Controlling methods investigation of the Caspian Sea invasive Ctenophora (Mnemiopsis leidyi)

The alien ctenophore Mnemiopsis leidyi which was transported from the Black Sea into Caspian Sea at the end 1990s has been affecting the Caspian Sea ecosystem. In this study, spatialand temporal distribution of M.leidyi , Zooplakton and Phytoplankton were studied from July 2001to July 2002 in three transects (Lisar, Bandar Anzali and Sefidrood) in the Iranian coasts of the Caspian Sea (Guilan province). Each transect had four stations located at 5, 10, 20 and 50 m bottom depth contours. By using Secchi disk,visibility or turbidity from 0.25 to 9 m and average was 3.41 m. Thehightest Secchi disk was depth 50 m with 4.77 m and the lowest observed depth 5 (1.83 m). The sea-surface Salinity ranged between 8.13 to 12.74 ppt with average 11.87 ppt. The highestSalinity was at depth 50 m (with value 12.52). Mnemiopsis leidyi achieved maximum abundance and biomass (5122 ±1750 n m2 and 221.3 ± 91 g m2) in October 2001. Minimum abundance and biomass (8.3 ± 3.8 g m2 and 337 ±165 n m2) of the ctenophore were measured in Decemder 2001. The highest biomass was at 20 m depth (145.36 ± 43.2 g.m2 ) in autumun and lowest biomass (1.9 ± 0.95 g m2 ) wasobtained at 50 m depth in winter. The young specimens (10 mm) contributed about 97 % oftotal abundance of the population. The maximum measured length was 51-55 mm. The highest average biomass 112.3 ± 48 g m2 was measured in Sefidrood region, and the lowest biomass (67.17 ±46.8 g m2) observed in Anzali region. Maximum of Zooplankton abundance (27774 ±15137 n m3) was observed in April 2002 and Minimum abundance was 2760 2135 n m3 in November 2002 . Copepoda with 90 % had the heighest population abundance of Zooplankton. The lowest Zooplankton Population belonged to Ostracoda, Notholca ,Lecane (0.0001 %). The maximum Phytoplankton was 781835000±109857176 n m3 in October 2001 and minimum was observed in July 2002 with 9958000±48594531 n m3. The variety of tempreture, depth and food were important factors in the Mnemiopsis distribution .