Toxicity of Cassava Effluents to Catfish, Clarias gariepinus, and the Effect on Some Target Organs - Abstract
A 96 hour bioassay was conducted to determine the toxicity of cassava effluents to Clarias gariepinus juveniles and its effects on the gills and liver as well as on some blood parameters such as packed cell volume (PCV), Red blood cells (RBC), White blood cells (WBC), Haemoglobin concentration (Hb) and their counts. Juveniles of C. gariepinus of the same age and size showed varying degrees of hyper-activity, mortality, stress and lesions to the organs of fish in the different concentrations of cassava effluent used (4.0, 4.5, 5.0, 5.5 ml/L). Static bioassay test revealed the 96 hour LC50 of cassava effluent as 4.28ml/L. Exposure to sublethal concentration of cassava effluents resulted in the reduction of blood parameters such as PCV, RBC and Hb however, the value of white blood cells increased at the end of the experiment. Degenerative and erosive changes were observed in the tissues of the organs of C. gariepinus. The gills of fish in the varying concentrations particularly in the higher concentrations (5.00ml/L and 5.50ml/L) showed signs of necrosis which means that at those concentrations cassava effluent was highly toxic to C. gariepinus juveniles. The liver of fish in higher concentrations also showed hydropic degenerative changes such as space formation. Water quality parameters (temperature, pH and oxygen) monitored during the experiment changed. The pH increased considerably throughout the course of the experiment, the dissolved oxygen concentration values recorded during the experiment decreases. Exposure to cassava effluent will prevent oxygen dissolution, cause destruction of breeding grounds as well as fish eggs, and ultimately, alteration of the entire aquatic environment leading to high mortality or
total eradication of aquatic life.