Overview of research on tuna thermo-physiology using electric tags

• Main Authors: Takashi Kitagawa, Shingo Kimura, Hideaki Nakata, Harumi Yamada
• Format: Report
• Language: English
• Published: Ocean Research Institute, University of Tokyo 2004
• Subjects: Pacific; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2481; http://id.nii.ac.jp/1291/00002481/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2481&item_no=1&attribute_id=18&file_no=1

The behavioral physiology of bigeye tuna was investigated using acoustic tags in the 1990s. They spend most of the daylight hours below the thermocline but make regular brief excursions into the mixed layer. In doing so, they reduce the efficacy of their vascular countercurrent heat exchangers while gaining heat from the warmer environment and then increase it again when they return below the thermocline. Recently, archival tags have been used on a range of tuna species including bluefin. This tag, recovered when the tuna is harvested, yields time-series data over longer periods than acoustic tags. Although immature Pacific bluefin spend most of their time at the surface, they often dive below the thermocline, maintaining a peritoneal temperature. This might be due either to heat conservation or high heat production. Further, while giant Atlantic bluefin show an ability to maintain their temperature above the ambient, there are occasions in cold water when some physiological process is clearly limiting their dive time. Solution of the growth conundrum that their warm body temperature may pose an ecological problem as they grow in body mass, should be clarified by using tag data. This will lead to investigation of their adaptation mechanisms to their habitats.