Settlement behaviour of coral-reef fish larvae at subsurface artificial-reef moorings

Abstract

Artificial-reef units (rolls of plastic garden mesh) attached to subsurface floats were used to study settlement behaviour of larval reef fishes. These units were located 3, 5, 7 and 9 m above the bottom in water 15–19 m deep in the Great Barrier Reef Lagoon, 1 km from natural reefs. Larvae of 50 species (15 families) settled on these units. The nine most abundant reef-fish taxa were in the families Apogonidae, Blenniidae, Gobiidae, Monacanthidae, Pomacentridae and Tetraodontidae. The less abundant of these taxa (n = 4) settled uniformly. The more abundant taxa (n = 5) had clumped settlement. Four taxa preferred structurally complex reef units, whereas five showed no preference. Apogonids, gobiids, tetraodontids and a pomacentrid preferred deep units, one pomacentrid had no depth preference, and a blenniid and a monacanthid preferred shallow units. Experiments evaluated visual, olfactory and auditory cues that reef-fish larvae may use to locate and settle onto reefs. Visual cues (large white panels) did not enhance settlement. Experiments on olfactory cues (corals in vented containers) and auditory cues (‘the nocturnal chorus’ of tropical reefs) were compromised by low and highly variable settlement, but show the potential of the method. The advantages of subsurface moorings for study of settlement behaviour are discussed.