A taxonomic review of the scorpionfish genus Scorpaenopsis in Japanese waters recognizes 12 species as valid: viz., S. cirrosa, S. cotticeps, S. diabolus, S. macrochir, S. neglecta, S. orientalis, S. oxycephala, S. papuensis, S. possi, S. ramaraoi, S. venosa and S. vittapinna. Of these, S. oxycephala, S. ramaraoi and S. vittapinna are reliably reported from Japan for the first time, including the northernrnost record of each. Distributional ranges in Japanese waters of four other species are extended, viz. S. macrochir (northernmost record from Sesoko Island off Okinawa Island, Ryukyu Islands; new record from the Ogasawara Islands), S. papuensis (northernmost record from Wakayama Prefecture; new records from Iriomote Island, Ryukyu Islands and Amamioshima, Kagoshima Prefecture), S. possi (new records from Kerama Islands and Izu Islands) and S. venosa (northern-most record from Kochi Prefecture). Three species, previously identified by Japanese researchers as S. cirrosa (Ryukyu Islands var.), S. brevifrons, S. oxycephala and Scorpaenopsis sp., are herein re-identified as S. possi, S. vittapinna, S. papuensis and S. venosa [or S. possi (part)], respectively. Five new standard Japanese names are proposed for S. macrochir, S. orientalis, S. oxycephala, S. ramaraoi and S. venosa. The configuration of a bulge on the snout and posterior nostrils found in S. macrochir constitute a newly-recognized diagnostic character for the species. Each of the above 12 species is redescribed on the basis of specimens collected from Japanese waters and compared with each other in detail. A key to the species of Japanese Scorpaenopsis is included.
The distribution range of the Japanese spined loach Cobitis biwae is in the middle stretches of rivers in most of Honshu and Shikoku Islands. In Kyushu Island, its close relative, the yamato complex sensu Saitoh et al.(2000), is distributed, but C. biwae is thought to be absent there. Comparison of the morphological characters and erythrocytic size revealed that the specimens of Cobitis collected from the Oita River system in Kyushu Island are the tetraploid form of C. biwae. Subsequent mitochondrial DNA analyses also supported this finding. Taking the connection pattern of drainages during glacial periods into consideration, it is suggested that C. biwae from the Oita R. s. is native.
The matter flow from terrestrial plants and aquatic algae to juvenile masu salmon was estimated in the Gokibiru River, Hokkaido, Japan. The stomach contents of masu salmon, stable isotope rate of invertebrates and plants, and assimilatory rate between masu salmon and invertebrates were analyzed. The weight composition of masu salmon stomach contents was converted into assimilation composition following a rearing experiment. The contribution of terrestrial plant matter in invertebrate diets was estimated by stable isotope analysis. The total contribution of terrestrial plant matterial to diets of juvenile masu salmon was 42.2-78.1%. The main mediators between juvenile masu salmon and terrestrial plants were aquatic invertebrates (e.g., Gammaridea and Heptageniidae) in summer, autumn and winter, and terrestrial insects (e.g., Lepidoptera larva) in spring.
The reproductive ecology and early life history of the bagrid catfish, Pseudobagrus nudiceps, were investigated in the field and laboratory. The species reproduced between late June and early August in a tributary of the Kinokawa River, Wakayama Prefecture. During the reproductive period, large mature males maintained a territory around crevices along shoals and banks. Mating behavior was observed there and in an aquarium, the field observations being the first for any Asian bagrid. When a female visited a male's territory, a series of behavioral activities, including courting, embrace and egg-stirring by the female were observed. Females (115-137mm SL) produced 1200-3000 developed ovarian eggs, apparently spawning in the nests of several males. Parental males cared for the eggs by fanning and cleaning, using the pectoral and pelvic fins, and displayed aggressive behavior against fish approaching the nest. Spawned eggs were adhesive and between 2.5-2.7mm in diameter. The eggs hatched 2.5-3 days after fertilization at an average water temperature of 26°C. At 2 days posthatching, the larvae began to move at night, leaving the nest after 7 days. Brood parasitism by the Japanese minnow, Pungtungia herzi, was frequently observed in the nests of Pseudobagrus nudiceps.
To clarify the hatching season and size of the Ryukyu-ayu, Plecoglossus altivelis ryukyuensis, newly-hatched larvae were collected in the Yakugachi and Kawuchi Rivers, Amami-oshima Island, between November-March in 1995, 2001 and 2002. Hatching began from mid-November when the water temperature had decreased to about 18°C. This was compared with hatching onset dates recorded for Ayu P a. altivelis at various locations around Japan, a significant negative correlation between latitude and onset of hatching being found. This was believed due to the lowering of water temperatures being delayed in the more southern latitudes, hatching starting when water temperature had decreased to around 20°C. The notochord length of newly-hatched Ryukyu-ayu larvae increased and water temperature decreased with each month. Larger larval size provide greater resistance to low water temperatures.
The intraspecific mitochondrial DNA (mtDNA) phylogeny of a Japanese brackish water goby, Mimizu-haze (Luciogobius guttatus) (Perciformes: Gobiidae), was inferred from partial nucleotide sequences of the mitochondrial 12S and 16S rRNA genes (1, 053 bp). The resultant mtDNA tree showed two major intraspecific lineages, and suggested that there were two cryptic species in the goby. One of the major lineage also showed two haplotype groups, one being distributed on the northeastern Japan and another on southwestern Japan and Ryukyu Islands. The mtDNA divergence between the two haplotype groups suggested that those mtDNA groups have been isolated for about one million years.
A single example of the lutjanid fish Pinjalo pinjalo (MUFS 22234, 420 mm in standard length), collected by set net (maximum depth 31m) off Isashiki, Sata, Kagoshima, Kyushu Island, Japan (130°41'25″E, 31°6'6″N), was iden-tified on the basis of having 11 dorsal fin spines, 14 dorsal fin rays, 3 anal fin spines, 10 anal fin rays, the caudal fin deeply emarginated and dark diagonal lines following the scale rows on the nape and dorsal ca. 1/2 of body. The specimen represents the northernmost record of the species and first example of a larger specimen from Japanese waters. Finally, P. microphthallmus Lee, 1987 (April) is commented as a junior synonym of P. lewisi Randall, Allen and Anderson, 1987 (October) on the basis of the original description.
Mating behavior of aquarium-held freshwater catfish, Pseudobagrus nudiceps (Bagridae), was observed. Some 22-33 h following human chorionic gonatropin injection, males patrolled the nest area, while females maintained a stationary midwater position (premating behavior). Mating began with a female visiting a male's nest, successive stages including male'embracing' of the female, female stirring of eggs and female departure. Duration of the ‘embrace’ was 24.4-26.0 s, mating behavior sequences being repeated 10-18 times with intervals. Spawning was performed in the male's nest. The number of eggs, measuring 1.4-2.2 mm in diameter, laid by a single female was estimated at more than 1000. At 22.5°C, the eggs started to hatch 65.0-69.5 h after fertilization. After spawning, the male stayed near the eggs.
Three landlocked populations of an amphidromous goby, Rhinogobius sp.CO, in San-nome-gata Lake, Akita Pref., Ukinuno Pond, Shimane Pref., and Cheonmi River, Jeju Island, Korea, were identified and evidenced by allozyme and otolith analyses. Line analysis of strontium: calcium ratios along the life history transect of their otoliths showed relatively stable values as compared to those of amphidromous conspesifics, indicating the absence of sea-going career. The San-nome-gata and Ukinuno populations would have been landlocked in the Jomon (6000 years ago) and the Hakuho (1300 years ago) periods, respectively. Landlocking of the Cheonmi population may have occurred occasionally.