Long-term dynamics and modern species composition of lampreys and fish of the Sura-river basin

Before the beginning of XX century in the Sura-river basin 36 fish species (including 4 continuous) were reliably encountered. From 1900 to 1960 species diversity increased up to 39 species. At the same time began the invasion of species the first of which was Carassius auratus. After the cascade of hydropower stations on the Volga River had been built and the rivers had been polluted through- and stenobiontic species gradually disappeared from the fauna. However, species diversity remained the same - 39 taxa - due to appearance in the reservoirs alien species ( Clupeonella cultriventris, Perccottus glenii, Aristichthys nobilis ). The modern species composition of the fish populations of the Sura basin consists of 50 taxa, including 37 local species and 13 alien ones, the continuous forms are not marked. The acclimatized and randomly introduced species appeared during the last decade include the white silver carp Hypophthalmichthys molitrix, grass carp Ctenopharyngodon idella, rainbow trout Parasalmo mykiss, peled Coregonus peled, black carp Mylopharyngodon piceus, buffalo bolsheroty Ictiobus cyprinellus, round goby Neogobius melanostomus, needlefish Syngnathus nigrolineatus. The bulk of species is found in the river-beds of Sura (42) and major tributaries (34). In all the reservoirs and the streams of both natural and artificial origin are found only the 7 fish species: Esox lucius, Leucaspius delineatus, Barbatula barbatula, Carassius auratus, Cyprinus carpio, Rutilus rutilus and Perca fluviatilis. The 5 species - Clupeonella cultriventris, Anguilla anguilla, Abramis ballerus, Lucioperca volgensis and Neogobius melanostomus - are characteristic exclusively for the Sura river. Only in the ponds and the river-reservoir the 3 species - Ctenopharyngodon idella, Hypophthalmichthys molitrix and Ictiobus cyprinellus - are registered.