Survey of Density variation and Diversity of Cnidarins Medusae (Diphiydae & Gerionidae) in North Western Persian Gulf (Bahrakan water)

To taxonomic identification and density determination of medusae in Bahrakan area (Persian Gulf), planktonic samples were collected from 6 stations in July, August, October in 2010 and December, February and April in 2011. Sampling was conducted with 300µm mesh size plankton net. Environmental parameters such as salinity, pH, temperature and dissolved oxygen were measured. 5 species were identified. Most abundant species of them were Liriopetetraphylla and its relative frequency was 27.35%. The medusae density was the highest in July and lowest in February.L. indicaisthe first reported in the Iranian waters of the Persian Gulf. The result of Correlation test showed that the temperature has the higher relationship whit density of medusae. Analysis variance test was conducted to study of month impact on medusae abundance. The Shannon index was ranged from 0 to 2.07 and maximum value of this index observed in July.