Survey report (Part 1) from the joint Norwegian/Russian Ecosystem Survey in the Barents Sea and the adjacent waters August-October 2023

Figures by: S. Karlson and E. Bagøien

BESS aims to cover the entire ice-free area of the Barents Sea, from south to north. The ecosystem stations are distributed on a regular 35×35 nautical mile regular grid with the exception of the slope around Svalbard/Spitsbergen, with additional bottom trawl hauls for demersal fish indices estimation and additional acoustic transects east for Svalbard/Spitsbergen for the capelin stock size estimation. The planned vessel tracks for BESS 2023 are given in figure 2.1.

According to the plan, BESS 2023 was largely implemented. The realized tracks of the research vessel with the sampling taken are shown in Figures 2.2 and 2.3. The execution of BESS 2023 did not reveal any major changes or irregularities. The Russian vessel did not have enough allocated vessel-days to cover the region east of Franz Josef Land and in the north-eastern part of the survey area (Figures 2.2 and 2.3). A relatively large part of the Russian EEZ west of the Novaya Zemlya was closed for fishing at the request of the Russian Ministry of Defence, so survey area along the archipelago coast was not fully covered (Figure 2.2). For the same reason, some of the coverage of the Loophole has been moved from G.O. Sars part 1 to G.O. Sars part 2. A decrease in the number of standard pelagic trawls and reduced area coverage west of the Novaya Zemlya may lead to some underestimation of 0-group of cod, and significant underestimation of the polar cod stock size, including 0-group and juvenile Greenland halibut numbers. BESS 2023 was largely conducted according to the planned time schedule. In recent years, the number of ship days for a Russian vessel has been reduced with 10 %, while additional tasks (such as microplastic samples) have been added, leading to a reduction in survey area coverage. The planned schedule for BESS 2023 was 148 days (98 NOR+50 RUS), while the effective vessel days (time between first and last sample in the vessel logs) was 129 days (83 NOR+46 RUS). The difference between the two is as expected, as vessels need time for sailing to and from the harbor and preparation before sampling. The temporal and spatial progression during the survey was good (Figure 2.4). Weather conditions were very good for most of the period. Note that in reports from earlier years, only the planned schedule is reported.

The ecosystem survey in 2023 was similar to previous years, covering most ecosystem components. In addition to the standard coverage of most ecosystem components, the Norwegian vessels covered the oceanography sections “Vardø-Nord”, “Sørkapp-Vest”, and “Hinlopen” and the Russian vessel covered “Kola” section twice (Figure 2.3). During the BESS, a total of 362 pelagic hauls and 337 demersal were taken.

3.1 Databases

A wide variety of data are collected during the ecosystem surveys. All data collected during the BESS are quality controlled and verified by experts Herdis Langøy Mørk and Elena Eriksen (IMR) and Tatyana Prokhorova (PINRO-VNIRO) during and after the survey. The data are stored in IMR and PINRO national databases, with different formats. However, the data are exchanged so that both sides have access to each other’s data and use equal joint data.

3.2  Data applications

The BESS aim to cover the whole Barents Sea ecosystem geographically and provide survey data for commercial fish and shellfish stock estimation. Stock estimation is particularly important for capelin, because capelin TAC is based on the survey result, and the Norwegian-Russian Fishery Commission determines TAC immediately after the survey. In addition, a broad spectrum of physical variables, ecosystem components and pollution are monitored and reported. The survey data will be used by each party for various purposes within the framework of national and international programs.

This survey report is based on joint data and contains the main results of the monitoring. The survey report will come in two parts and will be published in the IMR/PINRO Joint Report series.

All reports from BESS from 2004 until the latest are available at this web site: https://imr.brage.unit.no/imr-xmlui/handle/11250/2658167. This report is published in the IMR digital report series Joint  IMR/PINRO Reports.

3.3  Time series of distribution maps

The redesigned IMR web site for the joint Norwegian/Russian Barents Sea Ecosystem Surveys is still not finished. The maps from this report series are to be made public in this map site when ready.

Ch. 4 Marine Environment is published in

Survey report (Part 2) from the joint Norwegian/Russian Ecosystem Survey in the Barents Sea and the adjacent waters August-October 2023

5.1  Phytoplankton

Text by S.J. Lerch

Figures by S.J. Lerch

Samples used to characterize phytoplankton community composition and abundance were collected from a total of 108 stations over the course of four separate cruises. Samples were collected from Hinlopen and Vardø-Nord Utvidet during the ecosystem cruise (cruise numbers: 2023007016, 2023002011) between September and October, and Fugløya-Bjørnøya during transect cruises conducted in April (2023006008), May (2023002007), and August (2023002010). Microscopy was used to identify and quantify taxa in 39 preselected stations along the transects, covering multiple ICES sub-regions (Figure 5.1.1). Algae-net and metabarcoding samples were also collected which can be used to qualitatively assess community composition. In total, 28 Algae-net and 67 metabarcoding samples were collected. 

Samples for algal cell counts (100 ml) were taken from 10 m CTD collected water and fixed in Neutral Lugol. Microscope counts were performed following the Utermöhl (1958) method on CTD samples to quantify abundance and community composition at the IMR Flødevigen Plankton Laboratory. Qualitative Algae-net samples were collected using a vertical net tow (10 μm mesh; 0.1 m² opening; 30-0 m), fixed with 2 ml 20% formalin and stored for future use. Metabarcoding samples were collected by filtering approximately 2 L of seawater, pre-filtered with 180 µm mesh, on to 25 mm filters with a pore size of 5 µm. Samples were then stored at -80 °C for future DNA extraction and sequencing. 

Microscopy algal counts include heterotrophic and autotrophic groups, these communities will therefore be referred to as microplankton in the summarized results below.

5.1.1 Results and discussion

Based on microscopy counts, the average concentration of Barents Sea microplankton in the late summer/ early fall (August-October) was 3.41×10⁵ ± 2.25×10⁵ cells L^-1. The average community was numerically dominated by flagellates (55%, 1.86×10⁵ ± 1.11×10⁵ cells L^-1), diatoms (19%, 6.47×10⁴ ± 1.40×10⁵ cells L^-1), and cryptophytes (15%, 5.10×10⁴ ± 4.24×10⁴ cells L^-1).

Microplankton abundances and communities varied spatially across the Barents Sea in the late summer/ early fall (Figure 5.1.2). Cell concentrations varied by nearly two orders of magnitude between stations with a minimum concentration of 3.50×10⁴ cells L^-1 and maximum of 1.01×10⁶ cells L^-1. Higher concentration stations were generally found south of 74°N. The majority of Vardø-Nord and Hinlopen communities were flagellates and cryptophytes, while the Fugløya-Bjørnøya stations had large contributions from diatoms in addition to flagellates.

Within these data, diatoms are the only purely photosynthetic group described at a high taxonomic level. During the late summer/ early fall, diatom abundance was greatest near Bear Island and diatom community composition varied spatially (Figure 5.1.3). Leptocylindrus minimus comprised a large proportion of the community at multiple stations in Vardø-Nord and Fugløya-Bjørnøya. In addition, Probosica alata, Cylindrotheca Closterium and Pseudonitzschia are numerically important at some of the other stations with high diatom concentrations.

The combination of August and spring sampling along the Fugløya-Bjørnøya transect allows us to describe seasonal differences in microplankton cell concentrations and community composition.  Average cell concentrations measured were the same order of magnitude in August (5.24×10⁵ ± 2.59×10⁵ cells L^-1) and in the Spring (3.67×10⁵ ± 5.14×10⁵ cells L^-1), although Spring samples were characterized by greater intra-station variability with particularly high cell concentrations at fixed station 1 in April (Figure 5.1.4). At the broad taxonomic group level, the Fugløya-Bjørnøya transect communities were variable with the only seasonal pattern being greater diversity and presence of diatoms across samples in August relative to the Spring (Figure 5.1.4). Diatom community composition shows clearer seasonal patterns (Figure 5.1.5). Chaetoceros and Thalassiosira were found almost exclusively in the spring and Skeletonema was found only in April. In contrast the August community was dominated by Proboscia alata and contained the only detection of Cerataulina pelagica, Cylindrotheca Closterium, and Guinardia delicatula.  

5.2     Distribution and biomass indices of jellyfish

Text by E. Eriksen, D. Prozorkevich, T. Prokhorova and A. Dolgov

Figures by E. Eriksen

The biomass of gelatinous zooplankton was calculated using SAS (for the new 23 fisheries subareas, 1980-2017). The new 13 subareas, based on environmental status and bathymetry, were used from 2018 (Figure 6.2) to present spatial variation of jellyfish abundance and biomass. The R-script has been developed during the last three years, and during the last year some mistakes in the calculations were corrected. Thus, the biomass shown in previous reports may slightly differ from the latest one.

Here, we present the time series for biomass indices calculated by SAS (1980-2017) and by R (2018-2023). Spatial biomass indices calculated by R for 2004-2023.

In August-October 2023, lion’s mane jellyfish (Cyanea capillata; Scyphozoa) was the most common jellyfish species, both with respect to weight (average density of 15.8 tonnes per nautical miles (nmi) and occurrence (found at 261 of 276 stations) (Figure 5.2.3.1). Higher densities (> 10 tonnes per sq nmi) were found widely in the Barents Sea (Figure 5.2.3.1).

Moon jellyfish Aurelia aurita was found at 82 stations in the southern Barents Sea with an average biomass of 1 416 kg per nmi (Figure 5.2.3.2). Some few catches were also taken further north (3 stations), west (1 station) and east (4 stations).

Blue stinging jellyfish, Cyanea lamarckii, was found at 19 stations in the western Barents Sea with average biomass 87.7 kg per nmi, which indicated an increase from earlier year (Figure 5.2.3.3). C. lamarckii has been observed regularly in the Barents Sea in recent years and the presence of this warm-temperate species may be linked to the inflow of Atlantic water masses.

Ctenophores were found at 6 stations in the west and southeastern Barents Sea, with densities below 4 kg per sq nmi (3 stations) and above 80 kg (86, 157 and 233 kg per nmi), that was also unusual. Hyperiid amphipod Hyperia galba living into schiphoid jellyfish was found at 4 stations in southwest and two stations in the north with an average densities of 0.3 kg per nmi.

Biomass indices were calculated as total, for large jellyfish, dominating by C. capillata, small jellyfish dominating by A. aurita and undetermined jellyfish for the period 2004-2023. In 2023, total jellyfish biomass in the Barents Sea was similar to the record high in 2001 and was 4.905 million tonnes (Figure 5.3.3.3). Jellyfish biomasses dominated by biomasses of large jellyfish (4.743 million tonnes), although biomass of small jellyfish (dominated by A. aurita) was the highest recorded (130 thousand tonnes, Figure 5.2.3.4).

Geographical distribution of jellyfish, mainly C. capillata, showed an increase in central, southern, eastern, and northern areas since 2013 with the widest distribution in 2023, when biomasses reached almost 5 million tonnes (Figure 5.2.3.5).

5.3  Distribution and biomasses of euphasiids and amphipods

5.3.1   Distribution and biomass of euphasiids

Text by E. Eriksen, B. Husson, A. Dolgov, D. Prozorkevich and T. Prokhorova

Figures by B. Husson and S. Karlson

Biomass estimates were calculated by different softwares during the last four decades: Excel (up to 2017) and R (since that). The new 15 subareas, based on similar environmental status, were used since 2018 (Figure 5.3.1.1). These areas were used to get more detailed information about the distribution of the krill within the survey area. The main differences between these two sets of estimates were that Excel used the average biomass of all stations to calculate the total biomass, while R used the average biomass for each of the 15 subareas and thus reducing the impact of single very high catches. In addition, sun elevation was calculated in R using getSunlightPosition script. The biomass estimates do not differ significantly due to the use of different software. The R-script for biomass estimation has been developed during the last three years, and last year some flaws were corrected. Thus the biomass values shown in previous reports may differ slightly from the previous ones.

In 2023, euphausiids, also known as krill, were widely distributed in the western and central Barents Sea with higher abundance in the southwest (Figure 5.3.1.2). The biomass values in the upper 60 m are presented as grams (wet weight) per square meter (g/m²). In 2023, the night catches (mean 1.97 g/m²), were much lower than long term mean (7.3 g/m²).

Based on the euphausiid species identification in 2023, Meganyctiphanes norvegica and were mostly restricted to the Atlantic waters in the southwest, while Thysanoessa inermis were mainly observed in the central and northern areas. Two catches of Thysanoessa raschii were taken in the southwest and one in the Great Bank (Figure 5.3.1.3). The smaller T. longicaudata were not found in 2023.

The number of night stations in 2023 was 108, while the day stations was 177. During the night, a majority of the krill populations migrate to the upper water layer for feeding and are therefore more available for the trawl. In the southwest one catch of 865.5 kg (corrected for trawl capture efficiency) was extremely high and thus influenced estimates of the total biomass of krill in the Barents Sea in 2023. The calculated total biomass of krill was 10.7 million tonnes with this catch (indicated with stars in Figure 5.3.1.4) and 2.3 million tonnes without this catch.

Krill were captured at fewer number of trawl stations than in previous years, and especially east of Svalbard/Spitsbergen and in the southern Barents Sea, indicating possible high predation pressure from capelin and young herring respectively.

5.3.2   Distribution and biomass indices of pelagic amphipods (mainly Hyeriids)

Text by E. Eriksen, B. Husson, A. Dolgov, D. Prozorkevich and T. Prokhorova

Figures by B. Husson and S. Karlson

Estimation of pelagic amphipods biomass for the Barents Sea was performed in R (see above) and presented here for the period 2003-2023.

In 2023, amphipods generally occurred east off Svalbard/Spitsbergen and in the southwestern area (Figure 5.3.2.1).

In 2023, amphipods taken east of Svalbard/Spitsbergen were mostly represented by the Arctic species Themisto libellula, while amphipods taken in southwest were mostly represented by subarctic Themisto compressa and Themisto abyssorum (Figure 5.3.2.2). The cosmopolitan species Hyperia galba were found in both areas. Smaller T. compressa (with max measured length of 13.0 mm) and T. abyssorum (with max measured length of 15.0 mm) are less captured by the trawl than larger T. libellula (with max measured length of 35.0 mm).

In the southwest, at one station, where the krill catch of 865.5 kg was taken, extremely high catch of amphipods of 389 kg (corrected for trawl capture efficiency) was also taken. This catch will have an impact on the total amphipod biomass in the Barents Sea in 2023, similar to the krill estimates. The calculated total biomass of amphipods in 2023 in the upper 60 m was 15.7 thousand tonnes with this catch and 1.08 thousand tonnes without this catch (Figure 5.3.2.3).

Figures by: D. Prozorkevich

Area coverage and estimations

In 2023, the 0-group fish distribution was quite well covered by the survey (Figure 6.1).

Abundance and biomass estimates were calculated by different softwares during the last four decades: SAS (up to 2017), MatLab and R. The new 15 subareas, based on similar environmental status, was used from 2018 (Figure 6.2). They were included to get more detailed information about the distribution of the 0-group fish within the survey area. The abundance estimates do not differ significantly due to the use of different softwares. The R-script for abundance estimation has been developed during the last three years, and last year some mistakes in the calculations were corrected. Thus, the numbers and biomass shown in previous reports may slightly differ from the latest ones. Here, we present numbers of 0-group fish in million (10⁶), billion (10⁹) and trillion (10¹²).

Total biomass

Zero-group fish are important consumers of plankton and are prey for predators (adult fish, sea birds and marine mammals) and, therefore, are important for the transfer of energy between trophic levels in the ecosystem. Estimated total biomass of 0-group fish species (cod, haddock, herring, capelin, polar cod, and redfish) varied from a low of 165 thousand tonnes in 2001 to a peak of 3.3 million tonnes in 2023, with a long-term average of 1.1 million tonnes for the period 1993-2023 (Figure 6.3). The estimated total biomass of 3.3 million tonnes in 2023 was record high. In 2023 like in 2004 and 2022, 0-group fish biomass was dominated by herring, and biomasses were higher than the long-term mean (period 1980-2023) for all species, except for redfish.

6.1   Capelin (Mallotus villosus)

The highest average abundance was found in the Svalbard South (181 billion ind.), Great Bank (157 billion ind.), and Central Bank (139 billion ind.) polygons. The distribution of the 0-group capelin with little fish in the southeastern Barents Sea looks quite unusual compared to the long-term average (Figure 6.1.1). The lack of capelin in the southeast could be due to predation from the large number of juvenile herring in the area in 2023.

The 0-group capelin body length varied from 2.0 to 7.4 cm in 2023, while most of capelin (70%) were medium size with body length of 4.5-5.5 cm, which is similar to the length distribution in 2022. Larger individuals (with an average length above 5 cm) were found mainly in southeastern and northern areas, most likely indicating early spawning and drift to the rich feeding areas on the banks. The smallest capelin with average length close to 3 cm were found in the southwestern areas.

Two very strong year classes of capelin occurred in 2019 and 2020, followed by two below average year classes in 2021 and 2022, and now an above average year class in 2023. Estimated abundance of 0-group capelin has varied from 1 billion in 1993 to 1.8 trillion individuals in 2020 with a long-term average of 387 billion individuals for the 1980-2023 period (Figure 6.1.2). In 2023, the total 0-group capelin abundnace index (corrected for capture efficiency of the trawl) was 574 billion individuals which is above the long-term mean (Figure 6.1.2). The estimated biomass of 0-group capelin at 233 thousand tonnes was twice as high as the long-term mean. Therefore, the 2023 year-class of capelin seems to be middle-strong. 

6.2     Cod (Gadus morhua)

0-group cod were distributed widely in the BS, but the highest abundance was found in the southeastern (95 billion in Pechora) and north central (46 billion in Svalbard South) areas (Figure 6.2.1).

In 2023, 0-group cod were smaller than in 2022 and were dominated by fish of 5.0-7.4 cm length. The largest cod (with an average close to 8.0 cm) were observed in the northern polygons. Cod below 1.5 cm were found in the South West, Hopen Deep and Central Bank polygons.

Estimated abundance of 0-group cod varied from 276 million in 1980 to 464 billion individuals in 2014 with a long-term average of 116 billion individuals for the 1980-2023 period (Figure 6.2.2). In 2023, the total 0-group cod abundance index (corrected for capture efficiency) was twice high as the long term mean and was 231 billion individuals. Cod estimated biomass in 2023 (440 thousand tonnes) was highest since 2017. Therefore, the 2023 year-class of cod could be characterized as strong.

6.3    Haddock (Melanogrammus aeglefinus)

The 0-group haddock were found over a large area, with main abundance in the western areas – 15 billion in South West, and 10 billion in the Bear Island and in Thor Iversen Bank (Figure 6.3.1.).

In 2023, 0-group haddock were dominated by fish from 7.0 to 9.4 cm. The largest haddock (with average length > 10 cm) were observed in the Central Bank and Svalbard North polygons, while smaller haddock were found in the Pechora and Franz Victoria Trough (with an average length < 8 cm). A very small 0-group haddock (below 2 cm) were found central areas, indicating later spawning.

Estimated abundance of 0-group haddock varied from 75 million in 1981 to 91.6 billion individuals in 2005 with a long-term average of 12.9 billion individuals for the 1980-2023 period (Figure 6.3.2). 

In 2023, the total 0-group haddock abundance estimates (corrected for capture efficiency of trawl) were higher than the long term mean and was 50 billion individuals. Haddock 0-group biomass in 2023 was estimated to 367 thousand tonnes and was the highest since 2009. Thus, the 2023-year class may be characterized as very strong.

6.4    Herring (Clupea harengus)

0-group herring were widely distributed in the covered area, except in the eastern Barents Sea (Figure 6.4.1). The highest average abundance per station within a polygon was found in the Hopen Deep (2.3 trillion individuals). Relatively high abundance were also found in Svalbard South and Svalbard North and the Central Bank (with an average of 319-446 billion individuals).

The majority of 0-group herring (86%) had lengths in the range 4.5-6.5 cm, which is smaller than in 2022. Larger individuals were observed in Southeastern Basin with an average of 7.2 cm, while the smallest were found in the north central areas, where abundance was highest.

Estimated abundance of 0-group herring varied from 37 billion in 1982 to a record high 3.6 trillion individuals in 2023 (Figure 6.4.2). Estimated biomass of 0-group herring at close to 1.7 million tonnes was lower than in 2022 and almost four times higher than the long-term mean (411 thousand tonnes). Therefore, the 2023-year class of herring may be characterized as record strong. Half of the 0-group herring abundance was distributed north of Svalbard/Spitsbergen and therefore their survival during the first winter is highly unknown.

6.5    Polar cod (Boreogadus saida)

Polar cod 0-group were mainly found around Svalbard/Spitsbergen in 2023 which indicates that most of the spawning took place near this archipelago (Figure 6.5.1). The highest abundance was found in the Svalbard South polygon (with an average per station within the polygon of 2.4 billion individuals) and Great Bank polygon (with an average per station within the polygon of 3.6 billion individuals). A few polar cod were sampled in the southeastern Barents Sea, which indicated some spawning also there. For many years there was little or no spawning of polar cod in the Pechora area. 

The length of 0-group polar cod varied between 0.5 and 8.0 cm, with fish in the length range 3.5-5.9 cm dominating. Average length was 5.1 cm. Average length varied between polygons and larger fish were found in the North East polygon (average of 6.5 cm), and smaller fish in the Pechora polygon (average of 3.6 cm). 

Estimated abundance of 0-group polar cod varied from 201 million in 1995 to a record high 7.6 trillion in 2023 with a long-term average of 470 billion individuals for the 1980-2023 period. In 2023, the total abundance index for 0-group polar cod was the highest observed (Figure 6.5.2). 

In 2023, the estimated biomass of 0-group polar cod at 681 thousand tonnes was the second highest after 1994 and was more than four times higher than the long term mean of 147 thousand tonnes (1980-2023). For the first time since the observations started in 1980, the record strong year class originated mainly from the Svalbard/Spitsbegen sub-component. 

6.6    Saithe (Pollachius virens)

Saithe distribution and abundance varied a lot between years. In 2023, saithe were widely distributed, which is seldom observed (Figure 6.6.1). 

The largest saithe with an average of 11-12 cm were observed further north, while smaller fish (with an average of 8.6 cm) fish were found in the North East polygon. 

Saithe abundance indices varied from some few hundred (1980 and 2020) up to 1 million individuals in 2004.  During the last two years abundance of saithe were high and were 672 million (2022) and 342 million (2023), which are higher than in long term mean of 445 million individuals (Figure 6.6.1). 

6.7    Redfish (mostly Sebastes mentella)

In 2023, 0-group redfish was distributed from north of Norwegian coast to Svalbard/Spitsbergen and around the archipelago, which is similar to the 2022 distribution (Figure 6.7.1). The highest abundance was found in Svalbard North (67 billion ind.) and Svalbard South (26 billion ind.) polygons. The largest fish with an average of 4.5 cm were found in the north, while smallest with an average of 2-3 cm were found in the south.

Estimated abundance of 0-group deepwater redfish varied from 23 billion individuals in 2001 to 1.6 trillion ind. in 1985, and long-term abundance was 229 billion individuals for the 1980-2023 period (Figure 6.7.2). In 2023, the total abundance index for 0-group deepwater redfish was half of the long term mean and was 102 billion individuals. The total biomass was close to 31 thousand tonnes. Thus the 2022-year class may be characterized as weak. 

6.9    Greenland halibut (Reinhardtius hippoglossoides)

0-group Greenland halibut were found distributed around Svalbard/Spitsbergen in 2023, similar to the distribution in 2018-2022 (Figure 6.8.1). Highest abundance was found further north in Franz Victoria Trough polygon per square nautical miles.

An annual average length of 0-group Greenland halibut length was 6 cm than lower it in 2022 (7 cm). Fish length varied from 2.0 to 10 cm. The larger fish were found in Svalbard South with an average of 8 cm and smaller fish were found in the Franz Victoria Trough with an average of 5 cm. 

In 2023, the total abundance index for 0-group fish was 26 million individuals, that was lower than the last five years, and the long term mean of 30 million individuals. Estimated biomass was also lower than long term mean (of 80 tonnes) and was 35 tonnes. 

0-group Greenland halibut distributes widely in the North Atlantic and Svalbard/Spitsbergen fjords, therefore, abundance indices may not represent year classes strength, but give an indication of abundance in the Barents Sea. The 2022-year class may be characterized as weak but this is connected to high uncertainty due to the distribution pattern. 

6.9    Long rough dab (Hippoglossoides platessoides)

In 2023, 0-group long rough dab were widely distributed in the Barents Sea (Figure 6.9.1). The highest densities were found in North East (an average of 51 thousand per square nautical miles) and the Southeastern Basin (an average of 46 thousand individuals per square nautical miles). 

The annual average length for 0-group long rough dab was 3.5 cm and was larger than the previous seven years. Fish length varied from 1 cm to 5.0 cm and larger fish (> 4 cm) were found in Great Bank and Franz Victoria Trough, while smaller fish (2.0 cm) in Pechora and North East.

In 2023, the total abundance index for 0-group fish was 2.4 billion individuals that was the largest since 2019 (Figure 6.9.2). Estimated biomass was higher than long term mean (of 297 tonnes) and was 720 tonnes.

Thus the 2023-year class of long rough dab could be characterized as strong. 

Figures by S. Karlson, F. Rist, G. Skaret

7.1    Capelin (Mallotus villosus)

The coverage of the capelin distribution was synoptic and considered to be close to complete for 2023 (see Figure 7.1.1.1). A summary of the capelin stock assessment for 2023 is given in Advice on fishing opportunities for Barents Sea capelin in 2024 | Havforskningsinstituttet with more details provided in Barents Sea Capelin - Report of the Joint Russian-Norwegian Working Group on Arctic Fisheries (JRN-AFWG) 2023 | Havforskningsinstituttet (hi.no).

7.1.1    Geographical distribution

The geographical distribution of capelin recorded acoustically is shown in Figure 7.1.1.1. Similar to last year, the capelin was distributed far north. The main distribution area was the Great Bank, which is typical late in the feeding season. Significant recordings were also made north and west of Svalbard/Spitsbergen, which is very unusual. The capelin recordings stretched towards east and north-east, and the recordings suggested that the distribution stretched even further north on the eastern side. Some capelin were recorded in the south-east, but apart from that, very little capelin were recorded south of 73°N.

7.1.2    Abundance by size and age

A detailed summary of the acoustic stock estimate is given in Table 7.1.2.1, and the time series of abundance estimates is summarized in Table 7.1.2.2. A comparison between the estimates in 2023 and 2022 is given in Table 7.1.2.3 with the 2022 estimate shown on a shaded background. 

The total stock in the covered area was estimated to about 2.95 million tons, which is slightly above the long-term average level (2.79 million tons). About 44 % (1.29 million tons) of the 2023 stock had length above 14 cm and was therefore considered to be maturing. The 3-year-olds (2020 year-class) dominated the biomass of the capelin stock, and the biomass of 3-year-olds was the highest since 2012. The biomass of 4-year-olds was the highest since 1980. Average weight at age was low for the age groups 2-4. For 3-year-olds it was the lowest since 1975 (Figure 7.1.2.1 and Table 7.1.2.3). 

 Estimates based on Target strength (TS) Length (L) relationship: TS= 19.1 log (L) – 74.0

    Note:«+»  <0.005*10⁶ tons

7.2   Polar cod (Boreogadus saida)

7.2.1  Geographical distribution

The acoustic recordings of polar cod are shown in Figure 7.2.1.1. The concentrations east of the Great Bank dominated, but there were also significant recordings on the westside of the Great Bank and northwest of Kvitøya. A spot with high polar cod concentrations was also recorded near the Kara Strait. It is very likely that some of the polar cod were distributed further to the north and northeast outside of the survey area. Thus, the polar cod estimate must be considered an underestimate of the population.

7.2.2. Abundance estimation

The stock abundance estimates by age, number and weight in 2023 is given in Table 7.2.2.1 and the time series of abundance estimates are summarized in Table 7.2.2.2. The estimated means are from 1000 bootstrap replicas made in StoX 3.6.

The total estimated biomass of polar cod in 2023 is slightly below the long-term mean and less than 40% of the biomass estimated in 2021. All age groups from 1 to 4 were quite well represented in the population, with 1-year-olds being most abundant. 3-year-olds (2020 year-class) dominated in biomass, while there was a significant contribution in biomass also from 4-year-olds (2019-year class). The abundance of both these year classes were above the long-term average and they were observed as strong also in the 2021 survey. There was no polar cod estimation in 2022 due to poor survey coverage.

Estimates based on Target strength (TS) Length (L) relationship: TS= 21.8 log (L) – 72.7

* numbers partly based on VPA estimates 

** incomplete survey coverage

7.3    Herring (Clupea harengus)

7.3.1  Geographical distribution

The main distribution of young Norwegian spring spawning herring (NSSH) was in the south-east (Figure 7.3.1.1). In addition, there were concentrations of young herring in the Central Bank area and the south-west.

 7.3.2  Abundance estimation

The estimated total number and biomass of NSSH in the Barents Sea in the autumn 2023 is shown in Table 7.3.2.1, and the time series of abundance estimates is summarized in Table 7.3.2.2. Total numbers in 2023 was estimated at ca. 104·109 individuals (Table 7.3.2.1). This is four times above the long-term average (Table 7.3.2.2). Abundance of all age groups 1-4+ were above the long-term average. In particular, the 1 and 2-year-olds were abundant. 1-year-olds are dominating in abundance while 2-year-olds are dominating the biomass estimate (Table 7.3.2.1). The abundance of both 1-year-olds and 2-year-olds were the second highest on record. While the high abundance of 1-year-olds follows from a year of very high 0-group abundance in 2022, the high abundance of 2-year-olds and relatively high abundance of 3-year-olds was not expected from previous BESS surveys. However, it should be noted that last year the eastern area was covered late and not included in the estimate. 

Estimates based on Target strength (TS) Length (L) relationship: TS= 20.0 log (L) – 71.9