Behavioural response of juvenile Chinook salmon Oncorhynchus tshawytscha during a sudden temperature increase and implications for survival

·Juvenile Chinook salmon Oncorhynchus tshawytscha survival and behaviour were evaluated during a temperature increase from 8.8 to 23.2 °C.·Relatively little mortality (12%) occurred, which was unexpected.·The percent of fish with an active swimming behaviour increased from 26% to 93% and opercular beat rates increased from 76 to 159 beats per minute.·Although sublethal in the laboratory, thermal stress was likely incurred by juvenile salmon in this study and the associated behavioural changes may increase predation potential in the wild.