 Variations in their muscle temperatures are not necessarily influenced by water temperatures or that of swimming speeds, which indicates the ability of the bluefin tuna to control the level of efficiency of their heat exchange system.Relating to the efficiency of oxygen extraction, tuna gill structure maximizes contact between water and the respiratory epithelium, which minimizes anatomical and physiological “dead space” in order to enable more than 50% oxygen-extraction efficiencies.This allows the fish to maintain a high rate of oxygen consumption as it continually swims out to others areas of oceans in search of food and ground for growth and reproduction.