Anaesthetic Effect of Ocimum gratissimum Extract on Oreochromis niloticus Juveniles

This study examined the use of O. gratissimum oil as anesthetic in O. niloticus juveniles. Ten fish with average weight (36.0 ± 1.6 g) were allocated to five rectangular tanks (50 × 34 × 27 cm) containing 35 litres using completely randomized design in triplicates and a control. The experimental treatment (dose) were prepared using 1:20 of extract oil and ethanol in five concentrations (0, 20, 40, 60, 80 and 100 mg/l) and exposed for twenty minutes before transferred in to recovery tanks. The data obtained were analyzed using descriptive statistics, ANOVA, Duncan multiple range test to separate the means and regression analysis. The results show that concentration of 100 mg/l anesthetized highest number of fish (10.00 ± 0.00) while the least was observed in 20 mg/l (1.67 ± 1.53) within three minutes. Fastest recovery was observed in fish anesthetized with the 20 mg/l of oil while 100mg/l had the least mean recovered fish (1.00 ± 1.00) within three minutes. There are relationships among induction time (R2=0.892), concentration of oil and recovery time (R2=0.905). However, 60 mg/l is considered adequate for the anesthetic of O. niloticus.