Africa's largest lake was once a biologist's dream pond, offering rare glimpses into vertebrate speciation and the dynamics of sexual versus natural selection, via the hundreds of endemic and often highly colourful cichlids that danced in its waters. Following the introduction of the Nile perch, a two metre long predatory fish that some people thought would make good sport, the barely ploughed depths of the lake's biodiversity was soon reduced to a dismal dump of alien cannibals, as the perch began to feed on alternate foods such as prawns and on each other, having exhausted the lineages of hundreds of cichlid species. Not surprisingly, midge populations along the lake's coasts exploded, as few small fish were left to consume insect larvae.
"Within a single decade," writes Dutch biologist Tijs Goldschmidt, who studied this community in the 1980s, "the differentiated biotic community that had coevolved over a period of at least fourteen thousand years, and perhaps even hundreds of thousands of years, had changed into an impoverished mess."
The Nile perch is now an ineradicable feature of Lake Victoria, a fitting tribute to the indiscriminate pride of men whose folly overruled their freedom. Nearby, the shore-dwellers of Tanganyika and Malawi have mercifully discovered the livelihoods afforded in catching their technicolour cichlids for export to aquarists. Here, at least, a handful of small fish are being truly transformed into a breadbasket that feeds a multitude.