97
4 Spawning Aggregations in Reef Fishes; Ecological and Evolutionary Processes
on the size structure and demography of prey species (Sandin et al. 2008 ) . Predation
may also have impacts on spawning individuals (Sancho et al. 2000a, b ) especially
for male participants (Clifton and Robertson 1993 ; Gust et al. 2003 , Chap. 5 ). The
impact of predation decreases with size (Hixon and Beets 1993 ; Sogard 1997 ;
Sandin et al. 2008 ; Holmes and McCormick 2009 ) . For this reason movement out of
the normal foraging range to exposed reef areas may be restricted to species that
achieve large size.
As size and density are negatively correlated (Ackerman and Bellwood 2000 )
aggregations of large individuals would need to draw on a broad habitat catchment
area to achieve the numbers observed in transient aggregations. This would require
the extensive migrations recorded for some larger aggregating species. We should
expect a strong relationship between size, the distance covered in spawning migrations and the extent to which individuals move beyond their normal foraging range.
For example Bolden ( 2000 ) recorded relatively long migrations in one of the larger
groupers, the Nassau grouper, which contrasts with a medium-sized grouper, the red
hind, Epinephelus guttatus , which migrates shorter distances – up to 33 km (Chaps. 2
and 12.3 ).
Trophic ecology will infl uence the daily activity, feeding and digestive processes
in the various families. The greatest contrasts are between those species that graze a
benthic biota including fi lamentous algae, detritus and meiofauna, and carnivores
which actively forage for large mobile prey organisms. Herbivores and detritivores
display continuous feeding activity and high food processing rates (Choat and
Clements 1998 ; Choat et al. 2004 ) . Most grazing species have consistent feeding
sites reached by local migrations and determined by structural and biological features of the reef habitat (Montgomery et al. 1989 ; Claisse et al. 2009 ) . Piscivores
and larger invertebrate carnivores forage and feed more opportunistically (Hobson
1974 , Bshary et al. 2006 ). The capacity to undergo extensive migration episodes
beyond the normal foraging reef habitat may be dependent on the extent to which
daily feeding requirements tie particular groups to specifi c reef habitats (Chap. 2 ).
In a preliminary analysis, 20 groups of reef fi shes (Table 4.8 ) were subject to an
ordination (PCA) analysis to examine the relationship between fi sh size, abundance,
and nutritional ecology in the context of spawning behaviour. Two trends were
observed (Fig. 4.2 ). PC1, which accounted for 65.8% of the variance, is shown on
the horizontal axis. This was positively correlated with mean size and negatively
correlated with abundance. PC2 accounted for 32.1% of the variance and was dominated by a trend on the vertical axis refl ecting the trophic status of the families
ranging from predominantly carnivorous groups to herbivorous and detrital feeders.
Mean body size was positively correlated with PC1 while abundance was predictably negatively correlated. Both abundance and percent carnivory in the diet were
negatively correlated with PC2.
The median size group (11–19.8 cm total length [TL]) (wrasses, anthiids, butterfl yfi shes and angelfi shes) occupied an intermediate position in the size spectrum
with the grazing groups, parrotfi shes, rabbitfi shes and surgeonfi shes (28–37.8 cm
TL) slightly larger. The largest families, including groupers, jacks, snappers and
emperors all of which are carnivores, were grouped in the right lower quadrant of
4 Spawning Aggregations in Reef Fishes; Ecological and Evolutionary Processes
on the size structure and demography of prey species (Sandin et al. 2008 ) . Predation
may also have impacts on spawning individuals (Sancho et al. 2000a, b ) especially
for male participants (Clifton and Robertson 1993 ; Gust et al. 2003 , Chap. 5 ). The
impact of predation decreases with size (Hixon and Beets 1993 ; Sogard 1997 ;
Sandin et al. 2008 ; Holmes and McCormick 2009 ) . For this reason movement out of
the normal foraging range to exposed reef areas may be restricted to species that
achieve large size.
As size and density are negatively correlated (Ackerman and Bellwood 2000 )
aggregations of large individuals would need to draw on a broad habitat catchment
area to achieve the numbers observed in transient aggregations. This would require
the extensive migrations recorded for some larger aggregating species. We should
expect a strong relationship between size, the distance covered in spawning migrations and the extent to which individuals move beyond their normal foraging range.
For example Bolden ( 2000 ) recorded relatively long migrations in one of the larger
groupers, the Nassau grouper, which contrasts with a medium-sized grouper, the red
hind, Epinephelus guttatus , which migrates shorter distances – up to 33 km (Chaps. 2
and 12.3 ).
Trophic ecology will infl uence the daily activity, feeding and digestive processes
in the various families. The greatest contrasts are between those species that graze a
benthic biota including fi lamentous algae, detritus and meiofauna, and carnivores
which actively forage for large mobile prey organisms. Herbivores and detritivores
display continuous feeding activity and high food processing rates (Choat and
Clements 1998 ; Choat et al. 2004 ) . Most grazing species have consistent feeding
sites reached by local migrations and determined by structural and biological features of the reef habitat (Montgomery et al. 1989 ; Claisse et al. 2009 ) . Piscivores
and larger invertebrate carnivores forage and feed more opportunistically (Hobson
1974 , Bshary et al. 2006 ). The capacity to undergo extensive migration episodes
beyond the normal foraging reef habitat may be dependent on the extent to which
daily feeding requirements tie particular groups to specifi c reef habitats (Chap. 2 ).
In a preliminary analysis, 20 groups of reef fi shes (Table 4.8 ) were subject to an
ordination (PCA) analysis to examine the relationship between fi sh size, abundance,
and nutritional ecology in the context of spawning behaviour. Two trends were
observed (Fig. 4.2 ). PC1, which accounted for 65.8% of the variance, is shown on
the horizontal axis. This was positively correlated with mean size and negatively
correlated with abundance. PC2 accounted for 32.1% of the variance and was dominated by a trend on the vertical axis refl ecting the trophic status of the families
ranging from predominantly carnivorous groups to herbivorous and detrital feeders.
Mean body size was positively correlated with PC1 while abundance was predictably negatively correlated. Both abundance and percent carnivory in the diet were
negatively correlated with PC2.
The median size group (11–19.8 cm total length [TL]) (wrasses, anthiids, butterfl yfi shes and angelfi shes) occupied an intermediate position in the size spectrum
with the grazing groups, parrotfi shes, rabbitfi shes and surgeonfi shes (28–37.8 cm
TL) slightly larger. The largest families, including groupers, jacks, snappers and
emperors all of which are carnivores, were grouped in the right lower quadrant of