Larval growth history determines juvenile growth and survival in a tropical marine fish

Processes that occur around the transition between larval and juvenile life-stages can have a major effect on the population dynamics of organisms with complex life cycles. We explore the roles of larval history and selective post-settlement mortality in determining the growth and survival of newly settled individuals of the damselfish, Pomacentrus amboinensis (Pomacentridae). Specifically, we determine whether the direction and intensity of selection on the recruits differs among various size-classes of predators. A mark-recapture study showed that individuals who survived 9 or more days were significantly larger at settlement than those that died within the first day (12.3 vs 11.9 mm SL), when mortality was highest (25% d(-1)). Censuses revealed that the species and size composition of piscivores differed markedly between two reef habitats where P. amboinensis was common. A cage experiment, conducted in both habitats, manipulated the sizes of predators that could access newly settled P. amboinensis to determine whether the resulting mortality of the recently settled fish was influenced by larval growth history or size at settlement. Ten days after the start of the experiment individuals that grew slowly in the second half of their larval life had been lost from most of the experimental treatments. Small fish were also selectively lost from the coarse-mesh cage on the reef base. Significant positive relationships between pre- and post-settlement growth rates were found in both habitats for the fine mesh cages, cage controls and open patch reefs. This relationship was reversed in the coarse mesh cages in both habitats. This growth compensation was facilitated through the action of a particular size range of predators, whose impact was disrupted or masked in the open treatments by the action of a diverse predator pool. The present study underscores the complexity of the processes that influence the early post-transition growth and survival in organisms with complex life-histories.