Behavioural and some Physico-Chemical Assessment of Fresh Water Catfish <i>Clarias gariepinus</i> (Burchell, 1822) Exposed To Acute Concentrations of Delsate® Herbicide (Glyphosate)

Abstract

Acute toxicity data has been used to derive water quality guidelines for regulatory measures. Behavioural and some physico-chemical characteristics of fresh water adult African catfish, Clarias gariepinus exposed to acute concentrations of Delsate herbicide for 96 hour were monitored. The concentrations of the toxicant tested were 0.5 mgL^-1, 1.0 mgL^-1, 1.5 mgL^-1, 2.0 mgL^-1 and 2.5 mgL^-1. The 96 hours LC₅₀ obtained for C. gariepinus with mean weight (661±0.1 g) and standard length (23.5±0.4 cm) was 0.14 mg/L. The upper and lower confidence limits were 0.18% and 0.11% respectively. The mean physico-chemical parameters measured varied from: temperature: 27.45±0.4 to 28.20±0.03 ºC, pH: 6.65±0.2 to 7.32±0.08, DO: 7.0±0.1 to 5.33±0.40 mgL-1, CO₂: 160±0.1 to 5.0 mgL^-1 and total hardness: 34 mgL^-1 to 0.00 mgL^-1. The behavioural changes observed were secretion of mucus and blood, erratic swimming, faster operculum movement among others. These varied with the concentration of delsate and indicated that increase in delsate concentration increased the mortality rate of C. gariepinus. The results obtained in this study showed that C. gariepinus adults were stressed before death. The use of delsate near fish farm or in agricultural field close to aquatic environment should be discouraged in order to safeguard aquatic organisms such as fish which constitute the major source of human protein.

Key Words: Behavioural, delsate, monitored, C. gariepinus and physico-chemical properties