There are around 500 species of fish in Lake Malawi. Most of these are of the family Cichlidae – the largest family of fish in Africa – and 99% of these cichlids are endemic to the lake. Chambo , familiar to anyone who has eaten in a restaurant in Malawi, are one type of cichlid. Others include the small utaka, which move in big shoals and are caught by fisherman at night. But Lake Malawi is most famous for the small and colourful mbuna , of which there are many species. As well as being attractive to snorkellers and divers, mbuna are popular with aquariums and for scientists they provide a fascinating insight into the process of evolution. Mbuna identification and classification is an ongoing process and it is thought that many species of mbuna remain undiscovered.
Cichlids have evolved over the millennia from one common species into many hundreds, yet they have continued to coexist. This has been achieved by different species developing different ways of feeding. Chambo eat phytoplankton, which they filter out of the water through their mouths, whereas mbuna have different methods of feeding. Some have developed special teeth to help them scrape algae off the rocks; there are also ‘snail eaters’ with strong flat teeth, perfect for crushing shells; and ‘sand diggers’, which filter insects and small animals out of the sand.
Also interesting is the cichlid breeding process. The male attracts the female with his bright colours, and if suitably impressed, she lays eggs, which she immediately takes in her mouth for protection. The male has a pattern near his tale resembling the eggs, which the female tries to pick up, at which point the male releases his sperm into the water, which the female invariably inhales. This process is repeated until all or most of the eggs are fertilised. The female keeps the eggs in her mouth and when they become baby fish, they stay there for protection. They emerge only to feed, but at the slightest sign of danger, the mother opens her mouth and the young swim straight back in.