Acute Toxicity of Ammonia to the African Freshwater Catfish Clarias gariepinus

Abstract

Fingerlings of Clarias gariepinus were collected and tested for growth and survival in acute concentration of ammonia. Results showed that mortality was 10% at 1.5 mg.l-1, 20% at 2 mg.l-1, 30% at 3 mg.l-1, 50% at 4 mg.l-1 and 60% at 6 mg.l-1. 20% fingerlings showed dark colour on their body, respiratory distress and erratic swimming. 30% became hyper-excited and ventilated with rapid mouth and opercula movement. 10% were convulsive and motionless with a lot of mucous materials on the body to confer death. The 96-h LC50 value was 3.85 mg.l-1 while the threshold value was 3.80 mg.l-1. The fish fed vigorously at the initial introduction of food but the anxiety to feed declined as concentration and exposure time increased.


Key words: Toxicity, ammonia, Clarias gariepinus.


Journal of Aquatic Sciences Vol.18(1) 2003: 71-74