4. FISHERY RESOURCES OF THE LARGER AND DEEPER LACUSTRINE SYSTEMS

The distinguishing characteristics of the large and the deep lakes are the following:

1. Lakes Tanganyika and Malawi are very deep lakes with de-oxygenated bottoms and with much of their endemic fauna somewhat still intact. The two lakes are still dominated by the cichlids, most of which are endemic (see Table 2).

2. Lake Victoria is relatively shallow (maximum depth 79 m, mean depth 40 m). It has higher fish yields per unit area than Lakes Malawi and Tanganyika. The original endemic haplochromine and tilapiine cichlids have changed. Its fisheries now depend on the introduced Nile perch and the Nile tilapia (Oreochromis niloticus) as well as on the indigenous pelagic cyprinid - Rastrineobola argentea (dagaa). Lake Victoria, has now a very much disrupted food web system. Many haplochromine zooplankton feeders and molluscs eaters have declined. Hence, here are abundant lake flies and possibly Rastrineobola has also benefited from the decline of Haplochromis and other insectivores.

3. Lake Kivu is fairly small (583 km²) and deep (maximum depth 489 m, mean depth 240 m) with a de-oxygenated layer. Its fishery depends on the introduced clupeid fish. Its annual fish yield per unit area is not exactly known;

4. Lake Edward (elsewhere known as Idi Amin) is large (2325 km²) and somewhat deep (117 m maximum and 34 m mean depth). This lake is characterized by nilotic fauna.

5. Lake Mobutu Sese Seko (or Albert) is relatively shallow (58 m maximum depth, 25 m mean depth). It also has a nilotic fauna: and

6. Lake Turkana (formerly Rudolf) has an area of 7200km² and maximum depth of 120 m. The lake has a nilotic fauna and a relatively low productivity level (22 kg/ha).

Table 1 : Indices of Fish Production for Various Lakes in Eastern and Central Africa

¹ Salinity scale
very low - with conductivity less than 100 μ mhos
low - with conductivity 100<500 μ mhos
medium - with conductivity 500>3,000 μ mhos
high - with conductivity more than 3,000 μ mhos

² MEI = Morpho-edaphic Index = conductivity/mean depth

Table 2: Physical Characteristics and Fish Production for Seven African Great Lakes

Note: Location of most of the lakes referred to in Tables 1, 2 and 3 are indicated in Figure 1 (a sketch map of riverine and lacustrine systems of East and Central Africa)

Figure 1: Sketch map showing rivers and lakes of East and Central Africa.

Table 3: Comparative estimated catches and potential yields of seven African Great Lakes