River or lake, Tanzania
Lake Tanganyika
The world's longest freshwater lake and second deepest, with ancient cichlids and a sardine fishery.
Lake Tanganyika is about 670 km long, the longest freshwater lake in the world, and reaches about 1,470 metres deep, second only to Lake Baikal. It is shared by Tanzania, the Democratic Republic of the Congo, Burundi and Zambia. Millions of years old, it holds around 250 species of cichlids, many of them older lineages than those of Lake Malawi and Lake Victoria.
Cichlids of every shape
Tanganyika's cichlids have evolved into a wide range of forms. Some live and breed inside empty snail shells, others form large colonies in which older young help raise their siblings. The frontosa, a large blue-and-white banded cichlid of deep rocky slopes, and the Tropheus species of the shallows are prized by aquarists. Most species are found nowhere else.
Sardines and lates
The open water supports a fishery for two small sardines, called dagaa or kapenta, and for four species of lates, relatives of the Nile perch, which hunt them. Fishers work at night with lamps to draw the sardines. The lake has warmed over the past century, and studies suggest this has weakened the mixing of nutrients and reduced fish production, while fishing pressure has grown. The deep water below about 200 metres has no oxygen and no fish.
Still to be written: Lake Tanganyika sardine, Sleek lates, Cyphotilapia frontosa, Tropheus moorii, Neolamprologus brichardi.