The Nile perch (Lates niloticus) is a species of freshwater fish in family Centropomidae of order Perciformes. It is widespread throughout much of the Afrotropic ecozone, being native to the Lake Chad, Congo, Nile, Senegal, Volta, and other river basins. It also occurs in the brackish waters of Lake Maryut in Egypt.

L. niloticus is silver in colour with a blue tinge. It has a distinctive dark black eye, with a bright yellow outer ring. One of the largest freshwater fishes, it reaches a maximum length of nearly two metres (more than six feet), weighing up to 200 kg (440 lb).

Adult Nile perch occupy all habitats of a lake with sufficient oxygen concentrations, while juveniles are restricted to shallow and/or nearshore environments. A fierce predator that dominates its surroundings, the Nile perch feeds on fish (including its own species), crustaceans, and insects; the juveniles also feed on zooplankton.

Nile perch have been introduced to many other lakes in Africa, including Lake Victoria (see below). The IUCN's Invasive Species Specialist Group considers L. niloticus one of the world's 100 worst invasive species.

The species is of great commercial importance as a food fish. The Nile perch is also popular with sport anglers and is raised in aquaculture.

Originally classified as Labrus niloticus, among the marine wrasses, the species is also known as the African snook and by a large number of local names in various African languages.

Lake Victoria introduction

The Nile perch was introduced to Lake Victoria, one of the Rift Valley lakes in eastern Africa, in the 1960s, where it is fished commercially and has had a catastrophic effect on local fishes, causing the extinction of several hundred native species. Among the Lake Victoria population, 95 percent of the Nile perch's diet consists of native cichlids, at least half of whose species have been extirpated.

The fish's introduction to Lake Victoria, while ecologically catastrophic, has been of short-term benefit to large fishing companies there. The long-term benefit is less clear, as overfishing is now reducing L. niloticus populations there.

The alteration of the native ecosystem has also had disruptive socioeconomic effects on local communities in the countries 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.

In addition, the Nile perch's flesh, being oilier than that of the native fish species, is more difficult to dry. Consequently, the increased demand for firewood to dry the catch has contributed to deforestation of the surrounding region, resulting in pollution of the lake by runoff.

The introduction of this species to Lake Victoria is one of the most commonly cited examples of the negative effects alien species can have on ecosystems and on the human populations which depend on them.

Movie

The Darwin's Nightmare is a documentary of Hubert Sauper (a French-Austrian-Belgian production, 2004). It illustrates all the damages that have been provoked by Nile Perch introduction.

References

• IUCN. "Alien Species Invade the Planet". Press release, 11 May 2001.
• Lipton, David. "Lates niloticus: Information". Animal Diversity Web. Ann Arbor: University of Michigan Museum of Zoology, 2003.
• Snoeks, Jos. "Ecology of Lates niloticus". Global Invasive Species Database. Updated 22 September 2004.