Factors Influencing the Invasion of the Alien Ctenophore Mnemiopsis leidyi Development in the Southern Caspian Sea

Mnemiopsis leidyi population activities first were recorded during the coastal observations in ۲۰۰۱ in which its population considerably increased afterward and now sustained the southern Caspian Sea. Maximum summer-autumn M. leidyi abundance was recorded in euphotic layer in ۲۰۰۲ (۸۵۱±۸۵ ind.m-۳) and maximum biomass was in ۲۰۰۱ with ۴۸.۱±۱۴.۴ g.m-۳) while minimum were in aphotic layer. In years ۲۰۰۳ to ۲۰۱۱, M. leidyi abundance and biomass sharply declined to ۱-۸۴۳ ind.m-۳ and ۰.۰۷-۳۷.۷ g.m-۳, respectively. The length-frequency distribution of Mnemiopsis showed larval, juveniles and transitional stages that made up ۹۸.۶% of the total population. In the southern Caspian Sea, Acartia tonsa was the highest number of mesozooplankton species (۳۶ species) which decreased tenfold after Mnemiopsis invasion during ۲۰۰۱-۲۰۱۰. Fecundity experiments of Mnemiopsis showed the average of ۸ eggs. day-۱, with a maximum of ۳۵ eggs.day-۱which increased with increasing body length. The main food was larger amounts of zooplankton prey such as copepodites and adult of A. tonsa. It seems the sharp decreased of Mnemiopsis abundance could be related the decreasing of ova reproduction; and food ability is the main reasons of M. leidyi sustained in the southern Caspian Sea. The objective of present study was to provide information about parameters influencingthe M. leidyi decreased after initial bloom invasion in the southern Caspian Sea.

کلیدواژه ها:

Caspian Sea ، Diet ، Mnemiopsis leidyi ، Ova reproduction ، Zooplankton