Growth performance, total fish yield and economical evaluation of the grey mullet Mugil cephalus (L.) at different stocking densities were compared in monoculture system without any supplementary feeding. Four stocking densities at rate of 1050, 1400, 2100 and 4200 fish/feddan (0.42 ha) for treatments, T1, T2, T3 and T4 respectively, were carried out in eight freshwater earthen ponds. Ponds were fertilized with organic and inorganic fertilizers, (60 kg; chicken manure, 30 kg. super phosphate and 10.0kg urea per feddan biweekly). Results indicated that the main individual growth rate was highest for lower density and lowest for the higher density. Final body weight was 231.86, 182.82, 151.19 and 91.65 g /fish for T1, T2, T3 and T4 respectively, with significant difference (p<0.05).
Final body length, SGR (%), RGR (%), daily weight gain, survival rate, condition factor, economic evaluation and sensitivity analysis were discussed. Total fish production values at the end of experimental period (180 days) were 233.7, 236.8, 273.0 and 313.9 kg. / feddan (0.42 ha.) for T1, T2, T3 and T4 respectively.
It could be concluded that treatment (T1) that received the lowest stocking density at the rate of 1050 grey mullet Mugil cephalus fingerlings per feddan (0.42 ha.), without any supplementary food, and cultured for 180 days in monoculture system, had the highest net return and rate of return, followed by T2 and T3, which can reduce the risk for the farmer in the event of unexpected fall in market price or production or increasing of costs.