Inland Fisheries


Overview of inland fisheries

Floodplains are defined as those low lying areas, bordering rivers, which are seasonally inundated by overspill from the main river channel.

During the dry season there is an accumulation of nutrients on the plain in the form of animal dung, rotting vegetation and ash from the fires which sweep them towards the end of the dry period. These nutrients rapidly enter into solution during the earlier stages of flooding, and combined with the river borne silt, support a rapid growth of plants, insects and other forms of aquatic life.

This outburst of productivity provides the essential conditions for the reproduction, feeding and growth of the many species of fish which migrate onto the floodplain from the river channel with the rising waters. The flood cycle is vital to the continued survival of these fish species, and any alterations in the intensity or duration of the floods can produce changes in the fish population in following years.

Because of the great concentrations of fish occurring during migrations onto and off of the floodplain, and in floodplain pools during the dry season, the fisheries of some African floodplains are among the most important of the continent.

Rivers and their floodplains are much sought after for a variety of uses other than fisheries. Many of these uses may conflict with the maintenance of the fish communities. Dam, irrigation and drainage schemes may alter or suppress flood cycles to the detriment of fish stocks, and in many areas of Africa complete fisheries have been lost downstream of major dams. Industrial and agricultural activity can, through the discharge of toxic wastes or the use of insecticides, so pollute the environment that many species are unable to complete their life cycle. This effect, which is most marked in Europe and North America, has not yet appeared as a major problem in Africa, although it remains a potential threat.

Because of the number of competing functions rivers and their floodplains have to be treated as a multi-purpose resource. This implies management so that the sum of the yields from the component uses is maximal. To maximalize yields in this way implies considerable knowledge of the way the resource behaves under different patterns of exploitation. Unfortunately the biology and ecology of river and floodplain fisheries in Africa have been little studied and the basic information necessary for the type of decisions required for management is lacking. Due to this lack the fisheries component of river-floodplain management has been largely overlooked, and a valuable source of animal protein is in many areas threatened by projects aimed at developing an alternative aspect of the resource.

It is therefore proposed that intensified studies are necessary both on the theoretical basis of floodplain fisheries productivity, and on the practical ways in which fisheries may be integrated in the general development of such areas.