A single specimen of the rare velvetfish Cocotropus keramaensis, collected from the sandy bottom at 53–58 m depth off the Kerama Islands, Okinawa, Japan during dredge surveys in 2017, represents the second collection record for the species, and first with fresh coloration. Morphological characters, including squamation and osteology, are described in detail from radiographs, and scanning electron microscope (SEM) and computed tomography (CT) images. A published underwater photograph taken off Iriomote Island, Okinawa was also identified as C. keramaensis. Diagnostic characters of the species were revised as follows: XII, 9 or 10 dorsal fin rays; II, 7 anal fin rays; 12 or 13 pectoral fin rays; 25 or 26 vertebrae; 3 or 4 + 4–8 = 7–12 gill rakers; 5 distinct preopercular spines; upper jaw longer than lachrymal; 1 small papilla on posterior portion of maxilla; 4 distinct papillae on outer edge of lower jaw; 2nd sensory pore on lower jaw on both sides fused; anterior tip of isthmus attaining to position of 5th mandibular pore; 4 dorsal spines anterior to 3rd neural spine; a large light-colored region anteriorly on spinous dorsal fin; a dark region between maxilla, suborbital stay and lachrymal; many pupil-sized dark spots scattered on pectoral fin; a large blotch below bases of posterior dorsal fin spines; an eyesized blotch below bases of anterior dorsal fin soft rays; head and body reddish when fresh. CT scanning revealed a connection between the sensory pores on the lower jaw and the mandibular canal openings in this species.
The stomiid snaggletooth genus Astronesthes Richardson, 1844 comprises nine species groups (including 40 valid species), plus a further eight species independent of the groups. Among them, the Astronesthes cyanea species group (seven species) is distinguished from all other species by having the following characters: e.g., 42‒50 total vertebrae, 16‒21 dorsal-fin rays, a relatively long chin barbel (but rudimentary in three species), 3 or 4 photophores (part of the ventral row below the pectoral fin) forming an arch, and prominent luminous tissue on the operculum in large specimens. Two specimens (84.6 and 111.1 mm in standard length) belonging to this species group, collected off the Yaeyama and Ogasawara Islands, Japan, were identified as Astronesthes formosana Liao, Chen and Shao, 2006. Although the original description of A. formosana, which noted its close resemblance to Astronesthes indopacifica Parin and Borodulina, 1997, considered the former to differ from the latter in having prominent luminous patch on the lower jaw (vs. absent), a slightly swollen or rounded tip on the chin barbel (vs. slender and simple), prominent luminous tissue on the lower part of the operculum, extending to the lower end of the maxilla [vs. restricted to the middle part of the operculum (in >50 mm standard length specimens)], numerous scalelike spots or prominent patches dorsally on the head and body (vs. sparse), and the upper nostril with more a pair prominent or smearlike luminous patches (vs. a single pair prominent luminous patches), no significant differences were found between the two species in prominent luminous tissue on the operculum, and scalelike spots or prominent patches dorsally on the head (including upper nostril) and body. In addition, the barbel tip shape was found to be of inconclusive value for separating the two species, leaving the presence or absence of prominent luminous patch on the lower jaw as the only valid distinguishing characteristic. Because the features of the two Japanese specimens agreed closely with those in the original description of A. formosana, they were identified as that species, being the first record of the latter from Japanese waters. The new standard Japanese name “Taiwan-tokagegisu” is proposed for the species.
Twelve specimens (71.5–89.9 mm standard length) of the genus Lutjanus (Lutjanidae), collected from Ishigaki-jima Island, Ryukyu Archipelago, southern Japan, were identified as Lutjanus biguttatus (Valenciennes in Cuvier and Valenciennes, 1830), being characterized by the following combination of characters: dorsal fin XI, 12; anal fin III, 8; pectoral rays 15–16; body depth 3.5–3.8 in standard length; preorbital depth 10.8– 16.3 in head length; tongue smooth, without patch of fine granular teeth; a dark longitudinal band from snout to caudal fin base; and two white spots above the lateral line. Dentition of the premaxilla and dentary, including several canine-like (one being long and curved) and many small conical teeth, is illustrated. The collected specimens were determined to be juveniles, due to their coloration matching that of juveniles previously described, in addition to their small body size. Although the coloration of L. biguttatus is similar to that of L. vitta during the juvenile stage, the latter species is distinguished by greater body and preorbital depths. The specimens of the former had been caught in a significantly localized area (in ca. 4 m depth) over several days, indicating the likelihood of their having been schooling, as observed in previous studies of the species. Lutjanus biguttatus is distributed in the Indo-western Pacific, from the Maldives to the Solomon Islands, but had not previously been recorded from Japanese waters. The new standard Japanese name “Futahoshi-fuedai”, given in reference to the two white spots above the lateral line in the collected specimens, is proposed.
Habitat use of Misgurnus anguillicaudatus was surveyed at Tanushimaru, Kurume City, Fukuoka Prefecture, Kyushu Island, Japan, at winter season. The study site was composed as traditional agricultural ditches in parts of the paddy field with some parts of concrete artificial type of the canals. The spatial distribution of M. anguillicaudatus in the study area was examined in 36 square frames (1 m × 1 m) located spaced along agricultural pathway for approximately 20 m. Relationships between presence of M. anguillicaudatus and several environmental factors was analyzed using the generalized linear model (GLM). Result of the GLM analysis showed that probability of the presence of M. anguillicaudatus mainly explained by water depth and the probability increased with increasing water depth.
Compared with the other anguillid eel species native to Japan (Anguilla japonica and A. marmorata), very little is currently known about the Japanese populations of A. bicolor pacifica. Three specimens of the latter (652.4–879.1 mm total length), collected in an irrigation channel on Iriomote Island, southern Japan, were examined, and the phylogenetic and morphological characters of the species discussed. The stomach contents of two specimens included a number of frog remains.
Distribution of the Indo–Pacific eel, Anguilla marmorata, and habitat water temperatures in Oita Prefecture were investigated using literature review, sample surveys, field sampling, and temperature logging. Thirteen records from nine localities were confirmed by literature and voucher specimens. Field sampling revealed the current distribution of the species at eight localities. Winter water temperatures at spring-fed stations where A. marmorata was present differed significantly from those at stations where A. marmorata was absent, the former being higher. Accordingly, over-wintering under the substrate in warmer water temperatures is likely to contribute significantly to the survival of A. marmorata at the northern limit of its range.
Exotic populations of Acheilognatus tabira found in northern Mie Prefecture, and subjected to nucleotide sequencing of the mitochondrial DNA cytochrome b region, were determined to represent the Hokuriku (A. t. jordani) and Kinki-Sanyo (A. t. tabira) lineages. The first record of A. t. jordani from outside its native distribution area (Japan Sea side of western Honshu), it is likely to be a viable population due to the presence at the sampling site of the freshwater mussel Beringiana fukuharai (Unionidae, Cristariini), with which the former likely has a spawning relationship.
A single yellowtail specimen (514.0 mm standard length), collected in the open ocean of the central North Pacific (31˚38.3'N, 163˚24.5'W), was identified as Seriola aureovittata Temminck and Schlegel, 1845, following morphological observations and genetic analysis. Commonly believed to be distributed in coastal areas off East Asia, the species may occupy a wide range of habitat in the western and central North Pacific (supported also by previous fisheries records). Seriola dorsalis (Gill, 1863), a very similar congener, is distributed in the eastern North Pacific, the two species being considered separated by the East Pacific Barrier.