STRUCTURAL CHARACTERISTIC OF ICHTHYOPLANKTON IN A SMALL RIVER FLOWING WITHIN A BAR PLAIN OF THE DNIPRO RIVER

Purpose. Using as an example of a small river, which flows through a bar plain of the Dnipro, to study species composition of the littoral ichthyoplankton, dynamics of its structure during the season and its diversity in different parts of the river. Methodology. The littoral ichthyoplankton was investigated during four seasons of 2011-2014 on the Vita river, a right tributary of the Dnipro affected by the operation of Kaniv HPP. The research covered the main channel, a permanent backwater connected with the channel, as well as temporarily flooded areas of the floodplain and separated from the channel oxbow lakes. Samples were collected with standard sweep nets and Bagenal buoyant nets. Identification of young fish was carried out under binocular microscope MBS-9. Early life stages of larvae were determined according to the system of V. Vasnetsov. Species diversity of ichthyoplankton was assessed by the Shannon index. Findings. The littoral ichthyoplankton during May-July mostly consisted of limnophilic fish larvae belonging to a family Cyprinidae. In the river channel and the backwater at the beginning of the period the larvae of roach (Rutilus rutilus) prevailed, later they were substituted by larvae of more thermophilic species, among which the rudd (Scardinius erythrophthalmus) was the most abundant. In the oxbow lakes and temporarily flooded areas in spring the coastal ichthyoplankton was mainly structured by larvae of Carassius sp. and the rudd, in summer the larvae assemblages of oxbow lakes were quantitatively dominated by the sunbleak (Leucaspius delineatus). In areas covered with vegetation the larvae of invasive Chinese sleeper (Perccottus glenii) were firstly found. Rheophilic species among young fish were absent, which indicates unfavorable conditions for their spawning at present hydrologic regime of the river. Originality. For the first time the coastal communities of early young fish in a small tributary of the Dnipro were investigated, seasonal dynamics of their structure was considered, the main spawning grounds of industrial fish were determined. Practical value. The obtained results point out the important role of small tributaries of the Dnipro in reproduction of many fishes, particularly the industrial ones. They can serve as a basis for identifying the most suitable places for restoration of fish populations, as well as for proper planning of measures aimed at protection, conservation and restoration of ichthyofauna of small rivers and waters associated with them.