ABSTRACT: Dissolved oxygen (DO) depletion was studied by adding 180 ± 0.63 ml of sodium sulfite stock
solution, 100,000 mg/l, into 254 L de-chlorinated water without fish. DO dropped from 6 mg/l to 0 mg/l within
20 min. Sodium sulfite, 7.1 mg/l was used for the second experiment. The second experiment was conducted to
investigate acute anoxia on stress in hybrid catfish (Clarias gariepinus Burchell x C. macrocephalus Gunther).
Catfish, 20.03 ± 7.55g body weight and 13.87 ± 1.89 cm body length, were exposed to anoxia for 40 min. The
results show that blood clotting time (min) and serum cortisol (µg/dl) were significantly different in
experimentals at p