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A single specimen of the northern wolffish Anarhichas denticulatus Krøyer, 1845, 393 mm in length, was documented for the first time in the Siberian Arctic (Laptev Sea, Russia). Species identification was confirmed by an integrative taxonomic approach that included examination of external morphology and DNA barcoding using the COI mtDNA gene. This species is widely distributed in the North Atlantic, but records in the Arctic Ocean are limited to the Canadian and US coasts. This record might represent a significant range extension of about 7500 km for the species and may be associated with the eastward transport of a pelagic juvenile specimen from the Northeastern Atlantic to the Laptev Sea by the North Atlantic current, consistent with the hypothesis of Atlantification of the Arctic Ocean. X-ray images of the Laptev Sea specimen and photographs showing ontogenetic variations of species' coloration are provided for reference. The Laptev Sea specimen had a more elongated shape, longer preorbital distance, and longer pectoral, dorsal, and anal fins, as well as a larger eye and wider caudal fin compared to North Atlantic samples. The size differences are likely associated with conditions experienced as a juvenile during the pelagic stage of the lifecycle. [ABSTRACT FROM AUTHOR]

The article presents the results of a study of activity levels and features of the vertical distribution of 210Pb, 137Cs, 234U, 238U and their relationship with the physicochemical parameters of peat deposits. Analysis of the data showed that the vertical distribution of 137Cs and 210Pb was related to the content of water-soluble salts, the water saturation of the deposit, and the values of Eh (oxidation–reduction potential) and rH (relative humidity), which indicates a complex geochemical barrier at a depth of 20 cm in the peat core. The 210Pb dating of the peat core, carried out according to the CF model using the Monte Carlo method (to improve the dating accuracy), showed that the above horizon corresponded to 1963, which is consistent with the data of the 137Cs reference horizon and in terms of several physicochemical parameters (in particular, ash content) also corresponds to the age of 1963, which confirms the correctness and adequacy of the chosen peat core dating model. The peak of anthropogenic radionuclides in peat deposits correlates with a particular major event in the history of radioactive fallout, the Partial Nuclear Test Ban Treaty of 1963, providing a benchmark for geochronological research. The obtained results of the linear accumulation rate, the mass accumulation rate of the peat deposit, and the value of the atmospheric flux of 210Pb are congruent with the data on the peatlands of Northern Europe and the data obtained by earlier analysts of the Subarctic region of European Russia. [ABSTRACT FROM AUTHOR]

The features of the spatial and vertical distributions, and size–age and size–sex structures of the ribbed sculpin Triglops pingelii of the Kara Sea are presented. In September 2019, this species was recorded at depths from 18 to 235 m at a bottom temperature from −1.5 to +1.6 °C. The densest concentrations were recorded northeastward of the Yamal Peninsula, at the outlet of the Gulf of Ob at a depth of 18–21 m and a bottom temperature from −1.5 to −1.0 °C. Individuals with a length of 46–126 mm and a body weight of 0.35–15.60 g aged 1+ to 4+ years were recorded in trawl catches. However, fish with a length of 51–90 mm and a body weight < 6 g aged 1+–2+ years dominated. Among fish > 71 mm long, the proportion of females increased sharply, reaching 100% with a length of 120 mm. The individual fecundity of female ribbed sculpins in the Kara Sea with a length of 89–123 mm varied from 100 to 316 (on average 215 ± 15) eggs. It is shown that this species is a necto-bentho-ichthyophage whose main prey are benthic and bentho-pelagic crustaceans (mainly amphipods and mysids), as well as juveniles of various fish, the total proportion of which is >99% of the food weight. In this sculpin, age-related changes in the diet composition are well expressed, i.e., as the size increases, the relative importance of the former prey group decreases sharply, and that of the latter two groups, on the contrary, increases. A comparative analysis of data on the biology and distribution of the six most abundant or common Triglops spp. makes it possible to attribute the ribbed sculpin to medium-sized representatives of the genus, whose maximum length is similar to those of T. jordani from the North Pacific, as well as T. murrayi and T. nibelyni from the Arctic. The lifespan of the ribbed sculpin is within the same limits as reported for other Triglops spp. Its individual fecundity in the Arctic seas is comparable to that of other Triglops species living here, but is significantly lower than that of individuals of this species and other congeners from the northwest Pacific Ocean. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recent climate change resulted in significant increasing of captures of boreal fish species in the Siberian Arctic. • The ranges of some North Atlantic species have significantly extended eastward. • The ranges of some North Pacific species have significantly extended westward. • Records of boreal fishes in the Siberian Arctic in the open databases (OBIS, GBIF, and FishBase) are very limited. The occurrence, abundance, biomass and size composition of six boreal fish species (walleye pollock Gadus chalcogrammus , Pacific cod G. macrocephalus , northern wolffish Anarhichas denticulatus , beaked redfish Sebastes mentella , Greenland halibut Reinhardtius hippoglossoides , glacier lanternfish Benthosema glaciale) in the Siberian and Pacific Arctic are presented based on the analysis of open databases (OBIS, GBIF and FishBase) and the results of scientific surveys of TINRO 1977–2020. In open databases, information on the records of these species is available mainly for the eastern Chukchi Sea and the Beaufort Sea and is practically absent for the seas of the Siberian Arctic, which is due to technical reasons. Data from long–term surveys of TINRO indicate the extension of the ranges of North Atlantic species eastward and North Pacific species westward indicating the ongoing borealization of the Siberian Arctic due to a changing climate. At the species level, it can lead to the overlap of the ranges of the "western" and "eastern" populations of Greenland halibut, as well as the ranges of Pacific and Greenland cods, which will make it possible to exchange genetic material between these populations/species and will contribute to the disappearance of genetic differences between them. [ABSTRACT FROM AUTHOR]

In 2016, an outbreak of anthrax killing thousands of reindeer and affecting dozens of humans occurred on the Yamal peninsula, Northwest Siberia, after 70 years of epidemiological situation without outbreaks. The trigger of the outbreak has been ascribed to the activation of spores due to permafrost thaw that was accelerated during the summer heat wave. The focus of our study is on the dynamics of local environmental factors in connection with the observed anthrax revival. We show that permafrost was thawing rapidly for already 6 years before the outbreak. During 2011–2016, relatively warm years were followed by cold years with a thick snow cover, preventing freezing of the soil. Furthermore, the spread of anthrax was likely intensified by an extremely dry summer of 2016. Concurrent with the long-term decreasing trend in the regional annual precipitation, the rainfall in July 2016 was less than 10% of its 30-year mean value. We conclude that epidemiological situation of anthrax in the previously contaminated Arctic regions requires monitoring of climatic factors such as warming and precipitation extremes. [ABSTRACT FROM AUTHOR]

The article presents the results of hydrobiological, ichthyological, trophological, acoustic, and genetic research aboard the R/V Professor Levanidov in the Chukchi, East Siberian, Laptev, and Kara seas during August 8–October 2, 2019. The distribution of species-indicators of vulnerable marine ecosystems was studied and the amount of seabed litter was estimated. [ABSTRACT FROM AUTHOR]

The pollution of the Siberian Arctic seas bottom by anthropogenic debris is assessed for the first time based on the results of bottom trawl surveys conducted in the Chukchi, East Siberian, Laptev, and Kara seas in 2019. In the East Siberian Sea and the Laptev Sea, no seabed litter was detected. The debris on bottom and near bottom was found in the Kara and Chukchi seas only. Plastic was the most frequently occurring type of seabed litter. The main source of the garbage encountered in the Kara Sea is the waste related to fishing activities in the Barents Sea. • The first assessment of the composition and amount of seabed litter in the Siberian Arctic is done. • No debris was found in the East Siberian and Laptev Sea. • The maximum amount of litter was detected in the Kara Sea. • Plastic has been the most frequently occurred type of seabed litter. • The main source of the garbage in the Kara Sea is the fishing fleet operated in the Barents Sea. [ABSTRACT FROM AUTHOR]

The first records of walleye pollock Gadus chalcogrammus Pallas, 1814 in the seas of the Siberian Arctic (the Laptev Sea, the Kara Sea, the southeastern Barents Sea), are documented. Information about the external morphology (morphometric and meristic characters), photos of sagittal otoliths and fish, and data on the sequences of the CO1 mtDNA gene are presented. The results of a comparative analysis indicate that walleye pollock caught in the Siberian Arctic do not differ in principle from North Pacific and North Atlantic individuals. Previous conclusions about the conspecificity of the walleye and Norwegian pollock Theragra finnmarchica are confirmed. New captures of walleye pollock in the Siberian Arctic allow us to formulate a hypothesis about its continuous species' range from the coasts of Norway in the North Atlantic to the coasts of Korea, Japan, and California in the North Pacific. The few records of walleye pollock in the North Atlantic originate from the North Pacific due to the transport of early pelagic juveniles to the Arctic by currents through the Bering Strait and further active westward migrations of individuals which have switched to the bentho-pelagic mode of life. [ABSTRACT FROM AUTHOR]

New data on lipid and fatty acid profiles are presented, and the dynamics of the studied components in muscles in the males and females of the beaked redfish, Sebastes mentella, in the depth gradient of the Irminger Sea (North Atlantic) is discussed. The contents of the total lipids (TLs), total phospholipids (PLs), monoacylglycerols (MAGs), diacylglycerols (DAGs), triacylglycerols (TAGs), cholesterol (Chol), Chol esters, non-esterified fatty acids (NEFAs), and wax esters were determined by HPTLC; the phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylcholine (PC), and lysophosphatidylcholine (LPC) were determined by HPLC; and fatty acids of total lipids were determined using GC. The Chol esters prevailed in muscles over the storage TAGs, and the wax ester content was high, which is a characteristic trait of vertically migrating species. Specific dynamics in certain PL in redfish were found to be depended on depth, suggesting that PLs are involved in the re-arrangement of the membrane physicochemical state and the maintenance of motor activity under high hydrostatic pressure. The high contents of DHA and EPA were observed in beaked redfish muscles is the species' characteristic trait. The MUFAs in muscles include dietary markers of zooplankton (copepods)—20:1(n-9) and 22:1(n-11), whose content was found to be lower in fish sampled from greater depths. [ABSTRACT FROM AUTHOR]

The seasonal dynamic of lipids and their fatty acid constituents in the lipid sac and muscles of pelagic postlarval Leptoclinus maculatus, an ecologically important fish species in the Arctic food nets, in Kongsfjord, Svalbard waters was studied. The determination of the qualitative and quantitative content of the total lipids (TLs), total phospholipids (PLs), triacylglycerols (TAGs), cholesterol (Chol), cholesterol esters (Chol esters) and wax esters was analyzed by TLC, the phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylcholine (PC), lysophosphatidylcholine (LPC) and sphingomyelin (SM) were determined by HPLC, and fatty acids of total lipids using GC. The lipid sac is a system of cavities filled with lipids, and it is not directly connected to organs of the digestive system. The wall's inner layer is a multinuclear symplast that has a trophic function. The results provide additional knowledge on the role of lipids in the biochemical and physiological adaptation of fish to specific environments and clarify the relationship between fatty acids and the food specialization of postlarvae. Analysis of the fatty acid (FA) profile of TLs in the muscles and lipid sac of daubed shanny pelagic postlarvae showed it to be tissue- and organ-specific, and tightly associated with seasonal variations of environmental factors (temperature conditions and trophic resources). [ABSTRACT FROM AUTHOR]

Integrated pelagic trawl surveys were conducted in the eastern sector of the Russian Arctic (Laptev Sea, Chukchi Sea and East Siberian Sea) in August–September of 2003–2018. Data were used to further describe biology and spatial distribution of Polar cod (Boreogadus saida) in this region. Polar cod in surveyed areas are characterized by similar linear size and spatial distribution. In all surveyed seas, polar cod aggregations consisted of individuals 3–29 cm in length with the age of 0+ - 6+ years. Lower growth rates of polar cod were evident in the eastern sector compared to the Kara Sea (the western sector of Russian Arctic). The lower growth rates in the eastern sector are probably due to the significant difference in environmental conditions (mainly temperature) that directly affect polar cod metabolic rates. In the Chukchi and East Siberian seas, the main concentrations were observed within the near-bottom layer, while in the Laptev Sea they were recorded throughout the water column. The abundance and biomass of polar cod in the Chukchi Sea in different years ranged from 514 million inds. and 0.83 thousand tons (2008) to 8.26 billion inds. and 117.5 thousand tones (2003). Respective indices for the Laptev Sea amounted to 233 thousand tones and 12.75 billion individuals. The abundance and biomass of the East Siberian Sea polar cod were at a relatively low levels compared to other areas in the Russian Arctic (about 0.150 thousand tons and 20 million individuals). [ABSTRACT FROM AUTHOR]

Presented here are data on the size composition and age structure, the sex ratio, the state of maturity of the gonads, and the composition of the diet and feeding habits of walleye pollock in the western Chukchi Sea, based on 2003-2020 bottom and mid-water trawl surveys conducted onboard Russian research vessels. During all years of research, mid-water trawl catches in this area were dominated by juveniles with FL 5–12 cm, while the size composition of walleye pollock in bottom trawl catches was bimodal with the dominance of fish 7–14 cm and 50–62 cm long. Females were considerably larger than males (on average by almost 10 cm), with mean FL 56.0–58.3 cm and 52.1–56.4 cm, respectively, in different years. The age structure of walleye pollock was significantly different from that of both the western and eastern Bering Sea since fingerlings and yearlings predominated there in the mid-water trawl catches, and fish under the age of 1 year and 6–17 years were the most numerous in the bottom trawl catches. In the western Chukchi Sea in 2018–2020, the proportion of females in bottom trawl catches ranged from 1.8 to 2.7 females per male. This is probably because walleye pollock here were represented mainly by large fish, while in the mature part of the population, females are usually larger than males. The proportion of fish with gonads at different stages of maturity varied significantly in different years. Immature individuals were extremely few among the fish analyzed. Individuals with developing and post-spawning gonads accounted for a major part of the catches. In recent years, walleye pollock of both sexes have been observed in pre-spawning, spawning, and post-spawning condition, which may indicate the possibility of spawning of individual specimens in the western Chukchi Sea. The survival of eggs, larvae, and fry in conditions of low temperatures is unlikely. However, if the warming in the Arctic continues, it is possible that new walleye pollock spawning grounds may appear in the Chukchi Sea. In the western Chukchi Sea, the proportion of euphausiids in the diet of large walleye pollock (>40 cm in 2018 and > 60 cm in 2019) was significantly higher than that of small fish (<40 cm). In the average long-term plan, the decrease in its diet with the growth was characteristic only for planktonic organisms (small crustaceans, chaetognaths, and larvaceans). Only large benthic crustaceans showed an increase in the walleye pollock diet as it grew. There were no pronounced trends regarding euphausiids and fish. In the western Chukchi Sea, the cannibalism was registered only in large individuals (40–60 cm and >60 cm) and only in 2019 with small number juveniles consumed. Such a low level of cannibalism was probably due to the spatial separation of juveniles and adults, as well as the presence of a sufficient amount of other prey. [ABSTRACT FROM AUTHOR]