Habitat selection by emperor fish larvae

Abstract

One of the great puzzles of coral reef fish ecology is how pelagic larvae locate the habitat in which they settle. The present study explored whether offshore emperor fish (Lethrinidae) larvae selected a specific reef and/or habitat at settlement. Although older juveniles are known to use back-reef seagrass beds as a potential nursery habitat, information is scarce regarding pre-settlement larvae. Using light traps anchored on the reef slopes at seagrass-replete and seagrass-free reefs (Ishigaki Island, Japan), lethrinid larvae were sampled weekly from April to June 2008. Larval abundance in light traps was similar on the 2 reef types. This result implies that lethrinid larvae did not or could not differentiate between the presence or absence of seagrass before settlement. However, in the laboratory, larvae collected from both reef types selected seagrass substrate rather than bare substrate or coral. In underwater visual censuses, newly settled juveniles were not observed on the seagrass-free reef, whereas they were abundant on the seagrass-replete reef. Together, these findings suggest that lethrinid larvae did not settle near the seagrass-free reef but rather preferentially settled near the seagrass-replete reef. © Inter-Research 2009.