Morphology Data of Oreochromis niloticus
Identification keys
Abnormalities
Main Ref. Trewavas, E., 1983
Appearance refers to Male; Female
Bones in OsteoBase Skull, Spine

Sex attributes

Specialized organs
Different appearance different morphology during breeding season only
Different colors different colors during breeding season only
Remarks

Descriptive characteristics of juvenile and adult

Striking features none
Body shape lateral fusiform / normal
Cross section compressed
Dorsal head profile more or less straight
Type of eyes more or less normal
Type of mouth/snout more or less normal
Position of mouth terminal
Type of scales cycloid scales
Diagnosis

Diagnosis: A large deep-bodied tilapia, with a relatively small head (Ref. 118638). Jaws of mature male not greatly enlarged, length of lower jaw 29-37% of head length; genital papilla of breeding male not tassellated (Ref. 2). Body depth 36-50% of SL (Ref. 28714). Most distinguishing characteristic is the presence, at all life stages, of regular vertical stripes throughout depth of caudal fin (Ref. 4967, 53405, 118638). In smaller fishes, these are relatively wide and form an arc, and start at the base of the caudal fin (Ref. 118638). Males are bluish pink, sometimes with a dark throat, belly, anal and pelvic fins; females are usually brownish, silvery/white beneath with around 10 thin vertical bars (Ref. 118638).

Description: Lower pharyngeal bone longer than broad, its anterior part longer than toothed part; outer jaw teeth bicuspid, inner jaw teeth tricuspid, posterior pharyngeal teeth bicuspid and stout; 3-4 rows of teeth in jaws (3-5, rarely 6, in specimens over 200 mm SL); micro-gillrakers present; scales cycloid (Ref. 53405).

Coloration: margin of dorsal fin grey or black; vertical bars in caudal fin 7-12 (Ref. 2). Regular black cross bars on caudal fin; ground colour greyish, relatively dark in adults; back olivaceous-green, sides paler, with 6-9 rather indistinct cross bars; belly whitish; upper lip pale green or white, lower lip white; dorsal and anal fins greyish, sometimes with very narrow red margin, soft part of fin with vertical lines (or with aligned light spots resembling striped pattern); pelvic fins grey, pectorals transparent; "tilapian" spot lacking in adults but very distinct in fingerlings which also have more distinct cross bars and very prominent black spot on upper part of caudal peduncle; throat, belly and unpaired fins black in mature males (Ref. 53405). Head and trunk in breeding male suffused with red (Ref. 28714).

Ease of Identification

Meristic characteristics of Oreochromis niloticus

Lateral Lines 1 Interrupted: No
Scales on lateral line 31 - 34
Pored lateral line scales
Scales in lateral series
Scale rows above lateral line 4 - 5
Scale rows below lateral line
Scales around caudal peduncle
Barbels 0
Gill clefts (sharks/rays only) absent
Gill rakers
on lower limb 18 - 28
on upper limb
total
Vertebrae
preanal
total 30 - 32

Fins

Dorsal fin(s)

Attributes extending over most of the back length
Fins number 1
Finlets No. Dorsal   0 - 0
Ventral  0 - 0
Spines total 15 - 18
Soft-rays total 11 - 13
Adipose fin absent

Caudal fin

Attributes more or less truncate; more or less normal

Anal fin(s)

Fins number 1
Spines total 3 - 3
Soft-rays total 9 - 11

Paired fins

Pectoral Attributes  more or less normal
Spines     
Soft-rays   
Pelvics Attributes  more or less normal
Position    thoracic  beneath origin of D1
Spines     1
Soft-rays   
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