Spatial and behavioural patterns of reef habitat settlement by fish larvae

The transition from a pelagic oceanic environment to a benthic reef environment, during which the relationship between the organism and its environment changes radically, is a particularly dangerous phase of the life cycle of marine organisms. To explore this transition phase in coral reef fish, I worked in Moorea Island lagoon, where oceanic larvae enter the lagoon across the reef crest by night. The fish larvae were captured by night with crest nets, then tagged and released in the lagoon. The day following the night of 'capture-tag-release', I surveyed the lagoon to determine the first benthic habitat of tagged fish. Based on spatial and behavioural components, 4 settlement patterns were highlighted: larvae settled either into the benthic habitat occupied by juveniles of their species (Pattern 1) or into a pre-settlement habitat (Pattern 2) on the first day after reef colonisation, and larvae had either similar behaviour to juveniles (Pattern A), or a cryptic lifestyle (Pattern B). Among the 25 species studied, 13 had settlement Pattern 1A (e.g. Chromis viridis, Acanthurus triostegus), 5 had Pattern 1 B (e. g. Lutjanus fulvus, Centropyge flavissimus), 4 had Pattern 2A (e. g. Apogon frenatus, Stegastes nigricans) and 3 had Pattern 2B (e.g. Gymnothorax sp., Scorpaenodes guamensis). Overall, the present study is the first to explore the use of the first larval benthic habitat by a broad range of fish taxa. The most widespread settlement pattern observed (13 out of 25 species) was that which minimises the transition time between pelagic life and life on the reef, namely, larvae going directly to their settlement habitat and immediately acquiring the lifestyle of juveniles.