Written for the World Commission on Dams Consultations in East and South-East Asia
February 25, 2000

¹Mekong River Commission Project for Management of the Freshwater Capture
Fisheries of Cambodia

² Department of Fisheries, Phnom Penh, Cambodia

Abstract:

Cambodia has reached the stage where a serious debate has begun about the positive and negative effects of dams, flood controls and irrigation schemes. This is also the concern of the Mekong River Commission, whose mandate is to promote and coordinate sustainable management and development of water and related resources for the riparian countries’ mutual benefit and the people’s well-being. A sound decision making and planning process requires sound information. This has been particularly weak in the fishery sector. The Project for Management of the Freshwater Capture Fisheries of Cambodia has now been working for a number of years with the purpose to reduce the gaps in knowledge and increase management capacities.

The paper attempts to show the importance of fisheries in Cambodia. It then discusses the possible effects dams and other water regulatory works may have on them. Finally, it presents a brief overview of other fisheries management issues.

Fishery yields and fish migrations

Cambodia ranks fourth among the world’s top freshwater capture fisheries with an annual production of 300,000 to 400,000 tons. The high fish yields stem from the annual inundation by the Mekong River of the large floodplains found in central Cambodia around the Great Lake, Tonle Sap, and the plains south of Phnom Penh. The level and duration of the (peak) Mekong floods determine the extent of the inundation of the floodplains and this is positively related to fish productivity. Extensive migrations occur between the floodplains and the river. The river is used as a dry-season refuge and spawning area for the so-called “white” fish, which were found to contribute more than 60% of the total catch. The migratory range of some stocks extends across the borders of the Lao PDR and Viet Nam. The migrations of “black” fish species are much more localised and mainly limited to movements between the floodplain and the nearest deeper water.

Effects of water management

Dam building for hydropower and irrigation purposes started in earnest in the sixties and is still continuing.  Several thousand large and small dams and associated reservoirs and irrigation schemes were built in the Mekong watershed, mostly in northeast Thailand. Obviously, this has led to fragmentation of aquatic habitats and the blocking off of fish spawning and nursery areas to migratory species.

The Mekong watershed above Pakse is mainly affected, as so far the Cambodian dams are tiny and for irrigation only. In the 17-year period from 1982 to 1998 the average wet season flow (June September) at Pakse (Lao P.D.R.) was 15% lower than in the 34-year period from 1923 56. There was also a significant increase in year-to-year flow variability.

On the other hand there were no trends apparent in rainfall data from Luang Prabang between 1923 and 1998. It suggests that the cumulative effect of these water management schemes may have caused the observed reduction in average peak flows in the last two decades. This may have lead to an approximately 20% lesser inundation of the floodplains and may have reduced the sustainable exploitation levels of the Cambodian fish stocks compared to their pre-1960 levels. Recent evidence suggests that variations in maximum inundation levels are roughly proportional to the variations in the size of the “white” fish yield. Thus, losses may have been in the order of some 40-50,000 tons annually (presently valued at US$ 10-15 million). In addition, there are (less well known) losses in “black” fish yields.

So far only one dam has been built on the Mekong main stream itself. This dam is located in Yunnan province, China, where presently a second one is under construction. However, many more potential sites in China, the Lao PDR and Cambodia have been identified, including 10 on the main stream.  Implementation of only a part of these schemes will have further consequences for the fisheries in the basin. Main stream dams, especially in the Lao PDR and Cambodia, would block vital migratory pathways, and access to spawning areas, as would dams on major tributaries, such as the Srepok and Sesan. Assessments are being carried out to quantify fishery losses in terms of their likely impact on food security and employment.

Progress is being made toward hydrological modeling of the Mekong River flow with the aim to simulate the cumulative effects of past and future  water management works on maximum flood levels and the extent and duration of the inundation at various river locations. The model will be linked to the size and distribution of habitats in the floodplains and their fish yields in order to relate an (average) decrease in maximum flow with the subsequent loss of floodplain area and fish yield. Studies to determine the botanical and (fish) faunal diversity of floodplains, as well as fish yield by habitat type are being carried out.

Fishery management issues

Fish is an important part of food security in the country and especially so for the rural poor. A household survey (1995/6) representative of 4.2 million people in central Cambodia found that the average fish consumption rate was 67 kg/capita/year and full-/part-time employment was as high as 45%.

The main internal threats to the fish resources are the destruction of flood plain habitats (due to conversion for agricultural uses) and the open-access situation prevailing in the middle- and family-scale fisheries, which has induced increasing numbers of people to take up full- or part-time fishing.

Access to the most productive parts of the Cambodian fisheries domain has been limited for many decades through a system of government leases, the “fishing lots”. Many fishing lots comprise of relatively large areas of floodplain containing flood forest habitats essential for feeding and breeding of many species. Lots provide some habitat protection.

Open-access fisheries have been expanding rapidly in recent years, catch rates are falling, and conflicts over fishing rights are increasing.

A strategy is being developed to provide solutions to these conflicts and stop the decline in fish catches. It aims at (1) highlighting the importance of fisheries for food security, employment and exports, (2) elucidating their vulnerability to water management schemes, (3) increasing management capacities and well-targeted research, (4) revising and adapting fishery laws, and (5) environmental sensitization of stakeholders and broadening participation in the management of the lots.