van Someren, V.D.Whitehead, P.J.2015-07-032015-07-031960/1961van Someren, V.D., & Whitehead, P.J. (1961). The Culture of Tilapia Nigra (GüNther) in Ponds: VI—the Effect of Selective Cropping Methods on Breeding Populations. East African Agricultural and Forestry Journal, 26(4), 202–209. https://doi.org/10.1080/00128325.1961.116617240012-8325https://kalroerepository.kalro.org/handle/0/2042It is shown that cropping only large fish from a mixed breeding pond will in time lead to a diminution in availability of such large fish, not only because they have been cropped, but also because it leads to a greater survival of fry, which in turn leads to a denser population and therefore less growth of individual fish. The larger of the fry left under such cropping will never attain the former size of original stock fish. By contrast, cropping of fry only, leads to much greater total weight yields, though the majority of fish taken are of relatively useless trash size. It also leads, however, to a greater increase in size of the larger fish left. Cropping of mature males only on the basis of breeding colouration, these to be used for fattening in monosex ponds elsewhere, can be carried on perhaps for very long periods, since as breeding males are removed, so others colour up to take their place. Indications are that up to 44 coloured males per acre per month could thus be cropped, and such cropping does little more than reduce the normal preponderance of males in the normal sex ratio to parity with females. It probably leads also to higher fry production, and thus more males still over a long period. For the culture of good sized Tilapia nigra, therefore, a two-pond technique is recommended. In one of these, mixed breeding is allowed to occur freely; from this mixed pond, mature males are removed periodically on the basis of breeding colouration, and these are then fattened separately for marketing or consumption in another pond in which such males only are kept in monosex culture.enhttp://creativecommons.org/licenses/by/3.0/Journal ContributionTilapiaFish pondsBreedingCatch croppinghttps://doi.org/10.1080/00128325.1961.11661724