Mnemiopsis leidyi A. Agassiz, 1865 (Ctenophora: Lobata) in the Inshore Areas of the Black Sea: 25 Years after Its Outbreak

Abundances, biomasses, size structures, and reproduction rates of the comb jellies Mnemiopsis leidyi and Beroe ovata were studied in the shelf area of the Black Sea near Sevastopol in 2013–2014. Longterm data on the population development were analyzed. The peculiar feature of M. leidyi development in recent years is a shift of its development to an earlier time of the season and a significant decrease in its reproduction rate: in the summer months in 2014, the average reproduction rate of adult ctenophores (30–70 mm) constituted only 20% of that in 2004. Such shift was related to the increase in temperature in the upper homogeneous layer, which, in turn, resulted in a decrease in its feeding rate.