Evaluation of Acute Toxicity and Anaesthetic Efficacy of Scent Leaf (Ocimum gratissimum) in African Catfish (Clarias gariepinus) Juveniles

This study assessed the acute toxicity and anaesthetic efficacy of scent leaf (Ocimum gratissimum) powder on Clarias gariepinus juveniles. Four hundred and fifty juveniles of C. gariepinus of average weight and length, 24.25g ± 4.25SD and 27.60cm ± 3.75SD were used for the study. Toxicity bioassay was conducted with 100, 150, 200, 250mg/l and 0.00mg/l as control at the rate of 10 fish per tank in triplicates for 96 hours. Anaesthetic bioassay was conducted with 100, 120, 140, 160 and 180mg/l of scent leaf with10 fish in each tank in triplicates for 30 min. fish mortality data was collected against the durations in the acute toxicity test while data on time of anaesthesia and recovery at various stages were also noted and recorded. The Trimmed Spearman’s Karber method was used to estimate the lethal concentration (LC) and mean lethal concentration (MLT) while data on anaesthesia and recovery time were subjected to analysis of variance followed by Turkeys test for significant differences at 5%. The LC₅₀ and maximum allowable toxicants concentration values were observed to decrease from 12 to 96 hour. The 96hrLC₅₀ value was estimated as 203.02mg/l which was observed as high. The MLT₅₀ values decrease for 164.36 hours in 100mg/l to 126.34 hours in 250mg/l. water quality parameters did not vary significantly (P > 0.05) from those of control. Deep anaesthesia (A3) was achieve in all the concentrations except in 100mg/l which only achieve sedation (stage A1) and with no mortality observed during the experiment. The shortest time for deep anaesthesia (2.25 min) was observed at the concentration of 180mg/l. the shortest time (4.08 min) to regain equilibrium and swim normally was observed in 120mg/l. Both anaesthesia and recovery time were observed to be dependent on concentration. Scent leaf was effective to anaesthetize C. gariepinus juveniles in routine management procedures.   This study therefore recommend the use of scent leaf at 160mg/l as effective dose when considering optimal induction and recovery time for sustainable aquaculture.

Citation: Okey, I. B1. and Igiri, M. R. (2021) Evaluation of Acute Toxicity and Anaesthetic Efficacy of Scent Leaf (Ocimum gratissimum) in African Catfish (Clarias gariepinus) Juveniles, International Journal of Fisheries and Aquaculture Research, Vol.7, No.2, pp.1-19

Keywords: immobilization, lethal concentration, recovery, scent leaf and African catfish