Larval and Juvenile Fish Communities of the Lower Mekong Basin
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ISSN: 1683-1489 Mekong River Commission Larval and Juvenile Fish Communities of the Lower Mekong Basin MRC Technical Paper No. 49 June 2015 Cambodia . Lao PDR . Thailand . Viet Nam For sustainable development Page i Mekong River Commission Larval and Juvenile Fish Communities of the Lower Mekong Basin MRC Technical Paper No. 49 June 2015 Cambodia . Lao PDR . Thailand . Viet Nam For sustainable development Published in Phnom Penh, Cambodia in June 2015 by the Mekong River Commission Cite this document as: Cowx, I.G; Kamonrat, W.; Sukumasavin, N.; Sirimongkolthawon, R.; Suksri, S. and Phila, N. (2015) Larval and Juvenile Fish Communities of the Lower Mekong Basin. MRC Technical Paper No. 49. Mekong River Commission, Phnom Penh, Cambodia. 100 pp. ISSN: 1683-1489. The opinions and interpretations expressed within are those of the authors and do not necessarily reflect the views of the Mekong River Commission. Editors: Starr, P.; Rodriguez, F.E.; Degen, P.; So, N. and Ngor, P.B. Graphic design and layout: C. Chheana Office of the Secretariat in Phnom Penh (OSP) Office of the Secretariat in Vientiane (OSV) 576 National Road, #2, Chak Angre Krom, Office of the Chief Executive Officer P.O. Box 623, 184 Fa Ngoum Road, P.O. Box 6101, Phnom Penh, Cambodia Vientiane, Lao PDR Tel. (855-23) 425 353 Tel. (856-21) 263 263 Fax. (855-23) 425 363 Fax. (856-21) 263 264 © Mekong River Commission E-mail: [email protected] Website: www.mrcmekong.org Contents List of figures ........................................................................................................................................... v List of tables .......................................................................................................................................... viii Abbreviations and acronyms ................................................................................................................... ix Executive Summary ................................................................................................................................ xi Acknowledgements ................................................................................................................................ xv 1 Introduction ......................................................................................................................................... 1 2 Sampling Methods .............................................................................................................................. 5 2.1 Spawning behaviour and habitats of fish .................................................................................... 5 2.2 Larval and juvenile fish sampling ................................................................................................ 6 2.3 Sampling strategy ........................................................................................................................ 8 2.4 Fisheries data and analysis ......................................................................................................... 15 2.5 Indigenous knowledge ............................................................................................................... 18 3 Results ............................................................................................................................................... 19 3.1 Catch composition between sampling gears ............................................................................. 19 3.2 Conical plankton nets ................................................................................................................ 20 3.2.1 Species composition – site variation ............................................................................... 20 3.2.2 Species composition – seasonal variation ....................................................................... 26 3.3 Seine net ..................................................................................................................................... 33 3.3.1 Species composition – site variation ............................................................................... 33 3.3.2 Species composition – seasonal variation ....................................................................... 37 3.4 Larval and juvenile size and abundance ................................................................................... 45 3.4.1 Conical plankton nets ...................................................................................................... 45 3.4.2 Seine nets ......................................................................................................................... 56 3.5 Indigenous knowledge ............................................................................................................... 56 4 Discussion ......................................................................................................................................... 63 4.1 Review of outputs .................................................................................................................... 63 4.2 Implications of dams ............................................................................................................... 70 4.3 Conclusions and recommendations ......................................................................................... 75 5 References ......................................................................................................................................... 77 Page iii Larval and Juvenile Fish Communities of the Lower Mekong Basin Appendix 1: Indigenous Knowledge Questionnaire .............................................................................. 81 Appendix 2: Relationship between length of larval and life stages and their age in days ..................... 83 Appendix 3: Water velocity (km/day) in Mekong River at different locations and seasons ................. 85 Page iv List of figures Figure 1.1 Location of existing and proposed hydropower schemes in the Mekong River Basin ................................................................................................. 1 Figure 1.2 Profile illustrating location of proposed hydropower schemes in the Lower Mekong River Basin. .................................................................................... 2 Figure 2.1 Design of conical plankton net ...................................................................................... 7 Figure 2.2 Design of seine net ......................................................................................................... 7 Figure 2.3 Location and photographs of each sampling location .................................................. 11 Figure 2.4 Comparison of water levels at selected sites on the Mekong mainstream .................. 15 Figure 3.1 Comparison of catch composition by conical plankton and seine nets ........................ 19 Figure 3.2 Cluster analysis on fish sampling at 11 sites ................................................................ 20 Figure 3.3 MDS analysis of fish sampling at 11 sites .................................................................. 21 Figure 3.4 Variation in species diversity collected by conical plankton nets between 11 sites .... 23 Figure 3.5 Relative abundance of 20 most common species of fish collected by conical plankton nets at 11 sites ............................................................................................................. 24 Figure 3.6 Average linkage cluster (a) and MDS (b) analyses of species abundance .................. 25 Figure 3.7 Seasonal variation in species diversity collected by conical plankton nets between 11 sites ......................................................................................................................... 27 Figure 3.8.1 Seasonal variation in species abundance of fish collected by conical plankton nets between 11 sites .......................................................................................................... 28 Figure 3.8.2 Seasonal variation in species abundance of fish collected by conical plankton nets between 11 sites .......................................................................................................... 29 Figure 3.8.3 Seasonal variation in species abundance of fish collected by conical plankton nets between 11 sites .......................................................................................................... 30 Page v Larval and Juvenile Fish Communities of the Lower Mekong Basin Figure 3.9 Cluster (a) and MDS analyses (b) on fish caught by conical plankton nets at 11 sites and 6 sampling times ................................................................................................... 31 Figure 3.10 Relationship between 20 dominant species caught by conical plankton nets at 11 sites and four environmental factors .................................................................................... 33 Figure 3.11 Variation in species diversity collected by seine nets between 11 sites ...................... 34 Figure 3.12 Relative abundance of species of fish collected by seine netting at 11 sites ............... 35 Figure 3.13 Average linkage cluster (A) and MDS (B) analysis on the species abundance ........... 36 Figure 3.14 Seasonal variation in species diversity collected by seine netting between 11 sites .. 40 Figure 3.15.1 Seasonal variation in species abundance of fish collected by seine netting between 11 sites . ........................................................................................................