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The red porgy (Pagrus pagrus) is a carnivore bottom dweller sparid, inhabiting flat sandy bottoms, rhodolith and seagrass beds of the Mediterranean Sea, the Western Atlantic (from Florida to Argentina) and the Eastern Atlantic (from Britain to Gabon). Along its native range, the red porgy is highly targeted by commercial and artisanal fisheries. In the past 40 years, the population decline of the species has been widely reported. In many locations, such as the Brazilian coast, stocks have collapsed. The central portion of the Brazilian coast harbours the largest rhodolith beds in the world and the highest levels of nektonic and benthic biodiversity. Along the rhodolith megahabitat, P. pagrus density is disproportionately higher (by 480%) than that of conspicuous benthic fishes inhabiting the same environment. Despite the ecological and economic importance of such an important species along its native range, little is known regarding its habitat use, niche availability and population responses to global warming. Here we present habitat affinities based on data sampled using baited remote stereo-video systems, and modelled niche availability and global warming populational responses. Our findings reveal that the red porgy is a species highly associated with rhodolith beds along the central portion of the Brazilian coast. The presence of a disproportional density and biomass of the red porgy, compared to other marine fish species, indicates that the species plays a key ecological role as a carnivore, mesoconsumer and prey/predator tolerant species, maintaining essential ecological functions in the habitat. In a global warming scenario, the model predicted populational niche shifts poleward and a severe niche erosion at lower latitudes as expected. Conservation initiatives (implementation of Maine Protected Areas, trawling exclusion zones, mining exclusion zones, fisheries management policies) are urgent to secure future stocks of the red porgy and also preserve the fragile rhodolith beds they inhabit.

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Marine Protected Areas (MPAs) are a widely used tool for coral reefs conservation, but massive tourism activities inside MPAs worldwide can challenge their effectiveness. This study investigated the role of different levels of protection strictness (no-entry, low and high tourism-allowed zones) set for a marine sanctuary in shaping benthic cover and reef fish community structure in the richest and largest coral reef system of the Southwestern Atlantic. Reef fish community structure and benthic cover differed between protection levels. No-entry zones showed significant higher coral coverage and biomass of piscivores and herbivores than tourism-allowed zones. Highest differences were found between no-entry and high tourism intensity zones. Despite the fact that protection from fishing by itself can ensure conservation benefits, we show here that the establishment of no-entry zones improve MPAs effectiveness.

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In tropical estuaries, wet seasons are responsible for the downstream transport of allochthonous material from the upper basin and flooded plains. Although allochthonous matter is commonly associated to nutrient and detritus input, pollutants are also transported throughout the basin or suspended from the river bottom via strong streamflow remobilization and rainfall dynamics. We assessed community and population trophic niche-based patterns using organisms' stable isotopes signatures in the wet and the dry seasons to test if estuarine trophic diversity is affected by remobilization of metal-contaminated material from a mining dam collapse that occurred in the Doce river basin, Brazil. Trophic depletion was detected community-wide and in a key consumer group (bottom-dwelling fishes) at the end of the wet season in the impacted Doce river estuary (DRE). Conversely, higher trophic diversity values were recorded in a well-preserved estuary used as control site. Stable isotopes mixing models indicated in the DRE that G. genidens, a predator fish species, presented poor-quality diet based on pollutant-tolerant tiny organisms, a finding that strongly contrasts from diet described in other, little-impacted Brazilian estuaries. Although wet seasons are expected to increase trophic, functional and taxonomic diversity in tropical estuaries, in the DRE the rainfall-driven dynamics poses a threat to the community due to the presence of ore tailings.

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The Fundão dam collapse occurred on November 2015 in Mariana city (Brazil), provoking a series of ecological impacts over the Doce river basin and its nearshore environment. However many impacts over fishery target fauna (fish and shrimp) are still unknown or underestimated due to the lack of baseline data in the region. In the present study we assessed the isotopic niches modeled from δ13C and δ15N signatures of six estuarine fish species before and after the impact to assign potential shifts at the population- and community-level. We showed isotopic niche has altered in all studied species irrespective of its trophic group and habitat use. Niche community metrics indicated a depletion of trophic diversity and basal resources of the whole community after the impact. Food web changes as we reported here can impair the energy transfer through the food chain and put at risk the sustainability of small fisheries that rely upon local resources.

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