Lake Victoria is 69,000 square kilometres in size, making it the largest lake in Africa, the largest tropical lake in the world, and the second largest freshwater lake in the world. It is the source of the White Nile (the longer branch of the Nile). It is also an extremely sick ecosystem. During the 1950s, the nile perch (Lates niloticus) was introduced into the lake's ecosystem in an attempt to improve the yields of fishing in the lake. The nile perch proved totally devastating to the local ecosystem - of the hundreds of endemic species, many are now extinct. Further, the initial good returns on nile perch catches has diminished dramatically.