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The Mekong is the longest river in southeast Asia. From its source on the Tibetan plateau it runs for 4,800 km through China, Myanmar, Lao PDR, Thailand, Cambodia and Viet Nam to the South China Sea, where it discharges on average 475,000 million m3 per year. The total Mekong Basin (MB) catchment area covers 795,000 km2 and has 73 million inhabitan...
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... However, between 2002 and 2003, the contribution of fisheries to the GDP increased to about 11.7% [43]. After 2003, fisheries sector contribution to GDP increased to about 16% of GDP [44]. Thus, fisheries section plays an important role in a national economy and the Tonle Sap plays a vital role in the fisheries sector. ...
Cambodia is a country where wetlands cover 30% of the country's total area. The Tonle Sap Lake is an important wetland area of Cambodia and Southeast Asia. However, wetland is under threats from infrastructure development, land conversion, water withdrawals, pollution, increased population pressure and hydropower dams building and affect the livelihoods of rural communities. The governance of wetlands is a key action in sustaining the wetland services and the well-being of people. The " wise use " is a key concept of wetland governance. Although there is considerable research on the " wise use " and the application of this concept in wetland management, its application in Tonle Sap remains challenged. Hence, this article addresses the question: How wise use is operationalized for the governance of wetlands in Tonle Sap and what implication it has on the wellbeing of peoples and the ecosystem services? It uses a literature review and a case study to analyze the wetland governance in Tonle Sap, Cambodia. The article describes the wetland governance based on ecosystem services, the direct and indirect driver affecting wetlands and how it threatens the livelihood security of wetland dependent communities. It concludes that the officially wise use of wetlands is a problematic in Tonle Sap.
... There is a clear and urgent need to better understand fish movements for two main reasons. Firstly, a significant proportion of Mekong fishes are migratory, specifically potamodromous (i.e., migratory wholly in freshwater) [8], and, more importantly, this enormous fisheries production relies heavily on the migratory habit of these species [9], [10]. They are harvested mostly with gears and techniques developed to capture fishes during their seasonal migrations [11][12][13][14]. ...
The migration of Siamese mud carp (Henicorhynchus siamensis and H. lobatus), two of the most economically important fish species in the Mekong River, was studied using an otolith microchemistry technique. Fish and river water samples were collected in seven regions throughout the whole basin in Thailand, Laos and Cambodia over a 4 year study period. There was coherence between the elements in the ambient water and on the surface of the otoliths, with strontium (Sr) and barium (Ba) showing the strongest correlation. The partition coefficients were 0.409-0.496 for Sr and 0.055 for Ba. Otolith Sr-Ba profiles indicated extensive synchronized migrations with similar natal origins among individuals within the same region. H. siamensis movement has been severely suppressed in a tributary system where a series of irrigation dams has blocked their migration. H. lobatus collected both below and above the Khone Falls in the mainstream Mekong exhibited statistically different otolith surface elemental signatures but similar core elemental signatures. This result suggests a population originating from a single natal origin but bypassing the waterfalls through a passable side channel where a major hydroelectric dam is planned. The potential effects of damming in the Mekong River are discussed.
... It was also observed that spawning characteristics of fish of the same length and species, but living in locations with different ecological features, had some variations. vanZalinge et al. (2004)2 reported that H. siamensis in the mainstream Mekong mature and reproduce within the first year of life, but that this was longer when they lived in impounded conditions. In the current study, length at 50% maturity of H. siamensis (i.e. ...
The riverine species, Henicorhynchus siamensis (Sauvage 1881), is an important source of protein and an economical fish for the rural population of inland Indochina. Investigated in the present study were the reproductive feeding aspects and growth of H. siamensis living in a lake system. The gonadosomatic index peaked in August, which was delayed compared to river fish, and individuals took 1.5 years to attain the length of 50% maturity (about 200 mm). Stomach contents were dominated by phytoplankton and showed considerable seasonal variation. Asymptotic length of H. siamensis was 264.2 mm, with a 0.75 year−1 growth coefficient and slower growth during the winter. The role of the flood pulse as a major influence on the life history of the fish is also discussed.
... ค่ าพารามิ เตอร์ ความโค้ ง เท่ ากั บ 0.56 ต่ อปี ค่ าอายุ ของปลาเผาะเมื ่ อมี ความยาวเท่ ากั บศู นย์ เท่ ากั บ -0.0163 ต่ อปี ค่ าแอมพลิ จู ด เท่ ากั บ 0.7 และค่ าจุ ดในฤดู หนาว เท่ ากั บ 0.9 โดยปลาเผาะมี อายุ ขั ย เท่ ากั บ 5.35 ปี ค่ าสั มประสิ ทธิ ์ การตายรวม โดยธรรมชาติ และโดยการประมงเท่ ากั บ 2.29, 1.04 และ1.25 ต่ อ ปี ตามลํ าดั บ ค่ าประมาณของ E ในปั จจุ บั นเท่ ากั บ 0.54 ประมาณค่ าขนาดแรกจั บ (L c ) เท่ ากั บ 23.55 ซ.ม. มี รู ปแบบการทดแทน 1 ครั ้ งในรอบปี ค่ าอั ตราการใช้ ประโยชน์ ที ่ ร้ อยละ 50 ของมวลชี วภาพแรกเริ ่ ม จากการ วิ เคราะห์ B'/R เท่ ากั บ 0.34 และค่ าอั ตราการใช้ ประโยชน์ ที ่ ก่ อให้ เกิ ด Y'/R สู งสุ ด เท่ ากั บ 0.64 ซึ ่ งมากกว่ าค่ า E ปั จจุ บั น ดั งนั ้นการใช้ ประโยชน์ ปลาเผาะในแม่ นํ ้าโขงเขตจั งหวั ดหนองคายสามารถเพิ ่ มการลงแรงงานได้ อี ก คํ าสํ าคั ญ: พลวั ตประชากร, ปลาเผาะ, Pangasius bocourti, แม่ นํ ้าโขง, ประเทศไทย คํ านํ า แม่ นํ ้าโขง มี ต้ นนํ ้าอยู ่ บนเทื อกเขาหิ มาลั ย มี ความยาวทั ้ งหมด 4,800 กิ โลเมตร ไหลผ่ านสาธารณรั ฐ ประชาชนจี น สหภาพพม่ า ประเทศไทย สาธารณรั ฐประชาธิ ปไตยประชาชนลาว ราชอาณาจั กรกั มพู ชา และลง สู ่ ทะเลจี นใต้ ที ่ สามเหลี ่ ยมปากแม่ นํ ้าโขง (Mekong Delta) ในสาธารณรั ฐสั งคมนิ ยมเวี ยดนาม และเป็ นหนึ ่ งใน แม่ นํ ้าที ่ มี ความอุ ดมสมบู รณ์ ที ่ สุ ดของโลก (MRC, 2005) จากการประเมิ นจํ านวนชนิ ดปลาที ่ พบในแม่ นํ ้าโขง ตอนล่ างพบว่ า มี มากกว่ า 1,200 ชนิ ด มี ผลผลิ ตจากการทํ าประมง และการเพาะเลี ้ยงสั ตว์ นํ ้าประมาณ 2.6 ล้ านตั น ต่ อปี (Van Zalinge et al., 2004 ...
Population dynamics of Bocourti’s catfish (Pangasius bocourti), in the Mekong River at Nong Khai Province, was studied, using the length frequency data (LFD) to evaluate the von Bertalannfy’s growth function (VBGF), mortality coefficients, recruitment pattern, fishery-exploitation rate (E), relative biomass per recruit (B’/R) and relative yield per recruit (Y’/R). The samples were collected monthly by using gillnets of mesh size; 4, 7, 9 and 14 cm (stretched mesh), during September 2007 to October 2008. The obtained parameters from the seasonalized VBGF, which was fitted to the LFD, were: asymptotic length = 57.62 cm TL, curvature parameter = 0.56 yr-1, the theoretical age at length zero = -0.0163 yr-1, amplitude = 0.7 and winter point = 0.9. The life-span of P. bocourti was estimated at 5.35 year. The instantaneous total, natural and fishing mortality coefficients were 2.21, 1.04 and 1.16 yr-1, respectively. These mortality coefficients yielded the current E at 0.53. The length at first capture (Lc) was estimated at 23.55 cm. The recruitment pattern was one peak in a year. The exploitation rate at 50% of the unexploited B’/R was 0.34. Meanwhile, the estimated Y’/R at maximum exploitation rate was 0.64, which was still beyond the current exploitation rate. It is, therefore, implied that increasing more fishing effort of P. bocourti fisheries in this fishing ground is possible.
Keywords: population dynamics, bocourti’s catfish, Pangasius bocourti, Mekong River, Thailand
... Fishing among the many millions of people engaged in the fishery is also diverse and dynamic, and highly seasonal, but for the majority of rural people a component of wider household livelihood strategies that are themselves highly dynamic (e.g., Arthur and Sheriff 2008; Keskinen 2003). In practice it has indeed proved difficult for fisheries biologists to assess fish abundance , or the level of fishing effort and the status of fish stocks in the Mekong, and to determine accurately what is happening in the fisheries (Bush 2004; Bush and Hirsch 2005; Hill and Hill 1994; van Zalinge et al. 2004). There is no institutionalized system for the effective collection of statistical data on inland capture fisheries, with much of the fishing and catch going unreported (Coates 2002; Sverdrup-Jensen 2002). ...
... This was in the post-Rio Earth Summit era, building on an agreement between the Lower Mekong countries that took on board the discourse of sustainability. This research generated wider interest in the hydrological and ecological drivers of fisheries production, with a greater understanding of fish species diversity, migration, and spawning patterns (Baran 2006; Lamberts 2006; van Zalinge et al. 2004; Coates et al. 2003), largely driven by fisheries by biologists and with less attention to the dynamics of how people use and value these resources. While this research could not determine the production potential or limits of the fisheries, it was highly significant in that it established the annual yields from the fisheries at approximately 2.5 million tonnes (a sevenfold increase from earlier estimates) and established the economic value of the fishery at around $2.5 billion (MRC 2003), though these estimates have not been subject to serious critique (Friend et al. 2009; Bush 2004). ...
Overfishing is a messy and contested term often associated with problems of numbers of people, particularly poor people, and something inherent in the nature of fisheries themselves. It has an intuitive appeal, implying something wrong and something that needs to be done. Although often grounded in science, when overfishing appears in policy debates in the Mekong its definition is rarely stated and the lack of evidence is readily acknowledged. Overfishing is one of a number of potential threats to the Mekong fisheries and there is a risk in overplaying the significance of overfishing, such that policy debates are limited and courses of action narrowed. In the face of current debates about fisheries in the context of water resource management, this article places the storyline of overfishing under closer scrutiny and seeks a more rigorous and nuanced assessment of threats and responses, less constrained by the confines of debates on “overfishing.”
... The Mekong River is the longest river in Southeast Asia. From its source on the Tibetan plateau, it runs 4800 km (Zalinge et al. 2004) to the south through Laos, Myanmar, and Thailand, downward to Cambodia. There, it begin breaking up into plural flows and forms a vast Mekong River Delta in Viet Nam where it finally runs into the South China Sea by eight estuaries. ...
Meiobenthos assemblages in eight estuaries of the Mekong river system were investigated in August 2008 (from the Cua Tieu estuary to the Tran De estuary). In each estuary, one sampling station was established for meiobenthos sampling. Twelve major taxa of meiobenthos were recorded in this estuarine system, including Nematoda, Copepoda, Turbellaria, Polychaeta, Oligochaeta, Tardigrada, Bivalvia, Ostracoda, Amphipoda, Cumacea, Gastrotricha, Gastropoda, and Crustacean Nauplii larvae. The densities of the meiobenthos range from 581 to 3168 inds/10 cm 2 . Nematodes always occupy the highest numbers with a percentage ranging from 64-99%. There are 135 nematode genera recorded in this study with the following as dominant genera Desmodora, Leptolaimus, Halalaimus, Thalassomonhystera, Theristus, Daptonema, Rhynchonema, Parodontophora, and Oncholaimus. Although the biodiversity of the meiobenthos at higher taxa level is not high compared to other marine environments, the estimates of nematode biodiversity at the genus level indicates high values. The increase in number of genera with increasing sampling intensity illustrate that the diversity is underestimated and would have been higher if the authors had considered a larger number of individuals, more replicates per station, and more sampling stations.
... Changes to river flow regimes, loss of habitat and disruption of migratory paths pose significant risks to inland fisheries in the GMS. The fish catch is strongly dependent on the extent, duration and timing of flooding, and access to productive floodplain and wetland habitats for feeding (van Zalinge et al. 2004; Krittasudthacheewa and Apirumanekul 2008). Increasing areas of the floodplain are being cleared or converted to agricultural use: for example, the area of flooded forest around Tonle Sap fell from over 1 Mha in the early 1970s to 0.45 Mha by 1997 (Evans et al. 2004). ...
... Changes in the pattern and timing of flooding are also likely to disrupt physiological cues for fish migration. Blockage of fish migration paths by dams has serious impacts on recruitment and spawning (van Zalinge et al. 2004; Thanh et al. 2004). A high proportion of fish species in Southeast Asian rivers are migratory, with seasonal movements over large distances to access spawning and feeding grounds (Baran 2006); Dugan (2008) reports that up to 70% of the Mekong fishery depends on long-distance migrant species. ...
... Evolution of large eastern flowing rivers at this time may have promoted the eastward dispersal of Gondwanan freshwater taxa into SE Asia (Hall 1998). The Mekong River is now the longest and largest drainage in SE Asia (van Zalinge et al. 2003; Zakaria-Ismail 1994), and it is also the most zoogeographically diverse freshwater region in Asia (Allan et al. 2005; Kottelat 1985). The Mekong is thought to have assumed its current configuration as recently as the Pleistocene (Rainboth 1996a). ...
... As a consequence, harvesting of wild C. micropeltes represents a significant income source for many fishermen, and this species is caught in large numbers across the region (Ambak & Jalal 2006;). In the Lower Mekong Basin, C. micropeltes is one of the most important " black " fish (Campbell et al. 2006; van Zalinge et al. 2003), accounting for up to 20% of all fish harvested in large scale fishing lot systems (Lim et al. 1999; Rot unpublished) and 7% of the total catch from middle-scale fisheries in the Tonle Sap Great Lake (Hai Yen et al. 2009). Over the last 20 years, fishing pressure on C ...
... The 2002 review also reiterated many of the issues that were raised in the 1992 review, and suggested some general responses to ongoing problems in the sector. MRC (2003) and van Zalinge et al. (2004) provided similar more recent descriptions of the LMB fisheries. The LMB fisheries reviews tended to identify technical issues and also to reflect the perspective of national governments, which is a consequence of review teams working mainly with staff of national fisheries agencies . ...
... The LMB fisheries reviews tended to identify technical issues and also to reflect the perspective of national governments, which is a consequence of review teams working mainly with staff of national fisheries agencies . The later reviews (Sverdrup-Jensen, 2002; van Zalinge et al, 2004) also reflect recent changes in emphasis of national policies by including recommendations for a more decentralized approach to management of local fisheries issues, for example, via comanagement. With recent political stability, the growth in regional economies, and continuing pressure to raise living standards, the Mekong system's environment is entering a new phase during which some of the grand ideas envisaged in the Mekong project may be implemented: a massive increase in electricity production through hydropower, regulation of the Mekong mainstream, road building, conversion of forests to plantations, increased agricultural output through irrigation, and development of secondary industries. ...
... In Cambodia and the upper Viet Nam delta floodplains are less than 20 m ASL and most of the wetland area is flooded by river water in most years (Table 9.5); the Great Lake depth increases by up to 9 m during each flood season (Chapter 11), and much of the floodplain is covered by several metres of floodwater for 3-4 months each year. Because of the extensive, deep, and prolonged flooding, this part of the LMB is generally considered to support the most productive fisheries (Lamberts, 2006; van Zalinge et al., 2004). In Thailand and Laos, a small proportion of the total wetland area comprises , and flooding is highly variable in extent and duration between years. ...
The Mekong Basin's (MB's) fisheries are characterized by a diversity of species and habitats, as well as a diversity of gears and fishing activities, as are inland fisheries generally. Most of the Mekong system's fish species are small, growing to maturity in their first or second year and many are extremely fecund or are repeat spawners adapted to take advantage of the great seasonal change in extent of available habitats. Aquatic habitats are most extensive in the lowlands; of most importance to fisheries are large river-floodplain systems, rice fields and associated habitats, large man-made reservoirs, and the estuary and brackish-water zone. Marine fisheries also depend upon nutrients in the Mekong's plume and the division of the fishery into inland and marine by a line across the mouth is quite arbitrary in an ecological sense. Numerous smaller streams and rivers run from uplands of northern Laos, northern Thailand and the Annamite mountain chain, as well as from the smaller mountains that delimit the catchment in southeast and northern Cambodia; uplands form a fifth habitat that is of relatively minor direct importance in fisheries.
... The Mekong River (known in Vietnamese as the Cuu Long River), with a mean discharge volume of 15 000 m 3 /s (the 10th highest in the world), traverses 4 880 km through six countries, and divides into seven major branches when it enters the delta, approximately 170 km from the South China Sea (van Zalinge et al., 2004). The Mekong Delta (3.92 million ha), with a catchment of 49 367 km 2 and a population of 17.42 million (in 2004), is popularly referred to as the food basket of Vietnam; for example, it accounted for nearly half of the national food volume (in 2000 totalling 17.5 million t), 55 % of the national fishery and fruit production and 61 % of the national food export value (Sub-Institute of Water Resources Planning, 2003). ...
... In general, most intensive aquaculture system are more often than not, targeted by environmental lobby groups. It has been shown in this study that the total estimated annual discharge of nitrogen into the Mekong River with an annual discharge of 15 000 m 3 /s, the tenth highest in the world (van Zalinge et al., 2004) is less than 33 000 t (in 2007 for example). This tantamount to a very small fraction of the total potential discharge from other agricultural activities as well as from human waste with a population of 17.2 million in the Delta. ...
Aquaculture of catfish, Pangasianodon hypophthalmus (Sauvage), locally known as “ca tra”, and commonly referred to as striped catfish, river catfish and sutchi catfish, in Vietnam, having recorded a production of 683,000 tonnes in 2007, valued at about 645 million US$ is one of the largest single species based farming system, restricted to a small geographical area, in the world. The product is almost totally exported to over 100 countries as frozen fillets, as an acceptable alternative to white fish. Catfish is farmed mostly in earthen ponds, up to 4 m deep, in nine provinces in the Mekong Delta in South Vietnam. The results of the grow-out system of catfish farming in the Mekong Delta from a survey of 89 farms are presented. The farm size ranged from 0.2 to 30 ha with a mean of 4.09 ha. The frequency distribution of the yield in tonne/ha/crop and tonne/ML/crop corresponded to a normal distribution curve, where 75% of the farms yielded 300 tonnes/ha/crop or more. It was found that the yield per crop was significantly correlated (p < 0.05) to stocking density, pond depth and volume but not to pond surface area. Yields per crop was significantly different (p < 0.05) between upper and lower provinces of the Mekong Delta and water source (river versus channels), amongst others. It was evident that diseases and/or symptoms were observed to occur mostly in accordance with the onset of rains. In this paper the history of the catfish farming in the Mekong Delta is briefly traced, and current harvesting and marketing procedures as well as pertinent social elements of the farming community are dealt with.
