Spawning dynamics of female freshwater butter catfish, Ompok bimaculatus (Bloch, 1794) in different major rivers of India.

Abstract

The pattern of reproductive responses depends on unevenness in the thermal regimes of different Indian River. The objective of this study was to investigate the reproductive strategies of butter catfish Ompok bimaculatus in wild populations of Indian major rivers (Brahmaputra, Cauvery, Ganga, Godavari, Krishna, Mahanadi, Narmada, Subarnarekha, and Tapti). Changes in gonado-somatic index (GSI), ovarian protein, fecundity and ovarian histology were observed in preparatory, pre-spawning and spawning phase of reproductive cycle. The fecundity was ranged minimum to maximum in Godavari to Narmada. GSI, fecundity and ovarian protein concentration distributions were correlated significantly (P < 0.05) by linear regression analysis. The histological assessment showed that ovaries exhibited seven stages of oocyte development, which were oogonia, chromatin nucleolar, early perinucleolar, yolk granules, late perinucleolar, vitellogenesis and vitellogenic oocyte stages in all the three phases of reproduction. The observation of fish sampled from different rivers showed that Narmada River has better adaptive condition for growth and breeding of O. bimaculatus in comparison of others rivers.