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Sun J, Du W, Lucas MC, Ding C, Chen J, Tao J, He D. River fragmentation and barrier impacts on fishes have been greatly underestimated in the upper Mekong River. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 327:116817. [PMID: 36459786 DOI: 10.1016/j.jenvman.2022.116817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 11/09/2022] [Accepted: 11/14/2022] [Indexed: 06/17/2023]
Abstract
River barriers reduce river connectivity and lead to fragmentation of fish habitats, which can result in decline or even extinction of aquatic biota, including fish populations. In the Mekong basin, previous studies have mainly focused on the impacts of large dams but ignored the impacts of small-scale barriers, or drew conclusions from incomplete barrier databases, potentially leading to research biases. To test the completeness of existing databases and to evaluate the catchment-scale fragmentation level, a detailed investigation of river barriers for the whole Upper Mekong (Lancang catchment) was performed, by conducting visual interpretation of high-resolution remotely sensed images. Then, a complete catchment-scale barrier database was created for the first time. By comparing our barrier database with existing databases, this study indicates that 93.7% of river barriers were absent from the existing database, including 75% of dams and 99.5% of small barriers. Barrier density and dendritic connectivity index (DCID and DCIP) were used to measure channel fragmentation within the catchment. Overall, 50.5% of sub-catchments contained river barriers. The Middle region is the most fragmented area within the Lancang catchment, with a median [quartiles] barrier density of 5.34 [0.70-9.67] per 100 km, DCIP value of 49.50 [21.50-90.00] and DCID value of 38.50 [9.00-92.25]. Furthermore, since 2010, distribution ranges of two representative fish species Schizothorax lissolabiatus (a rheophilic cyprinid) and Bagarius yarrelli (a large catfish) have reduced by 19.2% and 32.8% respectively, probably due in part to the construction of river barriers. Our findings indicate that small-scale barriers, in particular weirs and also small dams are the main reason for habitat fragmentation in the Lancang and must be considered alongside large dams in water management and biodiversity conservation within the Mekong.
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Affiliation(s)
- Jingrui Sun
- Yunnan Key Laboratory of International Rivers and Transboundary Eco-security, Yunnan University, Kunming, 650091, China; Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China
| | - Weilong Du
- Yunnan Key Laboratory of International Rivers and Transboundary Eco-security, Yunnan University, Kunming, 650091, China; Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China
| | - Martyn C Lucas
- Department of Biosciences, University of Durham, Durham DH1 3LE, UK
| | - Chengzhi Ding
- Yunnan Key Laboratory of International Rivers and Transboundary Eco-security, Yunnan University, Kunming, 650091, China; Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China.
| | - Jinnan Chen
- Yunnan Key Laboratory of International Rivers and Transboundary Eco-security, Yunnan University, Kunming, 650091, China; Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China
| | - Juan Tao
- Yunnan Key Laboratory of International Rivers and Transboundary Eco-security, Yunnan University, Kunming, 650091, China; Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China
| | - Daming He
- Yunnan Key Laboratory of International Rivers and Transboundary Eco-security, Yunnan University, Kunming, 650091, China; Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China.
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Duong T, Nguyen NT, Tran DD, Le TH, Nor SAM. Multiple genetic lineages of anadromous migratory Mekong catfish Pangasius krempfi revealed by mtDNA control region and cytochrome b. Ecol Evol 2023; 13:e9845. [PMID: 36820247 PMCID: PMC9937891 DOI: 10.1002/ece3.9845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 02/01/2023] [Accepted: 02/03/2023] [Indexed: 02/20/2023] Open
Abstract
Population genetic structure of migratory fishes can reflect ecological and evolutionary processes. Pangasius krempfi is a critically important anadromous catfish in the Mekong River, and its migration pathways and genetic structure have attracted much interest. To investigate, we quantified the genetic diversity of this species using the control region (D-loop) and Cytochrome b (Cytb) of the mitochondrial genome. Fish were sampled (n = 91) along the Mekong tributaries from upstream to estuaries and coastal areas in the Mekong Delta and compared to three samples from Pakse (Laos). The D-loop haplotype (0.941 ± 0.014) and nucleotide diversity (0.0083 ± 0.0005) were high in all populations, but that of Cytb was low (0.331 ± 0.059 and 0.00063 ± 0.00011, respectively). No genetic difference was detected between populations, indicating strong gene flow and confirming a long migration distance for this species. Pangasius krempfi was not genetically structured according to geographical populations but was delineated into three haplogroups, suggesting multiple genetic lineages. The presence of haplogroups in each sampling location implies that migration downstream is random but parallel when the fish enter two river tributaries bifurcating from the main Mekong River. Individuals can also migrate along the coast, far from the estuaries, suggesting a longer migration path than previously reported, which is crucial for maintaining diverse genetic origin and migration pathways for P. krempfi.
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Affiliation(s)
- Thuy‐Yen Duong
- College of Aquaculture and FisheriesCan Tho UniversityCan Tho CityVietnam
| | | | - Dac Dinh Tran
- College of Aquaculture and FisheriesCan Tho UniversityCan Tho CityVietnam
| | - Thanh Hoa Le
- Immunology DepartmentInstitute of Biotechnology (IBT), Vietnam Academy of Science and Technology (VAST)Ho Chi Minh CityVietnam
- Graduate University of Science and Technology (GUST), Vietnam Academy of Science and Technology (VAST)Ho Chi Minh CityVietnam
| | - Siti Azizah Mohd Nor
- Institute of Marine BiotechnologyUniversiti Malaysia TerengganuTerengganuMalaysia
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Yu F, Liu F, Xia Z, Xu C, Wang J, Tang R, Ai Z, Zhang Y, Hou M, Zou X. Integration of ABC curve, three dimensions of alpha diversity indices, and spatial patterns of fish assemblages into the health assessment of the Chishui River basin, China. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:75057-75071. [PMID: 35648347 DOI: 10.1007/s11356-022-20648-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 05/02/2022] [Indexed: 06/15/2023]
Abstract
Index of biotic integrity (IBI) based on fish has been applied globally. However, few have considered that fish assemblages change among different aggregate ecoregions when conducted their health assessment. Indeed, some comprehensive indices, such as functional and phylogenetic diversity indices and ABC curve, can be used to identify aspects that are not captured by traditional metrics. Consequently, we try to integrate comprehensive indices and spatial patterns of fish assemblages to develop IBI systems and then verified their effectiveness and accuracy for assessing the environmental health of the Chishui River basin. The comprehensive disturbance index (CDI), based on 11 water quality parameters and 4 human land use, was set to distinguish reference sites and impaired sites. According to the spatial patterns of fish assemblages, the 40 sites were finally divided into 2 aggregate ecoregions, include wadeable streams and nonwadeable rivers. 97 candidate metrics were selected to develop our IBI systems based on the systematic screening method. The result also showed that our IBI systems performed well in discriminating anthropogenic disturbances at both aggregate ecoregions, which suggests that our systems could provide a reliable evaluation. The mean IBI score of the Chishui River basin was 72.09 ± 16.58, and was classified as good status. However, S1 (Chishuiyuan Town), Baisha River, Tongzi River, and Xishui River were disturbed by various human activities. We conclude that the spatial patterns of fish assemblages should be combined with more comprehensive indices to assess river health. On the other hand, we do believe that the process of developing and verifying our IBI systems could be regarded as a reference for biomonitoring in more mountain river systems.
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Affiliation(s)
- Fandong Yu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Fei Liu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, China
| | - Zhijun Xia
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chunsen Xu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jianwei Wang
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, China.
| | - Rui Tang
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, China
| | - Zujun Ai
- Yunnan Management and Conservation Bureau of National Nature Reserve of Rare and Endemic Fishes in the Upper Reaches of Yangtze River, Zhaotong, 657000, Yunnan, China
| | - Youzhao Zhang
- Yunnan Management and Conservation Bureau of National Nature Reserve of Rare and Endemic Fishes in the Upper Reaches of Yangtze River, Zhaotong, 657000, Yunnan, China
| | - Miaomiao Hou
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xinhua Zou
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
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Dao TS, Nguyen VT, Baduel C, Bui MH, Tran VT, Pham TL, Bui BT, Dinh KV. Toxicity of di-2-ethylhexyl phthalate and tris (2-butoxyethyl) phosphate to a tropical micro-crustacean (Ceriodaphnia cornuta) is higher in Mekong River water than in standard laboratory medium. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:39777-39789. [PMID: 35113371 DOI: 10.1007/s11356-022-18993-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 01/27/2022] [Indexed: 06/14/2023]
Abstract
Plasticizers such as di(2-ethylhexyl) phthalate (DEHP) and tris (2-butoxyethyl) phosphate (TBOEP) are manufactured chemicals produced in high volumes. These chemicals are frequently detected in the aquatic environment and cause toxic effects on organisms. In this study, we assessed the chronic impacts of DEHP and TBOEP, respectively, at the concentration of 100 µg L-1 dissolved in the artificial medium (M4/4) and Mekong River water on life history traits of a tropical micro-crustacean, Ceriodaphnia cornuta, for 14 days. DEHP and TBOEP substantially reduced the survival of C. cornuta. In M4/4 medium, both plasticizers strongly enhanced reproduction but did not influence the growth of C. cornuta. Mekong River water, plasticizers-exposed C. cornuta produced less neonates than those in the control. The detrimental impacts of DEHP and TBOEP on the fitness of C. cornuta were much stronger in natural river water than in M4/4. Our results suggest that plasticizers can cause adverse effects on tropical freshwater cladocerans, particularly in natural water. These results are of a deep concern, as national and international regulatory guidelines which are based on ecotoxicological tests using standard media may not fully capture these effects.
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Affiliation(s)
- Thanh-Son Dao
- Department of Environmental Management, Faculty of Environment and Natural Resources, Ho Chi Minh City University of Technology (HCMUT), Ho Chi Minh City, Vietnam.
- CARE, HCMUT, Vietnam National University, Ho Chi Minh City, Vietnam.
| | - Van-Tai Nguyen
- Department of Environmental Management, Faculty of Environment and Natural Resources, Ho Chi Minh City University of Technology (HCMUT), Ho Chi Minh City, Vietnam
- CARE, HCMUT, Vietnam National University, Ho Chi Minh City, Vietnam
| | - Christine Baduel
- IRD, CNRS, Grenoble INP, Institut Des Géosciences Et de L'Environnement (IGE), Université Grenoble Alpes, 38050, Grenoble, France
| | - Manh-Ha Bui
- Department of Environmental Sciences, Saigon University, Ho Chi Minh City, Vietnam
| | - Viet Tuan Tran
- Environmental Monitoring Division, Institute for Tropical Technology and Environmental Protection, Ho Chi Minh City, Vietnam
| | - Thanh-Luu Pham
- Vietnam Academy of Science and Technology (VAST), Graduate University of Science and Technology, 18 Hoang Quoc Viet Street, Cau Giay District, Hanoi, Vietnam
- Institute of Tropical Biology, Vietnam Academy of Science and Technology (VAST), 85 Tran Quoc Toan Street, District 3, Ho Chi Minh City, Vietnam
| | - Ba-Trung Bui
- Department of Environmental Toxicology, Institute for Environment and Resources, Ho Chi Minh City, Vietnam
| | - Khuong V Dinh
- Department of Fisheries Biology, Nha Trang University, Nha Trang City, Vietnam
- Department of Biosciences, University of Oslo, Blindernvn. 31, 0371, Oslo, Norway
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Changing Land Use and Population Density Are Degrading Water Quality in the Lower Mekong Basin. WATER 2021. [DOI: 10.3390/w13141948] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Establishing reference conditions in rivers is important to understand environmental change and protect ecosystem integrity. Ranked third globally for fish biodiversity, the Mekong River has the world’s largest inland fishery providing livelihoods, food security, and protein to the local population. It is therefore of paramount importance to maintain the water quality and biotic integrity of this ecosystem. We analyzed land use impacts on water quality constituents (TSS, TN, TP, DO, NO3−, NH4+, PO43−) in the Lower Mekong Basin. We then used a best-model regression approach with anthropogenic land-use as independent variables and water quality parameters as the dependent variables, to define reference conditions in the absence of human activities (corresponding to the intercept value). From 2000–2017, the population and the percentage of crop, rice, and plantation land cover increased, while there was a decrease in upland forest and flooded forest. Agriculture, urbanization, and population density were associated with decreasing water quality health in the Lower Mekong Basin. In several sites, Thailand and Laos had higher TN, NO3−, and NH4+ concentrations compared to reference conditions, while Cambodia had higher TP values than reference conditions, showing water quality degradation. TSS was higher than reference conditions in the dry season in Cambodia, but was lower than reference values in the wet season in Thailand and Laos. This study shows how deforestation from agriculture conversion and increasing urbanization pressure causes water quality decline in the Lower Mekong Basin, and provides a first characterization of reference water quality conditions for the Lower Mekong River and its tributaries.
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