Origin of juvenile chum salmon <Emphasis Type="Italic">Oncorhynchus keta</Emphasis> (Salmonidae) in the Sea of Okhotsk coastal waters off South Sakhalin

Based on the data of the analysis of distribution of juvenile chum salmon Oncorhynchus keta that were marked at salmon hatcheries in the southern part of the Sakhalin Island and Japan it has been established that their stocks in the Sea of Okhotsk coastal waters off South Sakhalin and Japan are of mixed origin. One part of the stock is composed of juveniles from hatcheries located in the southern part of Sakhalin, and the other part is composed of migrants from the waters adjacent to Japan. The first part is formed by juveniles both from hatcheries on the Sea of Okhotsk and Sea of Japan coasts of South Sakhalin. The second part is formed by juveniles reared at hatcheries in all regions of Japan: the Pacific and Sea of Okhotsk coasts of Honshu and Hokkaido, and from the Sea of Okhotsk coast of Hokkaido and Izmena (Nemuro) Strait. In July, in the Sea of Okhotsk coastal waters off South Sakhalin, the length and weight of most juvenile chum salmon of Japanese origin exceed 10 cm and 10 g, and juveniles of Sakhalin origin are always smaller than 10 cm and 10 g, which makes it possible to differentiate juveniles in trawl catches.     

Distribution of the Eelpout Lycodes soldatovi(Pisces: Zoarcidae) over the Continental Slope of the Sea of Okhotsk

The eelpout Lycodes soldatovi was found at depths of 153 to 1005 m in the Sea of Okhotsk; however, it usually inhabits the depth range of 400 to 800. The mean and maximum abundance and the biomass of this species were 198.5 and 1037 individuals per km² and 173.7 and 1275 kg/km², respectively. In view of the data on the distribution of young fish (up to 30 cm in total body length) and the reports on the absence of Lycodes larvae, a hypothesis was developed that this species spawns predominantly in the waters off western Kamchatka and eastern Sakhalin at the depth range of 700 to 900 m. Large individuals (>50 cm) exhibit higher migratory activity and are more tolerant of environmental conditions. That is why they are encountered throughout the distribution area of this species, even in subzero temperature areas. Lycodes soldatovi seems to be a typical inhabitant of the Sea of Okhotsk, except for the waters off the South and Central Kuril Islands and the Pacific waters off the North Kuril Islands.     

The distribution and abundance of scyphomedusae (Scyphozoa) of the family Ulmaridae in the pelagic zone of the Sea of Okhotsk and the Sea of Japan

The distribution and abundance of jellyfish of the family Ulmaridae was studied based on the data of trawl surveys conducted in the Sea of Okhotsk (1998–2006) and the Sea of Japan (2003) in the fall. The jellyfish Aurelia aurita mainly inhabits the waters of the Sea of Japan, while in the Sea of Okhotsk small quantities of this species were recorded in southern areas, and solitary individuals, off North Sakhalin. Aurelia limbata tends to shelf waters of the Sea of Okhotsk, being less abundant in the southern deepwater area and in the Sea of Japan. Phacellophora camtschatica, in contrast, aggregates mostly over deep basins, whereas in shallow areas a significant quantity of this species was found only off West Kamchatka. In the northern Sea of Okhotsk, the species A. limbata dominated in biomass and abundance among Ulmaridae. During the studied period, its biomass varied from 27 to 803 kg/km² and its abundance varied from 69 to 1706 ind/km². In the southern Sea of Okhotsk, as a rule, P. camtschatica prevailed (1–16 kg/km² and 6–46 ind/km²). In the Sea of Japan, the most abundant species was A. aurita (29 kg/km² and 104 ind/km²). The jellyfish size structure in catches is presented.     

On genetic differentiation of the Pacific cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis> tilesius, 1810 (Gadiformes: Gadidae)

The variability of the Gmo3, Gmo34, Gmo35, and Pgmo32 DNA microsatellite loci in Pacific cod Gadus macrocephalus samples from different areas of the North Pacific was analyzed. The data obtained show that Pacific cod from the southern Kuril Islands significantly differs from the populations of the Bering Sea, the Sea of Okhotsk, and the coastal waters of Canada (the microsatellite loci Gmo3 and Pgmo32 bear the highest differentiating capacity). Despite the significant geographical remoteness of these areas from one another, the above three Pacific cod populations exhibit a high degree of similarity (I = 0.997–0.999).     

Variability of DNA microsatellite loci in populations of Pacific cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis> Tilesius (Gadidae)

Despite almost a hundred years of studies on the Pacific cod’s biological and ecological peculiarities, many of them and especially population structure remain poorly understood. The variability of DNA microsatellite loci Gmo3, Gmo34, Gmo35, Pgmo32, and Gmo 19 was analyzed for the cod sampled in different areas of the North Pacific. The cod sampled nearby the Southern Kurils, differed significantly by Gmo3 and Pgmo32 compared to the populations inhabiting the Bering Sea, the Sea of Okhotsk and the coastal waters off Canada. Further, Pacific cod of the three latter populations demonstrated high similarity (I = 0.996) in spite of considerable geographic remoteness of these areas from one another.     

Species composition,distribution, and specific features of feeding of Fish Larvae,and fry in the Sea of Okhotsk from October to December 2007

Ichthyoplankton of the Sea of Okhotsk from October to December 2007 comprised larvae and fry of eight fish species belonging to five families. The larvae of lord Hemilepidotus gilberti, white-spotted greenling Hexagrammos stelleri, and Atka mackerel Pleurogrammus monopterygius were the most widespread and numerous in the study period. Fish larvae from October to December 2007 were seined over the vast water area of the Sea of Okhotsk, maximum catches were made in waters of western Kamchatka. The food spectrum of larvae of five fish species (H. gilberti, Hexagrammos octogrammus, H. stelleri, P. monopterygius, and Bathymaster signatus) included approximately 20 plankters. Irrespective of species belonging, copepods Pseudocalanus minutus and Oithona similis, eggs and nauplii of copepods, as well as juveniles of pteropods were common food items for all fish. Larvae of all considered fish species in the Sea of Okhotsk fed mainly during the light hours of the day.     

Occurrence of the Chilean devil ray Mobula tarapacana (Elasmobranchii: Batoidea: Myliobatiformes) in the Sea of Okhotsk: first record from cold temperate waters

The northernmost record for Chilean devil ray Mobula tarapacana, a circumglobal species that occurs in tropical, subtropical and limited warm temperate waters, is described. An adult female was caught incidentally in the Sea of Okhotsk on 17 September 2011. This specimen is the first confirmed occurrence of devil rays Mobula spp. in cold temperate waters.     

Satellite detection of harmful algal bloom occurrences in Korean waters

Cochlodinium polykrikoides (p) is a planktonic dinoflagellate known to produce red tides responsible for massive fish kills and thereby serious economic loss in Korean coastal waters, particularly during summer and fall seasons. The present study involved analyzing chlorophyll-a (Chl-a) from SeaWiFS ocean color imagery collected over the period 1998–2002 to understand the spatial and temporal aspects of C. polykrikoides blooms that occurred in the enclosed and semi-enclosed bays of the Korean Southeast Sea. NOAA-AVHRR data were used to derive Sea Surface Temperature (SST) to elucidate physical factors affecting the spatial distribution and abundance of C. polykrikoides blooms. The time series of SeaWiFS-derived Chl-a gave an impression that recent red tide events with higher concentrations appeared to span more than 8 weeks during summer and fall seasons and were widespread in most of the Korean Southeast Sea coastal bays and neighboring oceanic waters. Coupled eutrophication and certain oceanic processes were thought to give rise to the formation of massive C. polykrikoides blooms with cell abundances ranging from 1000 to 30,000 cells ml⁻¹, causing heavy mortalities of aquaculture fish and other marine organisms in these areas. Our analysis indicated that Chl-a estimates from SeaWiFS ocean color imagery appeared to be useful in demarcating the locality, spatial extent and distribution of these blooms, but unique identification of C. polykrikoides from non-bloom and sediment dominated waters remains unsuccessful with this data alone. Thus, the classical spectral enhancement and classification techniques such as Forward Principal Component Analysis (FPCA) and Minimum Spectral Distance (MSD) to uniquely identify and better understand C. polykrikoides blooms characteristics from other optical water types were attempted on both low spatial resolution SeaWiFS ocean color imagery and high spatial resolution Landsat-7 ETM+ imagery. Application of these techniques could capture intricate and striking patterns of C. polykrikoides blooms from surrounding non-bloom and sediment dominated waters, providing improved capability of detecting, predicting and monitoring C. polykrikoides bloom in such optically complex waters. The result obtained from MSD classification showed that retrieval of C. polykrikoides bloom from the mixed phase of this bloom with turbid waters was not feasible with the SeaWiFS ocean color imagery, but feasible with Landsat-7 ETM+ imagery that provided more accurate and comparable spatial C. polykrikoides patterns consistent with in situ observations. The dense phase of the bloom estimated from these imageries occupied an area of more than 25 km² around the coastal bays and the mixed phase extended over several hundreds kilometers towards the Southeast Sea offshore due to exchange of water masses caused by coastal and oceanic processes. Sea surface temperature analyzed from AVHRR infrared data captured the northeastward flow of Tsushima Warm Current (TWC) waters that provided favorable environmental conditions for the rapid growth and subsequent southward initiation of C. polykrikoides blooms in hydrodynamically active regions in the Korean Southeast Sea offshore.     

Mass occurrence of an introduced crustacean (Caprella cf. mutica) in the south-eastern North Sea

The caprellid amphipod Caprella mutica is indigenous to coastal waters of north-east Asia and was first recorded in European waters in 1995. We now detected mass occurrences of > 3000 individuals per m² in harbours of the two islands of Sylt and Helgoland in the German Bight, North Sea. Currently, Caprella mutica seems to be restricted to artificial hard substrata but we expect it to become a new species in natural hard bottom assemblages of that region as well.     

Jellyfish of the Far Eastern Seas of Russia. 3. Biomass and abundance

The biomass and abundance of large jellyfish (Cnidaria: Scyphozoa, Hydrozoa) was estimated and their seasonal and interannual dynamics was studied based on the data of trawl surveys conducted by the Pacific Research Fisheries Center (TINRO Center) in the Sea of Okhotsk, Bering Sea, Sea of Japan, and the Northwestern Pacific Ocean (NWPO) in 1991–2009. Most of the jellyfish biomass (over 95%) in the Sea of Okhotsk, Bering Sea, and NWPO was formed by Chrysaora spp., Cyanea capillata, Aequorea spp., Phacellophora camtschatica, and Aurelia limbata. The same species along with Calycopsis nematophora predominated in abundance in the Bering Sea and NWPO, while Ptychogena lactea, C. capillata, and Chrysaora spp. were most abundant in the Sea of Okhotsk. In the northwestern Sea of Japan, Aurelia aurita, C. capillata, and Aequorea spp. predominated both in abundance and biomass. Generally, the jellyfish abundance reached the highest values in the summer and fall and decreased abruptly in the winter. Meanwhile, the seasonal dynamics proved to be specific for each species and were manifested in some of them by reaching maximum values at various periods of the warm season, whereas the other (Tima sachalinensis and P. lactea) showed the reverse pattern of seasonal variations, with the highest abundance in cold months. Jellyfish biomass and abundance varied greatly from year to year, which was related to the short lifecycle and alternation between sexual and asexual generations, in which reproductive success was predetermined by various environmental factors. In the fall, year-to-year fluctuations of the relative biomass could increase by ten times. In 1991–2009, it varied from 200 to 2000 kg/km² in the northern Sea of Okhotsk, from 500 to 4200 kg/km² in the northwestern Bering Sea, and from 300 to 3700 kg/km² in the southwestern Bering Sea. Taking the jellyfish abundance estimates into account, along with the vertical distribution and the seasonal dynamics, the overall biomass of large species that occurred in trawl catches in Far Eastern seas and adjacent Pacific waters during the warm season could reach 13.0–15.0 million tons, of which up to about 6.0 million tons would be concentrated in the western Bering Sea and 5.5–6.0 million tons in the Sea of Okhotsk.     

Genetic differentiation of Pacific cod Gadus macrocephalus in the Sea of Okhotsk and in the Bering Sea

Genetic differentiation of the Pacific cod Gadus macrocephalus was studied. Samples from six regions of the Sea of Okhotsk and the Bering Sea were analyzed with two mtDNA genetic markers-gene of cytochrome 1 and the control region (D-loop). Comparative analysis showed significant genetic differentiation between the two groups of samples. The first group included samples from Tauiskaya Bay and waters of Western Kamchatka. The second group consisted of the samples collected in the waters of the Iturup Island (Sea of Okhotsk), Northern Kurile Islands, Navarin region of the Bering Sea, and Anadyr Bay.     

Northernmost record of a whale shark Rhincodon typus from the Sea of Okhotsk

The whale shark Rhincodon typus is the world's largest fish and it occurs in tropical, subtropical and warm temperate waters. Here, the northernmost record of R. typus is reported, when it was found in the Sea of Okhotsk for the first time. This occurrence can be explained by the unusually high sea surface temperature during the summer of 2012.     

Development of tetranucleotide microsatellite loci for the finless porpoise (<Emphasis Type="Italic">Neophocaena phocaenoides</Emphasis>)

The finless porpoise, Neophocaena phocaenoides, is endemic to the coastal waters of the Indo-Pacific, ranging from the Persian Gulf to Japan. Nine tetranucleotide microsatellite loci were isolated from the finless porpoise (Neophocaena phocaenoides). Polymorphism of each locus was assessed in 39 unrelated individuals from the Yellow Sea and the South China Sea of the Chinese waters. The number of alleles per locus varied from 2 to 11. The ranges of observed and expected heterozygosity were 0.154–0.795 and 0.146–0.839, respectively. Cross-species amplification of these loci was tested in other cetacean species. These microsatellite markers described here will be suitable for population genetic studies of finless porpoises and other cetacean species.     

Population Structure of Pacific Cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis> in the Southern Part of the Range Based on the Microsatellite Analyses

The population structure of Pacific cod Gadus macrocephalus in the southern part of the range and adjacent regions is studied on the basis of the results of microsatellite analyses. Collected data indicate heterogeneity of this species population within the studied area. According to the obtained F_ST values, Pacific cod from the waters of the Republic of Korea (Yellow Sea side) and northwestern part of the Sea of Okhotsk significantly differ from all other studied regions (Table 4). Significant differentiation was also revealed between samples from the waters of the Tatar Strait and all other regions except for South Kurils Pacific cod (both Sea of Okhotsk and Pacific Ocean sides). These two latter sample collections were similar to each other as well. A low level of differentiation was also shown for the Peter the Great Bay and the East Sea/Sea of Japan waters of the Republic of Korea.     

First description of larvae of Radulinopsis derzhavini Soldatov et Lindberg, 1930 (Scorpaeniformes: Psychrolutidae) with remarks on melanin colouration and relationships with related species

The Derzhavin's sculpin (Radulinopsis derzhavini Soldatov et Lindberg, 1930) is a psychrolutids species that leads a cryptic life in coastal waters of the Japan Sea and the southern Okhotsk Sea. To date, larvae of this species have remained unknown; therefore, their biology is poorly understood. In the present study, the early developmental stages of R. derzhavini are described for the first time. In Peter the Great Bay, Japan Sea, this species is characterized by a spring spawning season (May) and a short pelagic period of larval development, usually from mid-May to the last 10 days of June. Species identification of the described larvae was confirmed by incubation, rearing of larvae in captivity, and genotyping of a fragment of the mitochondrial cytochrome c oxidase I (COI) gene. In addition, the development of pigmentation in larvae of this and related species was compared. Morphological analysis of both adults and larvae, together with complementary molecular genetics, confirms the previously obtained conclusions that the species of the genera Radulinopsis, Radulinus, Asemichthys, and Astrocottus form a natural group with monophyly by all types of data.     

The species composition and quantitative distribution of the diatom genus Pseudo-nitzschia H. Peragallo, 1990 in Russian waters of the Sea of Japan and the Sea of Okhotsk

This paper studies the species composition and quantitative distribution of diatoms that belong to the genus Pseudo-nitzschia in the Russian waters of the Sea of Japan and the Sea of Okhotsk. In total, 11 species of this genus were found in the area, including 7 that are known as being potentially toxic. The highest concentrations of Pseudo-nitzschia microalgae (1.4 × 10⁶–2.7 × 10⁶ cells/L) were found in the summer and autumn in the Peter the Great Bay of the Sea of Japan and the lowest concentrations (2.5 × 10²–1 × 10⁴ cells/L) were found in the Sakhalinsky and Akademiya bays of the Sea of Okhotsk. The species diversity of potentially toxic diatoms was greatest (seven species) and the cell concentrations highest (over 6 × 10⁵ cells/L) in the Peter the Great Bay, Sea of Japan, and in the Aniva Bay, Sea of Okhotsk. The density of potentially toxic species was highest near the northeastern coast of Sakhalin Island, in the Amur River estuary, and in adjacent waters. This paper also presents geographical distribution maps of Pseudo-nitzschia species and maps of the density distribution of potentially toxic microalgae over the studied area and identifies potential amnesic shellfish poisoning areas.     

Population Dynamics of the Pink Salmon Oncorhynchus gorbuschain the Basin of the Sea of Okhotsk in the 1990s

In the 1990s, an extensive body of data was gathered on the size of the Oncorhynchus gorbuschapink salmon populations of the Sea of Okhotsk at all the main developmental stages. A significant increase in numbers was found for juvenile pink salmon migrating into the offshore regions of the Sea of Okhotsk and the Pacific waters around the Kurils: from 250–450 million in 1990–1991 to 807–1570 million fish in 1993–1999. The overall number of migrating pink salmon in even years sharply increased in 1994 up to 215 million fish. After 1994, this estimate exceeded the number of migrating pink salmon in preceding odd years. Ocean survival of juvenile pink salmon gradually declined. This may be related to changes in the North Pacific pelagic ecosystems.     

The formation of the Lycodinae fauna (Perciformes: Zoarcidae) of the Sea of Japan

The subfamily Lycodinae is represented in the Sea of Japan by two genera (Lycodes and Petroschmidtia) and seven species (Lycodes japonicus, L. nakamurae, L. raridens, L. tanakae, L. teraoi, L. yamatoi, and Petroschmidtia toyamensis), which are widely distributed on the shelf and upper continental slope. Based on the geographic and bathymetric distribution of eelpouts of the Sea of Japan and adjacent waters, two groups of closely related species with different types of distribution ranges were distinguished. The first group includes pairs of species that live primarily on the continental slope and are completely isolated in the Sea of Japan or in the Sea of Okhotsk. The second group is comprised of upper interzonal species of the Sea of Japan that are found on the continental slope and shelf, as well as in the southern Sea of Okhotsk from Terpeniya Bay to the southern Kuril Islands. Their related species in the Sea of Okhotsk are mostly found to the north of the Terpeniya Bay. The study of the eelpout distribution and the data on the geological history and paleoclimate of the Far East show that the Lycodinae fauna of the Sea of Japan was formed from North Pacific eelpout-like fishes during the isolation of the sea in the late Pliocene-early Pleistocene, which was concomitant with the general cooling of the Earth’s climate. During the Pleistocene interglacials, the eelpout migrations were unidirectional, from the Sea of Japan to the southern Sea of Okhotsk. The reconstruction of the formation of the Sea of Japan Lycodinae fauna suggests that the related taxa from the Sea of Japan and the Sea of Okhotsk are separate species, while the northern and southern forms of species from the Sea of Japan (Lycodes yamatoi and L. teraoi) are no more than subspecies.