The impacts of Mnemiopsis leidyi on Kilka resources in the southern Caspian Sea

There are 3 species of kilka in the Caspian Sea consist Of: Clupeonella engrauliformis, C. grimmi and C. cultriventris. These species are caught by fishing method of tunnel net with underwater light in the inshore waters (depths of 40-100m).
The maximum recorded catch for three species in the Iranian waters had been 85000 tons per year during period of 1998-99. In the next years (2000-2001) despite of increasing the effort, the amount catch was dropped drastically.
The result or collected commercial catch data showed that there are some changes in kilka catch compositions and also the frequency of common kilka has been increased since 1998. On the other hand, this species was a main part of commercial catch composition during all months.
Meanwhile in the previous years, they were observed only during warm seasons (spring and summer). Based on fishermen and personal observations, the transparency of sea Water Was decreased rapidly during the years of 1999-2000 and at that time there were found a high abundance of Mnemiopsis leidyi in commercial catches.
Simultaneously, with an increase in the mass of Mnemiopsis leidyi, the amount of catch and CPLUE or kilka have been sharply decreased.