Mangrove ecosystem is the main ecosystem for life activities in the coastal area, and fiddler crab is one of the fauna associated with the mangrove ecosystem. This research aims to determine the dominant habitat characteristics and calculate the diversity of the fiddler crab and analyze the factors Biotic and Abiotic of the EcosystemMangrove inSungaiRawa village, Siak regency, Riau,the purposiv…