Mali has three reservoirs for irrigation, power generation and flood control. The Markala dam was built on the Niger River, mainly for water flow regulation, in 1946. The Sélingué dam has created a reservoir near the capital, Bamako. This dam was constructed on the Sankarani River for electrical power production, flow control and irrigation. The largest of the three, the Manantali Reservoir, was installed on the Bafing River for power generation and irrigation (Vanden Bossche and Bernacsek, 1991). This chapter deals with the two latter ones. Their geographic positions are presented in Figure 4.1.
The Bafing River has its source in the Fouta Djallon in Guinea; it is the inflowing as well as the outflowing river of the Manantali Reservoir at approximately 350 km west of Bamako. At the confluence of the Bafing (major tributary) and Bakoye Rivers the Senegal River originates (Vanden Bossche and Bernacsek, 1991). The shape of the reservoir is presented in Figure 4.2 (after Anne et al., in press).
Lelek and Tobias (1982 and 1985) carried out some investigations prior to the construction of the dam. Limnological data are presented in Table 4.1. Major fish species occurring in the Bafing River prior to damming, were four species of cichlids, Chrysichthys and Synodontis (after Anne et al., in press).
The Manantali Reservoir has a surface area of about 600 km2, a volume of 12 km3, a mean depth between 20 and 25 m. The irrigation area is 5 000 km2 and the electrical power capacity is of the order of 800 MW (Vanden Bossche and Bernacsek, 1990b). Anne et al. (in press) provided more detailed information on the characteristics of the lake. The filling started in July 1987 and the lake's maximum surface area is 457 km2, its maximum depth 55 m and its mean depth 23.8 m. The sequential filling of the lake is presented in Figure 4.3.
Deceuninck (1989) presented a general description of the fisheries in the waters of Mali. Fishing operations are carried out from planked or dugout canoes. Main gear used are castnet, gillnet, seines, longline, harpoon, trap and weir. No specifications were given for the Manantali Reservoir. Anne et al. (in press) reported that before the construction of the dam seasonal fishing was carried out in the Manantali region by nomadic fishermen, at the end of the dry season. After the damming, when filling of the lake started, hundreds of fishermen were attracted to the lake. In November 1989 the number of fishermen exceeded 400, while the number of boats was just over 200. Regular frame surveys in 1990, 1991 and 1992 shows that the number of fishermen was little less than 400 and remained stable, as did the number of boats (Anne et al., in press). Frame survey results are presented in Figure 4.4.
18.104.22.168 Annual yield
Welcomme (1979) estimated the potential annual yield at 2 000–3 000 t. An average yield of 150 kg/ha/yr was applied by CILSS (1977) and Deceuninck (1989), which then resulted in a total of 9 000 t/yr. Crul (1992) estimated the potential annual yield at 2 992 t, based on revised yield prediction models. Anne et al. (in press) estimated the fish yield at 27 kg/ha in 1989, which then dropped to 17 kg/ha in 1990. In 1991 and 1992 yields were of the order of 26 and 27 kg/ha respectively. This yield would indicate a total annual production of around 1 200 t. There is likely some scope for increase of total production in light of estimates by Welcomme and Crul. However, the figures applied by Deceuninck and CILSS seem to be overestimated.
22.214.171.124 Catch rates
No data available.
126.96.36.199 Fishing effort
No data available.
188.8.131.52 Mesh selectivity
No data available.
184.108.40.206 Species composition of catches
Before damming, four species of cichlids, Chrysichthys and Synodontis occurred in the river; immediately after the construction of the dam fish catches also consisted of species of the genera Clarias, Distichodus and Citharinus (Anne et al., in press). Detailed analyses of faunistic changes in the lake are in preparation.
Anne et al. (in press) observed differences in species composition of experimental catches in areas where bush clearance had taken place and where the (uncleared) savannah vegetation had been flooded (Figure 4.5).
220.127.116.11 Small clupeids and other small pelagics
The presence of a pelagic cyprinid (Leptocypris (Barilius) niloticus) was reported by Anne et al. (in press). This species is not yet fished; its abundance and ecology are under investigation.
No information available to the author.
The Sankarani River has its origin in Guinea; it is the inflowing as well as the outflowing river of the Sélingué Reservoir and discharges to the Niger River. The dam, located at Kangare, was closed on 6 July 1980. The shape of the reservoir is presented in Figure 4.6 (Anne et al., in press).
No data available; however, reportedly Lelek and Tobias (1982 and 1985) carried out investigations.
The Sélingué dam has created a reservoir of 409 km2 at 160 km from the capital of Bamako, at an altitude of 348.5 m above sea level at Full Supply Level. The maximum depth is about 20 m and its mean is 5.3 m. The total volume has been calculated at 2 166 km3. The temperature range is 26.0–31.4°C, the conductivity 31.6 μS/cm and the pH range is 6.3–7.05 (Vanden Bossche and Bernacsek, 1991). The electrical power capacity is of the order of 200 MW and the irrigation area is around 550 km2 (CILSS, 1977).
A more precise figure (23.8 m) of the mean depth was presented by Anne et al. (in press), who mentioned that the water influx into the lake is steady and that the lake is intermittently fed by the Balé stream.
Kanta (1989) observed the lowest water level since the lake had filled up entirely. The highest level was measured in October 1988: 348.644 m above sea level. In June 1989 the level had dropped to 339.983 m.
Deceuninck (1989) presented a general description of the fisheries in the waters of Mali. Fishing operations are carried out from planked or dugout canoes. Main gear used are castnet, gillnet, seines, longline, harpoon, trap and weir. No specifications were given for the Sélingué Reservoir.
Deceuninck did not give any specifications for the Sélingué Reservoir. Kanta (1989) estimated the total number of fishermen between 1300 and 1500, inhabiting 40 fishing camps. He summarized the information available on the origin of the fishermen. About 47% of the fishermen would be from the Segou area, 45% from Mopti, 3% from Koulikoro, 4.3% from Tombouctou, and 0.7% from Sikasso, Bamako and Gao. The ethnic background of the fishermen was as follows: 78% Bozos, 25.2% Somonos, 1.9% Sonrhaï and 4.7% Rimaïbé, Bella, Bambara and Sarakollé. Main gears used were gillnet, trap, seine and longline.
18.104.22.168 Annual yield
Welcomme (1979) estimated the potential annual yield at 2 000–3 000 t. An average yield of 150 kg/ha/yr was applied by CILSS (1977) and Deceuninck (1989) which then resulted in a total of 6 000 t/yr. Crul (1992) estimated the potential annual yield at 2 103 t, based on revised yield prediction models. Kanta (1989) quoted the figure of 2100 t/year at the initial phase and 1500 t/year in a stable situation. The average annual yield would be of the order of 50 kg/ha/year. Available catch statistics are as follows: 1431 tonnes of fish in 1984; this production figure dropped to 1100 t in 1985 due to severe drought in 1984. In 1986 the total annual catch was estimated at 1515 t and at 1472 and 1278 t in 1987 and 1988 respectively (Kanta, 1989). Anne et al. (in press) reported a sustained yield of 40 kg/ha/yr. Taking into account the surface of the lake the total annual yield would be around 1 650 t, well below the existing estimates. This would imply that there is scope for development of the fishery to some extent, especially when the unexploited small pelagics will become subject to fishing.
22.214.171.124 Catch rates
No data available.
126.96.36.199 Fishing effort
As stated above the number of fishermen was estimated between 1300 and 1500 (Kanta, 1989).
188.8.131.52 Mesh selectivity
No data available.
184.108.40.206 Species composition of catches
Kanta (1989) stated that 52 fish species were recorded to be caught in Sélingué Reservoir of which representatives of the following families predominated in the catches: Bagridae, Characidae, Chichlidae, Citharinidae, Clariidae, Cyprinidae, Centropomidae, Gymnarchidae, Malapteruridae, Mochokidae, Mormyridae, Osteoglossidae, Polypteridae and Schilbeidae.
220.127.116.11 Small clupeids
It was reported by Anne et al. (in press) that small clupeids occur in the Sélingué Lake. No scientific or vernacular name was reported. Up to 1992 the resource was untapped.
Some recommendations had been put forward by Kanta (1989). He recommended the establishment of a fisheries council as well as closed areas during the spawning seasons of various species. He also recommended the application of fisheries regulations involving the fishermen, non-fishing local communities and the competent local authorities.