LETHAL EFFECTS OF 2,2-DICHLOROVINYL DIMETHYL PHOSPHATE (DDVP) ON FINGERLING AND JUVENILE Clarias gariepinus (BURCHELL, 1822)

Abstract

This study investigated the lethal toxicity of 2,2-dichlorovinyl dimethyl phosphate (DDVP) on African mud catfish, Clarias gariepinus fingerlings (mean weight 7.02 ± 2.56 g) and juveniles (mean weight 13.54 ± 1.46 g) in a static renewable bioassay. DDVP, also known as Dichlorvos is an organophosphate pesticide. Each treatment in the lethal test was in triplicates with bioassay media concentrations (fingerlings: 0, 250, 275, 300, 325 µgL-1) and (juveniles: 0, 400, 450, 500, 600 µgL-1). Data on fish mortality as well as the physico-chemical parameters (temperature, pH, dissolved oxygen and electrical conductivity, EC) of water were collected and subsequently subjected to a one way analysis of variance (ANOVA) at 5% probability level. Duncan Multiple Range Test (DMRT) was used to separate differences between means. The median lethal concentration (LC50) and median lethal time (LT50) were determined by probit analysis. The water quality parameters of the treatment tanks showed no significant difference with those of the control except for conductivity and pH. Behavioural responses in the fishes included erratic and uncoordinated swimming which were observed to be more pronounced in the juveniles. Bleached body was the only external change observed and this was more pronounced in the fingerlings. The 96-hr LC50 for fingerlings and juveniles were 275.2 and 492.0 µgL-1 respectively. The LT50 values for fingerlings were 48.10 and 7.77 hrs for concentrations 250 and 325 µgL-1 respectively; while those of juveniles were 25.54 and 5.34 hrs for 400 and 600 µgL-1 respectively. The results indicated that DDVP was 1.79 times more toxic to the fingerlings than the juveniles.

Keywords

• dichlorvos
• toxicity
• clarias gariepinus
• lc50
• lt50