The Influence of Adults of Some Coral Reef Fishes on Larval Recruitment

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Abstract
I examined the recruitment of reef fishes to isolated experimental standard—size coral colonies supporting residents of each of four planktivorous fishes: (a) Dascyllus aruanus, (b) D. reticulatus (both at several densities), (c) Chromis caerulea, or (d) Pomacentrus popei. I removed all recruits at approximately weekly intervals, and summed larval recruitment over each of two settlement seasons. I found two types of interactions between resident fishes and recruits: (1) There was increased settlement of three species in sites where there were resident conspecifics. This appears to be due to habitat selection by settling larvae. More larval D. aruanus, D. reticulatus, and C. caerulea recruited to corals with resident conspecifics than to corals with other congeners or vacant control corals. In addition, corals with the highest densities of resident D. aruanus and D. reticulatus received the most conspecific recruits. (2) The presence of high densities of resident D. aruanus and D. reticulatus reduced recruitment of heterospecific larvae in all cases for which data were sufficient to allow a powerful test. The presence of C. caerulea reduced recruitment of some species but not others. This interspecific effect could be due to habitat selection by settling larvae, and/or emigration and mortality caused by aggressive interactions with residents. Some species were unaffected by the presence of resident P. popei, but the data for most species were inconclusive. Interactions of the first type may be the cause of the clumped distributions of other reef fishes, though this does not seem to hold in some known instances. Interactions of the second type do not seem to be directly related to resource availability. There are biological and statistical reasons why the likelihood of finding such interactions will be positively correlated with the supply of recruits. The general significance of these interactions for the structure of reef fish assemblages will depend on (1) the level of larval supply, and (2) the number and abundance of species that show this kind of behavior.