Diversity of freshwater Mollusc in Maguri beel- a floodplain Wetland of Tinsukia District in Assam, India

Freshwater molluscs have great environmental significance but seem to receive less attention of biologists in the North-eastern region of India. The diversity and distribution pattern of freshwater mollusc population in Maguri ‘beel’ (Assamese: Lake) of upper Brahmaputra basin in Assam, India was assessed for two consecutive years (2014–15). A total of 26 species belonging to nine families were recorded. The families Viviparidae followed by Thiaridae and Unionidae were found to be the dominant families whereas representatives of the families Pleuroceridae and Ampullariidae were rare. Analysis of diversity indices indicated a diverse mollusc population dominated by few species, heterogeneously distributed in the study area. The assessment on the conservation status of the mollusc population revealed most of the recorded species to be in the least concerned (LC) category with unknown (UN) population trends as per the IUCN Red list status (3.1). However five species were dominant (D), three frequent (F), 16 infrequent (IF) and two rare (R) at the local context. The record of Sphaerium austeni (Prashad, 1921) which is found to be a near threatened species at global context is a key example in the assessment of local status. While overharvesting and predation pressure on fish and mollusc population are identified as the key threats to the wetland.