Effects of photoperiod on the performance of farmed Nile tilapia Oreochromis niloticus: I. Growth, feed utilization efficiency and survival of fry and fingerlings

Abstract

The effect of photoperiod on survival, growth rates and feed utilization efficiency of Nile tilapia ( Oreochromis niloticus L.) fry and fingerlings was investigated in two consecutive experiments. In Experiment 1, triplicate groups of 75 swim-up fry (0.02 g) were stocked in 25-l fiberglass tanks, in recirculating indoor system. The fish were exposed to four photoperiod (light:dark, L:D) cycles (24L:0D, 18L:6D, 12L:12D and 6L:18D). Light intensity was kept constant at 2500 lx throughout the study. The fish were fed a tilapia diet (35% crude protein, 350 kcal GE/100 g) at a daily rate of 30–20% BW, three times a day for 60 days. The best weight gain, specific growth rate (SGR), feed efficiency and fish survival were achieved at 24L:0D and 18L:6D, without significant differences between them. Fry performance was significantly retarded by reducing light phase (12L:12D and 6L:18D). In the second experiment, triplicate groups of 40 fingerlings (mixed sexes) (2.4±0.05 g) were stocked in 0.4-m 3 fiberglass tanks and exposed to the same light intensity and photoperiod cycles used in Experiment 1. The fish were also fed the same diet used in Experiment 1, at 5–4% BW/day, three times a day for 90 days. The fish performance was not significantly affected by photoperiods. These results revealed that Nile tilapia fry, but not fingerlings, reared in indoor, recirculating systems are significantly affected by photoperiod. The insignificant difference in fry performance between 24L:0D and 18L:6D groups suggests that a 18L:6D cycle be used in case of larval rearing, while shorter light phases are suggested for optimal growth, feed efficiency and survival of fish fingerlings, taking into consideration the cost of electricity.