Identification of Polyphemidae in the Iranian coasts of Caspian sea (Guilan province) consequences of the Mnemiopsis leidyi invasion

Subject Areas : New Technologies in Aquaculture Development

Received: 2020-01-12 Accepted : 2020-01-12 Published : 2007-08-23

Keywords: Zooplankton, key words : Caspian sea, Polyphemidae, Ctenophore, Mnemiopsis leidyi,

Abstract :

ABSTRACT        The Polyphemidae of sothern Caspian sea were identified and photographed fulfillent of the Hydrology and Hydrobiology projects in 1996 and 1999 separatelly. Studying the Zooplankton  reaveled that there are totally 25 native speices , of which 16 species belonged to Polyphemidae with dominant species being  Podon polyphemoides , Polyphemus exigus , Cercopagis pengoi and Podonevadne trigona.This Zooplankton group is the most important food source for fish and their larvae in summer, They were most abundant in Summer and at the beginning of Autumn , and their maximum frequency were observed in surface layer ( 0 metre to 25 metre) , they were less abundant in 50 metre , and non was seen at depth of over 100 metre .The exotic ctenophore Mnemiopsis leidyi which wastransported from the Black sea into the Caspian sea at the end of 1990s has negatively effected the ecosystem of this new environment .As for Mnemiopsis feeding different zooplankton ,   at present  of the Polyphemids in Caspian sea only the species Podon polyphemoides and sometimes  polyphemus exigus  have been collecteded in low numbers during a short period  at  the end of spring  , whilst other Polyphemids had no any remarkable  populations.