251
8 Fishery and Biological Implications of Fishing Spawning Aggregations…
are more threatened, regardless of other characteristics, all else being equal. In a
global analysis of more than 14,000 species that used a similar fuzzy logic approach,
seamount aggregating fi shes were shown to have a higher intrinsic vulnerability to
fi shing in comparison with other groups of commercially exploited marine fi shes,
due to a suite of life history characteristics such as long lifespan, late sexual
maturation, slow growth, and low natural mortality (Morato et al. 2004 ) .
8.3.1.2 Approach Two – Single Fishery, Multiple Species That Vary
in Duration and Predictability of Aggregations
An unusually detailed and long-term fi shery database from Cuba for six commercially important aggregating snappers (cubera snapper, Lutjanus cyanopterus, mutton
snapper, L. analis, grey snapper, L.griseus, lane snapper, L. synagris, yellowtail
snapper, Ocyurus chrysurus , and the Nassau grouper) was examined for speciesspecifi c trends (Claro et al. 2009 ) . The species are reported to all share similar coastal
water habitats, be part of the same multi-species fi shery, have all been exposed to
similar social, economic and management factors over a 45-year period, and evidently
show different intensity of aggregation behaviour in relation to reproduction.
They are also among the larger and longest-lived species in the fi shery. In all six species, more than 50% of annual landings were taken during the spawning season, and
all declined over time. Although cause and effect cannot be established, aggregation
predictability and targeted fi shing were likely major factors in declines, because the
most marked declines occurred among those species that exhibit the briefest (fewest
months) and most highly predictable (fi sh highly concentrated at relatively few sites)
aggregations (Fig. 8.7 ). Marked declines were also observed in mullets, which are
often targeted on or moving to spawning aggregations in Cuba. Other groups of
fi shes (jacks-Carangidae, mojarras-Gerreidae, and grunts-Haemulidae), not knowingly targeted in association with aggregations, involved in the same multi-species
fi shery have evidently not undergone similar declines (Claro et al. 2009 ) .
8.3.1.3 Approach Three – Spawning Aggregations Within a Single Taxon
This approach compares trends within three very different taxonomic groups, groupers, sea breams and croakers, each taxon with both aggregating and non-aggregating
species. The groupers (Family Epinephelidae, subfamily Epinephelinae) were
recently assessed for conservation status according to IUCN Red List categories and
criteria; threatened (T), near threatened (NT), least concern (LC) and data defi cient
(DD). The rich sea bream assemblage of South Africa has a relatively well documented fi shery history, while many large croakers are fi shed on their aggregations
with declines noted in some.
A comparative analysis of 163 groupers indicates that, among species of known
reproductive strategy, spawning aggregation formation is associated with higher
extinction risk (Fig. 8.8 ); in all cases aggregations are exploited. Since larger species
8 Fishery and Biological Implications of Fishing Spawning Aggregations…
are more threatened, regardless of other characteristics, all else being equal. In a
global analysis of more than 14,000 species that used a similar fuzzy logic approach,
seamount aggregating fi shes were shown to have a higher intrinsic vulnerability to
fi shing in comparison with other groups of commercially exploited marine fi shes,
due to a suite of life history characteristics such as long lifespan, late sexual
maturation, slow growth, and low natural mortality (Morato et al. 2004 ) .
8.3.1.2 Approach Two – Single Fishery, Multiple Species That Vary
in Duration and Predictability of Aggregations
An unusually detailed and long-term fi shery database from Cuba for six commercially important aggregating snappers (cubera snapper, Lutjanus cyanopterus, mutton
snapper, L. analis, grey snapper, L.griseus, lane snapper, L. synagris, yellowtail
snapper, Ocyurus chrysurus , and the Nassau grouper) was examined for speciesspecifi c trends (Claro et al. 2009 ) . The species are reported to all share similar coastal
water habitats, be part of the same multi-species fi shery, have all been exposed to
similar social, economic and management factors over a 45-year period, and evidently
show different intensity of aggregation behaviour in relation to reproduction.
They are also among the larger and longest-lived species in the fi shery. In all six species, more than 50% of annual landings were taken during the spawning season, and
all declined over time. Although cause and effect cannot be established, aggregation
predictability and targeted fi shing were likely major factors in declines, because the
most marked declines occurred among those species that exhibit the briefest (fewest
months) and most highly predictable (fi sh highly concentrated at relatively few sites)
aggregations (Fig. 8.7 ). Marked declines were also observed in mullets, which are
often targeted on or moving to spawning aggregations in Cuba. Other groups of
fi shes (jacks-Carangidae, mojarras-Gerreidae, and grunts-Haemulidae), not knowingly targeted in association with aggregations, involved in the same multi-species
fi shery have evidently not undergone similar declines (Claro et al. 2009 ) .
8.3.1.3 Approach Three – Spawning Aggregations Within a Single Taxon
This approach compares trends within three very different taxonomic groups, groupers, sea breams and croakers, each taxon with both aggregating and non-aggregating
species. The groupers (Family Epinephelidae, subfamily Epinephelinae) were
recently assessed for conservation status according to IUCN Red List categories and
criteria; threatened (T), near threatened (NT), least concern (LC) and data defi cient
(DD). The rich sea bream assemblage of South Africa has a relatively well documented fi shery history, while many large croakers are fi shed on their aggregations
with declines noted in some.
A comparative analysis of 163 groupers indicates that, among species of known
reproductive strategy, spawning aggregation formation is associated with higher
extinction risk (Fig. 8.8 ); in all cases aggregations are exploited. Since larger species