Fig. 5. Diving behavior of Atlantic bluefin tunas recorded with electronic tags. Data on ambient and internal temperature and pressure are recorded at 2 min intervals for two Atlantic bluefin tuna in the North Atlantic. (A) Fish 521; 219 cm, 179 kg; (B) Fish 485; 208 cm, 154 kg at time of release. Days shown are representative of behaviors observed daily in the Gulf of Maine (A) and Flemish Cap (B). Both fish show a pattern of rapid diving into cool water and regular returns to the surface. Conservation of internal body temperature is also shown. The lack of any temperature effect (significant cooling) on the peritoneal cavity suggests that the continuous resurfacing may be associated with physiological requirements for rewarming of the heart and reoxygenation of the tissues.