Рыболовство во внутренних водоемах

Small water bodies and their fisheries in southern Africa. CIFA Technical Paper. No. 29.

Overview of inland fisheries

The most important inland fisheries in southern Africa tend to be concentrated on large lakes, such as Tanganyika, Malawi and Kariba, or the floodplains and rivers in the northern parts of the region. The supply of fish is erratic in those areas which lack large water bodies and are otherwise distant from sources of fish. Fishery resources in small water bodies, especially reservoirs built for water supply purposes, seem generally to be underexploited, and the development of these fisheries is a major priority of the Aquaculture for Community Development (ALCOM) project.

The physical and climatic conditions of southern Africa and their effects on fisheries productivity are considered in this paper. The most important factors are that much of the sub-continent is arid or semi-arid, and that many small water bodies lose most of their water, or dry up completely, in the dry season or during droughts. Poor farming practices and the growth of urban populations mean that sedimentation and pollution are becoming increasingly important constraints on fish production.

The nature of fisheries in small water bodies is discussed and the ability to control them completely is seen as one of the distinguishing characteristics of fisheries in small water bodies. Approaches to yield prediction are also considered, but, because small water bodies vary so much, the precision of the models described in this paper is likely to be very low. The possibilities of enhancing fisheries are much greater in small water bodies than in larger ones. The methods available to enhance fisheries include fish introductions or periodic stocking, of which the programme in Zimbabwe to restock dams that dried up during the severe drought of 1991/92 is a good example. Aquaculture options, such as supplementary feeding and cage culture, can also be used, although the application of these methods may be limited by economic conditions.

The possibility of being able to control these fisheries means that social factors become very important management considerations. Institutional aspects are therefore central to the development of fisheries in small water bodies.
Relatively little is known about the small water bodies in the region, and some research priorities include an inventory of them and their physical, chemical and biological characteristics. The information that is required is ranked according to the ease of collecting it, and it is clear that, although progress is being made in this area, much more remains to be learned.

It is concluded that, while small water bodies may never yield as much fish as large ones, they are nevertheless highly productive per unit area and, with proper management, can be an important source of fish