Oreochromis mossambicus (Peters, 1852)

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 793-795

Oreochromis mossambicus

Common name. Mozambique tilapia.

Diagnosis. Distinguished from other species of Cichlidae in West Asia by: ● nuptial male black or dark-grey with whitish lower part of head / ● snout duck-bill-like elongated in male larger than 200 mm SL / ○ orange or red dorsal- and caudal margins in nuptial male / ○ tip of membrane between dorsal spines orange or red / ○ caudal with small spots or blotches not forming regularly shaped and set bars / ○ all flank scales with dark-grey scale pockets in preserved individuals, dark-grey scales pockets never organised in fields / ○ center of flank scales above lateral midline, sometimes also below, darker than scale pockets / ○ anterior processes of lower pharyngeal bone clearly projecting beyond anterior margin of toothed pads / ○ chest, belly, and isthmus in front of pelvic covered by small scales / ○ 3 anal spines / ○ scales cycloid / ○ no ocelli on anal. Size up to 350 mm SL.

Distribution. Introduced in Saudi Arabia (details unknown) and in Yemen, locally introduced in UAE but not recorded from Oman . A non-native population in Algeria. Native to lower Zambezi, lower Shire, and coastal plains from Zambezi Delta to Algoa Bay. Occurs south to rivers in Eastern Cape and Transvaal to Limpopo. Widely introduced beyond this range into inland areas and south-western and western coastal rivers, including lower Orange River and rivers of Namibia. Introduced for aquaculture, escaped and established in tropical countries worldwide.

Habitat. Various standing and slow-flowing waters include coastal lakes, lowland rivers, streams, drains,

reservoirs, and marshes, usually over muddy bottoms, often in well-vegetated areas. Fresh to marine waters, can survive in hypersaline waters. Spawns only in fresh and brackish waters of low salinity, along shorelines in stagnant or slow-flowing waters, and on sandy or muddy bottoms.

Biology. Lives up to 11 years. Females usually begin spawning at about 120 mm SL, but in dense populations, at 60–70 mm SL and about 2 months. Territorial males excavate and defend a basin-shaped burrow in center of their territory, where they spawn with females. Often forms leks in dense colonies. Females only visit pits to spawn. Male actively courting female to nest in pit. Territorial males produce sounds during all stages of courtship, but especially during late stages, including spawning. Subordinate males without territory may adopt pseudo-female behaviour and sneak into nests during spawning. Female lays 100–1700 eggs in multiple portions. Female take eggs in their mouths as they are laid, before, during, or after fertilisation. No permanent pair bond formed; females incubate eggs alone while males court other females. Females may spawn a full clutch with one male or several males in a series so that siblings have different fathers. Females do not feed during brood care or take small food items, some of which are eaten in mouth by juveniles. Water is circulated over eggs by chewing movements of female’s jaws. Fry hatch in female’s mouth after 3–5 days, depending on temperature. Juveniles are released 10–14 days after spawning. Female guards fry, encouraging them to enter her mouth if threatened, for about 3 weeks. Juveniles swarm in shallow water and feed during day, retreating to deeper water at night. Females produce several broods in a season. Non-spawning individuals, as well as mouth-brooding females, gregarious along shores. Can tolerate temperatures ranging from 8 to 42°C; natural temperature range is 17–35°C. Tolerates low dissolved oxygen levels and utilises atmospheric oxygen when aquatic oxygen levels drop. Omnivorous, feeds mainly on algae and phytoplankton.

Conservation status. Non-native; released for mosquito control. NT in its native range, threatened by hybridisation with non-native Oreochromis niloticus .

Remarks. While this species was of great importance in aquaculture and is one of the best-studied freshwater fishes in the world, it is now largely replaced by O. niloticus and O. aureus . Further reading. Crass 1964 (biology); Pienaar 1978 (biology); De Silva & Chandrasoma 1980 (reproduction); Pullin & Lowe-McConnell 1982 (biology, reproduction); Gregg et al. 1998 (hybridisation); Fuselier 2001 (ecological

Wadi Bani Khalid in Oman is full of non-native Taiwanese red tilapia.

impact of invasion); Skelton 2001 (native distribution, biology); Allen et al. 2002 (habitat choice in Australia); Amorim et al. 2003 (sound production).

Oreochromis niloticus ; Fossa Calda, Italy; ~ 200 mm SL.