MEPS 314:171-185 (2006)  -  doi:10.3354/meps314171

Invasive ctenophore Mnemiopsis leidyi in the Caspian Sea: feeding, respiration, reproduction and predatory impact on the zooplankton community

Galina A. Finenko1, Ahmet E. Kideys2,6,*, Boris E. Anninsky1, Tamara A. Shiganova3, Abolghaseem Roohi4, Mojgan R. Tabari4, Hosseinali Rostami4, Siamak Bagheri5

1Institute of Biology of the Southern Seas, Nachimov Ave. 2, Sevastopol, Ukraine
2Institute of Marine Sciences, Middle East Technical University, Erdemli 33731, Turkey
3P.P. Shirshov Institute of Oceanology RAS, 36 Nachimovskiy Pr., Moscow, Russia
4Mazandaran Fisheries Research Center, Sari, Iran
5Guilan Fisheries Research Center, Anzali, Iran
6Present address: Joint Research Center, Institute for the Protection and Security of the Citizen, Ispra, 21020 Varese, Italy
*Corresponding author. Email:

ABSTRACT: The impact of the invasive ctenophore Mnemiopsis leidyi on the zooplankton community of the Caspian Sea was quantified according to food consumption and other major physiological activities (i.e. respiration and reproduction), coupled with field data on population structure. The adverse effects of M. leidyi on the zooplankton community during the first years of the invasion were tremendous for the Caspian Sea compared to other regions affected by this ctenophore. The impact was highest in summer, due to high water temperatures and a population size structure in which juvenile ctenophores with mean lengths of 2 to 5 mm accounted for most of the population. During winter/spring, these ctenophores could consume the available stock of zooplankton in 3 to 8 d, whereas in summer consumption took only 1 d. The computed critical ctenophore biomass that does not affect (decrease) the abundance of mesozooplankton in the Caspian Sea is about 4 g m–3 (or 120 g m–2, assuming most of the ctenophores occur in the upper 30 m layer). As is clear from the monitoring data, the M. leidyi biomass in summer in different regions of the Caspian Sea is far in excess of this value. Such a high abundance of ctenophores, if maintained, would constantly keep the non-gelatinous zooplankton biomass at very low levels, and, as a consequence, no recovery could be expected in the pelagic fishery.

KEY WORDS: Mnemiopsis leidyi · Feeding · Respiration · Reproduction · Predatory impact

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