The Ctenophore, Beroe ovata Bruguière, 1789 – the New Invader in the Ecosystem of the Caspian Sea

Abstract—In November 2020, the invasive ctenophore Beroe ovata Bruguière, 1789 was recorded in samples of gelatinous zooplankton from the northern and central parts of the Caspian Sea. The obtained values of the biomass of B. ovata and its main food object, the ctenophore Mnemiopsis leidyi (Agassiz, 1865), show an uneven distribution of these species across the studied area during the study period. A large range of individual sizes of the captured specimens of B. ovata suggests the possibility of its reproduction in the Caspian Sea during this period. The northern boundary of the range of the new invader within the study area was located near the Agrakhan Peninsula. The corresponding hydrological characteristics make it possible to suggest the limiting role of water salinity. Underwater studies using video equipment showed that B. ovata is confined to relatively warmer water layers. The peculiarities of the introduction of alien ctenophores into the Caspian Sea have much in common with similar processes in the Azov–Black Sea basin.