The Ganga River was host to one of the world’s largest and most diverse fish populations, accounting for more than 20% of all freshwater species found in India. However, the development of huge bridges, dams, barrages, and hydro-projects significantly altered river flows. The fragmentation of hydrological connectivity between rivers and wetlands, riverfront development, alarming levels of pollution, extensive sand mining, and unregulated overexploitation of fish resources are the primary causes of Ganga’s fish resource decline. The fish capture per kilometre length of the river has declined dramatically over time, and the species composition has altered more in favour of nonmajor carp and other species. Numerous alien fishes have also colonised the environment in favourable areas where flows have been drastically reduced as a result of water removal from the main river. Aside from changing climatic circumstances, altered hydrology has had a crucial role in transforming the river’s fisheries scenario. Several studies of data collected over time revealed poor water quality at stressed locations due to the presence of heavy metals, pesticide residues in river water, and silt, which are also factors in the loss of fish species in the Ganga. Many fish species have become extinct in various parts of the river. This alteration has also had an impact on the income of riparian fishermen.