Mekong Fisheries and Mainstream Dams
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STRATEGIC ENVIRONMENTAL ASSESSMENT OF HYDROPOWER ON THE MEKONG MAINSTREAM MEKONG FISHERIES AND MAINSTREAM DAMS Eric BARAN (WorldFish Center) Fisheries sections of the Strategic Environmental Assessment of hydropower on the Mekong mainstream prepared for the Mekong River Commission by ICEM – International Centre for Environmental Management 1 October 2010 STRATEGIC ENVIRONMENTAL ASSESSMENT OF HYDROPOWER ON THE MEKONG MAINSTREAM Fisheries ABOUT THE SEA OF HYDROPOWER ON THE MEKONG MAINSTREAM The Strategic Environmental Assessment of Hydropower on the Mekong mainstream (SEA) was initiated by the Mekong River Commission and coordinated by the MRC’s Initiative for Sustainable Hydropower. Strategic Environmental Assessments address broad strategic issues usually relating to more than one hydropower project. SEAs follow similar steps to Environmental Impact Assessments but have much larger boundaries in terms of time, space and subject coverage. The SEA is a tool to examine the broad strategic concerns which need to be resolved and decided prior to making project specific decisions. In this case, the SEA of hydropower on the Mekong mainstream was asked to provide an understanding of the implications of mainstream hydropower development and recommendations on whether and how the proposed projects should best be pursued. The SEA is intended to feed into the MRC Basin Development Plan (BDP), and ultimately to support national decisions concerning the mainstream proposals. The SEA was implemented between May 2009 and October 2010 by the International Center for Environmental Management (ICEM) and covered nine themes: Power systems, Economic systems, Hydrology and sediment regime, Terrestrial systems, Aquatic systems, Fisheries, Social systems, Navigation and Climate change. The SEA team included: MRCS ISH: Mr Voradeth Phonekeo (Project Manager), Mr Larry Haas (Technical Advisor). ICEM: Dr Jeremy Carew‐Reid (Team Leader), Mr Tarek Ketelsen (Project Coordinator), Mr Peter‐ John Meynell, Dr Eric Baran, Dr Elizabeth Mann, Prof. Peter Ward, Mr John Sawdon, Dr Benoit LaPlante, Dr Carlos Yermoli, Mr Cong An Tranh, Dr Apichart Annukalumphai, Dr Suppakorn Chinnarvo, Dr Kanokwan Manoram, Ms Piyathip Eawpanich, Dr Nguyen Huu Thien, Dr Nguyen Xuan Nguyen, Dr Nguyen Van San, Ms Nguyen Thi Nga, Mr Meng Monyrak, Mr Try Thuon, Mr Phaknakhone Rattana, Mr Sae Senpaty, Mr Bonheung Phantasith. The current report is an excerpt of the whole SEA study, and focuses on fish resources only. The details and conclusions of this SEA are available on the following websites: www.mrcmekong.org/ish/SEA.htm and www.icem.com.au Citation: Baran E. 2010. Mekong fisheries and mainstream dams. Fisheries sections in: ICEM 2010. Mekong River Commission Strategic Environmental Assessment of hydropower on the Mekong mainstream, International Centre for Environmental Management, Hanoi, Viet Nam. 145 pp. Dr. E. Baran is Senior Scientist at the WorldFish Center (www. worldfishcenter.org) Cover images: Mekong River Commission, 2010; Zeb Hogan, 2009; Peter‐John Meynell, 2010, Peter Ward, 2003 International Center for Environmental Management 32 Xuan Dieu St., Tay Ho, Hanoi, Vietnam www.icem.com.au 2 STRATEGIC ENVIRONMENTAL ASSESSMENT OF HYDROPOWER ON THE MEKONG MAINSTREAM Fisheries 1 FISHERIES BASELINE ASSESSMENT........................................................................................... 6 1.1 STATUS OF MEKONG FISH BIODIVERSITY 6 1.1.1 Freshwater fish diversity in the Mekong and worldwide ...............................................................6 1.1.2 Freshwater fish diversity in the 3 main migration zones................................................................7 1.1.3 Freshwater fish diversity in the six main ecological reaches ..........................................................9 1.1.4 Freshwater fish diversity in Mekong hydrological sub‐basins ......................................................10 1.2 STATUS OF MEKONG CAPTURE FISH PRODUCTION 12 1.2.1 Fish catch in the Mekong countries..............................................................................................12 1.2.2 Mekong fish catch and population ...............................................................................................15 1.2.3 Mekong fish catch and food security............................................................................................16 1.2.4 Capture fisheries in the six main ecological reaches ....................................................................21 1.3 STATUS OF MEKONG AQUACULTURE PRODUCTION 30 1.3.1 Status of aquaculture production in the Mekong Basin countries ...............................................30 1.3.2 Dominant species in the aquaculture sector ................................................................................31 1.4 SOCIOECONOMIC STATUS OF MEKONG FISH RESOURCES 33 1.4.1 Economic value of capture fisheries.............................................................................................33 1.4.2 Economic value of aquaculture fish..............................................................................................34 1.4.3 Employment value of capture fisheries and aquaculture.............................................................35 1.5 FISH ECOLOGY AND RISKS IN RELATION TO DAM DEVELOPMENT 36 1.5.1 Factors driving fish production .....................................................................................................36 1.5.2 Fish groups in the Mekong............................................................................................................38 1.5.3 Species guilds................................................................................................................................39 1.5.4 Fish migrations..............................................................................................................................40 1.5.5 Dams and disruption of migrations ..............................................................................................47 1.5.6 Interactions between the river and the coastal zone...................................................................49 1.6 FUTURE TRENDS WITHOUT MAINSTREAM HYDROPOWER DEVELOPMENT 50 1.6.1 Trends in aquaculture and capture fisheries ................................................................................50 1.6.2 Perspectives On aquaculture and capture fisheries .....................................................................52 1.6.3 Aquaculture as a replacement FOR capture fisheries?.................................................................54 2 FISHERIES IMPACT ASSESSMENT .....................................................................................58 2.1 CLUSTERS OF MAINSTREAM DAMS 58 2.1.1 Upstream cluster of dams.............................................................................................................60 2.1.2 Middle cluster of dams .................................................................................................................61 2.1.3 Downstream cluster of dams........................................................................................................62 2.1.4 Overview.......................................................................................................................................65 2.2 HYDROLOGICAL CHANGES FORECASTED IN RELATION TO FISHERIES 67 2.3 WETLANDS, FLOODPLAINS AND FISH PRODUCTIVITY 72 2.4 LONG‐DISTANCE MIGRATORY FISH SENSITIVE TO MAINSTREAM DAM DEVELOPMENT 73 2.5 IMPACT OF DAMS ON MIGRATORY FISH AND ON CAPTURE FISH PRODUCTION 75 2.5.1 Method 1: Catch monitoring in the mainstream..........................................................................75 2.5.2 Method 2: Surveying experts........................................................................................................76 2.5.3 Method 3: Catch statistics in Cambodia .......................................................................................76 2.5.4 Method 4: Update integrating black fish production in rice fields...............................................77 2.5.5 Method 5: Assessment based on habitat types............................................................................78 2.5.6 Synthesis.......................................................................................................................................80 2.6 GAINS IN FISH PRODUCTION FROM DAM RESERVOIRS 83 2.6.1 Estimates of productivity based on surface area, depth and flow ...............................................84 2.6.2 Estimates of productivity based on surface area alone................................................................84 2.7 MEKONG MARINE FISHERY 86 2.8 ANALYSIS BY DAM CLUSTER 87 2.8.1 Upstream cluster of dams.............................................................................................................87 2.8.2 Middle cluster of dams .................................................................................................................89 2.8.3 Downstream cluster of dams........................................................................................................92 3 STRATEGIC ENVIRONMENTAL ASSESSMENT OF HYDROPOWER ON THE MEKONG MAINSTREAM Fisheries 3 AVOIDANCE AND MITIGATION MEASURES.............................................................................96 3.1 INTRODUCTION 96 3.2 AVOIDANCE MEASURES BEFORE DAM CONSTRUCTION 96 3.2.1 Dam location.................................................................................................................................96