Recently, an unusual sea bass specimen, with all fin rays being extremely long (Fig. 1), was collected from Enshu-nada waters, central Japan. From its general features, the specimen was considered to belong to the genus Lateolabrax, presently known from three species, including the Japanese sea bass, Lateolabrax japonicus, spotted sea bass, Lateolabrax maculatus (sensu Kim et al. 2001; Liu et al. 2006), and flat sea bass, Lateolabrax latus. This study aimed to identify the longfinned specimen on the basis of morphological and genetic comparisons with the above Lateolabrax species. The long-finned specimen was collected by trawl in waters off the Tenryu River estuary (34 3804000N, 137 4704000E) on 23 March 2010. Following 3 days storage in ice water, the specimen was frozen at -20 C, before subsequent thawing and removal of the liver and muscle tissues for isozyme analysis. The specimen was then fixed in 10% formalin and deposited in Shizuoka Prefecture Nature Learning Resources Center (catalogue no. SPMN-h 40001). Morphological and genetic examination methods followed Yokogawa and Seki (1995). However, the pectoral scaly area length (PSAL), as defined by Yokogawa and Seki (1995), is given as a proportion of standard length as opposed to pectoral fin length, since the latter was extremely long in the present specimen (Fig. 1). Measurement data for L. japonicus and L. maculatus were based on Yokogawa and Seki (1995), and for L. latus, obtained from 11 specimens deposited in the Laboratory of Marine Biology, Faculty of Science, Kochi University (BSKU 100553, 100554, 100556–100561, 101826 and 101835) and the Tokushima Prefectural Museum (TKPM-P 00972), all from the Seto Inland Sea, Japan. Further, for osteological comparisons, the long-finned specimen was radiographed together with L. japonicus specimens (TKPM-P 00352, a sample lot) from the Seto Inland Sea. For isozyme analyses, control samples utilizing frozen preserved tissues from 7 L. japonicus (SPMN-h 40002– 40008, from Lake Hamana, Japan), 4 L. maculatus (BSKU 100540, 100542, 100545, 100551, from Mokpo, Korea) and 4 L. latus (BSKU 100554, 100556, 100557, 101826) were used for mobility comparisons with electrophoretogram bands from the long-finned specimen. Allelic frequency data for the former three species were also taken from Yokogawa (1998). Isozymic loci definitions generally followed Yokogawa (1998), with some modifications in Yokogawa (2004) (viz. GAPDH-1* and GAPDH-2* loci renamed G3PDH-1* and G3PDH-2*, respectively; LDH-1* locus newly added, the LDH* locus being renamed as LDH-2*; PROT-2* locus reidentified as CK* and PROT-3* locus renamed as PROT-2*). Genetic relatedness between individuals (Rxy) of three Lateolabrax species (data based on Yokogawa 1998) and the long-finned specimen was calculated following Queller and Goodnight (1989), and it was converted into distance between individuals (D) following Noguchi et al. (2003) (D = 1 Rxy). Subsequently, a dendrogram was constructed from the D values by using the unweighted pair group method with arithmetic mean (UPGMA) with the MEGA software created by Tamura et al. (2007). Morphological characters. Morphological measurements clearly demonstrated that the proportional lengths of K. Yokogawa (&) 13-5 Higashihama, Tadotsu-cho, Nakatado-gun, Kagawa 764-0016, Japan e-mail: gargariscus@ybb.ne.jp