Common names : English - mrigal; Bengali-mirka, mrigal; Punjabi-nain; Burmese - nga-gyin

History of use : The mrigal (Cirrhinus cirrhosus) is the most widely farmed species among the Indian major carps of the Indo-Gangetic floodplains of Bangladesh, India and Pakistan. It also found in the rivers of Myanmar that drain into the Bay of Bengal. It is an important component of carp polyculture throughout South Asia. It was introduced for aquaculture, together with catla (Catla catla) and rohu (Labeo rohita), to other areas of India beyond its natural range in the early 1940's and in the 1950's and 1960's to other Asian countries (Jhingran 1982).

Production Statistics : There are no reliable statistics on production of mrigal from aquaculture.

Where farmed : Region - South and Southeast Asia, FAO Area - 04, Asia, Inland.

Countries : Bangladesh, Cambodia, India, Laos, Malaysia, Mauritius, Myanmar, Nepal, Pakistan, Sri Lanka and Vietnam.

Climate and environmental tolerance : Tropics, hardy, can tolerate low oxygen conditions and salinity levels of 5 ppt; minimum tolerable temperature, 140C; reproduces between 27 - 310C.

Current farming methods: Originally, mrigal seed for aquaculture were collected from floodplain rivers or bred by simulating riverine conditions in special ponds called dry bundhs.). Since 1957, induced breeding technology and large hatcheries have facilitated mass production of seed: for a review of methods, see Jhingran and Pullin (1988). Mrigal is one of the easiest of the major carps to breed in captivity.

The postlarvae are called renu, dhani or jeera in Bengali and are also commonly called 'spawn'. Postlarvae are usually stocked directly into nursery ponds, raised to advanced fry or fingerlings and then transferred to larger waterbodies. In Bangladesh, mixed postlarvae of mrigal, catla and rohu are stocked in large open waterbodies (haors and beels), from which the fish disperse over vast expanses of water during the annual floods.

Mrigal attain first maturity when about two years old (800 - 1,200 g) and spawn during the south-west monsoon. The main spawning period is June to August. In hatcheries, the same fish can spawn two to three times, early in the season. They lose condition towards the end of the season. The fecundity of mrigal ranges from 100,000 to 200,000 eggs/kg body weight (Jhingran and Khan 1979).

For induced spawning, two injections of crude carp pituitary gland (2-3 mg and 5-8 mg/kg) are given to a female at an interval of 4-6 hrs, as against only one (2-3 mg/kg) to males at the time of the second injection to the female. a female and two males in a running water spawning task should then spawn within six hours. If spawning has not taken place, the female is stripped and the eggs fertilized with semen stripped from males. The fertilized eggs hatch after 18-24 hrs depending upon the water temperature. Optimum temperature for spawning and hatching is 280C (Chaudhuri 1963). Jhingran and Pullin (1988) have reviewed the use of materials other than carp pituitary, for induced spawning.

Nursery ponds are prepared by liming and fertilization with cover or poultry manure, to produce zooplankton (especially rotifers and small claducerans). Before stocking the nursery ponds the predators of postlarvae, especially copepods and insects, are controlled with appropriate chemicals (Jhingran and Pullin 1988). Postlarvae are stocked at 5 million/ha and are given supplementary feed in the form of a fine powder comprising a 1:1 mixture of groundnut/mustard oil cake and rice or wheat bran. This is given daily at two, three and four times the weight of postlarvae stocked, increasing the ration at five days intervals. The postlarvae grow to about 25 mm in 15 days, with survival around 70%.

The fry are raised in larger rearing ponds which are fertilized in a similar manner to nursery ponds and then normally stocked as part of a combination of catla, rohu and mrigal. The total stocking rate in rearing ponds is usually around 100,00 - 125,000 fry/ha, of which 30-40% are mrigal. Mrigal is a bottom feeder and consumes mainly detritus and decayed vegetation, along with some plankton (20-25%).

Growout ponds (0.2 - 5.0 ha) are stocked with mrigal fingerlings at 10-35% of the total stocking density density depending upon the species mix. In polyculture of Indian major carps (catla, rohu and mrigal), mrigal are normally 30-40% of the population but this is reduced to 10-15% when common carp are included. Growout ponds are also prepared initially by liming and fertilization with periodic fertilization (organic and inorganic) thereafter. Mrigal normally registers better growth than rohu in ponds that have rich bottom feeding or when supplementary feed is provided regularly. In sewage-fed ponds, mrigal attain a weight of about 1 kg in 6 months.

Several intergeneric hybrids of Indian major carps have been produced in attempts to obtain faster-growing fish for aquaculture. The best cross so far is that between female mrigal and male rohu, called mrighu. It has a smaller head than rohu and a body deeper than both parents. It is also fertile. Such hybrids are also commonly available in the seed from dry bundhs (Tripathi 1992).

Processing and marketing : Mrigal is a tasty fish, despite its fine bones. It has a good market wherever it is farmed or fished. It is marketed either fresh or packed with ice.

Likely future trends : Mrigal will continue to be a very important species in carp polyculture in Asia. Monoculture of mrigal is not known at present, but the availability of improved genetic material (such as that being developed in Vietnam) may lead to the development of cage, pen, running water, and closed recirculatory systems, using mrigal alone. Mrigal is also a good fish for sewage-fed ponds, where the abundance of natural food almost high density stocking.

References :

Chaudhuri, H. 1963. Induced spawning of Indian carps. Proc. Nat. Inst. Sci. India (B), 29:478-87.

Jhingran, V.G. 1982. Fish and Fisheries of India. Hindustan Publishing Corporation (India), Delhi. 666p.

Jhingran, V.G. and H.A. Khan. 1979. Synopsis of biological data on the mrigal, Cirrhinus mrigala (Hamilton, 1822). FAO Fish. Synop. 120 : 78p.

Jhingran, V.G. and R.S.V. Pullin. 1988. A hatchery manual for the common, Chinese and Indian major carps. ICLARM Studies and Reviews 11. Asian Development Bank and ICLARM, Manila, Philippines. 191 p.

Roberts, T.R. 1997. Systematic revision of the tropical Asian labeoin Cyprinid Fish Genus Cirrhinus, with descriptions of new species and biological observations on C. lobatus. Nat. Hist. Bull., Siam Soc. 45: 171-203.

Tripathi, S.D. 1992. Three decades of research on carp hybridisation in India, p 00 - 00, In Symposium on Zoological Research in Relation to Man and Environment, 1 - 4 March. Zoological Society, Calcutta, India.

S. D. Tripathi