Aquaculture Crsp 22nd Annual Technical Report

A feeding trial was conducted towards optimization of feeding regimes for semi-intensive culture of Mozambique tilapia in earthen ponds in order to improve pond and effluent water quality, and reduce feeding cost. Fifty Mozambique tilapia fingerlings with an average weight of 17.8 ± 1.6 g were stocked in each of the 40 hapas. The experimental layout consisted of five feeding treatments of 20, 40, 60, 80, and 100% of apparent satiation with 8 replicates each. Fish were fed three times a day for 111 days. Specific growth rate (SGR) and feed conversion ratio (FCR) were used to measure the response to the various feeding regimes. Results were analyzed at three separate periods: at days 27, 55, and 111. At 27 and 55 days no significant improvement in FCR and SGR were observed at feeding levels above levels 60 and 80%, respectively. At 111 days, no significant difference in SGR was observed at feeding levels of 60% and above. This is an indication that 60% is the optimum feeding management regime. Natural food intakes calculated based on SGR and FCR were 0.34, 0.29, and 0.20% of body weight per day at 27, 55, and 111 days, respectively. Results from water quality analyses sampled fortnightly indicated no significant difference between the ponds. Analyses for correlations between production performance parameters and water quality parameters provided a regression equation to predict the natural food intake at specific water quality parameters, viz. Natural food intake (expressed as percentage of bodyweight per day) = 27.2 – 0.0962 morning measured oxygen – 0.0328 conductivity – 0.911 pH + 13.0 ammonianitrogen – 2.52 nitrate + 41.2 nitrite – 7.72 phosphate + 0.337 TSS (R2 = 80.9, P = 0.000). These results may provide useful data to quantify the utilization of natural pond productivity in the feeding management of Mozambique tilapia.