Global warming is not only a matter of increasing temperature, ice melting, increasing sea water level and enhanced abnormalities in weather conditions. Changes in temperature, though might seem, as little as few degrees, will bring about major changes in the functioning and metabolism is global aquatic, ecological and land-water systems. Fish population in world oceans and seas will suffer major dynamic changes, in term of population, species and catch composition. Fish species will be forced to large-scale migration to adapt themselves for new living in suitable waters and some fish species are expected to disappear. Such major changes in fish species will also have other impacts on global ecology of other animal species.