33
2 Ecosystem Aspects of Species That Aggregate to Spawn
Nemeth et al. 2007 ; Rhodes and Tupper 2008 ; Robinson et al. 2008 ) . Gladstone
( 1994 ) noted that dominant yellowmargin triggerfi sh males occupied the core of the
aggregation whereas smaller males occupied apparently marginal spawning habitats
on the edge of the spawning area and sometimes failed to attract a mate (Fig. 2.5 ).
If preferred or suitable spawning habitat is a limited resource, then as the number
of fi sh in an aggregation increases some portion of the spawning population may
occupy marginal areas or may fi nd other suitable spawning habitat and establish
satellite or ‘secondary’ aggregation sites (Fig. 2.5 ). This may explain the presence of
one large (primary) spawning site and one or more smaller (secondary) spawning
sites reported for red hind and leopard coralgrouper (Samoilys and Squire 1994 ;
Samoilys 1997 ; Zeller 1998 ; Kadison et al. 2009 ) . Alternatively, if fi shing pressure
at a spawning aggregation site increases, satellite aggregations may be the fi rst to be
eliminated with fi sh occupying marginal spawning habitat replacing those removed
from the core spawning area. These replacements would maintain spawning fi sh
density at the core of the primary aggregation and may account for a condition known
as hyperstability where catch rates remain stable while the total spawning population
is declining (Sadovy and Domeier 2005 ; Chapter 8) . Finally, at multi-species spawning
aggregation sites some species may have spatially distinct spawning areas whereas
others can have overlapping courtship arenas and spawning sites (Fig. 2.6 ) (Colin
and Clavijo 1988 ; Sala et al. 2001 ; Rhodes and Sadovy 2002b ; Whaylen et al. 2004 ;
Nemeth et al. 2006b ; Heyman and Kjerfve 2008 ) . Competition for limited spawning
habitat may also be a factor that determines levels of inter-specifi c aggression and the
distribution patterns observed among aggregating species at multi-species spawning
sites (Rhodes and Sadovy 2002b ; Nemeth et al. 2006b ; Robinson et al. 2008 ) .
2.3 Habitat Linkages During Spawning Migrations
Resident and transient aggregating species migrate from feeding sites or home
ranges to spawning aggregation sites over various spatial and temporal scales. To
illustrate, square-tail coralgrouper adults commonly inhabit patch reefs within
lagoons, inner and outer reef slopes and fringing reefs and spawn in reef pass channels,
outer reef slopes and promontories of fringing reefs (Myers 1999 ; Sluka 2001a , b ;
Pet et al. 2005 ; Rhodes and Tupper 2008 ) . Seasonal habitat linkages for squaretail
coralgrouper can be drawn between lagoon and fringing reefs (feeding habitats) to
channels and outer reef slopes (spawning habitats). Hutchinson and Rhodes ( 2010 ) ,
who tracked squaretail coralgrouper with acoustic telemetry, provided a specifi c
example of habitat linkages between spawning and home sites. Squaretail coralgrouper aggregated near reef passages along reef fl at, wall and slope habitats and
lived the remainder of the year on either the fore reef or inside the lagoon in areas of
moderate to high coral cover. To better understand the connectivity of aggregating
species among habitat types, Nemeth ( 2009 , Appendices 4.1 and 4.2) compiled a
list of 13 generalized adult feeding habitats and spawning sites for 134 species of
coral reef fi shes known or presumed to form resident (n = 42) or transient (n = 92)
2 Ecosystem Aspects of Species That Aggregate to Spawn
Nemeth et al. 2007 ; Rhodes and Tupper 2008 ; Robinson et al. 2008 ) . Gladstone
( 1994 ) noted that dominant yellowmargin triggerfi sh males occupied the core of the
aggregation whereas smaller males occupied apparently marginal spawning habitats
on the edge of the spawning area and sometimes failed to attract a mate (Fig. 2.5 ).
If preferred or suitable spawning habitat is a limited resource, then as the number
of fi sh in an aggregation increases some portion of the spawning population may
occupy marginal areas or may fi nd other suitable spawning habitat and establish
satellite or ‘secondary’ aggregation sites (Fig. 2.5 ). This may explain the presence of
one large (primary) spawning site and one or more smaller (secondary) spawning
sites reported for red hind and leopard coralgrouper (Samoilys and Squire 1994 ;
Samoilys 1997 ; Zeller 1998 ; Kadison et al. 2009 ) . Alternatively, if fi shing pressure
at a spawning aggregation site increases, satellite aggregations may be the fi rst to be
eliminated with fi sh occupying marginal spawning habitat replacing those removed
from the core spawning area. These replacements would maintain spawning fi sh
density at the core of the primary aggregation and may account for a condition known
as hyperstability where catch rates remain stable while the total spawning population
is declining (Sadovy and Domeier 2005 ; Chapter 8) . Finally, at multi-species spawning
aggregation sites some species may have spatially distinct spawning areas whereas
others can have overlapping courtship arenas and spawning sites (Fig. 2.6 ) (Colin
and Clavijo 1988 ; Sala et al. 2001 ; Rhodes and Sadovy 2002b ; Whaylen et al. 2004 ;
Nemeth et al. 2006b ; Heyman and Kjerfve 2008 ) . Competition for limited spawning
habitat may also be a factor that determines levels of inter-specifi c aggression and the
distribution patterns observed among aggregating species at multi-species spawning
sites (Rhodes and Sadovy 2002b ; Nemeth et al. 2006b ; Robinson et al. 2008 ) .
2.3 Habitat Linkages During Spawning Migrations
Resident and transient aggregating species migrate from feeding sites or home
ranges to spawning aggregation sites over various spatial and temporal scales. To
illustrate, square-tail coralgrouper adults commonly inhabit patch reefs within
lagoons, inner and outer reef slopes and fringing reefs and spawn in reef pass channels,
outer reef slopes and promontories of fringing reefs (Myers 1999 ; Sluka 2001a , b ;
Pet et al. 2005 ; Rhodes and Tupper 2008 ) . Seasonal habitat linkages for squaretail
coralgrouper can be drawn between lagoon and fringing reefs (feeding habitats) to
channels and outer reef slopes (spawning habitats). Hutchinson and Rhodes ( 2010 ) ,
who tracked squaretail coralgrouper with acoustic telemetry, provided a specifi c
example of habitat linkages between spawning and home sites. Squaretail coralgrouper aggregated near reef passages along reef fl at, wall and slope habitats and
lived the remainder of the year on either the fore reef or inside the lagoon in areas of
moderate to high coral cover. To better understand the connectivity of aggregating
species among habitat types, Nemeth ( 2009 , Appendices 4.1 and 4.2) compiled a
list of 13 generalized adult feeding habitats and spawning sites for 134 species of
coral reef fi shes known or presumed to form resident (n = 42) or transient (n = 92)