On the systematics of three eelpout species (Teleostei: Zoarcidae: Lycodes) endemic to the Sea of Okhotsk

Three nominal species of eelpouts endemic to the Sea of Okhotsk, specifically Lycodes ygreknotatus Schmidt in Taranetz, 1937, L. microlepidotus Schmidt, 1950, and L. fulvus Toyoshima, 1985, are reinvestigated based on all type materials and additional specimens. The latter two species are recognised as junior synonyms of L. ygreknotatus, as no significant morphological differences were found among these taxa. Lycodes ygreknotatus is rediagnosed. It exhibits significant geographic variability in both the number of vertebrae and the density of scale cover. The observed variability can likely be attributed to differences in environmental temperatures across different parts of its extensive distribution range.