31
2 Ecosystem Aspects of Species That Aggregate to Spawn
may intensify and culminate with spawning rushes and gamete release (Rhodes and
Sadovy 2002b ; Whaylen et al. 2004 ; Nemeth et al. 2006b, 2007 ; Robinson et al.
2008 ) . Whaylen et al. ( 2004 ) described and quantifi ed such a shift in colouration
and courtship for Nassau grouper during the crepuscular period as spawning adults
moved from the reef platform to hover off the shelf edge to commence spawning. A
similar pattern has also been observed for yellowfi n grouper in the USVI (RSN
unpublished data).
The defi nition of core spawning area depends upon the mode of reproduction of
individual species. For species that establish spawning territories and pair spawn at
aggregation sites the core area is defi ned as the area which consistently has the highest densities of aggregating individuals as reported for red hind, brown-marbled
grouper, camouflage grouper and yellowmargin triggerfish ( Pseudobalistes
flavimarginatus ) (Gladstone 1994 ; Rhodes and Sadovy 2002b ; Nemeth et al. 2007 ;
Robinson et al. 2008 ) . In large aggregations multiple core spawning sites may exist
(e.g. red hind, Kadison et al. 2009 ) . For those species that spawn in large groups
(i.e. group spawn – a spawning rush of three or more fi sh such as in Nassau grouper
and snappers) the core area is the location where the majority of spawning adults
ascend into the water column and spawn and this core area can change within the
courtship arena even within a single evening (Sala et al. 2001 ; Whaylen et al. 2004 ;
Heyman and Kjerfve 2008 ) .
Estimates of the size of courtship arenas come mainly from studies of a few
transient aggregating species (triggerfi shes-Balistidae, snappers, groupers) and is
currently lacking for species forming resident aggregations (surgeonfi shes, parrotfi shes). For transient aggregating species within snappers and groupers the courtship
arena is estimated to be <10 km
2 with spawning usually confi ned to an area <1 km
2
(Fig. 2.3 , see also Appendix 4.2 in Nemeth 2009 ) . For example, Nassau and tiger
groupers, and cubera and dog snappers ( Lutjanus cyanopterus and L. jocu ) are all
transient aggregators which typically spawn along a narrow section (50–100 m) of
the shelf edge (Colin 1992 ; Carter and Perrine 1994 ; Heyman et al. 2005 ; Nemeth
et al. 2006b ; Kadison et al. 2007 ) . Heyman et al. ( 2005 ) and Kadison et al. ( 2006 )
reported that during the week of spawning cubera snapper could be found in large,
highly mobile groups within a 4.5 km
2 area of reef (i.e. courtship arena) where they
were observed performing a variety of pre-spawning behaviours. But during spawning,
cubera snapper were confi ned to a core spawning area less than 1,000 m
2 where they
spawned in mid-water (Heyman et al. 2005 ) .
Spawning aggregation territories and habitats : For aggregating species that establish temporary spawning territories and pair-spawn, the courtship arena is estimated
to be 0.01–0.4 km
2 (Appendix 4.2 in Nemeth 2009 ) . Species known to defend territories within spawning aggregations include red hind, brown-marbled, camoufl age, tiger, and leopard coralgroupers, square-tail coralgrouper ( Plectropomus
areolatus ) and yellowmargin triggerfi sh (Shapiro et al. 1993 ; Gladstone 1994 ;
Sadovy et al. 1994a, b ; Samoilys and Squire 1994 ; Samoilys 1997 ; Zeller 1998 ;
Rhodes and Sadovy 2002a, b ; Nemeth 2005 ; Nemeth et al. 2007 ; Rhodes and Tupper
2008 ; Robinson et al. 2008 ) . For these species, some of which include benthic
spawners with a lek-like mating system (i.e. triggerfi sh, Gladstone 1994 ) , the courtship
2 Ecosystem Aspects of Species That Aggregate to Spawn
may intensify and culminate with spawning rushes and gamete release (Rhodes and
Sadovy 2002b ; Whaylen et al. 2004 ; Nemeth et al. 2006b, 2007 ; Robinson et al.
2008 ) . Whaylen et al. ( 2004 ) described and quantifi ed such a shift in colouration
and courtship for Nassau grouper during the crepuscular period as spawning adults
moved from the reef platform to hover off the shelf edge to commence spawning. A
similar pattern has also been observed for yellowfi n grouper in the USVI (RSN
unpublished data).
The defi nition of core spawning area depends upon the mode of reproduction of
individual species. For species that establish spawning territories and pair spawn at
aggregation sites the core area is defi ned as the area which consistently has the highest densities of aggregating individuals as reported for red hind, brown-marbled
grouper, camouflage grouper and yellowmargin triggerfish ( Pseudobalistes
flavimarginatus ) (Gladstone 1994 ; Rhodes and Sadovy 2002b ; Nemeth et al. 2007 ;
Robinson et al. 2008 ) . In large aggregations multiple core spawning sites may exist
(e.g. red hind, Kadison et al. 2009 ) . For those species that spawn in large groups
(i.e. group spawn – a spawning rush of three or more fi sh such as in Nassau grouper
and snappers) the core area is the location where the majority of spawning adults
ascend into the water column and spawn and this core area can change within the
courtship arena even within a single evening (Sala et al. 2001 ; Whaylen et al. 2004 ;
Heyman and Kjerfve 2008 ) .
Estimates of the size of courtship arenas come mainly from studies of a few
transient aggregating species (triggerfi shes-Balistidae, snappers, groupers) and is
currently lacking for species forming resident aggregations (surgeonfi shes, parrotfi shes). For transient aggregating species within snappers and groupers the courtship
arena is estimated to be <10 km
2 with spawning usually confi ned to an area <1 km
2
(Fig. 2.3 , see also Appendix 4.2 in Nemeth 2009 ) . For example, Nassau and tiger
groupers, and cubera and dog snappers ( Lutjanus cyanopterus and L. jocu ) are all
transient aggregators which typically spawn along a narrow section (50–100 m) of
the shelf edge (Colin 1992 ; Carter and Perrine 1994 ; Heyman et al. 2005 ; Nemeth
et al. 2006b ; Kadison et al. 2007 ) . Heyman et al. ( 2005 ) and Kadison et al. ( 2006 )
reported that during the week of spawning cubera snapper could be found in large,
highly mobile groups within a 4.5 km
2 area of reef (i.e. courtship arena) where they
were observed performing a variety of pre-spawning behaviours. But during spawning,
cubera snapper were confi ned to a core spawning area less than 1,000 m
2 where they
spawned in mid-water (Heyman et al. 2005 ) .
Spawning aggregation territories and habitats : For aggregating species that establish temporary spawning territories and pair-spawn, the courtship arena is estimated
to be 0.01–0.4 km
2 (Appendix 4.2 in Nemeth 2009 ) . Species known to defend territories within spawning aggregations include red hind, brown-marbled, camoufl age, tiger, and leopard coralgroupers, square-tail coralgrouper ( Plectropomus
areolatus ) and yellowmargin triggerfi sh (Shapiro et al. 1993 ; Gladstone 1994 ;
Sadovy et al. 1994a, b ; Samoilys and Squire 1994 ; Samoilys 1997 ; Zeller 1998 ;
Rhodes and Sadovy 2002a, b ; Nemeth 2005 ; Nemeth et al. 2007 ; Rhodes and Tupper
2008 ; Robinson et al. 2008 ) . For these species, some of which include benthic
spawners with a lek-like mating system (i.e. triggerfi sh, Gladstone 1994 ) , the courtship