Oreochromis rukwaensis (Hilgendorf & Pappenheim, 1903)
Lake Rukwa tilapia
Oreochromis rukwaensis
photo by Turner, G.F.

Family:  Cichlidae (Cichlids), subfamily: Pseudocrenilabrinae
Max. size:  33 cm SL (male/unsexed)
Environment:  benthopelagic,
Distribution:  Africa: Lake Rukwa (Ref. 2, 118630) and upper Great Ruaha River in Tanzania (Ref. 118630).
Diagnosis:  Dorsal spines (total): 15-17; Dorsal soft rays (total): 11-13; Anal spines: 3-3; Anal soft rays: 10-11; Vertebrae: 30-30. Diagnosis: Typical tilapiine cichlid, relatively deep bodied, with rather a small head (Ref. 118638). Other distinguishing characters are: caudal fin free of scales except basally; vertebrae 30; scales in lateral line series 30-32; dorsal spines XV-XVII; soft rays usually 11-13; outer teeth bicuspid, in mature fishes occasionally with a few tricuspids; lower gill-rakers 20-22; interorbital region in adults 34.5-40.0% length of head (Ref. 2). Ripe males have a dark body and fins, almost black, with bright red/orange margins on the dorsal and caudal fins; vertical barring can be noticeable in freshly caught specimens; head region in ripe males has a bluish sheen; ripe males have yellow-orange tassels; females and subadult males plain silver/grey with 6-7 post-opercular vertical stripes and bluish snout present in freshly caught specimens (Ref. 118638). Description: The teeth are in 4-6 series in specimens over 100 mm standard length, 3-4 below this size; with slender shafts and broader, curved crowns; those of outermost row bicuspid except that three mature fishes have a few tricuspids among them; inner rows tricuspid (Ref. 2). Scales on cheek in 2 rows, rarely 2 or 3 scales of a third row present; 4 or 4.5 between origin of dorsal and lateral line (Ref. 2). Caudal fin very slightly emarginate in young, truncate in adults (Ref. 2). Colouration: Preserved adults are uniformly pale, without markings on the body; the vertical fins and the pelvics are either likewise pale or may be dusky between the rays; the young are also pale, but some show 6-8 grey vertical bands on the flanks and the soft dorsal may be marked with dark oblique bands or with clear ovals on a grey ground; in this pattern the tilapia-mark may be indicated by a darker grey, but most are without even this vestige of a tilapia-mark (Ref. 2).
Biology:  This species is found both in large lakes and small rivers (Ref. 4967, 118638). A maternal mouthbrooder (Ref. 118638). Males construct territories in shallow water; where there was ample space they were similar in structure and grouping to those of Oreochromis variabilis, each territory consisting of a central raised mating platform in the middle of a large circular depression (Ref. 2). It is a major component of the fisheries catch in Lake Rukwa and the Mtera Dam (Ref. 118638). Strong aquaculture potential given broad habitat requirements (Ref. 118638). IUCN conservation status is stated as vulnerable D2, declining population trend (Ref. 118638).
IUCN Red List Status: Vulnerable (VU); Date assessed: 31 January 2006 (D2) Ref. (120744)
Threat to humans:  harmless
Country info:   

Entered by: Binohlan, Crispina B. - 20.12.90
Modified by: Boden, Gert - 25.10.18
Checked by: Sa-a, Pascualita - 31.08.94

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