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 delta area of Viet Nam, which has the highest population density, the fishery is likely to be the most heavily exploited. In some areas, the fishery takes on industrial proportions, especially in the Tonle Sap in Cambodia.

At peak times, single gears in the bagnet or dai fishery in Cambodia and Viet Nam can land up to 0.5 tonnes of fish during a 15 minute period. Scenes here are reminiscent of the days of plenty in ocean fisheries, although catches are highly seasonal and influenced greatly by the lunar cycle. There are up to 68 units of dais located along the Tonle Sap River alone, with large numbers operating also in Viet Nam. Over 40 species can be found in a single catch.

Other spectacular fisheries include the large barrage systems which use fences to channel fish towards various traps or holding pens. This seasonal abundance means that large numbers of people are employed in fisheries and associated activities such as gear making, transportation, fish processing and marketing.

In Cambodia, the best fishing grounds are allocated through a bi-annual auction of fishing lots. Lot "owners" not only have fishing rights, but they protect the supporting environment with security staff. The revenue earned from fishing lots makes the Fisheries Department in Cambodia one of the most prominent agencies in the country. There is much interest in these resource management systems as mechanisms for conserving the environment and biodiversity. Unfortunately, the current fishing lot system is criticised for being socially unjust. The wealthier individuals can afford to purchase lots, whilst the poor are often excluded. Conflicts are exacerbated by an auction system which is less than transparent. The Government of Cambodia has recently attempted to improve this system. This is being achieved, in part, by abolishing some of the lots, and again allowing public access in those areas.

An interesting question then emerges – will the resulting access by poor people result in resource destruction? And, if so, what is the balance between the rights of poor communities and losses to biodiversity? It is argued here that the two considerations (poverty and biodiversity) are in fact closely related. Poor people are stakeholders in sustaining biodiversity too - in fact, they are the most dependent upon it. The solution to these problems rests not so much in access to resources but in empowerment to manage them. Fishing "lots" offer a management system with considerable proven benefits for biodiversity. Many countries are interested in adopting similar approaches to resource management. The requirement, therefore, is to find a way of making the system more just and socially acceptable.

Much of the industrial/commercial fishery in the Mekong is based upon exploitation of fishes that are migrating from flood season feeding grounds to their dry season habitats as flood waters recede. The resulting seasonal peak in catches means that far more fish are caught than local communities can consume. In response, a low-input technology industry has developed which turns surplus fish into fish paste, fish sauce and other products. Production of these products spreads the benefits of seasonal production over the full year, and caters for the demand in seasons when fish are less plentiful. Remarkably, catches along the Tonle Sap River can be so high in the peak season, that when prices drop due to oversupply, fishing actually ceases. This is quite possibly the world's last remaining example of oversupply in a fishery.

Impressive as industrial fisheries are, the fishery is still dominated by individual small-scale operations. Survey results have shown that from 64 to 93 percent of rural households in the Lower Mekong Basin are involved in fisheries, both for their own consumption and for sale.

3.3 The role of aquaculture

Aquaculture is currently dwarfed in comparison to capture fisheries, although it is more prominent in some areas than others. Commercial aquaculture (including industrial production for the luxury and export markets) is increasing. In the delta of Viet Nam, cage culture of pangasiid catfish is a growing industry, as is the culture of snakeheads (Channa micropeltes).

Much of the production of higher-value fish relies on the provision of feed made from lower grade fish which are caught from the river and other wetlands. Thus, some aquaculture activities are net consumers of fish (they use up more fish than they produce). Culture and capture are further linked because much of the stock (seed) for commercial aquaculture is taken from the wild. The motivation for aquaculture tends to be profit rather than food.

Smaller-scale aquaculture mixed with farming is particularly prominent in the Thai part of the Mekong Basin, and in the delta in Viet Nam. Not surprisingly, small-scale aquaculture tends to develop best in areas which are away from the main fishing grounds and from the floods.

Fisheries and farming are combined when fish are raised in the waters covering rice fields. Traditionally this practice relies on recruiting wild stocks of fish and other animals. This is a very significant activity in the Mekong. Only recently has production been enhanced through stocking of fish into fields. The intensification of rice farming, particularly the excessive use of pesticides is, however, undermining this additional source of income and food for rural farmers. Modern agricultural practices significantly reduce the biodiversity of products obtained from rice-growing areas.

While aquaculture will clearly play an increasingly important role in the Mekong, there are serious misconceptions about its ability to increase total fish production. The ability of aquaculture to do this will depend upon primarily whether the capture fisheries themselves are sustained. Without appropriate management, capture fisheries are likely to decline much faster than aquaculture can expand, obliterating gains made from fish farming. Another misconception about aquaculture is that it is somehow more environmentally appropriate than catching fish in rivers and other wetlands. Unfortunately, this is not the case.

The aquaculture sector itself is very diverse in the Mekong, but it is exhibiting the usual characteristics that have occurred in agricultural development - that is, simplification of the production system through increasing control over and modification of the environment.

Aquaculture can also cause major environmental disturbances. In the Mekong, major impacts of aquaculture include habitat degradation (especially so for coastal shrimp farming), overexploitation of wild stock for seed and the poor, or sometimes non-existent management of the use of exotic species and biodiversity of native species.

3.4 Threats to aquatic biodiversity in the Mekong

Threats arise from two sources: the impact of fishery activities themselves and the impact arising from outside the fishery sectors. The direct threats to biodiversity posed by the fishery sectors include: the use of destructive fishing methods (explosives, poisons and electrocution); exploitation of fish at vulnerable stages, such as at spawning times; and fishing in sensitive areas such as spawning grounds.

The highly migratory fish stocks are more vulnerable to over harvest. Large numbers of these fish migrate at the same time, making them vulnerable to intensive fishing, and especially to large-scale commercial operations. Examples include the dais on the Tonle Sap River in Cambodia. Licenses have a short duration and this encourages many fishermen to over-exploit the fishery. Fish migrations are often associated with spawning, and concentrations of fish at spawning sites also make stocks vulnerable to over-fishing at the critical spawning period.

Unless properly managed, the release of live animals into the wild can have serious impacts upon biodiversity. This happens primarily through aquaculture when animals are either deliberately released into the wild through fish stocking activities, or when they "escape" from fish farms (a common problem when ponds are flooded seasonally). Biodiversity can be adversely affected when exotic (non-native) species compete with native species in the wild.

Caution must also be exercised when using native species. The natural range of native fish can be quite limited within the basin - they do not all occur everywhere. Some species of Mekong native fish are in fact "exotic" (i.e., naturally foreign) to many parts of the basin. In addition, fish stocks can be composed of a number of distinct populations living in different areas, each with significantly different genetic characteristics. This phenomenon is an example of genetic diversity and it is important. It is probable, for example, that several species have different stocks above and below the Khone Falls.

Impacts upon aquatic biodiversity arising from outside the fishery sectors include changes in the environment and habitats in rivers, brought about by the impact of development. These can have significant impact upon biodiversity and include 1) destruction of local spawning grounds or dry season refuges as a result of stream bed dredging, removal or alteration of vegetation, and bank modification; 2) local changes in the quality (e.g. pollution) and quantity of water available as a result of storage in dams and abstraction for irrigation; and 3) the construction of barriers (dams, weirs, diversions) which, apart from the local environmental disturbances they might cause, act as physical barriers to fish migrations.

Essentially, these influences undermine ecosystem integrity. They invariably lead to a simplification of the river ecosystem and a significant loss of ecosystem area. The loss of river floodplains is a significant cause for concern. These changes result in significant reductions in both aquatic productivity and biodiversity.

Since industrialisation and urbanisation are still quite limited, by comparison to some areas, these have had little impact on the Mekong so far, except locally. However, as populations grow and development pressures increase, it is likely that aquatic life will be affected. The negative consequences of deforestation, inappropriate agriculture, road construction, hydropower and other forms of development are already evident. In the Mekong, the most pressing problem is one of water quantity, not water quality. A second major concern is the loss of riparian vegetation cover, and, in particular, the rapid loss of flooded forests, which provide a crucial aquatic habitat for fishes.