Decadal-scale response of detritivorous surgeonfishes (family Acanthuridae) to no-take marine reserve protection and changes in benthic habitat.

No-take marine reserves (NTMR) are increasingly being implemented to mitigate the effects of fishing on coral reefs, yet determining the efficacy of NTMRs depends largely on partitioning the effects of fishing from the effect of benthic habitat. Species of coral-reef fishes typically decline in density when subjected to fishing or benthic disturbances, but this is not always the case. This study documents the long-term (8-31 years) response of six species of detritivorous surgeonfishes (family Acanthuridae) to NTMR protection and benthic habitat change at four islands (Apo, Sumilon, Mantigue, Selinog) in the central Philippines, each island with a NTMR and a monitored fished site. Despite being subject to moderate fishing pressure, these species did not increase in density with NTMR protection. However, density of these surgeonfishes had a strong negative relationship with cover of live hard coral and a strong positive relationship with cover of dead substratum (sand, rubble, hard dead substratum). These surgeonfishes typically feed over dead substrata and thus probably increase in density following large environmental disturbances that substantially reduce live hard coral cover. Here, we describe effects of environmental disturbance events (e.g., use of explosives, typhoons) that reduced live hard-coral cover and subsequent large increases (up to 25 fold) in surgeonfish densities, which then slowly (over 5-15 years) decreased in density as live hard coral recovered. Density of these functionally important surgeonfish species was influenced more by changes to benthic cover than by NTMR protection. Thus, we highlight the greater importance of bottom-up controls (i.e., benthic changes to food availability) than top-down control (i.e., fishing) on a functionally important group of coral-reef fishes.

Russ GR ，Payne CS ，Bergseth BJ ，Rizzari JR ，Abesamis RA ，Alcala AC ... -  《-》

Partitioning no-take marine reserve (NTMR) and benthic habitat effects on density of small and large-bodied tropical wrasses.

Russ GR ，Lowe JR ，Rizzari JR ，Bergseth BJ ，Alcala AC ... -  《PLoS One》

Coral cover a stronger driver of reef fish trophic biomass than fishing.

Russ GR ，Rizzari JR ，Abesamis RA ，Alcala AC ... -  《-》

Relative influence of environmental factors and fishing on coral reef fish assemblages.

Understanding whether assemblages of species respond more strongly to bottom-up (availability of trophic resources or habitats) or top-down (predation pressure) processes is important for effective management of resources and ecosystems. We determined the relative influence of environmental factors and predation by humans in shaping the density, biomass, and species richness of 4 medium-bodied (10-40 cm total length [TL]) coral reef fish groups targeted by fishers (mesopredators, planktivores, grazer and detritivores, and scrapers) and the density of 2 groups not targeted by fishers (invertivores, small fish ≤10 cm TL) in the central Philippines. Boosted regression trees were used to model the response of each fish group to 21 predictor variables: 13 habitat variables, 5 island variables, and 3 fishing variables (no-take marine reserve [NTMR] presence or absence, NTMR size, and NTMR age). Targeted and nontargeted fish groups responded most strongly to habitat variables, then island variables. Fishing (NTMR) variables generally had less influence on fish groups. Of the habitat variables, live hard coral cover, structural complexity or habitat complexity index, and depth had the greatest effects on density, biomass, and species richness of targeted fish groups and on the density of nontargeted fishes. Of the island variables, proximity to the nearest river and island elevation had the most influence on fish groups. The NTMRs affected only fishes targeted by fishers; NTMR size positively correlated with density, biomass, and species richness of targeted fishes, particularly mesopredatory, and grazing and detritivorous fishes. Importantly, NTMRs as small as 15 ha positively affected medium-bodied fishes. This finding provides reassurance for regions that have invested in small-scale community-managed NTMRs. However, management strategies that integrate sound coastal land-use practices to conserve adjacent reef fish habitat, strategic NTMR placement, and establishment of larger NTMRs will be crucial for maintaining biodiversity and fisheries.

McClure EC ，Hoey AS ，Sievers KT ，Abesamis RA ，Russ GR ... -  《-》

Expectations and Outcomes of Reserve Network Performance following Re-zoning of the Great Barrier Reef Marine Park.

Networks of no-take marine reserves (NTMRs) are widely advocated for preserving exploited fish stocks and for conserving biodiversity. We used underwater visual surveys of coral reef fish and benthic communities to quantify the short- to medium-term (5 to 30 years) ecological effects of the establishment of NTMRs within the Great Barrier Reef Marine Park (GBRMP). The density, mean length, and biomass of principal fishery species, coral trout (Plectropomus spp., Variola spp.), were consistently greater in NTMRs than on fished reefs over both the short and medium term. However, there were no clear or consistent differences in the structure of fish or benthic assemblages, non-target fish density, fish species richness, or coral cover between NTMR and fished reefs. There was no indication that the displacement and concentration of fishing effort reduced coral trout populations on fished reefs. A severe tropical cyclone impacted many survey reefs during the study, causing similar declines in coral cover and fish density on both NTMR and fished reefs. However, coral trout biomass declined only on fished reefs after the cyclone. The GBRMP is performing as expected in terms of the protection of fished stocks and biodiversity for a developed country in which fishing is not excessive and targets a narrow range of species. NTMRs cannot protect coral reefs directly from acute regional-scale disturbance but, after a strong tropical cyclone, impacted NTMR reefs supported higher biomass of key fishery-targeted species and so should provide valuable sources of larvae to enhance population recovery and long-term persistence.

Emslie MJ ，Logan M ，Williamson DH ，Ayling AM ，MacNeil MA ，Ceccarelli D ，Cheal AJ ，Evans RD ，Johns KA ，Jonker MJ ，Miller IR ，Osborne K ，Russ GR ，Sweatman HP ... -  《-》