June 16th 2016
As my colleague Dan highlighted last week, we in the UK don’t have the worst problems in the world with invasive species. Japanese knotweed and the Killer Shrimp are causing havoc – but we wouldn’t go so far as to say devastation (although in the case of the Killer Shrimp, this is mostly because their spread is currently, thankfully, limited).
Few of the documented cases of damage from invasive species are as bad as those at Lake Victoria – where the introduction of the Nile Perch caused the extinction, or near-extinction of hundreds of native marine species.
Straddling three countries, Lake Victoria is by some margin the largest lake in Africa, and is one of the largest lakes in the world. It has been documented since the 12th century, and its shores have become densely populated.
The non-native fish species known as ‘Nile perch’ was introduced to the lake in the 1950s to be fished commercially. The Nile perch prey on many of the cichlids (a species of fish), shrimp and minnows in the lake. Many of the native cichlid species are now extinct or nearing extinction.
“The introduction of Nile perch has also had additional ecological effects on shore. Native cichlids were traditionally sun-dried, but Nile perch have a higher fat content than cichlids so instead need to be smoked to avoid spoiling. This has led to an increased demand for firewood in a region already hard-hit by deforestation, soil erosion and desertification.”
The lake also has a significant infestation of water hyacinth, which causes problems for fishing boat access, provides a breeding ground for mosquitos which spread disease, de-oxygenates water, causing problems for native species and has even blocked the intakes of a hydro-electric plant, causing electrical blackouts.
So on the whole, Lake Victoria hasn’t done so well out of the invasive species that we have introduced.