The effect of captive breeding on aggressive behaviour of European grayling, Thymallus thymallus, in different contexts

Abstract

Hatchery rearing is known to influence the aggressive behaviour of fish and to weaken antipredator responses. However, behavioural traits of an individual may not be free to evolve independently and can be correlated with one another. A positive link between aggressiveness and risk taking, for example, has been observed. We previously found second-generation hatchery grayling to be less aggressive than their wild conspecifics. In the present study, we examined both the level of aggression and the propensity to resume aggressiveness after a predator stimulus (risk taking) in young-of-the-year grayling from hatchery and wild strains of two populations. We were also interested in the effects of hatchery rearing on the link between the behaviours at the individual level and the consistency of this relation between populations. In contrast to our earlier findings, hatchery grayling appeared on average more aggressive than their wild conspecifics from the same population, whereas hatchery fish were more cautious after the threat stimulus in only one of the two populations. At the individual level, the behavioural association was, however, evident and similar in both strains of the two studied populations, such that the initially more aggressive fish also resumed aggressiveness faster after the threat than their less aggressive conspecifics. Consequently, while hatchery rearing for one generation has the potential to influence the expression of single behavioural traits, it may not necessarily result in changes in the link between them, that is, in the behavioural syndrome.