Freshwater snail and shrimp differentially affect water turbidity and benthic primary producers

Benthic macroinvertebrates play key roles in shallow aquatic ecosystems and can contribute substantially to aquatic food webs.However,how macroinvertebrates with different behaviors(for example,pertaining to locomotion,foraging and burrowing)impact water quality and primary producers has not been fully explored.Here,we performed two consecutive microcosm experiments to test the effects of(1)macroinvertebrates with different behaviors(a low mobility scraper aquatic snail Bellamya aeruginosa and a high mobility shredder freshwater shrimp Macrobrachium nipponense)and(2)different shrimp biomasses on water clarity and the composition of benthic primary producers.The results showed that presence of snails significantly increased the biomass of filamentous green algae and decreased the biomass of periphyton.In contrast,presence of shrimp significantly decreased the biomass of filamentous green algae and increased the biomass of periphyton,and these effects were biomass dependent.Filamentous green algae disappeared when shrimp biomass reached 9.8 g m^(-2).No interactive effects of snail and shrimp presence were found.This could be attributed to different food preferences by the two consumers,with snails preferring periphyton(mainly diatoms)and shrimp preferring filamentous green algae.The presence of snails decreased water turbidity,while shrimp increased water turbidity,which showed a hump-shaped response to shrimp biomass with a peak at 24.2 g m^(-2).These results are likely because the snail is a low mobility grazer and can filter suspended particles,while the shrimp is a high mobility shredder with burrows,which can strongly disturb sediment.The decrease in water disturbance at high shrimp biomass might be due to food limitation,thus reducing burrowing and foraging activities.Neither snail nor shrimp affected the biomass of H.verticillata,while the biomass of V.spinulosa increased with shrimp biomass.The reason for this could be that shrimp increased nutrient availability and decreased the growth of filamentous green algae that compete with macrophytes.Our study demonstrated that different macroinvertebrates have complementary functions in benthic habitats;thus,maintaining macroinvertebrate diversity is important for shallow aquatic ecosystems.Furthermore,the freshwater shrimp M.nipponense could be a potential consumer to control filamentous green algal blooms in its native range,but their biomass should be taken into consideration.

Improved genome assembly of Chinese sucker(Myxocyprinus asiaticus)provides insights into the identification and characterization of pharyngeal teeth related maker genes in Cyprinoidei

The Chinese sucker,Myxocyprinus asiaticus(M.asiaticus,Catostomidae,Cypriniformes),is the only living species of Catostomidae in Asia.There are more than 75 species of this family in North America.The fossil record of this group dates back to the early Eocene.As the Chinese sucker is located at the base of the Cyprinoidei phylogeny,this species is also important in clarifying the evolutionary relationships within Cyprinoidei.Here,we assembled a high-quality genome of the Chinese sucker,contig N50(40.26 Mb),which is nearly ten times longer than the previous version(4.19 Mb).Phylogenetic analysis identified that Chinese sucker together with Cyprinidae groups are paraphyletic with respect to Cobitoidea.The specific whole genome duplication event of the Chinese sucker was estimated to have occurred~25.9 million years ago.Analysis of population historical changes indicated a trend of reduction for the Chinese sucker and T.tibetana.Since Dlx genes play a key role in Cypriniformes pharyngeal teeth development,we conducted a genome-wide identification of Dlx genes,and found that these genes were doubled in whole genome duplication events,followed by the loss of specific copies.Transcriptome results showed that the expression levels of these paralogous genes were similar.This genomic resource provides useful information for the protection of Chinese sucker and functional study of Dlx genes.

Effects of environmentally relevant concentrations of micro(nano)plastics on aquatic microorganisms:Changes in potential function but not in overall composition

Micro(nano)plastics(MNPs)are a growing problem as persistent environmental pollutants.Here,we investigated the impact of MNPs on microorganisms in aquatic microbial floc exposed to NPs(80 nm)and MPs(8μm)for 35 days.Water quality indicators were tested weekly and microbiological analyses were conducted on Day 7 and 28 after exposure.The results showed that there were significant differences in the levels of total ammonia nitrogen or nitrite between the MNPs groups and the control group,spanning from Day 7 to Day 28.For the microbial response,microbial community richness in the NPs and MPs groups were significantly increased at Day 7.Functional prediction showed that the relative abundances of bacteria associated with the“Forms Biofilms”,“Potentially Pathogenic”,“Plastic Degradation”and nitrogen cycle processes were significantly different after MNPs exposure.The results suggest that MNPs had no significant effect on the microbial diversity of mature microbial flocs.Findings suggest MPs could cause an increase in the relative abundance of potentially pathogenic bacteria,while NPs do not.In addition,stress associated with MNPs affected the nitrogen cycle of microorganisms,and NPs exerted greater impacts than MPs.Findings from this study further our understanding of the impact of MNPs at environmentally relevant concentrations on microorganisms in aquatic ecosystems.

Diet variability of snappers(Teleostei:Lutjanidae)in a bay-to-reef ecosystem of the Mexican Caribbean

Fishes use environmental resources differently.Snapper ontogenic movements among coastal habitats lead to diverse diets.We investigated the diets of seven snapper species(Lutjanus apodus,L.analis,L.griseus,L.jocu,L.mahogoni,L.synagris,and Ocyurus chrysurus)in three interconnected coastal environments in the western Caribbean:Río Huach channel,Chetumal/Corozal bay,and the adjacent Xcalak reef lagoon.These three encompass all habitats used by the seven species in the study area.Snapper diets were mostly composed of fish and crustaceans,but dominance of either group varied among the studied habitats;for example,fish were the main prey for L.apodus from the reef lagoon zone,but second in the bay.Snappers are piscivorous-invertivorous mesopredators;the species that relied the most on fishes were L.griseus and L.jocu,whereas O.chrysurus preferred crustaceans.Stomach content results revealed a high degree of dietary overlap among species.Our findings suggested a tradeoff in relative weight between fish and crustaceans as the main food source of snappers at these connected areas,supporting the hypothesis of niche segregation.Our results can be used as a baseline to further our understanding of the ecology and differences in resource use by snapper species in an area undergoing important anthropogenic changes.

A review of potential conservation and fisheries benefits of breaching four dams in the Lower Snake River(Washington,USA)

Abundances of important and imperiled fishes of the Snake River Basin continue to decline.We assessed the rationale for breaching the four lower Snake River Basin dams to prevent complete loss of these fishes,and to maximize their likelihood of recovery.We summarize the science surrounding Sockeye Salmon(Oncorhynchus nerka),Chinook Salmon(O.tshawytscha),steelhead(O.mykiss),Bull Trout(Salvelinus confluentus),White Sturgeon(Acipenser transmontanus),and Pacific Lamprey(Entosphenus tridentatus).From this,we drew ten conclusions:(1)development of the Columbia River System(including the Snake River Basin)has converted mainstem rivers into reservoirs,altering fish behavior and survival;(2)most populations currently record their lowest abundance;(3)the Columbia River System dams reduce productivity of diadromous fishes in the highest-quality spawning grounds that could buffer against future climate dynamics;(4)past actions have done little to reduce impacts or precipitate recovery;(5)the Columbia River System constrains survival and productivity of salmon,steelhead and Bull Trout;(6)Snake River Basin salmon and steelhead remain at high extinction risk;(7)eliminating migration impediments and improving mainstem habitats are essential for maintaining genetic diversity and improving Bull Trout persistence;(8)the lower Snake River Basin dams preclude passage of adult White Sturgeon,constraining gene flow and recruitment;(9)the lower Snake River Basin dams impede dramatically passage of adult and juvenile Pacific Lamprey,and(10)Snake River Basin Pacific Lamprey is at high risk of extirpation.Breaching the four lower Snake River Basin dams is an action likely to prevent extirpation and extinction of these fishes.Lessons from the Columbia River System can inform conservation in other impounded rivers.

Bio-ecological remediation of freshwater aquaculture environments:A systematic review and bibliometric analysis

Freshwater aquaculture plays an important role in the global aquaculture industry.The success of freshwater aquaculture relies on the integration of bio-ecological remediation technologies to ensure its sustainable development.This paper systematically reviews the global literatures on bio-ecological remediation of freshwater aquaculture environments from 1990 to 2021,and discusses in detail the research progress and status quo in this field using both bibliometric analysis and content analysis.Our results indicate that the number of publications per year has increased year by year,with a particularly rapid increase after 2015.Institutions and researchers from China and the USA publish the greatest number of papers and contribute the most to this field.By analyzing the research progress in this field,we also find that the protection and restoration of freshwater aquaculture environments has received attention since as early as 1990,such as the application of constructed wetlands and recirculating aquaculture systems.Recently,researchers have increasingly focused on the use of microbial communities in remediation.Furthermore,vanRijn,J's papers are of great value to the research in this field.In content analysis,the application of primary technologies,including plant selection,aquatic animals,microorganisms,and biological filtration and purification equipment,as well as ecological engineering technologies with combinations of various types of organisms,is described to improve the effectiveness and efficiency of remediation.The performance,advantages,disadvantages,or limitations and prospects of these technology applications are analyzed in detail.By comparison,ecological engineering is shown to be the best remediation technology,being most comprehensive,and well-established.Taken together,this paper composes and summarizes existing work in this field,and provides guidance for future research on the improvement of existing technologies and the development of new technologies,with the aim of enhancing remediation capability,improving ecological sustainability and ensuring economic viability.

Lipidome and proteome analyses provide insights into Mariana Trench Snailfish(Pseudoliparis swirei)adaptation to the hadal zone

The hadal zone environment,characterized by extreme hydrostatic pressure,low temperatures,and limited food availability,presents substantial survival challenges for deep-sea fish species.In this study,we captured five deepsea fish species(Bathysaurus mollis,Coryphaenoides rudis,Ilyophis sp.,I.brunneus and Pseudoliparis swirei)from the Mariana Trench at depths ranging from 2027 to 7125 m,by employing China's“Exploration I and Exploration II”.By combining lipidomic and proteomic analyses,we aimed to explore the genetic basis of adaptive evolution to the hadal zone in fish.The results indicate several key findings:(1)P.swirei(Mariana hadal snailfish,MHS)may enhance energy storage and utilization during prolonged fasting periods by significantly increasing liver tissue levels of cholesterol ester(CE),ether-linked triacylglycerol(TG-O),coenzyme Q(CoQ),and ATPase content;(2)MHS could maintain membrane fluidity under high pressure by increasing the proportion of unsaturated fatty acids while reducing levels of cholesterol and phosphatidylethanolamine(PE)content.(3)The regulation of lipid types and ratios could increase the risk of lipid peroxidation.To counter oxidative stress,MHS likely elevates monounsaturated fatty acid content and enhances antioxidants such as transferrin and heat shock proteins.Overall,this study provides new insights into the adaptive mechanisms of MHS to deep-sea conditions through the lipidome and proteome analyses,thus broadening our understanding of its resilience in the hadal zone.

Tropical and subtropical streams:A synthesis

Tropical and sub-tropical streams harbor great biodiversity and are responsible for crucial ecosystem services.Intending to contribute to the understanding of how anthropogenic stressors and pressures alter functional or taxonomic diversity in biotic assemblages or processes in these systems,Water Biology and Security published eight papers.The research originated from Cameroon(Central Africa),southeastern Brazil,eastern Amazonia,and eastern China,representing eight river basins:Huai,Sui and Yishusi from east Asia;São Francisco,Doce,Jequitinhonha,and Amazon from South America;and Congo from Africa.The last two are the most biodiverse on the planet.The studied biomes included tropical rainforest and savanna,neotropical savanna and rainforest,neotropical savanna mountains,and subtropical monsoon forest.The response variables included fish assemblages(3 papers),entire macroinvertebrate assemblages or sub-groups(4 papers),and stream physical habitat structure(1 paper).

Methodology for fish biodiversity monitoring with environmental DNA metabarcoding:The primers,databases and bioinformatic pipelines

Environmental DNA(eDNA)originates from cellular material shed by organisms into aquatic or terrestrial environments and can be sampled and monitored using metabarcoding technology,which is revolutionizing fish biodiversity monitoring.Several reviews concerning fish eDNA have focused on standard sampling methods and its applications,though a systematic review focused on marker genes,databases,and bioinformatic pipelines has not yet been published.Here,we present a comprehensive literature review of studies applying metabarcoding technology to fish eDNA for the purpose of fish biodiversity monitoring.We systematically provide the available universal primers used to amplify barcoding sequences from fish eDNA,and then discuss reference barcoding databases,relevant bioinformatic analyses,as well as developed pipelines.The performances of universal primers and their relevant reference databases are summarized.Combined use of multiple primer pairs targeted for more than one gene marker(e.g.,12S,16S,Cytb,COI),and use of both local and public databases are recommended as approaches to improve the sensitivity and reliability of fish eDNA analyses.We also compare the effectiveness of eDNA metabarcoding to traditional approaches for monitoring fish biodiversity and highlight challenges and future perspectives associated with this new tool.Ultimately,we advocate for greater incorporation of eDNA analysis into fish biodiversity assessments to assist environmental managers.

Similarities and differences in gastrointestinal microbiomes between wild and human-cared spotted dolphins(Stenella attenuata)in natural waters

Despite the growing awareness on the importance of gut microbiomes,understanding marine mammal gut microbiomes remains limited due to difficulties in sampling.Spotted dolphins(Stenella attenuata)are widely spread oceanic cetaceans,and there is a gap in knowledge regarding their gut microbiology.In this study,we opportunistically collected samples from both wild and human-cared spotted dolphins in the southern waters of Hainan Island,China.This provided the opportunity to examine the composition and diversity of the gut microbial communities of this cetacean species.Since these dolphins inhabit a similar water environment,different food sources might be the primary factor distinguishing the gut microbiomes of wild and human-cared populations,offering valuable experimental material to investigate potential differences in gut microbial community structure among marine mammals in similar environments but with varying food sources.We found that the gastrointestinal microbial community structure of wild and human-cared dolphins demonstrated significant differences,both overall and at specific locations.However,no significant difference was observed in the microbial diversity of their gastrointestinal tracts,indicating that the disparities primarily lie in microbiota composition.Additionally,we detected numerous potentially pathogenic bacteria,suggesting a comprehensive future study of marine mammal gut microbiology.Such a study might involve determining health indicator factors associated with these microbiomes.Our study not only supplements information on the gut microbiology of spotted dolphins but also delves into the similarities and differences in gastrointestinal microbial communities within the same marine mammal species when food source variations play a significant role in their lives.

Towards a low-carbon footprint:Current status and prospects for aquaculture

Aquaculture is one of the fastest-growing agricultural sectors globally and is becoming increasingly important for producing sustainable and healthy diets with relatively low climate impacts.In comparison to livestock production,especially beef,seafood production has lower carbon emissions.Additionally,some species can extract carbon from aquatic environments,contributing to an extended carbon cycle.However,the potential for negative environmental consequences in aquaculture production might increase with the growing global population and demand for aquatic food.Herein,we review the environmental consequences of aquaculture production and the potential effects of different aquatic products on greenhouse gas(GHG)emissions.We also summarize approaches to improving environmental footprints for mitigating global climate change.Key elements,including improving feed efficiency,selecting suitable farmed species,and implementing sustainable farming practices and management in aquaculture,are discussed,as well as the trade-offs between aquaculture and capture fisheries.Crucially,performance gaps among farmed species underscore the potential for consumer-oriented advice to significantly reduce the effects of aquaculture on climate change.However,uncertainties and knowledge gaps related to carbon sequestration and GHG emissions in aquaculture ponds necessitate further research.Overall,holistic evaluation and strategic intervention regarding GHG emissions are fundamental and essential for achieving a sustainable,low-carbon future for aquaculture.

Characteristics of microbial communities and antibiotic resistance genes in typical rivers of the western Qinghai Lake basin

Environmental factors and anthropogenic activity are key factors that shape the distribution of bacteria and antibiotic resistance genes(ARGs)in natural environments.However,few studies have focused on the occurrence of bacteria and ARGs in remote and pristine environments.In this study,the distribution of bacteria and ARGs in two typical rivers of the western Qinghai Lake basin was investigated.Results showed that cold-resistant Planomicrobium sp.was the predominant genus due to the low temperature,followed by unclassified_f_Planococcaceae.High nitrogen nutrients increased the abundance and diversity of the bacteria community and denitrification was the dominant means of bacterial nitrate reduction.Tetracycline resistance genes including tetA,tetB,and tetC were the dominant ARGs in the western Qinghai Lake basin,ranging from 2.30×10^(3)to 1.91×10^(8)copies/L,while the low abundances of intI1,and ARGs such as sul1 indicated low anthropogenic activity in the western Qinghai Lake basin.Finally,the strong positive correlation between ARGs and intI1 highlights the potential transmission risk of ARGs through cross-or co-selection by horizontal gene transfer.Our study emphasized the adaptation of bacteria to the environment and the facilitation of anthropogenic activity in the propagation of ARGs in natural environments.

Interactive effects of warming and eutrophication on zooplankton could reverse the stoichiometric mismatch with phytoplankton

The core ecosystem functioning(e.g.trophic transfer efficiency)is at risk of being disrupted by the growing mismatch between nutrient content of primary producers and nutrient demand of grazing consumers.Ecological stoichiometry provides a conceptual framework that explains this trophic interaction using C,N and P elemental composition across trophic levels.In light of ongoing climate change and eutrophication,previous studies have raised concerns regarding the growing stoichiometric mismatch between phytoplankton and zooplankton,given the stoichiometric plasticity of phytoplankton.However,there is currently little conclusive evidence on the stoichiometric mismatch from a dual perspective of phytoplankton and zooplankton.To address this,we conducted a mesocosm experiment to investigate the separate and combined effects of climate warming(a constant increase of t3.5C plus heat waves)and eutrophication(nutrient addition)on stoichiometric mismatch between phytoplankton and zooplankton by examining stoichiometric changes in both communities.We observed a growing trend in stoichiometric mismatches when warming or nutrient addition acted individually,which was mediated by the increase in nutrient demand(N,P elements)of zooplankton growth.However,when these stressors acted jointly,the mismatches were reversed.This could be because climate warming and eutrophication combined would lead to changes in species composition,which accordingly reshaped the stoichiometric composition at the community level.These results illustrate the need of stoichiometric mismatches for understanding the implication of global change on trophic interactions and ecosystem functioning,requiring consideration not only of cross-trophic levels but also of compositional changes within communities.

Initial discovery of microplastic pollution in Mnemiopsis leidyi(Ctenophora:Lobata)

The production of plastics has exponentially increased over time such that the observation of microplastics in the oceans has become a major concern given how frequently these particles and marine biota may interact.Microplastics can be ingested by diverse species,including invertebrates,which can lead to physical damage due to their small size and potentially chemical damage related to the ingestion of monomers,polymeric additives,or adsorbed chemicals.This study reports on the first evidence of microplastics in Mnemiopsis leidyi.Microplastics were described by type,quantified,and had their chemical composition identified.In total,328 samples of microplastic(MP)candidates were observed:blue fibers were the most abundant,followed by black,red,and green fibers as well as blue fragments.Three types of microplastics were chemically identified as polyurethane,unplasticized polyvinylchloride,and polyethylene polylauryllactam.Overall,this study demonstrated that Mnemiopsis leidyi have the capacity to incorporate microplastics.Although more studies are needed,Mnemiopsis leidyi is relatively abundant on the Atlantic coast and should be recommended for use as a bioindicator for microplastics.

Assessing physical habitat structure and biological condition in eastern Amazonia stream sites

The advance of agricultural frontiers and industrialization in Amazonia has increased natural resource deterioration,resulting in degraded physical habitat structure and reduced local aquatic biodiversity.We evaluated the relative sensitivities of the Biological Monitoring Working Party(BMWP)and Average Score Per Taxon(ASPT)biotic indexes based on EPT(Ephemeroptera,Plecoptera,Trichoptera)versus EPT taxa richness,EPT abundance,and Shannon-Wiener EPT diversity for evaluating anthropogenic impacts on Amazonian streams.We expected that EPT-BMWP and EPT-ASPT would be more sensitive in detecting environmental changes on stream biota than the other measures.We sampled 32 stream sites in eastern Amazonia distributed along an environmental gradient resulting from different land use intensities.All the biological metrics except EPT-ASPT were significantly responsive to anthropogenic pressures;however,EPT taxa richness was slightly more responsive.

Novel insights into the spatial genetic patterns of the finless porpoise from East to Southeast Asia

Several cetacean species are endemically distributed throughout the Indo-Pacific.Due to disproportionate sampling and research efforts across the Indo-Pacific region,the spatial genetic structure of these species remains poorly understood.This has led to poor phylogeographic knowledge and ambiguous taxonomic classification of many Indo-Pacific cetacean species.Of these,the finless porpoise(genus Neophocaena)is a small cetacean obligatory to the inshore waters from East Asia to the Persian Gulf of the Indian Ocean.To date,two species are generally recognized:the narrow-ridged finless porpoise inhabiting temperate and subtropical waters,and wideridged finless porpoises inhabiting subtropical and tropical waters.Early research efforts focused on the temperate waters off the northern China.However,recent studies have proposed that the primary divergence within the genus may lie between the Indian Ocean and Pacific region,which remains to be tested with more samples from tropical and subtropical regions.Here,we examined the genetic relationship among the finless porpoises from the Gulf of Thailand to the Taiwan Strait using both mitochondrial and autosomal markers.Bayesian assignment analysis suggested a minimum of four genetic populations within the study areas,corresponding to the narrowridged finless porpoise from the Taiwan Strait(TWSn),and the three wide-ridged finless porpoise populations from the Taiwan Strait(TWSw),Pearl River Delta region(PRDw),and the Gulf of Thailand(Thaiw),respectively.The minimum spanning network of the mtDNA control region found shared haplotypes among finless porpoises in Chinese waters,but those from the Gulf of Thailand formed a unique matriline lineage.Consistently,the genetic differentiation or divergence within the South China Sea(Thaiw vs.PRDw)appears to be higher than that of most finless porpoise populations examined to date,and meets the threshold values of species or sub-species level proposed for the cetacean species.The Mantel test detected a strong correlation between the geographic and genetic matrices within the South China Sea(r>0.99,p<0.001),indicating that the divergence associated with isolation-by-distance(IBD)has been accumulating in recent history.Our results imply that the formation and maintenance of the spatial genetic pattern of the finless porpoise is more complex than previously thought.However,this cannot be addressed by the current taxonomic classification of the genus.

On the presence of the giant freshwater prawn,Macrobrachium rosenbergii,in French Guiana confirmed by citizen science and genetic analyses

We report for the first time the presence of self-sustaining populations of Macrobrachium rosenbergii in French Guiana.Genetic analyses of the cytochrome c oxidase subunit I marker(COI)confirmed the identity of the species as well as historical records about the introduction of the species from commercial stocks.Despite the limited presence of Macrobrachium rosenbergii in French Guiana,the species is recorded in several river basins,including two where the species has never been farmed.This suggests that the species is able to disperse locally and highlights its potential invasive nature in the territory.

Diversity of carbon cycle-linked phyllosphere microorganisms: A key driver of CO_(2) flux in macrophyte-dominated aquatic systems

Planktonic microorganisms have been recognized as important components in biogeochemical cycling in lakes.However,research into the impact of phyllosphere microorganisms,particularly those involved in carbon cycling,on CO_(2) fluxes in macrophyte-dominated lakes within the context of global environmental changes remains scarce.Here,by employing high-throughput sequencing techniques,we experimentally tested how nutrient enrichment,top-down effects of fish and increases in dissolved organic carbon(DOC)affect CO_(2) exchange flux at the water-air interface by altering the community structure and functioning of phyllosphere bacteria on macrophytes.We found that our mesocosm ecosystems exhibited a net absorption of CO_(2),but nutrient enrichment significantly decreased the absorption ability.Mantel tests and multiple regression modeling also showed that eutrophication-associated parameters(total nitrogen,total phosphorus and ammonium nitrogen),pH,and extinction coefficient were the key drivers influencing abundance of phyllosphere functional microorganisms.In addition,these experimental treatments significantly altered the composition,diversity and co-occurrence networks of carbon cyclingassociated phyllosphere microorganisms,which impacted the CO_(2) flux.Structural equation models and linear regression further showed that the Shannon Index of phyllosphere functional microorganisms related to carbon cycling(rather than plant volume inhabited-PVI)had a significant positive impact on CO_(2) fixation.This means that environmental changes—especially eutrophication—may hinder carbon sequestration by decreasing the diversity of phyllosphere microorganisms rather than reducing the abundance of submerged macrophytes.This study increases our understanding of carbon cycling processes in aquatic environments from a management perspective by emphasizing the importance of protecting the diversity of phyllosphere microorganisms in macrophyte-dominated lakes.

Water transfer determines the regional spread dynamics of non-native fish species

Interbasin water transfer projects(IBWT's)have emerged as dispersal corridors for aquatic species.However,little is known about how water transfer affects regional spread dynamics,or shapes the genetic diversity patterns of non-native populations.Shimofuri Goby Tridentiger bifasciatus is a globally introduced fish species with many wellestablished populations in IBWT's.Here,we used nuclear microsatellites to assess the genetic diversity and population structure of the Shimofuri Goby in its native and introduced sites belonging to two IBWT's in China.Our objectives were to(1)reveal the genetic diversity patterns of the Shimofuri Goby during regional spread,and(2)identify its mode of spreading in water transfer systems.We observed(1)a high level of genetic diversity in non-native populations without evidence of bottleneck effects,(2)that non-native populations with a longer water transfer times had a higher private allele richness,and(3)that non-native populations showed a highly mixed genetic structure,low level of genetic differentiation,and no significant relationship between geographical and genetic distances.Our results indicate that the genetic patterns of diversity of non-native populations are mainly shaped by a linear cascade spread processes due to long-distance movement of larvae,and are probably related to propagule pressure caused by the construction of water transfer.To manage the non-native populations of T.bifasciatus,preventive actions and physical removal should be implemented in IBWT's.