The taxonomic status of the Black Sea and Marmara Sea populations of the Broadnosed Pipefish <italic>Syngnathus</italic> cf. <italic>argentatus</italic> Pallas (Teleostei: Syngnathidae) based on morphological and molecular characters.

As the Black Sea and Marmara Sea population of the Broadnosed Pipefish <italic>Syngnathus</italic> cf. <italic>argentatus</italic> show some morphological differences from the Mediterranean Sea populations, some authors regard it as an endemic species <italic>Syngnathus argentatus</italic> Pallas, 1814, while others consider it as a synonym of <italic>S. typhle</italic> Linnaeus, 1758. The aim of this study is to compare the populations of the Black Sea and Sea of Marmara with the Aegean Sea population, using a combination of morphological and molecular characters, in order to clarify their taxonomic status. Sampling was carried out at three stations in the Black Sea, two in the Sea of Marmara and three in the Aegean Sea, and a total of 24 morphometric and 6 meristic characters were examined. Metric data were analysed by Principal Component Analysis (PCA) and phylogenetic relationships between the populations were analysed using both cytochrome oxidase subunit 1 (COI) gene and cytochrome b (cyt-b) gene sequences. Although constant differences were observed in snout depths between the Black Sea/Marmara Sea and the Aegean Sea populations, other morphological features and genetic analysis did not enable these populations to be differentiated. These findings indicate that <italic>S. argentatus</italic> is a synonym of <italic>S. typhle</italic>. [ABSTRACT FROM AUTHOR]