The state of Odisha (Odisha) is located between the parallels of 17° 49°N and 22° 34'N latitudes and meridians of $127°E and 87° 29'E longitudes. It is bounded by the Bay of Bengal on the cast, Madhya Pradesh on the west and Andhra Pradesh on the south. It has a coast line of about 450 kms. It extends over an area of 155,707 square kms which is about 4.87% of the total area of India. The Coastal Plains are the depositional landforms of recent stretches from the West Bengal border, ie from the River Subarnarekha in the north to the River Rushikulya in the south. The major rivers of Odisha, such as the Subamarekha, the Budhabalanga, the Baitarani, the Brahmani, the Mahanadi, and the Rushikulya are flowing through this region. It stretches along the coast of the Bay of Bengal having the maximum width in the Middle Coastal Plain (the Mahanadi Delta), narrow in the Northern Coastal Plain (Balasore Plain) and narrowest in the Southern Coastal Plain (Ganjam Plain). The North Coastal Plain comprises the deltas of the Subarnarekha and the Budhabalanga. The Middle Coastal Plain comprises the compound deltas of the Baitarani, Brahmani and Mahanadi rivers. The South Coastal Plain comprises the laccustrine Plain of Chilika Lake and the smaller delta of the Rushikulya River.

The estuarine systems of Mahanadi, Brahmani, Baitarani, Subarnarekha, Rushikutya, Bhidhabalang etc. are extensive and supporting rich aquatic biodiversity inaddition to providing many ecological services. These estuaries providing valuable commercial resources like fishes, molluscs, crabs, prawns, shrimps, etc. to the people of rural areas settled around and offering many livelihood options. The biodiversity studies made on these estuaries is vesry scanty. The studies on Mahanadi estuary by Upadhyay (1988), David (1953), Rao (1964), Jayaram and Majumdar (1976), Thakur (1970), Shetty (1963), Shetty et al. (1965), Venkactswatlu et al. (1993a, 1993b, 1993c, 1993d, 1993e) and Deb, (1998); estuarine part of Paradeep and Astaranga by Vekateswaralu et al. (1998), Rushikulya Estuary by Rao et al, (1992) and on Bahuda Estuary by Rath and Dev Roy (2011), Brahmani-Baitarani estuarine system by NGO, Greenpeace India (2007) and by Rao and Shibanada Rath (2012) are notable. But no studies on Budhabalanga estuary have been made so far. Keeping in view of the paucity of studies, the authors made an attempt to study the faunal composition w.sr to fishes and crustaceans of the Budhabalanga: estuary. The studies revealed the occurrence of 121 species of fish, 31 species of crustaceans (17 species prawns; 14 species crabs), 15 species of gastropods and 6 species of bivalves in the estuary About 24 species of fishes (marked with Astrisk in the systematic list) are found to be first distributional record to the estuaries of Odisha.

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