Environmental variability, early life-history traits, and survival of new coral reef fish recruits

For benthic marine organisms with complex life cycles, conditions experienced by pelagic larvae can influence juvenile survival. Trait-specific selective mortality has been documented in the laboratory and field, yet our knowledge of the factors contributing to the existence, strength, and consistency of natural selective mortality is limited. We compiled previously published and unpublished data on the common Caribbean coral reef fish, Thalassoma bifasciatum, recruiting to Barbados, West Indies, and the upper Florida Keys to examine how environmental variability during pelagic larval life influences the distribution of early life-history traits exhibited by new recruits. We explored how the scope of variability in otolith-derived traits such as larval growth, pelagic larval duration (PLD), size and condition at settlement, and early juvenile growth influences the degree to which mortality of juveniles is selective. At both locations, contrasting oceanographic conditions (periodic passage of large low-salinity North Brazil Current [NBC] rings near Barbados and seasonal variation in water temperature at Florida) led to significant differences in the early life-history traits of recruits. Mortality was most frequently selective for the two most variable traits, condition at settlement and early juvenile growth. Environmental variability (including variation in predation pressure and stress-inducing conditions) also likely influences juvenile mortality and consequently the degree to which selective loss of particular traits occurs. As we begin to better understand the spatial, temporal, and species-specific circumstances in which events occurring during larval life influence juvenile performance, studies must also be extended to examine how these processes are translated into adult fitness.