568
Y. Sadovy de Mitcheson and P.L. Colin
species of groupers (Serranidae) and croakers (Sciaenidae), both families for which
International Union for Conservation of Nature (IUCN) Red Listing has now been
conducted for all species, something that should set off alarm bells with conservationists and fi shery managers worldwide ( www.iucnredlist.org ; Craig et al. 2011 ).
Although many papers have been published on spawning aggregations, vexing
and fundamental questions remain, among them: (1) why spawn in an aggregation,
(2) how do spawning aggregations originally form where and when they do, (3) from
how big a geographic, i.e. catchment, area do adults come to the spawning site,
(4) how far do the offspring disperse from the aggregation site and (5) what
determines the number of individuals gathering at different sites? There are serious
fi sheries and economic issues that could draw immediate benefi t from the answers
to these and other (see below) questions that would facilitate management and
strengthen the case and urgent need for long-term preservation.
Despite the large number of reef-associated species (>100 Appendix) known to
aggregate to spawn, an appreciation of the wider implications of the aggregating
habit for coastal fi sheries and the marine ecosystem, beyond their immediate biological role in reproduction, has been slow in materializing. The phylogenetic diversity, different aggregation types, high numbers (from hundreds to tens of thousands)
of fi sh that briefl y assemble at certain sites, as well as sometimes extensive (ten to
several hundred kilometres) migrations collectively involve huge biomass movements of different trophic levels across broad expanses of reef. Initially described in
a fi sheries context in the 1800s by Vilaro Diaz ( 1884 ) , serious scientifi c study of an
aggregation was not conducted until the 1960s (Randall and Randall 1963 ) , on a parrotfi sh species. The fi rst descriptive studies of aggregations of a large commercial
species, the Nassau grouper, Epinephelus striatus , were undertaken in the 1970s
(Smith 1972 ; Olsen and LaPlace 1979 ) . The widespread occurrence of fi sh spawning aggregations became apparent in the late 1970s and 1980s, with publications
covering single geographic regions (e.g. Johannes 1981 ) . The threats of fi shing to
aggregations was fi rst recognised for the Nassau grouper (Sadovy 1993 ) , while the
ecosystem role of aggregations was considered more recently with recognition of
the apparent food value of eggs produced by massive snapper aggregations during
whale shark migrations (Heyman et al. 2001 ) .
As long-term indicators of ecological stability, spawning aggregations are perhaps
the most defi nitive iconic event available to marine scientists and managers. For some
specifi c locations there are records of aggregations stretching back 40–50 years,
with anecdotal and oral accounts from fi shing communities for much longer periods.
Since many aggregations involve large exploited reef fi shes and have been extirpated or greatly reduced by exploitation (Sadovy et al. 2008 ) , this fact alone should
have set off alarm bells throughout the management community several decades
ago. While there is a growing realization that aggregations matter, and, in many
cases are critical to maintenance or recovery of fi sheries resources, we could fi nd
few fi shery management success stories and few aggregations yet effectively
incorporated into marine protected areas (MPAs).
A compelling observation that strongly highlights the need for action is that, where
aggregating species are found and exploited, and especially in the case of transient
Y. Sadovy de Mitcheson and P.L. Colin
species of groupers (Serranidae) and croakers (Sciaenidae), both families for which
International Union for Conservation of Nature (IUCN) Red Listing has now been
conducted for all species, something that should set off alarm bells with conservationists and fi shery managers worldwide ( www.iucnredlist.org ; Craig et al. 2011 ).
Although many papers have been published on spawning aggregations, vexing
and fundamental questions remain, among them: (1) why spawn in an aggregation,
(2) how do spawning aggregations originally form where and when they do, (3) from
how big a geographic, i.e. catchment, area do adults come to the spawning site,
(4) how far do the offspring disperse from the aggregation site and (5) what
determines the number of individuals gathering at different sites? There are serious
fi sheries and economic issues that could draw immediate benefi t from the answers
to these and other (see below) questions that would facilitate management and
strengthen the case and urgent need for long-term preservation.
Despite the large number of reef-associated species (>100 Appendix) known to
aggregate to spawn, an appreciation of the wider implications of the aggregating
habit for coastal fi sheries and the marine ecosystem, beyond their immediate biological role in reproduction, has been slow in materializing. The phylogenetic diversity, different aggregation types, high numbers (from hundreds to tens of thousands)
of fi sh that briefl y assemble at certain sites, as well as sometimes extensive (ten to
several hundred kilometres) migrations collectively involve huge biomass movements of different trophic levels across broad expanses of reef. Initially described in
a fi sheries context in the 1800s by Vilaro Diaz ( 1884 ) , serious scientifi c study of an
aggregation was not conducted until the 1960s (Randall and Randall 1963 ) , on a parrotfi sh species. The fi rst descriptive studies of aggregations of a large commercial
species, the Nassau grouper, Epinephelus striatus , were undertaken in the 1970s
(Smith 1972 ; Olsen and LaPlace 1979 ) . The widespread occurrence of fi sh spawning aggregations became apparent in the late 1970s and 1980s, with publications
covering single geographic regions (e.g. Johannes 1981 ) . The threats of fi shing to
aggregations was fi rst recognised for the Nassau grouper (Sadovy 1993 ) , while the
ecosystem role of aggregations was considered more recently with recognition of
the apparent food value of eggs produced by massive snapper aggregations during
whale shark migrations (Heyman et al. 2001 ) .
As long-term indicators of ecological stability, spawning aggregations are perhaps
the most defi nitive iconic event available to marine scientists and managers. For some
specifi c locations there are records of aggregations stretching back 40–50 years,
with anecdotal and oral accounts from fi shing communities for much longer periods.
Since many aggregations involve large exploited reef fi shes and have been extirpated or greatly reduced by exploitation (Sadovy et al. 2008 ) , this fact alone should
have set off alarm bells throughout the management community several decades
ago. While there is a growing realization that aggregations matter, and, in many
cases are critical to maintenance or recovery of fi sheries resources, we could fi nd
few fi shery management success stories and few aggregations yet effectively
incorporated into marine protected areas (MPAs).
A compelling observation that strongly highlights the need for action is that, where
aggregating species are found and exploited, and especially in the case of transient