48
R.S. Nemeth
2.6 Conclusions and Future Directions
Throughout tropical reef ecosystems a wide diversity of fi shes, with a range of
aggregating behaviours, migrate to specifi c spawning aggregation sites. Some species are solitary carnivores that are widely dispersed across 100’s–1,000’s km
2 and
undergo long distance spawning migrations only once per year. At the other extreme
are herbivores that live in foraging groups and migrate short distances to spawning
aggregation sites on a daily basis. Fishes that aggregate to spawn provide an important and largely overlooked ecological component of connectivity within marine
ecosystems that needs to be incorporated into fi shery management, EBM and
MPA design.
Typically, connectivity is associated with the larval phase but aggregating
species provide examples whereby adult connectivity may also be an important part
of ecosystem dynamics. Spawning migrations represent short-term yet substantial
fl uctuations in fi sh biomass that increase the potential for signifi cant trophic interactions and energy transfer from feeding grounds to spawning sites, and beyond,
through the release of eggs and predator-prey encounters. Although a large body of
anecdotal information exists on this topic, the most dramatic example of the infl uence of spawning aggregations on ecosystem-level processes is the synchronized
convergence of whale sharks in Belize and other locations apparently for the purpose
of feeding on fi sh spawn at spawning aggregation sites (Heyman et al. 2001 ;
Hoffmayer et al. 2007 ) . Multiple-species spawning aggregation sites in particular
are important cross-roads of marine animal migrations and represent major nodes of
biological diversity and reproductive potential.
The area within which species migrate represents each spawning aggregation’s
functional migration area and includes important migration pathways and habitats
used exclusively during the spawning season. Since the functional migration area
encompasses most of the relevant biological processes and habitats used by aggregating species it may also provide an appropriate guide for defi ning the relevant
geographical boundaries necessary to implement EBM objectives. Nested within
the functional migration areas are other spatially distinct components of some
aggregating species that are equally relevant to fi sheries management, including
catchment area, staging area, courtship arena and the core spawning site. Detailed
information on these spatial components is beginning to emerge for a few groupers
and snappers but is lacking for most other species. Based on limited data, the catchment area encompasses the home ranges of an aggregation’s spawning adults during
the annual reproductive season and defi nes the minimum area of management for a
particular species. The staging area may be important for aggregating groupers and
snappers immediately before and after spawning for feeding, visiting cleaning stations or for some other purpose. Staging areas that contain healthy and biologically
diverse reef systems and intact prey populations may be an important component of
reproductive success for transient aggregating species which may spend weeks or
months away from home sites, yet they might not be immediately obvious as associated with an FSA. Finally, protecting the areas used for courtship and spawning
R.S. Nemeth
2.6 Conclusions and Future Directions
Throughout tropical reef ecosystems a wide diversity of fi shes, with a range of
aggregating behaviours, migrate to specifi c spawning aggregation sites. Some species are solitary carnivores that are widely dispersed across 100’s–1,000’s km
2 and
undergo long distance spawning migrations only once per year. At the other extreme
are herbivores that live in foraging groups and migrate short distances to spawning
aggregation sites on a daily basis. Fishes that aggregate to spawn provide an important and largely overlooked ecological component of connectivity within marine
ecosystems that needs to be incorporated into fi shery management, EBM and
MPA design.
Typically, connectivity is associated with the larval phase but aggregating
species provide examples whereby adult connectivity may also be an important part
of ecosystem dynamics. Spawning migrations represent short-term yet substantial
fl uctuations in fi sh biomass that increase the potential for signifi cant trophic interactions and energy transfer from feeding grounds to spawning sites, and beyond,
through the release of eggs and predator-prey encounters. Although a large body of
anecdotal information exists on this topic, the most dramatic example of the infl uence of spawning aggregations on ecosystem-level processes is the synchronized
convergence of whale sharks in Belize and other locations apparently for the purpose
of feeding on fi sh spawn at spawning aggregation sites (Heyman et al. 2001 ;
Hoffmayer et al. 2007 ) . Multiple-species spawning aggregation sites in particular
are important cross-roads of marine animal migrations and represent major nodes of
biological diversity and reproductive potential.
The area within which species migrate represents each spawning aggregation’s
functional migration area and includes important migration pathways and habitats
used exclusively during the spawning season. Since the functional migration area
encompasses most of the relevant biological processes and habitats used by aggregating species it may also provide an appropriate guide for defi ning the relevant
geographical boundaries necessary to implement EBM objectives. Nested within
the functional migration areas are other spatially distinct components of some
aggregating species that are equally relevant to fi sheries management, including
catchment area, staging area, courtship arena and the core spawning site. Detailed
information on these spatial components is beginning to emerge for a few groupers
and snappers but is lacking for most other species. Based on limited data, the catchment area encompasses the home ranges of an aggregation’s spawning adults during
the annual reproductive season and defi nes the minimum area of management for a
particular species. The staging area may be important for aggregating groupers and
snappers immediately before and after spawning for feeding, visiting cleaning stations or for some other purpose. Staging areas that contain healthy and biologically
diverse reef systems and intact prey populations may be an important component of
reproductive success for transient aggregating species which may spend weeks or
months away from home sites, yet they might not be immediately obvious as associated with an FSA. Finally, protecting the areas used for courtship and spawning