Reproductive Biology of Two Fresh Water Fishes, Ompok Bimaculatus and O. Malabaricus (Bloch) of the River Amaravathy, Tamil Nadu, India

ABSTRACT

O. bimaculatus and O. malabaricus are found to  breed throughout the year with significant increase during specific time, supported by ova diameter studies, seasonal occurrence of maturity stages, gonado-somatic index and relative condition factor (‘Kn’). Individuals of O. bimaculatus and O. malabaricus   seem to spawn once in a breeding season.  The spawning peaks for O. bimaculatus (September) and for O. malabaricus (July) are confirmed by the occurrence of high percentage of fully mature specimens and a rise in  ‘Kn’ values, during the respective months. 50% of males and females of O. bimaculatus   seem to mature in the size range of 200-210 mm and 189-199 mm, respectively, which is attained at the end of the second year or at the beginning of the third year.  In O. malabaricus, 50% of males in the 333-353 mm size group and females in 328-348 mm size group attain maturity at the age of the second year.