The East Asian Species, Thermocyclops taihokuensis (Harada 1931) (Crustacea, Copepoda, Cyclopoida) in the Taganrog Bay of the 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 the Sea of Azov were studied. The East Asian copepod, Thermocyclops taihokuensis (Harada 1931), was recorded for the first time in the eastern part of the bay at a water salinity of 3.5–5.8‰. The species 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 (>7000 ind./m3); in the bay in September 2023 it reached 4000 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 the bioflow from the Don River delta. The potential consequences of the introduction of this alien copepod for the zooplankton of the Taganrog Bay are discussed.