First Record of Eutaeniichthys cf. gilli Jordan Snyder, 1901 (Actinopterygii: Gobiiformes: Gobiidae) from Vietnam

Eutaeniichthys cf. gilli Jordan Snyder, 1901 (Gobiidae), an estuarine goby with a high risk of vulnerability, is documented for the first time in Vietnam, representing the recent southernmost and westernmost range of distribution of the species. A single specimen measured 26.7 mm in standard length (SL) was collected during the summer from the intertidal flat area near the mouth of the Red River at Xuan Thuy National Park, Vietnam. The collection was conducted during high tide using a small seine net in an area characterized by scattered mangrove trees and a mixed sandy and muddy bottom with shrimp burrows. This goby is characterized by a very elongate and slender body with three short spines in the first dorsal fin and a stripe of melanophores extending along the side throughout its entire length. The photographic, meristic, and morphometric data of the specimen are provided to aid in resolving the ambiguity of taxonomic studies of gobies in Vietnam.