This experiment was continued for 7 days, and a 45-min video recording (DCR-HC 46, Sony, Japan) was conducted on days 0 (before transfer), 1, 2, 4, and 7 (n= 8). The video recording was always taken between 10:00 and 16:00 h. The air–surface respiration, ASR, was recorded when fish directly swallowed air on the water's surface.