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The impact of freshwater discharges from upstream hydroelectric projects on estuarine ecology, particularly on
commercial bivalves was seldom ever studied, despite the fact that they contribute substantially to local livelihoods. Such
projects have been executed in many rivers of Indian Western Ghats unmindful of their ecological consequences. Through
a period of the past five decades, two hydroelectric projects were commissioned in the river Sharavathi of central west
coast, in the district of Uttara Kannada, Karnataka. Obvious consequences were on mangrove vegetation and fishery, and
the livelihoods of fisher-folks were also badly affected. This study in the Sharavathi estuary is with the special objective
of assessing the impact on commercial clams of incessant releases of freshwater after power production. For comparison,
the study was also carried out in the undammed Gangavali River estuary in the same district. The study covers the
diversity and distribution of commercial bivalves in relation to salinity, the key factor that expectedly gets altered due to
freshwater releases from dams. The status of bivalves was collected through primary observations, interviews with local
fisher-folks, and based on earlier studies. Whereas clam fishery involving Paphia malabarica, Meretrix meretrix, M.
casta, Tegillarca granosa, Polymesoda erosa and Villorita cyprinoides goes on rather unchanged in Gangavali estuary,
Sharavathi witnessed collapse of clam fishery, following salinity decline, indicative collapse of estuarine ecosystems
itself. All clams gathered earlier, barring a lone species Polymesoda erosa, tolerant of low salinity remained here.