Longitudinal changes in fish assemblage were studied in the Ogata River and djoining tributaries, northeastern Kyushu, southern Japan, in October 2003, and February nd August 2004. A total of 18,015 individuals (14 species/subspecies representing 7 amilies) were recorded at 15 stations, by observers using snorkels. A major fish community ransition was apparent from headwater stations with a simple assemblage dominated by mago salmon Oncorhynchus masou ishikawae and Chinese minnow Phoxinus oxycephalus, o downstream stations with more complex assemblages dominated by cyprinid fishes, such s Japanese dace Tribolodon hakonensis and dark chub Candidia temminckii. Multivariate nalyses separated the 15 stations into three groups: headwater stations with a salmon/innow-dominated assemblage (415–820 m altitude), a transition zone with a dace/chub/innow-dominated assemblage (260–397 m), and downstream stations with a cyprinidominated assemblage (232–255 m). The fish assemblage structures were considered to e influenced by longitudinal environmental gradients, being significantly correlated with ix environmental variables (topographic type and altitude, and stream gradient, mean etted width, discharge and minimum daily mean water temperature) showing monotonic hanges over the length of the stream investigated (16.3 km). On the other hand, cyprinid opulation densities did not show such changes, but declined within the transition zone ownstream from erosion-control dams, suggesting that such densities were affected by maller spatial scale factors, including dam-induced habitat degradation.
Accurate descriptions of distribution and habitat are important for effective We examined the distribution patterns and habitat preferences of two related gizzard shads, Nematalosa japonica and N. come, based on specimens, reports and fish market research in the Ryukyu Archipelago. Both species are N. japonica to the north of Okinawa-jima Island, and come in waters off Amami-ohshima Island and the Okinawa Islands, thereby being distributed at Amami-oshima Island and Okinawa-jima Island. Natural between the two species, found only at Okinawa-jima Island indicated that is a natural hybrid zone. Analysis using a random forest method and fish market N. japonica was most affected by tidal flat type tidal flats), the species being dominant in restricted fishing grounds (Nakagusuku and Haneji coastal waters) that include many coastal tidal flats. However, N. come fected by bottom sediment type, the species being dominant in a of fishing grounds (Kin and Nago Bays, and Nanbu-higashi, Nago-higashi, Nakijin Shioya coastal waters). Thus, the distribution pattern of the two species at OkinawaIsland was affected by environmental factors, such as tidal flat type, and area and sediments. Our findings indicated a clear discontinuity in home range between the fort (CPUE) of the two species has highly altered environments. These findings indicated that the diminution of suitable Okinawan populations of both species. Accordingly, the two Nematalosa species are as being of good indicators of the health and conservation of shallow areas, such as tidal flats. Shallow habitats should be conserved to preserve healthy populations of the two species.
A recent revision of the systematics of the family Apogonidae recognized four (two being new), 14 tribes (all new) and 38 genera, one of which was new. Apogon or Rhabdamia, Apogonichthyoides, Nectamia sensu strictoZoramia. All apogonid subfamilies, tribes and genera occurring in Japanese waters are given fixed standard Japanese names. Based on the rules operationally proposed twenty-five new standard Japanese names were given to three subfamilies, 13 tribes Japanese name (at generic level for , subfamily and tribe level taxa, and a specific level for genera) being designated Additionally, a new standard Japanese Senou-hikari-ishimochi, was proposed for a Japanese species, Siphamia senoui,
A genetic analysis of wild-caught tetsugyo from Yutori-numa Pond, Miyagi Prefecture, a long-finned fish of uncertain origin designated as a National Natural Monument in Japan, demonstrated that some specimens were hybrids of goldfish (Carassius auratus) and crucian carp (genus Carassius). Phylogenetic analysis of sequences from part of the D-loop region of mitochondrial and nuclear DNA of 87 Yutori-numa tetsugyo indicated that 66 belonged to the goldfish group and 21 to the Japanese crucian carp group, subsequent PCR-RFLP analysis of c-myc gene revealing three different restriction fragment digest profiles, 21 and 60 specimens possessing goldfish or Japanese crucian carp genes, respectively, and the remaining 6, both genes, indicating their hybrid origin.
Three specimens (39.9–161.0 mm SL) of an ophidiid genus Neobythites, were collected off Zanpa Cape, Okinawa Prefecture, southern Japan, in December 2012. The specimens were identified as Twospot cusk Neobythites bimaculatus Nielsen, 1997 in having two spines on the hind margin of the preopercle, pelvic fin rays not reaching the anus and two ocelli on the middle of the dorsal fin. Nielsen (2002) referred to a small specimen (73 mm SL) having two faint dark spots on the anal fin. The smallest specimen (39.9 mm SL) reported here, although smaller than Nielsen’s specimen, has no spots on the anal fin. This species was previously known from New Caledonia, Australia and the South China Sea. These specimens are the first record of the species from Japan.