Links between behaviour and acute hyperthermia and hypoxia resistance in rainbow trout using isogenic lines

Abstract

Acute hyperthermia and hypoxia resistances are traits of growing interest in aquaculture in the context of adaptation to climate change. The feasibility of genetic improvement of these traits through selection was demonstrated in rainbow trout (Oncorhynchus mykiss) and other fish species. It is now important to understand what makes a genotype resistant by identifying the mechanisms underlying these resistances, which are still under debate. In the present study, we investigated links between resistances to acute hyperthermia and hypoxia and some behaviour variables measured in moderately stressful conditions. For this purpose, we used rainbow trout isogenic lines, previously phenotyped for acute hyperthermia and hypoxia resistances. Behaviour of fish was phenotyped using an individual test as well as a group test, respectively response to a novel environment and evaluation of shoaling combined with response to a moderate thermal challenge. The use of isogenic lines allowed to relate resistance to acute hyperthermia with behaviour phenotypes. There were significant differences in behaviour between isogenic lines. Some behaviour variables were found to be highly correlated with acute hyperthermia and hypoxia resistances. Isogenic lines with a higher activity level were found to be more sensitive to acute hyperthermia and more resistant to acute hypoxia than lines with a lower activity level. This encouraging link between behaviour and resistance phenotypes also suggest that some behaviour variables could be used as predictors for acute hyperthermia and hypoxia resistances in fish, leading to more ethical phenotyping methods than classical ones.