ISSN: 1681-7613 Proceedings of the 6th Technical Symposium on Mekong Fisheries Pakse, Lao PDR, 26 th - 28th November 2003 MRC Conference Series No5 Mekong River Commission Vientiane, Lao PDR 6th Technical Symposium on Mekong Fisheries Symposium Proceedings 26th -28th November 2003 Editors: T.J. Burnhill and M.M. Hewitt Suggested citation: Burnhill T.J. and Hewitt M.M. (eds). 2005. Proceedings of the 6th Technical Symposium on Mekong Fisheries, 26th – 28th November 2003. MRC Conference Series No.5. Mekong River Commission, Vientiane. 194 pp. ISSN: 1681-7613 The opinions and interpretations expressed within are those of the authors and do not necessarily reflect the views of the Mekong River Commission © Mekong River Commission P.O.Box 6101, 184a Fa Ngoum Road Ban Sithane Neua, Sikhottabong Vientiane, Lao PDR Telephone: (856-21) 263263. Fax: (856-21) 263264 E-mail: [email protected] Website: www.mrcmekong.org Foreword The Proceedings of the 6th Technical Symposium of the MRC Fisheries Programme have been collated to serve a number of important purposes. They provide a vehicle for young scientists to publish the results of their work; they form a permanent record for future workers to refer to; and they assist in communicating the importance of the fisheries resources in this region to decision makers and the public. Communication must be considered a key element in any development activity, particularly one dealing with natural resources that are subject to many competing uses. This is the case with the resources of the Mekong. The Mekong's waters are used for hydropower, irrigation, navigation and fisheries; its wetlands are used for production of fish, timber products and agriculture; and its ecosystem supports biodiversity and the livelihoods of millions of people. The fishing industry is just one component of the myriad of uses of the Mekong, but a very important one. To ensure that fisheries are appropriately considered in planning processes, it is essential that fisheries workers make available information on this resource and its role in the lives of riparian people. Such information must take many forms, to ensure that we reach all levels of government and society. In this regard, I appreciate these Proceedings, as they document and present much of the data that underpin arguments on the importance of fisheries in the Lower Mekong Basin. The range of papers presented in the Proceedings indicates the scope of work being undertaken by the Fisheries Programme, as well as the technical capacity within the region. I am pleased to see in this issue more papers from fisheries researchers not directly associated with the MRC Fisheries Programme. This indicates both the importance of the Symposium within the region, and the growing interaction between agencies associated with management of the natural resources of the Mekong. Such interaction is essential if we are to make the best use of the human and financial resources we have for developing the fisheries of the Mekong. I hope these Proceedings engender pride among those who have participated in and contributed to the 6th Technical Symposium. Fisheries remain a critical element of any multidisciplinary approach to development in the Mekong. The continued collection, development and distribution of knowledge in the area of fisheries will playa vital role in meeting the needs and keeping the balance of the Mekong River basin, now and in the future. / /, Dr Olivier Cogels Chief Executive Officer Mekong River Commission Secretariat September 2004 iii iv Contents Foreword..............................................................................................................................................iii Section 1: Fisheries Assessment ...........................................................................................................1 Monitoring fish sales at retail markets in Cambodia ......................................................................3 Drift of fish juveniles and larvae and invertebrates over 24-hour periods in the Mekong River at Phnom Penh, Cambodia .............................................................................................................. 19 The dai trey linh fisheries of the Tonle Touch (Touch River), south-east Cambodia ..................35 Using local knowledge to inventory deep pools, important fish habitats in Cambodia................57 Section 2: Aquaculture........................................................................................................................77 Mobile hatchery: a new tool for fisheries extension.....................................................................79 A survey on aquatic animal health problems affecting small-scale aquaculture production and fisheries in Lao PDR ..................................................................................................................................................83 Artificial propagation of Hoeven’s slender Carp (Leptpbatbus hoevenii)....................................89 Comparison of the effect of buserelin in combination with various forms of domperidone and pituitary gland on the induction of spawning and gonadal development in the Thai carp, Barbonymus gonionotus ..................................................................................................................................................................97 Experiments on seed production and commercial culture of freshwater prawns (Macrobrachium nipponense) ................................................................................................................................105 Section 3: Fisheries Management .....................................................................................................115 Stock enhancement as a major element of reservoir fisheries management...............................117 Inland fisheries co-management: what next for Viet Nam? .......................................................127 Participation in fisheries co-management in Kandal province, Cambodia.................................143 Hydrology, habitat and livelihoods on the floodplains of southern Lao PDR .................... 155 Abstract Titles ........................................................................................................................ 179 Agenda..............................................................................................................................................182 List of participants ............................................................................................................................185 v Section 1: Fisheries Assessment Monitoring sales of fish and other aquatic animals at retail markets in Phnom Penh, Cambodia D. Khay* and K.G. Hortle Assessment of Mekong Capture Fisheries Component, MRC Fisheries Programme ABSTRACT Phnom Penh, Cambodia’s capital city has a population of over one million people, of which about 700,000 live in the main central urban area. Inland fish and other aquatic animals are sold at 29 main markets that are supplied from several landing sites and from other diverse sources. We monitored sales at six of these markets in early 2003 and assessed the total numbers of traders in late 2003. Fresh inland fish comprised about 85% of the weight sold of all fresh fish and other aquatic animals. Snakeheads (Channidae) comprised around 40% by weight of all fresh inland fish sold, and with a few other species, made up most of the sales. Exotic species (from aquaculture) comprised only about 1% of sales, so virtually all fresh fish sold were indigenous wild fish or indigenous species grown in floating cages and fed on other small wild fish of lower value. Hence, wild inland fish (either directly or indirectly) still provide most of Phnom Penh’s fish supply. The most important other aquatic animals were marine and freshwater shrimps (Penaeidae and Palaeomonidae). In the 29 markets, over 2,000 people sell aquatic products and about 90% of sellers are female. Based on our limited data, the total daily inland fresh fish sales in these markets were of the order of 12 tonnes/day in March-May and 19 tonnes/day in October 2003, with a value of US$15-24,000 per day. Preserved inland fish sales are also very important but were not quantified. This small-scale industry is the primary supplier of fish to the city and is a significant employer, in particular providing opportunities for women in an environment where they can manage their own businesses. Fish marketing also supports many associated industries. Sales showed no daily patterns and quantities generally varied by about 10-20% from day-to-day. A five-day monitoring programme would therefore provide quite representative data for any market. Monitoring markets poses particular challenges that require novel approaches which we discuss for those planning similar studies. KEY WORDS: Cambodia, Mekong, fisheries, markets INTRODUCTION The residents of Phnom Penh, like those of many large cities in Southeast Asia, rely on local retail markets to provide the fresh and preserved aquatic produce that forms an essential part of their diet. Because they are intermediate between producers and consumers, monitoring sales in these markets can reveal trends in the type, quantity and price of produce available. This paper documents three such monitoring surveys carried out in central Phnom Penh during 2003. Data from a fourth survey, which involved long-term monitoring by a selected group of 20 traders in six markets, is not