46
R.S. Nemeth
amount of eggs eaten from individual spawning events, Moyer ( 1987 ) observed that
egg predators often remained within a gamete cloud for more than a minute and
continued to feed on the remaining eggs even though other spawning clouds of
T. cupido were released nearby. In the Caribbean, a similar suite of egg predators
was reported to feed directly on gametes or increased in numbers at spawning aggregation sites, e.g. Belize, Cayman Islands, Mexico, Puerto Rico and the US Virgin
Islands (Colin and Clavijo 1988 ; Aguilar-Perera and Aguilar-Davila 1996 ; Heyman
et al. 2001 ; Whaylen et al. 2006 ) . The majority of egg predators may opportunistically feed on newly released eggs at aggregation sites, while other species target
these temporary concentrations of planktonic food. This appears to be the case for
whale sharks which may undergo annual migrations on a regional scale to feed on
gamete clouds of snappers, jacks and mackerels (Heyman et al. 2001, 2005 ; Graham
and Castellanos 2005 ; Hoffmayer et al. 2007 ) . The importance of these temporary
food sources is unknown, but the synchronized movements of whale sharks and
possibly other planktivorous species to active spawning sites highlights a possible
ecosystem level component of spawning aggregations.
2.4.4 Other Trophic Linkages
Other potentially important but unstudied trophic interactions at spawning aggregation sites include host-parasite relationships, the use of cleaning stations by aggregating species and the effects of defaecation on benthic communities. During the
spawning season fi sh spend considerable amounts of energy for migration, courtship,
territoriality and spawning. Semmens et al. ( 2006 ) found that infestation by the isopod
parasite Excorallana tricornis tricornis on Nassau grouper increased immediately
following spawning. Similar infestations were also observed on red hind at an aggregation on St. Croix (RSN personal observation, Tom Daley personal communication).
Semmens et al. ( 2006 ) suggested that energy expense and physiological stress during
reproduction may expose Nassau grouper to higher levels of parasitism and therefore
visiting cleaning stations during spawning may be particularly important for aggregating groupers (Nemeth et al. 2006b ) . Finally, defaecation by aggregating species is a
potentially important source of nutrients into a reef system surrounding a spawning
aggregation site. Faecal material may provide nutrients that enhance the growth of
corals at aggregation sites (Meyer et al. 1983 ; Meyer and Schultz 1985 ) or may directly
contribute to local productivity through feeding by coprophagus fi shes and other detritivorous organisms (Bailey and Robertson 1982 ; Robertson 1982 ) .
2.5 Approaches to Study and Management of FSA’s
at the Ecosystem Level
Identifying and mapping the catchment areas of spawning populations and the various
ecological components within the functional migration area of aggregating species is
an important step towards ecosystem based management (EBM) of multi-species
R.S. Nemeth
amount of eggs eaten from individual spawning events, Moyer ( 1987 ) observed that
egg predators often remained within a gamete cloud for more than a minute and
continued to feed on the remaining eggs even though other spawning clouds of
T. cupido were released nearby. In the Caribbean, a similar suite of egg predators
was reported to feed directly on gametes or increased in numbers at spawning aggregation sites, e.g. Belize, Cayman Islands, Mexico, Puerto Rico and the US Virgin
Islands (Colin and Clavijo 1988 ; Aguilar-Perera and Aguilar-Davila 1996 ; Heyman
et al. 2001 ; Whaylen et al. 2006 ) . The majority of egg predators may opportunistically feed on newly released eggs at aggregation sites, while other species target
these temporary concentrations of planktonic food. This appears to be the case for
whale sharks which may undergo annual migrations on a regional scale to feed on
gamete clouds of snappers, jacks and mackerels (Heyman et al. 2001, 2005 ; Graham
and Castellanos 2005 ; Hoffmayer et al. 2007 ) . The importance of these temporary
food sources is unknown, but the synchronized movements of whale sharks and
possibly other planktivorous species to active spawning sites highlights a possible
ecosystem level component of spawning aggregations.
2.4.4 Other Trophic Linkages
Other potentially important but unstudied trophic interactions at spawning aggregation sites include host-parasite relationships, the use of cleaning stations by aggregating species and the effects of defaecation on benthic communities. During the
spawning season fi sh spend considerable amounts of energy for migration, courtship,
territoriality and spawning. Semmens et al. ( 2006 ) found that infestation by the isopod
parasite Excorallana tricornis tricornis on Nassau grouper increased immediately
following spawning. Similar infestations were also observed on red hind at an aggregation on St. Croix (RSN personal observation, Tom Daley personal communication).
Semmens et al. ( 2006 ) suggested that energy expense and physiological stress during
reproduction may expose Nassau grouper to higher levels of parasitism and therefore
visiting cleaning stations during spawning may be particularly important for aggregating groupers (Nemeth et al. 2006b ) . Finally, defaecation by aggregating species is a
potentially important source of nutrients into a reef system surrounding a spawning
aggregation site. Faecal material may provide nutrients that enhance the growth of
corals at aggregation sites (Meyer et al. 1983 ; Meyer and Schultz 1985 ) or may directly
contribute to local productivity through feeding by coprophagus fi shes and other detritivorous organisms (Bailey and Robertson 1982 ; Robertson 1982 ) .
2.5 Approaches to Study and Management of FSA’s
at the Ecosystem Level
Identifying and mapping the catchment areas of spawning populations and the various
ecological components within the functional migration area of aggregating species is
an important step towards ecosystem based management (EBM) of multi-species