Tilapia cage culture in Dokgrai reservoir, Rayong Province [Thailand]
1993
Sompong Hiranwat | Boonsong Sricharoendham | Renu Pitipornchai (Department of Fisheries, Bangkok (Thailand). National Inland Fisheries Inst.)
Fish growth rate and survival rate were inversely related to stocking density. There were significant (p0.05) differences in final mean weight (375, 326, 310 g) and daily weight gain (2.88, 2.54, 2.37 g/day) among the three stocking densities. Survival rate of fish at low density (94.8 %) was significantly (p0.05) higher than the other two densities (89.3, 87.6 %). However, there was no significant difference in food conversion ratio (1.32, 1.39, 1.40) among treatments. The net yields (139, 228, 316 g/cubic m/day) increased logarithmically with increasing stocking density. Using gross marginal analysis, the economic results showed that profit from bulk selling of fish at high density was higher than those of the other two densities. In contrast, yield from low density culture gave higher profit when the fish were graded before selling. The income from sells of graded fish from low density culture gave the highest rate of return to all variable costs (12.27 %) and to labour (176.92 Baht/man-day). The lowest break-even price was 19.34 Baht/kg for the short run and 21.34 Baht/kg for the long run operation. The partial budget analysis showed that if the tilapia price was stable and inputs limited, increasing the stocking density would not be economically practicable.
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