The Amazon dolphin (Inia geoffrensis), Ganges dolphin (Platanista gangetica), and Indus dolphin (Platanista minor) are freshwater cetaceans who depend on habitats threatened by dam infrastructure that alter hydrological regimes and impairs riverine ecosystems.
In this study, researchers combined occurrence records of the three dolphins from literature and databases, including GBIF. Employing a density plot analysis based on environmental and alteration variables along the occurrence records they studied the effects of physiographic and hydrologic factors on dolphin distributions.
Their analysis showed that all three species preferred confluences—areas where two or more streams join together to form a single channel—and winding rivers segments. Amazon and Ganges dolphins mainly occupied smaller third-order tributaries while Indus dolphins tend to stay in the mainstem of the rivers.
Examining 147 specific cases of hydrological alterations, the authors found most caused by barrages, or diversion dams, in the ranges of Ganges and Indus dolphins, and embankment dams in the range of Amazon dolphins.
While the authors did identify one example of an impoundment upstream of a barrage improving conditions for Ganges dolphins, most other reported structures had negative impacts on dolphins due to either habitat fragmentation or reduction.