Page title THE UNIVERSITY OF HULL

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1 Page title THE UNIVERSITY OF HULL Observations of the fisheries of the Mekong with notes on the life history strategies of four fish species (Botia modesta, Henicorhynchus siamensis, Helicophagus waandersii and Probarbus jullieni) being a Thesis submitted for the Degree of Doctor of Philosophy in the University of Hull by Sinthavong Viravong B.Sc. (Stara zagora University) M.Sc. (Kasetsart University) October 26

2 Observations of the fisheries of the Mekong with notes on the life history strategies of four fish species (Botia modesta, Henicorhynchus siamensis, Helicophagus waandersii and Probarbus jullieni) SUMMARY The importance of fish species Botia modesta, Henicorhynchus siamensis, Helicophagus waandersii and Probarbus jullieni in the Lower Mekong Basin is to support the livelihoods of the rural peoples. These fish resources not only support important subsistence fisheries but are vital to economies of Cambodia, Vietnam, Southern Lao PDR and Thailand (Songkhram River Basin), both in terns of domestic and export markets. B. modesta, H. siamensis, H. waandersii and P. jullieni migrate twice a year, once in each of the wet and dry season, for reproductive, feeding and refuge purposes. This is a life history strategy linked to finding optimal habitat, which varies from region to region. For example, below the Khone Falls, the critical feeding habitats in the wet season are the Cambodian-Vietnamese floodplains whilst above the Falls these are tributaries, streams, rice fields and flooded areas. Fishing activities in the LMB intensify seasonally, linked to the migration patterns of these species. There are nineteen types of fishing gears commonly used in subsistence fisheries in the Lower Mekong Basin, amongst which gill net (stationary and drifting gillnet) are the most commonly used. These catch mature adult stocks during the wet season and indiscriminately capture both adult and juvenile stages during the dry season, using small mesh sized nets (< cm). to protect the stocks access should be restricted, closed areas and seasons demarcated and controlled, destructive fishing gears and small mesh sized nets banned. This needs to be managed through increased enforcement of fisheries laws and regulations, perhaps by engaging communities. B. modesta, H. siamensis, H. waandersii and P. jullieni all exhibit rapid growth, although differences are found between sites. The fastest growth is for the populations above the Khone Falls at Hatsalao, an area where numerous streams and tributaries join the Mekong. B. modesta, H. siamensis exhibit rapid early growth and a short life span, typical of 'r'-selected fish species. This rapid growth to maturation ensures that the fish contribute to reproduction early in their life. They spawn after the April early May period during the wet season. Differences were found between the populations above the Khone Falls. Essentially, the populations above the Falls spawn earlier possibly because of the floods and the rains arriving earlier there. The reproductive tactics for the B. modesta, H. siamensis and H. waandersii include: biased sex ratios. Usually in favour of females dominating the populations, and production of large numbers of small eggs. These tactics are symptomatic of ensuring that large numbers of eggs are produces to ensure explosive reproduction. These characteristics are typical of 'r'- selected species, and cyprinids in particular. Unfortunately, it was not possible to determine the survival rate of eggs to larval stages in this study. The Mekong River is a transboundary system used for multiple purposes (such as: irrigation for agriculture, hydropower, navigation, water of house hold use, becomes a disposal of waste by the riparian countries. No attention has been paid to understanding the impact of each activity on the fish and fisheries in the Lower Mekong River. This thesis attempts to examine these impact and formulate a manage plan to manage the resources. ii

3 ACKNOWLEDGEMENTS I am indebted to many people who contributed towards the completion of this study. Foremost, I wish to thank my academic supervisor Prof. Dr. I.G. Cowx for his tireless efforts to help, guide and encouragement through this study. The study was funded by NARI Project supporting by DANIDA and the Government of Lao PDR. I wish to thank them for their generosity in financial support which made this study possible. I would like to thank the DLF, NAFRI Directors General, and AMFP Project Chief Technical Advisor Mr. Singkham Phonvisay, Dr. Thong Bouahom and Dr. D. Coates respectively for their keen interest had in this study and their administrative support towards this success. I also wish to thank the NARI Projects Chief Technical Advisors Dr. S.S. Jensen for his continuing effortful support, followups and encouragement made this study possible and successful. I thank the Director of Living Aquatic Resources Research Center, Mr. Lieng Khamsivilay and Champassak Provincial Agricultural and Forestry Department who facilitated me in various ways during the study. Special thanks are expressed to Dr. A.F. Poulsen and Mr. J.V. Jorgensen, Technical Advisor and assistant of AMFP Project with whom we worked closely together during the implementation and data handling of the frame survey. And kindly I express to thank the fisheries staffs from Department of Fisheries of Cambodia based in Phnom Penh (Mr. Lieng Sopha), Thailand based in Udornthani (Dr. U, Suntornratana), and Ho Chi Minh City in Vietnam (Dr. N.T. Tung) and Lao PDR (Mr. K. Bouakhamvongsa) who have worked with the Assessment of Mekong Fisheries Project (AMFP) in helping to organize for and conduct the field survey and supplying raw data on the fisheries and fish migration to this work. I would like to thank to the Khong District fishery officers (Lao PDR), head of villagers for their collaboration and assistance in the conduct of the field work in the Mekong beyond the Khone Falls area and Pakse to collecte fish sample. iii

4 ABBREVIATIONS AMFC AMFP CAM CBD CCRF CEO CESVI CITES CPUE DLF DOF E.I.U EGAT FAO GDP GPS HRD ICCILMB ICLARM IDRC IUCN JC KKU Lao PDR LFA MAF MCS MRC MW NAFRI NGO NMC Assessment of Mekong Fisheries Component Assessment of Mekong Fisheries Project Cambodia Convention on Biological Diversity Code of Conduct for Responsible Fisheries Chief Executive Officer Cooperazione E Sviluppo Convention on International Trade in Endangered Species Catch Per Unit Effort Department of Livestocks and Fisheries Department of Fisheries Economist Intelligence Unit Electricity Generating Authority of Thailand Food and Agricultural Organisation Gross Domestic Production Global Position System Human Resources Development Interim Committee for Coordination of Investigations of the Lower Mekong Basin International Centre for Living Aquatic Resources Management International Development Research Center International Union for Conservation of Nature and Natural Joint Committee Khon Khaen University Lao People Democratic Republic Logical Framework Approach Ministry of Agriculture and Forestry Monitoring Control and surveillance Mekong River Commission Megawatt National Agriculture and Forestry Research Institute Non government Organisation National Mekong Committee iv

5 PAFD RID SEARIN THA UK VNM Provincial Agriculture and Forestry Department Royal Irrigation Development South East Asia Rivers Network Thailand The United Kingdom Vietnam v

6 TABLE OF CONTENTS Page title...i SUMMARY...ii ACKNOWLEDGEMENTS...iii ABBREVIATIONS...iv TABLE OF CONTENTS...vi LIST OF TABLES...x LIST OF FIGURES...xiv CHAPTER ONE Background Development and potential threats to the resources The fish and fisheries in the Mekong River Objectives of the study Structure of the thesis...11 CHAPTER TWO Background to the Mekong Basin Information on target fish species...21 CHAPTER THREE MIGRATION OF BOTIA MODESTA Bleeker, HELICOPHAGUS WAANDERSII Bleeker, HENICORHYNCHUS SIAMENSIS Sauvage and PROBARBUS JULLIENI Sauvage IN THE LOWER MEKONG RIVER Introduction Historical information Local fisher knowledge Objectives Materials and methods Overall approach of the survey Survey design Results Information on villages and fishers in the four Lower Mekong River countries Information on fishing gears used in the four Lower Mekong River riparian countries Distribution of four fish species (B. modesta, H. siamensis, P. jullieni and H. waandersii) in the Lower Mekong River countries...6

7 3.3.4 Migration patterns of four fish species in the Lower Mekong River Maturity of fish species during migration in the Lower Mekong River Size distribution of fish species during migration in the Lower Mekong River Discussion Fisher age, experience and fish species knowledge Gear types and use Seasons, hydrology and migration patterns Functional aspects of migration patterns...9 CHAPTER FOUR ASPECTS OF THE REPRODUCTIVE ECOLOGY OF FOUR MEKONG RIVER FISH SPECIES (B. modesta, H. siamensis, H. waandersii and P. jullieni) Introduction Materials and Methods Sampling procedure Data analysis Result Length-weight relationship Length-frequency distributions Growth rate Reproductive biology Discussion Length-weight relationship, growth rate and size Reproduction, fish size, spawning period and sex ratio Conclusion...12 CHAPTER FIVE PROSPECT FOR SUSTAINABLE MANAGEMENT OF FISHERIES OF LOWER MEKONG RIVER Introduction MRC policies and objectives Resource uses and impacts on the Mekong River Fish and fisheries Status of fisheries in the Lower Mekong River Characteristics of fish production...138

8 .4.2 Indiscriminate catches of juvenile and gravid fishes The market relating to the small size and gravid fish Policy, regulations and objectives Comparison of status with regulations and objectives Issues and options Proprietorship Policing: community involvement in monitoring, control and surveillance Fishing and non-fishing sector interactions Importance of ecosystem-based management Management actions Strategic goal 1: Regulation of fishing effort within the framework of an adaptive management approach Strategic Goal 2: Harmonizing and strengthening of the institutional environment for fisheries, development, research and management in the Lower Mekong basin Strategic goal 3: Adoption of Catchment Management and Integrated Development Strategy models as policies to match the complexities of the fisheries Strategic goal 4: Strengthening of capacity building and the institutional environment for fisheries management, development and research in the Lower Mekong Basin REFERENCES APPENDICES Appendix 2.1(a). The list of fish specie putting in the study of migration in the Lower Mekong Basin Appendix 2.1(b). The list of fish specie putting in the study of migration in the Lower Mekong Basin (cont.) Appendix 2.1(c). The list of fish specie putting in the study of migration in the Lower Mekong Basin (cont.) Appendix 2.2. Survey forms (Form A - E) for fish migration and spawning study in the Lower Mekong River Appendix 3.1. Selected sites for the study of fish migration in the Lower Mekong River Basin by distance from the river mouth and village names...194

9 Appendix 3.2. The age of fisher contributing to the fisheries in the four riparian countries of the Lower Mekong River. The value in bracket represented number of observation fishers Appendix 3.3. The experience of fisher contributing to the fisheries in the four riparian countries of the Lower Mekong River. The value in bracket represented number of observation fishers Appendix 3.4. Mean number of fishing days of using different types of fishing gears by different month of the year in three different fishing habitat (canal, Bassac River and Mekong River). n = the number of particular fishing gear, Mean number of fishing day; River discharge Appendix 4.1. Instantaneous group of the Mekong B. modesta occurring at Hatsalao fishing area, in southern Lao PDR, separating by Bhattacharya method Appendix 4.2. Instantaneous group of the Mekong B. modesta occurring at Donesadam fishing area, in southern Lao PDR, separating by Bhattacharya method Appendix 4.3. Instantaneous group of the Mekong H. siamensis occurring at Hatsalao fishing area, in southern Lao PDR, separating by Bhattacharya analysis method Appendix 4.4. Instantaneous group of H. waandersii occurring at Hatsalao fishing area, in southern Lao PDR, separating by Bhattacharya analysis method Appendix 4.. Instantaneous group of H. waandersii occurring at Khinak fishing area, in southern Lao PDR, separating by Bhattacharya analysis method Appendix 4.6. Instantaneous group of P. jullieni occurring at Hatsalao fishing area, in southern Lao PDR, separating by Bhattacharya analysis method Appendix 4.7. ANOVA test showed variety effort putting in reproductive activities occurring in between big fish and young fish along the Mekong River (P =.; df n-1 = 99)...2 Appendix 4.8. ANOVA analysis indexes obtaining from comparison of eggs size from big fish and small fish size individuals in the Mekong River...2 LIST OF TABLES Table 1.1. List of fish species were died causing by clayey water due to occurring strong erosion during the wet season in Ou River in Lao PDR, in

10 Table 1.2. Fishes in the Lower Mekong River Basin...6 Table 1.3. Characteristics of inland fish production in the Lower Mekong Basin (x1 3 t)....6 Table 1.4. Trend of the catch yield per hectare in Dai fisheries in Tonle Sap River, calculated by major species group (Short lived species) at maximum inundation, (van Zalinge et al. 23)...7 Table 2.1. The country surface areas in the Lower Mekong Basin and their contribution to the annual flow of the Mekong River....1 Table 2.2. Population of the six countries in the Lower Mekong River in 197 and Table 2.3. List of the hydropower and irrigation reservoirs in the Lower Mekong Basin, part of Lao PDR...18 Table 2.4. Information on the reservoirs and large swamp water bodies in Thailand (Reservoirs and large swamp in the Lower Mekong Basin) (Pawaputanon 22)...19 Table 2.. Land utilisation by region in Thailand (in km 2 )...2 Table 3.1. Summary of the main annual wet season migration patterns identified in southern Lao PDR based on three year's data and direct observation....2 Table 3.2. List of fish species selected by the AMFP project, priority for detailed interviews...28 Table 3.3. Selected sites for the study of fish migration in the four Lower Mekong River Basin countries by distance from the river mouth Table 3.4. Numbers, ages and experience of fishers in the Lower Mekong River riparian countries...42 Table 3.. Water bodies, defined through interviewing the villagers, into which B. modesta penetrates and uses for reproduction. THA = Thailand; LAO = Lao PDR, * = streams located in Lao PDR Table 3.6. Water bodies, defined through interviewing the villagers, into which H. siamensis penetrates and used for reproductive purposes. THA = Thailand; LAO = Lao PDR...66 Table 3.7. Water bodies, defined through interviewing the villagers, into which P. jullieni penetrated and used for reproductive purposes. THA = Thailand; LAO = Lao PDR...68 Table 3.8. Water bodies, defined through interviewing the villagers, into which P. jullieni uses as habitat for reproductive purpose in Cambodia...69

11 Table 3.9. Some indicators that fishers realised H. siamensis were associated with the spawning season during their migration in the Mekong River...73 Table 3.1. Possible water bodies defined through interviewing the villager that H. siamensis penetrated into and used as habitat for reproduction in Cambodia...74 Table Some indicators that fishers realized P. jullieni were associated with spawning season during their migration in the Mekong River...7 Table Possible water bodies defined through interviewing the villager that P. jullieni penetrated into and used as habitat for reproductive purpose in Thailand and Lao PDR * indicates streams located in the Lao PDR....7 Table Possible water bodies defined through interviewing the villager that P. jullieni penetrated into and used as habitat for reproduction in Cambodia and Lao PDR...76 Table 4.1. Classification of gonad maturity stages in fish form the Mekong River. (Nikolsky 1963; Bagenal 1978)...99 Table 4.2. Exponents of the length-weight relationships of the four study species at different localities in the Mekong River Table 4.3. Observed size of B. modesta in different months at Hatsalao fishing area, in southern Lao PDR derived from FiSAT. Separation Index (SI) >2 indicated different modes (significant)...14 Table 4.4. Observed size of B. modesta in different months at Donesadam fishing area, in southern Lao PDR derived from FiSAT. Separation Index (SI) >2 indicated different modes (significant)...16 Table 4.. Observed size H. siamensis in different months at Hatsalao fishing area, in southern Lao PDR derived from FiSAT. Separation Index (SI) >2 indicated different modes (significant)...17 Table 4.6. Observed size H. siamensis in different months at Donesadam fishing area, in southern Lao PDR derived from FiSAT. Separation Index (SI) >2 indicated different modes (significant)...19 Table 4.7. Observed size of H. waandersii in different months at Hatsalao fishing area, in southern Lao PDR derived from FiSAT. Separation Index (SI) >2 indicated different modes (significant)...19 Table 4.8. Observed size of H. waandersii in different months at Khinak fishing area, in southern Lao PDR, derived from FiSAT. Separation Index (SI) >2 indicated different modes (significant)...11

12 Table 4.9. Observed size of H. waandersii in different months at Donesadam fishing area, in southern Lao PDR derived from FiSAT Table 4.1. Observed size of P. jullieni in different months at Hatsalao fishing area in southern Lao PDR derived from FiSAT. Separation Index (SI) >2 indicated different modes (significant) Table Observed size of P. jullieni in different months at Donesadam fishing area in southern Lao PDR derived from FiSAT Table Growth characteristics of B. modesta, H. siamensis and H. waandersii in the Mekong River, southern Lao PDR Table Sex ratios of four fish species at different fishing areas in the Mekong River, southern Lao PDR Table Percentage mature and immature stages of four fish species in the southern Lao PDR Mekong River Table 4.1. Size range of mature and immature stages of B. modesta in the Mekong River, southern Lao PDR Table Size range of mature and immature stages of H. siamensis in the Mekong River, southern Lao PDR Table Size range of mature and immature stages of H. waandersii in the Mekong River, southern Lao PDR Table Size range of mature and immature stages of P. jullieni in the Mekong River, southern Lao PDR Table.1. List of fish species that were the backbone for subsistence and commercial fishery in the Lower Mekong Table.2. some example of the importance of small-scale fisheries to inland capture fisheries production in Southeast Asia (Coates 22) Table.3. Estimates of freshwater capture fisheries production in Cambodia, from Sensereivorth et al. 1999, in Coates (22) Table.4. The total freshwater fish production in the four countries (Cambodia, Lao PDR, Thailand and Vietnam) (FAO 22) Table. Issue and options relating to management of fisheries in the Lower Mekong River Basin...147

13 LIST OF FIGURES Figure 1.1. Map of the Mekong River showing the four Lower Mekong Countries, the Khone Falls, the Great Lake (Tonle Sap) and the Mekong Delta....2 Figure 1.2. Scheme of the interchange of fish stock shows possible life cycle relationship between adult and young stock of fishes below and above the Khone Falls....8 Figure 2.1 Monthly average of the Mekong hydrology in 11 different stations along the Lower Mekong River, year 22 (data courtesy to MRC)...2 Figure 2.2 Illustration of the fishing-down process (van Zalinge et al. 22)...22 Figure 3.1. Map showing study sites of fish migration in the Lower Mekong River riparian countries (Thailand, Lao PDR, Cambodia and Vietnam). T1-T13 = study sites in the country of Thailand; L1-L34 = in the Lao PDR; C1-C2 = in Cambodia, and V1-V33 = in Vietnam....3 Figure 3.2 Overview of the survey process...32 Figure 3.3. Overview of survey forms and their interrelationship...3 Figure 3.4. Demographic distribution of fishers interviewed for information on fish migration (n = 46) Figure 3.. Percentage of fishers by age group in the four Lower Mekong River riparian countries. Total number of fishers by country: Thailand (n) = 42, Lao PDR (n) = 133, Cambodia (n) = 136, and Vietnam (n) = Figure 3.6. Distribution of experience amongst fishers interviewed from the four Mekong River riparian countries (Thailand, Lao PDR, Cambodia, and Vietnam) (n = 46)...44 Figure 3.7. Distribution of experience of fishers between the four Lower Mekong River riparian countries. Thailand (n) = 42, Lao PDR (n) = 133, Cambodia (n) = 136, and Vietnam (n) = Figure 3.8. Composition diversity of fishing gears in the four Mekong River riparian countries, n = total number of fishing gears by country...46 Figure 3.9. Percentage of fishing gear type by the range of the mesh size in four Mekong River riparian countries Figure 3.1. Seasonal variation in fishing days by gear used in the Thailand Mekong River. n = the number of particular fishing gear....2

14 Figure Seasonal variation in fishing days by gear used in Lao PDR Mekong River, n = the number of particular fishing gear...4 Figure Seasonal variation in fishing days by gear used in Cambodian Mekong River, n = the number of particular fishing gear...6 Figure Seasonal variation in fishing days by gear used in Vietnam Mekong River, n = the number of particular fishing gear...9 Figure Direction of movement by different months and seasons of the year of four fish species in the Lower Mekong River. n = number of fishers Figure 3.1. Direction of movement of four fish species in different months and seasons of the year in three different river types in Vietnam...64 Figure Seasonal variation in proportion of female fish with ripe eggs in four fish species. n = number of fishing areas Figure Seasonal variation in size distribution of B. modesta in four Mekong River riparian countries during upstream migration. n(1) = Thailand; n(2) = Lao PDR; n(3) = Cambodia; n(4) = Vietnam. (Data obtained through interviewing the villagers)...78 Figure Seasonal variation in size distribution of B. modesta in four Mekong River riparian countries during downstream migration. n(1) = Thailand; n(2) = Lao PDR; n(3) = Cambodia; n(4) = Vietnam. (Data obtained through interviewing the villagers) Figure Seasonal variation in size distribution of H. siamensis in four Mekong River riparian countries during upstream migration. n(1) = Thailand; n(2) = Lao PDR; n(3) = Cambodia; n(4) = Vietnam. (Data obtained through interviewing the villagers) Figure 3.2. Seasonal variation in size distribution of H. siamensis in four Mekong River riparian countries during downstream migration. n(1) = Thailand; n(2) = Lao PDR; n(3) = Cambodia; n(4) = Vietnam. (Data obtained based on interviewing the villagers)...82 Figure Seasonal variation in size distribution of P. jullieni in four Mekong River riparian countries during upstream migration. n(1) = Thailand; n(2) = Lao PDR; n(3) = Cambodia; n(4) = Vietnam. (Data obtained based on interviewing the villagers)...84 Figure Seasonal variation in size distribution of P. jullieni in four Mekong River riparian countries during downstream migration. n(1) = Thailand; n(2) = Lao PDR; n(3) = Cambodia; n(4) = Vietnam. (Data obtained based on interviewing the villagers)...8

15 Figure Seasonal variation in size distribution of H. waandersii in four Mekong River riparian countries during upstream migration. n(1) = Thailand; n(2) = Lao PDR; n(3) = Cambodia; n(4) = Vietnam. (Data obtained based on interviewing the villagers)...87 Figure Seasonal variation in size distribution of H. waandersii in four Mekong River riparian countries during downstream migration. n(1) = Thailand; n(2) = Lao PDR; n(3) = Cambodia; n(4) = Vietnam. (Data obtained based on interviewing the villagers)...88 Figure 3.2 Scheme of the migration along the Lower Mekong River for the four Mekong River fish species...94 Figure 3.26 Functional units in fish ecology (Cowx & Welcomme 1998)...9 Figure 4.1. Examples of length-weight relationships for the Mekong River B. modesta at three different study sites: (a). Hatsalao, (b). Khinak, and (c). Donesadam...13 Figure 4.2. Length frequency of B. modesta occurring in the catch at Hatsalao fishing area at different times, showing a potential growth of cohorts...14 Figure 4.3. Length frequency of B. modesta occurring in the catch at Khinak fishing area, southern Lao PDR....1 Figure 4.4. Length frequencies of B. modesta occurring in the catch at Donesadam fishing area at different times, showing a potential growth of cohorts...1 Figure 4.. Length frequencies of occurring in the catch at Hatsalao fishing area at different times, showing a potential growth of cohorts...16 Figure 4.6. Length frequencies of occurring in the catch at Donesadam fishing area at different times, showing a potential growth of cohorts...17 Figure 4.7. Length frequencies of H. waandersii occurring in the catch at Hatsalao fishing area at different times, showing a potential growth of cohorts...18 Figure 4.8. Length frequency of H. waandersii occurring in the catch at Khinak fishing...11 Figure 4.9. Length frequency of H. waandersii occurring in the catch at Donesadam fishing area at different time, southern Lao PDR Figure 4.1. Modal length of P. jullieni appearing in the catch in the Mekong River, at Hatsalao fishing area, southern Lao PDR Figure Modal length of P. jullieni appearing in the catch in the Mekong River, at Donesadam fishing area, southern Lao PDR...112

16 Figure Length for age growth curves for (a) B. modesta at Donesadam fishing area and (b) H. waandersii based on the von Bertalanffy growth parameters Figure Stages of gonad maturation by different months for B. modesta: (a) at Hatsalao fishing area: (b) at Khinak fishing area: and (c) at Donesadam fishing area...11 Figure Stages of gonad maturation by different months for H. siamensis: (a) Hatsalao fishing area (b) Donesadam fishing area Figure 4.1. Stages of gonad maturation by different months for H. waandersii (a) at Hatsalao fishing area, (b) at Khinak fishing area and (c) at Donesadam fishing area Figure Percentage size distribution of eggs in the gonads of B. modesta, H. siamensis and H. waandersii at (a) Hatsalao; (b) Khinak; (c) Donesadam and (d) the total figure for all areas. n = number of eggs Figure.1. Structure of the Mekong River Commission (MRC 1999)...13

17 CHAPTER ONE 1.1 Background The Mekong (Figure 1.1) is a multipurpose river and the life-blood for the people in the Indo-China region. It is used for navigation, domestic water supply and fishing activities. The Mekong also supports a wide diversity of aquatic animals and plants. In its virgin state, the Mekong could produce annually a wealth of products that are important sources of food, especially in form of fish and other taxa, for people in the region. Historically, fisheries of the Mekong provided food for daily subsistence. However, following an increase in the human population in the last 3 years, the river is facing new challenges, especially associated with infrastructural development, modernisation of agriculture, industrial development, and intra- and inter-country trade. The river is now being developed to allow access to larger vessels (personal obs.). Water is being diverted for agricultural irrigation, hydropower and aquaculture purposes. Fisheries now support not only daily food consumption, but also provide employment, and are a major source of income and foreign exchange earnings for the people of the region and their governments. Because of the ever-growing utilisation and expansion of activities on the Mekong River, it was recognised that management of the resources needed regional cooperation. This co-ordination falls under the auspices of the Mekong River Commission (MRC). The Mekong River Commission is an international commission established in 199. Its political mandate in the Lower Mekong River is to promote and co-ordinate sustainable management and development of water and aquatic resources, in order to meet the countries' mutual benefit and the populace's welfare by tooling strategic programmes and activities and providing scientific information and policy advice. Because the remit of the MRC is restricted to the lower part of the river (Figure 1.1), its membership comprises only the four countries associated with the lower Mekong region, i.e. Cambodia, Lao PDR, Thailand and Vietnam (China and Myanmar are excluded). 1.2 Development and potential threats to the resources Pollution is probably one of the biggest threats to the freshwater environment (Moss 1998; Cowx 22), but in the Mekong many development-related activities could 1

18 1 o E 1 o E CHINA N MYANMAR VIETNAM 2 o N LAO PDR 2 o N Nam Sanh South China Sea Nam Heuang Nam Loei Songkhram Hinboune Sebangfai Sebanghieng THAILAND Mun Khone Falls Sedon 1 o N Se Kong 1 o N Tonle Sap River CAMBODIA Se Pok Gulf of Thailand Bassac River VIETNAM Mekong River Mekong Rivers Delta 1 o N Lake Tonle Sap 1 o N Floodplain & flood areas South China 2 km Sea 1 o E 1 o E Figure 1.1. Map of the Mekong River showing the four Lower Mekong Countries, the Khone Falls, the Great Lake (Tonle Sap) and the Mekong Delta. 2

19 threaten its resources through environmental degradation. The increasing human population in the region is leading to expansion of agriculture and disposal of human and industrial wastes, and putting stress on the water resources and aquatic ecosystem quality and functioning (Cowx 22). Construction of navigation channels, and river canalisation is causing reduction of fish catch because of altering the aquatic habitats that causes reduced fishing habitats; also fishery activity are disturbed by the waves from the ships passing, especially in the Mekong upper north in Lao PDR (from villagers interview. The Construction of the roads networks, hydropower dams and embankment for irrigation or flood control purposes appears to be resulting in loss of fish production by changing the nutrient fluxes, and blocking fish migration routes between spawning, nursing and feeding grounds. Also, the modification of the river flooding regime may allow ill reduce inundation of the floodplains permitting intrusion of, and alluvium deposition by, saline water from the sea. It also appears that alteration of the seasonal water levels is having substantial and social negative consequences e.g. during the past 4 years the Mekong has frequently fluctuated during the wet season with strong current and changes in channel flow that cause some villages (in Bokeo Province) along the Mekong River bank to be swept away (from villagers interview in Bokeo Province, and personal observation). The use of fertilisers and pesticides for agricultural purposes, and waste discharge from industry will probably contaminate the rivers and lakes, resulting in poorer fish stocks and fisheries (Cowx 22). Some development in the lake and floodplain areas, such as building of harbours, oil and gas exploitation and so on, will have negative effects on the existing ecology as they will increase the accessibility to, and employment in, the area (van Zalinge et. al. 22). Slash and burn or deforestation has caused land erosion and degradation of breeding habitat, many fishes were killed by the clayey or turbid water (Table 1.1) and some species of fish have disappeared in some parts of the river, e.g. Dasyatis laosensis has now disappeared in the upper part and the number declined in the lower part of the Ou River in Lao PDR due to huge erosion in the wet season in 199 (Personal communication with villagers). It appears that the conversion of lake and floodplain areas into agricultural land by removal of the flooded forest areas is likely to lead to a loss of feeding grounds and reduce the potential for fish production, with dire consequences for the biodiversity and fisheries (van Zalinge et al. 22). With rapidly increasing human population, the fisheries sector has expanded in the Mekong region. This has also increased the pressure on fish stocks, but fisheries now 3

20 have to support both domestic and export markets. This expansion threatens the fish resources through overexploitation, increased fishing effort, use of illegal and destructive fishing gears (small sized mesh, explosive, poison, electrofishing and so on) and promotion of more efficient and technically advanced gears. Fisheries, which before were for subsistence are now adopting commercial and industrial orientations. Table 1.1. List of fish species were died causing by clayey water due to occurring strong erosion during the wet season in Ou River in Lao PDR, in 199 No Scientific names No Scientific names Daysiatidae Cyprinidae 1 Daysiatis laosensis 1 Mystacoleucus spp. Notopteridae 16 Opsarius pulchellus 2 Chitala ornata 17 Probarbus jullieni 3 Notopterus notopterus 18 Scaphognathops sp. Cyprinidae 19 Sikukia sp. 4 Barbonymus schwanenfeldii 2 Tor tambroides Cyclocheilichthys apogon 21 Tor sp. 6 Cirrhinus molitorella Bagridae 7 Dangila sp. 22 Mystus nemurus 8 Hampala dispar 23 Mystus sp. 9 Hampala macrolepidota Pangasiidae 1 Hypsibarbus sp. 24 Pangasius siamensis 11 Labeo chrysophekadion Sisoridae 12 Labiobarbus leptocheilus 2 Glyptoptorax sp. 13 Macrocheilichthys macrochirus The introduction of exotic fish species and other aquatic fauna in the Mekong River Basin is also becoming a problem through habitat degradation as well as interactions with native species. At least 42 species of exotic fishes has been introduced in the Lower Mekong Basin for four main purposes: aquaculture, stock enhancement, the aquarium trade, and pest control. The introduction of exotic species into the Mekong Basin risks disrupting the native fish fauna through genetic interference, predation, food competition, and the introduction of new diseases (Welcomme & Vidthayanon 1999). Finally, the commercial and industrial fisheries in the floodplain and Tonle Sap and Mekong rivers of the Cambodia, and semi-commercial fisheries in southern Lao, target migratory species (e.g. Paralaubuca typus, Henicorhynchus siamensis, Henicorhynchus spp., Botia modesta, Botia spp., Probarbus jullieni, Helicophagus waandersii, Pangasius larnaudii, Pangasius conchophilus, Pangasianodon. hypophthalmus, 4

21 Scaphognathops spp.) that depend on the seasonal nature of the rivers' fluvial dynamics. Unfortunately, basic information for the management of these resources, such as migration pattern, spawning season and reproductive capacity, remains fragmentary, and a problem for establishing management intervention. 1.3 The fish and fisheries in the Mekong River Due to the heterogeneous nature of the river, the Mekong is one of the most diverse river basins in the world in terms of fish and fisheries. The aquatic fauna is composed of species widespread in Southeast Asia (Taki 1974, 1978). It is estimated that the whole Mekong basin is inhabited by about 1,2 fish species, many of which are still awaiting taxonomic identification (Rainboth 1996). Fishes are the richest species group in the Lower Mekong Basin with 76 species belonging to 228 Genera, 62 Families and 2 Orders. The most prevalent group is the Cypriniformes (363 species), followed by Siluriformes (126 species), and Perciformes (112 species), respectively (Table 1.2). Most of aquatic resources play an important function to the livelihoods of the rural and urban peoples. Fishes, plus other taxa, which are caught from the river and its adjacent waters, are bought for daily consumption by the villagers and fishers themselves. The Mekong is important not only as a source of food but also for income, and it provides employment to a large number of people (Coates 22). A good example of this is the dai fishery in Cambodia, which, in terms of production, is the most important fishery in Cambodia (Lieng et al. 199). However, a high proportion of fish is also caught in rice fields and flooded areas (Guttman 1999), and the Khone Falls fishery in southern Laos PDR is one of the most important fishing areas in the region (Singhanouvong et al. 1996a, 1996b). National consumption of fish from the Mekong regional countries is between 67 kg/person/year in Cambodia (Ahmed et al. 1998) and 8 kg/person/year in Lao PDR (Phonvisay 1999). Fish production has increased year-on-year to accommodate the growing demand in the region, and the fish capture now is mainly for commercial, industrial and export purposes (Table 1.3). Consequently, there is increasing pressure on the fish stocks, and this has been shown through a gradually decrease of the catch-per-unit-effort (van Zalinge et al 2a). For example, the catch from the dai fisheries in Cambodia have decreased from 18,41 t in 199 to 8,894 t in 1999, and from the bamboo filter trap

22 (tone) fishery at Khone Falls Lao PDR the catches have declined from 3. t in 199 to 2.4 t in 1999 (Baird et al. 23). Table 1.2. Fishes in the Lower Mekong River Basin. No Orders Families Genera Species 1 Carchariniformes Pristiformes Rajiformes Osteoglossiformes 2 3 Elopiformes Anguilliformes Clupeiformes Gonorynchiformes Cypriniformes Siluriformes Batrachoidiformes Atheriniformes Cyprinodontiformes Beloniformes Gasterosteiformes Syngnathiformes Synbranchiformes Perciformes Pleuronectiformes Tetraodontiformes Total: Source: (fishbase 22) List of Freshwater Fishes for Cambodia. (fishbase 22) List of Freshwater Fishes for Lao PDR. (fishbase 22) List of Freshwater Fishes for Thailand. (fishbase 22) List of Freshwater Fishes for Vietnam. Table 1.3. Characteristics of inland fish production in the Lower Mekong Basin (x1 3 t). Countries Years Cambodia Lao PDR Thailand Vietnam Sources: (Sam Nuov et al. 22; Souvannaphanh et al. 22; Pawaputanon 22; Duong 22). 6

23 As previously noted (Section 1.2), the Mekong River is a source of water for domestic, industrial, hydroelectric power generation and agricultural purposes, as well as for transport. These increasing demands on the water resources have increased with the human population growth, other infrastructure, and agricultural and industrial development since the 196s. As a result, the Mekong River has undergone changes both in the ecology and fish community structure and dynamics. There has been a steady decline in the ichthyofauna in terms of its diversity and its relative abundance caused by the heavy exploitation (Table 1.4). Although, a substantial part of the fisheries are based on catching migratory fishes, there is a little information on the biology and ecology of Mekong fishes. An important aspect of river ecology is the pronounced longitudinal and lateral fish migrations. Often fishes migrate several hundred kilometers to reach spawning sites or fertile feeding ground (Bayley 1973; Welcomme 198). Migratory behaviour of riverine fishes, and probably of all fishes, results from the separation in space and time of optimal habitats used for growth Table 1.4. Trend of the catch yield per hectare in Dai fisheries in Tonle Sap River, calculated by major species group (Short lived species) at maximum inundation, (van Zalinge et al. 23) No Dai fishery Maximum inundated floodplain Short lived species of fish season (km 2 ) (kg/ha) , , , , , , , survival and reproduction during different life-history stages (Northcote 1984). Therefore, in general migration up and down rivers involves a cyclic alternation between at least two, but more often three habitats (Northcote 1998). The cycle between feeding and survival habitats may occur only once or several times until the sub-adults approach maturity in either a survival or feeding habitat, and then start a reproductive migration to an appropriate spawning habitat over distances that may vary from a few metres to thousands of kilometres. Natural phenomena (rapids, water falls) and human activities (dams and weirs) (Northcote 1998) in and around river channels can interact 7

24 with migratory freshwater fishes. The potential issues are summarised in Figure 1.2, which indicates the interchange of fish stock base on the movement of between the functional habitats, spawning and feeding habitats in the Lower Mekong Basin, between above and below the Khone Falls. KHONE FALLS Upstream Young Adult Downstream Adult Young Mekong River Figure 1.2. Scheme of the interchange of fish stock shows possible life cycle relationship between adult and young stock of fishes below and above the Khone Falls. The Khone Falls may be a key area within the Mekong, which effects life cycle strategies for most Mekong fish species. The problem is that little is known about the ecological impacts of the Khone Falls on the migration of fishes, in the Lao's region as well as throughout the Mekong as a whole. Furthermore, fish migrations in the Mekong River have great implications for fisheries management, since many important fish stocks are shared between countries and therefore call for regional management strategies. Consequently, to be able to predict impacts on fish and fisheries of future development strategies for the Mekong basin, it is important to improve our ecological knowledge of the fishes of the Mekong on which these important fisheries are based. 8

25 1.4. Objectives of the study The problems and threats associated with the fisheries of the Lower Mekong River necessitate that they should be managed on a more sustainable basis. To achieve this, there is a growing need to understand the ecology and dynamics of the fish and fisheries. Unfortunately much of the information needed to inform management is lacking. This study aims to improve knowledge of the life history strategies of four commercially important fish species (Botia modesta Bleeker, Henicorhynchus siamensis debeaufort, Helicophagus waandersii Bleeker, and Probarbus jullieni Sauvage) in the Lower Mekong River and use the information to support a management plan for the Lower Mekong fisheries. The secondary objectives of the study are as follows. 1. to introduce and describe topography of the Lower Mekong River; 2. to use local fisher knowledge to examine the demographic aspects of the fishing communities, the types of fishing activity and the fishing gears used in the Lower Mekong River and migration patterns of four fish species in the this region; 3. to examine the reproductive strategies of four commercially-important fish species around the Khone Falls region of the Mekong River; and 4. to identify the issues and make proposals for the sustainable management of the fisheries resources in the Lower Mekong Region. General information of the four commercially important fish species: Botia modesta Bleeker, 186 is a small loach in the order Cypriniformes, family Cobitidae. In English it is known as "Orange finned loach", "aka Blue Botia"(loaches.com) and "Redtail Botia"(Rainboth 1996). It is one of the small fish found (in Asia) in the Mekong and Chao Phraya Basins reaching their maximum size (TL) up to 2 cm (Rainboth 1996) and 3 cm (loaches.com). Body is naked (scaleless), with grey-green to greyish blue body colour and slight darker on the head and orange to red fins (Kottelat 21; Rainboth 1996; loaches.com). Usually found in big rivers with muddy substrate, also occurs in flooded fields. In natural conditions, worms, crustaceans and insect are diet of B. modesta (Rainboth 1996). In terms of the economical importance, B. modesta is the most common in the Mekong River in Tonle Sap and it forms a substantial part of the dai net catch in Cambodia (Rainboth 1996) and bamboo filter trap at Khone Falls stretch line and seine net in the Mekong at Pakse, 9

26 southern Lao PDR (Baird 1998, personal observation). Botia modesta is now also an economically important species in the aquarium trade (loaches.com). Henicorhynchus siamensis (debeaufort, 1927) is a small carp fish in the order Cypriniformes, family Cyprinidae. In English it is known as "Siamese muddy carp" (Fishbase 26), It is one of the small fish found (in Asia) in the Mekong and Chao Phraya Basins reaching their maximum size (TL) up to 2 cm (Fishbase 26; Rainboth 1996), with large head and broad, snout weakly projecting, an a plain silvery body (Fishbase 26). Usually found in a great abundance at midwater to bottom depth in large and small rivers, and also in floodplain in the wet season (Fishbase 26; Rainboth 199). In natural conditions, algae, periphyton and Phytoplankton are the diet of H. siamensis (Rainboth 1996). In terms of the economical importance, H. siamensis is the most common in the Mekong River in Tonle Sap and it forms a substantial part of the dai net catch in Cambodia (Rainboth 1996) and bamboo filter trap at Khone Falls in the Mekong southern Lao PDR (Baird et al. 23). H. siamensis is also an economically important species in the aquarium trade (Fishbase 26; Rainboth 1996). Helicophagus waandersii Bleeker, 188 is a medium size fish species amongst catfish (Pangasids) and belongs to the order Siluriformes, family Pangasiidae (Shark catfishes) (Fishbase 26, Roberts and Vidthayanon 1991). Its maximum size (TL) reaches to cm (Rainboth 1996) to 7 cm (Fishbase 26). Due to its face looking like a mouse face the local people along the Mekong between Laos PDR and Thailand gave its name Pa Na Nou (Lao PDR) and Pla Sawai Nou (Thailand) (Pa or Pla = fish, Na = face, Nou = mouse, Sawai = catfish fish). H. waandersii is found in the large River of the Mekong and Chao Phraya basins as well as the island of Sumatra, Indonesia (Rainboth 1996; Fishbase 26). In natural conditions, molluscs usually bivalves is the diet of H. waandersii (Rainboth 1996; Fishbase 26); also gastropod usually snails (Singhanouvong et al. 1996(b); personal observation). In terms of the economical importance, H. waandersii is caught with seine, gill net, cast net and sold in the local market. Probarbus jullieni Sauvage, 188 is probably the third largest species amongst Cyprinids themselves in the Lower Mekong Basin following Catlocarpio siamensis (3cm TL) and Luciocyprinus stiolatus (2cm SL). P. jullieni belongs to order Cypriniformes, family Cyprinidae with the maximum size (TL) up to 1 cm (Rainboth 1

27 1996), event to 1 16 cm (SL) (Suvatti 1981; Fishbase 26). Due to its body having seven black stripes, the English common name is known as the seven striped barb, the seven-line barb, by many, including Jullien's golden carp, the Isok barb and rice carp (Smith 194; Phuriphong & Ukkatawewat 1992; Rainboth 1996; Baird & Flaherty 2; Fishbase 26). The distribution in natural water of P. jullieni is wide and spreading in southeast Asia big rivers such as Mekong, Chao Phraya, Mae klong Basins and the Pahang and Perak basins of Malaysia. In the Mekong Basin P. jullieni has been known from as far upriver as Bokeo, Luang Prabang (Baird & Flaherty 2; Taki 1974; Davidson 197) down to the lower part of the lower Mekong in Cambodia and Vietnam (Roberts 1992) and in tributaries (Viravong 1996; fishbase 26). In natural conditions, benthic algae, weeds, insects, bivalves, gastropods (snails) are the diet of P. jullieni (Rainboth 1996; MRC 22; fishbase 26). P. jullieni is a desirable fish for all people, sold fresh in the high price in the market and exported, but has now become an endangered species and trade and transportation forbidden in Lao PDR; it has been listed in IUCN's Red Book of threatened animals as insufficiently known"( Baird & Flaherty 2; IUCN 1996). 1.. Structure of the thesis The thesis is divided into several component areas: Chapter 2 provides an overview of the topography and dynamics of the Mekong River in its component countries and reviews what is known about the biology of the four species chosen for this study. Chapter 3 examines the demographic aspects of the fishing communities, the types of fishing activity and the fishing gears used in the lower Mekong River. Chapter 4 describes the migration patterns of B. modesta, H. siamensis, H. waandersii, and P. jullieni as well as their spawning season and habitat based on indigenous knowledge from within the fishing communities/villages. Chapter investigates the population dynamics of the four target species, including size distributions, growth rates and reproduction. 11

28 Chapter 6 evaluates the information collated for preparation of a fisheries management plan as a contribution towards sustainable exploitation and conservation of the fisheries in the Lower Mekong River. 12