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In order to explore changes and trends in the timing of Arctic sea ice melt onset and freezeup, and therefore melt season length, we developed a method that obtains this information directly from satellite passive microwave data, creating a consistent data set from 1979 through present. We furthermore distinguish between early melt (the first day of the year when melt is detected) and the first day of continuous melt. A similar distinction is made for the freezeup. Using this method we analyze trends in melt onset and freezeup for 10 different Arctic regions. In all regions except for the Sea of Okhotsk, which shows a very slight and statistically insignificant positive trend (0.4 d decade−1), trends in melt onset are negative, i.e., toward earlier melt. The trends range from −1.0 d decade−1 for the Bering Sea to −7.3 d decade−1 for the East Greenland Sea. Except for the Sea of Okhotsk all areas also show a trend toward later autumn freeze onset. The Chukchi/Beaufort seas and Laptev/East Siberian seas observe the strongest trends with 7 d decade−1. For the entire Arctic, the melt season length has increased by about 20 days over the last 30 years. Largest trends of over 10 d decade−1 are seen for Hudson Bay, the East Greenland Sea, the Laptev/East Siberian seas, and the Chukchi/Beaufort seas. Those trends are statistically significant at the 99% level.

Recent investigations, based mostly on molecular data, have unraveled the evolutionary history of several common ribbon worm (phylum Nemertea) species and solidified the taxonomic status of many higher taxa within the group. However, a large proportion of enigmatic species have yet to be placed in a phylogenetic framework. We investigated the phylogenetic positions of 26 novel and/or perplexing nemertean species from the Sea of Okhotsk, the Sea of Japan, the Kuril–Kamchatka Trench, and Vietnam (including the first record of a reptant nemertean from the Far East seas of Russia). We conducted both maximum likelihood and parsimony analyses, utilizing four molecular loci—mitochondrial COI and 16S rRNA, as well as nuclear 18S rRNA and 28S rRNA—finding that the current classification for most of these species is corroborated by their phylogenetic placement. We then discuss the evolution of some unique morphological traits possessed by some of these species, using the molecular phylogeny as a backbone for our general conclusions.

The mercury pollution status in the northwestern Sea of Okhotsk remains largely unexplored. In this study, hair samples were collected from 40 bearded seals harvested between August and October 2021 in the region. Total mercury (THg) concentrations in the samples exhibited a wide range from 137 to 1885 ng/g (median: 407 ng/g). While no significant differences in THg concentrations were found between male and female seals, distinctions were observed between young and potentially mature seals. Stable nitrogen isotope analysis indicated that juveniles and mature adults did not differ, although sample sizes were limiting. The higher THg concentrations in juveniles were attributed to variations in the seals’ diets and/or variations in foraging locations during the juvenile stage which likely contribute to THg differences due to greater seasonal migration to offshore habitats. Notably, THg levels in bearded seals from the northwestern Sea of Okhotsk were lower in comparison to other pinniped species in the North Pacific. These findings, representing the first dataset for this pinniped species in the Russian segment of its habitat, contribute insights into mercury exposure in the Sea of Okhotsk mammalian population.

This study provides a holistic view of the coupled ocean-atmosphere-sea ice processes responsible for generating interannual variability in sea ice coverage in the Sea of Okhotsk as well as the atmospheric response to this variability. Simulations from the Community Earth System Model Large Ensemble project are analyzed, providing the ability to elucidate the time evolution of these relationships through weekly lead-lag composite analysis, while maintaining a large number of samples to provide robust conclusions. We find that thermodynamic processes involving anomalous ocean-atmosphere heat fluxes affect the timing of initial sea ice growth in the Sea of Okhotsk as early as November. Low-level wind anomalies in the winter affect the extent to which sea ice fully develops, both through advection of the sea ice itself and through changes in the transport of air masses over the Sea of Okhotsk. In this study, the results synthesize and support a diverse set of mechanisms identified in previous observational studies to be responsible for anomalous sea ice conditions, but in a coupled global climate model framework with a large sample size. We also find evidence that anomalous ocean-atmosphere heat fluxes in the winter can trigger an atmospheric response comprised of a local negative sea-level pressure anomaly and Rossby wave that extends over North America. The sign of the turbulent heat fluxes relative to the sea ice anomalies confirm that this is indeed a lagged response of the atmosphere forced by sea ice anomalies. This validates the Rossby wave train response identified in more idealized model simulations with prescribed sea ice and sea surface temperature by demonstrating that this process also occurs in a more realistic coupled model framework.

The new snailfish Careproctus rhomboides is described on the basis of four specimens collected from the southern Sea of Okhotsk (570–825 m depth), off Hokkaido, Japan. The new species is most similar to Careproctus bowersianus Gilbert and Burke 1912, with both species having the following characters: teeth trilobed; snout blunt; cephalic pore pattern 2-6-7-2; gill slit small above pectoral fin (or extending down in front of upper ray); pectoral fin shallowly notched; pelvic disk moderately large, ca. 20% in head length; and stomach black. The new species is distinguished from congeners, including C. bowersianus, by the following combination of characters: total vertebrae 59–61; dorsal-fin rays 56 or 57; anal-fin rays 49–52; pectoral-fin rays 32–34; pyloric caeca 13–16; cephalic pore pattern 2-6-7-2, chin pores paired in separate pits; maximum body depth 22.4–30.5% in standard length (SL); inner teeth on both jaws strongly trilobed; pelvic disk oval, slightly longer than width, length 4.3–7.7% SL (18.9–33.9% head length); gill opening small, extending to just above pectoral fin; stomach black and peritoneum pale in preserved specimens.

The red king crab (Paralithodes camtschaticus) is a highly valued delicacy on the international market and currently contributes significantly to the income from fisheries in the regions where it is harvested. Russian income from red king crab export is $200–250 million per year. We review both the biology and fishery of the two largest populations of this species in Russia, i.e., in western Kamchatka (Sea of Okhotsk) and in the Barents Sea. The latter was established in the mid-1990s after introduction of red king crab to the area in the 1960s. The Barents Sea crabs are larger, grow faster and mature earlier than the crabs from the Sea of Okhotsk owing to more favorable temperature conditions in the Barents Sea. Additionally, we provide fishery information for the Prymorie population of red king crab (Sea of Japan) that remains depressed and closed for commercial fishery at present. Although the fishery period of red king crab in western Kamchatka is much longer than in the Barents Sea (1930–present time vs. 2004–present time), similar patterns were observed for the exploited king crab populations. High annual landings led to a pronounced decrease in population density and total abundance that, in turn, led to closures or some limitations of fisheries. Subsequent rehabilitations of the populations provided an opportunity for reopening of the fisheries and further exploration of red king crab populations under sustainable management. The main reason explaining a decline in red king crab populations both in the North Pacific and in the Barents Sea is high, mainly illegal, fishing pressure. Sustainable harvest strategies for the fisheries could prevent negative scenarios (overfishing) in the future.

Data of morphometric measurements of Strongylura anastomella FL 71.2 cm, which entered the fixed seine set near the mouth of the Lyutoga River on June 8, 2023 are presented. Information on its catches at other coastal sites in Sakhalin waters is considered.

— Three immature specimens of Indo-Pacific sailfish Istiophorus platypterus have been found in a catch using a fixed net from the Sea of Okhotsk side of Kunashir Island on September 27, 2023. Data of morphometric measurements of one of them are presented. The total length of the studied specimen was 1101.3 mm, fork length ( FL ) was 973.8 mm, standard length ( SL ) was 966.6 mm, lower jaw–fork length ( LJFL ) was 82.15 cm, and body weight was 2.25 kg. The temperature of the water surface layer in the catch site was 21°C on the date of the capture.

Plastic and meristic characters, position of teeth on jaws, and coloration of Okhotsk Sea fringed sculpin Porocottus minutus endemic to the north part of the Sea of Okhotsk are described.

Information has been provided on the distribution, temperature conditions of habitat and size composition of the whitecrest eelpout Petroschmidtia albonotata in the northeastern Sea of Okhotsk in July–September 2010. This species was found within the intermediate water mass at depths of 213–651 m at a water temperature at the bottom of 0–2.3°C. Accumulations of increased density were noted on the western slope of the TINRO depression and south of the Lebed trench in the bathymetric range of 213–300 and 401–500 m, respectively. The total length of the whitecrest eelpout in catches varied from 14 to 48 cm. A significant proportion of small individuals (<20 cm in length) was recorded on the western slope of the TINRO depression at depths <300 m, while larger individuals were caught to the south. Differences in thermal conditions of this species habitat within the study area have been revealed. North of 55° N, the whitecrest eelpout is concentrated at a temperature of 1.0–1.2°C, to the south—at 1.8–2.0°C. A comparison of the obtained data and literature data indicates that, depending on the region, species of the genus Petroschmidtia are characterized by significant differences in preferred depths and temperature conditions in their habitats.