The East Asian species <i>Thermocyclops taihokuensis</i> (Harada 1931) (Crustacea, Copepoda, Cyclopoida) in the Taganrog Bay of Azov Sea

In August–September 2021–2023, the composition and abundance of pelagic Copepoda in the Don River delta and in the eastern part of the Taganrog Bay of Azov Sea were studied. The East Asian copepod, Thermocyclops taihokuensis (Harada 1931) was recorded for the first time from the eastern part of the bay at a water salinity of 3.5–5.8‰. The species must have entered the Taganrog Bay with water from the Don River. The largest population of the invader was registered in the Don River delta in August 2021 ( 7.000 ind./m3); in the bay in September 2023 it reached 4.000 ind./m3. The body size and fertility of the invader were close to those in the Tsimlyansk Reservoir and the Don River. In 2023, the reproduction of T. taihokuensis was noted in the bay with an extremely low (about 1%) proportion of mature individuals in the population. The species seems to have not yet been fully naturalized in the bay, its population still being supported by bioflow from the Don River delta. The potential consequences of the introduction of this alien copepod for the zooplankton of Taganrog Bay are discussed.