Northernmost record of Valenciennea wardii (Actinopterygii, Gobiiformes, Gobiidae) from Ulleung Island, Northwest Pacific

Valenciennea wardii (Playfair in Playfair et Günther, 1867) often exhibits color variations depending on its habitat. However, owing to its reclusive behavior and low abundance, it is challenging to collect V. wardii using fishing gear, and ecological and population genetic studies remain limited. On 11 November 2024, a single specimen of the tropical gobiid fish V. wardii, which was previously unrecorded in the waters around the Korean Peninsula, was collected from the coastal waters off Ulleung Island via SCUBA diving.

It was analyzed using detailed morphometric and meristic measurements in conjunction with mitochondrial cytochrome c oxidase subunit I (COI) sequencing to confirm its taxonomic identity. Morphological analysis revealed distinct characteristics, particularly brown transverse body bands and a black blotch with a white margin on the first dorsal fin, which distinguish it from other closely related species. Genetic analysis showed high similarity to V. wardii specimens collected from the South China Sea and Sri Lanka but indicated notable divergence from those collected in the Philippines, suggestive of potential cryptic diversity within the species.

This study reports the poleward range expansion of V. wardii and proposes the new Korean name “ gal-saeg-tti-bok-gi-mang-duk ” based on the characteristics of this species having dark brown transverse bands. These records provide concrete evidence for the poleward expansion of this tropical marine fish species and play a crucial role in monitoring the impacts of climate change on marine ecosystems.