Postmucilage biodiversity of shallow water fish assemblages: A case study in the Marmara Sea, Turkey

: A dense mucilage event occurred between November 2020 and August 2021 in the Marmara Sea, Turkey. In this study, the aim was to understand the effect of mucilage on coastal fish biodiversity. For this purpose, juvenile and small-sized adult fish species were sampled with an experimental beach seine at 12 equally-spaced stations around the Marmara Sea between November 2021 and April 2022. In total, 34 species belonging to 19 families were sampled. Approximately 70% of the total fish abundance were Atherina boyeri Risso, 1810 , Chelon auratus (Risso, 1810) and Chelon saliens (Risso, 1810). Highest abundance was detected from S5 (Marmara Ereğlisi) and S11 (Florya) comprising 17.3% and 14.2% of total abundance, respectively. Maximum species richness was found at S4 (Erdek) and S12 (Yalova Tigem), with 21 and 18 species, respectively. The highest biodiversity indexes were seen at S4, S8 (Karacabey floodplain area) and S12, whereas the lowest biodiversity index was found at S9 (Büyükçekmece). S4 and S8 should be monitored and protected by fisheries management authorities due to being nursery and protection areas for the Sea of Marmara. When the biomass and biodiversity of the coastal fish assemblages were compared with previous studies conducted before the mucilage event, it can be said that mucilage did not adversely affect recruitment success.