Laboratory bioassay studies were carried out to evaluate the toxic effect of Cadmium, Chlorpyrifos and Cadmium + Chlorpyrifos on the haematological changes in Tilapia, Oreochromis mossambicus. The lethal toxicity of commercial grade organophosphate insecticide, Chlorpyrifos (20% Emulsified concentration), heavy metal, Cadmium and Cadmium + Chlorpyrifos on Oreochromis mossambicus was tested. The lethal toxicity of Cadmium, Chlorpyrifos and Cadmium + Chlorpyrifos to the tilafia fingerlings exposed for 96 hr was found to be 169.80ppm, 0.022ppm and 92.04ppm respectively. The fingelings were exposed to lethal concentrations (LC50) of Cadmium, Chlorpyrifos and Cadmium + Chlorpyrifos to study the alterations of different haematological parameters at 24hrs and 48 hrs of exposure. Reduction in the number of red blood cells, Haematocrit value, Haemoglobin conten and increase in Mean corpuscular haemoglobin, Mean carpuscular volume, Mean carpuscular haemoglobin concentration were evident.
