Introduction
Oreochromis niloticus, commonly known as the Nile tilapia, is a popular food fish that has been farmed in ponds for thousands of years. Despite its name, the Nile tilapia is not only present in the River Nile, it is native to Burkina Faso, Cameroon, Chad, Cote d’Ivoire, Egypt, Gambia, Ghana, Guinea, Liberia, Mali, Niger, Nigeria, Senegal, Sierra Leone, Sudan, Togo and Uganda.

Since Oreochromis niloticus is such an appreciated food fish it has been introduced to many other parts of the world; sometimes deliberately as a food fish or to control aquatic weed and sometimes accidently form of specimens escaping from aquacultures. Today, you can find established Nile tilapia populations on all continents except Antarctica.

The genus Oreochromis is a part of the cichlid family (Cichlidae).

Conservation status
Oreochromis niloticus has not been evaluated for the IUCN Red List of Threatened Species.

Since Nile tilapia is such a sturdy, flexible and prolific fish it can easily become a problematic invasive species when introduced to ecosystems outside its native range.

Subspecies
The Nile tilapia (Oreochromis niloticus) currently has eight recognized subspecies.

• Oreochromis niloticus baringoensis (Baringo tilapia)
• Oreochromis niloticus cancellatus
• Oreochromis niloticus eduardianus
• Oreochromis niloticus filoa
• Oreochromis niloticus niloticus
• Oreochromis niloticus sugutae
• Oreochromis niloticus tana
• Oreochromis niloticus vulcani

The two forms of tilapia referred to as Oreochromis “Kabagole” and Oreochromis”Nyabikere” and are also suspected to be variants of Oreochromis niloticus.

Habitat
Nile tilapia is an adaptable fish that can do well in wide range of habitats. It has been found in all sorts of waters, from rivers and lakes to sewage canals and irrigation channels. Despite being considered a freshwater fish it will readily adapt to brackish conditions. Its extended temperature range is 8-42 °C (47-108 °F), but it is typically found in environments where the water temperature stays in the 13.5-33 °C (56-91 °F) interval.

Feeding
O. niloticus spends most of the day feeding on phytoplankton and benthic algae, but will also happily eat higher plants. As mentioned above, it is sometimes introduced to ponds to combat aquatic weeds.

Size and appearance
The body of the Nile tilapia is decorated with regular vertical stripes that continue throughout the depth of the caudal fin. The dorsal fin margin is black or grey.

The largest scientifically measured O. niloticus specimen was 60 cm (nearly 24 inches) long.

Reproduction
Many African cichlids are mouthbrooder and the Nile tilapia is no exception. The Nile tilapia is a maternal mouthbrooder, which means that it is the mother who will keep the offspring safe inside her mouth until they are large enough to be released.

Nile tilapia in aquacultures – now and then
The oldest record of tilapia farming comes from the ancient Egyptians who raised Nile tilapia in ponds along the River Nile. They called the Nile tilapia ỉn.t and it was such an important source of food for the Egyptians that they even gave it its own hieroglyph. (It is hieroglyph K1 on Gardiner’s Sign List, a list of common Egyptian hieroglyphs compiled by Sir Alan Gardiner.)

The ỉn.t hieroglyph was used for several different purposes. As a logogram, it was reserved for Nile tilapia only, but when used as a determinative (ideogram) it could also refer to the Flathead mullet, another important food fish. When used as part of a phonogram, it represented the sound ỉn.

Today, the wild type Nile tilapia is still farmed in ponds in Africa and the Middle East where it is an important source of food for local populations. When farmed for the international fish market, most breeders will however displace the wild type Nile tilapia with a leucistic breed that has been developed for aquaculture. Unlike the wild Nile tilapia which has dark coloured flesh, the leucistic variant has fairly light meat and is therefore more popular among fish consumers in countries like the United States.

The Nile tilapia is also important for fish developers creating hybrids and strains for the industry, since it contains several desirable traits, e.g. its fast growth rate. Many modern tilapia strains today contain genetic material from O. niloticus.