LAUSR

The effect of incubation and rearing temperature on muscle development and swimming endurance under a high-intensity swimming test was investigated in juvenile Chinook salmon (Oncorhynchus tshawytscha) in a hatchery experiment. After controlling for the effects of LF and parental identity, times to fatigue of fish were higher when fish were incubated or reared at warmer temperatures. Significant differences among combinations of pre- and post-emergence temperatures conformed to 15-15 °C > 15-9 °C > 9-9 °C > 7-9 °C > 7-7 °C in 2011 when swimming tests were done at 300 accumulated temperature units post-emergence, and 15-9 °C > (7-9 °C = 7-7 °C) in 2012 when swimming tests were done at LF  ~ 40 mm. The combination of pre- and post-emergence temperatures also affected the number and size of muscle fibres, with differences among temperature treatments in mean fibre cross-sectional area persisting after controlling for LF and parental effects. However, neither fibre number nor fibre size accounted for significant variation in swimming endurance. Thus, thermal carry over effects on swimming endurance were not mediated by thermal imprinting of muscle structure. This is the first study to test how temperature, body size, and muscle structure interact to affect swimming endurance during early development in salmon. This article is protected by copyright. All rights reserved.