Abstract
Three different jellyfish species were detected during the underwater observations which were carried out in October 2021 on the shores of the Ocaklar Bay, southern Marmara Sea. Observed jellyfish species are Cotylorhiza tuberculata (Macri, 1778), Aurelia aurita (Linnaeus, 1758), and Beroe ovata (Bruguière, 1789). Although it generally spreads in the Mediterranean Sea, two individuals of C. tuberculata species, which have never been observed previously in the southern Marmara Sea, were seen in this study. The umbrella diameters of both individuals were calculated as 25 and 38 cm, respectively. The present study reports the first occurrence of C. tuberculata on the southern coasts of the Marmara Sea and a new distribution/range area for the Marmara Sea. The present paper is also considered to provide significant contributions to the biodiversity and spatial distribution of marine species in the Marmara Sea ecosystem.