As one of the most diverse and productive ecosystems known, and one of the first ecosystems to exhibit major climate-warming impacts (coral bleaching), coral reefs have drawn much scientific attention to what may prove to be their Achilles heel, the thermal sensitivity of reef-building corals. Here we show that climate change-driven loss of live coral, and ultimately structural complexity, in the Seychelles results in local extinctions, substantial reductions in species richness, reduced taxonomic distinctness, and a loss of species within key functional groups of reef fish. The importance of deteriorating physical structure to these patterns demonstrates the longer-term impacts of bleaching on reefs and raises questions over the potential for recovery. We suggest that isolated reef systems may be more susceptible to climate change, despite escaping many of the stressors impacting continental reefs.biodiversity ͉ climate change ͉ coral bleaching ͉ resilience ͉ reef fish G lobal warming is causing reef corals around the world to expel their photosynthetic symbionts, resulting in ''bleaching'' and extensive coral mortality (1-3). Widespread impacts of bleaching are predicted (4), although empirical data on the long-term effects on other components of the ecosystem are lacking. Of particular interest are reef fish, which support local fisheries and tourism (5), and are crucial for the resilience of coral reefs (6-8). Existing studies of the indirect effects of bleaching mediated coral mortality on reef fish assemblages have been short-term and indicated limited change (9-11); however, the longer-term implications of coral loss may be much more substantial (12). Long-term responses may result from changes in the physiological condition of species following coral loss (13) or through processes such as the breakdown of the physical matrix of the remaining reef structure.The global mass bleaching event of 1998 was devastating in the western Indian Ocean, where the El Niño event interacted with the Indian Ocean dipole (14), resulting in 75-99% loss of live coral (15). The Seychelles suffered particularly badly; live coral was reduced by Ͼ90% across the entire range of the inner islands (2, 16), with no apparent depth refuge. With widely accepted predictions of all reef regions of the world suffering similar large-scale degradation through bleaching in coming decades (1, 2), the study of such locations provides a unique opportunity to understand longer-term impacts on other components of the ecosystem, with implications for resilience and the persistence of vulnerable species.We surveyed coral and fish communities at 21 sites across the inner islands of the Seychelles in 1994 (17) and 2005. Over 50,000 m 2 of three distinct coral reef habitats were surveyed: fringing reefs with carbonate framework, coral growth on a granitic substrate, and patch reefs on a sand, rock, or rubble base (17). The study specifically aimed to assess changes in benthic variables after the 1998 bleaching event and relate these to changes in the ...

The increased frequency and intensity of bleaching episodes has led to wide-scale loss of reef corals and raised concerns over the effectiveness of existing conservation and management efforts. The 1998 bleaching event was most severe in the western Indian Ocean where coral declined by up to 90% in some locations. Using fisheries independent data, we assess the long-term impacts of this event in the Seychelles on fishery target species, the overall size structure of the fish assemblage and assess the effectiveness of two marine protected areas (MPAs) in offering resilience. Fishery target species above size at first capture showed little change in biomass between 1994 and 2005, corroborating studies that suggest fisheries yields are currently not affected. Biomass remained higher in protected areas, indicating they are still effective in protecting fish stocks. However, the size structure of the fish communities, as described with size-spectra, changed in both fished and protected areas, with a decline in smaller fish (<30 cm) and an increase in larger fish (>45 cm). This is likely to represent a time lag response; with the larger fish that are lost to natural mortality and fishing no longer being replaced by juveniles. This effect is expected to be even greater in terms of productivity, affect fisheries and, as congruent patterns are observed for herbivores, suggests no long term resilience in the MPAs.Corallivores and planktivores demonstrate striking declines in numerical abundance which are greatest in MPAs, and associated with a similar pattern of decline in their preferred corals. There is an urgent need for climate mediated disturbance to be at the fore of conservation and management planning for coral reefs, which should include MPAs placed in areas of resistance and resilience to bleaching, and a greater emphasis on reducing other stressors to the system as a whole.3

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State indicators, e.g., mean size and trophic level of the fish assemblage, can provide important insights into the effects of fishing on ecosystems and the resource potential of the fishery. On coral reefs, few studies have examined the relative effects of fishing and other drivers, such as habitat, on these indicators. In light of habitat heterogeneity and increasing habitat degradation, this lack of understanding limits the usefulness of indicators for monitoring the effect of fishery management actions. Identifying thresholds or nonlinearities in relationships between fishing pressure and state indicators has been suggested as a basis for biomass‐based targets to support management efforts in low research capacity contexts. Using data collected in Seychelles, we examined the relative influences of fishable biomass (proxy for fishing pressure) and the benthic habitat on fisheries‐independent indicators characterizing attributes of the fish community important for fisheries production. We characterized the driver–indicator relationships, and compared local‐scale relationships for Seychelles with large‐scale relationships published for the Indian Ocean. We found that both habitat and fishing pressure influenced indicators, but habitat effects were particularly strong. This knowledge provides managers with the capacity to implement a diverse array of complementary management actions targeting these drivers. A number of the Seychelles scale driver–indicator relationships were linear, suggesting gradual changes in indicators in response to changes to drivers. This contrasted with relationships published for the Indian Ocean, which were characterized by thresholds below which exploitation is likely to have significant detrimental effects on the functioning of important ecosystem processes. These scale‐specific differences are likely driven by the narrower range of fishing pressures found in Seychelles. Importantly, it indicates that, although biomass‐based targets derived from large‐scale relationships may provide a useful starting point for setting management targets, the local context must be considered.

The protection of grouper spawning aggregations is a global conservation issue: populations of many grouper species are threatened with collapse due to exploitation of this critical life history behaviour by fisheries. Effective protection of spawning aggregations requires information on spawning site fidelity, residence time and timing of arrivals at, and departures from, the site. To estimate these parameters at a spawning aggregation site at Farquhar Atoll, southern Seychelles, 12 brown-marbled groupers Epinephelus fuscoguttatus and 20 camouflage groupers E. poly phe ka dion were tagged with acoustic transmitters, and their presence and absence was monitored by an array of acoustic receivers positioned at the site over 2 spawning seasons (2010/2011 and 2011/2012). Spawning aggregations formed during 3 consecutive spawning months each season and overlapped spatially and temporally in the 2 species. Intra-and inter-season site fidelity was high, with 91.7% of tagged E. fuscoguttatus and 89.5% of tagged E. polyphekadion detected at the site 1 yr after tagging. The majority (2010/2011: 82.4%, 2011/2012: 80.0%) of fish detected in a spawning season visited the site during at least 2 spawning months. Residence time at the fish spawning aggregation site was influenced by sex (E. fuscoguttatus only) and spawning month (both species). Distinct periodicity in lunar timing of arrivals and departures was observed in both species. This study highlights the spatio-temporal scales involved during spawning aggregations of 2 long-lived, slow-growing coral reef fishes, which need to be considered for their effective management.KEY WORDS: Spawning aggregation dynamics · Lunar and diel periodicity · Residence time · Site fidelity · Groupers · Epinephelus · Seychelles Resale or republication not permitted without written consent of the publisherEndang Species Res 22: 145-157, 2013 tions (FSAs) comprising several hundred to several thousand individuals (Rhodes & Sadovy 2002b, Pet et al. 2005, Nemeth 2012. These FSAs are often spatially and temporally predictable (Rhodes & Sadovy 2002b, Nemeth et al. 2007, Robinson et al. 2008 and at many locations, fisheries have developed to specifically target them (Olsen & LaPlace 1979, Sala et al. 2001, Sadovy de Mitcheson & Erisman 2012. Targeted fishing of FSAs has led to demographic changes (Beets & Friedlander 1999, stock decline (AguilarPerera 2006) and, in extreme cases, the disappearance or effective re productive failure of aggregating populations (Johannes et al. 1999, Mangubhai et al. 2011.Camouflage grouper Epinephelus polyphekadion and brown-marbled grouper E. fuscoguttatus are 2 species that form spawning aggregations. Both species are economically important and are targeted by coral reef fisheries throughout the Indo-Pacific (Pears 2012, Rhodes 2012. Similar to other tropical groupers, E. fuscoguttatus and E. polyphekadion are slowgrowing, late-maturing and occur at low densities throughout much of their range (Russell et al. 2006, Pears 2012, except when they form ...