Overview

Comprehensive Description

Biology

Occurs in both river and swamp habitats and is adapted to fairly fast-flowing rivers (Ref. 6465). Hardy, tolerating fresh and brackish water (up to 20ppt, Ref. 3), preferring slow-flowing or standing water; adults occupy deep open waters, juveniles remain inshore among vegetation (Ref. 7248, 52193). Prefers fairly deep, quiet water with some weed cover; hippo pools are a favoured retreat (Ref. 12524, 13337). Forms schools (Ref. 2, 12524, 13337). Mainly diurnal; a detritivore which feeds on fine particulate matter (Ref. 2), including algae (Ref. 246, 12524, 13337, 53992), diatoms, detritus (Ref. 7248, 52193, 53992) and zooplankton (Ref. 7248, 52193). Larger individuals also take insects and other invertebrates (Ref. 53992). Feeding regime is variable, the diet changes according to food availability (Ref. 6465). Female mouthbrooder (Ref. 87, 246, 6465, 12524, 13337). Fine angling and table species (Ref. 6465, 12524, 13337).
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Distribution

Range Description

This species occurs in the upper Zambezi, as well as the Kafue, Okavango and Cunene Rivers. Occasionally also recorded from the Middle Zambezi (Skelton 2001).

In East Africa, the species was introduced in Kenya in 1980 from Botswana (Motiti Pan, Okavango drainage) by I. Parker for aquaculture purposes. It was introduced to a dam near Nairobi and it is possible that some specimens found their way into the Nairobi River system.
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Africa: Ngami basin, Okavango River; Cunene River and Mossamedes, Angola; upper Zambezi, Kafue River; middle Zambezi, Lake Kariba and Cabora Bassa since construction of dams. Several countries report adverse ecological impact after introduction (2265). Reported as introduced in Kasanka National Park (upper Congo River basin) in Zambia (Ref. 95585).
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Southern Africa.
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Physical Description

Morphology

Dorsal spines (total): 15 - 18; Dorsal soft rays (total): 11 - 15; Analspines: 3; Analsoft rays: 9 - 13; Vertebrae: 30 - 32
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Size

Maximum size: 500 mm SL
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Max. size

61.0 cm TL (male/unsexed; (Ref. 40637)); max. published weight: 4,710 g (Ref. 40637); max. reported age: 13 years (Ref. 13400)
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Diagnostic Description

Diagnosis: male genital papilla bluntly conical with a narrow flange slightly notched in the middle; jaws enlarged in breeding males, which in this species are normally not less than 30cm TL; scales in lateral line series 31-35, usually 32-33; scales of cheek in 3 full rows; vertebrae 30-32; total number of dorsal rays 28-31. Pectoral fin in adults 34-43% SL (Ref. 2), very long (Ref. 1904). Depth of body 40.5-50.5% SL; color-pattern of non-breeding fish and female always including 3 or 4 conspicuous mid-lateral blotches and a red margin on dorsal and caudal fins; breeding male with red margins broader and brighter and general dark, iridescent purplish-brown color of head, back and flanks, masking the blotches; no series of vertical spots or vertical stripes on caudal fin; nest a simple circular depression (Ref. 2).Description: deep bodied (Ref. 12524, 13337, 52307, 54048) with a straight profile (Ref. 1887, 2989, 6465, 12524, 13337, 54048). Snout rounded (Ref. 1887, 2989). Small mouth (Ref. 12524, 13337, 13400), extending to between nostril and eye (Ref. 2989). Lower pharyngeal bone slender (Ref. 54096). Teeth slender, not densely crowded (Ref. 2, 54096), the posterior with a marked second cusp or shoulder; inferior vertebral apophysis only on third vertebra; microbranchiospines present on the outer sides of arches 2 to 4; 5-8 scales between bases of pectoral and pelvic fins; caudal fin only scaled at the base (Ref. 2). Caudal fin with 15 rays (Ref. 1904). Adult large males have the posterior rays of the dorsal fin prolonged (Ref. 12524, 13337). Pectoral fin reaching vertical of origin of anal; pelvic fin reaching between vent and anal; caudal fin rounded; scales cycloid (Ref. 1887, 2989).Coloration: body silvery-grey with upper parts of head and body darker than ventral parts (Ref. 2, 52307). Dorsal fin light green to brown Ref. 12524, 13337). Pectoral (Ref. 1904, 12524, 13337) and pelvic fins light grey ( Ref. 1904) to green; anal fin grey to green at its base (Ref. 12524, 13337). Margins of dorsal and anal fin bright red (Ref. 2, 6465, 7248, 12524, 13337, 52193, 52307). Soft portions of dorsal and anal fins with pale tips and dots (Ref. 2, 1887, 1904, 2989, 6465, 7248, 52193) that are also sometimes visible in the caudal fin (Ref. 2, 52307). 3 prominent black spots present on the flanks (Ref. 2, 1887, 2989, 6465, 12524, 13337, 54048) and a black patch on the posterior portion of the gill cover (Ref. 2, 1887, 2989, 12524, 13337, 54048). The 3 body spots are usually visible from an early age (Ref. 12524, 13337), and are more pronounced in small specimens (Ref. 6465). In breeding males body and fin colours become brighter, with the red seams on the fins becoming more intense (Ref. 2, 7248, 12524, 13337, 52193, 52307) and the snout and cheeks assume a deep maroon coloration (Ref. 12524, 13337, 54048). The caudal fin may appear totally red (Ref. 52307). Juveniles silvery with 6-9 irregular thin bars on body (Ref. 6465, 7248, 12524, 13337, 52193) and 3-4 midlateral spots (Ref. 13337). Young with Tilapia-mark, which disappears or becomes part of the barred pattern of the fin at ca 7cm SL; up to ca 10cm SL vertical bars on the body may predominate and the mid-lateral spots may be faint or absent; 6-10 faint vertical bars appear in dead fish (Ref. 2).
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Adults are found mainly in deeper pools and main river channels. Juveniles and sub-adults are found in a variety of habitats in rivers and floodplain lagoons, large open swamps, and, more rarely small tributaries of the rivers. Feeds on detritus, diatoms and zooplankton. Males excavate large, saucer-shaped nests, females mouthbrood the eggs and fry. Multiple broods are raised during the warmer months. Lives for up to 11 years.

Systems
  • Freshwater
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Environment

benthopelagic; freshwater; brackish; depth range 0 - 10 m (Ref. 54002), usually 3 - 6 m (Ref. 54002)
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Depth range based on 2 specimens in 1 taxon.

Environmental ranges
  Depth range (m): 10 - 10
 
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Trophic Strategy

Occurs in both river and swamp habitats (Refs. 2, 6465). Hardy, tolerating fresh and brackish water (up to 20ppt, Ref. 3), preferring slow-flowing or standing water (Refs. 7248, 12524, 13337, 52193) with some weed cover (Refs. 12524, 13337). Adults occupy deep open waters (Refs. 7248, 12524, 13337, 52193), juveniles remain inshore among vegetation (Refs. 7248, 52193). Hippo pools are a favoured retreat (Refs. 12524, 13337). Forms schools (Refs. 2, 12524, 13337). Mainly diurnal; a detritivore which feeds on fine particulate matter (Ref. 2), including algae (Refs. 246, 12524, 13337, 53992), diatoms, detritus (Ref. 7248, 52193, 53992) and zooplankton (Refs. 7248, 52193). Larger individuals also take insects and other invertebrates (Ref. 53992). Feeding regime is variable, the diet changes according to food availability (Ref. 6465).
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Diseases and Parasites

Fish Tuberculosis 2. Parasitic infestations (protozoa, worms, etc.)
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Fish tuberculosis (FishMB). Bacterial diseases
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Life History and Behavior

Life Cycle

Spawning did not occur in ponds at a temperature below 21°C (Ref. 2). Rarely more than one brood in a season (Ref. 87, 246), but known to breed at least twice a year under pond conditions (Ref. 12524, 13337). Males excavate saucer-shaped nests (Ref. 246, 314, 6465, 12524, 13337, 54048) that can be up to 75cm in diameter and 30cm deep, using mouth and fins (Ref. 2, 314, 52307), in the center of their territory (Ref. 52307), on a sandy substrate (any vegetation is uprooted with its mouth) and in water from 1-3m deep, where they display to attract females (Ref. 12524, 13337, 54048). Up to 40 nests can be found together (Ref. 6465). Females are the primary care-givers (Ref. 52307), moutbrooding eggs, larvae and fry; multiple broods are raised during the warmer months (Ref. 7248, 52193). She lays her eggs in the concavity on top of the nest, the male fertilizes the eggs whereupon the female takes the eggs into her mouth where they are incubated; males guard the nest and females against all intruders; parental care is exercised for the first few weeks after the eggs hatch (Ref. 12524, 13337).
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Oreochromis andersonii

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 13
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
VU
Vulnerable

Red List Criteria
A3e

Version
3.1

Year Assessed
2007

Assessor/s
D. Tweddle & Marshall, B.E.

Reviewer/s
Snoeks, J. (Freshwater Fish Red List Authority) & Darwall, W. (Freshwater Biodiversity Assessment Programme)

Contributor/s

Justification
Insufficient data are available on the apparent declines in abundance, but anecdotal evidence suggests a major decline in stocks on the Barotse floodplain since the 1960s as a result of heavy fishing pressure. The rapid spread of alien O. niloticus through the Kafue system will have had a major impact though data are lacking, and the species is now being promoted for aquaculture in the Upper Zambezi catchment. Under criterion A3e, a population reduction of up to 100% is projected in areas where O. niloticus invades. In these area (i.e., in Zambia as a whole), the species should be classed as CR A3(e). It seems inevitable that the O. niloticus will continue to spread throughout the range of O. andersonii unless drastic steps are taken immediately.

At present, the Okavango population is not immediately threatened, but this system is intermittently linked to the Zambezi and thus it is inevitable that O. niloticus will invade the system unless a barrier is constructed across the Selinda Spillway to prevent migration.

O. andersonii is also recorded from the Cunene River, where O. niloticus does not yet occur. The alien species Oreochromis mossambicus (Peters, 1852) is, however, being extensively cultivated in Namibia and may hybridise with O. andersonii if it escapes in to the Cunene.

Establishing refuges in lakes that are not directly connected to the main rivers or to aquaculture establishments may allow small populations to survive. For this reason, and the possibility that the Cunene population may be secure at present, the species is assessed as Vulnerable globally.
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Population

Population
Fairly common and widespread in the Okavango and Upper Zambezi Rivers, although depleted by fishing in some areas such as the Barotse floodplain.

Population Trend
Decreasing
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Threats

Major Threats
The spread of alien Oreochromis niloticus (L.) as a result of aquaculture introductions in the Kafue and Upper Zambezi catchments is a major threat to the survival of O. andersonii throughout its range (Tweddle et al. 2004). Oreochromis niloticus has caused the extinction of O. esculentus (Graham) and O. variabilis (Boulenger) in Lake Victoria. It has also replaced O. mortimeri (Trewavas) in Lake Kariba, has spread throughout the Kafue Flats in Zambia and is rapidly replacing O. mossambicus (Peters) in the Limpopo system in southern Africa.

Increasing fishing effort and increasingly widespread use of small-meshed fishing nets has depleted stocks in many areas, such as the heavily-populated areas of the Barotse Floodplain on the Upper Zambezi River in Zambia. Floodplain lagoons no longer provide refugia as they are all intensively seine netted.

A commercial gillnet fishery in the Panhandle area of the Okavango Delta also targets this species.
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Vulnerable (VU) (A3e)
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Management

Conservation Actions

Conservation Actions
Nile tilapia should be urgently removed from ponds in the Upper Zambezi system in northern Zambia and replaced by O. andersonii. Attempts should be made to prevent the spread of O. niloticus and establish refuges for O. andersonii and other species.
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Relevance to Humans and Ecosystems

Benefits

Importance

fisheries: commercial; aquaculture: commercial; gamefish: yes
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Wikipedia

Oreochromis andersonii

Oreochromis andersonii, the three spotted tilapia, threespot tilapia or threespot bream, is a species of cichlid native to Africa, where it is found in rivers and swamps in the southern half of the continent. This species reaches a length of 61 cm (24 in). It is important to local commercial fisheries, as well as being commercially farmed. It is also popular as a gamefish.[2]

References[edit]

  1. ^ D. Tweddle & Marshall, B.E. 2007. Oreochromis andersonii. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 7 May 2013.
  2. ^ Froese, Rainer and Pauly, Daniel, eds. (2013). "Oreochromis andersonii" in FishBase. April 2013 version.
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