Body temperature of the Atlantic bluefin tuna (Thunnun thynnus L.) in the Western Mediterranean

This study documents body temperature in the Atlantic bluefin tuna (Thunnus thynnus L.) in the Mediterranean Sea and temperature variability caused by the stress of capture. The investigation was carried out in the traditional trap (tonnara) of Isola Piana (Sardinia, W Mediterranean) where body temperature recordings were conducted on free-swimming bluefin confined in the system of nets known as “camere” or chambers. We tracked the body temperature of two bluefin tuna (214 and 191 cm CFL) using a commercial data logger (HOBO U12, Onset Computer Corporation), under two conditions: the pre-fishing phase, when specimens confined in the “camera di ponente” are undisturbed and the fishing phase when bluefin tuna are trapped in the “camera della morte” and undergo the stress of confinement and capture (mattanza). Body temperature increased by about 2°C during the “mattanza”, whereas no temperature variation was exhibited during the pre-fishing phase. The heat transfer coefficient (K), calculated for both bluefin tuna during the “mattanza”, revealed a rapid increase in heat transfer. Additional data on ambient temperature Ta, white muscle Tw (n = 65; 110–287 cm CFL) and red muscle temperature Tr, (n = 249; 107–287 cm CFL) were obtained from live fish during angling operations, and excess body temperature (Tx = Tr–Ta) was calculated. Mean red muscle temperature was 27.6 ± 1.48°C in an ambient temperature of 18.9 ± 0.84°C. The excess red muscle temperature Tx was 8.21–9.10°C, and the red muscle was 2.4 ± 1.78°C warmer than white muscle.