When selecting fish species suitable for farming, various important biological and economic factors need to be considered:
market price and demand (not when fish are produced for own consumption)
growth rate
ability to reproduce in captivity
simple culture of the young fish
match between available fish feeds and the food preference of the selected fish species
Although certain slow-growing species may be candidates for culture because of their market value, it is often difficult to make their culture profitable. It is better that they reach marketable size before they attain maturity, thus ensuring that most of the feed is used for muscle growth instead of reproduction. Early maturity, on the other hand, ensures easier availability of young fish.
Raising different fish species together in one pond (polyculture) will produce a higher fish production than from raising fish species separately (monoculture).
Monoculture
Only one fish species is raised in the pond. An advantage of monoculture is that, as there is only one fish species to consider with regard to food preference, it is easier to give certain supplementary feed to the fish. A disadvantage is the risk that a single disease may kill all the fish in the pond. Different fish species are usually susceptible to different diseases.
Polyculture
More than one fish species are raised in the fish pond. This way the various natural food resources in the pond are better utilised. Each fish species has a certain feed preference, which is related to the position of the fish in the pond (e.g. bottom-living or mid-water-living fish). For example, mud carp live mostly on the bottom of the pond and feed on mud and detritus (= dead material), which they find on the bottom. Tilapia, on the other hand, prefer the middle part of the pond. An example of a Chinese polyculture fish farming system is the culture of silver carp, bighead carp and grass carp together in one pond .
Most widely cultured species
Tilapia, catfish and carp are the most commonly cultured fish species in the tropics. Someother like bighead ,rohu,bhakur,,roopchanda ,pangas,etc are also cultured in local level.
Tilapia culture
Tilapias are a group of tropical freshwater fish species native to Africa and the Middle East. There are at least 77 known species of tilapia, of which Nile tilapia is the fastest growing one.
The stocking density of tilapia is 2/m2 and that of the predatory fish varies according to its voracity: 83 catfish of at least 30 cm in length per 100 m2 or 7 snakeheads of at least 25 cm in length per 100 m2 .
Catfish culture
Catfish belong to the order called Siluriformes, subdivided into various families, including the Ictaluridae, Pangasidae and Clariidae. This fish order consists of both marine and freshwater fish species found in most parts of the world.
Over 2000 different species have been recorded, of which over half are present in South America. Some catfish families and the areas of farming are: Ictaluridae; Channel catfish (Ictalurus punctatus) and blue catfish (Ictalurus furcatus) both farmed in the USA. Pangasiidae; Pangasius sutchi farmed in Thailand, Cambodia, Vietnam, Laos and India and Pangasius iarnaudi. Clariidae; Asian catfish (Clarias batrachus) and Clarias microcephalus farmed in Thailand and African catfish (Clarias gariepinus) farmed in Africa and Europe .
Carp culture
Carp belong to the freshwater family Cyprinidae. The family consists of 1600 different species of which only very few are important for fish farming. Farmed carp are divided into three groups: common carp, farmed in Europe, Asia and the Far East; Indian carps; and Chinese carps.
The common carp is a widely cultured, strictly freshwater fish (figure 33), which can reach a length of some 80 cm and a weight of 10 to 15 kg. The temperature range in which common carp live is from 1 to 40 °C. The fish starts growing at water temperatures above 13 °C and reproduce at temperatures above 18 °C, when the water flow is increased suddenly. Carp are usually mature after about 2 years (weighing 2 to 3 kg).
Fishes Cultured in India(most popular)
1. Carassius carassius:
It is commonly called as crucian carp or golden carp. It was brought to India from central Europe in 1874 and was first introduced by Maclvor in the Ooty Lake. Later on, it was transplanted to other places in Nilgiris and to Sunkesula fish farm of Andhra Pradesh. The purpose of its import is to use as food fish. These are fresh water river fish but survive and reproduce in confined water, too. In tropics, its breeding season extends throughout the year. Its growth rate is quite slow and attains a maximum length of 45 cm and a weight of 1.4 kg as recorded in Ooty Lake.
Gold carp feeds on insects, Cladocerans and Crustaceans. They attain sexual maturity in the first year of their life. The eggs remain attach to aquatic weeds till hatching. The culture of this fish is of little significance as its growth rate is low and the flesh is also not well relished. However, when it is cultured along with other species the yield increases. They help to control predators and weeds in the pond.
2. Ctenopharyngodon idella:
“Grass carp or white amur” is a native of flat land rivers of China and the middle and lower sections of the river Amur in Russia. In India it was introduced in 1959 at Cuttack (Orissa) for the sole purpose as food fish. After the successful hypophysation at the Cuttack, in 1962 the grass carp culture started at different parts of India and a gift consignment of grass carp fry was send to Philipines, Nepal and Burma in subsequent years.
Grass carp is a fresh water fish which can tolerate slightly brackish water. The body of an adult fish is elongated and slightly compressed with broad head. The upper jaw is slightly longer than the lower jaw. The barbels are absent. The dorsal fin is short. Body is dark grey dorsally with silvery belly. The scales are of moderate size. By the end of first year, the fish attains a length of about 120 mm and weight about 225-500 gm. After two years, these attain a length of 600 mm and weight between 1.8 to 2.3 kg. In about 4 years, a fish attains a weight of 4.5 kg to 7 kg or more.
Puntius javanicus:
It is commonly known as “Tawes”. It was brought о India from Indonesia in the year 1972 and was first introduced in the ponds of West Bengal.
Puntius breeds naturally all over the year, however it requires well oxygenated water. Owing to its not very familiar taste, it is not recommended for culture. Its Cultivation is done along with other carps in poly-culture system mainly to keep the aquatic weeds under control.
Osphronemus gouramy:
it is commonly known as “Gouramy”. Osphronemus gouramy is a native of fresh water ponds and streams of Indonesia, Thailand, Malaysia, Cambodia and Veitnam. Gouramy was brought to India from Java to Calcutta and then from Mauritius to Madras in 1916 Gourami is a fresh water fish of the tropical countries which do not survive and reproduce below 15° C. They may, however, survive in water with low oxygen content as they possess air breathing organs.
Incubation period is 36 hours. Newly hatched out larvae are transparent measuring 5.3 mm to 6 mm in length. Initially, they are without gills, mouth and fins. After 4th -5th day of hatching they start feeding. The fry feed on insect larvae, crustaceans, rotifers, infusorians and other coarse zoo-planktons. The adults are herbivorous feeding upon aquatic vegetation but in scarcity may become omnivorous.
Catla catla (Ham):
The species has the fastest rate of growth among the Indian major carps. In good nursery ponds, hatchlings of catla stocked at the rate of 1000000 to 1250000 per hectare, grow to a length of 20-25 mm in 15 days.
Catla attains maturity when about 2 years old. In 5 kg female, a total number of 4000000 ova were found which gives the fecundity to be 80 eggs/g body weights.
Labeo bata (ham):
It is a medium sized carp and attains a length of 60 cm. it is widely distributed in India and is often cultured with other major carps. When stocked at 1.5 lakhs/ha, the fish grows to a length of 25-32 mm in one month.
Cirrhina mrigala:
This species is widely cultured in India along with other carps. It grows fast and fry when stocked at 10 lakhs to 12.5 lakhs/ha grow to 25-30 mm in length in 15 days. Both the sexes mature when they are two years old. However induced bred specimen at Central Fisheries Research Institute, Cuttack become sexually mature in one year only.
Comments