Current Fish Community Structure of an Anthropogenically Pressured System: the Case of the Küçükçekmece Lagoon (NW Türkiye)

This study offers the first detailed investigation of the ichthyofauna of the K & uuml;& ccedil;& uuml;k & ccedil;ekmece Lagoon (& Idot;stanbul, T & uuml;rkiye) in nearly 30 years, with the aim of characterizing the current structure of the fish community in this anthropogenically pressured lagoon. Seasonal samplings were conducted between September 2023 and August 2024, and fishing was conducted at five different stations within the lagoon using multimesh gillnets and at two coastal sites using a seine net. A total of 18 fish species belonging to 12 families were identified. Only five species (Atherina pontica, Engraulis encrasicolus, Chelon auratus, Chelon ramada, and Mugil cephalus) were captured using gillnets. On the other hand, 17 species were recorded with a seine net in areas close to the lagoon's connection with the Sea of Marmara. Atherina pontica was the most abundant species in both fishing methods, while Salaria pavo, Belone belone Neogobius fluviatilis, Gobius niger, and Sparus aurata were each represented by a single specimen. The current species composition indicates a community dominated by euryhaline species, which differs from historical records that included freshwater taxa. The absence of freshwater species in the catch coincides with the observed salinity levels (up to 14.12). Except for a few resident species (e.g., A. pontica and E. encrasicolus), the lagoon is predominantly inhabited by euryhaline species, especially during spring and summer. Serving as a structured baseline, this study documents the current ecological status of fish assemblages in the lagoon following long-term environmental change.