<b>Piscicide Effects of Mahua Oil Cake from the Finfish Culture System</b> The present investigation envisage a study of the effects of pesticides on four fin fishes Oreochromis mossambicus from mahua oil cake, a derived from the plant Madhuca longi folia seed. Although some reports on the effects of mahua oil cake on fin fishes and Madhuca seed on fresh water pond culture systems are available, information on their effect on brackish water culture systems are rather scanty. Fishes along with the shrimps were taken at 10, 20, 30 ppt salinity and mahua oil cake MOC was applied at 10, 15, 20 ppm concentrations to see the mortality timings of the fishes. Phyisco chemical parameters and LC50 concentration were recorded in the study. Lethal concentration LC50 was recorded for the species Elops machnata the concentration was found to be 5ppm. There was no variation in the temperature, although the pH and DO levels were affected by the application of MOC. Oreochromis mossambicus, Madhuca longifolia, mahua oil cake, phyisco chemical parameters 1205-1211 Issue-5 Volume-2 R. Vinothkumar | Rupam Dey | Dr. M. Srinivasan