Genus of fishes
Oreochromis is a large genus of oreochromine cichlids, fishes endemic to Africa and the Middle East. A few species from this genus have been introduced far outside their native range and are important in aquaculture. Many others have very small ranges; some are seriously threatened, and "O. ismailiaensis" and "O. lidole" possibly are extinct. Although "Oreochromis" primarily are freshwater fish of rivers, lakes and similar habitats, several species can also thrive in brackish waters and some even survive in hypersaline conditions with a salinity that far surpasses that of seawater. In addition to overfishing and habitat loss, some of the more localized species are threatened by the introduction of other, more widespread "Oreochromis" species into their ranges. This is because they—in addition to competing for the local resources—often are able to hybridize.
"Oreochromis" are fairly robust fish, and medium–small to very large cichlids that can reach up to in total length depending on the exact species.
Taxonomy.
Species in this genus, as well as those in several other oreochromine and tilapiine genera, share the common name "tilapia" and historically most were included in the genus "Tilapia".
"Oreochromis" contains more than 30 species, and several undescribed forms exist. Judging from mtDNA sequence analysis, several clades seem to exist. Research is hampered because hybridization runs rampant in these fishes, which confounds mtDNA data (Wami tilapia is an example), and the fast speed of evolution makes choice of appropriate nuclear DNA sequences difficult. A comprehensive genetic study that included almost all the species, as well as the closely related "Alcolapia", found that "Oreochromis" as currently defined is paraphyletic. For example, two "Oreochromis" species ("O. amphimelas" and "O. esculentus") appear closer to "Alcolapia" than the remaining "Oreochromis", and five other "Oreochromis" species ("O. angolensis", "O. lepidurus", "O. niloticus", "O. schwebischi" and "O. upembae") appear to be as distant from the "core" "Oreochromis" as they are from "Alcolapia". A potential solution is to merge "Alcolapia" into "Oreochromis", as done by Catalog of Fishes.
Species.
The 37 recognized species in this genus are:
Gallery.
 Media related to at Wikimedia Commons
References.
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