381
11 Management of Spawning Aggregations
Minimum and maximum fi sh size limits, although diffi cult to enforce especially
in remote locations, can protect juvenile and large adult fi sh, contributing to addressing growth and recruitment overfi shing. A minimum size limit set at a size large
enough will allow a target fi sh species to spawn in at least one or more spawning
seasons before recruiting to a fi shery. A maximum size limit offers protection to
large, highly fecund fi sh to remain in the population to help replenish the fi sh stock.
However, a fi sher, whether commercial, subsistence or artisanal, is unlikely to be
willing to return an under-size fi sh to the water especially if it is a prime protein and
economic source, and/or a fellow fi sher may catch and retain that same fi sh.
Managing for upper size limits to protect large females, or males of protogynous
species, is challenging because of a general market preference for larger fi sh. Also,
non-legal species taken from deeper waters are unlikely to survive release due to
barotrauma; this is a substantial problem in many deeper water fi sheries with fi sh
size limits.
Fishing gear controls, such as limiting or prohibiting the use of SCUBA and
hookah, traps, nets, spears, night fi shing, poisons such as cyanide, and explosives
can reduce overfi shing of aggregations, among other objectives. For example, fi sh
traps have been banned in Bermuda since 1990 to prevent overfi shing of coral reef
fi shes, including aggregating species such as groupers and snappers (Luckhurst and
Ward 1996 ) . Gill and channel nets are prohibited to reduce pressure on migrations
of reef and estuarine species in Cuba (Claro et al. 2009 ) , and gill nets were prohibited
on an aggregation site in Mexico (Aguilar-Perera 2004 ) . Spear-fi shing, especially at
night with lights and using SCUBA, is now occurring in many Pacifi c countries and
is considered a major threat to inshore fi sheries (Gillett and Moy 2006 ) .
When considering input and output controls, where the aggregation component
of the fi shery for a species is small compared to the non-aggregation component,
management may be applied at the overall stock/fi shery level. However, emphasis
should be placed on minimizing the catch from aggregations as much as possible.
11.3.3 Which Management Option to Use?
Deciding the appropriate fi sheries management or conservation approach will
depend on the vulnerability of the species, how depleted its aggregations or stocks
are and the potential risk of depletion. The biology and behaviour of target species
and the type, economics and social context of the fi shery are also key considerations. Management is essential and should be prioritized if the catchability of a
species is greater during aggregation periods, and if aggregations are specifi cally
targeted or are likely to be targeted by commercial fi shing. Management measures
required to rebuild aggregations will typically involve full protection using closures
if a large component of the catch comes from aggregations.
The type of aggregation and the species involved, as well as the prevailing fi shing
pressure, will be major factors determining management choices. Transient aggregating species that form relatively few, large aggregations, as opposed to resident
11 Management of Spawning Aggregations
Minimum and maximum fi sh size limits, although diffi cult to enforce especially
in remote locations, can protect juvenile and large adult fi sh, contributing to addressing growth and recruitment overfi shing. A minimum size limit set at a size large
enough will allow a target fi sh species to spawn in at least one or more spawning
seasons before recruiting to a fi shery. A maximum size limit offers protection to
large, highly fecund fi sh to remain in the population to help replenish the fi sh stock.
However, a fi sher, whether commercial, subsistence or artisanal, is unlikely to be
willing to return an under-size fi sh to the water especially if it is a prime protein and
economic source, and/or a fellow fi sher may catch and retain that same fi sh.
Managing for upper size limits to protect large females, or males of protogynous
species, is challenging because of a general market preference for larger fi sh. Also,
non-legal species taken from deeper waters are unlikely to survive release due to
barotrauma; this is a substantial problem in many deeper water fi sheries with fi sh
size limits.
Fishing gear controls, such as limiting or prohibiting the use of SCUBA and
hookah, traps, nets, spears, night fi shing, poisons such as cyanide, and explosives
can reduce overfi shing of aggregations, among other objectives. For example, fi sh
traps have been banned in Bermuda since 1990 to prevent overfi shing of coral reef
fi shes, including aggregating species such as groupers and snappers (Luckhurst and
Ward 1996 ) . Gill and channel nets are prohibited to reduce pressure on migrations
of reef and estuarine species in Cuba (Claro et al. 2009 ) , and gill nets were prohibited
on an aggregation site in Mexico (Aguilar-Perera 2004 ) . Spear-fi shing, especially at
night with lights and using SCUBA, is now occurring in many Pacifi c countries and
is considered a major threat to inshore fi sheries (Gillett and Moy 2006 ) .
When considering input and output controls, where the aggregation component
of the fi shery for a species is small compared to the non-aggregation component,
management may be applied at the overall stock/fi shery level. However, emphasis
should be placed on minimizing the catch from aggregations as much as possible.
11.3.3 Which Management Option to Use?
Deciding the appropriate fi sheries management or conservation approach will
depend on the vulnerability of the species, how depleted its aggregations or stocks
are and the potential risk of depletion. The biology and behaviour of target species
and the type, economics and social context of the fi shery are also key considerations. Management is essential and should be prioritized if the catchability of a
species is greater during aggregation periods, and if aggregations are specifi cally
targeted or are likely to be targeted by commercial fi shing. Management measures
required to rebuild aggregations will typically involve full protection using closures
if a large component of the catch comes from aggregations.
The type of aggregation and the species involved, as well as the prevailing fi shing
pressure, will be major factors determining management choices. Transient aggregating species that form relatively few, large aggregations, as opposed to resident