Correlation between heat-shock protein induction and reduced metabolic condition in juvenile steelhead trout (Oncorhynchus mykiss) chronically exposed to elevated temperature

The metabolic condition, stress response, and growth rates of juvenile steelhead trout (Oncorhynchus mykiss) were assessed throughout a 10-week exposure to 15 and 20 °C, each at full and half food ration. Metabolic measurements included white muscle phosphocreatine (PCr), ATP, ADP and AMP, hepatic glycogen, and global metabolite profiling of muscle and liver using 1H nuclear magnetic resonance (NMR) spectroscopy. Stress was assessed via induction of heat shock proteins (hsps) 63, 72, 78 and 89, and growth was determined from otolith measurements. Exposure to 20 °C induced hsp synthesis, particularly hsp72. Principal components analyses revealed positive correlations between increased stress (elevated hsp72 and hsp89) and decreased metabolic condition (decreased PCr, ATP and glycogen). However, no effect on growth was observed, suggesting that 20 °C is the upper limit of the steelhead trout's preferred range. The NMR analysis of multiple metabolite classes not only identified a decrease in PCr, ATP and glycogen in temperature exposed fish, but also provided a more integrated description of the biochemical response to thermal stress.