Abstract
One year pond fertilization trial was conducted with the rearing of major carps such as Calla calla, Labeo rollita and Cirrhina nuigala, so as to test cow-dung treatment with control (no additives). Based on its nitrogen contents cow-dung was added at the rate of 0.10 g nitrogen per 100 g of wet fish weight daily. The effect of treatment on fish weight, fork and total length increase was highly significant. However, differences among species in gaining weights were non-significant between Labeo rohita and Cirrhina mrigala. The response of treated and control ponds towards planktonic productivity, phyto- and zooplankton populations and phytoplankton/zooplankton ratios were significantly different. Increase in fish yield and nitrogen incorporation efficiency of fish were positively and significantly correlated with water temperature and planktonic productivity in both the ponds. Planktonic biomass was positively and significantly correlated with water temperature also. The net fish yields of 2928.54 and 767.29 kg/ha/year of major carps were obtained from treated and control ponds, respectively.
