Studies on Trilapia nilotica Linnaeus, T. mossambica Peters, and Their Hybrids

Abstract

Two species of Tilapia (T.nilotica. and T. mossambica.) and their hybrids were studied to determine the rate of growth, the net production, the sex-ratio, and the variations in the morphometric and meristic characters. The growth rate in average total length was just the same among their hybrids and selfing T.nilotica, but they grew significantly faster than selfing T.mossambica. When the average weight was considered, the hybrid of male T.nilotica and female T. mossambica had the highest growth rate, followed by the another hybrid and selfing T.nilotica respectively. Selfing T. mossambicd had the lowest growth rate. The net production of the hybrid of male T.nilotica and female T.mossambica was only significantly than those of selfing T.nilotica and selfing t.mossambica. The ratio of male and female was 2:1 for selfing T.nilotica, 1:1 for selfing T.mossambica, 5:2 for the hybrid of male T. nilotica and female T. mossambica, and 3:2 for the hybrid of male Y.mossambica and female T.nilotica. The best morphometric and meristic characters for segregating those species were : a) The number of gill rakers. b) The number of lateral stripes, and c) The black and light yellow stripes on the dorsal, anal, and caudal fins.