42 research outputs found
Regional Fisheries Livelihoods Programme for South and Southeast Asia (RFLP) Activity 1.5 (2011): Systems and Procedures for Participatory Monitoring of Management Measures Developed, Introduced and Implemented-catch Monitoring
Coastal fisheries are very essential for supporting the livelihoods of many rural poor in the coastal areas, particularly coastal community fisheries members. They serve as sources of food, employment and income generation for many coastal families. "Coastal Community Fisheries Catch Monitoring" Project which was conducted from April to November 2011 provides some data which indicates the importance of small-scale fisheries. The project was financially supported by the Regional Fisheries Livelihoods Programme, Cambodian component (RFLP/CMB) and was activity 1.5 of the approved RFLP CMB 2011 activity work plan and budget. For this catch monitoring study, 26 small-scale subsistence fishers, including 05 women, from five community fisheries (CFi?s) in the RFLP CMB area of geographic coverage from the four coastal provinces of Cambodia were selected and following appropriate training collected specific catch data and recorded it in fisher's logbook on a daily basis for the purpose of getting a better understanding of catch per unit of effort (CEPU), the health of inshore fish stock and the contribution of aquatic products to small-scale fisher households along the coast of Cambodia. The key data items recorded included total catchweight, catch weight by species, total catch sale price, fish price of the main species and total lengths of some key species. The study involved designing logbooks, training the selected 26 fishers as data collectors on data collection methods, collecting data from all the selected fishers, designing a database and entering all the collected data into the database, checking for errors and analyzing the collected data for final reporting and preparing report
Analysis of the Cambodian bagnet ("dai") fishery data
This report summarises general and detailed features of catches from the bagnet ("dai") fishery in Cambodia between 1995 and 1999, as monitored by the MRC/DoF/DANIDA Management of the Freshwater Capture Fisheries Project (MFCFP) in Phnom Penh.Fishery data, Cambodia,
Spatial and Long-Term Temporal Changes in Water Quality Dynamics of the Tonle Sap Ecosystem
Tonle Sap lake-river floodplain ecosystem (TSE) is one of the worldâs most productive freshwater systems. Changes in hydrology, climate, population density, and land use influence water quality in this system. We investigated long term water quality dynamics (22 years) in space and time and identified potential changes in nutrient limitation based on nutrient ratios of inorganic nitrogen and phosphorus. Water quality was assessed at five sites highlighting the dynamics in wet and dry seasons. Predictors of water quality included watershed land use, climate, population, and water level. Most water quality parameters varied across TSE, except pH and nitrate that remained constant at all sites. In the last decade, there is a change in the chemical nutrient ratio suggesting that nitrogen may be the primary limiting nutrient across the system. Water quality was strongly affected by development in the watershed i.e., flooded forest loss, climatic variation, population growth, and change in water level. Seasonal variations of water quality constituents were driven by precipitation and hydrology, notably the Mekongâs distinct seasonal flood pulse
Dynamique des peuplements de poissons dans le bassin inférieur du Mékong
The Mekong seasonal flow plays a pivotal role in structuring up- and downstream aquatic communities. The thesis investigates the dynamics of spatial and temporal fish community structure in the Lower Mekong system, i.e. the Lower Mekong River and its major tributaries. Using spatial and time-series datasets and univariate as well as multivariate statistical approaches, the thesis highlights: * The importance of flow and other environmental factors in explaining spatial and temporal dynamics of fish diversity patterns and assemblage structure in the Lower Mekong system. * The effects of indiscriminate fishing in one of the world's largest tropical inland fisheries, the Tonle Sap, with the finding of, despite overall stationary catch per unit effort (CPUE), strong alterations in assemblages composition, with decreasing trends in catches of large-sized species, and increasing trends in the catches of some small-sized species. * Contrasted responses of fish assemblages to a gradient of disruption of flow seasonality and predictability due to dams in the Lower Mekong system. The results obtained through this thesis contribute to the ecological understanding of fish assemblages and to the design of applications for long-term planning, monitoring, management and conservation of fisheries in the Mekong Basin and beyond. The thesis suggests that: * Maintaining the Mekong robust and predictably seasonal flood pulse dynamics and habitat connectivity is imperative to ensure fish longitudinal and lateral dispersal ability among critical habitats for breeding, feeding and seeking refuge. * Setting appropriate regulations based on known peak fish migrations at various spatiotemporal scales would allow migratory fish species to pass through rivers, access critical habitats and complete their life cycles. Also, enforcing and operationalizing the existing formal fisheries management mechanisms effectively at local, national and regional levels as well as allocating sufficient resources to the fishery sector to combat illegal fishing practices and implementing fisheries conservation measures in critical habitats would help deal with the problem of overharvesting. * Hydropower-related pulsed flows that can mimic as far as possible the natural pulsed flows are critical to reduce downstream effects on aquatic organisms, and, thus, should be prioritized and applied as one of the measures to mitigate the impacts from existing and planned hydropower dams in the Mekong Basin.Le dĂ©bit saisonnier du MĂ©kong joue un rĂŽle central dans la structuration amont/aval des communautĂ©s aquatiques. Cette Ă©tude examine les dynamiques de la structure spatiale et temporelle des communautĂ©s de poissons dans le bassin infĂ©rieur du MĂ©kong, comprenant le MĂ©kong aval et ses principaux affluents. L'application de mĂ©thodes statistiques univariĂ©es et multivariĂ©es, sur des bases de donnĂ©es spatiales et temporelles piscicoles et environnementales, met en Ă©vidence : * Le rĂŽle prĂ©pondĂ©rant des dĂ©bits dans l'explication de la dynamique spatiale et temporelle des patrons de diversitĂ© et de structure des assemblages piscicoles dans la bassin aval du MĂ©kong. * Les effets de la pĂȘche non sĂ©lective dans l'un des plus grands systĂšmes de production halieutique tropicale au monde, le lac le TonlĂ© Sap, avec la mise en Ă©vidence d'une production globalement durable marquĂ©e nĂ©anmoins par une composition altĂ©rĂ©e des communautĂ©s de poissons. * Les rĂ©ponses des assemblages de poissons face aux fluctuations saisonniĂšres et Ă la stabilitĂ© des dĂ©bits dans les riviĂšres non rĂ©gulĂ©es et rĂ©gulĂ©es du bas MĂ©kong. Les rĂ©sultats obtenus lors de cette thĂšse contribuent Ă la connaissance du fonctionnement des peuplements piscicoles et apportent une aide Ă la conception de plans de gestion et de conservation des ressources halieutiques et des autres ressources aquatiques dans le bassin du MĂ©kong et au-delĂ . Cette Ă©tude suggĂšre que : * Le maintien de la dynamique saisonniĂšre des dĂ©bits et de la connectivitĂ© des habitats est impĂ©ratif afin d'assurer la dispersion longitudinale et latĂ©rale des poissons vers des habitats vitaux pour leur reproduction, leur alimentation et leur protection. * L'Ă©tablissement d'une rĂ©glementation appropriĂ©e basĂ©e sur la connaissance des pics migratoires de poissons aux diffĂ©rentes Ă©chelles spatio-temporelles permettrait aux poissons migrateurs de franchir les riviĂšres pour accĂ©der Ă leurs habitats nĂ©cessaires Ă l'accomplissement de leur cycle de vie. Aussi, faire respecter et opĂ©rationnaliser de façon efficace les mĂ©canismes officiels de gestion halieutique aux Ă©chelles locales, nationales et rĂ©gionales, mais aussi allouer suffisamment de moyens pour le secteur de la pĂȘche afin de lutter contre les pratiques de pĂȘche illĂ©gale et pour la mise en Ćuvre de mesures de conservation contribuerait Ă rĂ©soudre les problĂšmes de surexploitation des ressources aquatiques. * La mimique des variations naturelles des dĂ©bits par les barrages hydroĂ©lectriques devrait ĂȘtre priorisĂ©es et appliquĂ©es comme une des mesures permettant d'attĂ©nuer leurs impacts sur les peuplements aquatiques du bassin du MĂ©kong
Fish assemblages dynamic in the tropical flood-pulse system of the lower Mekong river basin
Le dĂ©bit saisonnier du MĂ©kong joue un rĂŽle central dans la structuration amont/aval des communautĂ©s aquatiques. Cette Ă©tude examine les dynamiques de la structure spatiale et temporelle des communautĂ©s de poissons dans le bassin infĂ©rieur du MĂ©kong, comprenant le MĂ©kong aval et ses principaux affluents. L'application de mĂ©thodes statistiques univariĂ©es et multivariĂ©es, sur des bases de donnĂ©es spatiales et temporelles piscicoles et environnementales, met en Ă©vidence : * Le rĂŽle prĂ©pondĂ©rant des dĂ©bits dans l'explication de la dynamique spatiale et temporelle des patrons de diversitĂ© et de structure des assemblages piscicoles dans la bassin aval du MĂ©kong. * Les effets de la pĂȘche non sĂ©lective dans l'un des plus grands systĂšmes de production halieutique tropicale au monde, le lac le TonlĂ© Sap, avec la mise en Ă©vidence d'une production globalement durable marquĂ©e nĂ©anmoins par une composition altĂ©rĂ©e des communautĂ©s de poissons. * Les rĂ©ponses des assemblages de poissons face aux fluctuations saisonniĂšres et Ă la stabilitĂ© des dĂ©bits dans les riviĂšres non rĂ©gulĂ©es et rĂ©gulĂ©es du bas MĂ©kong. Les rĂ©sultats obtenus lors de cette thĂšse contribuent Ă la connaissance du fonctionnement des peuplements piscicoles et apportent une aide Ă la conception de plans de gestion et de conservation des ressources halieutiques et des autres ressources aquatiques dans le bassin du MĂ©kong et au-delĂ . Cette Ă©tude suggĂšre que : * Le maintien de la dynamique saisonniĂšre des dĂ©bits et de la connectivitĂ© des habitats est impĂ©ratif afin d'assurer la dispersion longitudinale et latĂ©rale des poissons vers des habitats vitaux pour leur reproduction, leur alimentation et leur protection. * L'Ă©tablissement d'une rĂ©glementation appropriĂ©e basĂ©e sur la connaissance des pics migratoires de poissons aux diffĂ©rentes Ă©chelles spatio-temporelles permettrait aux poissons migrateurs de franchir les riviĂšres pour accĂ©der Ă leurs habitats nĂ©cessaires Ă l'accomplissement de leur cycle de vie. Aussi, faire respecter et opĂ©rationnaliser de façon efficace les mĂ©canismes officiels de gestion halieutique aux Ă©chelles locales, nationales et rĂ©gionales, mais aussi allouer suffisamment de moyens pour le secteur de la pĂȘche afin de lutter contre les pratiques de pĂȘche illĂ©gale et pour la mise en Ćuvre de mesures de conservation contribuerait Ă rĂ©soudre les problĂšmes de surexploitation des ressources aquatiques. * La mimique des variations naturelles des dĂ©bits par les barrages hydroĂ©lectriques devrait ĂȘtre priorisĂ©es et appliquĂ©es comme une des mesures permettant d'attĂ©nuer leurs impacts sur les peuplements aquatiques du bassin du MĂ©kong.The Mekong seasonal flow plays a pivotal role in structuring up- and downstream aquatic communities. The thesis investigates the dynamics of spatial and temporal fish community structure in the Lower Mekong system, i.e. the Lower Mekong River and its major tributaries. Using spatial and time-series datasets and univariate as well as multivariate statistical approaches, the thesis highlights: * The importance of flow and other environmental factors in explaining spatial and temporal dynamics of fish diversity patterns and assemblage structure in the Lower Mekong system. * The effects of indiscriminate fishing in one of the world's largest tropical inland fisheries, the Tonle Sap, with the finding of, despite overall stationary catch per unit effort (CPUE), strong alterations in assemblages composition, with decreasing trends in catches of large-sized species, and increasing trends in the catches of some small-sized species. * Contrasted responses of fish assemblages to a gradient of disruption of flow seasonality and predictability due to dams in the Lower Mekong system. The results obtained through this thesis contribute to the ecological understanding of fish assemblages and to the design of applications for long-term planning, monitoring, management and conservation of fisheries in the Mekong Basin and beyond. The thesis suggests that: * Maintaining the Mekong robust and predictably seasonal flood pulse dynamics and habitat connectivity is imperative to ensure fish longitudinal and lateral dispersal ability among critical habitats for breeding, feeding and seeking refuge. * Setting appropriate regulations based on known peak fish migrations at various spatiotemporal scales would allow migratory fish species to pass through rivers, access critical habitats and complete their life cycles. Also, enforcing and operationalizing the existing formal fisheries management mechanisms effectively at local, national and regional levels as well as allocating sufficient resources to the fishery sector to combat illegal fishing practices and implementing fisheries conservation measures in critical habitats would help deal with the problem of overharvesting. * Hydropower-related pulsed flows that can mimic as far as possible the natural pulsed flows are critical to reduce downstream effects on aquatic organisms, and, thus, should be prioritized and applied as one of the measures to mitigate the impacts from existing and planned hydropower dams in the Mekong Basin
Molecular phylogeny reveals a new genus of freshwater mussels from the Mekong River Basin (Bivalvia: Unionidae)
A new genus of freshwater mussels (Bivalvia: Unionidae) is described from the Mekong River Basin as Namkongnaia gen. nov. The validity of the new genus is supported by its unique conchological characteristics, namely the lack of hinge dentition and elongated shells, together with its evolutionary distinctiveness as estimated by multi-locus phylogenetic analyses (mitochondrial COI and 16S, and nuclear 28S genes). The new genus includes two lineages with deep divergence, shown by 5.10% uncorrected COI p-distance. One lineage is a type species described herein as Namkongnaia inkhavilayi gen. et sp. nov. The other is a recognized species under the name âPilsbryoconcha lemeslei (Morelet, 1875)â. Molecular phylogenetic analysis further shows that the new genus belongs to the tribe Pseudodontini, and evolutionarily is closely related to the genus Monodontina Conrad, 1853. However, its conchology is similar to the genus Pilsbryoconcha Simpson, 1900. Time-calibrated phylogeny suggests that the main radiation events of the tribe Pseudodontini occurred during the Late Cretaceous to the Eocene, with the divergence between the new genus and Monodontina placed in the Miocene. The discovery of new freshwater mussel taxa in this study highlights the importance of the Mekong River Basin as one of the worldâs biodiversity hotspots for freshwater fauna
Spatial and temporal changes in fish yields and fish communities in the largest tropical floodplain lake in Asia
International audienceThe Tonle Sap Lake was dominated by few large commercial fishes. Moreover, the total fish yield of the lake was temporally decreased. Also, the fish yields are increased with an increase in the water level fluctuation. The result revealed that fish community in lake is divided into two assemblages: northern assemblage and southern assemblage
Fish Community Responses to Human-Induced Stresses in the Lower Mekong Basin
The Mekong River is one of the world’s largest rivers and has an annual captured fish production of about 2.3 million tonnes, equivalent to around 11 billion USD. Although the Mekong provides important ecological and socioeconomic benefits to millions of people, it is facing intensive change due to anthropogenic stressors. Therefore, it is necessary to understand the changes to the spatiotemporal fish communities to inform sustainable fisheries management. Here, we aimed to characterize patterns of the fish communities and identify the ecological status of each fish community using daily catch data from 2007 to 2018 at 25 monitoring sites in the Lower Mekong Basin (LMB). The collected data were classified by a self-organizing map into four main groups. Group 4 represented the lower Vietnam Mekong Delta (VMD), while groups 1, 2, and 3 were subdivided into subgroups 1a (upper LMB), 1b (upper and middle LMB), 2a (Mekong River below the Khone Falls and Sesan River), 2b (Mekong River below the Khone Falls and Sekong, Sesan and Srepok (3S) Rivers), 3a (Floodplain-Tonle Sap and Songkhram) and 3b (upper VMD). Among the 571 species recorded, 119 were identified as indicator species. Based on the abundance and biomass comparison curves, the fish community of 2b was in a healthier condition with a positive W-statistic value while the rest had a negative W-statistic value. The highest species richness and diversity were observed in 3a and 2b, so these subgroups deserve high management and conservation priority. Likewise, 1a should also be considered as a high priority area since it harbors several endangered and long-distant migratory fishes. It was also noticed that the fish communities of groups 3 and 4, located far from the hydropower dams, remained mostly unchanged compared to those of groups 1 and 2, close to the mainstream and tributary dams in the upper LMB and 3S Rivers
Phylogeny and biogeography of Indochinese freshwater mussels in the genus Pilsbryoconcha Simpson, 1900 (Bivalvia: Unionidae) with descriptions of four new species
Abstract The body of knowledge regarding the classification and evolution of freshwater mussels in the family Unionidae (Bivalvia) in Indochina has recently increased. However, the taxonomic revision of all extant taxa in the region is still ongoing. In this study, the genus Pilsbryoconcha was revised based on an integrative analysis of shell morphology, biogeography, and molecular data. Multi-locus phylogeny indicated the availability of eight species within the genus. Four previously recognized species are P. exilis (Lea, 1838), P. schomburgki (Martens, 1860) stat. rev., P. linguaeformis (Morelet, 1875), and P. carinifera (Conrad, 1837), while four other species are described herein as P. acuta sp. nov., P. mekongiana sp. nov., P. kittitati sp. nov., and P. hoikaab sp. nov. In addition, the neotype of P. carinifera is also designated to clarify its long taxonomic ambiguity. Divergent time estimation and historical biogeography analysis revealed that Pilsbryoconcha originated in the area now called the Khorat Plateau around the middle of the Eocene (mean ageâ=â43.12 Mya), before its range was expanded across Indochina through a series of complex geomorphological changes of river systems, which also led to diversification of the genus