Lala I.P. Ray


Lala I.P. Ray, P.K.Panigrahi, B. C. Mal

Water is a crux in the life of all biological species. Aquaculture, which depends predominantly on water, regular monitoring water quality is given the most importance. An attempt was made at Indian Institute of Technology, Kharagpur, West Bengal, India during 2006-07 to study the response of the growth of Indian Major Carps (IMC) semi intensively cultured in polythene lined ponds. Nine ponds were stocked with IMC at stocking densities of 2.0, 3.5 and 5.0 numbers per square meter. The pond water quality was measured at regular interval to determine the levels of NO3, NO2, NH3 and PO4 pollution. Physio-chemical parameters such as temperature, pH, dissolved oxygen, organic carbon were also monitored along with the above critical nutrients. The average water temperature, dissolved oxygen, and pH during culture period were 1532.5C, 6.78.6 ppm, 3.17.8 ppm and 6.58.0 respectively. Nutrients like Total Ammonium Nitrogen (TAN), Nitrate-N, Nitrite-N and orthophosphate-P ranged between 0.2 to 1.2 ppm, 0.1-0.7 ppm, 0.02-0.1 ppm and 0.05-0.4 ppm respectively. Water exchange interval varied between 30 to 42 days for different stocking densities. Nutrient concentration initially increased with time until the water was exchanged. The exchange of water from the pond was carried out before nutrient concentrations reached the critical values. The fluctuation of nutrients in the pond water with higher stocking density (STD-3.5 and 5.0) was higher as compared to the lower stocking density (STD-2.0). The biomass increases with the increase stocking density but water exchange is needed. In this paper an attempt has been made to highlight the variation of important water quality parameters during a perennial culture period and its management by water exchange.

Key words: Water quality, IMC, stocking densities, water exchange