Biological impact of in-situ exposure of catfish (<i>Clarias gariepinus</i> Burchell, 1822) to agricultural pesticide residues in the Tabalak pond

Abstract

The Tabalak pond is contaminated by residues of agricultural pesticides, used by market gardeners. The present study aims to evaluate  the ecotoxicological impact of this contamination on the ichthyofauna of this pond from growth parameters, biometric indices and  organs histopathology. An in-situ fish cage experiment was used, compared to controls placed elsewhere and fish in the open water of  the pond. Thus, juveniles of Clarias gariepinus were raised in tanks (control) and Tabalak pond for 120 days. The results showed that the  survival and growth of the fish were better at the control site than the Tabalak site. The survival rate (SR) was 93.75% for the control,  compared to 83.13% at the Tabalak site. The mean final weight (Mfw) was 148.71 g compared to 138.47 g, the weight gain (Wg) was  133.52 g compared to 123.45 g and finally the specific growth rate (SGR) was 1.9% compared to 1.85% for the control and Tabalak sites  respectively. Semi-quantitative evaluation of organ tissues showed slight alterations in the organs of the control fish and moderate  alterations in the organs of the caged and open water fish. Some of these histological alterations may be detrimental to certain vital  functions of these fishes.