World Aquaculture March 2019

WWW.WA S.ORG • WORLD AQUACULTURE • MARCH 2019 23 ( C O N T I N U E D O N P A G E 2 4 ) another air-breathing catfish species being cultured to a certain extent in swamps and derelict water bodies, especially in the eastern states. In recent years, attempts have been made to develop the culture of fishes like Pangasius pangasius, Pangasius sutchi, Oreochromis niloticus, Ompok pabda etc. Other finfish species of importance include climbing perch Anabas testudineus and murrels Channa striata and C . marulius . Among the freshwater prawns, the giant river prawn Macrobrachium rosenbergii is the most important species, followed by the monsoon river prawn M. malcolmsonii . Freshwater aquaculture activity has expanded in terms of areal coverage and intensity of operation, with farmers in Andhra Pradesh, Punjab, Haryana and Maharashtra taking up fish culture as a commercial farming enterprise. Of late, scientific carp farming is picking up in the northeastern states of India. With regards to the market, the main areas of freshwater fish consumption are in West Bengal, Bihar, Orissa and northeastern India. Non-conventional Freshwater Culture Systems  Sewage-fed fish culture and rice paddy-cum-fish culture are two important culture systems practiced in certain areas of the country; sewage-fed fish culture in bheries in West Bengal is an age-old practice. About 5,700 ha are currently being utilized for fish culture using the input of primary-treated sewage and produce over 7,000 t of fish per annum, mainly consisting of the major and minor carps. The culture system usually involves multiple stocking and multiple harvesting approaches, with harvest size usually in Fish cage farming (Photo: TNJFU). Red tilapia culture in commercial cages (Photo: TNJFU). Nursery raceways for shrimp culture (Photo: TNJFU). RAS-based commercial shrimp hatchery tanks (Photo: TNJFU). the range of 300-500 g and stocking densities of 7,000-10,000 of advanced fingerlings per ha are prescribed. Normally, multiple stocking and multiple harvesting is adopted and fishes are reared for 3-5 months, depending on the growth of the fishes to reach marketable size of 250-400 g. Paddy-cum-fish culture is undertaken in medium- to semi- deepwater rice paddy fields in lowland areas with fairly strong dykes to prevent the escape of cultivated fish during floods. Trenches and pond refuges in the paddy fields provide shelter for the fish. The modern concept of paddy-fish integration with rice-fish plots, digging of peripheral trenches, construction of dykes, nutrient utilization of pond refuges and sowing of improved varieties of rice and release of fish in trenches, have resulted in improved yields of rice and fish. Brackishwater Aquaculture In the domain of brackishwater aquaculture, a scientific approach to the traditional practice of trapping naturally bred fish and shrimps in coastal wetlands or manmade impoundments was carried out. Shrimp, seabass, milkfish and other freshwater species are produced in (low salinity) brackishwater aquaculture. Brackishwater aquaculture is mainly concentrated on the coasts of Andhra Pradesh, Tamil Nadu, Orissa and West Bengal. West Bengal and Gujarat have the largest production potential available. The brackishwater aquaculture sector is mainly dominated by production of the black tiger prawn Penaeus monodon , which