The present written work represents the results of the research of the ichthyofauna from the lower course of the Prut River (including the Manta puddle and the Beleu lake) in terms of succession. It was established that, as a result of anthropogenic actions (drying of over 27-30 thousand ha of puddles, dam of the banks of the Prut River and its tributaries, extraction of sand and river stone from the minor riverbed, irreversible use of water in irrigation and industries, pollution, construction of the Costești-Stânca dam, destruction of wood cuts for lithifile and phytophilic species, etc.) in the ichthyofauna on the lower course of the Prut River, there were significant changes in diversity, quantitative and qualitative composition, and functional status of fish populations.

The result of multiannual research that supports the concept of biological progression of Gobiidae family representatives on the territory of the Republic of Moldova in current ecological conditions are revealed in this paper. A new species was found for the Dniester riverbed - Caspiosoma caspium (Kessler, 1877), in the spring of 2021, being captured in number of 16 specimens, this previously being identified only in the Cuciurgan refrigerated lake in 1969, in a single specimen.