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  • RAP Publication 2001/11

    TONLE SAP FISHERIES:A CASE STUDY ONFLOODPLAIN GILLNET FISHERIES

    by

    Dirk Lamberts

    ASIA-PACIFIC FISHERY COMMISSIONFood and Agriculture Organization of the United Nations

    Regional Office for Asia and the PacificBangkok, Thailand

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    The designations employed and the presentations of material in this publicationdo not imply the expression of any opinion whatsoever on the part of the Foodand Agriculture Organization of the United Nations concerning the legal status ofany country, territory, city or area or of its authorities, or concerning thedelimitation of its frontiers or boundaries. Opinions expressed in this publicationare those of the author and do not imply any opinion whatsoever on the part ofFAO.

    NOTICE OF COPYRIGHT

    All rights reserved. This publication may not be reproduced, in whole or in part, byany method or process, without the written permission from the copyright holder.Applications for such permission with a statement of the purpose and extent of thereproduction desired should be addressed to the Senior Fishery Officer, FAORegional Office for Asia and the Pacific, Maliwan Mansion, 39 Phra Athit Road,Bangkok 10200, Thailand.

    FAO 2001

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    PREFACEPREFACE

    The inland fisheries of Cambodia are among the most productive in the world andcontribute considerably to national food security. Fish from waters all over thecountry provide an essential part of the daily diet for millions of people.

    The fisheries of the Tonle Sap make up almost two thirds of all inland catches.Together with the forests, they are Cambodias most important renewable naturalresource. Not only does fishery sustain the livelihood of many families, it alsoprovides an essential contribution to the national economy and is a source of foreigncurrency income.

    Nowadays, the bounty of the Tonle Sap is intensively exploited. This seems justifiedbut entails considerable risks. Therefore, sufficient understanding of the naturalproductivity is required to allow durable exploitation, safeguarding the resource forfuture generations.

    The issues that threaten the existence of the Tonle Sap fisheries as known today arenumerous and diverse. The undervaluation of the fisheries risks to contribute to thesituation where the sector cannot withstand critical challenges, e.g. from proposeddam construction and the subsequent alterations to the hydrology of the main fishinggrounds.

    Maintaining the parameters of the complex ecosystem that enable the exceptionalproduction of fish is crucial and possibly the only effective management strategy forthe fisheries of the Tonle Sap.

    This publication aims at contributing to a better understanding of the Tonle Sapecosystem and the fisheries and aquaculture sectors. It is written for those who willmake the crucial decisions about the future exploitation of the natural richness of theTonle Sap.

    Veravat HongskulSecretary

    Asia-Pacific Fishery CommissionBangkok, September 2001

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    PREPARATION OF THIS DOCUMENTPREPARATION OF THIS DOCUMENT

    This document, prepared under Special Service Agreement by Mr. Dirk Lamberts, is acase study on floodplain gillnet fisheries in the Tonle Sap, Siem Reap, Cambodia.

    LAMBERTS, D. 2001. Tonle Sap fisheries: a case study on floodplain gillnetfisheries in Siem Reap, Cambodia. FAO Regional Office for Asia and the Pacific,Bangkok, Thailand. RAP Publication 2001/11, 133 p.

    ABSTRACT

    Gillnet fishing makes up a substantial part of the inland fisheries in Cambodia, whichare important to food security and to the national economy. The Tonle Sap ecosystemis one of the most productive in the world. Although little studied, its productivity isgenerally attributed to the pulsed flooding and the specific vegetation of the hugefloodplain.

    Major habitat types are identified in the floodplain of the Tonle Sap based onmacrophyte vegetation and flooding characteristics. These habitats are described inlimnological terms and seasonal variation in water quality. This results in thedefinition of ecologically significant phases of flooding. Their impact on fishes andproductivity of the lake are analysed.

    The second part describes the fisheries of the Tonle Sap ecosystem and theirmanagement. Gillnet fishing in the different habitats of the ecosystem is studied andcatches and productivity are compared. Data on biology and ecology of eight fishes ofeconomic importance are presented. The final part describes the aquaculture of theTonle Sap ecosystem.

    Distribution:

    FAO Fisheries DepartmentFishery Officers in FAO Regional OfficesInternational Fishery Organizations

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    CONTENTSCONTENTSPage

    IntroductionCambodia some relevant facts 2Cambodia and inland fisheries 4

    i. Fish production and consumption 4ii. Contribution of inland fisheries to the national economy 6iii. Fish production and food security 8

    Objectives of the study 9Methodology

    i. The study area and characterization of the habitats 9ii. Identification of the habitat types 12iii. Selection and location of the sampling areas and sites 15iv. Sampling procedure 17

    I. The Tonle Sap ecosystemThe physical environment

    i. Climate 19ii. Geography 21iii. Hydrology 21

    Biotic components of the ecosystem 22Productivity of the ecosystem and natural resource use 25

    i. Ecosystem productivity 25ii. Natural resource use in the Tonle Sap ecosystem 27

    Limnological parameters: methods 30Results of the limnological sampling 31

    i. Diurnal changes in water quality 31ii. Seasonal changes in water quality 35

    Discussion: floodplain habitats ecology 44i. Diurnal changes and patterns 45ii. Seasonal changes and patterns phases of flooding 46

    II. Tonle Sap fisheriesCatches 51Fishing techniques and gear 54

    i. Large-scale fisheries (fishing lots) 55ii. Medium-scale fisheries 57iii. Subsistence (small-scale) fisheries 58

    Fisheries management 60Environmental aspects 68

    III. Gillnet fisheries: case studyMethods:

    i. Experimental gillnet fishing 71ii. Additional fish sampling 71iii. Selected species 72iv. Fish identifications 72v. Ichthyological parameters 72

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    Page

    Results:i. Composition of the gillnet catches 74ii. Selectivity of gillnets comparison of experimental

    gillnet catches 76iii. Habitat-related results of the experimental

    gillnet fishing 81Discussion: floodplain gillnet fisheries 86Selected data and information on 8 species of economic importance 88

    i. Cirrhinus microlepis (Sauvage, 1878) 89ii. Cyclocheilichthys apogon (Valenciennes, 1842) 92iii. Cyclocheilichthys enoplos (Bleeker, 1850) 95iv. Henicorhynchus siamensis (deBeaufort, 1927) 98v. Osteochilus melanopleurus (Bleeker, 1852) 101vi. Paralaubuca typus (Bleeker, 1865) 103vii. Trichogaster microlepis (Gnther, 1861) 106viii. Trichogaster trichopterus (Pallas, 1770) 110

    IV. Tonle Sap aquacultureDescription of Tonle Sap aquaculture systems 114Environmental aspects 118National policies, strategies, plans and programmes for Tonle Sap aquaculture development 119

    AnnexesAnnex 1. Macrophyte species composition of the habitats 121Annex 2. Fish species encountered in the case study 124Annex 3. Summary overview of sampling activities 127

    References 128

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    ABBREVIATIONS & ACRONYMSABBREVIATIONS & ACRONYMS

    ASEAN Association of Southeast Asian NationsCFw Weight-based condition factor (dimensionless)CPUE Catch per Unit of EffortCPUEn number-based CPUECPUEw weight-based CPUEDANIDA Danish International Development AgencyFAO Food and Agriculture Organization of the United NationsGDP Gross Domestic ProductGm3 Giga (109) cubic metresGIS Geographic Information SystemGPS Global Positioning SystemMAFF Ministry of Agriculture, Forestry and Fisheries of CambodiaMRC Mekong River CommissionNIS National Institute of Statistics, Ministry of Planning of CambodiaUNICEF United Nations Childrens FundWFP World Food Programme

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    ACKNOWLEDGMENTSACKNOWLEDGMENTS

    Many have played an important role in all the different stages of the preparation ofthis study, its implementation and the final analysis and write-up.

    The staff of the Provincial Office of the Department of Fisheries in Siem Reap, TimSarath in particular, did a marvellous job collecting data, together with the staff of theParticipatory natural resources management in Tonle Sap region project(GCP/CMB/002/BEL). Their eagerness to learn and their determination to maintainthe high levels of scientific rigour required for a study such as this contributed to thevalue and validity of the data, the results and most importantly of the modestcontribution this study may make to a durable management of the rich resources ofthe Tonle Sap.

    I am indebted to Director Nao Thuok and Deputy Director Sam Nouv of theCambodian Department of Fisheries for sharing information and facilitating theprogress of the study.

    Among those who have contributed through their critical questioning and toughdiscussions to my understanding of the ecology of the flooded forest, I am particularlyindebted to Taber Hand and to Heiko Seilert.

    Patrick Evans, Rob Overtoom and Eleanor Briggs kindly provided photographs. I amgrateful to Etienne Delattre for the GIS data analysis.

    Chavalit Vittayanon of the Department of Fisheries of Thailand, kindly allowed me touse his photographs on fish taxonomy.

    Chieng Sisovin and Patcharee Chadpool did an excellent job meticulously entering thedata for processing.

    Funding for this study was provided by the Bel