The Zambezi River Basin is one of the richest sources of freshwater fish in southern Africa. This is due to its dense network of rivers and a significant share of natural lakes such as Lake Malawi, Lake Chilwa, Lake Malombe, and others such as lakes Mweru, Mweru-wa-Ntipa and Bangweulu.

In addition, there are also artificial lakes such as Lake Kariba and Cahora Bassa which are fishing grounds for freshwater fish. The Zambezi river itself also provides significant quantities of fish.

Fish provide a significant percentage of protein to the population of the Zambezi Basin states. The demand for fish has risen with growth in population and there are several factors that are required to maintain the levels of supply to meet demand. These factors are, among others, climatic, economic, managerial, cultural, hydrologic and geographic. Fish need exceptionally stable habitats and the depletion of water supply due to droughts, for instance, will have a significant impact on the stocks and their productivity levels. Equally, high floods causing high levels of runoff have a tremendous influence on fish as they are adapted to specific velocities to the extent that spawning becomes impaired. Such conditions are especially true in areas of steep gradients. While direct prohibition of fishing by government during selected periods of the year may yield some direct results, there are other ‘silent’ ways in which fish and aquatic resources are destroyed. Industrial and sewage waste have a serious environmental impact on aquatic resources. These kill fish, for instance, if deposited into water systems and if in large concentrations.

The fish species of the entire Zambezi River Basin are not all known and listed. However, a checklist done in 1972 contains 361 species, 22 of which are estuarine, 217 are from Lake Malawi and 122 from the Zambezi system excluding Lake Malawi. Some of the commercially exploited fish species within the basin include, Tilapia, Clarias, Bagrus meridionalis, utaka (a group of the Haplochromis), Barbus paludinosus, Labeo mesops, Clarias mossambicus and Engralicypris sardella.

Forests including national parks and game reserves play a crucial role in maintaining a balance of the habitat requirements of fish and other aquatic resources. Under conditions of resource scarcity, people will tend to encroach onto forests, national parks and game reserves for settlement and cultivation.

However, poor land husbandry, erosion and deposition in rivers and streams destroy the breeding grounds for fish. Other useful wetlands which may also be under encroachment include marshes and swamps. Poor land use on the upstream of rivers and other riverine systems causes deterioration in productivity rates of fish due to silt loads deposited in habitats suitable for spawning.

Chemical pollution from agricultural activities and settlements is also a threat to the fishing industry. Apart from directly effecting fish, fertilisers in rivers, streams and lakes promote the growth of aquatic weeds which can completely cover the water surface. This condition depletes oxygen levels required by fish and may result in their death. When the water weeds die, the matter may sink in water promoting the growth of algae. When this happens, the water is literally ‘dead’ to support animal life except for the resistant species such as catfish and others. Equally, nitrogen and phosphorus are strong catalysts towards eutrophication that is detrimental to aquatic life. Eutrophication is a process by which water becomes full of phosphates and other nutrients which encourage the growth of algae and kill other organisms.

Deforestation is a major cause of land degradation. Balded lands are often subjected to increased runoff, soil erosion, increased turbidities and heavy loads of silt deposited in Riverine systems. These occurrences are not suitable for fish production. While development projects have an economic value for sectors of the society, the construction of hydraulic structures such as dams, weirs and locks may have an environmental impact on fish. Fish usually have selected spawning grounds and move under velocities of a given range. They are also selective in their locality such that some fish inhabit the juvenile and the middle sections of the river system while others prefer to colonise the senile stage.

Thus the construction of a dam, for instance, may inhibit the amount of water draining downstream thereby reducing the water levels and making it unsuitable for particular types of fish. Some fish are able to jump over short weirs and colonise the other part of the divide while others are restricted to this environment and may have been caught on the wrong side during construction.

Fish within the Zambezi Basin are harvested either for commercial purposes or for domestic consumption. Several fishing methods are available and these include commercial fisheries, where use of boats is common, and artisanal fisheries. The latter method uses lines, traps or nets. The choice of the right size of net is important for the type of fish needed. For instance the small kapenta would require the correct size of mesh which considers the size of the fish. Use of mosquito nets, a practice carried out by some fishers for instance, cannot be recommended for fish such as the tilapia species.

Harvesting of fish from lakes and rivers requires special fishing gear for different types and sizes of fish. Small fish such as the kapenta of Lake Kariba and other lakes of Zambia need fine nets while large ones such as bream, catfish and others require nets with larger mesh. Use of fine meshed nets is usually restricted by law since these may result in catching juveniles. Use of explosives for fishing is equally unsuitable as are some traditional methods using poisons that kill fish and other aquatic animals in large numbers. Under hard economic conditions people tend to overfish to the extent that stocks may be heavily depleted. Government may from time to time impose restrictions on fishing to allow regeneration of the fish populations.

Due to increased tourism activities and in some cases, acquisition of property by private individuals and institutions, access to river banks or the shoal line has been restricted and in some cases prohibited by the landlord. This has affected particularly local communities who previously fished for both subsistence and commercial purposes. Sewage spills and effluent into water courses have had a marked impact on the fishing industry. Introduction of alien species of fish into the water systems of the Zambezi Basin is an issue demanding serious consideration. The introduction of the Nile perch into Lake Victoria, for instance has had dire consequences on the endemic fish as they have been severely subjected to the new predator. Some fisheries experts believe, however, that the introduction of alternative ways to increase fish production are overdue.

Aquaculture is a system of breeding and growing of fish and is fairly new to the southern African region including the Zambezi Basin. Although the practice has some commercial and subsistence benefits, it is also associated with some economic and environmental problems. For example, fish have to be guaranteed a continuous supply of water. Given the dwindling water resources due to droughts, lack of water can cause heavy losses on the stocks available. While the fish need to be constantly fed with seemingly expensive commercial feed, it is thought that unless alternative feeds, preferably prepared locally are found, the venture can be expensive for the smallholder. However there is more sense in expanding aquaculture to rural areas as long as suitable management systems are found and passed on to the rural population. Table 1 reveals that aquaculture has not been vigorously pursued in the region and there is need to seriously consider its expansion. It has to be recognised that these figures do not relate to the Zambezi Basin sources alone but include other fishing grounds and therefore the harvests from the basin could be even less.

Some of the underlying factors inhibiting accelerated development of aquaculture within the Zambezi Basin states include limited water supplies or non-utilisation of small water bodies for fish production, restricted availability of suitable soils required for the construction of fish ponds, lack of social and economic benefits of fish farming and little general awareness of its existence and practice, inadequate skills, shortage of human resources and poor transport to and infrastructure at the market.

The Zambezi Basin’s only marine zone is at the Zambezi Delta in Mozambique. This zone is rich in mangrove vegetation, a suitable habitat for marine aquatic resources such as fish, shrimps, prawns and other sea resources. However, this ecosystem has been subjected to deforestation at a rate of 2.4 percent from 1972 to 1990. Mangroves are cut for poles used for construction of houses, firewood and timber for boats while their leaves are used for animal fodder.

Other threats to the mangrove zone of the basin include pollution from agricultural, industrial and domestic sources, oil spills from ships and diesel from power stations, changes in the watercourse of the upper section of the channel which causes reduction in freshwater from upland, tides, and uncontrolled tourism.

Proper management of the mangrove zone such as through the formulation of management plans, strengthening public awareness and information dissemination, community-based management and strengthening the resources capacity of institutions can guarantee sustainability of the marine resources.

Serious considerations are called for in sustaining the use and management of the fishery resources of the Zambezi Basin, especially in the wake of rising populations and hence increased demand for animal protein.

Fisheries of the Zambezi Basin have multiple functions as they provide food, employment, trading opportunities and financial gains. One of the principal shortcomings associated with artisanal fisheries as opposed to commercial fisheries, is the lack of detail necessary for databases at the national level to feed into a regional database for purposes of monitoring. Closely linked to this is the need for greater cooperation between countries sharing large water bodies. In some cases little information comes to fisheries departments on the amount of catch from outposts, both from freshwater and marine environments, especially catches made by non-commercial fishers.

The importance of research in and development of aquaculture needs to be recognized to promote the production of fisheries in the Zambezi Basin and improve on the nutritional requirement of the basin’s peoples. In this regard, extension services on breeding habits, resource availability, exploitation and management needs to be promoted and should include the full involvement and participation of the fishers and farmers. This has the advantage of limiting antagonism between fisheries departments which are responsible for the implementation of regulations pertaining to fishing and the fishers who may want to fish all year round. In this event it is therefore important to equip the local communities with knowledge regarding resource exploitation and sustainable management.

For purposes of enforcing existing regulations, adequate staff are required for supervision. The staff may not necessarily be the core personnel of the fisheries department but could include the fish farmers and fishers themselves who are then empowered and feel a sense of ownership and authority over the resources they are directly responsible for. While many families within the basin were willing to engage in fish farming, they could be limited to the existing technology that is seen as expensive. In this case, low technological options to farmers are required including initial capital investment and training. Information provision and awareness is also crucial. Farmers and fishers within the Zambezi Basin require adequate access to extension messages.

Information on fisheries would require to be simple and educational such as through posters or cinema.