Acute toxicity of ethanol extracts of cocoa bean shell on sarotherodon galilaeus juveniles

Abstract

An acute toxicity test of ethanol extract of cocoa bean shell (CBS), a by-product of cocoa processing was conducted on 250 Sarotherodon gallilaeus juveniles for 96 h. There were 5 treatments and one control with each having 3 replicates. The treatments were prepared as 10,000, 7500, 4167, 2315, 1286 and 0 mg L-1 (control). The aim of the experiment was to study the toxic effects of Ethanol extract of CBS. While, the control experiment produced no mortalities and adverse histopathological responses, there were reactions to the presence of CBS extract in all the treatments which included restlessness and mortality. The lethal concentrations at which fifty percent of the test population died (LC 50) obtained using the logarithm method were 7943, 5012 and 6310 mg L-1 for replicates 1, 2 and 3, respectively while the probit method gave 5878, 4865, 6103 mg L-1 for replicates 1, 2 and 3, respectively. Histopathological examination of control fish showed no lesions on all tissues examined. However, marked changes were observed in the liver in form of degenerative hepatocytes, multifocal aggregation of haemosiderin laden macrophages; in the gills as shortening of gill filaments and in the brain as spongiosis of white cerebral matter of fish subjected to various concentrations of CBS extract. It was concluded that ethanol CBS extract possessed piscicidal properties on S. gallilaeus which could be useful in culling stunted and unwanted fish populations from ponds before stocking