Mc. Ohman et al., SETTLEMENT STRATEGIES AND DISTRIBUTION PATTERNS OF CORAL-REEF FISHES, Journal of experimental marine biology and ecology, 225(2), 1998, pp. 219-238
Patterns of habitat use established at settlement may be a primary det
erminant of the distribution of coral-reef fishes within and among hab
itats. However, due to the difficulty of observing fish larvae in the
wild, the behaviour of individuals at settlement has rarely been obser
ved. Here, we examined the behaviour at settlement of five species of
damselfishes (family Pomacentridae) by conducting multi-choice experim
ents in large outdoor aquaria at Lizard Island on the Great Barrier Re
ef, Australia. Late-stage larvae that were competent to settle were co
llected using light traps and placed in large circular aquaria at nigh
t where they could choose to settle among live coral, dead branching c
oral, coral rubble and bare sand habitats. We examined patterns of hab
itat choice at settlement by larvae with no prior experience of the re
ef (naive larvae). The effect of experience in the reef environment on
habitat preferences was then determined by studying the behaviour of
juveniles collected soon after settlement and exposed to the same expe
rimental protocol. We also examined the importance of interspecific in
teractions among late-stage larvae and interactions between newly sett
led juveniles and adults in determining patterns of habitat choice exh
ibited by larvae and newly settled juveniles. Late-stage larvae and ne
wly settled juveniles made distinct habitat choices but the choices ma
de varied widely among species. Chromis viridis (Cuvier) late-stage la
rvae selected live coral and always settled as a group. Post-settlemen
t C. viridis also selected live coral but exhibited stronger schooling
behaviour and moved around the aquaria more frequently than late-stag
e larvae. Pomacentrus moluccensis (Bleeker) consistently selected live
coral and also preferentially selected habitats where conspecifics, e
ither settlers or adults, were present. P. amboinensis (Bleeker) late-
stage larvae preferentially selected both Live and dead standing coral
habitats but avoided coral rubble. Post-settlement P. amboinensis sel
ected live coral more frequently than late-stage larvae. P, coelestis
(Jordan and Starks) late-stage larvae initially settled with equal fre
quency among the habitats presented but exhibited an increasing use of
coral rubble and dead coral throughout the day. In contrast, early po
st-settlers always selected the coral rubble habitat with significantl
y greater frequency than other habitats. Therefore, experience on the
reef may be associated with habitat preferences in P. coelestis. P. ch
rysurus settlers were distributed evenly among habitats due to agonist
ic interactions among individuals observed within hours of settling. A
lso, early post-settlement P. chrysurus avoided habitats containing ad
ults. For the pomacentrids we tested, the patterns of habitat selectio
n observed in our experiments were similar to the distribution of adul
ts among habitats on the reef at Lizard Island. Also, interactions amo
ng individuals at settlement could explain the spacing of individuals
within habitats. Therefore, precise selection of habitats at settlemen
t and behaviour among conspecifics within hours of settling may have a
major influence on the distribution of coral-reef fishes within and a
mong habitats. (C) 1998 Elsevier Science B.V.