Comparative study of growth rate and size-age structure of gray sea urchin Strongylocentrotus intermedius is conducted for six its aggregations along Primorye coast on the data collected in diving surveys in 2015–2017. Some aspects of the method of the sea urchin individual age determination by concentric growth bands on interambulacral plates of its carapace are discussed (the plates are processed by M. Jensen method). The group growth is described with Bertalanffy equation. Considerable spatial variability of the growth rate is found between the aggregations that provides some distinctions in size structure of the sea urchins. The highest growth rate is observed for three habitats: Kreyser Rock Island — Cape Lisuchenko, Oprichnik Bay — Cape Grozny, and Cape Sosunov — Plitnyak Bay, where the sea urchins reach the commercial size mostly at the age from 3.5+ to 4.5+. On the contrary, 50 % of the sea urchins become large enough for commercial fishery at the age of 6+ in the Ezhovaya Bay, and the lowest growth rates are noted at Cape Yuzhny and Cape Nadezhda where the majority of sea urchins never reach the commercial size. The maximum age of S. intermedius (19 years) is registered for a specimen with size 73 mm caught at Cape Sosunov. Mean and maximum sizes of individuals in the aggregations of slow-growing S. intermedius are lower than in the aggregations with comparatively high growth rates; such aggregations are also distinguished by lack of commercially-sized individuals. Age structure of all aggregations shows strong irregularity of annual recruitment, particularly low portion of the sea urchins at the age of 1+ is noted. Anyway, the frequency goes down from the age of 7+...9+ that indicates mass elimination of elder animals.

Size composition of common whelk Buccinum undatum in its aggregations on sandy and stony grounds at the depth of 2–15 m is analyzed on the data of experimental fishing by scuba divers and traps in the Kislaya Guba and Ura Guba Bays in different seasons of 2004–2017. The size group with shell height > 60 mm was the most abundant (70 %) and formed 90 % of the total biomass. This group is recommended for fishery; the shell height of 60 mm is sug­gested as the minimal commercial size for common whelk in this area.

Current state of zoobenthos in the areas of scallop Chlamys islandica beds in the southern Barents Sea and eastern White Sea (Voronka) is described. The scallop stock is ex­ploited there with the landing by specialized vessels, without separation of catch, so bycatch of other species is considerable. As the result, significant changes occurred in structure of benthic communities during the times of scallop fishery. To assess the fishery effect, species composition of benthos, its dominant species and trophic structure is considered separately for 4 regions with different degree of exploitation. Dynamics of zoobenthos abundance is traced over the last 25 years. Changes in trophic structure of the benthic community at Cape Svyatoy Nos (southern Barents Sea) are analyzed in details. Although up to ¼ of its total biomass is presented by carnivorous species and the biomass of C. islandica has decreased, the portion of sestonophages has increased in this community. Recently a recovery of zoob­enthos is observed in its southern part, supposedly because of the animals redistribution from adjacent areas unaffected by fishery. On the contrary, extremely low biomass of zoobenthos, in particular scallop, is observed in the northern part of the community. Biomass of benthos in the Voronka area is high, but it is formed mainly by mussels. There is concluded that more than a decade is required for full recovery of the scallop stock and accompanying zoobenthos communities to the native state.

The main stages of embryonic and early post-embryonic development of bering flounder in the northern shelf areas of the Okhotsk Sea are described for the first time, their timing is determined and the heat amounts necessary to achieve the stages are evaluated on the base of experimental data. The developing eggs had an average diameter of 2.33 ± 0.01 mm and volume — 5.66 ± 0.05 mm3. The yolk occupied 19.36–31.15 % (on average 24.40 %) of the egg volume that corresponded with the polyplasmatic type of eggs. Time of the eggs incuba­tion from the beginning of epiboly to hatching of prelarvae was 238 hours in the experiment under temperature 8.1 oC. The total time of embryogenesis was estimated as 276 h, and the heat amount required for the total embryogenesis — as 2236 degree-hours. At the stage of the blastula cells gastrulation, the process of axial convergence of the blastoderm directed to forming of an axial bud in the embryo. The Kupfer vesicle was developed and the body pigmentation appeared before closing of the blastopore, but segmentation of the body started after the closing. The muscle activity was detected only with start of the heart working, in opposite to other studied flounders which muscles became active earlier. The newly hatched prelarvae had the body length 4.85–6.00 mm, on average 5.44 ± 0.06 mm. Their transition to mixed and exogenous nutrition occurred at the age of 2 and 3 days, respectively, when their average size was 5.75 ± 0.17 and 5.83 ± 0.17 mm. Following to the experimental and cited data, morphology of prelarvae and larvae of bering flounder is distinguished by weak development of black melanophore on the dorsal side and its absence on the fin fold, as well as relatively early pigmentation of eyes with guanophore.

Reasons for rapid rise of pink salmon landings in the Sakhalin Bay (Okhotsk Sea) in the early 21 century are analyzed. Dependence of its juveniles and adults numbers on the number of their parents is well described with Ricker equation, and the recruitment depends linearly on the number of juveniles in the river. Several factors of the pink salmon reproduction are compared between the early 21 century and previous period. There is found that recent in­crease of the catches could not be reasoned by favorable changes of environments, decreasing of juveniles mortality either in the river or in the sea, extending of spawning grounds, growth of spawning stock or number of juveniles. The only possible reason for significant rise of the landings could be an increasing by-catch of transitory stocks.

Description of frill shark Chlamydoselachus anguineus (TL 134.3 cm) is presented that was caught in the pelagic layer of the North-West Pacific in June 1979, including surface morphometric parameters and data on number of vertebras, teeth rows, and intestinal valve coils.  

Oceanographic and chemical properties, sea currents, bottom topography and sediments in the Severnaya Bight (Slavianka Bay of Peter the Great Bay, Japan Sea) are considered on the base of all available data collected from 1965 to 2018. Mean and extreme values of the water parameters in the bight are determined for the first time. Seasonal and short-term tide-induced variations of the water temperature and salinity at certain depths are described. The environments influence on aquaculture is estimated. The hanging culture equipment can be mounted in the bight at the depth of no less than 10–12 m, whereas the bottom culture is possible in local areas with the depth of 6–10 m located in its northern and northwestern parts and southwestward from the Mininosok Inlet. In the north of the bight, the cultivated scallop is subjected to unfavorable influence of high water temperature and low salinity, but the water regime at the depth of 6–8 m, where the collectors and hatcheries are usually mounted, is relatively stable and favorable for the scallop cultivation, with rather rare and short-term rises of temperature (up to 25 °С), declines of salinity (to 24 ‰), and dissolved oxygen depletion (to 3.17 mL/L, or 58 %). Currents in the Severnaya Bight are strong enough for its waters renewal: 25–30 cm/s. The currents are almost reverse in the top of the bight; the semi-permanent cyclonic circulation develops in its main part that provides the water exchange with the open part of Peter the Great Bay and distribution of suspended solids, contaminants, bacteria, or larvae from marine farms or other sources over the bight. The non-tidal currents are almost twice stronger in winter than in summer.

Chemical parameters (dissolved oxygen content, concentrations of silicon, phosphate and nitrate, nitrate deficiency) in the TINRO Basin of the Okhotsk Sea (~1000 m depth) are considered for the years 2001–2002 with abnormally cold winters. The Basin water exchange with the southern Okhotsk Sea is limited by the threshold with 500 m depth. The warm Inter­mediate water penetrates to the Basin above the threshold only. The warm intermediate layer is rather thin (σθ = 26.88–26.92 or 400–500 m depth) in the years with abnormally cold winter. It is distinguished by high concentrations of nutrients and low oxygen content; moreover, their values are the highest/lowest for the entire Okhotsk Sea, presumably because of partial isolation of its water in the basin where it is captured by the water gyre and «aged» with biogeochemical processes. The deep waters of the TINRO Basin (σθ ~27.02) are formed by mixing of three components: intermediate Okhotsk Sea waters, waters of the temperature maximum layer and dense cold waters of the Shelikhov Bay. The portion of the latter water mass is evaluated as 37 %. It enriches the Deep water in the Basin with dissolved oxygen and provides relatively low concentrations of nutrients. The peculiarity of the TINRO Basin manifests in the fact that these processes in the deep-sea zone (800–1000 m) proceed with high velocities typical for shelf. In addition, in the deep waters of the Basin, there is a significant deficit of nitrate, presumably due to denitrification, which also proceeds with high rate. This suggests that non-conservative behavior of hydrochemical characteristics in the deep waters is caused by processes occurring on the surface of bottom sediments. The main reason for this behavior is probably an additional accumulation of biogenic material at the bottom of the TINRO Basin as the result of its trans­fer from shelf by the cold dense waters ventilating the Basin. The TINRO Basin, being a trap for the cold dense shelf waters, apparently is a convenient object for observing and analyzing climate change in the northeastern Okhotsk Sea.  

Resident morph of threespine stickleback Gasterosteus aculeatus is an important competitor for food for sockeye salmon juveniles in their freshwater period of life. The most intense feeding interactions occur in the pelagic zone of lakes between sockeye salmon underyearlings and yearlings of resident threespine stickleback. To evaluate this factor, the size and feeding were monitored for the resident yearlings of threespine stickleback (leiurus morph) in the littoral zone of Lake Azabachye annually on July 1 (±1 day) since 1985 (in late July — early August these yearlings migrate in mass to the pelagic zone of the lake). The mean body length varied from year to year between 29.02 ± 0.19 — 40.52 ± 0.33 mm, with some periodicity of 8–9 — 12 years presumably caused by environmental changes. Their main prey was chironomids, with average percentage in the food bolus 44.3 % (from 3.3 % in 2011 to 79.2 % in 2008). The mean stomach fullness of leiurus at the age 1+ varied by years in the range 27.8–254.5 ‱ and correlated significantly with year-to-year changes of the water temperature in the lake; the specimens with empty stomach were absent and the highest individual index reached 527.9 ‱. The consumption was the highest in 2011 and 2017 (mean indices of stomach fullness 215.7 and 254.5‱, respectively). Sockeye under­yearlings were almost absent in the littoral zone in the period from late June to middle July.  

Data on abundance and biomass of mass arrowworm Sagitta elegans in the Okhotsk Sea are presented, by size classes, on the base of plankton surveys conducted by Pacific Fish. Res. Center (TINRO) in 1984–2017. S. elegans spawns throughout the year, with varying intensity by areas. The juveniles with the length < 6 mm are observed in mass along the eastern boundary of the sea in winter and spring, and in its entire periphery in summer. The mean annual portions of the size classes by abundance/biomass are: < 6 mm — 13.9/0.3 %; 6–10 mm — 10.0/1.9 %; 10–15 mm — 8.1/3.3 %; and 15–25 mm – 58.0/70.0 %. In the epipelagic layer 0–200 m, the total number of S. elegans depends negatively on the bathymetry: its mean abundance/biomass decreases from 71 ind./m3 and 942 mg/m3 in the zone with depth 30–50 m to 8 ind./m3 and 159 mg/m3 in the deep-water zone; the decreasing is more prominent for small-sized classes, and is not observed for the class > 25 mm. However, no more than 20 % of the species biomass is presented in the epipelagic layer, but the main part is concentrated in the layer 200–1000 m. S. elegans consumes the prey with the size equal to width of its mouth, mostly copepodites on differ­ent stages of development — their size correspondence to the size classes of arrowworms is presented, as well as the mean annual spatial distribution of small-, medium-, and large-sized copepods. Generally, the prey for the arrowworms with length < 25 mm (eggs, nauplii, smalland medium-sized copepods) is more abundant on the shelves, whereas the prey for the biggest arrowworms (large-sized copepods with length up to 5 mm) are concentrated in the deep sea.

Results of parasitological studies of rainbow smelt Osmerus mordax dentex Steindachner et Kner, 1870 at the northern coast of the Okhotsk Sea are presented. Its helminth fauna includes 21 species: Cestoda — 8, Trematoda — 7, Nematoda — 4, and Acanthocephala — 2. Almost all these species (19) were detected in the Shelikhov Bay, with the highest species diversity among 4 investigated sites in the secondary Perevolochny Bay (14 species). Six species of helminthes from the smelt dwelling in the northern Okhotsk Sea are known as dangerous for human or other mammals: Nybelinia surmenicola, Diphyllobothrium dendriticum, Hysterothy­lacium aduncum, Anisakis simplex, Pseudoterranova decipiens, and Corynosoma strumosum. The species diversity of helminthes at the northern coast is comparable with the number of species at the coasts of Kamchatka (16 species: Cestoda — 4, Trematoda — 5, Nematoda — 4, Acanthocephala — 3) and Sakhalin (19 species: Cestoda — 5, Trematoda — 8, Nematoda — 3, Acanthocephala — 3); totally 33 species of helminthes are detected in these three areas. The cestodes Diplocotile olrikii, Bothriocephalus spp., trematodes Bucephaloides iskaensis, Po­docotyle atomom, and P. reflexa and nematodes Ascorophis pacificus infect rainbow smelt at the northern coast of the Okhotsk Sea only. The most epidemically significant species Anisakis simplex is widely distributed in all three areas.

Data on feeding of underyearlings of arctic cod Boreogadus saida, pacific cod Gadus mac­rocephalus, saffron cod Eleginus gracilis, sand lance Ammodytes hexapterus, capelin Mallotus villosus, and other fish species were collected in the Chukchi Sea in August-September, 2017 in the framework of Arctic Integrated Ecosystem Survey (Arctic IES). In the time of survey, the eastern Chukchi Sea was free of the sea ice to 72о30′ N. Large aggregations of arctic cod were observed in the surveyed area. The diet of arctic cod juveniles and youngsters of other investi­gated species included both pelagic and near-bottom zooplankton, mainly copepods, euphausiids, oikoplevres, and juvenile decapods. The copepods Calanus glacialis and Calanus. hyperboreus dominated in the northern part of the surveyed area, being typical for the Arctic Ocean and Beau­fort Sea, and the species usual for the Bering Sea, as the copepods Calanus glacialis + Calanus marshallae, Eucalanus bungii, and Neocalanus cristatus, were in predominance in its southern part. Besides of these large-sized species, the species typical for the Alaska coastal waters were presented in the diet of juveniles, as the copepods Pseudocalanus spp., Centropages abdominalis, Acartia longiremis, Podon sp., Tortanus discaudatus, Epilabidocera amphitrites, and Eurytemora herdmani, as well as larvae of Polychaeta, Echinodermata, Cirripedia and veligers of Bivalvia. The arctic cod juveniles used the whole spectrum of prey but consumed mainly smalland medium-sized zooplankton, which biomass was relatively low in 2017: 21.8–243.5 mg/m3 in the southern part of the surveyed area and 5.1–83.0 mg/m3 in its northern part. Correspondingly, their feeding intensity was higher in the south: their stomach fullness was 98.7–67.5 ‱ in the south and 76.9–46.9 ‱ in the north; the mean daily ration was 4.2 % of the body weight in the south and 3.4 % in the north. These values are considered as low or medium, possibly the stock of arctic cod was too high for the feeding base, particularly in the northern area. From the other hand, the diets of arctic cod, saffron cod and sand lance were very similar in the areas of joint habitation, so competitive relations between these species could be assumed.

Zooplankton in the eastern Chukchi Sea is described on the data of summer observa­tions in 2017. The northern part of the surveyed area was occupied by the cold water masses from the Arctic Ocean and Beaufort Sea. Large-sized zooplankton dominated here, including copepods Calanus glacialis, C. hyperboreus (this species is an indicator of Atlantic waters) and cold-water hyperiids Themisto libellula. In the southern part of the surveyed area, small-sized zooplankton dominated by biomass and abundance and species belonged to the Bering Sea community, as copepods Calanus glacialis + Calanus marshallae, Eucalanus bungii, and Metridia pacifica, were presented in the large-sized fraction. In the western part of the sur­veyed area and in the coastal waters, small-sized copepods Pseudocalanus spp. and Oithona similis prevailed, and biomass and abundance of neritic species as Centropages abdominalis and Acartia longiremis were high, too. Besides, some species typical for desalinated water were observed here (Eurytemora herdmani, Podon sp., and Epilabidocera amphitrites), as well as larval forms of benthic invertebrates (larvae of polychaetes, bivalves, gastropods, and echinoderms). Arrowworms Sagitta elegans were abundant everywhere that was caused by this species reproduction. The observed structure of plankton community corresponded to feeding demands of arctic cod juveniles, but the zooplankton biomass was rather low. These features of community could be interpreted as early summer state, when its biomass does not reach the maximum yet, as it was observed, for example, in September 2007.

Qualitative and quantitative composition of phytoplankton in the Golden Horn Bay (Japan Sea) was investigated in the period from October 2009 to October 2010. The water samples of 1 L volume were taken with Molchanov bottle at the 36th Berth where ship-repairing yards were located and naval and commercial ships were moored. The samples were fixed in Utermӧhl iodine solution and phytoplankton cells were concentrated by precipitation or by reverse fil­tration, then the concentrated samples were processed under microscope. In total, 135 species and intraspecific taxa of microalgae were detected, which belonged to 7 divisions. Average density of phytoplankton cells varied from 1.9 . 103 to 610.3 . 103 cells/L, its average biomass varied from 0.02 to 11.70 g/m3. Four peaks of the phytoplankton cells density were registered: in summer, spring, winter and fall (in descending order), with the highest density in June, but only one peak of the phytoplankton biomass was observed in February. The highest density (up to 1 . 106 cells/L) was formed by euglenophytes that was similar to the neighboring Amur Bay and obviously indicated organic pollution of the Golden Horn Bay waters. Comparing with results of previous observations in the 1990s and 2000s, the species diversity of dominant diatoms and euglenophytes has increased recently. These species are known as indicators of eutrophic waters and/or organic pollution.  

Abundance, size composition, and terms of plankton stage were investigated for the larvae of pacific mussel in the Veselaya Bay (Okhotsk Sea) in two years with different oceanographic regime. The first larvae (density 8-30 ind./m³, shell length 75–150 μm) appeared in late June in the year with relatively high water temperature (2016) and in early July in the year with lowered temperature (2011), then their number had increased to 1750 ind./m³ in early August of 2016 and to 1320 ind./m³ in late August of 2011. Density and size composition of the spat and young mussels were examined in hanging collectors and nurseries. The growth rate change in dependence on shell length was noted. There is concluded that the hanging collectors are more effective for spat collection, while the nurseries are better for growing of littoral mussels.  

Natural populations of crayfish are in depression in Russia and local species are not cultivated. In this situation, experimental cultivation of allochtonous australian crayfish Cherax quadricarinatus is conducted. This species is distinguished by high reproductive abilities and good consumer properties. It has domesticated in Russia spontaneously and produced 9–10 generations in Astrakhan Region. Certain natural selection in the process of domestication provides adaptive ability of this species to local environments and its capabil­ity to reproduce a viable progeny, so there is no doubts in good prospects of its cultivation in industrial conditions.

Physical and chemical processes in muscular tissue of pond fish are considered in the process of storage. The muscle contraction appears mainly because of the myofibrils activity that utilizes energy of the sarcoplasm substances. Intense disintegration of glycogen causes sharp acidification (pH decreasing) in the muscular tissue that affects on chemical composition and physical-colloidal structure of proteins. Hardening of the muscular tissue is observed in the first hours of storage because of the proteins transformation to actin and myosin in insoluble actomyosin complex. The highest level of actomyosin is observed in the first 3–5 hours that is the evidence of unstable rate of biochemical processes corresponded to changing activity of enzyme systems. Cumulative level of the actomyosin complex grows in the first 8 hours of storage for all investigated fish species. Organoleptic and technological characteristics of the fish meat improve significantly in the process of its maturation: the meat has no definite taste and smell in early stages of autolysis, but these properties appear in 3–4 days, depending on the storage temperature, due to enzymatic decomposition of proteins, peptides, nucleotides, carbohydrates, lipids, etc. Recommendations on storage are presented for certain groups of fish products in dependence on initial properties of raw materials.

Marine biological resources are usually assessed by trawl surveys; methods of these surveys are well-developed. However, number of fish populations is too high to be completely assessed by scientific surveys, so the data of commercial fishery have to be used, too. Danish seine is preferable method of the Russian commercial fishery in the Japan Sea and some other areas of the Russian EEZ. Principal possibility of fish stocks accounting with Danish seine is tested earlier by specialists of Kamchatka Research Institute of Fisheries and Oceanography for the West Kamchatka where the parallel surveys by trawl and Danish seine were compared that showed similar results. Continuing these experiments, the data of Danish seine catches in Peter the Great Bay are compared with the data of trawl catches in the same area. In spite of differences in construction of the Danish seine and trawl, the fish resources assessments by these gears are similar in this area, too. Some differences are associated with the three times thicker layer caught by the Danish seine. Because of this reason, yellowfin sole Limanda aspera prevailed in the catches of Danish seine but other Pleuronectidae plaices were more numerous in the trawl catches, obviously because of their aggregation closer to  the bottom.

New methodological approach to express assessment of ecological state in the coastal areas of the Black Sea is proposed on the base of functional state evaluation for mussel Mytilus galloprovincialis. Non-invasive cardiac activity of mussels under a short-term functional loading (salinity change) was monitored in four differently polluted sites at Sevastopol city to detect early signs of their physiological state deterioration. As the control, the biochemical method of antioxidative stress (AOS) assessment was applied that is widely implicated in bioindication of marine environments. The sites in the Yuzhnaya/South Bay were defined as the most contami­nated ones where the mussels demonstrated a prolonged recovery of the heart rate (76.8 min) and high variation of the heart rate after loading (24 %), while the mussels from the Kazachya Bay had rapid recovery (35.3 min) and lower variation of the heart rate (9 %) after removal of the stress load. The biochemical assessment showed the same results. The poor ecological state of the South Bay is obviously caused by heightened concentrations of heavy metals, as Pb, Sn, and Cu, detected in the hepatopancreas of tested mussels. The levels of antioxidative system parameters (e.g. glutathione peroxidase, catalase, and superoxide dismutase activity) correlated significantly with Pb content in the hepatopancreas (R2 = 0.89–0.92) and were heightened, as well. Prospects of the proposed biomarkers application in biomonitoring and their relevance for the risk assessment in aquatic ecosystems are discussed.  

New method for long-term forecasting of mean month and mean 10-days values of the ice cover and position of the ice edge in the Far-Eastern Seas is presented. The sea ice regime is formed under influence of thermal and dynamic patterns in the atmosphere and hydrosphere, though mechanisms of its forming and evolution are not yet completely clear, so the sea ice forecasting is based mainly on statistical methods. The new method is developed for the ice parameters prediction for the period with stable ice cover. It uses a physical-statistical model with ensemble approach. The minimum lead time of this method is 7 months. The model assimilates the data on absolute topography of 500 GPa surface, atmospheric pressure at the sea level, air temperature at 850 GPa surface and at the sea surface, relative topography of 500/1000 GPa surfaces, and the South Oscillation index. Archives of these fields for the Northern Hemisphere from 1961 to 2017 are loaded. The ensemble of predictions is formed using the criterion of their maximum accuracy on independent data sets. The method is tested for the winter seasons of 2015/2016 and 2016/2017. The most accurate by 3 parameters are the forecasts for the Okhotsk Sea with the average accuracy 75–83 % that is much better than the accuracy of climatic forecasts (61–67 %). The forecast of the mean month ice cover only is satisfactory for the Japan Sea, and the forecast of the ice edge position only (65 % accuracy) exceeds the climate forecasting accuracy for the Bering Sea, while the climatic forecasting shows better results for the ice cover. The average accuracy of forecasting with new method (all parameters for all seas) exceeds 70 %, that allows to recommend the method for practical using. A prognostic product could be proposed as charts of the sea ice edge for future winter with estimations of the ice cover for each sea by months and 10-days.