THE EFFECTS OF TEMPERATURE AND SALINITY ON GROWTH AND FEED-UTILIZATION OF JUVENILE, SEX-REVERSED MALE FLORIDA RED TILAPIA CULTURED IN A RECIRCULATING SYSTEM

In two experiments, juvenile, sex-reversed male Florida red tilapia (a vg. wt. = 0.56-1.20 g) were stocked into forty-two 0.33-m3 indoor tank s at a density of 74 fish m-3 and growth and feed utilization compared for 54-58 days at temperatures of 22, 27 and 32-degrees-C and at sali nities of 0 and 18 ppt (experiment one) or at 18 and 36 ppt (experimen t two) under a 12 L:12 D photoperiod. Fish were fed twice daily to sat iation a 32% protein diet. Each treatment consisted of seven replicate tanks supported by a recirculating water system. While growth rates g enerally increased with increasing temperature and were markedly lower at 22-degrees-C than at 27 and 32-degrees-C, salinity modified the ef fects of temperature on growth: at 0 ppt, feed consumption and growth reached a maximum at 27-degrees-C, while at 18 and 36 ppt, consumption and growth were highest at 32-degrees-C. Under all temperatures, feed consumption and growth were higher at 18 ppt than at 0 or 36 ppt. The results suggested that, in freshwater, heating water to temperatures above 27-degrees-C is not justifiable, while at 18 or 36 ppt, heating water to 32-degrees-C can maximize growth rates without lowering growt h efficiency. An important advantage of brackishwater (18 ppt) rearing under conditions of suboptimum temperatures was further suggested.