Population structure of the sailfin sandfish, Arctoscopus japonicus (Trichodontidae), in the Sea of Japan

Fluctuations in distribution and relative abundance of Japanese Spanish mackerel, Scomberomorus niphonius, in the Yellow Sea, East China Sea and Sea of Japan

The origins and migration routes of migrating juvenile chum salmon Oncorhynchus keta along the Pacific coasts of Hokkaido and Honshu were examined on the basis of seasonal and geographical distribution data. Three groups of migrating juveniles were recognized in the survey area. The first group in the waters from Tsugaru Strait to Hidaka from late May to early June was suggested to originate from the Japan Sea area of northern Honshu or from Mutsu Bay, the second, occurring in large numbers off Hachinohe from mid-June to late June was suggested to be from the Pacific coast of northern Honshu. The third, occurring in large numbers along the Pacific coast of Hokkaido from early July to mid-July, was estimated to be composed of juveniles from the Pacific coast of Honshu and from nearby localities. The migration routes of the juveniles are considered to be along the coast, and offshore migrating juveniles of various origins are thought to migrate along the Pacific coast of eastern Hokkaido.

A taxonomic review of the cottid genus Cottiusculus Jordan and Starks 1904 established three species, C. nihonkaiensis sp. nov., C. schmidti, and C. gonez. Cottiusculus nihonkaiensis sp. nov., which had been previously confused with C. schmidti, is described on the basis of 32 specimens (44.8-77.9 mm, SL) collected from the Sea of Japan. The new species is very similar to C. schmidti in having a curved barbless uppermost preopercular spine and the lateral line extending past the caudal fin base, but is distinguishable as follows: nasal spines simple or sometimes weakly bicuspid (vs. deeply bicuspid in C. schmidti); first dorsal fin not elongated in either males or females (vs. elongated in males); ventral lateral and lateral line cirri present (vs. absent). The former is known from the Sea of Japan coasts of Hokkaido, Honshu, Kyushu and the Korean Peninsula, and Volcano Bay, Hokkaido, and the latter from the Pacific coast of Tohoku District, Japan. Cottiusculus gonez, known from the Sea of Japan, Sea of Okhotsk and Pacific coast of Hokkaido, is characterized by having a simple nasal spine, the uppermost preopercular spine almost straight with two small cusps dorsally, posterior cusp barbed, and the lateral line almost reaching to the caudal fin base. A lectotype of C. gonez is designated here. Sequence differences in the cytochrome b gene among the above three species of Cottiusculus are also presented.

From already published tsunami tables of author (1985, W), Iida (1984, I) and Rika-nenpyo (1986, R), we study three problems. Obtained results are follows.1. Comparison of tsunami tables.1) Number of data in I's table is about two of it in W, s and R, s ones.2) The tsunami sources adapted in only I, s table distribute on the coasts of Japan Sea, the inlands and coasts of southwestern Japan, and off southeastern coasts of Hokkaido and the Sanriku coast. Some data of I's table are doubt, because the tsunami sources situate on the inlands.2. Distribution of maximum wave heights.1) The eastern coast of Kii Peninsula is attacked five times by tsunami with the wave height of more than five meters.2) The Sanriku coast is attacked four times by tsunami with the wave height of more than twenty meters.3. Locality of the coast on tsunami propagation.The coefficient on propagation distance (log Δ) in equation calculating tsunami magnitude Mt is one for all coasts in Japan. However, it differs from one by calculating at many tidegage stations. The values are 0.62 in the Pacific coast of Hokkaido, 1.16 in Hakodate to Sanriku coast and 0.92 in the Pacific coast of sothwestern Japan.They will depend mainly on the difference of submarine deformation, such as the trench, the trough and the continental shelf.

Phylogeography of the sandy beach amphipod Haustorioides japonicus along the Sea of Japan: Paleogeographical signatures of cryptic regional divergences

Response of lower trophic ecosystem in the Japan Sea to horizontal nutrient flux change through the Tsushima Strait

To investigate the genetic variation and population structure of Pacific herring in the Yellow Sea and the genetic differentiation between the Yellow Sea and the Sea of Japan, fragments of 479-bp mitochondrial DNA control region were sequenced for 110 individuals collected from three different periods in the Yellow Sea and one locality in the Sea of Japan. High haplotype diversity and moderate nucleotide diversity were observed in Pacific herring. AMOVA and exact test of population differentiation showed no significant genetic differentiations among the three populations of the Yellow Sea and suggested the populations can be treated as a single panmictic stock in the Yellow Sea. However, a large and significant genetic differentiation (ΦST=0.11; P=0.00) was detected between the populations in the Yellow Sea and the Sea of Japan. The high sea water temperature in the Tsushima Strait was thought a barrier to block the gene exchange between populations of the two sea areas. The neutrality tests and mismatch distribution indicated recent population expansion in Pacific herring.

Middle to lower crustal earthquakes in the western East Sea (Sea of Japan) and their implications for neotectonic evolution

Using path analyses, we investigated relationships between size at release from hatcheries, the early marine growth of juveniles, and adult return rates for chum salmon from five river stocks of Hokkaido, Japan, in relation to sea surface temperature during ocean residence. Marine growth was estimated using scales collected from 11 760 adults of age 0.3 (1980–2004). The growth and survival of each stock appeared to have a different suite of regulatory processes. Interannual variability in return rates was mainly regulated by size at release in two stocks from the Sea of Okhotsk. A similar relationship was found in one stock from the Sea of Japan, but growth during coastal residency also affected their return rates. In two stocks from the Pacific coast of Hokkaido, variability in return rates was not related to size at release or to the coastal growth of juveniles, but with offshore growth in the Sea of Okhotsk, the nursery area for juveniles after leaving Japanese coastal waters. Whereas coastal growth tended to be negatively correlated with size at release in some stocks, offshore growth was positively associated with the August–November sea surface temperature in all stocks. This study confirmed that mortality of juvenile salmon occurred in two phases, during the coastal residency and the late period of the growing season, but the relative importance of both phases varied by stock and region, which probably regulated year-class strength of Hokkaido chum salmon.

January 1997 the Russian tanker 'NAKHODKA' spilled in to the Sea of Japan about 5000 tons of heavy fuel oil type C. Most of it reached the coast of Japan and damaged the environment. This incident forced the development of the operational system for the prediction of oil spills in the Sea of Japan. As a part of this system the model for oil spill modelling is presented. The modelled climatological sea currents were used in these simulations, generated by the three-dimensional primitive ocean circulation model with 10minute horizontal resolution and 19 vertical levels. The model was forced by climatological atmospheric winds and heat fluxes. The wind currents in the upper sea layer were estimated by the wind data of ECMWF with 6 hours time and 0.5625-degree spatial resolution. The vertical structure of the total currents was interpolated using both wind driven currents and the climatological model currents data at the model levels. The oil spill was modelled with the particle tracking techniques. The model included the advection by currents, random diffusion, the buoyancy effect and the parameterisation of oil evaporation, biodegradation and beaching. For the deep sea the parameterisation of diffusion depends from the stratification, taken from the ocean circulation model output. The results demonstrated the defined relation with the observed propagation of the oil along the coast of Japan and highlighted the most important directions for the model development. The main is the realisation of the model for the real-time simulations and forecasts of the ocean currents with the fine resolution in the upper layer of the Sea of Japan. Transactions on Ecology and the Environment vol 20, © 1998 WIT Press, www.witpress.com, ISSN 1743-3541

Heavy rain in western Japan was broadly induced by the stagnation of the Baiu front during 5-7 July 2018. This study hypothesizes that cold air advection over the Sea of Japan intensified by Typhoon Prapiroon (Typhoon No. 7) was one of the triggering factors for the formation process of the Baiu front over western Japan. Typhoon Prapiroon passed over the Sea of Japan on 4 July and became extratropical at approximately 40°N on 5 July. During its passage, the strong southward pressure gradient force to the north of Typhoon Prapiroon broke down the convergence line of the Baiu front that remained at approximately 45°N before 4 July and thick cold air from the Okhotsk High flowed over the Sea of Japan. The Okhotsk High expanded toward the Sea of Japan and enhanced cold air advection to the north of western Japan. As a result, the Baiu front was stationary at approximately 35°N after 5 July. In addition, the westerly jet in the east of an upper-level trough deepened along the typhoon track was associated with the adiabatic component of the ascending motion over the isentropic upslope and was suggested to contribute to the maintenance of Baiu frontal convection.

Species composition of fish is decribed for the Japan Sea on the data of Pacific Fish.Res.Center (TINRO), Russia (about 10,000 bottom and pelagic research trawlings at the depth 5-750 m obtained in 1980-2005), National Fish.Res.Dev.Inst. (NFRDI), Rep.Korea (about 100 research cruises conducted since 1994 with trawling at the depth 30-2550 m), coastal fishery statistics, and cited data. All past revisions in the taxonomy are registered. Some general ecological and zoogeographical features of the Japan Sea are revealed. In total, 962 fish species dwell in the Japan Sea, and 738 of them (77 %) are registered in the EEZ of Russia and Korea. In the analyzed TINRO and NFRDI surveys, 419 fish species were found, mainly in research trawls (389) and patially only in commercial catches in coastal waters (30). On the other hand, 872 fish species (91 % of the total list) occur in the EEZ of Japan. The species belong to 42 orders (Perciformes absolutely dominates among them by number of species - 432) and 215 families (the most numerous are Cottidae - 51 species, Gobiidae - 48 species, and Stichaeidae - 41 species). From zoogeographic point of view, they have mostly tropical-subtropical (488 species), lowboreal-subtropical (210 species), and lowboreal Asian (128 species) origin; only 14 species are endemics of the Japan Sea, 17 species are endemics of the Japan and Okhotsk Seas, and 171 species are endemics of the southern part of the North-West Pacific (Japan Sea, Yellow Sea, East China Sea, and Pacific coast of Japan). The major part of fish species in the Japan Sea inhabit mainly sublittoral (28 %) and elittoral (28 %) biotopes; diversity of stenobathic species decreases both shoreward and toward the continental slope. Bottom (46 %) and near-bottom (26 %) species absolutely prevail over pelagic ones (20 %), whereas 8 % of the species are considered as bottom-pelagic ones.

The dynamics of the northern and western Sea of Japan sailfin sandfish ( Arctoscopus japonicus ) stocks (NSJ and WSJ, respectively) varied simultaneously until the mid-1970s but differently thereafter. To identify the mechanisms underlying these dynamics, we evaluated the impact of environment and harvesting on NSJ by developing a recruitment model and simulating NSJ dynamics. The model was constructed based on egg production, density effect, and water temperatures in winter and spring, which correlated significantly and positively with the estimated surface mixed-layer depth. Winter water temperatures and egg production were variables common to the two stocks. Our results suggest that simultaneous dynamics resulted from similarities in variations in winter water temperatures for each stock and the difference in dynamics resulted from NSJ depletion caused by overfishing. We suggest management strategies to prevent NSJ depletion caused by unfavorable environmental conditions and overfishing, as well as to allow improved biomass recovery while taking advantage of favorable environmental conditions, and avoid further exploitation of previously depleted NSJ.

Analyses of phylogeographic patterns and genetic diversity provide fundamental information for the management and conservation of species. However, little is published about these patterns in Japanese kelp species. In this study, we conducted phylogeographic analyses of a canopy-forming kelp, Eisenia bicyclis, based on genome-wide SNPs identified by ddRAD-seq. We obtained 1,299 SNPs for 76 samples from nine localities across the distribution. STRUCTURE, NeighborNet, and discriminant analysis of principal components consistently showed high genetic differentiation among the Eastern Pacific, Central Pacific, and Sea of Japan coastal regions. Relatively strong gene flow was detected only within populations in the Eastern Pacific and in the Sea of Japan. Genetic diversity and genetic uniqueness were high in the Central Pacific and low in the Sea of Japan. These results suggest that there were at least three independent refugia corresponding to the three regions during the Last Glacial Maximum (LGM). Furthermore, relatively larger populations in the Central Pacific and smaller populations in the Sea of Japan have been maintained in the demographic history from before the LGM to the present. These phylogeographic histories were supported by an Approximate Bayesian Computation analysis. From a conservation genetics perspective, the loss of southern populations in the Central Pacific would greatly reduce the total genetic diversity of the species. Southern populations in the Sea of Japan, which have relatively low genetic diversity, may be highly vulnerable to environmental change, such as heat waves and increased feeding. Therefore, careful monitoring and conservation are needed in the two regions.

A previous molecular-genetic analysis of clonal cultures and single cells of Ostreopsis spp. that were isolated from Peter the Great Bay (the Sea of Japan) revealed three different genotypes according to the nucleotide sequences of ribosomal DNA (rDNA). Of these, Ostreopsis sp. 1 was earlier found only off the coast of Japan and described as being the most common and highly toxic. We have obtained further molecular evidence and have studied the morphological features of cells from one of the Ostreopsis strains with this genotype and some aspects of its growth at salinities of 24, 28, and 32‰. The results showed that in cells from the Russian coast of the Sea of Japan, the third apical (3') and the third precingular (3") plates do not adjoin one another, being separated by the elongated second apical (2') plate. Cells of Ostreopsis sp. 1 from the Russian coast are significantly larger than Ostreopsis sp. 1 cells with the same genotype from the coast of Japan. Salinity did not have a substantial effect on the growth of Ostreopsis sp. 1. The growth rate varied from 0.24 to 0.35 divisions per day, with maximum values at a salinity of 24‰. When salinity decreased to 24‰, the exponential growth phase was significantly extended and the maximum cell concentration doubled.