Morphometric changes in the Ussurian bullhead, Leiocassis ussuriensis, and the Korean bullhead, Pseudobagrus fulvidraco, were observed during the early period of growth. Yolk length, yolk height, and yolk volume in the two species decreased within 9 days post-hatching (DPH) (p<0.05). The body lengths and body heights of both species increased gradually to 150 and 130 DPH, respectively (p<0.05). The horizontal distance between the anteriormost extension of the head and the anterior insertion of the pectoral fin, the anteriormost extension of the head × the verticality position of the anterior insertion of the primary dorsal fin rays, and the anterior insertion of the primary dorsal fin × the anterior insertion of the pectoral fin were greater in the Korean bullhead than in the Ussurian bullhead (p<0.05). However, the relative sizes of the head region, pectoral fin, ventral fin, and anal fin were greater in the Ussurian bullhead than in the Korean bullhead (p<0.05), and relative body depth and the size of the outer-mandible barbel were greater in the Korean bullhead than in the Ussurian bullhead (p<0.05). The growth curves of the morphometric characteristics of both species were divided into three types.
Keywords: Korean bullhead; Leiocassis ussuriensis.; Morphometric characteristic; Pseudobagrus fulvidraco; Ussurian bullhead.