Are farmed salmon more prone to risk than wild salmon? Susceptibility of juvenile farm, hybrid and wild Atlantic salmon Salmo salar L. to an artificial predator

- Offspring of farmed Atlantic salmon display reduced survival in nature.
- Increased susceptibility to predation due to altered behaviour has been hypothesised.
- We examined susceptibility of farmed and wild salmon to an artificial predator.
- Equal susceptibility to predation was detected in salmon of farmed and wild origin.
- Increased susceptibility, through altered risk-taking behaviour, was not detected.

Offspring of farmed Atlantic salmon have been documented to display lower survival than the offspring of wild salmon in the wild. It has been suggested that reduced survival of farmed salmon offspring in the wild could, in part, be explained by increased susceptibility to predation through altered behaviour. This has however, not been demonstrated. This study investigated if farmed salmon display a higher susceptibility to predation than wild salmon, by exposing fry of farmed, hybrid and wild origin to an artificial predator in a semi-natural environment with competition for feed. The main results can be summarised as: (i) susceptibility to predation was similar in salmon of all origins, i.e., an equal number of farmed, hybrid and wild salmon were caught by the artificial predator; (ii) susceptibility to the artificial predator was not size-selective, i.e., large, fast growing individuals were caught in the same frequencies as small, slow growing individuals. As salmon fry of all origins were caught by the artificial predator in similar frequencies, equal susceptibility to predation was detected in farmed and wild salmon, under these conditions. If farmed salmon exhibit a genetically higher susceptibility to predation than wild salmon, potentially through increased risk-taking behaviour, this still remains to be demonstrated.