Lake Malawi is the southernmost of the Rift Valley Lakes. Its tropical setting
maintains a permanent thermal stratification. Surface waters are oxygenated, but
oxygen decreases with depth so that anoxic waters are a permanent feature below about
200 m depth. Although the tectonic activities which formed the lake basin originally
date back to the Miocene, the lake is believed to have had roughly its present
form for approximately two million years. It is the fourth deepest and the ninth largest
lake in the world. There are more species of fish in Lake Malawi than in any other lake.
Nearly all of these fishes are endemic, indicating that speciation took place in the
lake. As in the other African Great Lakes the cichlid species flocks are numerically
dominant. The lake and its fishes are vital to riparian communities and every
effort should be made to conserve Lake Malawi.