Behavioural syndromes in farmed fish: implications for production and welfare

Consistent individual differences in behaviour have been described for several species of salmonid fish, the group that has been most intensively farmed. In particular, fish accept different levels of risk when competing for limited resources and, in nature, the different behavioural phenotypes seem to perform better in different environmental conditions. Studies of the behaviour of farmed fish can provide insights into the genetic basis of such differences and into their consequences for some components of fitness. Both deliberate selection for fast growth in farmed fish and inadvertent selection of fish that flourish in intensive aquaculture systems have generated inherited behavioural differences between farmed fish and the wild stocks from which they originated. Thus, fish from farmed stocks tend to be bolder and to take greater risks when foraging; they may also be more aggressive, depending both on conditions during selection and the environment used to screen aggressiveness. Such results indicate the existence of inherited variation in risk-taking and aggression in the populations from which today's farmed stocks were derived. They also suggest that fish from the risk-avoiding/non-aggressive end of the behavioural spectrum may fail to flourish in conditions that usually prevail in intensive husbandry systems. The implications of these findings for production and welfare in aquaculture are discussed.