BIOLOGICAL FEATURES OF TARAN (RUTILUS HECKELII) OF THE DNIEPER-BUG ESTUARY SYSTEM

Purpose. To analyze morphological variability and basic biological features of the modern stock of taran of the Dnieper-Bug estuary system in the conditions of the transformed Dnieper flow. Methodology. Morphological variability was determined based on the comparison of morphological features of roach Rutilus rutilus (Linnaeus, 1758) of the Kakhovka reservoir and semi-migratory taran Rutilus rutilus heckelii (Nordmann, 1840) of the Dnieper-Bug estuary system. As a main criterion of the evaluation of the taran stock biological state, we used age, sex structure, growth characteristics, fecundity and condition factor. Fish sampling was carried out at stationary monitoring-observation stations of the Institute of Fisheries NAAS of Ukraine. Field and cameral processing of the collected materials were performed based on conventional methods and guidelines. Findings. Morphological variability analysis demonstrated significant differences between Dnieper and Bug taran. The highest differences were observed for antroventral distance (td=11.19). Significant differences were also observed for antenanal and ventroanal distances td=4.05-4.14. No significant differences were found for meristic features. There were also significant differences between Dnieper-Bug taran and Kakhovka reservoir roach, which had formed a resident form after regulating the Dnieper River flow. Kakhovka reservoir roach is more deep-bodied with Н=32.79%, t-test value was 5.65. Pelvic fins were more shifted to the caudal fin (td=5.28) that resulted in significant difference (p