30
R.S. Nemeth
join the migrating group which continues to swim toward the spawning aggregation
site (Mazeroll and Montgomery 1998 ) . These behaviours may be important for
establishing, learning about and maintaining traditional spawning aggregation sites,
as shown in the bluehead wrasse, Thalassoma bifasciatum (Warner 1988 ) , which
may persist for many decades (Colin 1996 ) .
Some species may also undertake vertical migrations during the spawning period.
Detailed acoustic data from Glover’s Reef Atoll, Belize showed that migrating
Nassau grouper used not only shallow coral reef habitat along the shelf (15–35 m) but
also deeper (range 50–255 m) outer slopes below the shelf break (Starr et al. 2007 ) ;
the entire spawning population descended within a few hours to depths greater than
50 m immediately after the second, February, spawning period each year. During
the 2 months of deep reef habitation, a limited number of Nassau grouper continued
to migrate to and from the aggregation site but all fi sh remained deeper than 50 m
(mean depth 72 m). In April all tagged fi sh ascended in synchrony within a few
hours to shallow reef areas averaging 20 m depth (Starr et al. 2007 ) . It is not clear
what these Nassau grouper were doing, but the vertical depth changes may have
been to feed on preferred prey, avoid predation or parasite infestations, enter different
water strata (i.e. cooler, deeper waters) or to release fertilized eggs in particular
ocean strata or currents which enhance larval survival or retention (Semmens et al.
2006 ; Starr et al. 2007 ; Nemeth 2009 ) . Further studies and more environmental
information are needed to understand the similarities and differences in behaviour
among sites and species.
2.2.3 Courtship Arena, Spawning Site
Many investigators have identifi ed areas immediately surrounding spawning aggregation sites where fi sh density and behaviours related to spawning increase dramatically in the days leading to spawning (Colin et al. 1987 ; Colin 1992 ; Carter and
Perrine 1994 ; Rhodes and Sadovy 2002b ; Whaylen et al. 2004, 2006 ; Heyman et al.
2005 ; Kadison et al. 2006 ; Nemeth et al. 2006b ; Robinson et al. 2008 ) . Although
little is understood about these specifi c areas, they have been given a variety of
names such as ‘boundary’ area, ‘aggregation margins’, ‘areas outside the aggregation core’, ‘outlying areas’ and ‘surrounding reef areas’ (Samoilys 1997 ; Rhodes
and Sadovy 2002b ; Nemeth et al. 2007 ; Robinson et al. 2008 ) . In an effort to standardize this terminology, the term courtship arena is suggested as a potentially useful and descriptive way of identifying and characterizing the unique behaviours,
spatio-temporal patterns of movement and reef habitats associated with spawning
aggregations.
The courtship arena (Fig. 2.3 ) may be distinguished from the staging area by
observed increases in fi sh density, courtship behaviours and colouration and/or intra/
interspecifi c interactions which are at their most intense in close proximity to the
spawning aggregation site. Several studies have observed that as fi sh move from the
courtship arena to the core spawning site colour changes and male-male aggression
R.S. Nemeth
join the migrating group which continues to swim toward the spawning aggregation
site (Mazeroll and Montgomery 1998 ) . These behaviours may be important for
establishing, learning about and maintaining traditional spawning aggregation sites,
as shown in the bluehead wrasse, Thalassoma bifasciatum (Warner 1988 ) , which
may persist for many decades (Colin 1996 ) .
Some species may also undertake vertical migrations during the spawning period.
Detailed acoustic data from Glover’s Reef Atoll, Belize showed that migrating
Nassau grouper used not only shallow coral reef habitat along the shelf (15–35 m) but
also deeper (range 50–255 m) outer slopes below the shelf break (Starr et al. 2007 ) ;
the entire spawning population descended within a few hours to depths greater than
50 m immediately after the second, February, spawning period each year. During
the 2 months of deep reef habitation, a limited number of Nassau grouper continued
to migrate to and from the aggregation site but all fi sh remained deeper than 50 m
(mean depth 72 m). In April all tagged fi sh ascended in synchrony within a few
hours to shallow reef areas averaging 20 m depth (Starr et al. 2007 ) . It is not clear
what these Nassau grouper were doing, but the vertical depth changes may have
been to feed on preferred prey, avoid predation or parasite infestations, enter different
water strata (i.e. cooler, deeper waters) or to release fertilized eggs in particular
ocean strata or currents which enhance larval survival or retention (Semmens et al.
2006 ; Starr et al. 2007 ; Nemeth 2009 ) . Further studies and more environmental
information are needed to understand the similarities and differences in behaviour
among sites and species.
2.2.3 Courtship Arena, Spawning Site
Many investigators have identifi ed areas immediately surrounding spawning aggregation sites where fi sh density and behaviours related to spawning increase dramatically in the days leading to spawning (Colin et al. 1987 ; Colin 1992 ; Carter and
Perrine 1994 ; Rhodes and Sadovy 2002b ; Whaylen et al. 2004, 2006 ; Heyman et al.
2005 ; Kadison et al. 2006 ; Nemeth et al. 2006b ; Robinson et al. 2008 ) . Although
little is understood about these specifi c areas, they have been given a variety of
names such as ‘boundary’ area, ‘aggregation margins’, ‘areas outside the aggregation core’, ‘outlying areas’ and ‘surrounding reef areas’ (Samoilys 1997 ; Rhodes
and Sadovy 2002b ; Nemeth et al. 2007 ; Robinson et al. 2008 ) . In an effort to standardize this terminology, the term courtship arena is suggested as a potentially useful and descriptive way of identifying and characterizing the unique behaviours,
spatio-temporal patterns of movement and reef habitats associated with spawning
aggregations.
The courtship arena (Fig. 2.3 ) may be distinguished from the staging area by
observed increases in fi sh density, courtship behaviours and colouration and/or intra/
interspecifi c interactions which are at their most intense in close proximity to the
spawning aggregation site. Several studies have observed that as fi sh move from the
courtship arena to the core spawning site colour changes and male-male aggression