Postmucilage status of teleost fish assemblages in the Sea of Marmara.

A frightening mucilage event occurred in the Sea of Marmara (SoM) from November 2020 to July 2021, leaving devastating effects on maritime industries, fishing activities, and the benthic ecosystem. The mucilage led to intense fish mortalities, particularly affecting species like smelt, anchovy, and picarel, with severe consequences for benthic ecosystems and various marine species. This study aims to analyze the possible long-term effects of the recent mucilage disaster on species diversity and biomass by assessing the current status of teleost fish assemblages in the SoM. The data set is based on bottom trawl surveys carried out at 52 points at ten stations in the SoM throughout 2023. Data presented through biomass and various ecological indices enabled comparative analyses of changes in fish assemblages pre and postmucilage events. During the study, a total of 5066 kg of retained catch in the 4867 km2 scanned area revealed a biomass of 1040.9 kg·km-2, represented by 45 species in the SoM. Commercial species such as Trachurus trachurus, Merlangius merlangus, Merluccius merluccius stood out with the highest biomass in the teleost fish assemblage. Species richness and total teleost biomass tended to decrease by over 20% in the postmucilage period, reflecting the possible destruction of mucilage to fish populations in the SoM. The decreasing trend in biomass was limited to pelagic species. The extent of the impact on pelagic species may be the cumulative effect of ongoing overexploitation and reduced landing size, as well as intense mortality recorded during the mucilage period. The findings underscore the need for sustainable fishing practices and marine protected areas, including compliance with the Marmara Sea Action Plan, for the restoration and conservation of fish assemblages. [ABSTRACT FROM AUTHOR]