AQUACULTURE. Aquaculture, the controlled or semi-controlled production of aquatic plants and animals, has increased at double-digit percentage rates since the early 1980s. This increase has been in response to declines in commercial harvests of wild stocks of fish and shellfish. Oceans of the world are currently at maximum sustainable yield. Since the late 1980s, there has been a concerted effort to maintain global commercial harvest of ocean fish at approximately 100 million metric tons (mmt). However, as global population grows, demand for fish and shellfish increases, and the percentage of aquatic products grown in aquaculture must likewise rise to meet the supply of those products. Projections for increased production are in the range of 40–100 mmt of new aquaculture production by about the year 2030. The lower range assumes only increases in world population; the upper figure represents increases in world population plus a 1 percent per year increase in per capita consumption. To put this number in perspective, the 1995 world production figures for soybeans was 137 mmt, swine was 83 mmt, and chickens was 46 mmt. Thus, to meet demand in the first part of the twenty-first century, we must realize significant growth. This increase in production will not be accomplished with a single species.
There are fewer than thirty large species-specific aquaculture industries globally, and the fourteen largest industries are listed in the table. However, there are over twenty-five thousand species of fish and there are estimates that one thousand new species are being evaluated for their culture potential. The small percentage of species raised relative to the total number available is an indication that aquaculture is a new concept in many parts of the world. As a subsistence enterprise, aquaculture has been practiced for over four thousand years. As a series of large industries, aquaculture is less than fifty years old, often stimulated by declining wild stocks of fish. The channel catfish industry, which only began in the late 1960s in the southern United States, is illustrative of a relatively young industry. Today, over 90 percent of the U.S. supply of Atlantic salmon is cultured. In 1980, that figure was a fraction of 1 percent, at most. The global supply and demand characteristics created a good deal of volatility in production, which has only increased over time. Additional factors such as identification of new
|The largest aquaculture industries, by volume, in 1999|
|Values are in million metric tons|
|Giant tiger prawn||3,651,782|
|Pacific cupped oyster||3,312,713|
|Japanese carpet shell||2,194,521|
diseases and movement of those diseases contribute to the volatility in production. Inevitably, as new aquaculture species are brought into culture settings, new diseases are identified that were previously unknown. In the past ten years, new viral diseases have been identified in shrimp and salmon, both of which caused large-scale losses from production facilities.
Of the approximately 25 mmt of global aquaculture production, there are only a few industries that produced over 1 mmt in 1996. Several of the species of Asian carp and the common carp account for the largest industries. Silver carp production was 2.2 mmt, grass carp production was 1.8 mmt, bighead carp production was 1.1 mmt, and common carp production was 1.5 mmt. Virtually all of this production occurred in China with the exception of common carp, which is raised throughout Europe, its native range. Of the species typically available in U.S. markets, pen-raised Atlantic salmon accounted for 0.4 mmt, rainbow trout production for 0.3 mmt, channel catfish production for 0.2 mmt, and tilapia for 0.6 mmt. Production of several invertebrates was significant. Scallop production was 1.0 mmt, shrimp production was 0.9 mmt, oyster production was 1.1 mmt, mussel production was 1.0 mmt, and clam production was 1.0 mmt. Production of brown seaweeds was 4.5 mmt and red seaweed production was 1.6 mmt. Thus, the largest aquaculture industry is the production of brown seaweeds, largely for nonfood use. In the twenty-first century, greater demand will likely result in increased production.
There are only a few production systems in use for aquaculture, and they include earthen ponds, raceways, cages or net pens, and indoor recirculating systems. Earthen ponds or cages placed in existing bodies of water are the oldest production system and the indoor recirculating systems are the newest. For successful culture, considerable technical expertise is required when using a recirculating system. All of the current industries use earthen ponds (catfish, tilapia, Asian carps, shrimp), raceways (rainbow trout), or cages/net pens (Atlantic salmon, yellowtail, an amberjack from Southeast Asia). Producers are experimenting with indoor recirculating systems using a wide variety of species. There are a few successful producers using indoor systems, but the number will inevitably grow as both the systems themselves and information on targeted species increase. Successful aquaculture can be viewed as the correct match of species under a certain set of market conditions with production system. Some species do not tolerate some of the production systems or do not thrive in those systems. Behavioral characteristics of the various species often point toward the appropriate culture systems. For example, sedentary fish (bluegill, catfish, and flounder) should probably be raised in systems without significant water flow (earthen ponds, cages/net pens), whereas those that typically swim a great deal (tuna, trout, and striped bass) can be raised in raceway systems with a constant flow of water.
Fish are generally considered good quality food for human consumption because of the low saturated fat levels and generally high levels of n-3 fatty acids. Fish tend to retain the fatty acids that are in their diet. Thus, we can manipulate the fatty acid concentrations of fish and produce "designer fish" for targeted markets. Further, we can control the fat concentration in muscle through selected feed and produce a low-fat or high-fat fish depending on the demands of the market. Cultured aquatic animals can be safer products for consumption than wild fish because they are raised in a defined environment, and pollutants can be eliminated. Wild fish can be exposed to environmental pollutants and retain those they encounter. Organoleptic properties (taste) of fish and shell-fish raised in aquaculture can be quite different from wild stocks. Fish flavor can be manipulated by dietary ingredients fed to the target species. If the diet contains a relatively high percentage of fish meal, the fish can taste fishier than if the diet contains a relatively high percentage of corn and soybean products. Fish fed the latter diets are often described as "milder" tasting, which is a desirable characteristic in certain markets. There is also a taste consideration with environment. Some species can survive both fresh-and saltwater, but osmoregulation changes to meet the challenges of those environments. This physiological change affects taste because of the chemical compounds used to regulate ionic balance. A good example of this is the freshwater shrimp. When raised in freshwater, taste has been described as mild, whereas if the shrimp is placed in saltwater for one to two weeks, it will taste more like a marine shrimp. Even with these positive attributes, aquaculture is experiencing growing pains.
Culture of aquatic animals produces the same wastes as other animal production industries. The problem is confounded by the fact that those wastes are discharged as rearing water is renewed. There have been incidences of environmental degradation resulting from aquaculture. One of the focal points of aquacultural research is waste management, focusing on phosphorus and nitrogen dynamics originating in the diet. Those efforts, as well as efforts related to siting aquaculture operations, land-use practices, and economic development, have become the focal point of sustainable aquaculture development. Along with the overall focus on sustainability, there are significant concerns about the feed used to achieve aquaculture's successes. Fish meal is a high-quality ingredient, yet it is a finite resource similar to all other species in the oceans. Ingredients made from soybeans, corn, canola, wheat, legumes, peanuts, and barley, as well as the by-products of the brewing industries and animal packing operations, are needed.
Growth of aquaculture in the twenty-first century will most likely be similar to growth in terrestrial animal production seen in the twentieth century. Fish and shell-fish are the last major food item humans still hunt and gather from wild populations. The sustainable nature of aquacultural production probably will be the focal point of research in the early part of the twenty-first century and those results should facilitate the production increases necessary for sufficient quantities of fish and shell-fish in the future.
See also Crustaceans and Shellfish ; Fish, subentries on Freshwater Fish and Sea Fish .
Adelizi, Paul D., Ronald R. Rosati, Kathleen Warner, Y. Victor Wu, Tim R. Muench, M. Randall White, and Paul B. Brown. "Evaluation of Fish Meal-Free Diets for Rainbow Trout, Oncorhynchus mvkiss." Aquaculture Nutrition 4, no. 4 (1998): 255–262.
Donahue, Darrell W., Robert C. Bayer, John G. Riley, Alfred A. Bushway, Paul B. Brown, Russell A. Hazen, Keith E. Moore, and Dorothy A. Debruyne. "The Effect of Soy-Based Diets on Weight Gain, Shell Hardness, and Flavor of the American Lobster (Homarus americanus )." Journal of Aquatic Food Product Technology 8, no. 3 (1999): 69–77.
Floreto, Eric A. T., Robert C. Bayer, and Paul B. Brown. "The Effects of Soybean-Based Diets, with and without Amino Acid Supplementation, on Growth and Biochemical Composition of Juvenile American Lobster, Homarus americanus." Aquaculture 189 (2000): 211–235.
New, M. B. "Aquaculture and the Capture Fisheries—Balancing the Scales." World Aquaculture 28 (1997): 11–30.
Riche, M., and P. B. Brown. "Incorporation of Plant Protein Feedstuffs into Fish Meal Diets for Rainbow Trout Increases Phosphorus Availability." Aquaculture Nutrition 5 (1999): 101–105.
Twibell, Ronald G., and Paul B. Brown. "Optimum Dietary Crude Protein for Hybrid Tilapia Oreochromis niloticus x O. aureus Fed All-Plant Diets." Journal of the World Aquaculture Society 29 (1998): 9–16.
Twibell, Ronald G., Bruce A. Watkins, Laura Rogers, and Paul B. Brown. "Dietary Conjugated Linoleic Acids Alter Hepatic and Muscle Lipids in Hybrid Striped Bass. Lipids 35 (2000): 155–161.
Wu, Y. Victor, Ronald R. Rosati, and Paul B. Brown. "Effects of Lysine on Growth of Tilapia Fed Diets Rich in Corn Gluten Meal." Cereal Chemistry 75 (1998): 771–774.
Wu, Y. Victor, Kerry W. Tudor, Paul B. Brown, and Ronald R. Rosati. "Substitution of Plant Proteins or Meat and Bone Meal for Fish Meal in Diets of Nile Tilapia. North American Journal of Aquaculture 6 (1999): 58–63.
Paul B. Brown
"Aquaculture." Encyclopedia of Food and Culture. . Encyclopedia.com. (November 22, 2017). http://www.encyclopedia.com/food/encyclopedias-almanacs-transcripts-and-maps/aquaculture
"Aquaculture." Encyclopedia of Food and Culture. . Retrieved November 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/food/encyclopedias-almanacs-transcripts-and-maps/aquaculture
Aquaculture, a type of agriculture, is the practice of cultivating aquatic animals and plants in managed aquatic environments. Aquaculture in salt-water or marine environments is called mariculture. Fish culture, or pisciculture, refers to the husbandry of finfish . The most popular aquaculture species are finfish grown in fresh waters, accounting for over 40 percent of total aquaculture production (U.S. Department of Agriculture, 1998).
Ancient and Modern Aquaculture
Aquaculture has a long history, but for much of the world it remains somewhat of a novelty, being practiced less than agriculture or capture fisheries . Yet as the world demand for fish increases, recent advances in growing fish in captivity have led to a rapid expansion of the aquaculture industry.
During the last 30 years of the twentieth century, aquaculture grew at an average annual rate of 10 percent, and emerged as the only growth sector of the fisheries industry. At the beginning of the twenty-first century, aquaculture's share of total fish production worldwide was 25 percent, and that proportion is projected to increase. Even though the production of fish from capture fisheries has not substantially increased over the past decade (1990s), capture fisheries nevertheless account for a far greater percentage than aquaculture.
The roots of aquaculture trace back 4,000 years to China where carp were cultured, and before that to Egypt where early pictorial depictions dating to 2500 b.c.e. show tilapia being fished out of a tank. The earliest known written record of fish culture techniques is attributed to Fan Li, of China, who in 475 b.c.e. described propagation methods, pond construction, and growth characteristics of common carp.
From those early beginnings to the present, common carp is the best understood of all aquaculture species. Common carp reportedly were grown in Europe 2,000 years ago, and, although the ancient Greeks and Romans held fish in ponds, more advanced techniques for breeding and growing fish in managed environments in Europe were first devised 1,000 years ago.
The Japanese, Polynesian Hawaiians, and Mayans were also early practitioners of fish culture. In the United States, nineteenth-century scientists developed techniques for breeding rainbow trout in captivity. Rainbow trout have since been transplanted from their native Western U.S. streams to many countries in Europe, Africa, and South and Central America.
Criteria for Commercially Successful Aquaculture
The twentieth century witnessed the science of fish culture unveiling many new methods for growing aquatic animals and plants. Advances in controlled reproduction of desired species, feed formulation, and water quality management have helped generate the rapid growth of aquaculture. The biological selection of culture species depends on many factors. A few criteria that must be considered in choosing a species to cultivate include the following characteristics of a species:
- Growth rate;
- Place in the food chain;
- Climate and environmental adaptations;
- Disease resistance;
- Breeding characteristics;
- Compatibility with other fish species in cultivation; and
- Conversion efficiency (feed-to-flesh).
For example, aquaculturists prefer fast-growing planktivores because of their short food chain.
Interestingly, biotechnological selection criteria are not always the most critical; for example, growing fish unsuitable for local or export markets can readily drive a farmer out of business. Thus, consumer preference, market conditions, regulations against nonnative species, and other economic, social, and political criteria play an important role in species selection.
Diversity of Aquaculture Species
Hundreds of species of finfish, crustacean , mollusks , and plants are used in aquaculture. Most are finfish species, and many of these are grown as food fishes . The most common fresh-water aquaculture species are carp, tilapia, catfish, and trout. Other species are cultivated as bait fish , ornamental fish for water gardens and aquaria, sport (game) fish, laboratory fish for experimentation, industrial and medicinal products, and as native fish to mitigate losses to wild fish populations.
In the United States, catfish and trout, grown as food fishes, are by far the most popular aquaculture species. But other species are also commonly grown for food, including salmon, striped bass, and tilapia. Also, there is a small industry for alligators, frogs, turtles, egg seed stock, and ornamental fishes.
Purposes of Aquaculture
Aquaculture is practiced for a number of reasons, chief among them being food production and income generation. Most fresh-water aquaculture production (over 70 percent) comes from low-income, food-deficit countries. Even in the poorest countries, fish farming is seldom solely a subsistence activity. So while farmers may consume some of their product, typically fish are sold, thereby enabling farmers to earn income to purchase other goods and services.
Additional purposes of aquaculture include:
- Utilizing land unsuitable for agriculture;
- Utilizing inland water bodies such as shallow lakes;
- Reclaiming saline soils;
- Increasing the supply of highly valued species;
- Improving the reliability of fish supplied in the marketplace;
- Offsetting losses in the capture fisheries or in native fish populations;
- Servicing the sport fishing industry;
- Controlling parasites like mosquito and snail larvae that cause diseases such as dengue fever and malaria;
- Storing water; and
- Earning foreign exchange. (Europe and the United States import aquaculture products from Asia, Africa, and Central and South America.)
Types of Aquaculture Operations
Aquaculture operations range from small, backyard water gardens to energy-intensive, large commercial farms encompassing hundreds of hectares . Aquaculture is sometimes combined with agriculture as in rice–fish farming, or in duck–fish ponds. It is also practiced as polyculture , where a variety of species occupying different ecological niches are cultivated together. Aquaculture involves many levels of intensity and complexity, from gravity-fed ponds with little or no inputs, to intensive systems that use aeration , supplemental feeds, antibiotics, and genetically modified species.
Systems for rearing fish depend on the environment and the objective of the aquaculture operation. In the United States and worldwide, the most common rearing unit is the pond, although other types of units are also used: cages, net pens , flow-through raceways, and recirculation tanks. Efficient farm management and careful water-quality management are keys to a successful operation, regardless of the culture unit. With poor water quality, for example, fish exhibit higher incidence of disease. In addition, poor water quality often yields effluents (wastewater and byproducts) that can have negative environmental effects.
Potential Adverse Effects
Not too long ago, aquaculture was perceived as a cure for hunger and dwindling wild fish supplies. At the end of the twentieth century, given the rapid growth of the aquaculture industry, critics began questioning the real social and environmental impacts of aquaculture. The social impacts are generally felt more acutely in poorer countries. For example, people have been displaced from their homes and jobs by aquaculture operations, sometimes by operations that pollute land and water previously used by local residents.
Aquaculture, like any farming activity, produces effects on the environment. Aquaculture uses energy and creates wastes. As aquaculture replaces wild habitat , changes to the ecosystem inevitably occur. Even where aquaculture operations are placed in non-pristine areas, potential exists for exotic (nonnative and genetically altered) aquaculture species to escape and adversely affect native species by competing for food and space, interbreeding and hybridizing native species, and spreading disease. Collecting wild larvae for rearing in aquaculture units can decimate native populations of fish, and can affect biodiversity. Toxic and bioaccumulative compounds can be harmful to people, including fish farmers themselves, and to plants and animals. Excessive discharge of organic wastes causes pollution.
The environmental impacts of effluents depend on the type of aquaculture practiced, and on farm management. Aquaculture can, in local situations, improve the environment or be environmentally benign. If ponds are properly managed, nutrient-rich discharges (soil and water) can be dredged for use in crop production, thereby reducing the need for soil amendments such as inorganic fertilizers.
Fish ponds can increase bird populations, which are pleasing to birdwatchers, but are disdained by fish farmers. While poorly managed fish ponds can serve as breeding grounds for vectors of animal and human disease, well-managed fish ponds can be used to control these vectors. Thus, fish farm management geared at minimizing negative environmental effects can be critical for balancing the farm's impact on the environment, and for its own long-term success.
see also Agriculture and Water; Fisheries, Fresh-Water; Fisheries, Marine; Mariculture; Pollution by Invasive Species.
Hillary S. Egna
Bardach, John, John Ryther, and William O. McLarney. Aquaculture: The Farming and Husbandry of Freshwater and Marine Organisms. New York: Wiley-Interscience, 1972.
Egna, Hillary S., and Claude E. Boyd, eds. Dynamics of Pond Aquaculture. Boca Raton, FL: CRC Press, 1997.
Pillay, T. V. R. Aquaculture and The Environment. New York: Halsted Press, 1992.
Rath, Rajendra Kumar. Freshwater Aquaculture. Jodhpur, India: Scientific Publishers, 1993.
Review of the State of World Aquaculture. FAO Fisheries Department. FAO Fisheries Circular No. 886 FIRI/C886 (Rev.1), Rome, 1997. <http://www.fao.org/docrep/003/w7499e/w7499e00.htm>.
The State of World Fisheries and Aquaculture 1998. United Nations Food and Agriculture Organization, 2000. <http://www.fao.org/docrep/w9900e/w9900e00.htm>.
U.S. Department of Agriculture. 1998 Census of Aquaculture. <http://www.nass.usda.gov/census/census97/aquaculture/general.htm>.
"Aquaculture." Water:Science and Issues. . Encyclopedia.com. (November 22, 2017). http://www.encyclopedia.com/science/news-wires-white-papers-and-books/aquaculture
"Aquaculture." Water:Science and Issues. . Retrieved November 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/news-wires-white-papers-and-books/aquaculture
Aquaculture is the rough equivalent of agriculture on land. Aquaculture is the raising of fish, shellfish, or aquatic plants to supplement the natural supply. Although aquaculture includes the growing of aquatic plants, most people use the term to mean fish and shellfish farming. Fish and shellfish are raised as food under controlled conditions all over the world. The goal of fish and shellfish culture is to increase the yield of useful products, including increased food production.
While most aquacultural production is in food items such as fish, mollusks , and crustaceans , some marine algae, kelp, and other aquatic plants are raised commercially. Cultured pearls are created by placing small bits of material in the shells of young oysters. Various types of floating algae and phytoplankton are also grown, primarily as food for animals.
Aquatic animal husbandry includes all of the activities terrestrial farmers and ranchers have used, such as selective breeding, care of the young, feeding, sanitation, environmental modifications, and harvesting. Species having characteristics that make them suitable and practical for culturing are selected for extensive cultivation. This includes considerations of consumer choice. Aquaculture is relatively expensive, so most aquacultural products are luxury items such as trout, oysters, and shrimp. Some less expensive fish species, such as carp and tilapia, are successfully cultured in China, India, and southeast Asian countries.
History of Aquaculture
Aquaculture has been practiced for thousands of years. Chinese in the fifth century C. E. practiced aquaculture, and temple friezes (ornamented bands on a building) dating from the Middle Kingdom of Egypt (2052-1786 B. C. E. ) depict what appear to have been intensive fish farming. The ancient Romans are known to have cultivated oysters.
As suitable arable land diminishes and the world's population increases, aquaculture is expected to become increasingly important. Aquaculture is an environmentally friendly source of high-quality animal protein. Many countries with limited arable land, such as Japan, are actively developing an aquaculture industry.
Problems of Aquaculture
Aquacultural practices are not as efficient as they could be. Lack of capitalization in developing countries, inefficient and outdated techniques, and poor marketing all contribute to the lack of commercial success in aquaculture. Another factor limiting production is the lack of suitable domesticated species. Only a few aquatic animals are used, and much of the life cycle of these animals is not controlled. Research into new species, development of commercially viable hybrids , and new techniques of breeding should improve the efficiency of commercial aquaculture. Continued research and the dissemination of new skills and techniques holds promise for substantially increased aquacultural production, perhaps exceeding 30 million metric tons (33 million short tons) per year.
Selection of Suitable Species
In order to be aquaculturally useful, species must be able to reproduce in captivity, have robust eggs and larvae, feed on inexpensive food, and grow quickly to harvestable size. For example, trout and carp have large, hardy eggs; mullet fry are easily collected; and young oysters are easily collected and grown. So these were the species of choice for aquaculture. The feeding habits of species also limit suitability. Wide-ranging plankton feeders, such as herring, are not suitable. Sessile animals, such as oysters and mussels, which filter the water for their food, can be cultured extensively but still must be supplied with a rich food supply if they are to grow rapidly.
Aquaculturists, like their terrestrial counterparts, selectively breed for desirable traits in captive organisms. Since the traits that enhance success in a wild population are often inconsistent with a successful captive population, these traits must be eliminated through breeding. Desirable characteristics include fast growth and a body shape that provides more edible tissue. Since captive populations are usually held at a higher density than wild populations, disease is a problem. So resistance to disease is desirable. Since aquatic animals usually produce many offspring per generation, selective breeding is somewhat easier than with terrestrial animals.
One desirable characteristic of captive populations is an accelerated onset of sexual maturity. This event is triggered in the wild by a combination of factors, including water temperature, length of daylight hours, and salinity. These factors in turn act on the animal's pituitary gland, which controls the output of sexual hormones. Attempts to control environmental factors to accelerate spawning have been largely unsuccessful, except in the cases of oysters and shrimp. A more generally successful method involves the injection of pituitary hormones. This is expensive and labor intensive so alternatives are being sought.
Large-scale fish culture projects, if properly managed, have the potential to produce thousands of tons of fish. Community ponds and reservoirs created by the damming of tropical rivers are often designed to include largescale fish farming. When a new reservoir is created, nutrients from the soil trigger the growth of abundant algae and aquatic plants. So herbivorous fish must be included in the plans. These fish can provide the first harvested "crops."
Fish "ranching" is also widely practiced. For example, salmon are raised in hatcheries then released into wild streams. This allows the establishment of new salmon runs, the reintroduction of salmon into previously used streams, and the replenishment of depleted stocks. This form of aquaculture also helps alleviate losses due to human-induced environmental degradation.
Hybridization is another technique coming into use in aquaculture. Crossing one trout with another trout having seagoing tendencies enables breeders to send fish to new oceanic pastures and then to harvest them when they return to freshwater to spawn. Promising crossbreeding experiments with tilapia have also resulted in species exhibiting hybrid vigor.
Both coal-fired and nuclear power plants use water for cooling. This water is generally discharged into a reservoir of evenly warmed water. This water has significant potential to be used in aquacultural programs. Many aquatic animals grow more rapidly in somewhat warmer water. Other species, such as carp and catfish, prefer warmer water. Many of the farmraised catfish available in supermarkets are grown in ponds warmed by water from power plants.
Pelagic (open ocean) fish have not been raised in captivity with any great success. They are desirable species because they grow fast. But they require huge quantities of food fish or other pelagic organisms, which are also hard to raise in captivity. As research continues, it is likely that new aquacultural techniques will be developed that will permit the farming of many new species such as spiny lobsters, crayfish, octopus, and others not presently husbanded. Improved techniques will increase the yield of existing aquacultural species. As demand continues to increase for world food supplies, aquaculture promises to grow into a thriving and productive industry.
see also Farming.
Curtis, Helena, and N. Sue Barnes. Biology, 5th ed. New York: Worth Publishing, 1989.
Lovell, Tom. Nutrition and Feeding of Fish. New York: Van Nostrand Reinhold, 1988.
Miller, G. Tyler, Jr. Living in the Environment, 6th ed. Belmont, CA: Wadsworth, 1990.
Purves, William K., and Gordon H. Orians. Life: The Science of Biology. Sunderland, MA: Sinauer, 1987.
"Aquaculture." Animal Sciences. . Encyclopedia.com. (November 22, 2017). http://www.encyclopedia.com/science/news-wires-white-papers-and-books/aquaculture-0
"Aquaculture." Animal Sciences. . Retrieved November 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/news-wires-white-papers-and-books/aquaculture-0
Aquaculture refers to the breeding of fish and other aquatic animals for use as food. Aquaculture has long been practiced in China and other places in eastern Asia, where freshwater fish have been grown as food in managed ponds for thousands of years. Since the mid-twentieth century, however, the practice of aquaculture has spread around the world, with many new species of freshwater and marine animals being cultivated. By the late 1990s, aquaculture produced some 20 percent of the fish eaten by people around the world—over 20 million tons. The principle goal of aquaculture science is to develop systems by which fish can be grown and harvested at large rates, while not causing environmental damage in the process.
The oldest fish-farming systems were developed in Asia, and involved several species of freshwater fish. The first writings about the methods of fish farming date from about 2,500 years ago. The first species to be grown in aquaculture was probably the common carp, a fish native to China but now spread throughout the world.
Fish farming involves the management of all steps in the life cycle of the cultivated fish, from the production of eggs through the growth and eventual harvest of a high-quality, mature fish. Fish are most commonly raised in artificial ponds or in cages or pens set into larger bodies of water, including the ocean. The fish are fed a nutritious diet—sometimes to excess so they may grow to their maximum size—and are administered medicines to maintain their health. Additionally, chemicals are frequently applied to their cages to prevent the fish from being eaten by predators. When the fish are mature, they are carefully harvested and processed.
Other cultivated freshwater fish include channel catfish and the common carp. Saltwater or brackish (slightly salty) water species frequently cultivated include salmon and trout. Varieties of these are Atlantic salmon, Pacific salmon, and brown trout.
Invertebrates are animals that lack a backbone or spinal column. The most common aquatic invertebrates cultivated around the world are species of oysters and mussels. In Asia, many species of oriental shrimps are bred, along with giant freshwater prawn. In Europe and North America, lobsters and various species of crayfishes are also cultivated.
Environmental impacts of aquaculture
Although aquaculture provides nutritious, high-quality foods for humans, it also severely harms the environment. When natural ecosystems (communities of plants and animals) such as tropical mangrove forests are turned into aquacultural systems, for instance, many native species in those ecosystems are displaced. Any remaining native species and the surrounding waters then face the threat of contamination from the drugs and toxic chemicals used in aquacultural management.
"Aquaculture." UXL Encyclopedia of Science. . Encyclopedia.com. (November 22, 2017). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/aquaculture
"Aquaculture." UXL Encyclopedia of Science. . Retrieved November 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/aquaculture
aquaculture, the raising and harvesting of fresh- and saltwater plants and animals. The most economically important form of aquaculture is fish farming, an industry that accounts for an ever increasing share of world fisheries production. Formerly a business for small farms, it is now also pursued by large agribusinesses, and by the early 2000s it had become almost as significant a source of fish as the as wild fisheries.
Successful aquaculture takes into consideration the biology of the aquatic species (feeding, water flow and temperature needs, disease prevention) and engineering design (water source and water quality study, pond and tank containment systems, water filtration and aeration) as well as issues pertinent to any business. Common products of aquaculture are catfish, tilapia (St. Peter's fish), trout, crawfish, oysters, shrimp, and salmon, and tropical fish for aquariums. Caviar from farm-raised sturgeon is one of the more expensive and exotic aquacultural products. Some are raised in huge freshwater tanks or ponds; others require the running water of rivers or streams. Saltwater species are often raised in saltwater ponds, in enclosed bays, or in pens placed in coastal or deeper sea waters.
There are potential environmental problems associated with aquaculture. Most of the fish that are raised are genetically altered or hybridized for quick growth. If they escape into the wild, they compete against and can crowd out smaller or less voracious native fish. Confined fish can become a breeding ground for diseases or pests, which can be transmitted in some cases to wild fish; confinement also makes the fish more suspectible to attacks by some naturally occurring pests, such as some species of jellyfish, that would be less likely to trouble dispersed wild fish. In addition, the large amounts of water that are used in aquaculture become laden with fish feces and unconsumed food that, if not removed through treatment or used as agricultural fertilizer, can add injurious amounts of nitrogen and phosphorus to a river or stream when the water is returned to it. Development of improved recirculating-tank technologies, however, may lead to a reduction in such pollution threats, as well as the spread of aquaculture to areas where large volumes of water are not available in the environment (see also aquaponics).
The practice of aquaculture dates back to 1000 BC in China. It is growing worldwide, in part in response to overfishing and the deterioration of the world's fisheries and concerns about the effects of pollution on seafood. In the United States, aquaculture is also a response to the increased demand for fish and shellfish as a result of changes in the nation's eating habits.
See M. Landau, Introduction to Aquaculture (1992).
"aquaculture." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (November 22, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/aquaculture
"aquaculture." The Columbia Encyclopedia, 6th ed.. . Retrieved November 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/aquaculture
aq·ua·cul·ture / ˈäkwəˌkəlchər; ˈak-/ • n. Bot. the rearing of aquatic animals or the cultivation of aquatic plants for food.
"aquaculture." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (November 22, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/aquaculture-0
"aquaculture." The Oxford Pocket Dictionary of Current English. . Retrieved November 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/aquaculture-0
"aquaculture." Oxford Dictionary of Rhymes. . Encyclopedia.com. (November 22, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/aquaculture
"aquaculture." Oxford Dictionary of Rhymes. . Retrieved November 22, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/aquaculture