Toxicological Evaluation of Ethanol Extract of Adenium obesum Stem Bark in African Catfish, <i>Clarias gariepinus</i>

Abstract

The toxicity of ethanol extract of Adenium obesum stem bark as a tool for aquaculture pond management prior to the stocking of desired fish species was evaluated in Clarias gariepinus over a 96-h exposure. The fish were exposed to 6.25 mgL-1, 7.50 mgL-1, 8.20 mgL-1, 8.80 mgL-1 and 10.00 mgL-1 of the extract and a control in an acute static toxicity bioassay after performing a range finding test to determine the median lethal concentration (LC50) of the extract. Exposed fish showed signs of changed behaviours with adaptive responses, respiratory distress and nervous compromise, including mortality in some of the exposed fish. The appearance and intensities of the observed signs were concentration and exposure period-dependent. An LC50 value of 7.35 mgL-1 was established for the extract in the exposed fish where mean mortality was significantly (p<0.05) concentration and exposure period-dependent. The toxic nature of the extract in the exposed hardy fish can be exploited for effective aquaculture pond management against some unwanted predatory and weed aquatic organisms. However, the indiscriminate use of higher extract concentrations could seriously jeopardise the biodiversity of any aquatic environment.