OBSERVATIONS ON THE EFFECTS OF WATER EXCHANGE-RATE ON THE GROWTH-RATE OF OREOCHROMIS-MOSSAMBICUS (PETERS) .2. JUVENILE FISH OVER THE 1ST 60 DAYS AFTER HATCHING

Larvae were stocked at different densities in fibreglass tanks with 1 500 1 capacity for a period of 60 d after hatching. Different water flow rates were used to establish the relationship between water used and growth (production) and the effect of different stocking densities on growth. A flow-through system to waste was used to prevent an accumulation of growth-limiting substances in the water. A significant positive correlation of r=0.95 (p<0.001) between water exchange rate and growth rate was obtained with juvenile Oreochromis mossambicus. A positive correlation of r=0.82 (p=0.001) was also obtained between total water used per fish and the mean mass of the fingerlings at the end of the 60 d period. An insignificant correlation of r=0.59 (p>0.05) was obtained between stocking density and water exchange rate.