Protecting coastal habitats: is a 24-meter isobath ban on purse seines adequate for coastal areas and endangered species?

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The Sea of Marmara (SoM) holds significant importance for both local and regional fisheries due to its characteristic as a semi-enclosed sea on the migratory route of small and medium pelagic fish. While this area sees active fishing with numerous small-scale vessels and approximately 150 purse seiners, there has been a noticeable absence of research on the spatial and temporal distribution of intense fishing pressure in this relatively small sea. Concerns regarding the sustainability of purse seining in the region, specifically in relation to its potential interaction with the seafloor, have emerged over time. This study aimed to assess the spatial and temporal distribution of purse seine fishing effort in the Sea of Marmara (SoM) from 2012 to 2022. The objectives were to identify the locations of concentrated purse seine fishing effort, determine if these clusters were statistically significant hotspots, and uncover any spatio-temporal variations in fishing activity. To address these issues, this study assessed the apparent fishing effort of purse seiners from 2012 to 2022 using data from Global Fishing Watch. Various statistical tools of geographic information systems (ArcGIS and QGIS) were applied to achieve the following. identify the locations where apparent clusters of purse seine fishing effort were concentrated in the SoM; determine if these identified clusters were statistically significant hotspots; and uncover any spatio-temporal variations in fishing activity. The analyses revealed persistent and intensifying purse seine fishing efforts concentrated in the eastern sector of the SoM. This area includes ecologically sensitive habitats and serves as a habitat for vulnerable species, such as Posidonia meadows, Pinna nobilis, and Octocorals. Additionally, it was found that 50% of the fishing effort occurred in areas shallower than 50 m, raising public concerns about the protection of these specific zones. The findings indicate significant and increasing fishing pressure in the eastern sector of the SoM, posing potential risks to sensitive marine habitats and vulnerable species. These results underscore the need for targeted management strategies to ensure the sustainability of purse seine fishing and the protection of critical habitats in the SoM.