•River impoundment results in fairly predictable changes in fish functional diversity.•The most vulnerable species have functional traits associated with flowing water, flow pulses, and habitat ...complexity and connectivity.•Changes in distributions of functional traits negatively affect fishery yields, market values, traditional fishing practices and ecosystem properties.•Effects are not limited to the reservoir and often extend to reaches far upstream and downstream of dams.•Functional approaches can improve our ability to predict the responses of fishes and fisheries to hydroelectric dams across multiple scales.
We summarize observed and expected impacts of hydroelectric dams on tropical fishes and fisheries through the lens of fish functional traits and consequences of shifting functional diversity for social-ecological systems. Following impoundment, stocks respond to environmental changes differently according to their functional traits, resulting in fairly predictable shifts in assemblage functional structure. The most vulnerable species are those with traits adaptive for habitats with fast flowing water, structural complexity, flood pulsing or those requiring connectivity across basins to complete their life cycle. Shifts in assemblage functional trait distributions are accompanied by reduced fishery yields and impacts to other ecosystem services. Research employing a functional traits approach should enhance assessment of impacts of impoundments on biodiversity, fisheries and ecosystem services, especially for data-deficient systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Land-cover change often shifts the distribution of biomass in animal communities. However, the effects of land-cover changes on functional diversity remain poorly understood for many organisms and ...ecosystems, particularly, for floodplains. We hypothesize that the biomass distribution of fish functional diversity in floodplains is associated with land cover, which would imply that fish traits affect behavioral and/or demographic responses to gradients of land cover. Using data from surveys of 462 habitats covering a range of land-cover conditions in the Amazon River floodplain, we fitted statistical models to explain landscape-scale variation in functional diversity and biomass of all fish species as well as subsets of species possessing different functional traits. Forest cover was positively associated with fish biomass and the strength of this relationship varied according to functional groups defined by life history, trophic, migration, and swimming-performance/microhabitat-use traits. Forty-two percent of the functional groups, including those inferred to have enhanced feeding opportunities, growth, and/or reproductive success within forested habitats, had greater biomass where forest cover was greater. Conversely, the biomass of other functional groups, including habitat generalists and those that directly exploit autochthonous food resources, did not vary significantly in relation to forest cover. The niche space occupied by local assemblages (functional richness) and dispersion in trait abundances (functional dispersion) tended to increase with forest cover. Our study supports the expectation that deforestation in the Amazon River floodplain affects not only fish biomass but also functional diversity, with some functional groups being particularly vulnerable.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The hydrological connectivity of freshwater ecosystems in the Amazon basin makes them highly sensitive to a broad range of anthropogenic activities occurring in aquatic and terrestrial systems at ...local and distant locations. Amazon freshwater ecosystems are suffering escalating impacts caused by expansions in deforestation, pollution, construction of dams and waterways, and overharvesting of animal and plant species. The natural functions of these ecosystems are changing, and their capacity to provide historically important goods and services is declining. Existing management policies—including national water resources legislation, community‐based natural resource management schemes, and the protected area network that now epitomizes the Amazon conservation paradigm—cannot adequately curb most impacts. Such management strategies are intended to conserve terrestrial ecosystems, have design and implementation deficiencies, or fail to account for the hydrologic connectivity of freshwater ecosystems. There is an urgent need to shift the Amazon conservation paradigm, broadening its current forest‐centric focus to encompass the freshwater ecosystems that are vital components of the basin. This is possible by developing a river catchment‐based conservation framework for the whole basin that protects both aquatic and terrestrial ecosystems.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
1. Habitat degradation leads to biodiversity loss and concomitant changes in ecosystem processes. Tropical river floodplains are highly threatened by land cover changes and support high biodiversity ...and important ecosystem services, but the extent to which changes in floodplain land cover affect fish biodiversity remains unknown. 2. We combined fish and environmental data collected in situ and satellite-mapped landscape features to evaluate how fish species with different ecological strategies and assemblage structures respond to deforestation in floodplains of the Amazon River. We surveyed 462 floodplain habitats distributed along a gradient of land cover, from largely forested to severely deforested. Rather than analyse only taxonomic metrics, we employed an integrative approach that simultaneously considers different aspects of fish biodiversity (i.e. β diversity and taxonomic and functional assemblage structure) to facilitate mechanistic interpretations of the influence of land cover. 3. Spatial patterns of fish biodiversity in the Amazon River floodplain were strongly associated with forest cover as well as local environmental conditions linked to landscape gradients. Several species and functional groups defined by life-history, feeding, swimming/microhabitat-use strategies were positively associated with forest cover. Other species, including some that would usually be considered habitat generalists and species directly dependent on autochthonous resources (e.g. planktivores), were most common in areas dominated by herbaceous vegetation or open water habitats associated with the opposite extreme of the forest cover gradient. β diversity and the degree of uniqueness of species combinations within habitats were also positively associated with forest cover. 4. Synthesis and applications. Our results demonstrating that spatial patterns of fish biodiversity are associated with forest cover, indicate that deforestation of floodplains of the Amazon River results in spatial homogenization of fish assemblages and reduced functional diversity at both local and regional scales. Floodplains world-wide have undergone major land cover changes, with forest loss projected to increase during the next decades. Conserving fish diversity in these ecosystems requires protecting mosaics of both aquatic habitats and floodplain vegetation, with sufficient forest cover being critically important.
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Hydropower is a threat to freshwater fishes. Despite a recent boom in dam construction, few studies have assessed their impact on mega-diverse tropical rivers. Using a before-after study design, we ...investigated the early impacts of the Belo Monte hydroelectric complex, the third-largest hydropower project in the world, on fishes of the Xingu River, a major clear-water tributary of the lower Amazon. We explored impacts across different river sectors (upstream, reservoir, reduced flow sector, and downstream) and spatial scales (individual sectors vs. all sectors combined) using joint species distribution models and different facets of diversity (taxonomic, functional, and phylogenetic). After 5 years of the Belo Monte operation, species richness declined ~12% in lentic and ~16% in lotic environments. Changes in abundance were of less magnitude (<4%). Effects were particularly negative for species of the families Serrasalmidae (mainly pacus), Anostomidae (headstanders), Auchenipteridae, and Pimelodidae (catfishes), whereas no taxonomic group consistently increased in richness or abundance. The reservoir and downstream sectors were the most impacted, with declines of ~24–29% in fish species richness, overall reductions in fish body size and trophic level, and a change in average body shape. Richness and abundance also declined in the reduced river flow, and changes in size, shape, and position of fins were observed. Relatively minor changes were found in the upstream sector. Variation in functional and phylogenetic diversity following river impoundment was subtle; however, across sectors, we found a reduction in functional divergence, indicating a decline in the abundance of species located near the extremities of community functional space. This may be the first sign of an environmental filtering process reducing functional diversity in the region. Greater changes in flow and habitats are expected as hydropower operations ramp up, and continued monitoring is warranted to understand the full scope and magnitude of ecological impacts.
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•Richness declined ~12% in lentic and ~16% in lotic habitats after dams' operation.•Reservoir (~24%) and downstream (~29%) sectors had the steepest richness declines.•Serrasalmidae, Anostomidae, Auchenipteridae and Pimelodidae were the most impacted.•Dams' impacts were related with changes in fish body size, shape, and trophic level.•Changes in functional diversity were subtle with a reduction in functional divergence.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Inland fisheries underpin food security in many tropical countries. The most productive inland fisheries in tropical and subtropical developing countries occur in large river–floodplain systems that ...are often impacted by land cover changes. However, few studies to date have assessed the effects of changes in floodplain land cover on fishery yields. Here, we integrated fisheries and satellite‐mapped habitat data to evaluate the effects of floodplain deforestation on fishery yields in 68 floodplain lake systems of the lower Amazon River, representing a wide range in relative amounts of woody, herbaceous and non‐vegetated land cover. We modelled relative fish yields (fish capture per unit effort CPUE) in the floodplain lakes as a function of the relative amounts of forest, shrub, aquatic macrophyte and bare/herbaceous habitats surrounding them. We found that forest amount was positively related (p = .0003) to multispecies CPUE. The validity of these findings was supported by rejection of plausible alternative causative mechanisms involving habitat‐related differences in amount of piscivores, fishing effort, lake area, and habitat effects on CPUE of the nine taxa dominating multispecies yields. Our results provide support to the idea that removal of floodplain forests reduces fishery yields per unit effort. Increased protection of floodplain forests is necessary to maintain the food, income and livelihood security services provided by large river–floodplain fisheries.
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DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Communities throughout the globe are increasingly being given the responsibility of resource management, making it necessary to understand the factors that lead to success in community-based ...management (CBM). Here, we assessed whether and how institutional design principles affect the ecological outcomes of CBM schemes for
Arapaima
sp., an important common-pool fishery resource of the Amazon Basin. We quantified the degree of presence of Ostrom’s (Science 325:419–422, 1990) institutional design principles in 83 communities using a systematic survey, and quantitatively linked the design principles to a measure of ecological outcome (arapaima density) in a subset of 39 communities to assess their influence. To understand regional patterns of institutional capacity for CBM, we evaluated the degree of presence of each principle in all 83 communities. The principle scores were positively related to arapaima density in the 39 CBM schemes, explaining about half of the variation. Design principles related to defined boundaries and graduated sanctions exerted the strongest influence on the capacity of CBM to increase arapaima density. The degree to which most principles were present in all 83 communities was generally low, however, with the two most influential principles (defined boundaries and graduated sanctions) being the least present of all. Although the roles of the other principles (management rules, conflict resolution, collective action, and monitoring systems) are probably important, our results indicate that efforts aimed at strengthening the presence of defined boundaries and graduated sanctions in communities hold promise to improve the effectiveness of arapaima CBM regionally.
Food webs are spatially variable and temporally dynamic in heterogeneous and species-rich river floodplains. However, empirical evidence that shows how food webs vary across landscapes and scales in ...river–floodplain ecosystems is limited, especially in the tropics. Here, we evaluate how the flow of energy and matter varies among food webs in aquatic habitats and across scales in the lower Amazon River floodplains. We surveyed 109 habitats across 19 floodplain units (lake systems) and analyzed the isotopic composition of primary production sources and fish tissues to estimate relative contributions of these sources to fish biomass at local and regional scales. Basal production sources and fish species each varied considerably in their carbon and nitrogen isotopic ratios across the floodplain landscape. Aquatic macrophytes and suspended particulate organic material in the water column were inferred to be the principal basal sources contributing to the biomass of most fish species at the regional scale. However, the estimated contribution of different production sources to fish biomass varied, on average, by ∼40% across lake systems. The sources estimated to contribute most to fish biomass at the regional scale were sometimes unimportant in certain species and lake systems. Conversely, the least important sources at the regional scale were sometimes very important at the local scale. Spatial variation in the isotopic composition of production sources and fishes, and the proportional contributions of sources to fish biomass in the Amazon River floodplain, are probably influenced by multiple factors including variation in the quality and quantity of basal sources. Future stable isotope investigations of aquatic food webs of river–floodplain systems should consider not only suitable replication and appropriate temporal scale, but also spatial scale.
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Tropical river fisheries support food security for millions of people but are increasingly threatened by hydropower development. How dams affect these fisheries remains poorly known in most regions. ...Here, we used a functional traits approach to evaluate the extent to which compositions of fishery yields in the Madeira River Basin, the largest sub‐basin in the Amazon, respond to dam construction. We also explored how dams affected the monetary value of yields and fishing‐based income of the communities.
We collected fishing data in 17 locations distributed over 300 km across upstream, reservoir and downstream zones during pre‐and post‐dam construction periods. We interviewed 711 fishers from 13 communities to assess fishing income during pre‐ and post‐dam periods.
Catch‐per‐unit effort (CPUE) declined significantly, that is, by 37%, after dam construction. Multivariate analysis yielded six species clusters according to trait syndromes related to life history, migration, swimming performance/habitat‐use and economic value that were associated with the environmental data characteristic of pre‐ and post‐dam periods. Comparison of CPUE of each cluster indicated that large species with periodic life‐history strategy and regional or long‐distance migratory behaviour were most affected by dam construction, with CPUE declining by, on average, 31%. Declines in yields and shifts in functional composition of the fishery yields resulted in average decline of 21% in the monetary value of functional clusters and 30% in fishing income.
Synthesis and applications. Our study indicates that the implementation of the dams affected the functional composition of yields and reduced catches, negatively affecting the fishing‐based income of communities in the Madeira River. These results imply that hydropower expansion will cause detrimental effects for fisheries and the livelihoods they sustain. Our results underscore the urgent need for considering alternative sources of renewable energy (e.g. solar power and in‐stream turbines) to avoid irreversible socio‐environmental damages of large dam projects. In river reaches where dams are already in operation or under construction, minimizing impacts will require improving operational protocols to reduce hydrological alterations and developing research and technology to improve the functionality of fish passages. In these locations, addressing losses in fishery value and fishing‐based income will also require the implementation of fair compensation measures. Maintaining fish production requires conserving flow pulses and free‐flowing rivers and tributaries critical for completing life cycles of fish species with vulnerable traits.
Resumo
A pesca em rios tropicais sustenta a segurança alimentar de milhões de pessoas, mas está cada vez mais ameaçada pela expansão hidrelétrica. Entretanto, em diversas regiões, os efeitos das construções das barragens na pesca ainda são pouco conhecidos. Neste estudo, utilizamos uma abordagem de análise com base em traços funcionais para identificar possíveis alterações na composição de espécies de peixes e nas capturas pesqueiras na Bacia do Rio Madeira, a maior sub‐bacia da Amazônia, em resposta à construção de barragens. Além disso, exploramos como as barragens impactaram o valor monetário da pesca e a renda dos pescadores.
Coletamos dados de pesca em 17 localidades distribuídos em mais de 300 km nas zonas montante, reservatório, e jusante das hidrelétricas, durante os períodos pré e pós‐construção das barragens. Também entrevistamos 711 pescadores de 13 comunidades para avaliar a renda pesqueira durante os períodos pré e pós‐barragem.
A captura por unidade de esforço (CPUE) diminuiu significativamente, em 37%, após a construção das hidrelétricas. Análises multivariadas apontaram seis agrupamentos (grupos) de espécies de acordo com síndromes de traços funcionais relacionados à história de vida, migração, desempenho de natação/uso de microhabitat e valor econômico. Esses grupos de espécies foram especificamente associados aos dados ambientais característicos dos períodos pré ou pós‐barramento de acordo com seus traços funcionais. Espécies que atingem maiores comprimentos, e que possuem estratégia de história de vida periódica, além de comportamento migratório (regional ou de longa distância), foram mais fortemente afetadas pela construção de barragens, mostrando declínio médio na CPUE de 31%. Declínios nas capturas pesqueiras e alterações na composição funcional da pesca resultaram em um declínio médio de 30% na renda gerada pela pesca nas comunidades estudadas.
Síntese e aplicações. Nosso estudo indica que a implantação das hidrelétricas e as consequentes mudanças nas condições ambientais reduziram as capturas e alteraram a composição funcional da pesca, afetando negativamente a renda das comunidades estudadas no Rio Madeira. Esses resultados indicam que a expansão da construção de hidrelétricas prejudica a pesca e os meios de subsistência das populações locais. Nossos resultados demonstram a necessidade urgente de considerar o uso de fontes alternativas de energia renovável (por exemplo, energia solar e turbinas posicionadas no rio (‘in‐stream’)) para evitar os danos socioambientais irreversíveis causados por grandes projetos hidrelétricos. Em trechos de rios onde as hidrelétricas já estão em funcionamento ou em construção, minimizar os impactos exigirá melhorias dos protocolos de operação para reduzir as alterações hidrológicas e o desenvolvimento de pesquisa e tecnologia para aperfeiçoar a funcionalidade das passagens para peixes. Nesses locais, medidas de compensação justas devem ser implementadas para reaver perdas no valor da pesca e na renda pesqueira das comunidades. Manter a produção pesqueira requer conservar os pulsos de inundação e conectividade dos rios e tributário os quais são essenciais para o desenvolvimento dos ciclos de vida das espécies de peixes com características vulneráveis.
Our study indicates that the implementation of the dams affected the functional composition of yields and reduced catches, negatively affecting the fishing‐based income of communities in the Madeira River. These results imply that hydropower expansion will cause detrimental effects for fisheries and the livelihoods they sustain. Our results underscore the urgent need for considering alternative sources of renewable energy (e.g. solar power and in‐stream turbines) to avoid irreversible socio‐environmental damages of large dam projects. In river reaches where dams are already in operation or under construction, minimizing impacts will require improving operational protocols to reduce hydrological alterations and developing research and technology to improve the functionality of fish passages. In these locations, addressing losses in fishery value and fishing‐based income will also require the implementation of fair compensation measures. Maintaining fish production requires conserving flow pulses and free‐flowing rivers and tributaries critical for completing life cycles of fish species with vulnerable traits.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract
Riverine floodplains are biologically diverse and productive ecosystems. Although tropical floodplains remain relatively conserved and ecologically functional compared to those at higher ...latitudes, they face accelerated hydropower development, climate change, and deforestation. Alterations to the flood pulse could act synergistically with other drivers of change to promote profound ecological state change at a large spatial scale. State change occurs when an ecosystem reaches a critical threshold or tipping point, which leads to an alternative qualitative state for the ecosystem. Visualizing an alternative state for Amazonian floodplains is not straightforward. Yet, it is critical to recognize that changes to the flood pulse could push tropical floodplain ecosystems over a tipping point with cascading adverse effects on biodiversity and ecosystem services. We characterize the Amazonian flood pulse regime, summarize evidence of flood pulse change, assess potential ecological repercussions, and provide a monitoring framework for tracking flood pulse change and detecting biotic responses.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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