Toxicity Assessment of the Ethanolic Stem Bark Extracts of Ackee, Blighia sapida on the African Catfish, Clarias gariepinus

Acute toxicity effects of ethanolic stem bark extract of ackee, Blighia sapida was tested on catfish fingerlings over a 96hr exposure period as a potent organic piscicide. A static toxicity bioassay was conducted after a preliminary trial tests were carried out to determine effective extract concentrations to be used. A 300 number catfish fingerlings were randomly selected and distributed in triplicate concentrations of stem bark extracts of ackee. The test fish were treated with concentrations of 0.00, 1.60, 3.20, 6.40 and 12.8g/l stem bark extracts. At the end of the exposure period, plant toxicant caused visible behavioral changes on test fish which included aggression, erratic swimming, stunned posture, opercula movement, air gulping, settlement at the bottom and eventual death. The LC50 lethal concentration of 8.394g/l was recorded while the safe concentration was established to be 1.281g/l. There were significant changes in water quality parameters of the experimental tanks. It could be inferred from the results of this study that treated fish were irritated by the plant toxicant such that unstable behavioral changes were exhibited in all treated groups. Therefore, the use of stem bark of ackee in fish harvesting should be regulated.