Behavioural syndromes in juvenile brown trout (Salmo trutta); life history, family variation and performance in the wild

The main aims of this study were to investigate (1) the occurrence and strength of the shyness-boldness behavioural syndrome in brown trout fry, (2) whether this syndrome is associated with paternal migratory life history, (3) whether fry survival and growth in the wild is associated with paternal life history and/or boldness and (4) whether offspring performance showed maternal effects. Nine female migratory trout were each crossed with one migratory and one resident male and the offspring were raised in hatchery tanks until first feeding. The behavioural studies showed that fry that responded bold towards a novel object also accepted a novel food item earlier and responded more aggressively towards their own mirror image. Principal component analysis showed that this shyness-boldness syndrome (PC1) explained 34% of the behavioural variation. Offspring boldness was not affected by paternal migratory life history, but significant effects of the female parent suggested maternal and/or genetic effects. Deviations from this pattern (PC2), where some individuals behaved less aggressively and performed more approaches to food, explained an additional 17% of the variation in behaviour, and was significantly influenced by length and paternal migratory life history. Fry growth and survival in nature was not associated with boldness (PC1) or PC2, suggesting that alternative behavioural strategies can be successful in nature. However, female parent effects on variation in fry size persisted over the first growth period in the wild, suggesting that these effects may influence offspring fitness during early life when major selection occurs.