First record of the at-sea swimming speed of a Pacific salmon during its oceanic migration

• Published in: Marine Ecology Progress Series
• Main Authors: Tanaka, Hideji, Naito, Yasuhiko, Davis, Nancy D., Urawa, Shigehiko, Ueda, Hiroshi, Fukuwaka, Masa-aki
• Format: Article in Journal/Newspaper
• Language: English
• Published: Inter-Research
• Subjects: Chum salmon; Oceanic migration; Swimming speed; Orientation; Time allocation; Foraging behavior; 487; Bering Sea; Keta; Pacific
• Online Access: http://hdl.handle.net/2115/39887; https://doi.org/10.3354/meps291307

The swimming behavior of the chum salmon Oncorhynchus keta was studied for 53 d of its 67 d oceanic migration from the central Bering Sea to the Japanese coast. We provide the first data on swimming speeds by a homing salmon, recorded at 5 s intervals by a fish-borne time-speed, depth, and temperature logger. Swimming speed rarely exceeded 1.0 m s^[-1], and horizontal swimming speed was 36.4 ± 15.2 km d^[-1]. Cumulative horizontal swimming distance was approximately 2500 km, equivalent to 90% of the minimum distance between the release and recovery sites (2760 km). Swimming depth and speed peaked around dawn and dusk, and there was a smaller peak around midnight. The fish showed sequential up-and-down movement near the thermocline during daytime. Diurnal patterns of movement suggest that homing chum salmon spend a considerable time foraging, and the strategy is different between daytime and nighttime. Our findings indicate that over large distances of ocean, a homing salmon maintains a strong homeward orientation, but that passive transport by favorable water currents may help the migration.