24
R.S. Nemeth
Pair-spawning usually occurs within spawning territories defended by individual
males whereas group-spawning occurs well above the substrate with no evidence
of territorial defense by males.
2.2 Spatial Patterns Exhibited by Fishes
That Aggregate to Spawn
During migration to spawning aggregation sites, fi sh may follow key landmarks or
bathymetric features along particular migration pathways (Colin 1992 ; Mazeroll
and Montgomery 1995, 1998 ) . Although the actual migration route might not be
direct, the straight-line distance from a fi sh’s home site to the spawning aggregation
site defi nes its migration distance . Individual fi sh or migrating groups eventually
reach a specifi c spawning aggregation site and remain in the area for a few hours,
days or weeks (Rhodes and Tupper 2008 ) . After spawning, fi sh return to home sites
along pathways that radiate outward from the spawning site. The linear distance or
length of each “radial” can vary considerably among individuals within a species
(Zeller 1998 ; Nemeth 2005 ; Nemeth et al. 2007 ) . If one connects the endpoints of
the longest “radials” which radiate out from the spawning site core (i.e. those fi sh
whose home sites are farthest from the spawning site), the resulting polygon defi nes
the catchment area of an aggregation site for a spawning population of a single
species (Fig. 2.1 ). Throughout this chapter a spawning population is defi ned as all
adults using a single spawning aggregation site.
As fi sh migrate through their catchment area and converge on the spawning site,
this temporary concentration of hundreds to thousands of herbivorous or carnivorous
fi shes during the reproductive period provides a potentially important mechanism to
interlink and possibly infl uence food webs. The complex biological processes and
trophic interactions that may occur during migration and spawning and the mosaic
of habitats through which fi sh may migrate within a catchment area represents the
functional migration area (FMA) of a species (Nemeth 2009 ) . The FMA includes
migration pathways, spatial and temporal habitat use during the spawning season,
all intra- and interspecifi c interactions and predator-prey dynamics that occur
within the catchment area during the spawning season from the moment the adults
depart their home ranges until the time they return. The functional migration area
also takes into account the transfer of energy resulting from feeding, defaecation
and release of propagules at the spawning site (Nemeth 2009 ) . Moreover, as transient aggregating species temporarily vacate their home reefs during the reproductive season, predation pressure on their potential prey may be temporarily
alleviated.
The FMA utilized may vary in size from a few hundred to several thousand
square kilometres depending upon species and location (Nemeth 2009 ) . Due to the
inherent patchiness of coral reefs, not all substrates within the catchment area are
suitable habitat for feeding, migration, spawning or other activities. Therefore the
subset of suitable habitats represents the maximum area supporting the spawning
population. To explore the possible infl uence of a spawning population as it moves
R.S. Nemeth
Pair-spawning usually occurs within spawning territories defended by individual
males whereas group-spawning occurs well above the substrate with no evidence
of territorial defense by males.
2.2 Spatial Patterns Exhibited by Fishes
That Aggregate to Spawn
During migration to spawning aggregation sites, fi sh may follow key landmarks or
bathymetric features along particular migration pathways (Colin 1992 ; Mazeroll
and Montgomery 1995, 1998 ) . Although the actual migration route might not be
direct, the straight-line distance from a fi sh’s home site to the spawning aggregation
site defi nes its migration distance . Individual fi sh or migrating groups eventually
reach a specifi c spawning aggregation site and remain in the area for a few hours,
days or weeks (Rhodes and Tupper 2008 ) . After spawning, fi sh return to home sites
along pathways that radiate outward from the spawning site. The linear distance or
length of each “radial” can vary considerably among individuals within a species
(Zeller 1998 ; Nemeth 2005 ; Nemeth et al. 2007 ) . If one connects the endpoints of
the longest “radials” which radiate out from the spawning site core (i.e. those fi sh
whose home sites are farthest from the spawning site), the resulting polygon defi nes
the catchment area of an aggregation site for a spawning population of a single
species (Fig. 2.1 ). Throughout this chapter a spawning population is defi ned as all
adults using a single spawning aggregation site.
As fi sh migrate through their catchment area and converge on the spawning site,
this temporary concentration of hundreds to thousands of herbivorous or carnivorous
fi shes during the reproductive period provides a potentially important mechanism to
interlink and possibly infl uence food webs. The complex biological processes and
trophic interactions that may occur during migration and spawning and the mosaic
of habitats through which fi sh may migrate within a catchment area represents the
functional migration area (FMA) of a species (Nemeth 2009 ) . The FMA includes
migration pathways, spatial and temporal habitat use during the spawning season,
all intra- and interspecifi c interactions and predator-prey dynamics that occur
within the catchment area during the spawning season from the moment the adults
depart their home ranges until the time they return. The functional migration area
also takes into account the transfer of energy resulting from feeding, defaecation
and release of propagules at the spawning site (Nemeth 2009 ) . Moreover, as transient aggregating species temporarily vacate their home reefs during the reproductive season, predation pressure on their potential prey may be temporarily
alleviated.
The FMA utilized may vary in size from a few hundred to several thousand
square kilometres depending upon species and location (Nemeth 2009 ) . Due to the
inherent patchiness of coral reefs, not all substrates within the catchment area are
suitable habitat for feeding, migration, spawning or other activities. Therefore the
subset of suitable habitats represents the maximum area supporting the spawning
population. To explore the possible infl uence of a spawning population as it moves