Based on expeditions and experimental studies, energy characteristics underlying the interaction of energy exchange processes were assessed quantitatively in fishes of the Arctic. The linear and weight growth was studied for the first time in the nonmigratory species Arctic flounder Liopsetta glacialis (Pallas, 1776) of the Kara Sea. It was found that deceleration of biosynthetic processes leads to a relative decrease in the proportion of entropy generated by metabolic processes in cold-water marine fish species, while the growth becomes more efficient at low temperatures.

Forestalling the decline of global biodiversity requires urgent and transformative action at all levels of government and society, particularly in the Arctic Ocean and adjacent seas where rapid changes are already underway. Amid growing scientific support and mounting pressure, the majority of nations have committed to the most ambitious conservation targets yet. However, without an approach that inclusively and equitably reconciles conservation and sustainable ocean use, these targets will likely go unmet. Here, we present ArcNet: a network design framework to help achieve ocean-scale, area-based marine conservation in the Arctic. The framework is centred around a suite of web-based tools and a ~ 5.9 million km2 network of 83 priority areas for conservation designed through expert-driven systematic conservation planning using conservation targets for over 800 features representing Arctic biodiversity. The ArcNet framework is intended to help adapt to new and emerging information, foster collaboration, and identify tailored conservation measures within a global context at different levels of planning and implementation.

Integrated marine studies were carried out by researchers at the Murmansk Marine Biological Institute, Russian Academy of Sciences, during an August 2023 cruise on the R/V Dalnie Zelentsy within the national project “Science and Universities.” The studies included CTD sampling; hydrological, hydrochemical, hydrobiological, ichthyological, and radioecologic studies; and observations of marine birds and mammals. The outcome of the cruise was new data on the reference state of the eastern Barents Sea ecosystem.

— Based on the expedition and literature data, the ichthyoplankton in the southwestern part of the Kara Sea is described. Larvae and pelagic fry of 22 fish species belonging to 19 genera, 10 families, and five orders were found in the study area from 1921 to 2019. Maps of the distribution of the most numerous species in 1981 and 2012–2015 are presented, as well as the data on the distribution density of species per unit volume and area in 2012–2015. It is established that over the past 38 years, the species composition of ichthyoplankton has not been replenished with any species and, first of all with representatives of the boreal complex, which indicates the absence of the processes of borealization of the ichthyofauna of this area observed in some other areas of the Arctic.

— Information on the distribution and occurrence of three species of the genus Liparis , Liparis bathyarcticus Parr, 1931, L. cf. fabricii Krøyer, 1847 and L. tunicatus Reinhardt, 1836 on the shelf of the Laptev and East Siberian seas, depending on the temperature, salinity and sediment types is presented according to the data of trawl surveys in 2014 and 2017. L. cf. fabricii is the most common species in the surveyed water area with the frequency of occurrence of 22.4% in the Laptev Sea and 24.7% in the East Siberian Sea. The total relative abundance and biomass of all species of the genus Liparis in the East Siberian Sea (377.7 ind./km 2 and 9.14 kg/km 2 ) were slightly higher than in the Laptev Sea (326 ind./km 2 and 8.32 kg/km 2 ). The maximum length of L. tunicatus in the East Siberian Sea (172 mm) exceeds the previously known one (160 mm). The average length and weight of fish of all three species of Liparis in the East Siberian Sea are greater than in the Laptev Sea.

Based on bottom trawl catches during the years 2002–2017, we present the first large-scale baseline on the spatial distribution and abundance of ice cod Arctogadus glacialis (Peters, 1874) in the fjords and on the shelf in Northeast Greenland (latitudes 70 °N–78 °N). Ice cod abundance peaked in the secluded sill fjords such as Bessel Fjord, Brede Fjord, Clavering Ø fjord system and Kong Oscar Fjord as compared to the offshore shelf. The mean biomass was estimated as 3.9 kg/km2 on the shelf and 49.3 kg/km2 in the fjords. Nearly 45% of the biomass was restricted to temperatures < −1.0 °C and almost 90 % of the biomass occurred within 200–600 m depth. This corresponds well with the deep, subzero fjords along the Northeast Greenland coast which, thus, appear the most suitable habitat for ice cod. Moreover, there was a gradual decrease in ice cod biomass on the shelf over the years 2002–2017. This apparent relocation of ice cod matches the ongoing warming of the Northeast Greenland shelf waters. Given that the overall temperature space of ice cod spans less than 4 ºC in Northeast Greenland, it is likely that the species is particularly vulnerable to climate change as warmer waters before long enter the fjords, i.e., the main habitat for ice cod.

The ichthyological studies carried out at the shelf of North-Eastern Greenland in 2002–2017 new regions of dwelling of beaked redfish Sebastes mentella were discovered. It is shown that the distribution of underyearlings is not limited to the European shelf, but extends much further to the west, to the deep-water part of the Fram Strait. Juvenile individuals of beaked redfish constantly occur off North-Eastern Greenland, where the branches of the Gulf Stream reach its shelf, and further south to the area of the formation of a circular current in the eastern part of the Greenland Sea and western the Norwegian Sea. It is likely, that this cyclonic system and the cold Greenland Current are an integral part of the feeding and migratory path of larvae, juvenile specimens and adult beaked redfish to the area of its reproduction on the European shelf, as well as in the Irminger Sea.

The population structure and growth rate of polar cod Boreogadus saida in the Laptev Sea are analyzed based on the materials collected in the summer–autumn period of 2014. The catches included individuals with lengths of 3.5–28.5 cm and a weight of 0.6–129.0 g at ages 0+ to 7+. The modal age group is represented by 2-year-old individuals and the most abundant size group is formed by individuals with lengths of 7–14 cm (63–69%), mainly at ages 1+ and 2+. The highest absolute growth increments in the length of polar cod are observed in the first three years of life (on average 3.4 cm/year), followed by their gradual decrease to 1.0 cm/year by the age of 7 years. The specific rate of linear and weight growths of polar cod decreases throughout its life: from 0.446 at age 0+ to 0.047 in 7-year-old individuals and from 1.085 to 0.146, respectively. Polar cod reaches sexual maturity at an average length of 10 cm at age 1+; the bulk of individuals mature at a length of 13–17 cm at ages 2+ to 3+.

The main results of researches of laboratory of ichthyology of the MMBI RAS in the period from 2015 to 2019 are presented. Data on the ichthyofauna of bays and fjords of North-Eastern Greenland, spatial distribution of some species of the Cottidae, Liparidae and Zoarcidae families in the Arctic seas of Russia, as well as on the dynamics of fish diversity in the coastal and sub-coastal zones of Eastern Murmansk are provided. Quantitative data on Barents sea Polar cod productivity, bioenergetic and adaptations of boreal and Arctic fish species were obtained.Aspects of the morphology of the thymus of lumpfish larvae used in aquaculture to control parasitic crustaceans are considered.

Article present the main results of the investigations deal withthe program of the Presidium Russian Academy of Science “Bioresourcesof the Arctic seas of Russia: current state, the effectof natural changes and anthropogenic impacts, scientific foundations and perspectives for use”and linked researches.

On the basis of material from expeditions to the Laptev Sea in 2014, information is presented on occurrence, spatial-bathymetric distribution, water temperature and salinity, and types of ground in habitats of six species of eelpouts: shulupaoluk Lycodes jugoricus, pale eelpout L. pallidus, polar eelpout L. polaris, Arctic eelpout L. reticulatus, archer eelpout L. sagittarius, and wattled eelpout L. cf. palearis. Specimens similar to the wattled eelpout L. cf. palearis are found in this sea for the first time—in shallow water of Kotelniy Island (20–43 m). The polar eelpout is a common, relatively abundant, and widely distributed species in the Laptev Sea. Its frequency of occurrence is 24.7 vs. 1.2−6.2% of the other five species. The size of captured specimens, as well as the length-weight ratio of shulupaoluk and polar eelpout, is reported. Diet composition of shulupaoluk, polar eelpout, and Arctic eelpout is examined.

The range of the rarely caught fathead sculpin species Cottunculus subspinosus has been considered restricted to the waters off East Greenland and Northeast Iceland. For the first time the species is recorded from the east side of the Norwegian Sea, and also it is found further north in the Greenland Sea than previously known. Mapping all the corroborated specimens known indicates that the species seems confined to the continental slopes of the Nordic Seas, where it is found in waters with a temperature below zero and a depth of more than 900 m. Depth distribution shows almost no overlap with the closely related sympatric Cottunculus microps, perhaps as a result of competitive exclusion.

The somatic and generative production and the P/B-coefficient of polar cod Boreogadus saida of the Barents Sea were calculated using a long-term dataset (1969–2013). It has been found that the main contribution to the production in 1969–1978 was made by the individuals aged 1+–4+, while that in a later period was by the fish aged 1+–2+; the share of somatic production varied from 54 to 94%. In 1986–2013, a decrease in generative production was observed in all age groups. The intensity of production processes increased in 1969–2004 and declined in 2005–2008 and in 2013. The average annual P/B-coefficient of the polar cod varied from 0.62–1.10, which was significantly lower than the hypothetical expert value (1.5).

The first record of the juvenile northern wolffish Anarhichas denticulatus was reported 570 km away from the nearest border of the species natural habitat near the island of Jan Mayen, on the continental slope of Northeast Greenland. Also original and published data on the occurrence of juvenile northern wolffish in the European Arctic and North Atlantic are presented.