Biodiversity and Fisheries in the Mekong River Basin

D. Coates, C. Pongsri, O. Poeu, U. Suntornratana, N. T. Tung and S. Viravong

1) Assessment of Mekong Fisheries Component The MRC Programme for Fisheries Management and Cooperation Mekong River Commission Secretariat e-mail: chumnarnp@mrcmekong.org

Abstract

The fishery of the Lower Mekong Basin is one of the most abundant river fisheries in the world. It is of vital importance to the 55 million people who live in the basin. Not only do millions of people earn much needed income from catching, preserving and marketing fish and other aquatic products, they also depend on the fishery as their main source of animal protein. Although the Mekong River Commission (MRC)'s research has demonstrated that the fishery is still in good condition, this could change quickly if it is not well managed and developments in other sectors have adverse impacts on aquatic life.

In the report that follows, the authors propose that in the Mekong the importance of the fisheries is the major argument for protecting the biodiversity. They also discuss threats to biodiversity from within and outside the fisheries sector and measures that should be undertaken to sustain biodiversity.

Keywords: biodiversity, inland fishery, Mekong River Basin

1. Introduction

Within the Mekong River system there are flourishing fisheries which exploit a large number of species. Estimates indicate that approximately 120 fish species are commercially traded, although the bulk of the fishery is based on 10-20 species.

There is much current interest in biodiversity and the need to sustain it. Many people, however, often regard fisheries as a threat to biodiversity because of widespread overexploitation of stocks, the use of destructive fishing gears, large by-catches (killing of unused species) and general mismanagement of resources. But is this true? This paper argues that fisheries are, in fact, not the villain but perhaps the most important ally in the quest for sustaining aquatic biodiversity in the Mekong.

Large tropical river ecosystems have immense value both in terms of high biodiversity and the numbers of people that depend upon that biodiversity for their livelihoods. Unfortunately, all too often, large rivers lose their biodiversity as the environment suffers due to the many demands for water and other resources.

Popular belief is that amongst the world's aquatic environments, it is the sea, and in particular coral reefs, where biodiversity is threatened most. The facts, however, disprove this. The loss of species from freshwater environments is far greater. The IUCN Red List for bony fishes, a database on extinct, threatened and vulnerable species, lists no marine species as extinct, in comparison with 96 freshwater species. Losses in other categories of fish confirm that the threat to biodiversity is much greater in freshwater environments. This is caused by environmental degradation (habitat loss and pollution), not over-exploitation and is generally far worse in freshwaters.

There are some grounds for optimism with respect to freshwater environments, as understanding is growing that freshwater biological resources can be sustained where they are still significant. This is not technically difficult, but it does require awareness and commitment. Serious efforts are also beginning to be taken to rehabilitate degraded rivers, and this is being met with considerable success. Central to this, in developing countries, is the growing appreciation of the importance of freshwater fisheries to the livelihoods of people in rural areas.

2. Materials and methods

A combination of methods were used to understand the biodiversity and fisheries in the Mekong River Basin. These included conventional methods, such as biological studies and marketing surveys, and non-conventional methods, such as desk studies and local ecological knowledge surveys.

3. Results and discussion

3.1 Aquatic biodiversity in the Mekong

There are at least 1200 species of fish, and possibly as many as 1700, living in the Mekong Basin. High diversity is also exhibited by other aquatic animal and plant groups. It is important to note that "fisheries" in the Mekong include other animals and plants as well as fish. Possibly as much as 30 percent of production from the fishery comes from non-fish sources. Although poorly studied, this group of miscellaneous animals and plants is very diverse and important.

In rivers such as the Mekong, which have monsoon climates, tremendous seasonal changes also drastically increase the range and nature of habitats available. These are most marked on the river's floodplain. Every year, the spread of the Mekong's floodwaters influence the basin's aquatic life. This flooding also produces different habitats, in different places, at different times within the year. Changes occur between years due to differences in the timing, extent and duration of flooding. Natural variations in river hydrology, both within and between years, are very important in sustaining ecosystem diversity.

Understanding the role of ecosystem variability (including hydrology) in sustaining the Mekong's rich biodiversity is crucial. Development activities in a river system almost always result in the simplification, or even obliteration, of ecosystem diversity. These disturbances appear to be by far the greatest threat to sustaining aquatic biological resources in the Mekong Basin.

3.2 The fishery resource and its exploitation

Official government statistics still significantly undervalue the Mekong's fishery production in the four Lower Mekong Basin countries. It is between 2.6 and 21 times higher than official statistics suggest. The Lower Mekong Basin produces an estimated two million tonnes of fishery products each year. Of this, less than 10 percent arises from aquaculture.

While finfish dominate the overall catch in the Mekong, other aquatic species are also important, especially with the small-scale fisheries. In Lao PDR, for example, approximately 30 percent of the catch is composed of molluscs, crustaceans, insects, amphibians and reptiles.

The region also has a cottage industry producing dried "seaweed" (algae gleaned from rocks in clearer mountain streams).

Throughout the basin, rice fields are another important source of fish and aquatic species, unless these are impacted by excessive pesticide use.

Fisheries vary greatly from region to region, depending on the availability and access to markets. In areas with more abundant resources and greater human population (e.g., the Thai Mekong and central and southern Cambodia), larger commercial fisheries are dominant. In the...