Widespread and strong impacts of river fragmentation by human barriers on fishes in the Mekong River Basin

Research Square (Research Square), Journal Year: 2025, Volume and Issue: unknown

Published: March 5, 2025

The Mekong River, a global freshwater biodiversity hotspot, has suffered from intensive barrier construction, resulting in major challenges safeguarding its fauna. Here, we provide comprehensive evaluation of the impacts river barriers on distribution 1,032 fish species Basin. Our analysis revealed that 93% suffer habitat fragmentation, and with larger range requirements experienced higher fragmentation impacts. Sub-basins along main channel Lower had high values richness but relatively Across all migration types, potamodromous worst status (Fragmentation Index, 42.56 [95% CI, 36.95–46.05]), followed by catadromous fish. Among IUCN conservation categories, Critically Endangered highest index (33.34 [12.53–46.40]). small dams sluice gates contribute more to than large dams.

Language: Английский

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Response of Montane Fish Biodiversity to Landscape and Anthropogenic Activity Under Potential Water Quality Pathways

Ecology and Evolution, Journal Year: 2025, Volume and Issue: 15(4)

Published: April 1, 2025

ABSTRACT Mountain river ecosystems, globally recognized biodiversity hotspots shaped by pronounced landscape heterogeneity, are facing intensifying anthropogenic pressures. However, interactions between and activity on montane fish remain poorly quantified. Taking the Yuan River (Yunnan, China) as a model system, environmental DNA (eDNA) partial least squares structural equation modeling (PLS‐SEM) were coupled to disentangle responses of facets (taxonomic, functional genetic diversity) elevation human footprint gradients. First, eDNA‐derived taxonomic composition ( R = 0.97 against catch data) demonstrated Cypriniformes Perciformes dominance. Second, downstream areas exhibited enhanced 0.32) diversity 0.49), contrasting with upstream maxima −0.47). Third, gradients exerted stronger direct effects than or metrics, independent spatial autocorrelation. Crucially, PLS‐SEM identified water quality (i.e., total phosphorus (TP), nitrogen (TN), biochemical oxygen demand (BOD 5 ), organic carbon (TOC)) pivotal mediator linking outcomes. Overall, present study establishes mechanistic framework for disentangling drivers change, offering scalable reference conservation prioritization in freshwater ecosystems.

Language: Английский

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Spatiotemporal Dynamics of Fish Density in a Deep-Water Reservoir: Hydroacoustic Assessment of Aggregation Patterns and Key Drivers

Animals, Journal Year: 2025, Volume and Issue: 15(7), P. 1068 - 1068

Published: April 7, 2025

Understanding spatiotemporal patterns of fish density and their environmental drivers is critical for managing river-lake ecosystems, yet dynamic interactions in heterogeneous habitats remain poorly quantified. This study combined hydroacoustic surveys, spatial autocorrelation analysis (Moran's I), generalized additive models (GAMs) to investigate seasonal distribution, aggregation characteristics, regulatory mechanisms China's Zhelin Reservoir. The results reveal pronounced fluctuations, with summer peaking at 13.70 ± 0.91 ind./1000 m3 declining 1.95 0.13 winter. Spatial heterogeneity was evident, the Xiuhe region sustaining highest (15.69 1.09 m3) persistent hotspots upstream bays. Transient high-density clusters (90-99% confidence) near Dam during suggested thermal or hydrodynamic disturbances. GAM (R2adj = 0.712, 78.5% deviance explained) identified transitions (12.26% variance), water depth (16.54%), conductivity (13.75%), dissolved oxygen (13.29%) as dominant drivers, nonlinear responses bimodal conductivity/oxygen. These findings demonstrate that hydrological seasonality habitat jointly govern aggregation, underscoring ecological priority bays core habitats. provides a mechanistic framework guiding reservoir management, including targeted conservation, dam operation adjustments mitigate impacts, integrated strategies balancing needs similar ecosystems.

Language: Английский

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Geodiversity as a surrogate to inform freshwater fish diversity conservation and management

Journal of Applied Ecology, Journal Year: 2025, Volume and Issue: unknown

Published: April 17, 2025

Abstract Geodiversity offers novel insights into biodiversity patterns and their underlying mechanisms, thereby contributing to the development of conservation strategies amid widespread environmental changes human disturbances. However, relationship between geodiversity remains largely unexplored, particularly in freshwater ecosystems. Here, we investigated extent which accounts for fish diversity across dimensions (taxonomic, functional phylogenetic) levels (alpha beta) Lancang‐Mekong River. We first compiled three datasets (i.e. occurrence records, traits phylogenetic relations) seven geofeature group discharge, waterbody, topography, terrestrial cover, landform, soil rock) catchment. Multidimensional were then calculated at alpha beta levels, respectively. Next, assessed influence on multidimensional corresponding using generalized linear mixed models (GLMMs) structural equation modelings (SEMs). showed contrasting with showing positive upriver‐downriver gradients, but negative gradients along river continuum. The spatial congruence was weak geofeatures levels. substantially accounted variance both conditional R 2 GLMMs ranging from 0.892 0.996. increase primarily driven by growing variability discharge waterbody types, while mainly influenced rising dissimilarity types. SEMs revealed that indirect effects generally weak. Synthesis applications . Our findings emphasize profound large rivers, revealing its central role shaping through enhancing heterogeneity resource availability. To sustain diversity, it is crucial maintain types preserve linkages among components. Integrating programmes provides a robust framework ensuring ecosystem resilience functionality guiding management restoration globally, face rapid changes.

Language: Английский

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Species richness, composition, distribution and conservation status of herpetofauna in a global hotspot: The Mountains of Southwest China

Global Ecology and Conservation, Journal Year: 2024, Volume and Issue: 54, P. e03122 - e03122

Published: July 30, 2024

Herpetofauna have attracted considerable global attention due to their high risk of extinction. The Mountains Southwest China are among the 36 biodiversity hotspots and irreplaceability, Shaluli core area this region. However, diversity conservation status herpetofauna in remain unclear. In study, we updated species richness composition information based on extensive field expeditions, published literature, museum specimens. addition, identified local key environmental factors limiting distribution using niche models (ENMs). Furthermore, evaluated via Red List Index gap analysis. Our results revealed a total 68 species, representing 30 amphibians (21 genera nine families) 38 reptiles (19 six families). amphibian showed hump-shaped pattern along elevational gradient, while reptile monotonically decreasing pattern. dry-hot river valley was as hotspot, differed. Moreover, regional indices for were 0.87 0.8, respectively, showing that overall threat level region low. there large gaps protection species. study indicated new protected areas should be established existing upgraded protect with gap.

Language: Английский

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Human activities strengthen the influence of deterministic processes in the mechanisms of fish community assembly in tropical rivers of Yunnan, China

Journal of Environmental Management, Journal Year: 2024, Volume and Issue: 368, P. 122131 - 122131

Published: Aug. 8, 2024

Human-induced global alterations have worsened the severe decrease in fish biodiversity rivers. To successfully reduce pace of reduction diversity, it is crucial to prioritize understanding how human activities impact processes that shape and maintain diversity. Traditional survey methods are based on catch collection morphological identification, which often time-consuming ineffective. Hence, these inadequate for conducting thorough detailed large-scale surveys ecology. The rapid progress molecular biology techniques has transformed environmental DNA (eDNA) technique into a highly promising method studying In this work, we conducted first systematic study diversity its formation maintenance mechanism Xishuangbanna section Lancang River using eDNA metabarcoding. metabarcoding detected total 159 species freshwater fishes spanning 13 orders, 34 families, 99 genera. order cypriniformes were shown be overwhelmingly dominant. At different intensities anthropogenic activity, found differences community composition assembly. analysis Sloan's neutral model fitting revealed stochastic dominant factor shaping communities River. We further confirmed result by phylogenetic normalized stochasticity ratio. Furthermore, our findings indicate as get more intense, influence decreases, while deterministic eventually becomes prominent. Finally, discovered salinity positively correlated with changes high-intensity sample sites, but all factors had little effect low-intensity moderate-intensity sites. Our not only validated potential application monitoring tropical rivers, also respond activities. This knowledge will serve solid foundation protection resources

Language: Английский

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Phenotypic and Transcriptomic Analysis Revealed a Lack of Risk Perception by Native Tadpoles Toward Novel Non‐Native Fish

Ecology and Evolution, Journal Year: 2024, Volume and Issue: 14(10)

Published: Oct. 1, 2024

ABSTRACT The introduction of alien species poses a serious threat to native biodiversity, and mountain lake systems in the southwest China are particularly vulnerable non‐native fish. prey naivety hypothesis states that may not be able recognize novel introduced due lack common evolutionary background therefore become easy targets, so impacts fish on endemic amphibians need urgently assessed. In an ex‐situ experiment, we exposed tadpoles Chaochiao Brown Frog ( Rana chaochiaoensis ), western China, kairomones both translocated species, their phenotypic genetic response patterns were compared. results revealed significant plasticity responses total length (TOL), tail (TL), muscle width (TW) induced by kairomone, while kairomone exhibited weaker changes. At transcriptional level, number differently expressed genes (DEGs) treatment was 3.1‐fold (liver) 52.6‐fold (tail muscle) higher than treatment, respectively. There more unique DEGs primarily enriched terms pathways related stress response, energy metabolism, development. study risk perception toward fish, providing new evidence for from molecular perspectives. Future conservation efforts should prioritize assessing alpine subalpine threatened narrowly distributed amphibians. Additionally, prevention, early warning, monitoring, removal carried out as soon possible.

Language: Английский

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Freshwater non-native species' population dynamics are synchronized with functionally similar natives

Research Square (Research Square), Journal Year: 2024, Volume and Issue: unknown

Published: Dec. 4, 2024

Invasive non-native fish species can profoundly disrupt ecosystems. In invasion ecology, using the functional similarity with native to help predict demographic rates of and infer ecological processes underlying it remains largely unexplored. Utilizing a comprehensive analysis 2,903 pairs across 153 sampling sites in rivers distributed different continents, we evaluated interspecific synchrony patterns among populations (response variable) explored their relationship phylogenetic dissimilarities linear mixed model. Our results indicate that exhibit higher share similar morphological traits. This finding corroborates our hypothesis co-occurring are more functionally synchronized highlights importance environmental filtering significantly shaping population dynamics between communities coexisting species. Compensatory was not important explaining coexistence We highlight potential widespread increasing synchronous consequently decreasing community stability. addition, life history distances could observed. By elucidating which type (ecological, history, morphological, phylogenetic) mechanisms facilitate species, this research underscores implications long term guide conservation efforts. Understanding these at level temporal is essential for preserving biodiversity face ongoing changes.

Language: Английский

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Spawning cohort trade‐offs of reproductive time and output in cyprinid fish along an elevation gradient

Ecology Of Freshwater Fish, Journal Year: 2023, Volume and Issue: 33(2)

Published: Dec. 7, 2023

Abstract Understanding environmental requirements for fish reproduction in natural habitats is crucial population conservation and restoration. However, such information extremely scarce the highly threatened schizothoracine fishes that cover large elevation ranges on Tibetan Plateau. This research investigated spawning time, output conditions of wild Schizopygopsis thermalis along an elevational gradient (i.e., from 1766 to 4372 m) upper Nu‐Salween River. It found grounds S. were mainly located at elevations between 3600 m, mostly consist still marginal areas (still water <10 cm deep) with gravel substrates. Otolith microstructure analysis revealed, first spawns two seasons winter: December next February, spring: April May), winter period generally longer than spring period. Winter started earlier ended higher elevations, while occurred lower but simultaneously elevations. As increases, reproductive also cohorts shift winter‐dominant spring‐dominant. associated temperatures discharges cohort, both showed elevation‐related preferences. Our results suggest can adapt strategies conditions, which fill gaps characteristics fishes, highlight importance conserving high Qinghai‐Tibetan rivers.

Language: Английский

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