La pêche continentale

Current status of fisheries and fish stocks of the four largest African reservoirs. Kainji, Kariba, Nasser/Nubia and Volta. CIFA TECHNICAL PAPER 30.

Managing inland fisheries

The post-impoundment bio-ecology of fish fauna, aquatic macrophytes and aquatic birds of Kainji Lake are discussed.
Echinochloa stagnina was the dominant species of the aquatic macrophytes, and was used as livestock fodder during the dry season.
Fish processing, marketing and distribution in the lake basin have improved, while the management and development of the fisheries are still at research and planning levels.
For Kariba, research and fisheries development activities since 1984 are reported. Research focuses on problems related to the pelagic fishery between Zambia and Zimbabwe that lands 30 000 t annually, warranting an effort to manage the fishery efficiently. A joint Zambia/Zimbabwe SADC Fisheries Project is currently operational, and includes a stock assessment group.
Management of the inshore areas is being re-organized through giving resource rights to the fishing communities and hence an incentive to exploit the resource in a sustainable manner.
Basic research, focusing on an increased understanding of the ecosystem, continues. The ecosystem is beginning to stabilize and changes in populations are becoming predictable.
The Aswan High Dam Lake consists of Lake Nasser in Egypt and Lake Nubia in Sudan. Its main purposes since 1964 have been power generation and irrigation.
Seasonal fluctuations of a number of physico-chemical parameters are presented, while phytoplankton composition in 1988 is compared with that in 1976 and 1979. Data on fish biology are given for the main commercial species.
Fish landings decreased from 34 000 t in 1981 to 15 700 t in 1989, but increased again to 21 900 t in 1990 and to 30 800 t in 1991. Tilapias are 89% of total landings. Salted fish production decreased from 57% of the total landings in the early years of impoundment to less than 10% in 1990.
In recent years, the income of fishermen has increased, mainly because of rapidly increasing fish prices.
For Lake Volta, no significant limnological changes have been reported, but an influx of fishermen has led to overexploitation. The main food source of the fish stocks -periphyton attached to submerged trees - is threatened as, during drawdown periods, the trees are increasingly cut to meet increased demand for fuelwood, especially for smoking.
The estimated total yield (36 360 t in 1991) is close to the long-term yield of 40 000 t/year, but fishing effort has increased four-fold in two decades. New fishing techniques, including semi-mechanized purse seining and beach seining, are aggravating the overfishing. Although many of these new methods are prohibited, there is no effective control.