The African Great Lakes
Case Study : Lake Malawi

The lake is bordered and shared by three countries: Malawi, Tanzania and Mozambique and is known as Lake Malawi, Lake Nyasa, or Lake Niassa in each country respectively. Lake Malawi is the southernmost of the Western Rift Valley lakes of East Africa and is renowned for its remarkable fish fauna. It is partially due to the unique faunal characteristics of the lake that international attention has been engaged in its conservation and management. There have been various estimates of between 500 and 1000 species of the family Cichlidae living in Lake Malawi, many of which are yet to be scientifically described. The lake is also the source of over 70% of the animal protein (as fish) available to the people of Malawi.

This ultraoligotrophic lake extends almost 600 km in length with a maximum depth of over 700 m. Evaporation and precipitation dominate the hydrology of the lake, although several rivers flow into the lake and there is only one outflow through the Shire R iver to the south. Phosphorus and nitrogen are added to the lake in approximately equal amounts through precipitation and the particulate material of river discharge. Increased deforestation due to growth in agriculture and the population in the southern part of the lake catchment may produce significant changes to the lake chemistry. Thus there is growing concern about the possible eutrophication of Lake Malawi. This has produced many questions concerning the possible changes in fish habitat and human health. Ongoing studies continue to examine the consequences to fish biodiversity, lake chemistry, and lake production by changes in and around the lake. Also of importance to human health is the presence of bilharzia, which is currently the focus of research by Danish investigators.

Because the lake is ultraoligotrophic, the clarity is exceptional, especially during the dry season. The shoreline is predominated by long sandy be aches and rocky outcrops. Hippopotamus and crocodile are often seen in some of the near shore wetlands and river mouths and are easily sighted in Liwonde National Park on the Shire River.

An introduction to Lake Malawi and its fish can be found in Brian Moss's book, Ecology of Freshwaters.

Detailed article on Lake Malawi and its Cichlids with map and photos written from the point of view of an aquarist

Article on human population problems resulting in pressure on Malawi fish populations

Speciation in rapidly diverging systems: lessons from Lake Malawi
A modern research article on the diversity of Malawi cichlids (needs Adobe acrobat installed)

Biogeography and population genetics of the Lake Malawi cichlid Melanochromis auratus : habitat transience, philopatry and speciation. A modern research article on the diversity of Malawi cichlids (needs Adobe acrobat installed)