Lake Victoria is Africa’s largest lake – and home to one of the world’s largest freshwater fish. The man-sized Nile perch can grow to around 2 m (over 6 ft) and slam the scales down to 200 kg (530 lb). But Lates niloticus is no native, and debate raged in the 1950s with one side promoting the introduction of Nile perch for commercial reasons and the other issuing dire warnings that such a move would decimate one of the world’s most diverse fish environments.
The ‘pro’ lobby triumphed, but not by winning the argument. Nile perch were surreptitiously slipped into Lake Victoria from Uganda around 1954, so the genie was already out of the bottle when official introductions followed in 1962 and 1963. But did this prove disastrous, as naysayers predicted?
In fact, both sides were right. Once established, the Nile perch of Lake Victoria made a massive contribution to the economies of three countries, supporting not only 150,000 fishermen but also those working in related industries like processing and transport. On the other hand, the fierce new predator decimated original fish stocks with negative consequences for the area’s traditional fishing communities. Whatever view is taken, everyone agrees that the introduction is a classic example of the negative impact aliens can have on an established ecosystem.
And the spectacular commercial success of the Lake Victoria fishery may not last. Over-fishing is dramatically reducing Nile perch stocks, and the good times could be coming to an end. Just as cow pasture ploughed to grow arable crops produces spectacular initial yields that drop away as the natural fertilizer is exhausted, so the boom years for fishermen on Lake Victoria may be coming to an end as the bill for meddling with Nature is presented.
When: Early 1950s and early 1960s
Where: Lake Victoria, Uganda/Kenya/Tanzania
Death toll: Countless millions of native fish, with many of Lake Victoria’s 500 species vanishing altogether.
You should know: Sometimes, painful eco-lessons do get learned. The Australian state of Queensland – having suffered mightily following the introduction of cane toads in the 1930s – has made it a serious offence to be found in possession of a five Nile perch, it is thought that – should the dominant predator become established in local waters – it would swiftly decimate the popular native barramundi, a similar but smaller fish.