Conclusion

Estuaries although ranked among the highest productive ecosystems of the earth, have not merited to this day enough attention to safeguard their ecological integrity due to ever increasing anthropogenic interventions along the coastal zones in general. The fact notwithstanding that estuarine productivity is sustained naturally without any inputs from humans, unlike in agricultural ecosystems or fish farming systems, most estuaries, of the Indian west coast are subjected to increasing stress from humans.

Salinity changes due to dams constitute a single major factor that can undermine estuarine ecology. The current study clearly shows that the lowered salinity in the Kali River estuary, due to the constant release of freshwater from hydroelectric projects upstream, has seriously impacted the bivalves that constituted an abundant food resource from the estuary. The distribution zones of most such bivalve species have become narrower than in the pre-dam scenario, shifting more towards the estuarine mouth to whatever relatively safer salinity zones available, due to the constant onrush of freshwater from hydel projects upstream. Such major habitat shifts and shrinkage happened in the cases of Meretrix meretrix, M. casta, Villorita cyprinoides, and estuarine oysters and near decimation happened for yet another bivalve Paphia malabarica. The surviving bivalves themselves appear to be combating with low salinity conditions in their present occupation zones as well, and their diminished availability has affected the livelihoods of traditional bivalve collectors and the consumers of bivalves, bulk of whom are from the poorer segments of the coastal society. The study, while clearly establishing that the execution of hydel projects in the Kali River has adversely affected the estuarine commercial bivalve community as a whole, also implies that through upsets in salinity regimes a state of the imminence of ecosystem collapse could be happening not merely for bivalves, but also involving fishes, and shrimps and even mangroves.