Preliminary Observations On The Relative Growth And Production Of Tilapia Species Cultured In Cages At Three Stocking Densities
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Relative growth rate and productivity of Tilapia species (T. nilotica and T. galilaea) were studied for fish reared in cages in the Serow fish farm, Egypt. Both species were reared under three different stocking densities 100, 200 and 300 fish/ in^The fish were fed daily with supplementary food of 20% protein content at 5% of the stock weight-Control cages of each type of fish at the lowest stocking density were maintained without supplementary feeding. Results indicated that the individual growth rate of both species decreased with increased stocking densities with a best aggregate stocking rate of 200 fish/m3 for both species.The maximum production rates of 32.0 and 17.4 kg/m^six months and final average size of 178.7 and 108.7 gm/fish were recorded for T.nilotica and T. galilaea respectively.The range of food conversion ratios for T. nilotica were between 2.83 and 3.57 while for T. galilaea were 3.88 and 5.20 with efficiency decreasing with increasing stocking density. Survival rates at the three densities ranged between 97.5—100% indicating that Tilapia species are able to withstand a certain degree of crowding, which is an important characteristic in the intensive culture of the fish.