Microhabitat utilisation patterns in cryptobenthis coral reef fish communities

Abstract

The cryptobenthic reef fish communities from four microhabitats at Orpheus Island, central Great Barrier Reef are described. Eighty-four 0.4m2 samples yielded a total of 368 individuals from 42 species in eight families, with a mean density of 11 individuals m–2 (±1.7SE) and 2.9 species 0.4 m–2 (±0.2SE). Caves contained the highest number of both individuals (120) and species (26), followed by sand/rubble, soft coral, and open reefs. Microhabitat associations included cave and soft coral specialists. Site fidelity in 71 tagged individuals of 4 species was high, with a mean recapture rate of 53% (±8.4SE) remaining within the ~0.4 m2 sampling area after a 48-h period. Behavioural observations also reflect this limited movement, with the dominant mode of behaviour in 7 species being a motionless state (67.5% ±11.6SE), followed by feeding (21.8% ±8.7SE), hiding (6.3% ±1.6SE), and swimming (4.4% ±1.5SE). Two distinct behavioural groups are identified: (1) sedentary forms, characterised by long periods of immobility (5 species); and (2) winnowers, characterised by long feeding bouts (2 species). The fine-scale partitioning of microhabitats, restricted home ranges, and sedentary behaviour of many cryptobenthic reef fish species suggest that this reef fish community exhibits similar patterns of habitat utilisation to their larger reef-fish counterparts, but at a much finer scale.