Fingerlings of tilapia were used to compare the oxygen consumption rates at 0, 10, 20 and 30 ppt salinity. Oxygen consumption of tilapia at 0, 10, 20 and 30 ppt salinity was found 2.14, 0.71, 1.43 and 1.42 ml/liter/h respectively. Oxygen consumption rate thereafter decreased with increasing salinity, although the lowest consumption occurred at 10 ppt. Lower consumption at high salinities might be a result of reduced activity, which in itself was salinitymodulated. The fish in this study were in or near a resting state, and that differences in oxygen consumption rates probably were related to the energetic cost of ionic and osmotic regulation. Again, mechanism in the fill tissue might involve significant energy-consuming processes in different water salinities compared to fresh water.