AQUACULTURE

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AQUACULTURE:

AQUACULTURE Made By: Nikhil Aggarwal

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Aquaculture, also known as aqua farming , is the farming of aquatic organisms such as fish, crustaceans,  molluscs  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. The reported output from global aquaculture operations would supply one half of the fish and shellfish that is directly consumed by humans. Further, in current aquaculture practice, products from several pounds of wild fish are used to produce one pound of a piscivorous, fish like salmon. Particular kinds of aquaculture include fish farming, shrimp farming, oyster farming, alga culture (such as seaweed farming), and the cultivation of ornamental fish. Particular methods include aquaponics and Integrated multi-trophic aquaculture, both of which integrate fish farming and plant farming.

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The two main branches of aqua culture are: 1. Mari Culture 2. Fish Farming

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MariCulture Mari culture 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 Mari culture include: fish meal ,nutrient agar, jewellery (e.g. cultured pearls), and cosmetics .

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Fish Farming Fish farming is the principal form of aqua culture , while other methods may fall under Mari culture . Fish farming involves raising fish commercially in tanks or enclosures, usually for food. A facility that releases young (juvenile) fish into the wild for recreational fishing or to supplement a species' natural numbers is generally referred to as a fish hatchery. The most common fish species raised by fish farms are salmon , carp , tilapia , European sea bass , catfish and cod. There is an increasing demand for fish and fish protein, which has resulted in widespread overfishing in wild fisheries. Fish farming offers fish marketers another source. However, farming carnivorous fish , such as salmon , does not always reduce pressure on wild fisheries, since carnivorous farmed fish are usually fed fishmeal and fish oil extracted from wild forage fish. In this way, the salmon can consume in weight more wild fish than they weigh themselves .

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Major categories of fish aquaculture There are two kinds of aquaculture : 1. E xtensive aquaculture, based on local photosynthetical production 2.Intensive aquaculture , in which the fish are fed with external food supply.

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Extensive aquaculture Limiting for growth here is the available food supply by natural sources, commonly zooplankton feeding on pelagic algae or benthic animals, such as crustaceans and mollusks . Tilapia species filter feed directly on phytoplankton which makes higher production possible. The photosynthetic production can be increased by fertilizing the pond water with artificial fertilizer mixtures, such as potash , phosphorus nitrogen and micro-elements. Because most fish are carnivorous, they occupy a higher place in the trophic chain and therefore only a tiny fraction of primary photosynthetic production (typically 1%) will be converted into harvest-able fish. A second point of concern is the risk of algal blooms. When temperatures, nutrient supply and available sunlight are optimal for algal growth, algae multiply their biomass at an exponential rate, eventually leading to an exhaustion of available nutrients and a subsequent die-off. The decaying algal biomass will deplete the oxygen in the pond water because it blocks out the sun and pollutes it with organic and inorganic solutes (such as ammonium ions), which can (and frequently do) lead to massive loss of fish. Another option is to use a wetland system such as that of Veta La Palma. In order to tap all available food sources in the pond, the aqua culturist will choose fish species which occupy different places in the pond ecosystem, e.g., a filter algae feeder such as tilapia a benthic feeder such as carp or catfish and a zooplankton  feeder (various carps) or submerged weeds feeder such as grass carp

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Intensive aquaculture In intensive culture systems there is a decreased dependence on the availability of natural food and greater dependency on the use of commercial feeds. Densities of fish kept within such holding areas are limited by species tolerance, ability to grow at raised stocking densities and maintenance of environmental parameters rather than the production of a natural food supply. By contrast, fish production in extensive systems is based on the use of organic and inorganic fertilizers. Fertilization of ponds promotes the growth of simple plants which form the base of the food chain in the pond. Fish stocked in these ponds feed on phytoplankton, zooplankton, bottom-dwelling invertebrates and smaller fish. At its most effective, this type of production can be integrated with other types of crop or livestock production, using animal manure and agricultural by-products as sources to stimulate primary production. Semi-intensive aquaculture aims to increase the production of fish from pond systems beyond the level supported by food which is naturally available through the use of supplementary feeds. Supplementary feeds range from cereals and agricultural and fishery by-products to formulated feeds. Traditionally they are incomplete and would be inadequate as a sole source of food. Their function is to provide extra nutrients to complment those obtain from natural foods .

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Specific types of fish farms 1. Cage System - Fish cages are placed in lakes, bayous, ponds, rivers or oceans to contain and protect fish until they can be harvested. The method is also called "off-shore cultivation ’” when the cages are placed in the sea. They can be constructed of a wide variety of components. Fish are stocked in cages, artificially fed, and harvested when they reach market size. A few advantages of fish farming with cages are that many types of waters can be used (rivers, lakes, filled quarries, etc.), many types of fish can be raised, and fish farming can co-exist with sport fishing and other water uses. Cage farming of fishes in open seas is also gaining popularity. Concerns of disease, poaching, poor water quality, etc., lead some to believe that in general, pond systems are easier to manage and simpler to start. Also, past occurrences of cage-failures leading to escapes, have raised concern regarding the culture of non-native fish species in open-water cages. Even though the cage-industry has made numerous technological advances in cage construction in recent years, the concern for escapes remains valid.

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2. Composite fish culture - The Composite fish culture system is a technology developed in India by the Indian Council of Agricultural Research in the 1970s. In this system both local and imported fish species, a combination of five or six fish species is used in a single fish pond. These species are selected so that they do not compete for food among them having different types of food habitats . As a result the food available in all the parts of the pond is used. Fish used in this system include catla and silver carp which are surface feeders, rohu , a column feeder and mrigal and common carp which are bottom feeders. Other fish will also feed on the excreta of the common carp and this helps contribute to the efficiency of the system which in optimal conditions will produce 3000–6000 kg of fish per hectare per year .

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3.Classic fry farming -This is also called a "Flow through system" Trout and other sport fish are often raised from eggs to fry or fingerlings and then trucked to streams and released. Normally, the fry are raised in long, shallow concrete tanks, fed with fresh stream water. The fry receive commercial fish food in pellets. While not as efficient as the New Alchemists' method, it is also far simpler, and has been used for many years to stock streams with sport fish. European eel ( Anguilla) aqua culturalists procure a limited supply of glass eels, juvenile stages of the European eel which swim north from the Sargasso Sea breeding grounds, for their farms. The European eel is threatened with extinction because of the excessive catch of glass eels by Spanish fishermen and overfishing of adult eels in, e.g., the Dutch Ijsselmeer, Netherlands. As per 2005, no one has managed to breed the European eel in captivity. Some other special types are: 4. Integrated recycling systems 5. Irrigation ditch or pond systems

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Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats, purpose of the activities or a combination of the foregoing features ". The definition often includes a combination of fish and fishers in a region, the latter fishing for similar species with similar gear types . A fishery may involve the capture of wild fish or raising fish through fish farming or aquaculture. Directly or indirectly, the livelihood of over 500 million people in developing countries depends on fisheries and aquaculture. Overfishing, including the taking of fish beyond sustainable levels, is reducing fish stocks and employment in many world regions . Fisheries