The Malacca tilapia hybrids

Abstract

1. An un-named Tilapia belonging to themossambica group has been imported from Zanzibar and crossed with theTilapia mossambica Peters which has become acclimatised in Malaya. 2. Where an African male was mated with a Malayan female fish, the offspring were all males, or nearly so. 3. Where a Malayan male was mated with an African female, the offspring tended to show approximately a Mendelian sex-ratio of three males to one female. 3. Whereas the broods produced in the cross Malayan male by African female tended to be fewer than those produced by the pure-bred fish, the all-male broods resulting from the cross African male by Malayan female did not contain fewer fingerlings than the broods resulting from the crossing of pure-bred fish, in which there are about equal numbers of male and female fingerlings. 4. Therefore, the all-male broods are not the result of some lethal factor which inhibited the development of the females, but of a genetical mechanism probably similar to that in the Platyfish as described by Gordon. 5. The practical implications of the ability to breed fingerlings almost wholly of one sex, for the purpose of stocking commercial fishponds, are briefly stated.