Toxicity of Domestic Effluents to Clarias gariepinus Fingerlings

Abstract

The toxicity of domestic effluent discharge from Niger Delta University (NDU) female hostel on Clarias gariepinus fingerlings was studied using static bioassay method. The exposure period lasted for 96 hours. The fish specimens were acclimatized for one week after which they were distributed randomly into 18 transparent rectangular plastic tanks of 20 litres each consisting of graded effluent treatments; T2 (20%), T3 (40%), T4 (60%) T5 (80%), T6 (100%) and T1 (0%) i.e. the control, all in triplicates, in a completely randomized experimental design. Physicochemical parameters, heavy metals and detergent concentrations of the water were monitored using standard methods. The data generated were subjected to one way analysis of variance (ANOVA) at 5% probability level using Duncan multiple range test to separate differences between means. Behavioural responses of exposed fish such as erratic swimming, restlessness increase in opercula beating, gasping for air and accumulation of mucus on test organisms occurred in T5 (80%) and T6 (100%) effluent concentration. No mortality was however recorded during the 96hours, probably because water quality obtained such as pH (7.08), conductivity (894 µS/cm), TDS (441 mgl-1) and DO (7.00±0.03 mgl-1) were below the threshold besides the hardy nature of Clarias gariepinus. Levels of NO3, BOD, PO4, turbidity, detergent, total coliform; Pb, Cd, and Cr were however higher than safe limit standards stipulated by statutory bodies to protect aquatic life.