First description and collection records of juvenile slime flounder Microstomus achne from the eastern and western coastal waters off Honshu Island, Japan

Morphological characteristics and body pigmentations of juvenile slime flounder Microstomus achne were described from one specimen [27.8 mm total length (TL)] collected off Niigata Prefecture from the Sea of Japan (35 m depth) in May 1993 and from three specimens (30.1, 36.2, and 40.9 mm TL) collected off Fukushima Prefecture on the Pacific coast of northern Japan (15 and 50 m depths) during April–May 2008 and 2009. These age-0 juveniles had a characteristically slenderly oval-shaped body and slightly protruded front nostrils. Sparsely distributed melanophores and xanthophores were clearly visible throughout the ocular side of one specimen, which was judged as a newly settled juvenile, whereas several spots aggregated by small melanophores were found in the others with elongated pectoral fins and small cycloid scales. Melanophores were only slightly detectable on the blind side. Comparisons of the depth distributions of slime flounder juveniles and sympatrically collected age-0 pleuronectids ( Pseudopleuronectes herzensteini , Pseudopleuronectes yokohamae , Platichthys bicoloratus , and Dexistes rikuzenius ) suggested that slime flounder can settle on broad nursery areas of coastal and offshore pleuronectid flatfishes, probably depending on local oceanic conditions during the protracted pelagic phase.