Efficacy of metomidate as anaesthetics in clarias gariepinus (Burchell, 1822) broodstock and its effects on water quality

Abstract

Anaesthetics are commonly used in aquaculture to minimize the incidence of stress in fish. The study assessed effects of metomidate as anaesthetics on induction and recovery time in male and female brood fish of Clarias gariepinus as well as on some water quality variables {pH, dissolved oxygen (DO), temperature, ammonia and nitrite}, following standard procedures. Thirty-six (36) brood C. gariepinus consisting of eighteen (18) gravid female (mean length 60.23 cm±0.36 and 2.64 kg ±19.36) and eighteen (18) matured male (mean length 58.12 cm ±0.47 and 1.98 kg ±45.11 were exposed to 0.00 (control), 2.00, 4.00, 6.00, 8.00 and 10.00 mg/L in triplicates. Results showed that induction time(s) in both sizes of exposed fish decreased (660.00±18.98 at 2.00 mg/L to 228.00±20.72 at 10.00 mg/L) as metomidate concentration increased, while the recovery time(s) increased as metomidate concentration increased (490.00±23.07 at 2.00 mg/L to 862.00±28.15 at 10.00 mg/L). The survival rates in male and female C.  gariepinus exposed to metomidate were 100.00 % (0.00 mg/L and 6.00 mg/L of metomidate). The results indicated that metomidate did not cause any significant change (p>0.05) in water quality variables in all exposure concentrations. A reduction in DO, (5.22±0.78 mg/L in the control to 4.96±1.16 at 10 mg/L anaesthetics concentration) and slight increase and decrease in ammonia (0.35±0.01 mg/L; 0.28±0.11 mg/L) and nitrite (0.02±0.01 mg/L; 0.03±0.01 mg/L) were observed at 6.00 to 10.00 mg/L of metomidate. The study therefore established 4.00 mg/L as ideal concentration for C. gariepinus exposure to metomidate for optimum production in aquaculture venture.