Speckled s hrimp (Metapenaeus monoceros ) represents an important shrimp in the penaeid group of crustaceans and form one of the major components of exploited marine fishery resources in Karnataka which have good domestic and export demand. The reproductive study of M. monoceros was carried out from November, 2016 to May, 2018 . A five-stage classification for ovaries of female shrimp was adopted for describing the gross maturity stages. Based on the gross examination of gonads, microscopic observation and gonado-somatic index (GSI) the spawning season appears to extend throughout the year with peak from March to May and the secondary peak in November. The Gonado-Somatic index values for male ranged from 1.023 to 6.395, whereas for female 4.854 to 9.412 . Although the peak during South-west monsoon has been observed during the course of the present study, the presence of the secondary peak is discernible in the samples obtained from Mangaluru waters. It can be conclusively inferred that M. monoceros breed throughout the year as evidenced by the appearance of all the maturity stages in most of the months during the study period.
The fecundity ranged from 86,251 to 4,05,264 with an average of 2,25,206 ova and observed that fecundity is in direct proportion to the total length, total weight and ovary weight. The ova diameter mode ranged from 0.0512 mm to 0. 3248 mm. Studies on the size at first maturity revealed that females of the species mature at a smaller size than males. It can be concluded that speckled shrimp spawn more than once in a lifetime, since mature shrimps were seen in all the length groups from size at first maturity onwards and also throughout the season. The ovaries in the maturing and mature stages, encountered in the present study, had two widely separated groups of ova- one representing immature stock and another one maturing stock. This indicates that the spawning of individuals of the species is restricted to a short and definite period. The analysis of sex ratio indicate that females are more dominant than males in the population during almost all the months of the study period. However, during August to November 2017 the sex ratio is near to 1:1. This can be attributed to the fact that males move out of the fishing ground to the deeper water for spawning and that the breeding and fishing grounds for females is same. The results of sex ratio as analysed by Chi-square analyses for the homogeneity of sex ratio revealed that the season and sex are independent (p < 0.05).