Similar impacts of fishing and environmental stress on calcifying organisms in Indian Ocean coral reefs

McClanahan, Timothy R.; Muthiga, Nyawira A.

doi:10.3354/meps11921

Cited by 21 publications

(12 citation statements)

References 90 publications

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“…Consequently, benthic niches normally occupied by hard corals could be affected by unfavorable climate change and warm water disturbances. If true, reef growth has and will decline with further climate disturbance and ecological change (Perry et al 2015, McClanahan & Muthiga 2016. The relationship between fish biomass and our market-based human influence variable was weak but stronger with depth, which can also act as a refuge from fishing (Tyler et al 2009).…”

Section: Environmental Habitat and Human Influencesmentioning

confidence: 97%

Managing coral reef fish community biomass is a priority for biodiversity conservation in Madagascar

McClanahan¹,

Jadot²

2017

Mar. Ecol. Prog. Ser.

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Elucidating factors that influence natural resources and diversity can assist managing species and their ecological functions. Key management options include protecting unique locations or implementing restrictions that more broadly protect ecological attributes and their services. To evaluate these 2 options, we examined 23 fish families in 152 unique sites in the Western and Northern Madagascar Ecoregion to test for spatial aggregation, environmental, habitat, and human influences on the fish communities. We found that there were 10 distinct communities of fish and that they were widely distributed in the region. Biomass and diversity were closely associated with the community types and showed weak spatial aggregation and environmental and market influences. Further, fishable biomass was only weakly positively associated with habitat characteristics of depth and soft coral cover and negatively associated with erect algae (R 2 = 0.06). Biomass was the strongest predictor of number of species whereas associations with light and hard coral cover were weak and median sea surface temperature (SST) and water depth had the weakest influences (all variable R 2 = 0.41). Given the weak spatial aggregation, environmental influences, high spatial and species variability, we suggest that there are few conservation priority locations. Consequently, for ecological representation and function there is a need for broad-scale spatial management that captures this heterogeneity and maintains reef fish biomass. The status of reefs in this ecoregion was fair with ~65% of the study sites having biomass > 600 kg ha −1 .

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Section: Environmental Habitat and Human Influencesmentioning

confidence: 97%

Managing coral reef fish community biomass is a priority for biodiversity conservation in Madagascar

McClanahan¹,

Jadot²

2017

Mar. Ecol. Prog. Ser.

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“…It is however, unlikely that these species would be effective in controlling CoTS populations across the entire Indo-Pacific region as they are not universally common [86]. However, triggerfishes (particularly, Balistapus undulatus) may nonetheless be important maintaining the structure of coral reef ecosystems, by predating on rock-boring urchins [87]. There may be other large predatory fishes capable of regulating densities of adult CoTS; Keesing and Halford [47] observed the pufferfish A. stellatus to be capable of consuming adult starfish (20 cm diameter) in less than 10 min.…”

Section: Rates Of Predation On Crown-of-thorns Starfishmentioning

confidence: 99%

Known Predators of Crown-of-Thorns Starfish (Acanthaster spp.) and Their Role in Mitigating, If Not Preventing, Population Outbreaks

et al. 2017

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Predatory release has long been considered a potential contributor to population outbreaks of crown-of-thorns starfish (CoTS; Acanthaster spp.). This has initiated extensive searches for potentially important predators that can consume large numbers of CoTS at high rates, which are also vulnerable to over-fishing or reef degradation. Herein, we review reported predators of CoTS and assess the potential for these organisms to exert significant mortality, and thereby prevent and/or moderate CoTS outbreaks. In all, 80 species of coral reef organisms (including fishes, and motile and sessile invertebrates) are reported to predate on CoTS gametes (three species), larvae (17 species), juveniles (15 species), adults (18 species) and/or opportunistically feed on injured (10 species) or moribund (42 species) individuals within reef habitats. It is clear however, that predation on early life-history stages has been understudied, and there are likely to be many more species of reef fishes and/or sessile invertebrates that readily consume CoTS gametes and/or larvae. Given the number and diversity of coral reef species that consume Acanthaster spp., most of which (e.g., Arothron pufferfishes) are not explicitly targeted by reef-based fisheries, links between overfishing and CoTS outbreaks remain equivocal. There is also no single species that appears to have a disproportionate role in regulating CoTS populations. Rather, the collective consumption of CoTS by multiple different species and at different life-history stages is likely to suppress the local abundance of CoTS, and thereby mediate the severity of outbreaks. It is possible therefore, that general degradation of reef ecosystems and corresponding declines in biodiversity and productivity, may contribute to increasing incidence or severity of outbreaks of Acanthaster spp. However, it seems unlikely that predatory release in and of itself could account for initial onset of CoTS outbreaks. In conclusion, reducing anthropogenic stressors that reduce the abundance and/or diversity of potential predatory species represents a "no regrets" management strategy, but will need to be used in conjunction with other management strategies to prevent, or reduce the occurrence, of CoTS outbreaks.

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“…Effects of reduced fish diversity, their life histories, and increased sea urchin biomass were evident. At the time of the study, fishing impacts were less than reported elsewhere in the WIO (McClanahan and Muthiga , b). Nevertheless, if this region is to provide adaptive potential to climate change, fishing at sustainable levels and maintaining reef fish biomass, life histories, and functions is a high priority.…”

Section: Discussionmentioning

confidence: 72%

“…Evidence for trophic cascade effects caused by overfishing was present but not strong. Sea urchin biomass increased as restrictions declined, but the mean maximum values of ~1600 kg/ha were generally low compared to the larger region where values >2300 kg/ha were found in >65% of WIO reefs (McClanahan and Muthiga ). Erect algae cover is usually found to be ~5% in the region, and therefore, the 15% cover found here suggests high algae and some evidence for weak competition with hard corals.…”

Section: Discussionmentioning

confidence: 81%

Environmental variability indicates a climate‐adaptive center under threat in northern Mozambique coral reefs

McClanahan

Muthiga

2017

Ecosphere

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Abstract. A priority for modern conservation is finding and managing regions with environmental and biodiversity portfolio characteristics that will promote adaptation and the persistence of species during times of rapid climate change. The latitudinal edges of high-diversity biomes are likely to provide a mixture of environmental gradients and biological diversity that meet the portfolio criteria needed for adaptive systems. Northern Mozambique and the Quirimbas Islands represent the edge of a coral reef diversity center with limited potential to expand because of geologic and oceanographic limits on the southern edges. This region does, however, have the potential to be its own discrete adaptive center if it contains climate refugia and there are environmental gradients that promote acclimatization, ecological reorganization, and natural selection. Consequently, to evaluate this potential we tested for strong regional environmental spatial heterogeneity that might indicate a climate-adaptive center. Additionally, we evaluated human influences and environmental and demographic data on finfish, coral, and sea urchins in 66 reefs across~4°of latitude to evaluate ecological changes and human threats. A number of clear gradients in environmental and human influences were observed. For example, temperature increased and became more centralized and right-skewed, while water quality decreased to the south. Coral communities susceptible to thermal stress were found in the north where dispersed temperatures indicated a location with either tolerance to or refugium from recent thermal disturbances. Nevertheless, high coral diversity was found in southern deep-water channels. Further, spatial patterns for corals and fish differed indicating complex geographicfishing-biodiversity gradients. Consequently, environmental conditions for an adaptive portfolio exist and include refugia for preserving climate-sensitive and for numbers of coral taxa. Fishing and urban threats were observable as reduced fish biomass, diversity, and body sizes but higher biomass of sea urchins. We observed that many remote and protected areas had fish biomass values lower than expected or near maximum sustainable yields. This indicates low compliance and widespread migratory fishing, which is reducing fish diversity below maximum levels. Recommendations to sustain this adaptive center are to maintain fish biomass >500 kg/ha by increasing fisheries restrictions and compliance.

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Similar impacts of fishing and environmental stress on calcifying organisms in Indian Ocean coral reefs

Cited by 21 publications

References 90 publications

Managing coral reef fish community biomass is a priority for biodiversity conservation in Madagascar

Managing coral reef fish community biomass is a priority for biodiversity conservation in Madagascar

Known Predators of Crown-of-Thorns Starfish (Acanthaster spp.) and Their Role in Mitigating, If Not Preventing, Population Outbreaks

Environmental variability indicates a climate‐adaptive center under threat in northern Mozambique coral reefs

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