The present study deals with the population structure of freshwater crab May delliathelphusa. masoniana, focusing on then size frequency distribution, sex ratio, and breeding season. Crabs were randomly collected from the study area on monthly basis for a period of two years from Jan 2012 to Dec 2013. A total of 592 crabs were obtained of which 310 (52.36%) were females and 282 (47.63%) were males. The overall sex ratio comes to be 1:1.09 with considerable degree of seasonal fluctuations. The overall size frequency distribution exhibited males, females and juveniles. Sexual dimorphism was characterized by the larger sized males in relation to females. Breeding season indicated two peaks viz (June-July & Dec-Jan), with scarce young juveniles in the population.
