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Datasheet

Lates niloticus
(Nile perch)

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Datasheet

Lates niloticus (Nile perch)

Summary

  • Last modified
  • 06 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Natural Enemy
  • Host Animal
  • Preferred Scientific Name
  • Lates niloticus
  • Preferred Common Name
  • Nile perch
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Chordata
  •       Subphylum: Vertebrata
  •         Class: Actinopterygii
  • Summary of Invasiveness
  • L. niloticus is a large perch-like predator that is native and widespread in parts of Africa, mainly above the equator (Fro...

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Pictures

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PictureTitleCaptionCopyright
Lates niloticus, the Nile Perch, showing part of a catch; February 1984 in the the Nyanza Gulf, Kenya.
TitleNile Perch
CaptionLates niloticus, the Nile Perch, showing part of a catch; February 1984 in the the Nyanza Gulf, Kenya.
CopyrightFrans Witte
Lates niloticus, the Nile Perch, showing part of a catch; February 1984 in the the Nyanza Gulf, Kenya.
Nile PerchLates niloticus, the Nile Perch, showing part of a catch; February 1984 in the the Nyanza Gulf, Kenya.Frans Witte

Identity

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Preferred Scientific Name

  • Lates niloticus (Linnaeus, 1758)

Preferred Common Name

  • Nile perch

Other Scientific Names

  • Centropomus niloticus (Linnaeus, 1758)
  • Labrus niloticus Linnaeus, 1758
  • Lates albertianus Worthington, 1929
  • Lates niloticus albertianus Worthington, 1929
  • Lates niloticus macrolepidota Pellegrin, 1922
  • Lates niloticus macrolepidotus Pellegrin, 1922
  • Lates nilotus rudolfianus Worthington, 1932

International Common Names

  • English: African snook; Victoria perch
  • Spanish: perca del Nilo
  • French: perche du Nil
  • Arabic: am'kal; am'kaltâya; amukal; igl

Local Common Names

  • Finland: niilinahven
  • Germany: Albertseebarsch; Nilbarsch; Victoriabarsch; Victoriasee-Barsch
  • Ghana: dzo; lesi
  • Kenya: mbuta
  • Netherlands: nijlbaars
  • Nigeria: aja; bangur; giwan ruwa; giwan ruwan; igbo; kima; kina
  • Norway: nilabbor
  • Portugal: perca-do-Nilo
  • Senegal: diène wekh
  • Sudan: cal; ceil; gubro; gur; gwet; ndeni; nganzi
  • Sweden: nilabborre
  • Tanzania: chengu; mkombozi; sangala; sangara
  • Uganda: mputa

Summary of Invasiveness

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L. niloticus is a large perch-like predator that is native and widespread in parts of Africa, mainly above the equator (Froese and Pauly, 2009). During the 1950s and 1960s L. niloticus was introduced into several East-African lakes (Pringle, 2005). It became established in most of these, however only Lakes Victoria, Kyoga and Nabugabo were relatively well studied. In each of the latter lakes L. niloticus became the dominant fish species and concomitantly many other species declined or disappeared completely (Ogutu-Ohwayo, 1990a; 1993; Kaufman, 1992; Witte et al., 1992). Most striking was the case of Lake Victoria, where L. niloticus boomed some 25 years after its introduction and subsequently comprised over 90% of the demersal fish mass. It is estimated that some 200 endemic haplochromine cichlid species vanished as a result of predation and competition (Witte et al., 1992a,b). L. niloticus has been listed among the 100 "World's Worst" invaders (ISSG, 2009).

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Chordata
  •             Subphylum: Vertebrata
  •                 Class: Actinopterygii
  •                     Order: Perciformes
  •                         Suborder: Percoidei
  •                             Family: Centropomidae
  •                                 Genus: Lates
  •                                     Species: Lates niloticus

Notes on Taxonomy and Nomenclature

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Nile perch was originally described as Perca nilotica by Linnaeus (1758). The name was changed into Lates niloticus by Cuvier (in Cuvier & Valenciennes, 1828). Greenwood (1976) considered the Luciolates (Boulenger, 1914) species of Lake Tanganyika to be a subgenus of Lates, and therefore arranged the eight extant Lates species into two subgenera: Lates (Lates) comprising Lates (Lates) niloticus and three other species (see below), and Lates (Luciolates) for four species from Lake Tanganyika.

Related species: Lates (Lates) calcarifer (Bloch, 1792), from the Indo-Pacific region, Lates (Lates) longispinis Worthington, 1932, from the deeper waters of Lake Turkana (formerly Rudolf) and Lates (Lates) macrophthalmus Worthington, 1929 from Lake Albert in open waters from 20-40 m depth. Lates (Luciolates) angustifrons Boulenger, 1906, Lates (Luciolates) mariae Steindachner, 1909, Lates (Luciolates) microlepis Boulenger, 1898 and Lates (Luciolates) stappersi (Boulenger, 1914) all from Lake Tanganyika (Greenwood, 1976; Daget, 1986).

Lates albertianus Worthington, 1929 from Lake Albert and L. niloticus rudolfianus Worthington, 1932 from Lake Turkana are considered synonyms of L. niloticus (Holden, 1967; Greenwood, 1976).
 
Taxonomic investigations of Lates specimens from Lake Victoria, based on traditional taxonomic measurements, failed to identify these fishes unambiguously as L. niloticus (Harrison, 1991). It is possible that several Lates species wereintroduced into Lake Victoria viz. L. niloticus and L. macrophthalmus and/or L. longispinis, and that Lates from Lake Victoria is a hybrid (Harrison, 1991) (see section under Genetics).

Description

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Description of adult fish following van Oijen (1995): Body deep and somewhat compressed; scales small and ctenoid. Small villiform teeth in the jaws and on the vomer, palatines and ectopterogoids (bones forming part of the roof of the mouth). Pre-obital and pre-opercular bones armed with spines; a large spine on the free edge of the operculum. Dorsal fin almost completely divided into two parts by a deep notch; the anterior part comprises 7 to 8 spines and the posterior part 1 spine and 10 to 14 branched rays. The lateral line contains 60 to 80 scales. Interorbital space at least equal to the diameter of the eye in adults; caudal peduncle as long as deep, or a little longer than deep. Colour: dorsum dark greyish-blue, flank and ventral side greyish-silver.

Lates longispinis from Lake Turkana can be distinguished from Lates niloticus by its larger eye (diameter 22.6-39.9% of head in fishes of 12-27 cm standard length, cf. 18.3-22.9% in L. niloticus of a comparable size; in both taxa the eye size is negatively correlated with standard length) and longer third spine in the dorsal fin (78-84% of head, cf. 55-70%) (Greenwood, 1976).
 
Lates macrophthalmus from Lake Albert can also be distinguished from L. niloticus by its larger eye and elongate third spine in the dorsal fin, but the dorsal fin spine is shorter than in L.longispinis (78-84% of head, mean 82.0% in L. longispinis, cf. 65-84%, mean 74.4% in L. macrophthalmus) (Greenwood, 1976).
 
Harrison (1991) found that riverine L. niloticus differs both from that in Lake Albert and from that in Lake Turkana, but no significant difference was found between the latter two. The Lake Victoria collection was found to differ from all other taxa. Therefore, Harrison (1991) suggested that the characters currently used in the taxonomy of Lates are inappropriate for this purpose. He recommended that a reappraisal of Nile perch taxonomy be made using more modern techniques and that studies are initiated to discover how characters change during development under differing environmental conditions.
 
L. niloticus is distinguished from the four species endemic to Lake Tanganyika by having an ethmovomerine skull region that is not noticeably elongate (Greenwood, 1976).

Distribution

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L. niloticus is widespread throughout the Ethiopian region of Africa and occurs commonly in all the major river basins including the Nile, Chad, Senegal, Volta and Zaire. It is present in the brackish waters of Lake Mariout, near Alexandria and exists in Lakes Albert, Turkana (formerly Rudolf) (Daget, 1986) and Chad (Hopson, 1972), but not in Lake Tana as erroneously suggested by Daget (1986).

In the 1950s and 1960s, Nile perch (see Pictures) was introduced into Lake Kyoga, Lake Victoria and Lake Nabugabo from Lakes Albert and Chad (Pringle, 2005). It spread into several satellite lakes of Lake Kyoga, e.g. Lakes Bisina, Nakuwa and Nyasala (Mwanja et al., 2001), and of Lake Victoria, e.g. Lake Sare (Aloo, 2003). 

 

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Africa

BeninPresentNative Not invasive Froese and Pauly, 2009
Burkina FasoPresentNative Not invasive ISSG, 2009
CameroonPresentNative Not invasive Froese and Pauly, 2009
Central African RepublicPresentNative Not invasive ISSG, 2009
ChadPresentNative Not invasive Froese and Pauly, 2009
CongoPresentNative Not invasive ISSG, 2009
Congo Democratic RepublicPresentNative Not invasive ISSG, 2009
Côte d'IvoirePresentNative Not invasive Froese and Pauly, 2009
EgyptPresentNative Not invasive Froese and Pauly, 2009
EthiopiaPresentNative Not invasive Froese and Pauly, 2009
GhanaPresentNative Not invasive Froese and Pauly, 2009
GuineaPresentNative Not invasive Froese and Pauly, 2009
Guinea-BissauPresentNative Not invasive Froese and Pauly, 2009
KenyaPresentIntroduced1954 Invasive IPPC-Secretariat, 2005; Pringle, 2005; Froese and Pauly, 2013
LiberiaPresentNative Not invasive Froese and Pauly, 2009
MaliPresentNative Not invasive Froese and Pauly, 2009
MauritaniaPresentNative Not invasive Froese and Pauly, 2009
MoroccoIntroduced, not establishedIntroduced Not invasive Froese and Pauly, 2009
NigerPresentNative Not invasive Froese and Pauly, 2009
NigeriaPresentNative Not invasive Froese and Pauly, 2009
SenegalPresentNative Not invasive Froese and Pauly, 2009
Sierra LeonePresentNative Not invasive Froese and Pauly, 2009
SudanPresentNative Not invasive Bailey, 1994
TanzaniaPresentIntroduced Invasive Pringle, 2005First recorded near Mwanza in October 1961
TogoPresentNative Not invasive Froese and Pauly, 2009
UgandaPresentNative Not invasive Pringle, 2005; Froese and Pauly, 2009

North America

USAPresentPresent based on regional distribution.
-TexasPresentIntroduced Not invasive ISSG, 2009

Central America and Caribbean

CubaPresent1983IntroducedWelcomme, 1988

History of Introduction and Spread

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The first lake-wide fish survey in Lake Victoria (Graham, 1929) revealed a dominance of haplochromine cichlids. Graham mentioned that it had been suggested to him frequently, that a large predator should be introduced that could convert these small fish into a commercially more interesting fish. However, as a warning he wrote: “The introduction of a large predatory species from another area would be attended with the utmost danger, unless preceded by extensive research into the probable effects of the operation”. Despite this warning, Nile perch was introduced into the lake, after the catches of other major food fishes had declined (Pringle, 2005; Goudswaard et al., 2008).
 
Nile perch were unofficially introduced into Lake Victoria in August 1954, when individuals from Lake Albert were released at Jinja, Uganda (Amaras, 1986). In May 1960, local fishermen reported the first Nile perch from gillnet catches near Jinja (Gee, 1964). Seven others were reported in the same year. The fishes recorded in 1960 from the northeast corner of the lake, were 28-43 cm long (Hamblyn, 1961). They were probably offspring of those introduced in 1954, as during six years the introduced individuals would have attained a much greater length (e.g. Hughes, 1992a). According to Gee (1964), a breeding population existed in the lake in 1962/63, probably centered in Hannington Bay and down the Buvumu Channel.
 
After heavy debates (Fryer, 1960; Anderson, 1961; Pringle, 2005), the first official introductions of Nile perch took place in May 1962 and September 1963 at Entebbe, Uganda. They originated from Lake Albert and comprised respectively 35 fishes between 16 and 43 cm, and 339 fingerlings (Gee, 1964). In the Nyanza Gulf, Kenya, eight Nile perch from Lake Turkana were released in 1963 (Arunga, 1981; Pringle, 2005).
 
According to Pringle (2005), the first Nile perch reported from Tanzanian waters was caught near Mwanza in October 1961. Other reports suggest that Nile perch was landed for the first time from Tanzanian waters of the lake in August 1963 at Musoma (Kudhongania and Cordone, 1974a). During a bottom trawl survey in 1969-1970 Nile perch was rarely caught in Tanzanian waters. Catches constituted approximately 0.01 kg h-1, whereas the catches in Uganda and Kenya were 0.48 and 1.12 kg h-1, respectively (Kudhongania and Cordone, 1974a,b).
 
The upsurge of Nile perch in Lake Victoria was first observed in the Nyanza Gulf, Kenya, in 1979. In Ugandan waters it occurred 2-3 years later and in the Tanzanian Mwanza Gulf 4-5 years later (see Pictures). At the beginning of the upsurge in the Mwanza Gulf in 1983/84 only sub-adult and adult fishes were found. The first juveniles appeared in 1985, suggesting that the initial increase of Nile perch was mainly caused by migration of sub-adults and adults (Goudswaard et al., 2008).
 
Based on the foregoing observations it was hypothesised that a decline of haplochromines by over fishing in the Nyanza Gulf might have decreased predation on Nile perch brood and competition with juvenile Nile perch, thus facilitating their survival and resulting in a local Nile perch boom (Goudswaard et al., 2008). Subsequent mass migration of adult and sub-adult Nile perch to new areas may have affected haplochromines there, and paved the way for further successful recruitment (Goudswaard et al., 2008).
 
Nile perch were introduced into Lake Kyoga in 1954 and 1955 and into Lake Nabugabo in 1960 and 1963 (Ogutu-Ohwayo, 1993; Pringle, 2005). The aim of these introductions was to assess what effect Nile perch would have on fish faunas similar to that of Lake Victoria (Ogutu-Ohwayo, 1993), as it was not known then that Nile perch had been stocked already unofficially in the latter. 

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Cuba Ethiopia 1982-1983 Aquaculture (pathway cause) ,
Hunting, angling, sport or racing (pathway cause)
Welcomme (1988)
Kenya Uganda 1954-1963 Fisheries (pathway cause) Yes Pringle (2005) To Lake Victoria from Lake Albert. Spread into Kenyan waters from Ugandan side
Kenya Kenya 1963 Fisheries (pathway cause) Yes Pringle (2005) To Lake Victoria from Lake Turkana. Only 8 fish
Tanzania Uganda 1954-1963 Fisheries (pathway cause) Yes Goudswaard et al. (2008); Pringle (2005) To Lake Victoria from Lake Albert. Spread into Tanzanian waters from Ugandan side
Texas Africa 1979 Aquaculture (pathway cause) ,
Fisheries (pathway cause) ,
Hunting, angling, sport or racing (pathway cause)
No Froese and Pauly (2009)
Uganda Uganda 1954 Aquaculture (pathway cause) ,
Fisheries (pathway cause)
Pringle (2005) To Muchison Falls, Victoria Nile from Lake Albert
Uganda Uganda 1954-1955 Fisheries (pathway cause) Yes Pringle (2005) To Lake Kyoga from Lake Albert
Uganda Uganda 1963 Fisheries (pathway cause)Pringle (2005) To Kagera River and Lake Kijanebalola from Lake Albert
Uganda Uganda 1960, 1963 Fisheries (pathway cause) Yes Ogutu-Ohwayo (1993); Pringle (2005) To Lake Nabugabo from Lake Albert
Uganda Uganda 1963 Fisheries (pathway cause)Pringle (2005) To Lake Saka and Lake Salisbury from Lake Albert
Uganda Uganda 1954-1963 Fisheries (pathway cause) Yes Pringle (2005) To Lake Victoria from Lake Albert

Risk of Introduction

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Since its deliberate introduction into Lake Victoria and Lake Kyoga, L. niloticus has spread, accidentally or by deliberate introductions, into several lagoons and satellite lakes. There are still satellite lakes around Lakes Victoria and Kyoga where Nile perch is absent, for instance: Lakes Nawampasa, Lemwa and Nyaguo near Lake Kyoga; Lakes Kachera, Kijanebalola and Mburo (the Kioki lakes ) at the Ugandan side of Lake Victoria (Mwanja et al., 2001); Lakes Kanyaboli and Namboyo at the Kenyan side (Aloo, 2003); Lakes Katwe, Ikimba, Burigi, Malimbe, Kirumi and Kubigena at the Tanzanian side of Lake Victoria (Katunzi and Kishe, 2004). These lakes function as faunal refugia (Kaufman et al., 1997; Mwanja et al., 2001; Aloo, 2003; Mbabazi et al., 2004). There is a risk that in due time Nile perch will get into these lakes as well.

Habitat

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In Lake Victoria L. niloticus occurs at depths from 1-60 m (Goudswaard et al., 2008), but in its lakes of origin (Albert and Turkana), L. niloticus occupies shallower, more inshore habitats, than L. macrophthalmus and L. longispinis respectively (Daget, 1986). No exact depth distributions for L. niloticus in these native lakes are given, though it is mentioned that L. macrophthalmus in Lake Albert lives at depths of 20-40 m (Gee, 1964). L. niloticus tends to avoid areas with low dissolved oxyen levels, such as wetland areas (Chapman et al., 1996; 2002).

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Brackish
Inland saline areas Present, no further details
Freshwater
 
Irrigation channels Present, no further details
Lakes Principal habitat Harmful (pest or invasive)
Lakes Principal habitat Natural
Reservoirs Present, no further details
Rivers / streams Present, no further details Natural

Biology and Ecology

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Genetics

Allozyme data indicated that the introduced Nile perch of Lake Victoria were mainly L. niloticus from Lake Albert, although maximum likelihood estimates of stock contributions suggested the presence of L. macrophthalmus. In contrast, introduced Nile perch in adjacent smaller lakes (Lakes Kyoga and Nabugabo) appeared to be entirely L. niloticus (Hauser et al., 1998). DNA sequence data is also available for L. niloticus, see Ward et al. (2005) and Edmunds et al. (2009).
 
Reproductive Biology
 
Period: Around the year with peaks in the rainy season (Ligtvoet and Mkumbo, 1990).
 
Spawning area: Probably preferably in shallow sheltered areas (Ligtvoet and Mkumbo, 1990).
 
Nurseries: In Lakes Chad, Albert and Turkana, L. niloticus seem to spawn at shallow, sheltered and vegetated sites and juveniles up to a length ca. 20-30 cm lived in the vicinity of submerged vegetation (Hamblyn, 1962; Hopson, 1972; Arunga, 1981). In contrast, L. niloticus as small as 10 cm were caught in the open waters of Lake Nabugabo, approximately 700 m from the shore (Schofield and Chapman, 1999). In the Nyanza Gulf of Lake Victoria, postlarvae measuring 1-2 cm TL occurred in littoral weeds dominated by Ceratophyllum and appeared to be restricted to the shallow inshore areas (Ogari, 1985; Asila and Ogari, 1988 referring to Ogari, 1984). However, in October 1993, juveniles of this size were also collected over bare mud bottoms up to depths of 14 m, along a transect across the Mwanza Gulf of Lake Victoria (O Seehausen and F Witte, Leiden University, The Netherlands, personal communication, 2009). Juveniles smaller than 5 cm occurred as far as 3 km offshore, at depths of more than 20 m (Ogari, 1985; Katunzi et al., 2006). However, highest concentrations of small juveniles <5 cm TL) were found in littoral and sub-littoral areas (Katunzi et al., 2006). Juveniles <20 cm TL occurred up to 57 m deep (PC Goudswaard, Leiden University, The Netherlands, personal communication, 2009).
 
Size at maturity: According to Ogutu-Ohwayo (2004), shortly after the introduction, the size at maturity of Nile perch in Lakes Victoria and Kyoga was smaller than in the native habitats. The size at maturity for males in Lake Victoria between 1964 and 1967 was 30-34 cm TL, and between 1988 and 1992 it was 50-54 cm TL. In 1999-2000 it was still 54.2 cm (Mkumbo et al., 2007). For females Ogutu-Ohwayo (2004) recorded 40-59 cm TL between 1964 and 1977, and 90-99 cm between 1988 and 1992. By 1999-2000 the first size at maturity of females had decreased to 76.4 cm (Mkumbo et al., 2007). Acere (1985) reported a first maturity of males and females in Ugandan waters of Lake Victoria (1964-1977) was at 53.5 cm TL (age 1+ or year 2) and 67.5 cm TL (age 1+ or year 2), respectively.
 
First maturity of males and females in the Nyanza Gulf of Lake Victoria in 1983 was found at 50-55 cm TL (ca. 2 years old) and 80-85 cm TL (ca. 4 years old) respectively (Hughes, l992a). Fifty percent maturity in the Nyanza Gulf (1978-1984) was found at 74 cm TL for males and 102 cm TL for females (Asila and Ogari, 1988). By the end of the 1980s, fifty percent maturity in the Nyanza Gulf had decreased to 55 cm TL for males and 70 cm TL for females (Ogari and Asila, 1992 referring to Asila, 1991).
 
First maturity of males and females in the Mwanza Gulf (1988-1989) was at 35-40 cm TL and 50-60 cm TL respectively (PJ Mous, Wageningen University, The Netherlands, personal communication, 2009). Fifty percent maturity of males and females in the Mwanza Gulf in 1988-1989 was at 60 cm TL and 110 cm TL respectively (Ligtvoet and Mkumbo, 1990; PJ Mous, Wageningen University, The Netherlands, personal communication, 2009).
 
Ogutu-Ohwayo (2004) found that the sizes at maturity in Lake Albert between 1989 and 1992, in Lake Kyoga between 1967 and 1993, and in Lake Nabugabo between 1991 and 1993 were close to those of Lake Victoria between 1988 and 1992.
 
Fecundity: In Lake Kyoga Ogutu-Ohwayo (1988) found the following relation for egg number and standard length of Nile perch: F = 4.436 x 10-6 x SL2.92 (F is number of eggs in millions; SL in cm). For Lake Victoria a range of 3,000,000 to 15,000,000 eggs has been reported (Asila and Ogari, 1988).
 
Sex ratio: According to Ogutu-Ohwayo (2004) the proportion of mature females in Lake Victoria between 1964 and 1977 was higher than in Lake Albert between 1989 and 1992 (m:f ~ 2:3 in Lake Victoria and ~ 3:2 in Lake Albert). The proportion of females in Lake Victoria between 1982 and 1992, and in Lakes Kyoga (1967-1993) and Nabugabo (1991-1993) was lower (m:f ~ 3.5:1) than that for Lake Albert (1989-1992, m:f ~ 3:2).
 
Ligtvoet and Mkumbo (1990) reported ratios of males to females ranging from 10:1 to 7:1, in fish below 80 cm TL; in larger fish the proportion of males rapidly decreased (m:f = 1:1 at 90 cm; 1:10 at 100 cm TL).
 
In Lake Chad the sex ratio changed with increasing length, from a dominance of males to dominance of females (Hopson, 1972). Further, there was a difference between inshore and offshore fish. In the former group, males and females of 52-62 cm TL were equally abundant, whereas in the offshore fish of this size males were more abundant (m:f ~ 3:1).
 
Growth: Fish in Ugandan waters of Lake Victoria (1964-1977) reached 52 cm in year 1 and 100-110 cm in year 5 (Acere, 1985; based on length-frequency analysis).
Length frequency data from the Nyanza Gulf of Lake Victoria (1983) suggest a total length of 9 cm by age 118 days and of 23 cm by age 287 days (Hughes, 1992a).
Ligtvoet and Mkumbo (1990) reported growth increments of 28, 28 and 21 cm/year for 3 fishes that were tagged in the Mwanza area of Lake Victoria at lengths of 32, 47 and 51 cm respectively.
 
In Lake Chad mean lengths of both sexes combined after years 1 to 8 were respectively 21, 38, 51, 61, 69, 77, 86 and 94 cm TL (Hopson, 1972).
 
Nutrition
 
During the past decades several studies have been made on the diet of Nile perch in Lake Victoria, and in Lakes Kyoga and Nabugabo (Hamblyn, 1964; Gee, 1969; Ogari, 1985; Hughes, 1986; 1992b; Ogari and Dadzie, 1988; Ogutu-Ohwayo, 1990b, 1993; Mkumbo and Ligtvoet, 1992; Schofield and Chapman, 1999; Paterson and Chapman, 2009). In lakes Kyoga and Victoria, in the 1980s after the boom of the Nile perch, a shift in diet from one dominated by haplochromine cichlids to one dominated by the shrimp Caridina nilotica, was noted (Hamblyn, 1964; Hughes, 1986; 1992b; Ogari and Dadzie, 1988; Ogutu-Ohwayo, 1990b; Mkumbo and Ligtvoet, 1992, Katunzi et al., 2006). In Lake Nabugabo, where shrimps appeared to be absent, fish (mainly the cyprinid Rastrineobola argentea and juvenile Nile perch) remained the main prey types (Ogutu-Ohwayo, 1993; Schofield and Chapman, 1999). Since the recovery of haplochromines in the three lakes, in the course of the 1990s, a shift back to haplochomines has been observed (Balirwa, 2007; Paterson and Chapman, 2009; M Kishe-Machumu, Tanzania Fisheries Research Institute, Mwanza, Tanzania, personal communication, 2009).
 
Distinct ontogenetic changes in foraging patterns of Nile perch have been described (Hopson, 1972; Hughes, 1986; Ogari and Dadzie, 1988; Ogutu-Ohwayo, 1990b, 1993, 2004; Schofield and Chapman, 1999; Katunzi et al., 2006). In Lake Chad, Nile perch ate zooplankton until a size of ca. 3 cm. In pelagic larvae of 4-14 mm cladocerans dominated, and in the onshore post-larvae >1 cm, cyclopoid copepods (Hopson, 1972). Calanoid copepods were rare in the diet in this lake. In fish of more than 7 cm TL the shrimp Macrobrachium niloticum and fish became increasingly important and in L. niloticus of more than 60 cm, fish were the dominant prey. In inshore L. niloticus, the shift from Macrobrachium to fish was more abrupt and fish dominated already above 36 cm TL (Hopson, 1972).
 
In the Mwanza Gulf of Lake Victoria, zooplanktivory was confined to Nile perch < 5 cm. The proportion of cyclopoid copepods decreased and that of calanoids increased with size of the fish; zooplankton was followed by midge larvae. Shrimps, dragonfly nymphs, dagaa and small Nile perch were eaten by all size classes above 5 cm (Katunzi et al., 2006). In 1988-1989, when haplochromine cichlids were absent in the Mwanza Gulf, the switch to fish (juvenile Nile perch and R. argentea) in shallow inshore areas < 4 m) occurred around 10 cm SL, whereas in deeper, offshore areas (> 12m) Nile perch shifted to the shrimp C. nilotica, which remained the dominant prey up to at least 30 cm (larger fish were not included in the study; Katunzi et al., 2006). In the Kenyan and Ugandan parts of the lake, in years when haplochromines were absent, shrimps were the dominant prey up to 50 cm TL and were common up to 80 cm TL (Hughes, 1986, 1992b; Ogari and Dadzie, 1988; Ogutu-Ohwayo, 1990b; Mkumbo and Ligtvoet, 1992).Nile perch larger than 100 cm were mainly piscivorous.
 
Environmental Requirements
 
In Lakes Albert and Turkana, where L. niloticus is native, it mainly occupies shallow water and the deeper parts of these lakes are inhabited by L. macrophthalmus and L. longispinis respectively (Gee, 1964; 1969). In Lake Victoria Nile perch has been caught at depths from 1–60 m (Goudswaard et al., 2006, 2008). Between 1984 and 1988 highest catch rates of Nile perch in the Tanzanian part of Lake Victoria were from depths between 20 and 40 m deep (Goudswaard et al., 2008). L. niloticus is known for its sensitivity to low dissolved oxygen levels (Fish, 1956; Schofield and Chapman, 2000; Wanink et al., 2001; Chapman et al., 2002). Under experimental conditions, aquatic surface respiration was initiated by Nile perch from Lake Nabugabo, when the oxygen tension fell below 40 mm Hg (approximately 3.0 mg l-1; Schofield and Chapman, 2000). In periods when DO levels near the bottom of Lake Victoria were less than 2.5 mg l-1 Nile perch seemed to migrate upwards and dwelled just above the oxycline (Wanink et al., 2001; Goudswaard et al., 2006).

 

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
27 7

Water Tolerances

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ParameterMinimum ValueMaximum ValueTypical ValueStatusLife StageNotes
Dissolved oxygen (mg/l) Optimum > 2.0 tolerated. Mean critical oxygen tension 26.72+1.72 mm Hg (Chapman et al., 2002). Aquatic surface respiration starts at 30 mm Hg (ca 3 mg) (Schofield and Chapman, 2000)
Water temperature (ºC temperature) Optimum Optimum for feeding 27.5, max. lethal 38 (Kitchell et al.,1997)

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Crocodylus niloticus Predator not specific Green, 2009

Notes on Natural Enemies

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Natural enemies comprise man and Crocodylus niloticus (Green, 2009).

Means of Movement and Dispersal

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The results of a tagging experiment in the Mwanza region of Lake Victoria revealed movements of individuals of 50 km in one week and of almost 100 km within two months and of 150 km in six months (Ligtvoet and Mkumbo, 1990). One individual that was tagged in the Mwanza area was recaptured near Jinja at the opposite side of the lake (Witte and de Winter, 1995).

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Water Yes

Impact Summary

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CategoryImpact
Cultural/amenity Positive and negative
Economic/livelihood Positive and negative
Environment (generally) Negative
Human health Positive and negative

Economic Impact

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In the 1990s filleting factories arose which exported Nile perch fillets to Europe and Asia (Ntiba et al., 2001). The total capacity of these factories was several hundred tons per day and they became the main buyers of Nile perch. Many of these fish processing plants operated below their installed capacity. Balirwa (2007) reports for Uganda alone, 15 factories with a total installed capacity of 420 t per day, but actually processing 185 t per day.

At the beginning of the century, about 1.2 million people were directly or indirectly dependent for livelihoods on the fishery in Lake Victoria (Matsuishi et al., 2006). In 2003 the estimated annual catch was worth at least US $540 million at the fish landings, whereas a further US $240 million was earned in fish exports (Balirwa, 2007).

 

Environmental Impact

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Impacts on Habitat

It has been suggested that the algal blooms that occurred concomitantly with the Nile perch boom in different areas of Lake Victoria, were (partly) caused by a top down effect, i.e. disappearance of the phytoplanktivorous and detritivorous haplochromine cichlids by Nile perch predation (Kilham and Kilham, 1990; Kaufman, 1992; Hecky and Bugenyi, 1992; Goldschmidt et al., 1993; Ochumba, 1995; Ogutu-Ohwayo, 1999). Conversely, it has been suggested that the increase of the eutrophication that started already in the 1920s had a negative impact on haplochromines and provided an opportunity for the Nile perch boom (Hecky, 1993; Verschuren et al., 2002; Kolding et al., 2008).

Other environmental issues associated with this species include the demand for firewood for processing the fish. At Wichlum Beach (Kenya) the number of smoking kilns increased between 1984 and 1991 from about ten to over 50 (Riedmiller, 1994). Although the majority of the Nile perch catches are currently sold to the fish filleting factories, unsuitable individuals (e.g. fish that are too small) and waste from the factories are still smoked and/or fried. These activities contribute to deforestation, and consequently to land erosion and eutrophication of the lake.

Impacts on Biodiversity

It has so far been impossible to establish the causal relationship between the Nile perch boom and eutrophication, and the relative impact on haplochromine cichlids of each of these phenomena separately. There are a number of reasons for this. First, both the Nile perch upsurge in Lake Victoria and the increase of eutrophication occurred between the late 1960s and early 1980s. Furthermore, systematic data on haplochromine abundance and diversity were not collected until 1969/70 and 1978, respectively (Kudhongania and Cordone, 1974a,b; Witte, 1981).

Eutrophication resulted in decreases in dissolved oxygen levels and increased water turbidity. The latter especially has a negative impact on haplochromines and among others resulted in hybridization of several species (Seehausen et al., 1997a; 2008). Nevertheless, there is ample evidence that Nile perch predation did have a strong impact on haplochromine biodiversity (e.g. Witte et al., 2007a,b; Chapman et al., 2008).
 
In 1983 Nile perch started to boom in the Mwanza Gulf (see Pictures), mainly due to immigration of sub-adult fishes (Goudswaard et al., 2008). Concomitantly, the decline of some groups of haplochromines accelerated strongly in the sub-littoral and open waters, and shortly after the Nile perch peak in 1986-1987 haplochromines had virtually disappeared from the catches in these areas (see Pictures). Until the haplochromines had disappeared, they were the main food items of Nile perch (Ligtvoet and Mkumbo, 1990; Mkumbo and Ligtvoet, 1992). Scanty data from other parts of the lake indicate similar accelerations of the decline of haplochromines after Nile perch began to boom in those areas (Witte et al., 1995). In shallow areas, with relatively low Nile perch densities and areas with structured bottoms, such as rocky shores, haplochromines were less affected (Witte et al., 1992b; Seehausen et al., 1997b).
 
In Lake Kyoga and Lake Nabugabo, where Nile perch had also been introduced as well, the haplochromines also declined strongly with increasing Nile perch densities (Ogutu-Ohwayo, 1990a,b; 1993; 1995). In contrast, in several small satellite lakes of Lake Victoria and Lake Kyoga, where Nile perch was absent, haplochromines remained abundant (Ogutu-Ohwayo, 1993; Namulemo and Mbabazi, 2000; Aloo, 2003; Mbabazi et al., 2004). However, it has to be mentioned as a confounding factor, that in some of these lakes the water was also clear (Kaufman et al., 1997; G Namulemo, Fisheries Resource Research Institute, Uganda, personal communication, 2009). There are a few satellite lakes where Nile perch and haplochomines seem to coexist. Aloo (2003) found both haplochromines and Nile perch in the murky Lake Sare (transparency 0.25 m), but did not record when Nile perch entered this lake and how many cichlid species used to live there before Nile perch introduction. Nile perch and haplochromines also seem to coexist in Lake Saka in Uganda (Witte et al., 2007b). In Lake Nabugabo haplochromines apparently found refugia in the hypoxic and highly structured shoreline wetlands (Chapman et al., 1996; 2002; 2003). The same may hold for a few wetland species of Lake Victoria, but not for the sub-littoral and deepwater species, or for those of sandy shores of Lake Victoria, because many of them were strongly restricted to these habitats (e.g. Witte (1984)) that are often at great distances from wetlands.
 
Nile perch predation and competition also caused declines in native species other than haplochromines, e.g. the lung fish (Protopterus aethiopicus), catfishes (e.g. Bagrus docmak, Xenoclarias eupogon, Synodontis victoria) (Ogutu-Ohwayo, 1990a,b; Goudswaard and Witte, 1997; Goudswaard et al., 2002a,b). By the end of the 1980s only three fish species were common in sub-littoral and offshore waters of Lake Victoria; these were the small indigenous cyprinid Rastrineobola argentea, and the introduced Nile perch and Nile tilapia (Ogutu-Ohwayo, 1990; Wanink, 1999; Goudswaard et al., 2002b). Together, they dominated the fish landings by more than 80% (see Pictures) (Reynolds et al., 1995; Witte et al., 2009).
 
In the course of the 1990s, after a decline in Nile perch in Lake Victoria due to intensive fishing, a slow resurgence of some haplochromine species was observed, mainly zooplanktivores and detritivores (Witte et al., 2000; 2007a,b; Seehausen et al., 1997b; Balirwa et al., 2003). Of each group only about 30% of the species recovered and the ratio between detritivores and zooplanktivores reversed (Witte et al., 2007 a,b). Before the 1980s detritivores made up about 50% of the haplochromine biomass in the sublittoral waters and zooplanktivores about 25% (Goldschmidt et al., 1993), whereas by 2001 detritivores constituted only 15% and zooplanktivores more than 80%. However, the majority of the species did not recover. Many of the highly specialized trophic types like scale eaters, parasite eaters and prawn eaters have not been caught since the 1980s, whereas piscivores and paedophages are extremely rare now, both with respect to numbers of individuals and species.
 
The hypothesis that Nile perch had a large impact on haplochromine biomass is supported by the observations of a partial recovery of haplochromines in Lake Victoria, Lake Nabugabo and Lake Kyoga, following declines in Nile perch due to heavy fishing pressure (Ogutu-Ohwayo, 1995; Witte et al., 2000; Chapman et al., 2003; 2008; Getabu et al., 2003; Mbabazi et al., 2004). On the other hand, the incomplete recovery in Lake Victoria suggests that Nile perch may not be the only factor (Witte et al., 2007b).

Threatened Species

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Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Bagrus docmakNo Details
HaplochromisNE (IUCN red list: Not evaluated)
Synodontis afrofischeriLC (IUCN red list: Least concern)
Synodontis victoriaeNT (IUCN red list: Near threatened)
Xenoclarias eupogonCR (IUCN red list: Critically endangered)

Social Impact

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The changes in the fishery had impacts at the in­dividu­al, the house­hold and the communi­ty level. The following changes were mentio­ned by Harris et al. (1995): (1) Fishing was traditionally mixed with agricultural and pastoral activities and it used to be a house­hold enter­prise in which the whole family was involved. The husband was the boat owner and fisherman, his son crew and his wife or daughters fish processors or dealers. Because currently more capital is needed for the fishe­ry, fisher­men are often not the boat- or net-ow­ners, but employees.(2) Fishermen are now away from home for extended periods, and their wives and other members of the family are no longer involved with their activities. (3) The availa­bi­lity of fish for household consumption decrea­sed. Due to the relatively high price, the mana­gers do not like fish to be taken home by crew members. (4) The increased value of the nets and the fish led to an increased incidence of net and fish thefts. This led to distrust among local fis­hers and between boat owners and operators.

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Abundant in its native range
  • Is a habitat generalist
  • Capable of securing and ingesting a wide range of food
  • Highly mobile locally
  • Long lived
  • Fast growing
  • Has high reproductive potential
Impact outcomes
  • Altered trophic level
  • Changed gene pool/ selective loss of genotypes
  • Damaged ecosystem services
  • Ecosystem change/ habitat alteration
  • Modification of natural benthic communities
  • Modification of nutrient regime
  • Negatively impacts cultural/traditional practices
  • Reduced native biodiversity
  • Threat to/ loss of endangered species
  • Threat to/ loss of native species
Impact mechanisms
  • Competition - monopolizing resources
  • Predation
  • Rapid growth
Likelihood of entry/control
  • Difficult/costly to control

Uses

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Originally, the fishermen did not like Nile perch, because they had problems with handling, processing and marketing the fish; the larger and relatively fat perches could not easily be dried or transported. However, in the years after the upsurge, people rapidly adjusted the processing and transport techniques. The larger fishes were chopped into pieces and fried (Ligtvoet et al., 1995). The smaller ones were dried in the sun or smoked. In the 1990s filleting factories arose which export Nile perch fillets to Europe and Asia (Ntiba et al., 2001; Balirwa, 2007).

Apart from fillets, the Nile perch yields swim-bladders, suitable for the production of beer finings and traditional medicines in the Far East, and its skin may be used for leather (Geheb, 1995).
 
Though biodiversity decreased strongly and water quality deteriorated, fish production in Lake Victoria flourished after the Nile perch boom. In the 1960s the total landings for the lake were approximately 100,000 t y-1. In the late 1980s and early 1990s, just after the Nile perch boom, the fisheries produced over 500,000 t of fish annually, an increase by a factor of five (Reynolds et al., 1995; Balirwa, 2007; Witte et al., 2009).
 
In the course of the 1990s the total annual landings did not change much, but the contribution of Nile perch declined, whereas landings of R. argentea and O. niloticus increased (Matsuishi et al., 2006). Just after the boom, Nile perch contributed more than 70% of the landings (Van der Knaap et al., 2002), but between 1990 and 2000 the catch per unit effort for Nile perch dropped from about 80 to 45 kg per boat day (Matsuishi et al., 2006). By 2000 the total landings amounted to 657,000 t, 40% of which was made up by Nile perch, 41% by R. argentea and 8% by O. niloticus (calculated from table 1 in Matsuishi et al., 2006). In 2005-2006, the annual landings were even estimated at 1 million t and the contribution of Nile perch was about 26%, while that of R. argentea had increased to about 53% (LVFO, 2006; Witte et al., 2009). Apparently, the species composition in the fish landings have changed towards lower trophic level species (viz. R. argentea and Nile tilapia; Matsuishi et al., 2006), but hydroacoustic surveys between 1999 and 2007 revealed that over the studied period the overall fish biomass in Lake Victoria remained more or less constant (Getabu et al., 2003; LVFO/IFMP, 2007). The foregoing seems to represent a second fishing down episode in Lake Victoria (Balirwa et al., 2003).
 
Balirwa et al. (2003) suggested that conservation of biodiversity and fishery sustainability may not have to be antitheses in the management of Lake Victoria. A modelling study suggested that Nile perch prefer and grow fastest on a haplochromine prey base (Kaufman and Schwarz, 2002). If the model is realistic, it would suggest that it is worth thinking of management strategies that allow enough fishing on Nile perch to ensure an abundance of their haplochromine prey, but not so much pressure as to threaten the Nile perch stock itself (Balirwa et al., 2003). However, to allow maintenance and restoration of haplochromine diversity, the urgent measures must include serious attempts to reverse the eutrophication of Lake Victoria (Seehausen et al., 1997a; Balirwa et al., 2003; Witte et al., 2005).

Uses List

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General

  • Sport (hunting, shooting, fishing, racing)

Human food and beverage

  • Meat/fat/offal/blood/bone (whole, cut, fresh, frozen, canned, cured, processed or smoked)

Materials

  • Skins/leather/fur

Similarities to Other Species/Conditions

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Lates longispinis from Lake Turkana can be distinguished from Lates niloticus by its larger eye (diameter 22.6-39.9% of head in fishes of 12-27 cm standard length, cf. 18.3-22.9% in L. niloticus of a comparable size; in both taxa the eye size is negatively correlated with standard length) and longer third spine in the dorsal fin (78-84% of head, cf. 55-70%) (Greenwood, 1976).

Lates macrophthalmus from Lake Albert can also be distinguished from L. niloticus by its larger eye and elongate third spine in the dorsal fin, but the dorsal fin spine is shorter than in L.longispinis (78-84% of head, mean 82.0% in L. longispinis, cf. 65-84%, mean 74.4% in L. macrophthalmus) (Greenwood, 1976).

Harrison (1991) found that riverine L. niloticus differs both from that in Lake Albert and from that in Lake Turkana, but no significant difference was found between the latter two. The Lake Victoria collection was found to differ from all other taxa. Therefore, Harrison (1991) suggested that the characters currently used in the taxonomy of Lates are inappropriate for this purpose. He recommended that a reappraisal of Nile perch taxonomy be made using more modern techniques and that studies are initiated to discover how characters change during development under differing environmental conditions.

L. niloticus is distinguished from the four species endemic to Lake Tanganyika by having an ethmovomerine skull region that is not noticeably elongate (Greenwood, 1976).

References

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17/11/09 Original text by:

Frans Witte, Institute of Evolutionary and Ecological Sciences, University of Leiden, P.O. Box 9516, 2300 RA Leiden, Netherlands

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