Inland Fisheries

1.2.1.4. Floodplains of the world

The floodplains are the areas of low-lying land that are subject to inundation by the lateral overflow of waters from rivers or lakes with which they are associated. It includes the flood way, which consists of the stream channel and adjacent areas that carry flood flows, and the flood fringe, which are areas covered by the flood, but which do not experience a strong current. The floods further bring about such changes in the physico-chemical environment that biota react by morphological, anatomical, physiological or ecological adaptations, or by change in community structure.

The floodplains constitute a valuable part of the environment. They filter, store, and release flood waters, recharge aquifers, store a variety of sediments, and provide habitat for a diversity of wildlife. Despite their susceptibility to flooding, floodplains attract settlers who wish to farm the fertile land and take advantage of the proximity to water and river transportation. Unfortunately, in many areas, the development of floodplains has not been planned or managed adequately, resulting in damage to their natural functions.

Swamps, marshes and other wetlands amount to about 4 million sq kms of which the countries of USSR share more proportion. The fish communities of flood plain rivers have been the subject of special considerations as they are particularly vulnerable to changes in water quality and quantity induced by human activities. The seasonal flooding of river floodplains, along with their lakes, is among the most important factors determining river fish production. The timing and duration of flooding are highly variable, greatly affecting growth and survival of fish. When inundated, the plain contains a rich mosaic of habitats that provide shelter, breeding, nursery and feeding sites for a variety of fish species. Floodplain capture fisheries are mostly seasonal. The fishing is usually indiscriminate, with the removal of all fish.

Many people live along and around rivers and floodplains. Fish and aquatic products provide essential nutrition and buffer food insecurity. In many areas of the world, floodplain fisheries have maintained the same level of catch despite the increasing fishing pressure on fish stocks. Initially, this reduced the average age of stocks fished and increased the efficiency of utilization of their food. Acceleration in growth rate and reduction in the size of maturation of the exploited species has also been common. Subsequently, larger, slower-growing, longer-lived species are apt to be replaced with smaller species of a higher turnover rate. The ability of floodplains to act as sink for carbon and nutrients is conducive to maintaining the stability of this ecosystem.

Restoration of fish stocks is necessary when the tolerance of floodplains to environmental degradation is exceeded - a case often accompanied by high fishing pressure and by the introduction of mitigating measures, such as habitat and fish stocks enhancements .