To produced an effect of Mnemiopsis leidyi on Cladocera in Sothern Iranian Coasts of the Caspian Sea after invasio n

Order Cladocer belongs to Class Branchiopod is the most important Zooplankton group which they are feeding by different fish and their larva in summer, They had most abundance in Summer and the beginning Autumn, and their maximum frequency were observed in surface layer (0 meter) to 25 meter, they had a few abundance in 50 meter, and no seen in 100 and upper 100 meter depth. The polyphemidae in southern Caspian Sea introduced and photography during Hydrology and Hydrobiology projects in 1996 and 1999. The results of Zooplankton study reveal that there are totally 25 native species , that 16 species belongs to Polyphemidae with dominant species podon polyphemoides , polyphemus exigus , Cercopagis pengoi and podonevadne trigona. The alien Ctenophore Mnemiopsis leidyi which was transported from the black sea in to the Caspian Sea at the end of 1990s has been negatively affecting ecosystem in this new environment. Mnemiopsis leidyi feeding Zooplankton, eggs and fish larva, an assessment of data collected during the period of 2001- 2002 in Caspian Sea, showed that the number of fish eggs and larva and Zooplankton was negatively related to Mnemiopsis leidyi. The mass occurrence of Mnemiopsis appears to be one of the most important reasons for the sharp decrease of Anchovy and other pelagic fish stocks in the Black sea. At the present time in Polyphemidae only Podon polyphemoides and sometimes Polyphemus exigus was observed, and other species in this family hadn’t population in Caspian Sea.

کلیدواژه ها:

Caspian Sea ، Cladocera ، Zooplankton ، Mnemiopsis leidyi