Fish survey were undertaken during august 2015 to October 2015 to predict the checklist of fishes in Koshi Barrage. An attempt has been made to survey the existing fish species in three months of duration. Fishes caught alive or in fresh condition were preserved in 9-10% formalin solution. The fishes were collected, fixed and labeled giving serial numbers, the name of exact locality from where they have been collected; date of the collection and the common local name on each jar.The fishes were identified using a website www.fishbase.com.Thirty seven species of fishes belonging to eighteen families, thirty two genera were recorded. Out of these ten species, Canthophrys gongota, Mystus cavasius, Mystus vittatus, Nangra assamensis, Clupisoma montana, Parambassis lala, Macrognathus aral, Chaca chaca, Ompok bimaculatus and leiodon cutcutia were identified to be the new species.