Immature Pacific bluefin tuna, Thunnus orientalis, utilizes cold waters in the Subarctic Frontal Zone for trans-Pacific migration

The habitat and movements of a Pacific bluefin tuna were investigated by reanalyzing archival tag data with sea surface temperature data. During its trans-Pacific migration to the eastern Pacific, the fish took a direct path and primarily utilized waters, in the Subarctic Frontal Zone (SFZ). Mean ambient temperature during the trans-Pacific migration was 14.5 +/- 2.9 (A degrees C A +/- SD), which is significantly colder than the waters typically inhabited by bluefin tuna in their primary feeding grounds in the western and eastern Pacific (17.6 A +/- 2.1). The fish moved rapidly through the colder water, and the heat produced during swimming and the thermoconservation ability of bluefin tuna likely enabled it to migrate through the cold waters of the SFZ.