- Lake Malawi (Nyasa)
- 1,000 total number
- Malawi ()
Bordered by Malawi, Tanzania and Mozambique in eastern Africa, the lake with most fish species is Lake Malawi (aka Nyasa). It contains at least 700 species of cichlid (some ichthyologists claim as many as 1,000 – cichlid classification is notoriously complicated), all but four of which are endemic, as well as a number of additional endemic fish species. These latter include various catfishes, mormyrids, tetras, cyprinids and eels. The cichlids present here are divided into two main taxonomic groups – the haplochromines (all but six of Lake Malawi's endemic cichlid species belong to this group) and the tilapines. Also present, however, is the invasive, non-indigenous Nile tilapia (Oreochromis niloticus), which is seen as a grave threat to this lake's exceptionally rich, unique biodiversity, because it is known for out-competing other tilapines.
With a maximum depth of 706 m (2,316 ft), Lake Malawi is Africa's second-deepest lake (after the 1,460-m/4,790-ft Lake Tanganyika), and with a surface area of 29,544 km2 (11,407 sq mi) it is Africa's third largest. Overall, it is the ninth-largest lake in the world by area and the fifth-largest freshwater lake by volume (it contains 8,400 km3/2,015 cu mi of water), all of which provides ample space for vast quantities of fish, both numerically and taxonomically.
Moreover, analysis of its sediment levels spanning 1.3 million years have revealed that during this period the lake's water levels dropped by more than 200 m (660 ft) around 24 times. Such dramatic changes to the habitats provided by the lake would have forced its fish species to diversify in order to survive, thus explaining its remarkably high number of endemics.