The Efficacy of the Steroid Hormone, 17α-Methyltestosterone and Semi Flow-Through Culture System as Growth Promoters and Reproduction Inhibitors of Nile Tilapia ( O. niloticus ) Fed Two Feed Type

A total of 1200 sex reversed and mixed sex Oreochromis niloticus fry were reared in twelve circular fibre glass tanks, each with capacity of 3.08m 3 of water at a nominal flow rate of 2 L/min in a semi flow-through culture system to determine the efficacy of the steroid hormone and the culture system as growth promoters and reproduction inhibitors of O. niloticus . The experimental fishes at a stocking density of 100 fish per tank were fed two feed type (Coppens and Farm Produced Feed) and cultured for 24 weeks in which physico-chemical parameters were taken and growth performance was evaluated. The water quality parameters recorded (25.89-26.11℃, 6.80-6.82, 10.88-10.96 mg/L, 1.59-1.63 mg/L, and 0.01-0.02 mg/L for water temperature, water pH, dissolved oxygen, total ammonia nitrogen and unionized ammonia respectively) among all the treatments revealed that all tested physical and chemical parameters were within the permissible levels required for tilapia growth. No record of spawning activity or fry was observed in any of the fibre glass tanks throughout the culture period of 24 weeks thus suggesting the adequacy of this culture method for population control. Overall growth parameters were better in the sex reversed fishes in Treatments II and IV compared to the mixed sex fishes in Treatments I and III as the sex reversed fishes recorded the best average body weight gain, daily weight gain, average final weight gain as well as highest total fish production. Data generated from this experiment asserted that intensive culture of O. niloticus in a semi flow-through system is a successful culture system of controlling excessive reproduction of O. niloticus and also suggested that sex reversed treatments (II, IV) which are able to grow faster than typical mixed sex populations is ideal for the rapid growth rates of tilapia.