Gonad Maturation and Fecundity of a Fish with Partial Spawning (Tilapia nilotica L.) PDF

Keywords

Fish eggs, Egypt, oocytes

Abstract

Samples of ovaries of Tilapia nilotica collected monthly from Lake Manzalah (Egypt) confirm that the female lay eggs in batches, hence is partial spawner. The number of such batches varies from 4 to 5. The nearly ripe eggs are pear shaped, surrounded by a thick layer cytoplasm directly beneath the outer covering layer (oolemma). A peculiarity of oogenesis of T. nilotica is the continuous resorption of oocytes in different stages of maturation, even up to the times of ripening. Resorption occurs not only during trophoplasmic growth but also during the period of protoplasmic growth. Reduction in egg number by consecutive resorption greatly affects the calculation of final fecundity. Percentages of resorption and consequently the decrease in the number of oocytes in each stage are correlated primarily with the size of oocytes and also with the size of the ovary itself and finally with size of each batch ready to shed.