Oreochromis

Freyhof, JÖrg, Yoğurtçuoğlu, Baran, Jouladeh-Roudbar, Arash & Kaya, Cüneyt, 2025, Handbook of Freshwater Fishes of West Asia, De Gruyter : 789-790

Oreochromis

Oreochromis comprises approximately 20–40 species, depending on the generic concept. Most Oreochromis are found in East Africa, although two are native to West Asia. Some authors have recognised Alcolapia , Neotilapia, Nyassalapia , and Vallicola as valid genera. Still, molecular studies have challenged the generic concept of mouth-brooding tilapias, and these may ultimately be reclassified as Oreochromis . The phylogeny of Oreochromis also shows widespread discordance between nuclear DNA and mitochondrial DNA trees. It seems premature to propose a revision of mouth-brooding tilapias, which are unlikely to form a natural group.

Several Oreochromis species are attractive targets for aquaculture, with at least eight species actively farmed globally, many in warm-water farms. Oreochromis niloticus and its hybrids are the most widely farmed aquaculture warm-water species globally. Additionally, in certain West Asian regions, an expanding aquaculture industry is cultivating primarily hybrid tilapia ( O. niloticus x O. aureus ). Other tilapias, including Oreochromis niloticus , O. aureus , and O. mossambicus , as well as hybrids between O. mossambicus and O. niloticus (Taiwanese red tilapia), are maintained in experimental farms and are cultivated in limited quantities before being released

into natural waters. Oreochromis spilurus , a salt-tolerant species, was introduced from Kenya to Saudi Arabia and was reportedly bred and cultured in saline waters of the Red Sea. While it cannot be ruled out that fish have escaped and established themselves in the Red Sea basin, there is no evidence to confirm this. Therefore, O. spilurus has been excluded from the list of non-native species in Arabia.

A few Oreochromis from Oman have been studied for their mitochondrial molecular characters. The results suggest that either O. niloticus has already hybridised with O. mossambicus in Oman or that the introduced fish had already been hybridised, and these Omani populations might be feral Taiwanese red tilapia. Phenotypically, these fish are close to O. niloticus . Introgressed mitochondrial DNA is a trace of past hybridisation events. The aquaculture industry has a significant environmental impact, as fish inevitably escape and potentially establish local populations. This has occurred locally in West Asia, where Oreochromis have become invasive in the Persian Gulf basin and the Levant. Many species of Oreochromis have a substantial invasive potential, and four species are currently listed on the Global Invasive Species Index. Further reading. Genner et al. 2013 (invasion); Shechonge et al. 2019 (invasion); Ford et al. 2019 (phylogeny); IUCN 2020 (invasive species list).

Oreochromis spilurus ; Kenya, male, 150 mm SL. Oreochromis aureus ; Ceyhan drainage, Türkiye; ~ 200 mm SL.