Principles of Genetics and Breeding

14.1.6. Domestication in tilapia

The group of cichlids termed tilapias includes morethan 100 species divided among several genera or subgenera according to the method of classification used.

Tilapias are indigenous to most parts of Africa, and eastern Mediterranean areas as far north as Syria. They have been introduced to many areas within the 20⁰C winter isotherms, particularly in Latin America and South East Asia.

Aquaculture of the Nile tilapia (O. niloticus) in ancient Egypt goes back almost as far as carp culture in China, but there are no known records of the importance or longevity of this practice. Their domestication is of recent origin and is “still very much in its infancy.” According to the definition of domestication used here, tilapias are under domestication in all areas outside their natural distribution in which they are grown and reproduced. An extreme example is Southeast Asia, where the majority of the tilapia yield is produced.

The most prevalent species is O. mossambicus, progenies of five individuals which appeared in Eastern Java in a mysterious manner in 1939, from where they spread rapidly and were distributed as the “Japanese fish”.

Other tilapia species were introduced later e.g., O. niloticus to Taiwan, for crossbreeding with the established O. mossambicus. Similarly, O. hornorum has been introduced to countries outside its native Zanzibar due to its ability of fathering all-male hybrid broods with O. mossambicus and O. niloticus females.

The reproduction of these introduced species and species combinations in captivity in isolation from their wild ancestral population is the beginning of their domestication.

Whether this process has been instrumental in adapting tilapias to aquacultural environments is unknown, since no comparisons between wild stocks and those under domestication have been carried out. It is even possible that stocks under this kind of domestication perform not as well in captivity than wild (undomesticated) stocks of the same species due to inbreeding and genetic drift resulting from a small number of individuals in a given introduction, or unconscious selection of inferior stock.

In recent years, strains of red tilapias have been isolated in different countries such as Taiwan, Philippines, and the U.S. Their price is higher than that of normally colored tilapias and in Taiwan they are grown commercially for export to Japan.

Red individuals also occur sporadically in O. aureus and O. niloticus in natural and captive populations and are largely eliminated by natural selection. Populations produced from these red individuals should therefore be regarded as domesticated. Although most domesticated strains usually perform better in the aquaculture environment than wild strains, there are exceptions, e.g. wild Nile tilapia grow better in the aquaculture environment. Poor performance of some domesticated strains is related to poor founding (parental) lines, random genetic drift, inbreeding and introgression with slower growing species, such as O. mossambicus and O. niloticus.