Barents Sea Capelin - Report of the Joint Russian-Norwegian Working Group on Arctic Fisheries (JRN-AFWG) 2024

1.1 - Barents Sea Capelin

The Joint Russian-Norwegian Arctic Fisheries Working Group (JRN-AFWG) met by correspondence 10-11 October 2024 to assess and give quota advice for the Barents Sea capelin stock.

Participants:

Bjarte Bogstad (Norway, Chair of meeting)

Anatoly Chetyrkin (Russia)

Stine Karlson (Norway)

Yury Kovalev (Russia)

Dmitry Prozorkevich (Russia)

Frøydis Rist (Norway)

Georg Skaret (Norway)

Alexey Stesko (Russia)

Sindre Vatnehol (Norway)

1.2 - Regulation of the Barents Sea Capelin Fishery

Since 1979, the Barents Sea capelin fishery has been regulated by a bilateral fishery management agreement between Russia (former USSR) and Norway. A TAC has been set separately for the winter fishery and for the autumn fishery. From 1999, no autumn fishery has taken place, except for a small Russian experimental fishery in some years and small by-catch in the northern shrimp fishery. A minimum landing size of 11 cm has been in force since 1979. Scientific advice is to carry out capelin fishery only on mature fish during the period from January to April.

1.3 - TAC and Catch Statistics (Table 10.1-10.2)

The Joint Norwegian- Russian Fishery Commission (JNRFC) set a TAC of 62 000 tonnes for 2023 and 196 000 tonnes for 2024. For both years, the quotas were in accordance with the advice. The international historical catch by country and season in the years 1965–2024 is given in Table 10.1. The Norwegian catch in 2024 was 117 555 tonnes which was 5 tonnes above the national TAC. Russian catches were 51 125 tonnes which was 27 325 tonnes below the national TAC.

The age-length distribution of Norwegian and Russian catches in 2024 are summarized in Table 10.2a-b. A summary of the capelin catch sampling and BESS capelin sampling used for abundance estimation in 2024 is summarised below:

1.4 - Stock assessment

1.4.1 - Acoustic stock size estimates in 2024 (Table 10.3, Figures 10.1-10.3)

The geographical survey coverage of the Barents Sea capelin stock during the BESS in 2024 was close to complete and with very good coverage of the main distribution area. The areas west of Svalbard and west of Frans Josef Land where small quantities of capelin were found last year, were not covered. The geographical distribution of capelin in 2024 is shown in Figure 10.1.

The stock estimate (made in StoX v 4.0) from the area covered by the 2024 survey was 0.887 million tonnes (Table 10.3). About 60% (0.534 million tonnes) of the estimated stock biomass consisted of maturing fish (>14.0 cm). The mean weight at age increased from the 2023 to the 2024 survey for ages 2-4 (Figure 10.2). Estimates of stock in number by age group and total biomass for the historical period are shown in Table 10.4. Survey mortality for ages 1-2 and 2-3 is shown in Figure 10.3.

A fixed sampling variance expressed as Coefficient of Variation (CV) of 0.2 for all age groups has previously been applied as input for CapTool for the forecast in the capelin assessment (Tjelmeland 2002; Gjøsæter et al. 2002). The survey design and estimation software now allow for estimation of a direct CV by age group. CV estimates by age group for the years 2004-2021 and 2023-2024 are given in Table 10.5. It was found that age groups with very low abundance in the survey usually have very high CVs. That is expected since there are few observations in the survey for such age groups. Vice versa an abundant age group normally has much lower CV. WKCAPELIN recommended to use the average CV for each age group from the last five years with high-quality surveys in the stock projection. However, including age groups with very low abundance and accordingly high CV in the averaging is inappropriate.

Because of incomplete survey coverage in 2022, the CVs of that year were not included in the averaging. Following the approach from last year, it was decided to use the unweighted average for the recent 5 years (2019-2021 and 2023-2024) for ages 1 and 2 and apply the value for age 2 for the ages 3-5 also, based on the similarity in estimated CV for ages 2-4 in 2024 and lack of information from previous years on CV at age 5. The summary results are presented below:

A methodology for handling very small or very large CV values and abundance estimates of different orders of magnitude in the averaging should be explored, together with exploring using annual CVs. With a low CV there is a risk that sampling variance is not a good reflection of total uncertainty, since other sources of uncertainty could then dominate over sampling variance in the total uncertainty.

1.4.2 - Benchmark results

An ICES benchmark meeting joint for the Iceland East Greenland Jan Mayen capelin and Barents Sea capelin (WKCAPELIN) was held in Reykjavik 21-25 November 2022 (ICES, 2023). A summary of the changes to the assessment method following the benchmark is given in the 2023 capelin assessment report (Bogstad et al. 2023).

1.4.3 - Reference points

A B_lim (SSB_lim) management approach has been suggested for this stock (Gjøsæter et al., 2002). In 2002, the JNRFC agreed to adopt a management strategy based on the rule that, with 95% probability, at least 200 000 tonnes of capelin should be allowed to spawn. Consequently, 200 000 tonnes was used as a B_lim. Alternative harvest control rules of 80, 85 and 90% probability of SSB > B_lim were suggested by JNRFC and evaluated by ICES (ICES 2016). ICES considers these rules not to be precautionary. At its 2016 meeting, JNRFC decided not to change the adopted management strategy.

The B_lim used up until present is based on SSB in 1989 (estimated to 96 000 tons) with an uncertainty buffer added (SSB + uncertainty buffer assumed to add up to 200 000 tonnes). The SSB in 1989 is the lowest in the time series which resulted in good recruitment.

In WKCAPELIN it was considered that B_lim should not be based on years which are affected by the NSS-herring collapse in the Barents Sea, as was the case for the year 1989. Among the included years, 1990 had the lowest estimated SSB (68 000 tonnes) that still produced an above average recruitment.

The procedure of including an uncertainty buffer to B_lim like it was done previously, was not accepted by WKCAPELIN. Separate terms for the biological reference point (B_lim) and the reference point used in the harvest control rule (B_escapement) were therefore introduced.

1.4.4 - Harvest control rule evaluation

Trochta et al. (2024) assessed harvest control rules for capelin in the Barents Sea using a management strategy evaluation (MSE), a modeling framework that simulates population and fishery responses to management actions. The form of the current escapement rule is retained and is defined by B_escapement, the biomass that must escape to spawn after fishing is accounted for. The MSE specifically tested four different B_escapement values (100 000, 150 000, 200 000 and 400 000 tonnes) with and without three alternative fixed minimum quotas (25 000, 50 000 or 75 000 tonnes). When assuming historical capelin productivity, accurate survey estimates and correctly estimated survey precision, all four B_escapement values without fixed minimum quotas maintained a low risk (<5%) of spawning biomass falling below B_lim. However, a B_escapement equal to 100 000 tonnes showed notably higher risk (of SSB<B_lim) if either the survey estimate is biased high or estimated survey precision is biased low. High probabilities of fishery closures resulted from B_escapement = 400 000 tonnes. All the alternative rules using fixed minimum quotas showed very high risk of SSB falling below B_lim and the model framework projected reduced future recruitment to the extent of stock collapse over the long term. In general, average catch decreased and the number of years with closed fishery increased with higher B_escapement. When selecting a rule, managers should also consider the trade-offs with other consequences and potential impacts on the ecosystem given the critical role played by capelin as the key forage fish for various predators in the Barents Sea.

1.4.5 - Comparison of historical capelin advice using different model configurations 

As part of the 2022 capelin benchmark, the configuration of the forecast model for Barents Sea capelin, Bifrost, was reviewed and updated. Vatnehol and Skaret (2024) compared the quota advice for the advice years 2005-2023 based on forecasts with the updated and original model configurations, using the existing harvest control rule. The results show that the catch advice in general would have been higher with the updated configuration, but the years with no-fishery-advice were the same with the updated and original configuration. The comparison further showed that the changes in parameter settings of the cod consumption module in addition to the parameters set for natural capelin mortality in the autumn (1 October to 1 January) had the greatest impact on the advice. It must be noted that the model configuration is partly adapted to the current ecosystem state, so the comparison between configurations becomes less relevant the further back in time we go. Furthermore, some parameters including the natural capelin mortality in the autumn and the proportion of immature cod in the Svalbard area will be updated each year as part of the capelin assessment, so a direct comparison with historical advice will change each year.

1.4.6 - Stock assessment in 2024 (Tables 10.4-10.5, Figures 10.4-10.5)

All projections described below were based on a maturation and predation model as described in the 2023 WKCAPELIN Benchmark report (ICES, 2023), with parameters estimated by the model Bifrost and data on predicted cod abundance and size at age in 2025 from the 2024 JRN-AFWG assessment (Howell et al. 2024). The methodology is described in the Benchmark report (ICES 2023).

With no catch, the estimated median spawning stock size on 1 April 2025 is 177 000 tonnes (90% confidence interval: 56-332 000 tonnes) (Fig 10.4), and the probabilities for the spawning stock to be above 150 000, 200 000 and 400 000 tonnes are 63, 40 and 1%, respectively. Summary plots for catch, stock size and recruitment are given in Figure 10.5.

This year’s headline advice is thus based on a B_escapement of 200 000 tonnes, as in previous years, but we also provide information about what the quota advice would be for B_escapement values of 150 000 tonnes and 400 000 tonnes, as these values were also found to be precautionary during the HCR evaluation. The catch options are given in the text table below.

Annual catch scenarios. P = probability. All weights are in tonnes.

Barents Sea capelin (ICES subareas 1 and 2, excluding Division 2.a west of 5°W). Annual catch scenarios. P = probability. All weights are in tonnes.

*TAC (2025) vs. TAC (2024).

**Advice (2025) vs. Advice (2024).

Recruitment

No 0-group estimate was yet available for the 2024 capelin assessment. The 1-group abundance in 2024 in the area covered by the survey was 58.6 billion which is much lower than the long-term average (Table 10.4).

High abundance of young herring (mainly age groups 1 and 2) has been suggested to be an important but not a single factor causing recruitment failure in the capelin stock (Hjermann et al., 2010; Gjøsæter et al. 2016). In 2023, high abundance of age 1-3 herring was observed during the BESS. Also, high abundance of age 2 herring was observed during the Russian 2024 young herring survey in April/May (ICES 2024). Preliminary results from BESS 2024 shows some areas with high acoustic herring recordings in the southern Barents Sea but no abundance estimates of herring in the Barents Sea for 2024 were available at the time of the 2024 capelin assessment.

1.5 - Further work

The time series of SSB should be updated annually following annual updates of cod assessment, and plots showing historic assessment values of SSB should be included in the report and advice sheet.

1.6 - References

Bogstad, B. et al. 2023. Barents Sea Capelin - Report of the Joint Russian-Norwegian Working Group on Arctic Fisheries (JRN-AFWG) 2023. IMR-PINRO Report Series 9-2023, 23 pp.

Gjøsæter, H., B. Bogstad, and S. Tjelmeland. 2002. Assessment methodology for Barents Sea capelin, Mallotus villosus (Müller). ICES Journal of Marine Science 59:1086-1095.

Hjermann, D. Ø., B. Bogstad, G. E. Dingsør, H. Gjøsæter, G. Ottersen, A. M. Eikeset, and N. C. Stenseth. 2010. Trophic interactions affecting a key ecosystem component: a multi-stage analysis of the recruitment of the Barents Sea capelin. Canadian Journal of Fisheries and Aquatic Sciences 67:1363-1375.

Howell, D. et al. 2024. Report of the Joint Russian-Norwegian Working Group on Arctic Fisheries (JRN-AFWG) 2024. IMR-PINRO Report Series 7-2024, 305 pp.

ICES. 2016. Report of the second Workshop on Management Plan Evaluation on Northeast Arctic cod and haddock and Barents Sea capelin, 25–28 January 2016, Kirkenes, Norway. ICES CM 2016/ACOM:47. 76 pp. https://doi.org/10.17895/ices.pub.5296.

ICES 2023. Benchmark workshop on capelin (WKCAPELIN). ICES Scientific Reports. 5:62. 282 pp. https://doi.org/10.17895/ices.pub.23260388

ICES. 2024. Working Group on Widely Distributed Stocks (WGWIDE). ICES Scientific Reports. 6:81. 913 pp. https://doi.org/10.17895/ices.pub.26993227

Tjelmeland, S. 2002. A model for the uncertainty around the yearly trawl-acoustic estimate of biomass of Barents Sea capelin, Mallotus villosus (Müller). ICES Journal of Marine Science 59:1072-1080.

Trochta, J., B. Bogstad, Y. Kovalev, D. Prozorkevich, G. Skaret, S. Vatnehol, and D. Howell. 2024. Report on evaluation of harvest rules for Barents Sea capelin in subareas 1 and 2 (Northeast Arctic), excluding Division 2.a west of 5°W. In press.

Vatnehol, S. and Skaret, G. 2024. Comparison of historical capelin quota advice using original and updated forecast model configuration. In press.

*Not adjusted for incomplete area coverage