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Mekong Giant Fish Species: on Their Management and Biology

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Mekong Giant Fish Species: on Their Management and Biology Mekong River Commission Mekong giant fish species: on their management and biology MRC Technical Paper No. 3 April 2002 Report prepared by the MRC Fisheries Programme at the request of the Technical Advisory Body on Fisheries Management in the Lower Mekong Basin Published in Phnom Penh in April 2002 by the Mekong River Commission This document should be cited as: Mattson, Niklas S., Kongpheng Buakhamvongsa, Naruepon Sukumasavin, Nguyen Tuan, and Ouk Vibol. 2002. Cambodia Mekong giant fish species: on their management and biology. MRC Technical Paper No. 3, Mekong River Commission, Phnom Penh. pp. 29. 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. Editor: Ann Bishop © Mekong River Commission P.O. Box 1112, 364 M.V. Preah Monivong Boulevard Phnom Penh, Cambodia Telephone: (855-23) 720-979 Fax: (855-23) 720-972 E-mail: [email protected] Website: www.mrcmekong.org Acknowledgements This report was prepared under the auspices of the Aquaculture of Indigenous Mekong Fish Species (AIMS) project, which is funded by the government of Denmark (through DANIDA). It was prepared at the request of the Technical Advisory Body (TAB) of the MRC Fisheries Programme, which is composed of members from: the Department of Fisheries, Cambodia; the Living Aquatic Resources Research Center (LARReC), Lao PDR; the Department of Fisheries, Thailand; and the Ministry of Fisheries, Viet Nam. The authors are grateful to the Department of Fisheries, Cambodia, the Department of Fisheries, Thailand, the Living Aquatic Resources Research Center in Lao PDR and the Research Institute for Aquaculture Number 2, in Viet Nam for their contribution in compiling this document. Background of the Working Group on Mekong Giant Fish Species The Technical Advisory Body on Fisheries Management (TAB) of the Mekong River Commission (MRC) was established in June 2000. The TAB gives advice to the MRC Fisheries Programme on technical issues relating to basin-wide fisheries management. During the first meeting, five main issues were identified. Among these was the following: Management and preservation of the giant fish species of the Mekong The TAB considered under this item, in particular, the giant catfish, C. siamensis and Probarbus spp. The TAB agreed that action should be taken to conse rve these species, but the strategy for doing this was not entirely clear. More research may be needed. Considerable knowledge exists among researchers in the four MRC countries, but this is not readily available for analysis and for development of a conservation strategy. It was agreed that the MRC Fisheries Programme establish a Working Group on Mekong Giant Fish Species, with participants from the four riparian countries. The Working Group will review and compile existing knowledge on the Mekong giant fish species regarding: important habitats, migrations, biology and life cycles, as well as artificial breeding and results of release of artificially-bred fingerlings, etc. The Working Group may analyse management options and will report to the TAB. The Working Group on Mekong Giant Fish Species consists of one advisor from the MRC Fisheries Programme and one officer from each of the four fisheries departments in Cambodia, the Lao People's Democratic Republic, Thailand and Viet Nam. Table of Contents Summary...................................................................................................................... 1 1. Overview of Giant Fish Species ............................................................................ 3 1.1 Introduction ........................................................................................... 3 1.2 Status of Mekong fish............................................................................. 4 1.3 On rarity and size................................................................................... 4 1.4 Population genetics ................................................................................ 5 1.5 Management of the giant Mekong fish species ......................................... 6 1.6 Conclusions ........................................................................................... 7 2. Species synopsis – Catlocarpio siamensis............................................................. 9 2.1 Natural habitats...................................................................................... 9 2.2 Natural food .........................................................................................10 2.3 Natural spawning season and spawning habitats ......................................10 2.4 Age and size at first maturity .................................................................10 2.5 Natural growth rate and maximum size ...................................................10 2.6 Breeding...............................................................................................10 2.7 Growth rate and culture system ..............................................................11 2.8 Constraints and concerns .......................................................................12 2.9 Characteristics of environments supporting self-sustaining populations.....12 2.10 Other information..................................................................................12 3. Species synopsis – Pangasianodon gigas............................................................ 13 3.1 Natural habitats.....................................................................................14 3.2 Natural food .........................................................................................14 3.3 Natural spawning season and spawning habitats ......................................14 3.4 Age and size at first maturity .................................................................15 3.5 Natural growth rate and maximum size ...................................................15 3.6 Breeding...............................................................................................15 3.7 Growth rate and culture system ..............................................................17 3.8 Constraints and concerns .......................................................................18 3. 9 Characteristics of environments supporting self-sustaining populations.....18 3.10 Other information..................................................................................18 4. Species synopsis – Probarbus jullieni .................................................................. 19 4.1 Natural habitats.....................................................................................19 4.2 Natural food .........................................................................................20 4.3 Natural spawning season and spawning habitats ......................................20 4.4 Age and size at first maturity .................................................................21 4.5 Natural growth rate and maximum size ...................................................21 4.6 Breeding...............................................................................................23 4.7 Growth rate and culture system ..............................................................24 4.8 Constraints and concerns .......................................................................25 4.9 Characteristics of environments supporting self-sustaining populations ...25 4.10 Other information..................................................................................25 5. References............................................................................................................. 27 Mekong giant fish species – on their management and biology Summary The Technical Advisory Body on Fisheries Management (TAB) of the Mekong River Commission (MRC) requested the MRC Fisheries Programme to compile existing knowledge on rare giant Mekong fish species, and to recommend further action for their preservation. This report represents part of the response to the request. It includes biological information as well as management options. The species of main interest, as defined by the TAB, are Catlocarpio siamensis (giant barb), Pangasianodon (Pangasi us) gigas (giant catfish), Probarbus jullieni (Jullien’s Golden Carp or Seven-Striped Barb), Probarbus labeamajor and Probarbus labeaminor. These species grow to a large size, generally over 100 cm in length (except P. labeaminor), and in the case of the giant catfish, up to three metres. These giant fishes are becoming rare in the Mekong River, which is under increasing pressure from growing human populations and development. Attempts at saving the wild populations have so far largely focused on captive breeding, or spawning of wild broodstock, and subsequent release of hatchery-reared offspring into the wild. The report attempts to clarify why these species are rare. In general, it has been shown that the proportion of rare fish species increases with maximum size. It is assumed that large species, which breed comparatively late in life, are more vulnerable to fishing and changes in the environment, particularly in terms of fragmentation of the normal habitats (often caused by water-related development projects, such as dams). Although general biodiversity concerns are valid, it appears unlikely that the giant species play a significant role in terms of the functionality and stability of the Mekong River ecosystem as a whole. The river is the home of some
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