The importance of attitude: the influence of behaviour on survival at an ontogenetic boundary

Behavioural traits can strongly influence fitness and survival and are important mediators of life history trade-offs. This study explored the links between mortality trade-offs associated with fast growth during larval life and behaviour of individuals during an important life history transition. Longitudinal sampling of a cohort of damselfish settling on a reef at the end of their larval stage found that individuals with small otolith sizes at hatching and low otolith growth rates were selectively removed from the local population, while there was no apparent selection for size or body condition over the first 24 h after settlement. Selection against slow growth (initial larval growth and maximum growth) and small size at hatching and settlement were accentuated over the first month after settlement. Detailed behavioural assessments of naïve larvae settled onto habitat patches and monitored for 24 h found that initial boldness aided survival, but individuals that ventured larger distances from shelter suffered higher mortality. Correlations of growth with behavioural attributes were generally poor; however, there was a weak correlation between boldness and maximum growth. A measure of flexibility in the maximum distance ventured from shelter was positively related to initial otolith growth. Our results suggest that although early growth which is relatively slow leads to higher mortality later in life, and behavioural attributes influenced survival, there were only weak correlations between growth history and behaviour. This may be due to strong selective pressures on young fish to learn novel behaviours rapidly after settlement. Selection may promote behavioural flexibility at this key ecological transition