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Abstract
A 180-d trial was done to evaluate the effect of stocking different ratios of Nile Tilapia Oreochromis niloticus, Striped Mullet Mugil cephalus, and Thinlip Grey Mullet Liza ramada on production and economic return in brackish-water ponds. The trial was conducted in twelve 3,000-m2 earthen ponds with four treatments (3 ponds/treatment): Nile Tilapia alone (100% Nile Tilapia, monoculture group [MG]); 75% Nile Tilapia and 25% Thinlip Grey Mullet (polyculture group 1 [PG1]); 75% Nile Tilapia, 12.5% Thinlip Grey Mullet, and 12.5% Striped Mullet (PG2); and 75% Nile Tilapia and 25% Striped Mullet (PG3). Fish were fed a commercial diet containing 25% crude protein twice per day. The efficiency of feed utilization was determined in terms of feed conversion ratio (FCR; feed intake/weight gain). Polyculture group 3 had the best FCR, whereas the FCR results did not differ significantly among the MG, PG1, and PG2 treatments. In addition, PG3 had the highest total yield (3,350.3 kg/pond), followed in descending order by PG2 (3,234.4 kg/pond), PG1 (3,078.4 kg/pond), and MG (2,856.3 kg/pond). The PG3 treatment achieved the highest net financial return, followed by PG2, PG1, and MG. This study indicates that tilapia–mullet polyculture may improve the efficiency with which natural food resources are used within the system, resulting in better environmental quality, system sustainability, feed utilization, and net financial return.
Received March 14, 2013; accepted July 2, 2013
ACKNOWLEDGMENTS
We thank the students and staff of Cairo University's Fish Nutrition Research Unit for their assistance with laboratory and field work during the research.