In this work, based on the data on the sea surface temperature, deep-sea oceanographic observations, we studied the thermohaline and dynamic conditions of the Southern Primorye and open waters of the northwestern part of the Sea of Japan in the spring and summer of 2018. 'The features of the oceanological structure were revealed, and state and water conditions were estimated. Anticyclonic eddies were observed in the open waters of the northwestern part of the Sea of Japan. In the water circulation, its main components are shown, the roles of the Primorsky and West Sakhalin currents are highlighted. The concept of the structure and nature of the Primorsky Current has been expanded. It is shown that in the vertical structure of the waters of Peter the Great Bay (April) and the western part of the Tatar Strait (June) there existed the near-bottom and subsurface cold layers. In the waters of southern Primorye in May, these layers were not observed. Based on the meridional displacement of the vortex structures and the criterion for assessing the thermal regime of the waters of the northwestern part of the Sea of Japan - the average temperature of the subsurface layer 50-200 m - it was established that in the year under study the thermal regime of the sea was classified as warm.

Based on the analysis of changes in the spatial structure of climatic variations in the Northern Hemisphere before and after the climatic regime shift in the 1980s, the modes of interaction between climatic processes in the North Atlantic and North Pacific have been identified. 'The first (“western”) mode prevailed until the late 1980s, reflected the impact of the North Pacific climatic processes on the North Atlantic climate as a result of interaction of two mutually independent Pacific teleconnection patterns (Pacific/North American and Tropical/Northern Hemisphere patterns) with the West Atlantic pattern. The pronounced eastward shift of the North Atlantic Oscillation (NAO) centers from the late 1970s resulted in establishment of the “eastern” mode of interaction between the aquatories under consideration. The climatic changes originated in the North Atlantic basin propagated in the western half of the North Pacific via the system of atmospheric teleconnection patterns over Eurasia (“atmospheric bridge”). The establishment of the “eastern” mode became obviously one of the reasons of sharp warming of surface waters in the western and central areas of the North Pacific from the end of the 1980s, which favored the beginning of a new “salmon epoch” in its northwestern part. Along with the synchronous relationships between the Eurasian atmospheric modes and North Pacific sea surface temperature anomalies, an asynchronous response in the ocean to longitudinal shifts in position of the NAO centers, was found. The atmospheric signal associated with its southern center propagated eastward along the equatorial zone and appeared in the southwestern sector of the North Pacific 5-6 years later.

Formation of the surface structure mechanism of the South Kuril waters in the last two years has undergone significant changes. Therefore, the “cold” type of hydrological conditions prevailed in the South Kuril area during August-November 2017. The surface water temperature was below the norm by 1-2 °C. On the contrary, the “warm” type of hydrological conditions prevailed in the South Kuril area during August-November 2018 and the water temperature in the area under consideration was 1-3 °C higher than the average for many years. Saury fishing in 2018, as in 2017, began in the second decade of August on the peripheral fronts of the Ask eddy and continued here until the second decade of September. At the end of September, the fishing area formed in the southwestern part of the EEZ of the Russian Federation and, unlike last year, it remained until the beginning of the third decade of October. The “warm” type of hydrological conditions causes this duration of the fishery. Saury moved outside the EEZ in late October. Fishing for sardines and mackerel began in mid-July 2018 and was carried out on the northern periphery of the eddy A. However, at the end of October, unlike in 2017, fishing here practically stopped due to a decrease in the temperature drops at the peripheral fronts of the eddy caused by the high temperature of the surface waters of the Oyasio current. In late October - the first half of November in 2018, mackerel and sardine fished in high-gradient areas of the Northern Subarctic Front (NSAF) close to the eastern and southern borders of the Russian EEZ. During fishing season 2018, in contrast to the previous year, schools of sardines and mackerel remained much longer in the economic zone of Russia.

Hydrometeorological situations during the fish kill events that took place in the Belosaray, Obitochny and Kazantip Bays in the summer seasons of 2010-2018 have been analyzed. Average monthly background water and air temperatures and wind velocity are considered, as well as their average daily values before, during and after a fish kill event. It is shown that background characteristics of water temperature and wind velocity influenced the development of a fish kill event more directly and definitely than air temperature, which influence was only indirect. In the majority of cases, hydrometeorological situation, leading to fish kill event, developed according to the typical pattern with increasing air and water temperature and decreasing wind activity. In the northern bays, the Belosaray and Obitochny Bays, fish kill events were recorded during the first half of summer season, and in the southern bay, the Kazantip Bay, they occurred in the second half of it. Since 2012, due to significant decrease in vertical thermohaline stability and increase in water homogeneity, no significant fish kill events were recorded under various temperature and wind conditions. Satellite imaging of sea surface temperature confirmed typical course of fish kill event development: the temperature increased in the pre-event period and then, after the event, stayed high in the southern bays and decreased in the northern ones.

The features of the interannual dynamics of the surface water temperature in the Central part of the Baltic Sea and in the Gulf of Finland over the past 70 years were analyzed. The total effect of the linear trend and the long-period component on the dispersion of the initial water temperature values in the Central part of the Baltic Sea was 48.4%, and in the Gulf of Finland was 67.0%. These two components in 1949-2018 determined the duration of two climatic phases: moderate (1949-1987) with a heat content close to normal and warm (1988-2018). The average rate of temperature increase in the last 31-year period (1988-2018) in the Central part of the Baltic Sea was 0.42 °C per 10 years, while in the Gulf of Finland it was 1.5 times higher. The beginning of the modern period of warming of water masses coincided with the weakening of the meridional type of atmospheric circulation in the North Atlantic and the strengthening of air transport from its water area in the Eastern direction. The increase of water temperature may be one of the reasons for the redistribution of commercial concentrations of herring and sprat in the Baltic Sea, thereby the change in their annual catch in certain ICES sub-divisions of the Central part of the Baltic Sea and the Gulf of Finland was observed.

Aiming to develop the biological resources of the Okhotsk Sea shelf zone, a remote study of regional features of the ice processes dynamics in fishing areas is important. One of the main fishing areas of the Okhotsk Sea is the West Kamchatka subzone - the northeastern sector of the water area to the east of 153°30' E, bounded from the south by latitude 54° N. Dynamics of seasonal changes in ice cover is inherent in every region of the sea, regardless of the total area of ice. Geophysical processes affect the ice cover through a complicated mediated correlation that includes changes of the atmospheric circulation parameters. Critical, anomalous states of the ice cover in the West Kamchatka fishing subzone and also the cause-effect relations of its formation are revealed during the pollock seasons in 2006-2017. The mechanism of influence of thermobaric conditions, confirming the influence of the Okhotsk tropospheric cyclone (OTC) and the Pacific tropospheric crest on the formation of abnormal ice conditions in the Okhotsk Sea both in general and in certain local areas is presented.

Recent changes in reproduction are considered for two populations of walleye pollock which spawn in the Japan Sea at the coasts of Primorye and Hokkaido. Interannual dynamics of reproduction for both populations corresponds to the stock-recruitment dependence described by Ricker curve that determines the maximum recruitment with an optimal value of stock equal to the carrying capacity of the biotope for the species and the lower recruitment if the stock is either lower or higher than this optimal value. However, instability of the Ricker curve parameters is noted, and their recent changes were unfavorable for reproduction of both populations and caused decreasing of their stocks, with sharp decline in the early 1990s. Basing on authors results and cited data, climate change in the Japan Sea region is determined as the reason of this decreasing, in particular weakening of winter monsoon. In spite of a common nature, mechanisms of the climate change influence on two studied populations are completely different: reproduction of the Hokkaido population worsened because of increasing transfer of its eggs and larvae out of the Japan Sea in conditions of the strengthening Tsushima Current, that was explained in the terms of Ricker curve as decreasing of population fecundity, but reproduction of the Primorye population worsened because of unfavorable for pollock reconstructions in the local ecosystem located in the south periphery of the Subarctic zone in conditions of increasing water temperature that was explained in the terms of Ricker curve as shrinkage of carrying capacity for pollock (from approximately 150 -103 t to almost zero level). Note that the carrying capacity did not shrink but slightly extended (to 500 -103 t) for the Hokkaido population located in the north periphery of the Subtropic zone. Features of climate warming influence onto subarctic and subtropic ecosystems are discussed.

This paper discusses our research on the interannual variability in the Barents Sea thermal frontal zones. The length index of the thermal frontal zones (the number of grid nodes with a relevant temperature gradient) and their mean temperature gradients at 50 m depth in August-September 1960-2018 were calculated for an area between 73-78°N, 15-43°E, where the frontal zones are more evident. Thermal frontal zones were identified in the areas where temperature gradients exceeded 0.04 °C/km. Since the beginning of this century, the length index of thermal frontal zones in the Barents Sea has been decreasing and temperature gradients in them have been weakening; in 2010, the length index of frontal zones and the mean temperature gradient reached record low values since 1960. To estimate interannual variability in the positions of thermal frontal zones, their geographical centroids (weighted centers of mass for grid nodes with a relevant temperature gradient) were calculated, taking into account horizontal temperature gradients as weighting coefficients. From the 1960s to the 2010s, the decadal mean centroids of frontal zones shifted northeastwards by 150 km.

Based on the results of sea expeditions, interannual changes in structure of the ichthyocenosis in the pelagic zone of the southern shelf of Morocco in the Atlantic Ocean were studied in connection with changes in the habitat. Mass pelagic fish were selected as reference biological species: European and West African horse mackerel, European sardine, Eastern mackerel, sea bream, sea snipe, myctophids, as well as non-commercial fish species. Field data were obtained during the implementation of complex oceanographic surveys in the fall seasons (October-November) 2015-2018. The results of control trawls were used, in which any species amounted to at least 70% of the catch. The analysis of the species composition of the control trawls, data of hydroacoustic tracking of trawls, thermohaline water characteristics is carried out. Data pairing was carried out by phased extraction and transformation using standard computer programs for processing various types of data (acoustic, hydrological, ichthyological), as well as specially designed programs that allow you to create a single database. It has been established that recent changes in the number of commercial and by-catch species observed in the ARZ of Morocco in recent years are associated with the presence or absence of so-called “settlement windows”, which appear in the T, S-diagram field by regions of different configurations, which indicates changes in the ratios of water masses. Based on the identified relationships between changes in the ratio of water masses and changes in the species composition of the control trawls of accounting replenishment surveys, estimates of the expected changes in the biomass of mass pelagic fish in the coming years are made.

Analysis of the long-period changes of the surface thermal characteristics in the Japan Sea, including the ice cover of Peter the Great Bay, was carried on the basis of the regional databases formed from open sources. 'The relationship of the observed changes with large-scale processes characterized by well-known climatic indices was investigated. It was revealed that surface temperature changes in the Japan Sea, its Northern part and in Peter the Great Bay in winter and summer occur synchronously. In the new century (2001-2017), the growth rate of the sea surface temperature slowed down in comparison with the last 25 years of the 20th century. The most influential in these areas were the large-scale processes, which are characterized by the index of the Siberian anticyclone and the West Pacific index. We also analyzed the sustainability of the statistical relationships between regional thermal characteristics and large-scale climate indices. Special attention was paid to the change in the character of the relationships at different time periods. The pronounced rearrangements of the linkages accompanied by a change in the sign of the correlation coefficients corresponded to the well known climatic regime shifts in most of the cases under study. The most notable restructuring occurred in 1988/89.

Formation of the surface structure mechanism of the South Kuril waters in the last two years has undergone significant changes. Therefore, the “cold” type of hydrological conditions prevailed in the South Kuril area during August-November 2017. The surface water temperature was below the norm by 1-2 °C. On the contrary, the “warm” type of hydrological conditions prevailed in the South Kuril area during August-November 2018 and the water temperature in the area under consideration was 1-3 °C higher than the average for many years. Saury fishing in 2018, as in 2017, began in the second decade of August on the peripheral fronts of the Ask eddy and continued here until the second decade of September. At the end of September, the fishing area formed in the southwestern part of the EEZ of the Russian Federation and, unlike last year, it remained until the beginning of the third decade of October. The “warm” type of hydrological conditions causes this duration of the fishery. Saury moved outside the EEZ in late October. Fishing for sardines and mackerel began in mid-July 2018 and was carried out on the northern periphery of the eddy A. However, at the end of October, unlike in 2017, fishing here practically stopped due to a decrease in the temperature drops at the peripheral fronts of the eddy caused by the high temperature of the surface waters of the Oyasio current. In late October - the first half of November in 2018, mackerel and sardine fished in high-gradient areas of the Northern Subarctic Front (NSAF) close to the eastern and southern borders of the Russian EEZ. During fishing season 2018, in contrast to the previous year, schools of sardines and mackerel remained much longer in the economic zone of Russia.

Comprehensive research information on hydrology-hydrochemical structure of the Middle Caspian Sea in July-August 2019 on board of R/V “Issledovatel’ Kaspiya” is presented in the article. Data on dissolved oxygen, hydrogen sulfide, basic nutrients (ammonium, nitrite and nitrate nitrogen; mineral phosphorus) and dissolved organic carbon were obtained in four quasi-latitudinal sections using the probing complex SBE19 plus Sea Bird, equipped with a series of sensors and twelve Niskin bathometers. It is shown, that the distribution patterns of determined elements and vertical structure correspond to average annual values of the summer season. Despite the sea level decline, the thickness of hydrogen sulfide layer of the Caspian Sea hasn’t decreased.