Oreochromis aureus (Steindachner 1864)

Diagnosis: Adults: narrow preorbital bone (depth max. 21.5% of head length in fishes up to 21.3cm SL); lower pharyngeal jaw with short blade; no enlargement of the jaws in mature fish (lower jaw not exceeding and usually less than 36.8% head length) (Ref. 2). Caudal without regular dark vertical stripes (Ref. 2, 53405, 54467), but with a broad pink to bright red distal margin (Ref. 2). Breeding males assume an intense bright metallic blue on the head, a vermilion edge to the dorsal fin and a more intense pink on the caudal margin (Ref. 2, 54467). Breeding females with the edges of dorsal and caudal fins in a paler more orange color (Ref. 2). Juveniles: upper line of head profile running upward from snout at sharp angle; lower pharyngeal bone nearly triangular, teeth numerous but not densely crowded; dorsal and anal fin striped, with stripes running obliquely on the soft dorsal and longitudinally on the caudal fin; black Tilapia-mark on soft dorsal present; body dark; lower lip developed from beneath (Ref. 54566).Description: deep bodied; teeth very small, typical for an algae feeder (Ref. 52307), in 3-5 rows in the jaws, bicuspid in the outermost (Ref. 2, 53405, 54467), tricuspid in the others (Ref. 2, 54467). Lower pharyngeal bone with bicuspid teeth, its toothed part as long as anterior part (Ref. 53405). Scales cycloid (Ref. 367, 2756, 54408), with fringes of the embedded part almost straight (Ref. 54408). Scales on cheek in 2-3 horizontal series; 5-7 scales between base of pectoral and pelvic fin (Ref. 2, 54467). 13.5-14.5 scales below upper lateral line before the pelvic fins (Ref. 367). 2 scales between upper and lower lateral line (Ref. 367, 2756). Upper lateral line with 20-23 scales, lower with 14-18 scales (Ref. 367, 2756). Microbranchiospines present on outer sides of arches 2 to 4 (Ref. 2). Dorsal fin edge thickened and notches between lappets closed in fully ripe males (Ref. 364, 54467). Last dorsal spine the longest (Ref. 367, 2756). Third anal spine a little shorter than last dorsal spine (Ref. 2, 2756, 54467), but stronger (Ref. 2, 54467). Pelvics not greatly produced; caudal often with rounded corners, usually scaly only at the base and between rays on upper and lower parts of the fin; genital papilla of mature male conical or with narrow bifid flange (Ref. 2, 54467).Coloration: Juveniles: grey-brown to slightly golden (Ref. 52307), with vertical bars on sides (Ref. 53405). Specimens

Saccocoelioides Infection. Parasitic infestations (protozoa, worms, etc.)

Goezia Disease 2. Parasitic infestations (protozoa, worms, etc.)

Gnathostoma Disease (larvae). Parasitic infestations (protozoa, worms, etc.)

Ichthyobodo Infection 2. Parasitic infestations (protozoa, worms, etc.)

Whirling Viral Disease of Tilapia Larvae. Viral diseases

Sanguinicola Disease. Parasitic infestations (protozoa, worms, etc.)

Centrocestus Disease. Parasitic infestations (protozoa, worms, etc.)

Nesting usually in shallow water weedy areas (Ref. 96). Males establish territory and dig a spawning pit (Ref. 2, 6465, 54601), using mouth and fins (Ref. 2), up to 60cm deep and 4-6m in diameter; a number of territories can often be found clustered together (Ref. 52307). Territories are defended by means of agressive behaviour (Ref. 6465), including lateral display, lateral biting and mouth-to-mouth combat (Ref. 2). Reproduction is stimulated by long photoperiods and inhibited by short daylengths (Ref. 54365). Reproduction requires a minimum temperature of about 20°C (Ref. 2). Males visit schools of females and attempt to attract a female spawning partner (Ref. 2, 52307). Courting behaviour in the nest consists of lateral display by both sexes with nipping and tail-flapping (Ref. 2). Eggs are deposited in single clutches, from several dozen to 100 eggs (Ref. 52307), and are taken into the females mouth as soon as they are fertilized (Ref. 2, 6465, 52307), with a peak spawning frequency around the 9-11th hour of light (Ref. 31140, 54365). One female may hold up to 2000 eggs in her mouth (Ref. 2). The female swims away to deeper water with the brood after spawning is complete (Ref. 2, 52307), while the male renews spawning activities with another female. Hatching occurs about 3 days after oviposition (Ref. 2). Incubation time varies with temperature, 13-14 days at 25-27°C (Ref. 2, 52307) or 8-10 days at 29°C (Ref. 144), and juveniles leave the mother's mouth when they are about 1.1cm in length (Ref. 54601). The young school near parent's head for a few days, reentering the mouth at any sign of danger or at a gesture of the female; parent-offspring relationship ceases after 5 days (Ref. 2).

Potamodromous. Migrating within streams, migratory in rivers, e.g. Saliminus, Moxostoma, Labeo. Migrations should be cyclical and predictable and cover more than 100 km.

Dorsal spines (total): 14 - 17; Dorsal soft rays (total): 11 - 15; Analspines: 3; Analsoft rays: 8 - 11; Vertebrae: 28 - 31

Cold tolerant (Ref. 61), occuring at temperatures ranging from 8°-30°C, with small size fish less tolerant to low temperatures than larger specimens (Ref. 2). Tolerates fairly brackish conditions (Ref. 3, 61, 2001, 6465, 54362), with small specimens less tolerant than larger ones (Ref. 96, 54403, 54459) and ontogenetic changes in salinity tolerance related to body size rather than to chronological age (Ref. 54403, 54459). Forms schools; is sometimes territorial; inhabits warm ponds and impoundments as well as lakes and streams (Ref. 5723, 11028), in open water as well as among stones and vegetation (Ref. 11028). Omnivorous (Ref. 61, 52307), but with a tendency towards a vegetarian diet (Ref. 52307). Feeds on phytoplankton and small quantities of zooplankton (Ref. 3, 61, 6465, 52307). Young fish have a more varied diet which includes large quantities of copepods and cladocerans (Ref. 2, 61, 6465), but they also take pieces of small invertebrates (Ref. 52307). Particulate feeder during larval and juvenile stages, filter feeder when adult (Ref. 46977). Ovophilic, agamous (Ref. 52307), maternal mouthbrooder (Ref. 364, 52307). Reproduces in both fresh and brackish water (Ref. 61, 5723).

Cold tolerant (Ref. 23, 61, 55352), occuring at temperatures ranging from 8°-30°C (Ref. 2), tolerating up to 41 °C (Ref. 23). Tolerates fairly brackish conditions (Ref. 3, 23, 61, 2001, 6465, 54362). Forms schools; is sometimes territorial; inhabits warm ponds and impoundments as well as lakes and streams (Ref. 5723, 11028), in open water as well as among stones and vegetation (Ref. 11028). Feeds on phytoplankton and small quantities of zooplankton (Ref. 3, 61, 6465, 52307). Young fish have a more varied diet which includes large quantities of copepods and cladocerans (Ref. 2, 61, 6465), but they also take pieces of small invertebrates (Ref. 52307). Ovophilic, agamous (Ref. 52307), maternal mouthbrooder (Ref. 364, 52307). Sexual maturity in ponds reached at age of 5-6 months (Ref. 55352). Reproduces in both fresh and brackish water (Ref. 61, 5723). Good taste (Ref. 61).

fisheries: highly commercial; aquaculture: commercial; aquarium: commercial; bait: usually