Tilapia is a member of the family Cichlidae. Three genera are well-known namely Oreochromis, Tilapia and Sarotherodon, of which nile tilapia belongs to genus Oreochromis. This species is naturally distributed in Palestine, the Nile River as well as most part of African river and lakes. It was introduced in the Philippines in 1972. It’s rising popularity is due to their hardness, resistance to diseases, ease in breeding, reasonable growth rate, good taste, and tolerance to a wide range of environmental conditions including temperature and salinities.
Taxomic Positions of Tilapia
Most tilapia species of the tribe Tilapiani now being used in aquaculture were grouped initially into one genus, Tilapia. The species within this genus were later classified according to differences in their mode of reproduction (Low McConnel; 1959 Trewawas, 1973, 1978, 1982). Species which evolved as substrate spawner but guard their eggs were retained in the genus tilapia while those which orally rear their clutches were grouped into a new species Sarotherodon. Classification of the three genera Tilapia, Sarotherodon and Oreochromis was based largely on the differences on their reproduction and feeding habits.
Classification of Tilapia Species used in Aquaculture
Genus Tilapia (Substrate spawners)
Both parents guard, protect, aerate the breed, and help move clutch to different nest sites. Fry at first feeding are 4-5 mm and show feeble swimming ability. Fry survival relatively low.
Genus Sarotherodon (Paternal/biparental)
Both parents stay close to each other. Eggs and fry brooded in oral cavity up until they are ready for release. Brood may not be collected once released. Fry are between 7-9 mm at first breeding, well developed fins for swimming. Fry survival high.
Genus Oreochromis (Maternal)
Female solely involve in brood care. After spawning, female leaves nest to rear her clutch in safety. Fry brooded up until free swimming. There is an extended period of care during which fry seek shelter in buccal cavity for safety. First feeders have well-developed fins for swimming. Fry survival high.
Sex identification of tilapia is relatively simple. The male has two openings just in front of the anal fin. The large opening is the anus and the smaller opening at the tip is the urogenital pore. The female has three openings: the anus, the genital pore, and the urinary pore. The genital papilla is usually smaller in the female. Tilapia can be sexed when it has attained the weight of 15 grams. Application of ink or dark dyes to the papillae may increase the accuracy of sexing and may allow sexing of smaller fish. By rubbing ink along the papillae of the tilapia, sexes can be readily distinguished.