Redbelly tilapia
(Coptodon zillii)

The redbelly tilapia (Coptodon zillii, syn. Tilapia zillii), also known as the Zille’s redbreast tilapia or St. Peter’s fish (a name also used for other tilapia in Israel), is a species of fish in the cichlid family. This fish is found widely in fresh and brackish waters in the northern half of Africa and the Middle East.

Elsewhere in Africa, Asia, Australia and North America, it has been introduced as a food fish or as a control of aquatic vegetation. Where introduced, it sometimes becomes invasive, threatening the local ecology and species. The redbelly tilapia is an important food fish and sometimes aquacultured.

The redbelly tilapia can reach up to 300 g (11 oz) in weight and 40 cm (16 in) in length, but usually is no more than 30 cm (12 in). In the Middle East, adults typically are 12–22 cm (5–9 in) long. Males tend to grow larger than females, but otherwise the sexes are similar.

Its base color is brownish-olivaceous and the belly is yellowish or whitish. It often (for example, when agitated) has a faint/poorly defined dark pattern consisting of two horizontal lines on the body crossed by about half a dozen vertical bars. Breeding adults are more greenish overall, have iridescent blue-green spots on the head and bright pinkish-red underparts.

This species very closely resembles the redbreast tilapia (C. rendalli) and the two are difficult to distinguish; many reports of introduced populations may involve either species. The two have separate natural distribution (redbelly tilapia in the northern half of Africa, redbreast tilapia in the southern half), but through introductions their ranges now overlap. Whether they can hybridize is unknown. It has hybridized with the spotted tilapia (Pelmatolapia mariae), a quite distant relative.

Distribution
Africa and Eurasia: South Morocco, Sahara, Niger-Benue system, rivers Senegal, Sassandra, Bandama, Boubo, Mé, Comoé, Bia, Ogun and Oshun, Volta system, Chad-Shari system, middle Congo River basin in the Ubangi, Uele, Itimbiri, Aruwimi, Lindi-Tshopo and Wagenia Falls in Democratic Republic of the Congo, Lakes Albert and Turkana, Nile system and Jordan system.

America
While cold temperatures prevent the redbelly tilapia from spreading northward, it has spread to California’s Imperial Valley, in the salty irrigation ditches and canals. Populations of redbelly tilapia are also found in Guam, Hawaii and Florida.