Fish toxicity of the molluscicidal seeds ofMillettia thonningii(leguminosae: papilionoideae): impact onTilapia nilotica/auraeahybrids andCtenopharyngodon idella

Abstract

Ground seed suspensions of the West African legume, Millettia thonningii are known to be molluscicidal and have potential for use in schistosomiasis control programmes. The toxic effect of these suspensions on two species of fish found in Egypt was examined. Tilapia nilotica/auraea hybrids were less tolerant to the toxic effect than were Ctenopharyngodon idella. For both species, filtering the suspension reduced is toxity. A range of suspension concentrations were tested in order to determine which ones could be tolerated. It was demonstrated that at concentrations causing little or no harm to these fish species, i.e. 90 ppm unfiltered and 150 ppm filtered, effective snail kill could be achieved.