A study was conducted to assess the cytogenetic changes in an air breathing fish, Channa punctatus subjected to the polluted water of River Cooum. A control group of fish was maintained without any treatment. The fishes were exposed to Cooum water as test samples for 96 hours. The opercular movements were counted at an interval of 1 hour, four times a day for both the control and experimental. The tissues of gill and kidney were then subjected for the study of chromosomal aberration. It was found that the fishes which were exposed to Cooum water showed a decreasing rate of opercular movements as compared to the fishes exposed to tap water. Several structural chromosomal aberrations such as chromatid breaks and gaps, fragments, endoreduplication, ploidy were observed in the fishes subjected to Cooum water in comparison to the Control fishes thus indicating induced mutation in fishes subjected to Cooum water.