Combined effects of water temperature and salinity on growth and feed utilization of juvenile Nile tilapia Oreochromis niloticus (Linneaus)

Juvenile Nile tilapia, Oreochromis niloticus (Linneaus) (average weight 4.60 to 4.83 g) were raised in 36 75-1 glass tanks at a stocking density of 15 fish per tank and fed a 50% protein diet for 56 days. Combined effects of temperature (24, 28, and 32°C) and salinity (0, 8, 12, and 16 g l^-1) on growth and feed utilization under a 12L:12D photoperiod were studied. Significant (P < 0.05) effects of temperature, salinity, and their interaction on growth were observed. Final mean weights were significantly (P < 0.05) higher at 32 and 28°C than 24°C at 12 g l^-1 salinity, where fish increased their weights seven-fold and four-fold, respectively. Feed conversion efficiencies and protein efficiency ratios were highest at 32°C and 8 g l^-1 salinity, and lowest at 28°C and 16 g l^-1 salinity. At all salinities, growth increased with temperature, but at all temperatures an increase in salinity generally inhibited growth. At 32°C and 16 g l^-1 salinity, fish developed body lesions. The study suggested that growth rates of juvenile O. niloticus may be comparably high at 28 or 32°C in waters of 0 and 8 g l^-1 salinity.