Short-term effects of tidal range on juvenile fish communities in fringing coral reefs (Mayotte Island, Indian Ocean)

Abstract : The present study investigated the effects of tidal state (ebb vs. rising tide) on juvenile fish communities on three reef flats at Mayotte Island (Indian Ocean). Diurnal underwater visual surveys recorded 11,289 juveniles from 102 species during October-November 2011. Juvenile fishes were separated into three categories according to their habitat dependence: transient, semi-transient and resident. The three-factor ANOVA showed that the fish density differed significantly according to tidal range (p = 0.006) and habitat dependence (p = 0.001), and not according to sites (p = 0.316). Thus, transient fishes were mainly present on the fringing reef flats at rising tide and changed in abundance with tidal state, while resident fish groups differed little during tidal state. Overall, these results suggest that transient fishes would use the reef flat only as a temporary habitat at high tide, while resident fish would use the reef flat during all conditions of tidal flow.