First record of Gymnogobius macrognathos on Akkeshi mud flat, Hokkaido, Japan and utilization of Upogebia major burrows

Abstract

Eight specimens of a threatened goby, Gymnogobius macrognathos (30.04– 38.87 mm in standard length), were collected on a mudflat characterized by abundant burrows of Upogebia major, at Akkeshi, Hokkaido, northern Japan in August 2017. Because G. macrognathos specimens were collected directly from U. major burrows by suction pump, and were also collected with U. major by digging sediment exposed at low tide, it was concluded that G. macrognathos utilized U. major burrows on the tidal flat. Gymnogobius mororanus and an unidentified species of Gymnogobius also utilized U. major burrows. The presence of G. macrognathos at Akkeshi represents the northernmost record of the species in Japanese waters, the isolated population being ca. 500 km north of the main distributional range of the species along the Pacific coast of Japan.