This paper reflects the current state of ichthyofauna in the research made in Bistrita River Basin, regarding the inventory of the fish species that inhabit the rivers Calu and Iapa, right tributaries of the river Bistrita. The data obtained by us were compared with those existing in the literature (Bănărescu P., 1964) to capture changes recorded in the structure of the fish communities after the human impact appeared during 1960 and up to present. So, there were made investigations regarding the composition in the species, the fisheries of these rivers through the calculation of the ecological index, and the determination of the index of biologic integrity (IBI), which reflects best the actual state of the fish population from these ecosystems.