Behavioural type in newly emerged steelhead Oncorhynchus mykiss does not predict growth rate in a conventional hatchery rearing environment.

Behavioural assays were conducted on newly emerged steelhead Oncorhynchus mykiss to investigate the presence of behavioural syndromes and to determine whether behavioural type in young fish predicts growth rate in a conventional hatchery rearing environment. Individual fry were consistent in their position choice and activity behaviours across safe and unsafe contexts, as well as among assays conducted on different days. Position choice and activity behaviours, however, were not necessarily correlated to each other. Both behaviours predicted feeding rates during behavioural assays, but there was no relationship between fry behaviour and subsequent growth rate or survival during the first 3 months of hatchery rearing. These results support the hypothesis that selection in captivity may be relaxed with respect to behavioural type rather than directional, allowing for increased behavioural variance in domesticated populations. Modest magnitudes of correlations among fry behaviours, however, suggest that behavioural type may be unstable at the onset of the juvenile feeding stage.