Acute Toxicity of Ammonia to the African Freshwater Catfish <i>Clarias gariepinus </i>

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