Identification of nursery habitats for commercially valuable humphead wrasse Cheilinus undulatus and large groupers (Pisces: Serranidae) in Palau

In recent years there has been increasing interest in conserving fish habitats. However, fish-habitat associations, particularly nursery habitat for early juvenile stages, are poorly known for most reef fishes. Using mark-recapture techniques, I examined among-habitat variation in settlement, post-settlement growth, and persistence, and movement in 3 large, vulnerable, and commercially important reef fishes: the humphead wrasse Cheilinus undulatus, the squaretail coralgrouper Plectropomus areolatus, and the camouflage grouper Epinephelus polyphekadion. Both the humphead wrasse and the coralgrouper appeared to utilize specific nursery habitats. Settlement, growth, and persistence of humphead wrasse were highest in branching coral structures mixed with bushy macroalgae (BCMA). Of all tagged C. undulatus recaptured, in intermediate or adult habitats, 80% were tagged post-settlement in BCMA. Early juvenile P. areolatus were found almost exclusively in coral rubble habitats on the slopes of tidal channels, at a narrow depth range of 5 to 7 m, This dependence on one habitat type could render this species vulnerable to shipping or dredging operations or other forms of coastal development. E. polyphekadion appeared to be a habitat generalist, and no specific nursery habitat could be identified. In summary, spatial management (e.g. implementation of marine protected areas) should prioritize habitats for conservation according to their value as essential nursery or spawning habitats for target species needing protection.