The effects of environmental heat stress on heat-shock mRNA and protein expression in Miramichi Atlantic salmon (Salmo salar) parr

This study combines laboratory experiments with temperature monitoring and fish sampling in the wild to determine if Atlantic salmon (Salmo salar) parr from the Miramichi River in New Brunswick are currently experiencing significant sublethal heat stress during the warm summer months. Laboratory experiments indicated that Hsp 70 mRNA and protein and Hsp 30 mRNA were all significantly induced in Atlantic salmon parr between 22degreesC and 25degreesC. Field sampling during moderate spring temperatures and a high-temperature event in summer further indicated that the threshold for mRNA induction of both Hsp 70 and Hsp 30 is around 23degreesC, but Hsp 70 protein levels were only significantly elevated in the field at 27degreesC. Hsc 70 mRNA and protein levels were not significantly increased during heat stress under laboratory conditions. In the field, however, Hsc 70 mRNA was significantly increased at 23degreesC and both Hsc 70 mRNA and protein levels were elevated at 27degreesC. Taken together, the results of this investigation suggest that Atlantic salmon parr from the Miramichi River are currently experiencing temperatures that will cause significant protein damage and induce a heat-shock response for about 30 days each summer.