46 December 2011 Vertical Expansion of Fish Culture A number of measures are now being employed by the fish farmers and entrepreneurs to increase production of fish: • Stocking of yearlings by stunting the growth of fish seed during first year, • Heavy stocking and multiple harvesting after the fish attain a size of 500 g, • Multiple stocking and multiple harvesting and • Use of aerators in the pond. Carp Culture in Andhra Pradesh The prevailing carp culture in Andhra Pradesh is completely different from that of the popular composite fish culture practices in India. A simplified two-species system in which rohu is dominant with 80-90 percent of the fish biomass and with catla a very profitable 10-20 percent. Production can be described as semi-intensive and indirectly integrated. It is a green water system with mainly local off-farm inputs: chicken manure and chemical fertilizers; supplemented with farmmixed de-oiled rice bran and oil cake. Sustainable annual production is 7.5-10 t/ha though 12.5-15 t/ha have been achieved but at increased risk of mass mortality. During 2001, about 5,000-6,000 farmers produced a total of 4,50,000 t of fish from 60,000 ha of ponds in the state alone. Problems and Suggestions Farmers are experiencing problems, especially the increasing costs of production, mainly because of the rising cost of fertilizers and supplemental feed and weather-related mass mortalities. Another problem is the fall in DO during the rainy season and during cloudy weather in general and during cool season foggy periods. Water quality problems occur during the hot season from April to June when there is limited water availability, especially in conjunction with high density culture, which may result in disease. Farmers also recognize the need for change, especially to farm new species. Problems such as feed costs can be overcome to some extent by utilizing a locally available cheap source of feed ingredients for feed preparation. Stocking the fish pond at optimum stocking density and using aerators during DO depletions that occur in the early morning and during periods of cloudy weather help farmers avoid mass mortalities. The culture techniques that are being practiced in Andhra Pradesh are good examples for the fish farmers and entrepreneurs in other parts of the country to follow to enhance their fish production so that the import of fish from other states is minimized. Farmers also earn some foreign exchange by exporting fish and other value-added fish products. Notes 1College of Fisheries, Central Agricultural University, Lembucherra, Tripura (W), India. *Correspondence: scmandal02atgmail.com, +919402169213 (M), +913812865291 (Fax). 2Laboratory of Aquaculture & Artemia Reference Center, Ghent University, Belgium. 3Central Institute of fisheries Education, Seven Bungalow, Versova, Mumbai-61, India. View of sluice gate in the pond to maintain water level. tivity and fish growth. Excess fertilization that could result in eutrophication should not take place. Harvesting. Harvesting is generally done at the end of the 1st year, when the fish attain average weight of 0.75 to 1.25 kg. Normally, a production of 4 to 5 t/ha can be obtained in a year. However, for the purpose of our economics, a production level of 3 t/ha/year may be considered. Harvesting of fish is done by partial dewatering and repeated netting. In some cases complete dewatering of ponds is also practiced. Catla catla in farmer’s pond after harvest. A haul of harvested fish from composite culture pond.
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