This study was planned to study the impact of effluent discharged from International Paper Industry (located at Rajmundry (A.P.) on the bank of river Godavari) on the respiration rate of a fresh water fish, Oreochromis mossambicus, Peters (Tilapia) and its ecological significance. Fishes were exposed to graded series of concentrations of the effluent for acute toxicity studies. The MAC value deduced was 3.15% of effluent in 50 liters of water for 30th days. A safety concentration of 3.1% of effluent l-50 was selected for this study. Exposed fishes appeared lethargic after 7th days of exposure, when compared to the control fish. The whole body respiration rate decreased significantly after 7days of exposure onwards. The respiration rate declined with the increase in exposure period up to 28th days of exposure. The exposed fishes were allowed to recover in toxicant free water for 7th days for 7d exposed fish, 14th days for 14d exposed fish, 21th days for 21d exposed fish and 28th days for 28d exposed fish. Significant recover was noted in 7d exposed fish where as with the increase in exposure period, the recovery was not significant. After 28th days of exposure, the fish could survive up to 24th days and afterwards the exposed fishes died during recovery due to drastic depletion in oxygen uptake by the fish from the recovery medium. The exposed fish could not recover to its pre-test activity even after 56th days of recovery, double the exposure period indicating damage to vital systems. Control fish remained clinically healthy for the entire period of experimentation.