Effect of stocking rates of Nile tilapia (Oreochromis niloticus L.) and grey mullet (Mugil cephalus L.) on their performance in polyculture earthen ponds
2005
Abou-Zaid, Ramadhan M. | Abdel-Maqssoud, Abd-Allah M. | Aly, Ahmad A.
A growing experiment was conducted, for 150 days started on 20/6/2003 to evaluate the effect of four stocking rates of Nile tilapia and grey mullet fish in polyculture earthen ponds, rearing systems, on their growth performance, production and economical efficiencies. Stocked rates were; 6000 fish (5 tilapia: 1 mullet)/feddan, T,; 7700 fish (10 tilapia: 1 mullet)/ feddan, T2; 8000 fish (3 tilapia: 1 mullet)/ feddan, T3i and 11000 fish (10 tilapia: 1 mullet)/ feddan, T4. Eight ponds (2 ponds/treatment) each of 1 feddan area (4200 m), 1.2 m depth were supplied with fresh water. Fish were fed twice daily on a supplementary diet (25% CP, 4.45 kcal/g, GE) at a rate of 3% from their biomass. The results revealed that; water quality parameters didn't show significant differences among treatments and they were within the acceptable limits. Harvesting body weight, total gain, daily gain and specific growth rate of fish were affected by stocking rates. T he highest values for tilapia and mullet were obtained with T2 followed by T3, T, and T,, respectively. Survival rates of tilapia ranged between 92 to 980/9 and ranged between 92 to 96% for mullet. Body mass of tilapia at harvesting and the net production per feddan were higher with T4 than that of T2, T3 and T,. respectively. And these measures for mullet were higher with T3 than that of T2, T, and T4i respectively. While the total biomass and net production per pond were higher with T, than those of T3, T2 and T, respectively. The economical efficiency was in favor of T3 more than T4 (regarding net returns/total costs %). Key words: Nile tilapia, grey mullet, polycuture, stocking rate, growth performance, production and economical efficiencies.
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