Habitat and morphological characteristics affect juvenile mortality in five coral reef damselfishes

Abstract

The abundance and distribution of demersal fishes rely on larvae successfully settling from the pelagic environment to a benthic habitat and their subsequent survival. With high mortality rates during this life stage, settling to a habitat that maximizes survival is critical. However, relationships between settlement choices and subsequent survival are poorly understood and may vary among species with different habitat preferences. To test this, we focused on five congeneric (Pomacentrus) damselfish species that are known to differ in their habitat choices and explored whether habitat associations at settlement influenced survival. Newly settled individuals were tagged and monitored daily for two weeks to estimate natural mortality rates. Morphological attributes of fish and characteristics of settlement habitats, including depth, rugosity, benthic substrata, and local fish assemblages, were used to predict mortality. We found that some species displayed stronger associations with specific benthic substrata at settlement, but contrary to expectations, these selected habitat characteristics were relatively weak predictors of survivorship. Our survival analysis revealed that the best predictors of survivorship were rugosity (P. adelus and P. amboinensis) and two morphological traits, body depth and ocellus size (P. chrysurus and P. adelus). Interestingly, we found that P. moluccensis that settled in areas of high coverage of mounding coral experienced increased mortality. Of the remaining substrata, analysis showed that instead of associating with habitat characteristics enhancing survivorship, individuals tended not to associate with habitats characteristics that increased mortality (e.g., Turbinaria and sand). This study highlights the species-specific drivers of early post-settlement mortality in coral reef fishes.