Investigations were made on the blood of Mastacembelus armatus exposed to heavy metals (Cu, Ni, Fe, Co, Mn, Cr and Zn). The study reveals the contamination of Harduaganj Reservoir with heavy metals. The heavy metal content in reservoir water were in the order of Fe > Cu > Zn > Mn > Ni > Co > Cr. The values for the heavy metals such as Fe (8.71 mgL-1), Ni (0.12 mgL-1), and Mn (0.21 mgL-1)...