Biodiversity is basic for adjustment of a biological system, ensuring of general condition, quality and for understanding the natural worth of all species on earth. The fish fauna diversity has its significance like other aquatic and terrestrial animals. Water is an elixir of life; it is the source of energy, govern the evaluation and function of the universe on the earth. The water resources, which hold the biological life, have undergone considerable change in its quality on account of interference by the human and natural phenomenon. This is more specific to the Himalayan region on the account of fast-changing climatic and natural phenomenon. In past, construction of dam or barrages across on many rivers for hydroelectric power generation, irrigation, and navigation purposes have interfered with the riverine environment, inevitable affecting the fishery resources of the concerned rivers. The existing dam or barrages are poison threat to food and feeding habit, spawning biology and fish migration. They are altering and magnitude, chronology, quality of streams flows below dams and effecting fish stock.