143
5 Timing and Location of Aggregation and Spawning in Reef Fishes
reefs, the differences are marked. In Bermuda (32°N) the winter solstice day is
10:01 h long and the summer solstice 14:17 h, a 40% difference of 4:16 h.
All known RA fi shes are diurnally active species. For TA species, many are
active both day and night (groupers, snappers). For largely nocturnal fi shes (e.g.
squirrelfi shes – Holocentridae, bigeyes – Priacanthidae) it is not known how and
when they spawn, but aggregation spawning is possible. In the TWA large TA
fi shes, for which there is information, spawn from very late in the afternoon to
sunset. Nassau grouper spawn in a narrow time window from about 20 min before
to 20 min after sunset (Colin 1992 ; Sadovy et al. 1994 ; Whaylen et al. 2004 ) . Other
TWA groupers are similar (Colin et al. 1987 ) while cubera snapper spawn in the
hour before sunset (Heyman et al. 2005 ; Kadison et al. 2006 ) . In the EP Sala et al.
( 2003 ) found the snapper L. argentiventris to spawn within 1 h of sunset in Gulf
of California.
Other species may not be so tied to a particular time of day. In the EP Sala et al.
( 2003 ) found Pacifi c dog snapper, Lutjanus novemfasciatus , spawned at 2 pm along
reef walls while bigeye trevally, Caranx sexfasciatus , spawned as pairs out of an
aggregating school during the day at no specifi c times (Chap. 12.18 ). Less is known
for IWP TA species, but some IWP snappers are now known to spawn in the early
morning (blue-lined sea bream and twin-spot snapper) on outer reef faces (Chap. 12.11 ).
Many attempts to observe spawning by IWP TA groupers have been unsuccessful, but
camoufl age grouper have been observed spawning just after dawn (Chap. 12.5 ). Some
of these species may be spawning in the middle of the night (Rhodes and Sadovy
2002 ) . The only IWP grouper with numerous sunset spawning observations is leopard
coralgrouper and its behaviour appears to be intermediate between a RA and TA
species (Chap. 12.9 ). Hamilton ( 2005 ) reports on reliable observations of the spawning by the longfi n emperor, Lethrinus erythrocles , near midnight.
RA fi shes in the IWP in areas with moderate to high tidal amplitudes have a different pattern with nearly all spawning starting after high tide and lasting for 1–2 h.
Along the lengthy barrier reef of Palau, RA species as well as more numerous harem
and pair spawners (PS), spawn on the seaward edge of the reef crest after the high
tide (Robertson 1983 , PLC unpublished data) at times ranging from near dawn to
sunset. Newly shed and fertilized RA and harem/pair-spawned eggs are essentially
the same (size, transparency, buoyancy) and have a similar pattern of advection off
the reef (Hamner et al. 2007 ) . While spawning starts just after high tide, in some
areas there appears a sequence to the spawning by 20–40 species (only 2–3 of those
RA spawners) most over the period of 60–90 min after high tide. The humphead
wrasse is the fi nal species to spawn, starting until 2–2.5 h after high tide (Colin 2010 ) .
By the time it is fi nished for the day, no other RA or PS fi shes remain spawning.
A few RA species are believed to spawn only in the morning. The bumphead
parrotfi sh, Bolbometopon muricatum , spawns as pairs out of larger schools from
just after dawn (Gladstone 1986 , PLC unpublished data) to late morning (Mandy
Etpison personal observation), but not during the afternoon (Chap. 12.15 ). Some
other large, but non-aggregating, IWP parrotfi sh are also only known to spawn in
the morning (Colin and Bell 1991 ) . The bullethead parrotfi sh, a small RA fi sh,
group-spawned after high tides only from early morning to early afternoon in
5 Timing and Location of Aggregation and Spawning in Reef Fishes
reefs, the differences are marked. In Bermuda (32°N) the winter solstice day is
10:01 h long and the summer solstice 14:17 h, a 40% difference of 4:16 h.
All known RA fi shes are diurnally active species. For TA species, many are
active both day and night (groupers, snappers). For largely nocturnal fi shes (e.g.
squirrelfi shes – Holocentridae, bigeyes – Priacanthidae) it is not known how and
when they spawn, but aggregation spawning is possible. In the TWA large TA
fi shes, for which there is information, spawn from very late in the afternoon to
sunset. Nassau grouper spawn in a narrow time window from about 20 min before
to 20 min after sunset (Colin 1992 ; Sadovy et al. 1994 ; Whaylen et al. 2004 ) . Other
TWA groupers are similar (Colin et al. 1987 ) while cubera snapper spawn in the
hour before sunset (Heyman et al. 2005 ; Kadison et al. 2006 ) . In the EP Sala et al.
( 2003 ) found the snapper L. argentiventris to spawn within 1 h of sunset in Gulf
of California.
Other species may not be so tied to a particular time of day. In the EP Sala et al.
( 2003 ) found Pacifi c dog snapper, Lutjanus novemfasciatus , spawned at 2 pm along
reef walls while bigeye trevally, Caranx sexfasciatus , spawned as pairs out of an
aggregating school during the day at no specifi c times (Chap. 12.18 ). Less is known
for IWP TA species, but some IWP snappers are now known to spawn in the early
morning (blue-lined sea bream and twin-spot snapper) on outer reef faces (Chap. 12.11 ).
Many attempts to observe spawning by IWP TA groupers have been unsuccessful, but
camoufl age grouper have been observed spawning just after dawn (Chap. 12.5 ). Some
of these species may be spawning in the middle of the night (Rhodes and Sadovy
2002 ) . The only IWP grouper with numerous sunset spawning observations is leopard
coralgrouper and its behaviour appears to be intermediate between a RA and TA
species (Chap. 12.9 ). Hamilton ( 2005 ) reports on reliable observations of the spawning by the longfi n emperor, Lethrinus erythrocles , near midnight.
RA fi shes in the IWP in areas with moderate to high tidal amplitudes have a different pattern with nearly all spawning starting after high tide and lasting for 1–2 h.
Along the lengthy barrier reef of Palau, RA species as well as more numerous harem
and pair spawners (PS), spawn on the seaward edge of the reef crest after the high
tide (Robertson 1983 , PLC unpublished data) at times ranging from near dawn to
sunset. Newly shed and fertilized RA and harem/pair-spawned eggs are essentially
the same (size, transparency, buoyancy) and have a similar pattern of advection off
the reef (Hamner et al. 2007 ) . While spawning starts just after high tide, in some
areas there appears a sequence to the spawning by 20–40 species (only 2–3 of those
RA spawners) most over the period of 60–90 min after high tide. The humphead
wrasse is the fi nal species to spawn, starting until 2–2.5 h after high tide (Colin 2010 ) .
By the time it is fi nished for the day, no other RA or PS fi shes remain spawning.
A few RA species are believed to spawn only in the morning. The bumphead
parrotfi sh, Bolbometopon muricatum , spawns as pairs out of larger schools from
just after dawn (Gladstone 1986 , PLC unpublished data) to late morning (Mandy
Etpison personal observation), but not during the afternoon (Chap. 12.15 ). Some
other large, but non-aggregating, IWP parrotfi sh are also only known to spawn in
the morning (Colin and Bell 1991 ) . The bullethead parrotfi sh, a small RA fi sh,
group-spawned after high tides only from early morning to early afternoon in