Effects of temperature and water levels on dynamics of density and structure of the fish population of the channel-floodplain complex of a large river in the period of spring floods
Effects of temperature and water levels on dynamics of density and structure of the fish population of the channel-floodplain complex of a large river in the period of spring floods

Summary/Abstract: The article discusses the features of the dynamic process of migration of ichthyofauna from wintering sites to the wetlands of a large boreal river for feeding and spawning. The influence of factors of temperature and water level on various groups of fish is estimated, and the role of water bodies of various types during fish migration in a flooded floodplain is also established. The research was performed during the spring flood in the floodplain-channel complex of the Irtysh River (Western Siberia, Russian Federation) in the water area of the conjugate water bodies: the lotic and lentic parts of the riverbed depression and the mouth of the tributary – transit section of the migration pathway of fish to the flooded floodplain. The research work was performed by “AsCor” – computerized hydroacoustic complex, hydroacoustic survey data were processed in the laboratory. The “AsCor” complex remotely performs taxonomic identification of abundant species of fish at the family level by groups (Cyprinidae, Percidae, Coregonidae–Esocidae, Acipenseridae–Lotidae). It was found that after the breakup of ice cover, maximum densities of fish were observed in the wintering sections – the initial location of the spring migration. During the 30-days observation period in the wintering sections and conjugate water bodies, the density of fish decreased from 4 to 13 times due to their migration to the floodplain. The response to a decrease in the overall density of fish in the year-round functioning lotic part of the riverbed depression to the influence of factors of water level and temperature regimes was >0.300 in general for ichthyofauna and for all groups of fish registered by hydroacoustic method (Cyprinidae, Percidae, Coregonidae– Esocidae, Acipenseridae–Lotidae)

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