Bighead carp Aristichthys nobilis and silver carp Hypophthalmichthys molitrix in the Southern Western Siberia

Abstract

The native range of the bighead carp Aristichthys nobilis and silver carp Hypophthalmichthys molitrix covers the East Asian river basins from the Amur to the Yangtze. These are inhabitants of large streams with a developed floodplain. These species spawn in rivers, during pronounced fluctuations in the water level, at high flow rates. A. nobilis and H. molitrix, as well as their hybrids, are widely used in aquaculture in many countries of the world. It is believed that the A. nobilis does not naturally reproduce in most places of introduction, but it is known that it successfully naturalized in the Amur river basin. Natural reproduction of the H. molitrix occurs in some rivers in Eurasia and America. In Russia, it is currently known about the natural reproduction of A. nobilis and H. molitrix in the Lower Volga and in the Kuban river. In new habitats, the bighead carp, as a zooplankton feeder, can be a food competitor for juveniles of native fish species. The naturalization of silver carp can pose a serious threat to recipient ecosystems, since it feeds on phytoplankton and it can significantly undermine one of the lower elements of the trophic chain of water ecosystems. The first introduction of A. nobilis and H. molitrix in the Ob river basin was made in 1958, in the Novosibirsk reservoir. Currently, these species are cultivated in fish farms in the region, from where they enter natural water bodies. Data on the natural reproduction of A. nobilis and H. molitrix in the Ob river basin (except, possibly, the Belovsky reservoir) is currently absen