Relocation of Fish Populations to Estuaries and Bays of the North-Western Section of the Black Sea as a Consequence of Technogeneous Disasters and Natural Processes in 2023

The studies carried out from 05.15.2023 to 12.31.2023 showed that some part of the fish population of 12 species moved from the lower section of the Dnieper River and probably from the Kakhovka Reservoir to the western part of the Dnieper-Bug estuary (liman). This was caused by destruction of the Kakhovka dam on 06.06.2023, and inflow of huge water masses from the Kakhovka Reservoir. After the disaster, the numbers and occurrence frequency of most fish species in the western part of the estuary significantly increased. In four species, the certain size groups were replaced by another. Two species have been detected in the estuary for the first time. Of them, one is a dangerous invasive species, and other was absent for 25 years. As a result of relocation further to the Black Sea, <i>Polyodon spathula</i> was found for the first time in the Dzharylgach Bay. <i>Serranus scriba</i> was registered in the Berezan estuary, and <i>Sander marinus </i>was found in the estuary after the 80 years of absence. Besides, part of <i>Sander marinus</i> population migrated from the Dnieper liman to the upper part of the Bug liman and upstream to the lower section of the South Bug River. <i>Tinca tinca</i> was also registered for the first time in the Berezan liman, probably owing to the expansion of its range to the northwestern part of the Black Sea. The destruction of fish breeding ponds in Crimea because of catastrophic storm on November 26-27, 2023 resulted in migration of many fishes to the Dzharylgach Bay.