cages are used to raise fish in lakes, bays, or the open ocean


and are constructed of flexible netting suspended from a superstructure floating


on the water’s surface. Many more fingerlings can be stocked into raceways and


cages than into earthen ponds, but nutritionally complete formulated feed must


be provided to fish grown in these systems. Rainbow trout are grown in raceways


in many places, including Chile, Europe, and the United States. Salmon are grown

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in cages, and Norway leads the world in the production of farmed salmon. Carp


raising involves at least three different types of ponds for a whole life cycle


in Europe. Special shallow and warm ponds with rich vegetation provides a good


environment for spawning. After spawning, the parent fish are separated from the


eggs and taken to a second pond. The Fry, which hatch after a few days, are


transported to shallow, plankton-rich nursing ponds, where they remain until the


fall of the year or the next spring. An average harvest of 400 to 500 kilograms


per hectare is normal in intensive cultivation of carp. Crustaceans, mainly


shrimps, are also cultivated not just in Europe but in the United States as


well. Shrimps are cultivated by catching adult egg-bearing females. The female


shrimp are then transported to large sea water ponds nearby the sea or indoor


tanks. After hatching, the shrimps are fed in indoor tanks with cultivated


plankton. After ten days they are brought to shallow ponds for even further


cultivation or distribution to farms. Mollusk aquaculture is carried out in


coastal waters either as bottom culture or off-bottom culture. In bottom


culture, juvenile organisms are spread over prepared areas of the ocean floor in


either the intertidal zone or shallow coastal waters. In off-bottom culture,


juveniles attached to a substrate, such as oyster spat attached to oyster shell,


are bound to ropes and suspended from rafts or floats. Advantages of off-bottom


mollusk culture include protection from predators and the ability to use more


vertical space. Seaweed is also grown using off-bottom culture techniques, most


notably in Asia. Production Aquaculture is practiced in many regions of the


United States. Channel catfish are grown primarily in the southern and


southeastern United States, with greatest production in Mississippi, Arkansas,


Alabama, and Louisiana. More than 75 percent of the trout produced domestically


for human consumption are grown in Idaho. Japanese littleneck clams and Pacific


oysters are grown along the Pacific Coast, and hard clams and American bluepoint


oysters are grown along the Atlantic Coast. Most U.S. fish farms that produce


ornamental fishes are located in Florida. The largest bait-fish aquaculture


industry is located in Arkansas. The global aquacultural yield in 1992 was 19.3


million metric tons (42.5 billion pounds), worth approximately $32.5 billion.


This yield, which represented nearly 20 percent of world fishery production, was


composed of 48.8 percent fishes, 5.1 percent crustaceans, 18.1 percent mollusks,


27.9 percent algae and aquatic plants, and 0.1 percent other organisms.


Aquacultural production has grown steadily from an estimated 1 million metric


tons (2.2 billion pounds) in 1966 to the current value. World aquacultural


production is expected to grow 5 percent annually through the year 2000. The


Environmental Impacts of Aquaculture Aquaculture provides for many people a


large production of nutritious, high-quality foods. However, similar to the


conventional agriculture, there are many adverse environmental impacts of


aquaculture. The most important effects are ecological, and these are associated


with the conversion of natural ecosystems into complex and intensively managed


aquaculture ecosystems. For example, the conversion of tropical mangrove systems


into aquacultural facilities used to raise prawns yields a combined loss of


natural ecosystem, In other words, the conversion has significant consequences


for species in the environment, and usually causes damage to offshore


ecosystems. With the world?s steadily growing population limiting supplies of


food, water, minerals and energy, scientists believe we will have to rely on the


vast resources of the sea as key to sustaining human life. Fortunately, the


government is striving for an increase in ocean commercialization (the


development, harvesting and marketing of the ocean?s resources for a profit)


to meet the rapidly growing needs of humanity, and noticing the importance of


preserving and protecting the marine environment. Although, careless ocean


commercialization can have very serious side effects. One of the many effects is


seafood and water contamination by ocean pollution posing health risks for both


marine life and humans. With government support, many businesses such as DuPont,


Lockheed and International Nickel have already begun ocean commercialization.


Most of the current methods of ocean commercialization are aquaculture, the


farming of marine fish and plants; the conversion of saltwater to freshwater;


utilization of tidal and thermal energy; and the incineration of hazardous


wastes.

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