Status of the Sea of Marmara ecosystem and its fishery resources: Mucilage episodes and recommendations for sustainable fisheries

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Demirel N., Yildiz T., Ulman A., Zengin M., Akoglu E., Saygu I., ...More

in: Mucilage Problem in the Sea of Marmara, Meriç Albay, Editor, Istanbul University, İstanbul, pp.217-232, 2023

  • Publication Type: Book Chapter / Chapter Research Book
  • Publication Date: 2023
  • Publisher: Istanbul University
  • City: İstanbul
  • Page Numbers: pp.217-232
  • Editors: Meriç Albay, Editor
  • Istanbul University Affiliated: Yes


Various studies have recently been carried out to assess the condition of the Sea of Marmara's ecosystem and fish stocks. In this section, i) The results obtained from these studies are synthesized to reveal the ecosystem change and fisheries status; ii) The relationship between the mucilage event and the fisheries, and the status of the important fish stocks before and after mucilage events are evaluated; and lastly iii) Recommendations are developed for better fisheries management and stock sustainability. The Sea of Marmara has undergone a significant regime transition in terms of ecosystem status and human-induced pressures between 1994 and 2012. In this period, human-induced pressures increased notably due to overfishing, increasing seawater temperatures due to climate change, and pollution in the marine environment, especially via the main city of Istanbul and the Gulf of Izmit. Furthermore, some commercial fish and invertebrate species which were extirpated in the Sea of Marmara fisheries or decreased by their catches more than 80% were observed during this period. Especially, the majority of large pelagic predator species have disappeared, which is a strong indication of a failing marine ecosystem. The withdrawal of predatory species during this transition period increased the stocks of small pelagic fish and deep-water pink shrimp for benthic species. In addition to the effects of other anthropogenic pressures (e.g., eutrophication via nutrient and organic matter load) mentioned in the formation of mucilage in 2007, fisheries, which alter the relative composition of species in the food web and thus their interactions with each other, by targeting only certain species (selective exploitation), appears to have a significant effect. Subsequently, after the 2007 mucilage formation, the SoM fisheries suffered the most economic damage.