The
Nile perch is a
speciesIn biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of
freshwaterFresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
fishFish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
in
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
LatidaeThe Latidae are a family of perch-like fishes found in Africa and the Indian and Pacific Oceans. The family, previously classified subfamily Latinae in family Centropomidae, was raised to family status in 2004 after a cladistic analysis showed the original Centropomidae was paraphyletic.Many...
of
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
PerciformesThe Perciformes, also called the Percomorphi or Acanthopteri, is one of the largest orders of vertebrates, containing about 40% of all bony fish. Perciformes means perch-like. They belong to the class of ray-finned fish and comprise over 7,000 species found in almost all aquatic environments...
. It is widespread throughout much
of the
AfrotropicThe Afrotropic is one of the Earth's eight ecozones. It includes Africa south of the Sahara Desert, the southern and eastern fringes of the Arabian Peninsula, the island of Madagascar, southern Iran and extreme southwestern Pakistan, and the islands of the western Indian Ocean. It was formerly...
ecozoneAn ecozone is the broadest biogeographic division of the Earth's land surface, based on distributional patterns of terrestrial organisms.Ecozones delineate large areas of the Earth's surface within which organisms have been evolving in relative isolation over long periods of time, separated from...
, being native to the
CongoThe Congo River is a river in Africa, and is the deepest river in the world, with measured depths in excess of . It is the second largest river in the world by volume of water discharged, though it has only one-fifth the volume of the world's largest river, the Amazon...
, Nile,
SenegalThe Sénégal River is a long river in West Africa that forms the border between Senegal and Mauritania.The Sénégal's headwaters are the Semefé and Bafing rivers which both originate in Guinea; they form a small part of the Guinean-Malian border before coming together at Bafoulabé in Mali...
,
NigerThe Niger River is the principal river of western Africa, extending about . Its drainage basin is in area. Its source is in the Guinea Highlands in southeastern Guinea...
, and
Lake ChadLake Chad is a historically large, shallow, endorheic lake in Africa, whose size has varied over the centuries. According to the Global Resource Information Database of the United Nations Environment Programme, it shrank as much as 95% from about 1963 to 1998; yet it also states that "the 2007 ...
,
VoltaLake Volta is the largest reservoir by surface area in the world, and the fourth largest one by water volume. It is located completely within the country of Ghana, and it has a surface area of about 8,502 km² . Lake Volta lies along the Greenwich Meridian, and just six degrees of latitude...
,
Lake TurkanaLake Turkana , formerly known as Lake Rudolf, is a lake in the Great Rift Valley in Kenya, with its far northern end crossing into Ethiopia. It is the world's largest permanent desert lake and the world's largest alkaline lake...
and other river basins. It also occurs in the brackish waters of Lake Maryut in
EgyptEgypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
. Originally described as
Labrus niloticus, among the
marineSeawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...
wrasseThe wrasses are a family, Labridae, of marine fish, many of which are brightly colored. The family is large and diverse, with over 600 species in 82 genera, which are divided into nine subgroups or tribes....
s, the species has also been referred to as
Centropomus niloticus. Common names include
African snook,
Capitaine,
Victoria perch (a misleading trade name, as the species is not native to
Lake VictoriaLake Victoria is one of the African Great Lakes. The lake was named for Queen Victoria of the United Kingdom, by John Hanning Speke, the first European to discover this lake....
), and a large number of local names in various African languages, such as the
LuoThe Nilotic Luo languages, or Lwoian, are a dozen languages spoken by the Luo peoples in an area ranging from southern Sudan via Uganda to southern Kenya, with Dholuo extending into northern Tanzania and Alur into the Democratic Republic of the Congo. They form one of the two branches of Western...
name
Mbuta.
Lates 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 fish, it reaches a maximum length of nearly two metres (more than six feet), weighing up to 200 kg (440
lbThe pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...
). Mature fish average 121–137 cm (48–54 in), although many fish are caught before they can grow this large.
Adult Nile perch occupy all habitats of a lake with sufficient
oxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
concentrations, while juveniles are restricted to shallow or nearshore environments. A fierce predator that dominates its surroundings, the Nile perch feeds on
fishFish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
(including its own species), crustaceans, and
insectInsects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s; the juveniles also feed on
zooplanktonZooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
.
Nile perch have been introduced to many other lakes in Africa, including
Lake VictoriaLake Victoria is one of the African Great Lakes. The lake was named for Queen Victoria of the United Kingdom, by John Hanning Speke, the first European to discover this lake....
(see below) and the artificial
Lake NasserLake Nasser is a vast reservoir in southern Egypt, and northern Sudan, and is one of the largest man-made lakes in the world. Strictly, "Lake Nasser" refers only to the much larger portion of the lake that is in Egyptian territory , with the Sudanese preferring to call their smaller body of water...
. The IUCN's (World Conservation Union) Invasive Species Specialist Group considers
Lates niloticus one of the world's 100 worst invasive species.
The state of
QueenslandQueensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
in Australia levies heavy fines on anyone found in possession of a living Nile perch, since it competes directly with the native
BarramundiThe Barramundi , also known as Asian Seabass, is a species of catadromous fish in family Latidae of order Perciformes. The native species is widely distributed in the Indo-West Pacific region from the Persian Gulf, through Southeast Asia to Papua New Guinea and Northern Australia. Known in Thai...
, which is similar but does not reach the same size as the
Nile perch.
The species is of great commercial importance as a food fish. The Nile perch is also popular with sport
anglersFishing is the activity of trying to catch wild fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....
as it attacks artificial
fishing lureA fishing lure is an object attached to the end of a fishing line which is designed to resemble and move like the prey of a fish. The purpose of the lure is to use movement, vibration, and colour to catch the fish's attention so it bites the hook...
s and is also raised in
aquacultureAquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...
.
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
introducedAn introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
to
Lake VictoriaLake Victoria is one of the African Great Lakes. The lake was named for Queen Victoria of the United Kingdom, by John Hanning Speke, the first European to discover this lake....
in
East AfricaEast Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
in the 1950s, and since then it has been fished commercially. It is attributed with causing the extinction or near-
extinctionIn biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
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
cichlidCichlids are fishes from the family Cichlidae in the order Perciformes. Cichlids are members of a group known as the Labroidei along with the wrasses , damselfish , and surfperches . This family is both large and diverse. At least 1,300 species have been scientifically described, making it one of...
s, 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
Lates 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
Lates 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 (see for a critique on this view Beuving 2010). 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
deforestationDeforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....
, soil erosion and
desertificationDesertification is the degradation of land in drylands. Caused by a variety of factors, such as climate change and human activities, desertification is one of the most significant global environmental problems.-Definitions:...
.
The
Academy AwardAn Academy Award, also known as an Oscar, is an accolade bestowed by the American Academy of Motion Picture Arts and Sciences to recognize excellence of professionals in the film industry, including directors, actors, and writers...
-nominated documentary
Darwin's NightmareDarwin's Nightmare is a 2004 French-Belgian-Austrian documentary film written and directed by Hubert Sauper, dealing with the environmental and social effects of the fishing industry around Lake Victoria in Tanzania. It premiered at the 2004 Venice Film Festival, and was nominated for the 2006...
by
Hubert SauperHubert Sauper is a documentary filmmaker best known for the highly controversial Darwin's Nightmare which was nominated for an Academy Award....
(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
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
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, it appears that the trophic web of Lake Victoria has 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.
See also
- Nile tilapia - a different fish, which also belongs to the Perciformes
The Perciformes, also called the Percomorphi or Acanthopteri, is one of the largest orders of vertebrates, containing about 40% of all bony fish. Perciformes means perch-like. They belong to the class of ray-finned fish and comprise over 7,000 species found in almost all aquatic environments...
, or perch-like fish.