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P.L. Colin
increasingly dispersed from their natal region and some mechanisms described in
Chap. 6 which serve to limit this. Once feeding is successfully initiated, for reef fi sh
larvae in general, under normal conditions starvation may not be an overriding
factor in mortality (Llopiz and Cowen 2009a, b ) . Potentially, predation may have
equal or greater importance in larval mortality.
The relative importance of physical versus biological mechanisms of retention
will likely change as presettlement fi shes develop (Leis and McCormick 2002 ) .
Once established in the pelagic environment early stage larvae transition within
2 weeks or less to post-fl exion larvae, capable of more extensive swimming and
daily vertical movements. Post-fl exion larvae may be able to seek out and stay with
concentrations of food items, perhaps seeking out convergent fronts with more food
items, but also potentially more larval predators. Structures, such as large fi n spines in
grouper/snapper larvae and spines in acanthurids, may develop that reduce the potential
for predation and enhance survival in shallow oceanic waters. Larvae remain nearly
transparent, refl ective pigment found over the gut area and only those areas necessary
to be pigmented, such as the eyes, are easily visible.
While middle and late-stage larval fi shes from aggregations are able to swim
capably (Stobutzki and Bellwood 1997 ) , there is, as yet, no strong evidence they
school (Leis 2006 ) or utilize the epibenthos during their ELH. Leis ( 2006 ) points
out “where occupancy of the epibenthic boundary layer has been looked for, it has
generally been found, but only in a minority of the species” (e.g. gobiids, sciaenids).
For most reef fi shes available evidence indicates ELH stages occurring well above
the epibenthic. Also, while the possibility of active navigation to settlement habitat
through sensory means (hearing, olfaction, wave motion detection, rheotaxis, magnetic
sense) has been suggested by numerous authors (Tolimieri et al. 2000 ; Leis and
Carson-Ewart 2003 ; Simpson et al. 2004 ; Leis and Lockett 2005 ; Montgomery et al.
2006 ; Gerlach et al. 2007 ; Dixson et al. 2008 ) , there are numerous caveats evident
in any application of such information in a broad oceanographic sense. For example,
Heenan et al. ( 2008 ) commented that all earlier studies on the response of settlement stage larvae using acoustic playback to assess auditory attraction had been
done in the same location, often with the single same reef sound recording, and use
of a reef sound recording from a different area, did not attract fi shes. Most studies
have relied on a small suite of families, usually fi shes with demersal or orallybrooded eggs, with experiments being carried out either in small fl umes or in reef
waters on broad continental shelves (Great Barrier Reef lagoon), and are considered
applicable only in situations where reefs are from a few 100 of metres to perhaps
1 km away from settlement-stage larvae.
Whether the sensory abilities of settlement stage pelagic larvae are capable of
fi nding reefs from many miles at sea has not been conclusively demonstrated. New
efforts, such as the “orientation with no frame of reference” effort (Paris et al. 2008 )
hold promise of providing detailed information on the behaviour of larvae at sea and
how they use their sensory capabilities to locate settlement habitat. Retention mechanisms may help to keep late stage larvae within recruitment range of some reefs,
but the occurrence of settlement stage fi sh far at sea shows the “leaky” nature of
the system. For most aggregation spawned fi shes “self recruitment” is unlikely,
P.L. Colin
increasingly dispersed from their natal region and some mechanisms described in
Chap. 6 which serve to limit this. Once feeding is successfully initiated, for reef fi sh
larvae in general, under normal conditions starvation may not be an overriding
factor in mortality (Llopiz and Cowen 2009a, b ) . Potentially, predation may have
equal or greater importance in larval mortality.
The relative importance of physical versus biological mechanisms of retention
will likely change as presettlement fi shes develop (Leis and McCormick 2002 ) .
Once established in the pelagic environment early stage larvae transition within
2 weeks or less to post-fl exion larvae, capable of more extensive swimming and
daily vertical movements. Post-fl exion larvae may be able to seek out and stay with
concentrations of food items, perhaps seeking out convergent fronts with more food
items, but also potentially more larval predators. Structures, such as large fi n spines in
grouper/snapper larvae and spines in acanthurids, may develop that reduce the potential
for predation and enhance survival in shallow oceanic waters. Larvae remain nearly
transparent, refl ective pigment found over the gut area and only those areas necessary
to be pigmented, such as the eyes, are easily visible.
While middle and late-stage larval fi shes from aggregations are able to swim
capably (Stobutzki and Bellwood 1997 ) , there is, as yet, no strong evidence they
school (Leis 2006 ) or utilize the epibenthos during their ELH. Leis ( 2006 ) points
out “where occupancy of the epibenthic boundary layer has been looked for, it has
generally been found, but only in a minority of the species” (e.g. gobiids, sciaenids).
For most reef fi shes available evidence indicates ELH stages occurring well above
the epibenthic. Also, while the possibility of active navigation to settlement habitat
through sensory means (hearing, olfaction, wave motion detection, rheotaxis, magnetic
sense) has been suggested by numerous authors (Tolimieri et al. 2000 ; Leis and
Carson-Ewart 2003 ; Simpson et al. 2004 ; Leis and Lockett 2005 ; Montgomery et al.
2006 ; Gerlach et al. 2007 ; Dixson et al. 2008 ) , there are numerous caveats evident
in any application of such information in a broad oceanographic sense. For example,
Heenan et al. ( 2008 ) commented that all earlier studies on the response of settlement stage larvae using acoustic playback to assess auditory attraction had been
done in the same location, often with the single same reef sound recording, and use
of a reef sound recording from a different area, did not attract fi shes. Most studies
have relied on a small suite of families, usually fi shes with demersal or orallybrooded eggs, with experiments being carried out either in small fl umes or in reef
waters on broad continental shelves (Great Barrier Reef lagoon), and are considered
applicable only in situations where reefs are from a few 100 of metres to perhaps
1 km away from settlement-stage larvae.
Whether the sensory abilities of settlement stage pelagic larvae are capable of
fi nding reefs from many miles at sea has not been conclusively demonstrated. New
efforts, such as the “orientation with no frame of reference” effort (Paris et al. 2008 )
hold promise of providing detailed information on the behaviour of larvae at sea and
how they use their sensory capabilities to locate settlement habitat. Retention mechanisms may help to keep late stage larvae within recruitment range of some reefs,
but the occurrence of settlement stage fi sh far at sea shows the “leaky” nature of
the system. For most aggregation spawned fi shes “self recruitment” is unlikely,