A Thesis submitted in partial fulfilment of the requirements for the degree of Master of Science, School of Environment, Resources and Development

Thesis (M.Sc.) - Asian Institute of Technology, 1988

Biological assessment of carp polyculture (bighead carp, Aristichthys nobilis; rohu, Labeo rohita; and mrigal, Cirrhinus mrigala) was conducted in eight 200m2 earth ponds for three months. Four treatments: control with no inputs; cow manure; cow manure plus urea and triple superphosphate (TSP>; cow manure urea and TSP plus supplementary feed, were used with two replications for each treatment. Extrapolated gross and net yields of 3364 and 3274 kg/ha/yr were obtained, respectively from ponds with the highest inputs: cow manure, inorganic fertilizer and supplementary feed. The lowest yield was 640 kg/ha/yr from the control ponds. The computed production almost doubled from one treatment to the next. Bighead carp, mrigal and rates during the beginning, respectively with close concentrations of zooplankton, the study. rohu exhibited the highest growth middle and end of the experiment, correlations to the highest benthos and phytoplankton during The moisture, protein and ash contents of fish were higher with lower input levels and decreased with the addition of nutritional inputs. The crude fat content of fish was higher before stocking and was inversely related to moisture, protein and ash contents. Economic assessment revealed that the yield obtained from the treatment receiving organic and inorganic fertilizers as pond inputs had a positive gross margin of 10t500 Baht/ha/yr whereas those from the other treatments were negative . The productive potential of carp polyculture is promising ~nd higher ~reduction may be obtainable by better stock manipulation and rational use of pond inputs.