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J.H. Choat
The focus of this chapter will therefore be the demographic and evolutionary
relationships of the above four perciform families and the extent to which these
help explain the phenomenon of aggregation spawning. Two types of ecological
factors are considered (1) basic biological features such as body size, feeding mode
and functional anatomy and (2) life history information, including longevity, age
structure, growth rates and patterns of sexual development such as sex-reversal. A
major conclusion is that the capacity of reef fi shes to form different types of spawning aggregations is governed by basic rules of size, trophic ecology, anatomy and
physiology. Groups that made up the different spawning modes shared common
properties of size, nutritional ecology and anatomy. Whether they were protogynous or gonochoristic or had short or long generation times was a secondary
consideration.
Advection of eggs and larvae away from reef habitats dominated by plankton
feeders is hypothesized to be an important aspect of the development of aggregate
spawning. Regardless of whether the propagules are retained near the reef or dispersed
into oceanic waters the important consequence is that the initial stages of development occur in waters away from the reef habitats where there are high predation
rates on plankton (Chap. 7 ). Advection may be achieved by spawning in areas subject to reef (Heyman and Kjervfe 2008 ) or tidal current systems (tidal jets associated
with reef passes) (Chap. 9 ). Spawning in areas of enhanced water movement is common to most species and does not imply either retention or broad dispersal. Larval
retention is simply one potential consequence after initial advection from reef
habitats (Chap. 6 ).
A further conclusion concerns the linkage of periodic spawning episodes to
particular oceanic conditions. This may be accomplished by restricting spawning
to particular windows in the annual cycle so as to link spawning to oceanic
regimes that result in successful larval development and growth. This is a variant
of the match/mismatch hypothesis developed to explain spawning patterns in
clupeoid fi shes (Sinclair 1988 ) . This contrasts with the patterns shown by some
species that spawn over the entire annual cycle which exposes the annual output
of propagules to a potentially greater range of environmental conditions (see also
Chap. 6 ).
Detailed descriptions of reproduction and spawning behaviour have been
compiled for only a fraction of the reef fi sh fauna; a more comprehensive set of
examples may modify these conclusions. Moreover the terms resident and transient
are not mutually exclusive and may simply represent a continuum of reproductive behaviours (Fig. 4.1 ). Whether we classify spawning aggregations as resident
or transient may depend on ocean-specifi c patterns of reef structure, a consequence of the different geological and evolutionary histories (Montaggioni and
Braithwaite 2009 ) .
A number of additional hypotheses seek to explain spawning aggregations,
many compiled by Claydon ( 2005 ) . However, given the accumulation of biological detail relevant to this topic it is an appropriate time to focus on the basic biological attributes that are important for the development and maintenance of
spawning aggregations and the processes that underlie the evolution of spawning
aggregations.
J.H. Choat
The focus of this chapter will therefore be the demographic and evolutionary
relationships of the above four perciform families and the extent to which these
help explain the phenomenon of aggregation spawning. Two types of ecological
factors are considered (1) basic biological features such as body size, feeding mode
and functional anatomy and (2) life history information, including longevity, age
structure, growth rates and patterns of sexual development such as sex-reversal. A
major conclusion is that the capacity of reef fi shes to form different types of spawning aggregations is governed by basic rules of size, trophic ecology, anatomy and
physiology. Groups that made up the different spawning modes shared common
properties of size, nutritional ecology and anatomy. Whether they were protogynous or gonochoristic or had short or long generation times was a secondary
consideration.
Advection of eggs and larvae away from reef habitats dominated by plankton
feeders is hypothesized to be an important aspect of the development of aggregate
spawning. Regardless of whether the propagules are retained near the reef or dispersed
into oceanic waters the important consequence is that the initial stages of development occur in waters away from the reef habitats where there are high predation
rates on plankton (Chap. 7 ). Advection may be achieved by spawning in areas subject to reef (Heyman and Kjervfe 2008 ) or tidal current systems (tidal jets associated
with reef passes) (Chap. 9 ). Spawning in areas of enhanced water movement is common to most species and does not imply either retention or broad dispersal. Larval
retention is simply one potential consequence after initial advection from reef
habitats (Chap. 6 ).
A further conclusion concerns the linkage of periodic spawning episodes to
particular oceanic conditions. This may be accomplished by restricting spawning
to particular windows in the annual cycle so as to link spawning to oceanic
regimes that result in successful larval development and growth. This is a variant
of the match/mismatch hypothesis developed to explain spawning patterns in
clupeoid fi shes (Sinclair 1988 ) . This contrasts with the patterns shown by some
species that spawn over the entire annual cycle which exposes the annual output
of propagules to a potentially greater range of environmental conditions (see also
Chap. 6 ).
Detailed descriptions of reproduction and spawning behaviour have been
compiled for only a fraction of the reef fi sh fauna; a more comprehensive set of
examples may modify these conclusions. Moreover the terms resident and transient
are not mutually exclusive and may simply represent a continuum of reproductive behaviours (Fig. 4.1 ). Whether we classify spawning aggregations as resident
or transient may depend on ocean-specifi c patterns of reef structure, a consequence of the different geological and evolutionary histories (Montaggioni and
Braithwaite 2009 ) .
A number of additional hypotheses seek to explain spawning aggregations,
many compiled by Claydon ( 2005 ) . However, given the accumulation of biological detail relevant to this topic it is an appropriate time to focus on the basic biological attributes that are important for the development and maintenance of
spawning aggregations and the processes that underlie the evolution of spawning
aggregations.