Abstract

• The present study related to the reproductive biology of Indian mackerel, Rastrelliger kanagurta (Cuvier, 1816) was conducted from January 2021 to December 2021. A total of 360 specimens of Rastrelliger kanagurta were collected randomly to study their length-weight relationship, sex ratio, gonadosomatic index (GSI), hepatosomatic index(HSI), fecundity and stages of gonad maturity. During the study period, the sex ratio of male to female was 1:1.02. Significant correlation existed between fish length and weight in males (W = 0.0277L3.2159, R² = 0.7455) and females (W = 0.0293 L3.7046, R² = 0.7652). The highest GSI values of male and female were found in May, August, October and December, 2021. The lowest GSI values of male and female were observed in January and June, 2021. The highest value of HSI was found in March, 2021 whereas the lowest HSI value was in October, 2021 in both sexes. The GSI and HSI values were inversely correlated. Two reproductive cycles in male and female were observed with similar reproductive development. The fecundity of females varied between 2300 eggs and 78000 eggs. Total length, body weight and ovary weight were in linear relationship with fecundity. Macroscopic observation based on the appearance of the sample gonads could be classified into six maturity stages; immature, maturing1, maturing2, mature, spawning and spent. Six developmental stages of oogenesis were classified based on the chromatin nucleolus, perinucleolar, cortical alveolar, vitellogenesis, maturation and ovulation conditions. Six developmental stages of spermatogenesis were found as primary and secondary spermatogonia, primary and secondary spermatocyte, spermatid and spermatozoa. Understanding the breeding season of Rastrelliger kanagurta is a crucial necessity in obtaining scientific knowledge on artificial propagation process.