
The scientific assessment is included with freshwater ichthyofaunal diversity, distribution and evaluation of diversity indices analysis which are found in Doyang reservoir’s different distinct stretches, Nagaland in between the year 2015 to 2018. Total 64 numbers of freshwater fishes in which 6 order and 16 families were found where most dominated order is Cypriniformes and family is Cyprinidae. Depending on fish distribution in distinct three stretches of the reservoir diversity indices like Shannon diversity index (H), Margalef’s richness index, Simpson’s Diversity Index (1-D), Chao-1, Dominance Indices, Species evenness has been analyzed which shows a significant result regarding that facts. These works also found out that due to the introduction and culture practices of IMC and other introduced carp species, the main reservoir fish diversity has been reduced. Introduced fish species are destroying endemic fish species habitat. Due to the less stress towards the upper stretch of reservoir (towards the Doyang River) endemic species are much more available rather than other stretches of the reservoir. The specified fishes need immediate proper scientific management and conservation strategies for future availability of these freshwater fish species.