Nile Perch - Lake Victoria Introduction

Lake Victoria Introduction

The introduction of this species to Lake Victoria is one of the most commonly cited examples of the negative effects invasive alien species can have on ecosystems.

The Nile perch was introduced to Lake Victoria in East Africa in the 1950s, and has since been fished commercially. It is attributed with causing the extinction or near-extinction of several hundred native species, but as Nile perch stocks decrease due to commercial fishing, at least some of them are making a comeback. Initially, the Nile perch's diet consisted of native cichlids, but with decreasing availability of this prey, it now consumes mainly small shrimp and minnows.

The fish's introduction to Lake Victoria, while ecologically negative, has stimulated the establishment of large fishing companies there. In 2003, Nile perch earned 169 million euro in sales to the EU. Another income is the sportfishing tourism in the region of Uganda and Tanzania which aim to catch this fish. The long-term outlook is less clear, as overfishing is now reducing L. niloticus populations.

The alteration of the native ecosystem has also had disruptive socioeconomic effects on local communities bordering the lake. Large-scale fishing operations, while earning millions of dollars from their exported L. niloticus catch, have displaced many local people from their traditional occupations in the fishing trade and brought them into the cash economy or - before the establishment of export-oriented fisheries - turned them into economic refugees. At least initially, nets strong enough to hold adult Nile perch could not be manufactured locally and had to be imported for a high price.

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 Academy Award-nominated documentary Darwin's Nightmare by Hubert Sauper (a French-Austrian-Belgian production, 2004) deals with the damage that has been caused by Nile Perch introduction, including the import of weapons and ammunition in cargo planes from Europe that then export Nile perch, exacerbating conflict and misery in the surrounding regions. Darwin's Nightmare is highly controversial, however, to those who consider the introduction of Nile perch beneficial. They accuse the documentary of implying causalities that do not actually exist. Even critics of the introduction have not praised the focus on spectacular but only loosely correlated recent issues, to the neglect of the actual ecologic and economic upheaval caused by L. niloticus proliferation in Lake Victoria.

Regardless of opinion, the trophic web of Lake Victoria appears to have been drastically altered through the introduction of this novel near-top-level predator. While the lake ecosystem is slowly moving towards a new equilibrium, the former state of fisheries on Lake Victoria probably cannot be brought back, regardless of whether this is considered positive or negative.