Oreochromis urolepis hornorum

The Wami tilapia and Rufigi tilapia were once considered separate species, but they have now been merged and the current scientific name for Wami tilapia is Oreochromis urolepis hornorum. (The scientific name for Rufigi tilapia is Oreochromis urolepis urolepis.) In older sources, you the name Tilapia hornorum is used for Wami tilapia. The common name of this fish, Wami tilapia, is derived from the Wami River. 

Wami tilapia is an African cichlid native to Uganda and Tanzania. The fish can also be found on Zanzibar but it remains unclear whether this is an introduced population or not. Wami tilapia has been introduced by man to many parts of the world you can for instance encounter established populations in such diverse locations as the United States, Brazil, Cote d'Ivoire, Slovakia, Japan and Fiji. Oreochromis urolepis hornorum has not been evaluated for the IUCN Red List of Threatened Species.

The largest scientifically measured Wami tilapia was 24 cm (9.5 inches) long. In mature males the jaws grow really big which gives the fish a concave upper profile. Mature males are almost completely black with lips that are pale or black. The margin of the dorsal fin and the margin or upper half of the caudal fin is bright red, orange or pink. Females and non-breeding males are not as dramatically coloured; they are steel grey or silvery with 2-4 mid-lateral blotches.

The Wami tilapia lives in both freshwater and brackish environments. It can for instance be found in saline ponds on Zanzibar. It feeds on detritus (decomposing organic matter), algae, plants and small invertebrates. It is a tropical species that prefers a water temperature around 22-26 degrees C (72-79 degrees F).

The Wami tilapia is kept in aquariums and grown in aquacultures. Its minimum population doubling time is less than 15 months. The Wami tilapia is normally not a territorial species, but it can be occasionally. It is a popular food fish, especially in Africa. Wami tilapia can mate with Mozambique tilapia (Oreochromis mossambicus) and produce hybrids. The hybrid batches will contain no or very few females. This skewed sex ratio is highly appreciated by fish farmers since male tilapias grow faster and reach a more uniform size than females. Keeping only one sex will also save fish farmers from having to deal with large amounts of tilapia fry in their growing units.  

Mitochondrial DNA studies carried out by Nagl et al in 2001 yielded some surprising results. According to this study, the Wami tilapia might actually belong to the genus Sarotherodon instead of Oreochromis. The same seem to be true for its closest relatives in the genus Oreochromis, e.g. the Rufigi tilapia (Oreochromis urolepis urolepis) and the Blue tilapia (Oreochromis auerus). The Mozambique tilapia (Oreochromis mossambicus) does on the other hand not seem to be closely related to the Wami tilapia. There are several possible explanations for these results. One is of course that the Wami tilapia and its closest relatives have been erroneously placed in the genus Oreochromis when they should actually have been placed in Sarotherodon. Another alternative is that they have ancestors that mated with the ancestors of the fish in the genus Sarotherodon, producing fertile hybrids.