215
7 Aggregation Spawning: Biological Aspects of the Early Life History
subsistence or commercial value, other than as aquarium trade fi shes in some cases.
We remain largely ignorant of much of the ELH of those larger reef fi shes with
aggregations. As Quere and Leis ( 2010 ) point out “larger species of importance to
commercial and recreational fi sheries (e.g. groupers, snappers, grunts-Haemulidae)
are particularly poorly represented in studies of larval reef-fi sh behaviour”. There is
fragmentary information on a few aggregating species, such as Nassau grouper,
but along with concerns regarding human impacts on aggregations themselves,
there is a pressing need for studies of these (albeit diffi cult to work on) species of
conservation and fi sheries importance which are depleted or near extinction in
many areas.
At present, there do not seem to be major differences in or benefi ts documented
for ELH from aggregation versus other spawning strategies. Egg sizes or types,
based on the limited data available, do not appear to be correlated with aggregation
occurrence. By the time larvae are ready to begin feeding, the densities of reef fi sh
larvae with aggregation spawning are unlikely to be much different from other reef
fi shes (Chap. 6 ). Behavioural or physical processes may help to concentrate or
disperse larvae, but are not documented for the larvae of aggregating fi shes. With
the designation of large numbers of marine protected areas in low latitude regions,
often with the intention to protect reef fi sheries, understanding the larval fi sh ecology
in such regions is becoming increasingly important, but not receiving suffi cient
attention.
In many respects knowledge of ELH of aggregating species is best known for the
early life stages. Many of these fi shes are of aquaculture interest, and detailed studies
looking at the effect of variables such as temperature, turbulence, light, and salinity,
have shown that these can have major effects on survival of a cohort. When the
results of culture studies, such as specifi city of temperature for survival of Nassau
grouper through the yolk sac stage, correspond to the conditions observed in the
fi eld during the limited spawning season, this implies that culture work can provide
important insight into reasons for recruitment changes or failure. Coleman et al
( 1999 ) point out “because spawning and recruitment in aggregating spawners are
episodic events, they are subject to the vagaries of environmental conditions, and
unfavourable conditions such as low water temperature during planktonic stages
can drastically reduce year-class strength”.
The existence of critical periods, part of the match/mismatch hypothesis, does
seem to occur in ELH. As long as conditions are suitable for life through the yolk
sac stage, the initiation of feeding is the fi rst major bottleneck in life history. Once
ready to feed the time window to begin feeding is relatively short (Yoseda et al.
2006 ) . Being ready to start feeding at sunset is probably not benefi cial to early
larvae, which are also unlikely to be able to feed at night, and having to wait 12 h
before being able to feed will probably ensure that most larvae will soon starve.
The eggs and yolk sac larvae are ‘drifters’ initially not active in promoting their
retention or dispersal. These are largely determined by where and when they are
spawned and it is likely drifters or dye studies could provide reasonable estimates of
transport. At the end of the yolk sac stage, swimming ability is limited and directed
towards feeding and perhaps making diel vertical migrations in response to
light. Passive drifting raises the problem of “wash out”, in which larvae would be
7 Aggregation Spawning: Biological Aspects of the Early Life History
subsistence or commercial value, other than as aquarium trade fi shes in some cases.
We remain largely ignorant of much of the ELH of those larger reef fi shes with
aggregations. As Quere and Leis ( 2010 ) point out “larger species of importance to
commercial and recreational fi sheries (e.g. groupers, snappers, grunts-Haemulidae)
are particularly poorly represented in studies of larval reef-fi sh behaviour”. There is
fragmentary information on a few aggregating species, such as Nassau grouper,
but along with concerns regarding human impacts on aggregations themselves,
there is a pressing need for studies of these (albeit diffi cult to work on) species of
conservation and fi sheries importance which are depleted or near extinction in
many areas.
At present, there do not seem to be major differences in or benefi ts documented
for ELH from aggregation versus other spawning strategies. Egg sizes or types,
based on the limited data available, do not appear to be correlated with aggregation
occurrence. By the time larvae are ready to begin feeding, the densities of reef fi sh
larvae with aggregation spawning are unlikely to be much different from other reef
fi shes (Chap. 6 ). Behavioural or physical processes may help to concentrate or
disperse larvae, but are not documented for the larvae of aggregating fi shes. With
the designation of large numbers of marine protected areas in low latitude regions,
often with the intention to protect reef fi sheries, understanding the larval fi sh ecology
in such regions is becoming increasingly important, but not receiving suffi cient
attention.
In many respects knowledge of ELH of aggregating species is best known for the
early life stages. Many of these fi shes are of aquaculture interest, and detailed studies
looking at the effect of variables such as temperature, turbulence, light, and salinity,
have shown that these can have major effects on survival of a cohort. When the
results of culture studies, such as specifi city of temperature for survival of Nassau
grouper through the yolk sac stage, correspond to the conditions observed in the
fi eld during the limited spawning season, this implies that culture work can provide
important insight into reasons for recruitment changes or failure. Coleman et al
( 1999 ) point out “because spawning and recruitment in aggregating spawners are
episodic events, they are subject to the vagaries of environmental conditions, and
unfavourable conditions such as low water temperature during planktonic stages
can drastically reduce year-class strength”.
The existence of critical periods, part of the match/mismatch hypothesis, does
seem to occur in ELH. As long as conditions are suitable for life through the yolk
sac stage, the initiation of feeding is the fi rst major bottleneck in life history. Once
ready to feed the time window to begin feeding is relatively short (Yoseda et al.
2006 ) . Being ready to start feeding at sunset is probably not benefi cial to early
larvae, which are also unlikely to be able to feed at night, and having to wait 12 h
before being able to feed will probably ensure that most larvae will soon starve.
The eggs and yolk sac larvae are ‘drifters’ initially not active in promoting their
retention or dispersal. These are largely determined by where and when they are
spawned and it is likely drifters or dye studies could provide reasonable estimates of
transport. At the end of the yolk sac stage, swimming ability is limited and directed
towards feeding and perhaps making diel vertical migrations in response to
light. Passive drifting raises the problem of “wash out”, in which larvae would be