141
5 Timing and Location of Aggregation and Spawning in Reef Fishes
about 91 h and 88 h at 25.5°C. In the fi eld spawning occurred around sunset with the
day-night length in the Bahamas approximately 11–13 h during December–January
(Colin 1992 ) . Dawn after the fourth night post-spawning would occur around 85 h
after fertilization. At 26°C larvae would be ready to begin feeding an hour or two
after sunrise on that morning (Fig. 5.18 ) and would have nearly a full day in which
to initiate feeding, helping to ensure that the larvae will survive the upcoming night
when feeding may not be possible. Larvae would be ready to feed in the middle of
night if reared at 28°C and at sunset on the fourth night at 30°C (Fig. 5.18 ).
Is temperature similarly important among other TA species? Unfortunately few
data on time to fi rst feeding versus temperature, or indeed in relation to spawning,
are available for other reef fi shes. Sheaves ( 2006 ) suggested that early life history
stages of sparid fi shes (porgies) might be intolerant of higher water temperatures
and that spawning (not necessarily aggregation-spawning) during cool periods by
those found in warmer water might be a tactic for survival in such waters. Samoilys
( 1997 ) found leopard coralgrouper aggregations on the Great Barrier Reef to occur
at temperatures between 24.25°C and 28.5°C, within an overall annual range of
about 23–30°C. Ulong Channel in Palau had an annual water temperature range of
1.5°C (28.0–29.5°C) with two groupers aggregated during limited temperature
ranges (28.5–29.5°C for brown-marbled grouper, E. fuscoguttatus and squaretail
coralgroupe r ) while a third had a more in limited temperature range (29.0–29.5°C
for camoufl age grouper, Epinephelus polyphekadion ) (Fig. 5.17 ). In Fiji the same
species aggregated at temperatures of approximately 24°C with an annual temperature range at aggregation site is about 24–28.5°C (Yvonne Sadovy de Mitcheson
unpublished data). Perhaps the Fijian populations have different rates of development through the yolk sac larvae, or perhaps, if rates are the same, have the time
between spawning and fi rst feeding lengthened by one day in the cooler water temperatures of Fiji, still allowing fi rst feeding to start early in the day. Alternatively,
they appear to spawn at the lowest point of the annual temperature cycle so this may
be a cue for adults. Kadison et al. ( 2006 ) found cubera snapper spawning in the US
Virgin Islands at temperatures above 26.9°C to nearly 28°C, but unfortunately comparative data are not available for this species from other areas. If data are gathered
on annual temperature regimes, as well as studies of egg and early larval development conducted related to temperature (often from aquaculture), it will become
possible to test ideas of the possible importance of temperature in early life history
and whether this is a general principle related to reef fish aggregation. The
documentation of temperature at spawning sites is a simple, inexpensive standard
activity and should be regularly conducted (Chap. 9 ).
Drop-off areas where most TA fi shes aggregate generally have cooler water at
depths not very far below aggregation areas. Thus fi shes can infl uence their temperature
regime by simply varying the depth at which they reside. Starr et al. ( 2007 ) documented a fascinating instance where Nassau grouper at Lighthouse Reef, Belize,
moved from the normal shallow water (less than 30 m) habitats to deeper (60–70 m
depth) water after their January spawning aggregation. Several possible reasons
for this change can be suggested, selection for a preferred temperature being one
of them.
5 Timing and Location of Aggregation and Spawning in Reef Fishes
about 91 h and 88 h at 25.5°C. In the fi eld spawning occurred around sunset with the
day-night length in the Bahamas approximately 11–13 h during December–January
(Colin 1992 ) . Dawn after the fourth night post-spawning would occur around 85 h
after fertilization. At 26°C larvae would be ready to begin feeding an hour or two
after sunrise on that morning (Fig. 5.18 ) and would have nearly a full day in which
to initiate feeding, helping to ensure that the larvae will survive the upcoming night
when feeding may not be possible. Larvae would be ready to feed in the middle of
night if reared at 28°C and at sunset on the fourth night at 30°C (Fig. 5.18 ).
Is temperature similarly important among other TA species? Unfortunately few
data on time to fi rst feeding versus temperature, or indeed in relation to spawning,
are available for other reef fi shes. Sheaves ( 2006 ) suggested that early life history
stages of sparid fi shes (porgies) might be intolerant of higher water temperatures
and that spawning (not necessarily aggregation-spawning) during cool periods by
those found in warmer water might be a tactic for survival in such waters. Samoilys
( 1997 ) found leopard coralgrouper aggregations on the Great Barrier Reef to occur
at temperatures between 24.25°C and 28.5°C, within an overall annual range of
about 23–30°C. Ulong Channel in Palau had an annual water temperature range of
1.5°C (28.0–29.5°C) with two groupers aggregated during limited temperature
ranges (28.5–29.5°C for brown-marbled grouper, E. fuscoguttatus and squaretail
coralgroupe r ) while a third had a more in limited temperature range (29.0–29.5°C
for camoufl age grouper, Epinephelus polyphekadion ) (Fig. 5.17 ). In Fiji the same
species aggregated at temperatures of approximately 24°C with an annual temperature range at aggregation site is about 24–28.5°C (Yvonne Sadovy de Mitcheson
unpublished data). Perhaps the Fijian populations have different rates of development through the yolk sac larvae, or perhaps, if rates are the same, have the time
between spawning and fi rst feeding lengthened by one day in the cooler water temperatures of Fiji, still allowing fi rst feeding to start early in the day. Alternatively,
they appear to spawn at the lowest point of the annual temperature cycle so this may
be a cue for adults. Kadison et al. ( 2006 ) found cubera snapper spawning in the US
Virgin Islands at temperatures above 26.9°C to nearly 28°C, but unfortunately comparative data are not available for this species from other areas. If data are gathered
on annual temperature regimes, as well as studies of egg and early larval development conducted related to temperature (often from aquaculture), it will become
possible to test ideas of the possible importance of temperature in early life history
and whether this is a general principle related to reef fish aggregation. The
documentation of temperature at spawning sites is a simple, inexpensive standard
activity and should be regularly conducted (Chap. 9 ).
Drop-off areas where most TA fi shes aggregate generally have cooler water at
depths not very far below aggregation areas. Thus fi shes can infl uence their temperature
regime by simply varying the depth at which they reside. Starr et al. ( 2007 ) documented a fascinating instance where Nassau grouper at Lighthouse Reef, Belize,
moved from the normal shallow water (less than 30 m) habitats to deeper (60–70 m
depth) water after their January spawning aggregation. Several possible reasons
for this change can be suggested, selection for a preferred temperature being one
of them.