Toxicity of Herbicide Primextra on Juveniles of Clarias Gariepinus (Burchell, 1822).

Contamination of aquatic ecosystem is a matter of great concern. Primextra chemical constitute potential hazards to aquatic environment. The aim of the study was to evaluate the toxicity of primextra on the juveniles of Clarias gariepinus. Mixed sexes of Clarias gariepinus juveniles were obtained from school of Agriculture, Mando, Kaduna, and transported to the Zoological Garden, Kaduna State University. “Primextra Gold” containing atrazine (370g/l) and S-metolachlor (290g/l) were purchased from Central Market Kaduna. Fish were acclimatized for two weeks and fed with 2mm “Ala Aqua”. Stock solution was prepared by adding 1ml of the herbicide obtained in concentration of 50g/ml to 99ml of water and used to prepare 0, 10, 13, 16, 19 and 22.1mg/l concentrations. Fish were randomly selected, weighed and distributed into eighteen (18) plastic aquarium tanks with each containing 10 juveniles for the acute toxicity and sub-lethal toxicity bioassay. Behavioural responses and mortality rate were observed. The results of the acute toxicity bioassay, the 96-hours LC50 was calculated. Haematological profile including total erythrocyte count (RBC), haemoglobin concentration (Hb), haematocrit (PCV), mean corpuscular volume (MCV), mean corpuscular haemoglobin concentration (MCHC), mean corpuscular haemoglobin (MCH), leukocyte count (WBC) and the differential leukocyte count (DLC) were determined. Length and weight were measured. The fish showed abnormal swimming movements. The first mortality was observed at 24 hours at 10mg/L, 13mg/L, 16mg/L, 19mg/L and 22mg/L concentrations while the RBC count was 2.24±0.00 x106 cell/ml. Results of the histopathological studies of the liver of C. gariepinus exposed to acute and sub-lethal of primextra revealed prominent changes in the liver such as perivascular cuffing around the central vein and mild congestion of the sinusoids. The results of the present study revealed that primextra was toxic to Clarias gariepinus with LC50 value of 12.66mg/L