Field evidence that settling coral reef fish larvae detect resident fishes using dissolved chemical cues

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The presence of groups of the planktivorous damselfishes Dascyllus aruanus (L.) and D. reticulatus (Richardson) in small coral heads affects local recruitment in two ways: (1) more Dascyllus recruit to corals with resident adult conspecifics than to similar corals with no resident fishes; and (2) a number of other species recruit in higher numbers on corals without resident fish than on corals with resident Dascyllus. Such differential recruitment could be due either to selective settlement or to differential persistence. Previous studies have shown that at least two species settle selectively. Since both the species settle in darkness, settlers are unlikely to be selecting sites using vision. Two field experiments were designed to test whether settlers respond to chemical cues. Water was pumped from coral heads with resident Dascyllus and from unoccupied control corals to unoccupied experimental corals. The pumps ran all night, and all settlers were collected daily using anaesthetic. D. aruanus settlers preferred experimental corals supplied with water drawn from heads where there were resident conspecifics. More Pomacentrus sp. and P. popei (Jordan et Scale) settled on experimental corals supplied with water from control corals than on experimental corals of the other treatments. These results suggest that some coral reef fish larvae use dissolved chemical cues to choose or to avoid settlement sites.