Годовая динамика плотности и таксономического состава рыбного населения русловой ямы (влияние факторов)

Abstract

The article reports the results of the study on the annual dynamics of fish density, taxonomic composition of the fish population in a section of a riverbed depression in the lower reaches of the Irtysh River. A complex system of interaction between environmental factors and fish relationships in the predator-prey system in the studied section of the river under changing environmental factors is considered. The study was conducted using echometric sounding of the water column of the riverbed depression with an acoustic complex; during the open water period it was performed from a boat and during the ice cover period — from a snowmobile. The study also analysed the dynamics of environmental factors (turbidity, temperature, water level) and their effect on fish density. The maximum fish density in the riverbed depression was observed in summer, when juveniles migrate from the floodplain to the main channel. Fish density differed significantly during periods of open water and ice cover. Groups of cyprinids and percids had the largest share in the fish population. Their joint share varied from 68.53 to 87.42% of the total fish density; these values were noted in January and August, respectively. The maximum fish density was noted in June, the minimum density — in October and December: 4.49, 1.19 and 1.45 thousand ind./ha, respectively. The dynamics of the total fish density in the water area of the riverbed depression is described by a polynomial regression equation, and the only influencing factor is water temperature. The dynamics of the density of taxonomic groups in the water area of the riverbed depression demonstrated the following characteristic features: for the density of cyprinids the influencing factors were temperature and the water level; for percids, coregonids and pikes — the density of cyprinids, cyprinids and percids, respectively; for burbots and sturgeons — the water level. The study revealed that turbidity has high reliable correlation with the water level and temperature.