DOI: 10.26650/ijegeo.1893703 ISSN: 2148-9173

Ichthyoplankton in the Strait of Istanbul (Bosphorus) and Northern Sea of Marmara: Summer Snapshot of Spatial Distribution and Satellite Modeled Hydrographic Drivers

Orçin Uygun
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The Strait of Istanbul (Bosphorus, SoI) system, which serves as a biological corridor between the Black Sea and the Sea of Marmara, plays a critical role in the transport of fish during their early life stages. This study examined the structure, distribution, and relationship with environmental factors of the surface ichthyoplankton assemblage in the transition zone between the Strait of Istanbul and the Northern Marmara Sea, beginning at the Black Sea entrance. The research was conducted at 13 stations determined between 22 and 29 July 2023, representing the summer period. Sampling was performed using a WP2 plankton net, while hydrographic data (temperature, salinity and current velocity) were obtained in high resolution from the Copernicus Marine Service (CMEMS) satellite database. A total of 21 taxa were identified in the assemblage, with Engraulis encrasicolus (European anchovy) and Trachurus mediterraneus (Mediterranean horse mackerel) identified as the dominant species in the upper layer. The results of the Distance-Based Linear Model (DistLM) and dbRDA analyses indicate that temperature and salinity gradients are the main explanatory variables for variation in species composition. Additionally, the observed spatial patterns and the model's sensitivity to current velocity suggest that the Strait of Istanbul surface current system could potentially act as a supportive mechanism for the localized transport of E. encrasicolus early life stages. In turn, this transport process is thought to have potential implications for the local recruitment dynamics of the species in the Sea of Marmara.

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