Observation of Gas Bubble Disease in Postlarvae of Indian Carps Important to Aquaculture

Abstract

Abstract Postlarvae of important Indian carps affected with gas bubble disease were observed in a nursery pond located in Bhubaneswar, Orissa State, India. Affected specimens had distended abdomens filled with gas and were observed floating upside down and occasionally exhibiting very slow swimming movements. There was mortality among the most severely affected specimens. Experiments conducted on postlarvae indicated that dissolved oxygen (DO) supersaturation in the pond was not the cause of gas bubble disease. Pond water supersaturatcd with up to 38 mg oxygen/L failed to produce gas bubble disease in the postlarvae. It was observed that, when DO ranged between 4 and 6 mg/L, freshly ingested phytoplankton continued to release oxygen in the bright sunlight, because photosynthesis went on in the more or less translucent bodies of the postlarvae. The mounting pressure and volume of oxygen in the gut impaired digestive function and distended the abdomen, causing the gas bubble condition. Fish with this condit...