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ICES advises on the basis of the EU management plan (Council Regulation No. 676/2007) that landings in 2013 should be no more than 14 000 tonnes. ICES notes that the advice is based on stage one of the plan. The implementation of stage two of the plan (as stipulated in article 5 of the EC regulation) is not yet defined.

In the coastal waters of southern Norway the fishermen distinguish between three different types of cod:—the “dyptorsk” living in deep water in the fjords and in the skjærgård, and especially outside the coastal banks, the “taretorsk” living in the shallow waters of the skj ærgård, and the “fjordtorsk” living in the shallow waters of the fjords and in narrow sounds. The characters used by the fishermen to separate the different types are colour and body proportions. These characters are, however, influenced by the environment and rate of growth. The different types may be phenotypes. But we must also take into consideration tha t genotypical factors may come into the problem. The possibility exists that the young of the deep-sea cod will seek the deep layers, and grow into a deep-sea cod. It is possible th a t the young of the littoral cod prefer the littoral region. That question cannot, however, be discussed on the basis of the material at hand. The investigations discussed here will show that the population of cod in the skj ærgård differs in several ways from the cod in the fjords, and that the population in one fjord differs from that in another. Material is too scanty for the deep-sea cod. This publication is part of Rapport et Proces-Verbaux des Reunions Vol. 136, which includes all contributions to a special scientific meeting on cod. To see all other articles in this volume, please click on the keyword "RPVR Vol. 136".

Sustainable use of marine waters has a high priority as part of international and national agendas. The quality of marine ecosystems reflects both the level of human pressures and natural environmental processes. Knowledge is key to making efficient policy recommendations regarding ecosystem management. In the past decade, the development of indicators has played an important role in enabling policy-makers to understand ecosystem changes while helping them make concrete recommendations towards improvement of their marine environments. Such indicators should describe the quality of the ecosystem, have strong scientific basis, and have the advantage of simplicity. This article presents the steps taken to develop ecological indicators for The Netherlands section of the North Sea. Among the current set of indicators used in The Netherlands, two are presented to illustrate how they are used in ecosystem management. Article from Marine Science Symposia Vol. 219 - "Hydrobiological variability in the ICES Area, 1990-1999", symposium held in Edinburgh, 8-10 August 2001. To access the remaining articles please click on the keyword "MSS Vol. 219".

20/01/2023: Table 1.1 - rounding error corrected. Figure 1.1 - figure legend corrected. Executive summary In 2018 the European Commission submitted a Special Request to ICES to investigate the contribution of Total Allowable Catches (TACs) to fisheries management and stock conservation for brill (27.3a47de), turbot (27.4), lemon sole (27.3a47d), witch (27.3a47d) and whiting (27.3a). ICES was requested to analyse the role of the Total Allowable Catch (TAC) instrument and to assess the risks of removing TACs in light of the requirement to ensure that the stock concerned remains within safe biological limits in the short and middle term. In 2022 the EU and UK submitted a new request to ICES to investigate whether conclusions from 2018 remain valid, and to update the advice if needed. The request concerns four stocks: brill (27.3a47de), turbot (27.4), lemon sole (27.3a47d) and witch (27.3a47d). It was agreed to answer the request by updating the answers to a series of six questions addressed in the 2018 request. The six questions were as follows: Was the TAC restrictive in the past? Is there a targeted fishery for the stock or are the species mainly discarded? Is the stock of large economic importance or are the species of high value? How are the most important fisheries for the stock managed? What are the fishing effort and stock trends over time? What maximum effort of the main fleets can be expected under management based on FMSY (ranges) for the target stocks, and has the stock experienced similar levels of fishing effort before? This report describes the analysis for brill, turbot, witch flounder and lemon sole first covering each of the above questions, then providing concluding sections.

The application of the results of acoustic surveys to stock assessment is examined for herring (Clupea harengus L.) in the northern North Sea. Surveys designed to estimate spawning biomass have been carried out under ICES coordination in July each year since 1979. The results are reported annually in the form of estimated numbers-at-age and biomass in statistical rectangles. Total mortality estimates derived from the survey results are higher than those estimated by virtual population analysis (VPA). The reasons for this are explored by simulation techniques in which the relationship between target strength and length and the age-sampling procedure are varied. These indicate that the precision of the acoustic survey itself (as distinct from target-strength values and age sampling) dominates the random errors. It is not, however, clear whether the discrepancy between mortality estimates is due to a bias in the sampling for length compositions by trawl, or to inaccuracies in the VPA estimates. A compari­son with other techniques (VPA and estimates of stock size derived from herring larvae surveys) indicates that the acoustic surveys are providing similar indications of changes in abundance. Acoustic surveys, moreover, are providing absolute estimates of stock size within about 30% of the estimates obtained from VPA.

The ICES Multi-species Assessment Working Group (MAWG) last met in 1997 (ICES 1997a) because it was thought that there was no need for routine multi-species stock assessment and subsequent advice on management issues. Nevertheless, it is widely recognized that the development of viable long-term management strategies depends on a good understanding of species and fleet interactions, and requests for advice reflect the continued interest in this field. This workshop will produce primarily an updated key run of the North Sea MSVPA (Multi-Species Virtual Population Analysis) and identify the future direction of multi-species work in the context of the North Sea. This is necessary if ICES is to maintain the capability to give multi-species advice. A number of developmental extensions have previously been identified for MSVPA (see, for example, ICES 2001c) but it is necessary to define a feasible and focussed programme of research.

Stock specific documentation of standard assessment procedures used by ICES. Stock: Plaice in 4 and 3a20 Working Group: Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK) Last updated: April 2023 Last updated by: Chun Chen

ICES has reviewed the format of advice for ple.27.7d, ple.27.7e, and ple.27.420 stocks in relation to providing consistency of approach. ICES advises that from 2023 the headline advice for the three stocks will be stock-based advice. This implies that the advice for the ple.27.420 stock will include catches of the stock that are taken in Division 7.d. Additionally, changes to the catch scenario tables of the three stocks will be made to clarify the amount of plaice in Division 7.d that originates from the North Sea and western English Channel respectively. As ICES provides stock-based advice in the headline advice, details of the implied area-based projected catches will be given in the catch scenarios sections.

ICES advises that when the precautionary approach is applied, there should be zero catches in each of the years 2024, 2025, 2026, and 2027. Closed areas to protect spawning should be maintained.

Stock specific documentation of standard assessment procedures used by ICES. Stock: Sole (Solea solea) in Division 7.d (eastern English Channel) Working Group: Working Group on the Assessment of Demersal Stocks in the North Sea and Skagerrak (WGNSSK) Last date when the stock was updated: June 2022 Revised by: Lies Vansteenbrugge Timeline of revisions: May 2011, February 2017, October 2019, February 2021 Main modifications: Adapted stock annex as a result of the IBP 2022 Last Benchmarked: February 2021 (WKNSEA 2021), IBP June 2022 Last update: June 2023

Description not yet available.

The Working Group on Crangon Fisheries and Life History (WGCRAN) works on studying the population dynamics of the brown shrimp Crangon crangon and factors influencing the stock as well the individual species. A central goal of the group is to provide a biological basis for advice and to identify ways for sustainable management. A main outcome of the 2022 meeting was the standardization of the compilation of commercial data, i.e. the creation of a common workflow for uniform (inter-) national data retrieval. On this basis, total brown shrimp landings, fishing effort and landings per unit effort were discussed. For the first time, biological stock status indicators, i.e. brown shrimp swept area biomass, annual mortality, and fraction of large shrimp were calculated both with and without incorporating Belgian scientific survey data. For the swept-area biomass, the addition of Belgian data had limited influence. The meeting finally discussed the status of the international bycatch sampling programmes under the de minimis exemption from the landing obligation. For future common analysis supporting policy decisions, a data format was established for compiling the data collected by each country.

Please note: The present advice replaces the advice given in June 2022 for catches in 2023, 2024 and 2025. ICES advises that when the MSY approach is applied, catches in each of the years 2023, 2024 and 2025 should be no more than 28 238[1] tonnes. If discard rates do not change from the average of the last three years (2019–2021), this implies landings of no more than 2824 tonnes.

ICES has evaluated a 12-month TAC with a TAC-year of 1 July–30 June for northern shrimp in divisions 3.a and 4.a East. During this evaluation, the model year was shifted to start on 1 July, and numerous harvest control rules (HCRs) with different combinations of MSY Btrigger and Ftarget were assessed. ICES advises that a new 12-month TAC with a TAC-year of 1 July–30 June can be considered appropriate for the management of fisheries on this stock, subject to the amendment of the MSY Btrigger value. It was found that the current HCR for this stock, Ftarget = FB30% (i.e. the F that brings the stock to 30% of an unfished biomass B0) and MSY Btrigger = 80% x B30, no longer meets the criteria of the long-term management strategy, as it has a greater than 5% probability of the spawning-stock biomass (SSB) falling below Blim in several years of the simulated period. An alternative HCR with MSY Btrigger set at 90% x B30 was found to meet all three criteria of the long-term management strategy. The proposed HCR results in the median long-term yield being 97% of the deterministic maximum sustainable yield, and Ftarget remains at FB30%. Two additional TAC-year options were requested by EU/Norway (starting in April and May, respectively). However, as agreed by all parties, these options were not evaluated by ICES. The banking and borrowing aspect of the request requires further methodology development and will be conducted by ICES in Q3 of 2023.

The cod population of the Oslofjord. This publication is part of Rapport et Proces-Verbaux des Reunions Vol. 136, which includes all contributions to a special scientific meeting on cod. To see all other articles in this volume, please click on the keyword "RPVR Vol. 136".

Sole in Division IIIa and Subdivision 22-24 (Skagerrak, Kattegat and the Belts); advice for 2011

The contributions to the Special Scientific Meeting “THE COD” which are submitted herewith show that, during the 20 years that have passed since our last meeting dealing with the cod, very great attention has been paid to a census of the cod stocks. The long series of observations recording length and age compositions of the cod constitute very valuable material, and new facts of paramount importance have been presented. Our plan of arranging all the contributions within a particular frame work may have prevented some interesting observations from appearing, but it has enabled us to present data for a direct comparison of the different stocks examined by various workers. This publication is part of Rapport et Proces-Verbaux des Reunions Vol. 136, which includes all contributions to a special scientific meeting on cod. To see all other articles in this volume, please click on the keyword "RPVR Vol. 136".

Note on version 2: the original WKBCOD report published in April 2023 had some errors since the description of the final model in the report was mistakenly based on an intermediate model fit. Corrections were made to the executive summary and section 13.2 on June 12 2023. All updated text, values, and figures are indicated with footnotes. The North Sea cod stock was last benchmarked in 2021 including a workshop on Stock Identification of North Sea Cod (WKNSCodID) reviewing the population structure information on the cod in the North Sea and adjacent waters. The workshop concluded that the North Sea includes different stock components of Viking and Dogger cod, and that the Dogger cod population extends to the West of Scotland (6.a.N). However, it was not possible to develop spatial approaches in time for the benchmark in 2021 because of (1) unexplained discrepancies between spatially disaggregated data and the data as used in the current North Sea assessment; and (2) the constraint that the 6.a stock was not included in the benchmark process. Nevertheless, the North Sea cod assessment was improved by revising the survey indices, biological data, and SAM assessment model configuration, thus lessening the data and assessment issues that had triggered the benchmark process. ICES recommended that further work be conducted on a data call to consider the different stock components as well as inclusion of the West of Scotland cod stock in the evaluation. This stock was last benchmarked in 2020 at WKDEM (ICES, 2020). Several pre-data meetings were conducted with the data providers to ensure that the data asked for in the data call met the requirement of the stock assessors, and were realistic to provide for the relevant countries. The data set on landings for the substocks components covering 1995–2021 were evaluated at the data evaluation meeting and was found appropriate to use for the assessment. Presently the North Sea cod time series starts in 1963 and it would therefore be beneficial if the landings by substock could be extended further back in time. For the landings data covering the time period 1963–1995, ICES has a historic database with information on annual cod landings by area. It was decided to investigate if these data could be converted into landings by substock with some country specific assumptions. Also, recreational data were requested in the data call. However, very different quality levels for these data, with many missing years, were submitted by countries; therefore, it was decided that it is currently not possible to incorporate recreational data in the analytic stock assessment. It was concluded that catch level could, as in previous years, be given as a supplementary information in the WGNSSK report. A workshop on including recreational catches in stock assessment has been planned for in April 2023. As the substocks are considered mixed in Q3-4, a combined index for the whole area was evaluated during the data evaluation meeting. It was decided to combine the survey data for Q3 and Q4 to ensure a full stock area coverage. As the substocks are considered separate in Q1, it was decided to split the Q1 indices based on the assumption that all fish observed during the Q1 surveys can be allocated to substocks based on where they were found. Given mixing is assumed to occur during Q3 and Q4, the decision was made to let the Q3+4 index remain aggregated and representative of the total stock. To allow testing with as many ages as possible in SAM, it was agreed to prepare indices with a 7+ group for the benchmark meeting. A multi-stock (SAM) model was developed to take into account the substock structure in Northern Self cod stocks. This new model is estimated using substock Q1 survey indices and information about substock fishery catch compositions, as well as catch and survey indices that are only available as a sum for the substocks. For example, yearly catch-at-age data from the North Sea is only available as a sum of the catch of the Southern, Northwestern, and Viking stocks. Furthermore, the model can include genotype data to estimate stock- or catch-compositions. The benchmark meeting decided to use the BioPar option in the multi-stock (SAM) model for maturity, stock weights, and natural mortality. Three options were explored to address data deficiencies for maturities derived from Q1 surveys prior to 1990. New procedures were used to calculate catch and stock weights-at-age. The stochastic multi-species model SMS estimates of natural mortality rates were used for the three substocks assessed. Many configurations and sensitivity analyses of the multi-stock model were reviewed during the benchmark meeting. In the final preferred model formulation, stock dynamics were modelled from 1983 onwards. The substock model could not be reliably extended prior to 1983 because of a lack of substock information about landings. Another motivation for truncating the assessment time-series was that there were no maturity estimates prior to 1983 to derive SSB. These values had to be assumed. Hence, the meeting concluded that the assessment model time-period should be constrained to 1983-present. However, the full landings time-series from 1963 onwards still provides some historic perspective on the size of the total stock during 1963–1982. Estimates from the preferred model indicated that the Southern stock SSB decline steadily from around 21 600 tonnes in 1983 to 2700 in 2020, followed by a small increase in both 2021 and 2022. The northwestern stock was the largest component; during 1983 to 1997 its SSB fluctuated around 49 500 tonnes, followed by a large decline to 14 700 in 2005 and a generally increasing trend since then, except for 2017–2020. Throughout the period, the Viking stock SSB fluctuated around 14 000 tonnes[1]. Single combined-stock SAM models were also investigated during the benchmark meeting. Their results were very consistent with the multi-stock model results when combined for the three substocks, but the residual diagnostics were problematic for the single-stock SAM, and the retrospective pattern was at best borderline acceptable. The benchmark concluded that the multi-stock model was better suited to support the intended management options for northern shelf cod. There is evidence from the literature of three recruitment periods or productivity regimes for cod in the North Sea: before 1988, between 1988 and 1998, and after 1998. The benchmark meeting consensus from the multi-stock model results was that all three substocks had higher recruitment rates (i.e., recruits per spawner) prior to 1997; that is, there were two recruitment regimes since 1983. Hence, the benchmark meeting consensus was that reference points should be based on the stock-recruit times-series since 1997, the last three years for selectivity, and the last 5 or 10 years for other biological parameters. However, agreement to split the stock-recruit time-series was not unanimous, and an alternative perspective is documented in this report. The meeting report documents a minority statement from Swedish participants. They did not agree with the setting of the Btrigger reference points, which they suggested were too low and should have been set at 50% of BMSY, at a minimum. The benchmark process provided many research recommendations dealing with these topics: 1) catch sampling programs that take the new cod substock structure into account, 2) improved genetic sampling information for the substocks, 3) M information for each substock, 4) substock specific landings fractions and catch weights-at-age, 5) further simulation testing of the multi-stock model, 6) fecundity information for the substocks. [1] The values in this paragraph were corrected in version 2 of the WKBCOD report.

ICES advises that when the MSY approach is applied, catches in each of the years 2023, 2024 and 2025 should be no more than 29 249 tonnes. If discard rates do not change from the average of the last three years (2019–2021), this implies landings of no more than 3074 tonnes.

ICES advises on the basis of precautionary considerations that landings should be no more than 26 000 t (human consumption for the combined area) in 2013. Management for Division VIId should be separated from the rest of Subarea VII.

Horse mackerel (Trachurus trachurus) in Divisions IIa, IVa, Vb, VIa, VIIa-c, e-k, VIIIa-e (Western stock)

Experiments were carried out with juvenile Atlantic cod, Gadus morhua, in order to examine the impact of natural fluctuations in oxygen saturation on metabolism and growth. Three different oxygen scenarios, recorded during summer and autumn in the shallow waters of Kiel Bay, were applied in 28 day lasting experiments (minimum 45%, maximum 90% oxygen saturation). Two groups of seven fish were exposed to each scenario, two more groups were kept at normoxic conditions. A direct dependence of food intake on oxygen saturation was revealed. However, the specific growth rate, Fulton´s condition factor, the hepatosomatic index as well as the water content of white muscle showed no significant differences between treatments. Starving periods, induced by hypoxic conditions, were compensated by an enhanced food intake as soon as the oxygen saturation exceeded a critical value, which was determined at around 60% saturation. Furthermore, there were indications for compensatory growth in individual fish. At the end of the experiments the activity of the glycolytic enzyme lactate dehydrogenase (LDH) was measured. A significant correlation between growth rate and LDH-activity as well as a size- and condition-dependence of the enzyme activity was determined.

Based on the most recent estimate of SSB (in 2009) and fishing mortality (in 2008), ICES classifies the stock as suffering reduced reproductive capacity and as being at risk of being harvested unsustainably. SSB has increased since its historical low in 2006, but remains below Blim. Fishing mortality declined after 2000, but in 2008 increased, predominantly as a consequence of increased discarding and is currently estimated to be between Flim and Fpa. The 2005 year class is estimated to be one of the most abundant amongst the recent below-average year classes. The 2008 year class is estimated to be one of the lowest in the series.

Appendix F of Rapports et Proces-Verbaux des Reunions Vol. 3. If, in response to the invitation of the Bureau of the International Council for the study of the sea I give here some observations on the periodic occurrence of the principal fishes, based on the rich statistical material of the “Deutsche Seefischerei Verein”, I am nevertheless well-aware, that in so doing, I am raising an old and a difficult problem. It has been well-known for long, that most of the fisheries are carried on at certain periods and that the existence of such periods is almost always conditioned by the habits of the fishes. If the fish occur in quantities worth catching, the fishermen as a rule are soon on the spot and do not move until the catches no longer repay the costs of the time and labour. Thus arises a fishery-period

ICES advises that when the precautionary approach is applied, catches of the Division 7.e plaice stock in 2017 should be nomore than 2714 tonnes. If this stock is not under the EU landing obligation in 2017 and discard rates do not change from therecent average (2014–2015), this implies landings of the Division 7.e plaice stock of no more than 1391 tonnes.Assuming the same proportion of the Division 7.e plaice stock is taken in Division 7.d as during 2006–2015, this willcorrespond to catches of plaice in Division 7.e of no more than 2454 tonnes. If this stock is not under the EU landingobligation and discard rates do not change from the average (2014–2015), this implies landings of plaice in Division 7.e of nomore than 1258 tonnes.

The ICES workshop on the analysis of the benchmark of cod in Subarea IV (North Sea), Division VIId (Eastern Channel) and Division IIIa (Skagerrak), WKCOD, met at the ICES headquarters (Copenhagen) during February 7–9, 2011. There were 19 participants from seven countries (Belgium, Denmark, Germany, Iceland, Norway, Spain, and UK), of which three participants were industry representatives and one was an external reviewer. The meeting was chaired by Einar Hjorleifsson (Iceland). The meeting was designed to serve as an inter-benchmark protocol for the North Sea cod assessment and was tasked with reviewing the input data used and the assess-ment model and settings, proposing changes to them if deemed appropriate. Additional work, if required, was also to be identified. A consensus of the data input, model assumptions and framework to be used in the 2011 cod assessment was reached at the WKCOD meeting. The conflict in the IBTS quarter 1 vs. quarter 3 surveys, an issue raised by the WGNSSK in 2010, was not fully resolved. The abundance indices in the quarter 1 survey were considered to more likely reflect stock trends in recent years, because of suspected changes in catchability in the quarter 3 survey in relation to recent changes in the spatial distribution of fish in the latter part of the year. It is recommended that further investigation be ad-dressed within a working group on improving use of survey data for assessment and advice (suggested ToRs are in WKCOD report). Additionally, using both surveys in the assessment results in trends in unallocated removals that go against the prevail-ing hypothesis that the bias in landings in particular and potentially in discards esti-mates in recent years have declined compared with the earlier period. For these reasons it was agreed to use only the quarter 1 survey in the assessment for the time being. The current assessment model (B-ADAPT) was considered to be too responsive to the noise levels in the surveys in recent years to form the basis for providing advice to a management regime which is based on the final year estimates of fishing mortality. An alternative model, SAM, which smoothes fishing mortality was adopted as the basis for an interim period (~two years) of assessments because of the more stable estimates of fishing mortality. The SAM model is considered an interim solution be-cause it estimates bias in the total catch in the same way as the previous assessment model, whereas a model that estimates bias in landings and discards separately is considered a more suitable long-term solution. Although the SAM model structure agreed at WKCOD is considered the most ap-propriate that could be fitted in the time available, a refined model structure will only be completed with further work. Consequently, WKCOD consider that if further re-finements are found to be required before the WGNSSK 2011 meeting, these be presented to that meeting for adoption (WGNSSK comprises a large part of WKCOD participants). In the medium term WKCOD considered that the development of a model structure that models discard and landings separately is required due to the differing levels of noise associated with each data set. WKCOD recommended that the reference points are not revised in the short term until the assessment model has been finalised. It was concluded that the factors for ”unallocated mortality” estimated for North Sea cod were in agreement with the general perception of the extent of underreporting except for the most recent years. However, it was also recognized that ”unallocated mortality” in general is a result of discrepancies between model assumptions and observations. Alternative model assumptions, such as changes in natural mortality or survey catchability, might also explain the patterns observed.

This report provides the technical basis to support the ICES response to the EU-Norway request to ICES on a long-term management strategy for Pandalus in Skagerrak and the Norwegian Deep. The report was prepared by correspondence by a group of scientists who are members of the Joint NAFO/ICES Pandalus Assessment Working Group (NIPAG), led by Carmen Fernández (not a NIPAG member). Two external sci-entists have reviewed the work. A Management Strategy Evaluation (MSE) was developed to investigate via simulation the performance of different harvest control rules (HCR), which would be applied to the results of a stock assessment conducted in March of a given year. The catch given by the HCR would apply to the same year (January–December), and a preliminary TAC for the following year should be provided at the same time. The request indicates that, alternatively, the TAC year could go from May 1 of the assessment year to April 30 of the following year. Both TAC year options were examined in the evaluation, without detecting any significant difference in performance metrics (risk of low stock bio-mass, yield, interannual yield variability). For providing catch advice, a January–December TAC year seems more natural, because ICES calculates the spawning–stock biomass (SSB) for this stock as corresponding to January 1, and the trigger point of the HCR is defined as the SSB at the start of the TAC year. The preliminary TAC for the following year could then be based on a catch forecast, using the same HCR, for the first two quarters of that year. The Operating Model for the MSE was based on the latest available assessment from March (March 2017). Given the reduction in recruitment observed in the last decade, Historic and Low (based on the last ten years) recruitment scenarios were considered in the evaluation. The consequences of selecting an HCR based on a particular scenario when future recruitment follows the other scenario were examined, and risk-yield trade-offs were found. Uncertainty / error in the assessment and short-term forecast was analysed retrospectively and error parameters obtained from that analysis were included in the MSE. The HCRs evaluated consist of (Ftarget, Btrigger) combinations. The catch corresponds to the Ftarget fishing mortality; if the SSB at the start of the TAC year is estimated to be below Btrigger, then the Ftarget is linearly reduced to zero. A clause in the HCR (paragraph 3) sets the overriding constraint that there should be no more than 5% probability of the SSB falling below Blim at the beginning of the following TAC year. Paragraph 3 posed considerable implementation difficulties and could not be implemented exactly. Therefore, the HCRs evaluated either did not include paragraph 3, or included para-graph 3 implemented in an approximate form by requiring that the SSB from a deter-ministic forecast should be at or above Bpa at the beginning of the following TAC year. The technical aspects of this implementation were not straightforward and results for HCRs including paragraph 3 should be regarded as approximate. The report presents detailed results for HCRs with Btrigger=MSY Btrigger=9900 t, as well as for HCRs that consider multiple (Ftarget, Btrigger) combinations. As requested, the (Ftarget, Btrigger) combination that maximises long-term yield (median value) while resulting in no more than 5% probability of the SSB falling below Blim in any 20-year period was identified. Assuming Historic recruitment, this combination is (0.48, 13 000 t) or (0.48, 12 000 t), depending on whether the HCR excludes or includes paragraph 3. If, on the other hand, Low recruitment is assumed in the evaluation, this combination is (0.36, 12 000 t) or (0.37, 11 000 t), depending on whether the HCR ex-cludes or includes paragraph 3. The peformance of the HCRs excluding or including paragraph 3 is similar. The requirement in the request that there should be no more than 5% probability of the SSB falling below Blim in any 20-year period is more stringent than the ICES standard criterion to consider an HCR as precautionary, which is that there should be no more than 5% probability of the SSB falling below Blim in any year. If HCRs are selected based on maximising the median long-term yield while achieving a risk at or below 5%, then applying the 20-year-based risk criterion leads to HCRs that, in the long term, result in a higher median SSB (roughly of the order of 25%–35% higher) and lower median yield (roughly of the order of 5%–15% lower) than if the ICES standard risk criterion was applied. Some scenarios of interannual quota flexibility of +/-10% were evaluated, and resulted in a small increase of the probability of SSB falling below Blim. In this case, some reduc-tion (of the order of 5% reduction) in the Ftarget is necessary in order not to exceed the 5% risk level. As requested separately to the group, FMSY ranges were calculated following the stand-ard ICES procedure and are included in the report. It should be noted that the standard ICES risk definition was used in this calculation.

Advice Summary for 2011-2012

In the absence of agreed reference points, the state of the stock cannot be evaluated. SSB has been stable in recent years but is expected to decline rapidly due to poor recruitment. Fishing mortality has been stable and is estimated at 0.37, well above the candidate for Fmsy. From 2004 onwards, recruitment has been declining and is now at a record-low.

In the OSPAR area, the degree of interactions may be moderate between finfish mariculture and wild fish populations at the scale of a river local to a salmon farm, but are lower at a broader scale. The supply of food for mariculture creates a demand for small pelagic fish. ICES has advised that the fishing mortality on some small pelagic stocks should be reduced. A risk assessment is presented that identifies the research needed to more fully understand the nature and impact of these interactions and pressures.

Based on the most recent estimates of SSB (in 2009) and, fishing mortality (in 2008), ICES classifies the stock as having full reproductive capacity and being harvested sustainably (F=0.29). Year classes 2005-2008 are among the lowest observed. Due to recent low recruitment, SSB has declined from its historical peak in 2003-2004 of more than 7 million tonnes to 3.6 million tonnes at the beginning of 2009, and the decline is expected to continue in the short-term.

For a period of more than 10 years, two basic eutrophication indicators, dissolved inorganic macronutrients and chlorophyll a, have been measured along with physical parameters at a permanent coastal station in the northern German Wadden Sea near Büsum. despite distinctly reduced phosphorus inputs, the data have not revealed any long-term trend in nutrient winter concentrations or algal biomass compared to other available time-series in the area of investigation, i.e. River Elbe nutrient loads and nutrient concentrations in the German Bight near Helgoland. Instead, there are indices of slightly higher winter phosphate concentrations in recent years as well as a decrease in maximum annual N:P ratios due to elevated residual phosphate concentra­tions in spring. This is in contrast to the situation in the adjacent German Bight, where a declining trend in dissolved inorganic phosphate concentrations is observed. It is suggested that persistent high phosphate concentrations in the northern German Wadden Sea result from local sources of phosphate such as remobilization from the sediments, as well as remineralization of imported organic matter. The comparison with a comprehensive assessment of seasonal light and nutrient availability in the water column indicates that on an annual basis, phytoplankton biomass development in the northern German Wadden Sea is still insensitive to current nutrient reduction measures because of the predominant role of light limitation in this turbid environment. Article from Marine Science Symposia Vol. 219 - "Hydrobiological variability in the ICES Area, 1990-1999", symposium held in Edinburgh, 8-10 August 2001. To access the remaining articles please click on the keyword "MSS Vol. 219".

Open letter to the Bureau of the Central Committee for International Marine Research on seal ecology, fishing and status in the North Sea. This publication is part of Rapport et Proces-Verbaux des Reunions Vol. 8. To see all other articles in this volume, please click on the keyword "RPVR Vol. 8". Publication in German.

The list of authors and the volume/issue numbers were updated in February 2023. A benchmark process was conducted for six stocks in the North Sea and Celtic Sea area with the goal of determining appropriate data inputs for assessing status, estimation of reference points, and short-term projection which could form the basis of advice for fishing prospects. The benchmark process consisted of two meetings separated by about three months: the first was a data inputs review and the second was a model assumptions and outputs review. Benchmarked evaluation methods were produced for: 1) North Sea, Skagerrak, Malin Shelf Haddock (had.27.46a20) 2) Irish Sea cod (cod.27.7a) 3) North Sea plaice (ple.27.4) 4) Celtic Sea plaice (ple.27.7fg) 5) North of Scotland herring (her.6aN) 6) North of Ireland, West of Scotland herring (her.6aS7bc) North Sea Haddock is a category 1 assessment using the standard ICES Stock Assessment Model (SAM): The previous model for this stock was replaced by SAM in this benchmark primarily because the originator of the previous model is about to retire and a SAM approach is better under-stood by a wider swath of the ICES community presently. Furthermore, because the old model is incompatible with MS-Windows 12 and it will not be updated, it was deemed desirebale to switch to a SAM assessment. The SAM model fitting for this stock showed good fitting diag-nostics and the approach was easily accepted as the benchmarked approach. Haddock are notiously sporadic recruiters and this makes the choice of stock-recruit relationship for deter-mining the reference points difficult but this is well know feature of this stock and other had-dock stocks and did not preclude the estimation of reference points. Irish Sea cod was assessed as a category 1 stock that used the Stock-Synthesis 3 model ap-proach: Irish sea cod was previously classified as a category 3 stock. It was proposed as a category 1 assessment for the present benchmark and used the highly adaptable stock-synthetis modelling approach. The main issues for this assessment are less about the model approach than about data and a stock structure. The stock has not experienced many commercial fishery removals for a number of years while a recreational fishery along the English coast has been roughly quantified. The productivity dynamics of the stock seem largely extrinsically driven (i.e. spawner biomass influence on recruitment is the not the primary determinant of stock growth presently), at least during the current low stock size period. A post benchmark process to de-termine an ecological/climate conditioned sustainable fishing mortality (which has become termed Feco) was consquently calculated for this stock. The next benchmark for this stock should consider recreational catches from across the stock area and should revisit the definition of what area and data constitute information pertinent for this stock. North Sea plaice is a category 1 assessment using SAM: This assessment combined survey indices to cover the whole stock area well. Age dependent natural mortality was implemented based on literature methods of producing mortality estimates for species with plaice life history. The model fittings with time variying and invariante M produced similar fitting diagnostics however. Discarding rates of plaice from this stock has historically been important and assumptions about discarding have important impact on the estimates of the reference points. Celtic Sea plaice is a category 1 assessment using SAM: There were considerable difficulties fitting SAM to the data for this stock. The accepted bench-mark model was subsequently rejected owing to poor fit diagnostics and an ICES category 3 methods was proposed as the way forward for producting advice. Herring North and West of Scotland and Herring in Northwest of Ireland and West of Scotland were assessed using a category 3, method 2.2 CHR rule: Early in the data meeting it was decided to split these into two stocks as genetic, survey and migratory evidence suggests that there are at least two major components in this stock complex. A category 1 SAM assessment was attempted for the North of Scotland stock but it was too sensitive to the inclusion of particular survey indices combined with lack of strong justification for choosing particular survey series over others. Therefore the a category 1 SAM approach was rejected in favour of the ICES category 3 CHR rule which is based on life history an opti-mal length. The M/k ratio (natural mortality M and von Bertalanffy growth parameter k) de-fault of 1.5 for the method was modified to reflect actual values calculated from the data. This method adjusts catch in the recent period up or down depending on the state of the stock im-plied by the methods. Uncertainties remain in how split catch and survey data between this stock and the herring from western Scotland and Ireland and this will warrant future work.

This report describes the combined ex post and ex ante evaluation of the multiannual plan for sole and plaice in the North Sea as laid out in Council Regulation (EC) No 676/2007. It extends previous reports by IMARES (C114/09, C104/10). This plan has been in place since 2007. The plan aims to ensure, in its first stage, that stocks of plaice and sole in the North Sea are brought within safe biological limits, i.e. above Bpa and below Fpa. Following this, and after due consideration by the Council on the implementation methods for doing so, the plan will ensure that the stocks are exploited on the basis of maximum sustainable yield and under sustainable economic, environmental and social conditions. This report extends work previously carried out by Wageningen IMARES evaluating the multiannual plan for plaice and sole in the North Sea as described in Council Regulation EC 676/2007 (Machiels et al. 2008). That evaluation has been redesigned to take into account comments and criticisms highlighted by two ICES reviewers. The ex ante evaluation of the plan includes an examination of its implementation, and the stock and fleet dynamics in relation to the measures and objectives of the plan. The stock dynamics were evaluated using two different stock assessment models: an XSA model and a statistical catch at age (SCA) model. Changes in fleet dynamics were evaluated in terms of overall fishing effort and number of vessels in the Dutch beam trawl and otter trawl fleets. The regulations in the Council Regulation have been used as the basis for establishing TACs for North Sea plaice and sole for the last two years. However, the actual implementation of these regulations has required a degree of interpretation by those implementing them. The regulations by themselves lack transparency, without proper specification of how they are to be implemented (e.g. how Fsq is to be calculated) and how the achievement of objectives is to be assessed (neither in terms of the model used to specify this, nor in the level of uncertainty that is acceptable). The multiannual plan, without further specifications than the regulations alone, can appear to lack direction. A simple 10% reduction from an unclearly defined Fsq does not necessarily steer the stock towards the objectives. This is especially true given retrospective problems in the North Sea plaice and sole stock assessment. A stepwise decrease in the ‘distance’ between current F and the target F, while potentially invoking the 15% TAC change more often, may be more successful in assuring progress towards the objectives and prevent issues such as the projected increase in sole F from 2008 to 2009. The rationale for the target fishing mortality reference points in the long term management plan is not given in the Council Regulation. The objective F for the North Sea plaice stock is similar to, though slightly high than, the current proxy of FMSY for this stock as used by ICES. In the case of North Sea sole, the management objective F lies within the broad range of potential proxies for FMSY for the stock. North Sea plaice F is currently below the target F level while, a significant decrease in the F of North Sea sole is still required, especially considering that the current management F for the stock is likely to represent an increase in F from 2008 to 2009. In this context, the long term management plan will steer towards a further decrease in fishing effort by the main fleets targeting sole and plaice. Under the multiannual plan, the North Sea plaice TAC has been increasing. This increasing trend is likely to persist as long as the stock continues to recover because fishing in the near future should fluctuate around what is considered to be the optimum F for long term sustainable yields. Discarding levels remain high, but currently they are near the lowest level of the past ten years and show a downward trend. North Sea sole TACs have stabilised to a degree under the multiannual plan in the most recent years, but these are likely to continue to fluctuate depending on the strength of incoming year classes. The data available to analyse the stock dynamics under the multiannual plan allow the following conclusions to been drawn with respect to the chosen reference points and the safe biological limits of the stock: Spawning Stock Biomass (SSB) of both species have increased since the implementation of the plan. The XSA assessment for plaice (giving only point estimates), indicates that SSB has been larger than Bpa for two consecutive years. The SCA assessment (following Aarts and Poos 2009) indicates that plaice indeed has a larger than 95% probability of having reached a stage where the SSB is above Bpa for two consecutive years. For sole, the XSA stock assessment indicates that SSB has been above Bpa for two consecutive years. An alternative assessment including uncertainty estimates indicate that the probability of being above Bpa in not yet larger than 95%. The annual fishing mortality rates (F) of the two stocks have been declining in recent years. The North Sea plaice stock is now fished at a level below the management regulation target for this stock (0.2 per year). According to the latest assessment results, both stocks appear to be within the precautionary zone with regards to SSB and F in 2008. Hence, despite a lack of clarity in the implementation of the management regulations, the multiannual plan, given the current perception of the stock, appears to be resulting in stock trajectories and fishing levels moving towards the desired objectives and is, therefore, in line with the principles of the precautionary approach. In the first year of its implementation (2008), it appears that the effort regulations defined for the multiannual plan have been having the desired effect. Overall fishing effort has declined, along with a decrease in the size of the main fishing fleets utilising these resources. These reductions in effort seem to be compensating for issues relating to the practical application of management regulations on the setting of TACs. In the ex‐ante evaluation, three different approaches were used to test the effects of the management plan. The first was a yield curve analysis for the two stocks under different stock and recruit relationship assumptions to assess the equilibrium fishing mortality targets in the plan. The second approach is a projection of the two stocks under the rules of the plan, varying only future recruitment under different assumptions. Finally, the third approach is a full feedback MSE approach where in addition to the biology the fisheries system is also modelled. In order to show that the management plan is precautionary for the two species under consideration according to ICES, we use the Criteria agreed during WKOMSE to be applied in the evaluation of Harvest Control Rules/Management Plans in relation to precautionary reference points. The results presented here suggest that the multiannual plan can be considered to be precautionary for both of the managed stocks according to the criteria described by WKOMSE for the evaluation of multiannual plans. The plan allows for increases in yield to 2015 and in the long term while reducing the current levels of F. There is a very high likelihood of stock growth in terms of SSB for both stocks. Both the simple stock projections and full feedback MSE analysis showed that F is likely to remain at low levels allowing for increases in stock biomass. Caution needs to be taken in the interpretation of the MSE, and stock projection results because future projections take the stock to outside the range of historic observations. But by examining the performance of the plan at the lower ends of the simulation ranges and considering ‘worst case’ recruitment scenarios the likely risk of a management failure can be considered to be adequately estimated. The results presented show that the plan is very likely to be precautionary but it is more difficult to assess whether it achieves the goals of long term yields and sustained healthy populations. This is essentially a question over whether the F targets specified for the two stocks are reasonable and whether in practice they can be achieved simultaneously. The former relies of the definition of MSY for these two stocks and the corresponding stock sizes that can deliver these yields while the latter depends on how fisheries behaviour and gear selection changes into the future. Given the uncertainty associated in the estimation of Fmsy reference points and that expert opinion has been incorporated into the determination of target F points, the targets as they stand seem plausible. Regardless, it is clear that both stock growth and long term increases in current yield levels are likely should the multiannual plan be implemented.

Final summary for Rapport et Proces-Verbaux des Reunions Vol. 8. To see all other articles in this volume, please click on the keyword "RPVR Vol. 8"

ICES advises that its conclusions from 2018 remain valid, meaning that: 1. Removing the EU/UK TACs for the following stocks may generate a high risk of the stocks being exploited unsustainably: Witch (Glyptocephalus cynoglossus) in ICES Division 3.a, Subarea 4, and Division 7.d. Turbot (Scophthalmus maximus) in ICES Subarea 4. Brill (Scophthalmus rhombus) in ICES Division 3.a, Subarea 4, and divisions 7.d and 7.e. 2. Removing the EU/UK TACs for lemon sole (Microstomus kitt) in ICES Division 3.a, Subarea 4, and Division 7.d stock may generate a lower risk of the stock being exploited unsustainably. 3. For all stocks, management should be using a single-species TAC covering the stock distribution area.

From 1861 to 1962 daily observations of temperature and salinity were carried out in the Marsdiep tidal inlet near Den Helder. Since 1947 similar measurements have been made in the Marsdiep on the coast of the island of Texel. Monthly mean differences for temperature and salinity were determined from the overlapping years. With these differences the Den Helder series could be extended to a homogeneous series from 1861 until 2001. The seasonal and annual mean salinities and temperatures are presented. The years 1999 and 2000 were the two warmest since 1861, and 1996 was among the five coldest years. The mean annual temperatures reflect the West European climatic variability and are highly correlated with the annual mean air temperature in Den Helder. Ice winters with monthly mean temperatures below 0°C occur generally in winters with a low NAO index. The salinity shows a persistent decreasing tendency related to increased river discharge since the beginning of the observations. Article from Marine Science Symposia Vol. 219 - "Hydrobiological variability in the ICES Area, 1990-1999", symposium held in Edinburgh, 8-10 August 2001. To access the remaining articles please click on the keyword "MSS Vol. 219".

The NAFO/ICES Pandalus Assessment Group (NIPAG), met online to assess the Northern shrimp (Pandalus borealis) stock in Division 4.a West (northern North Sea, Fladen Ground). The objective was to assess the stock status in light of updated 2022 catch data and stock indices. Overall, the different sources of new and updated information (Norwegian survey data, Danish LPUE-index, and a Danish bycatch-based index), indicate that the shrimp stock on Fladen Ground has increased since 2018. A Danish observer and self-sampling program for the targeted shrimp fishery was initiated in 2021, which provided biological data of the stock (weight, length, and sex). If a commercial shrimp fishery is continued on Fladen Ground, these 2021 data may form the start of a new commercially based time-series that together with biological data from the Norwegian survey may enable a full analytical assessment of the stock. Due to likely irregular visits to Fladen Ground by the annual IMR shrimp survey an analytical assessment will have to be based mainly on data collected by the commercial fishery.

Contribution to the biology of the cod (Gadus callarias L.) in the Danish waters. This publication is part of Rapport et Proces-Verbaux des Reunions Vol. 136, which includes all contributions to a special scientific meeting on cod. To see all other articles in this volume, please click on the keyword "RPVR Vol. 136".

There are no new data available that change the perception of the stock. Therefore, the advice for this fishery in 2014 and 2015 is the same as the advice for 2013: ICES advises on the basis of the approach for data-limited stocks that catches should not increase, unless there is evidence that this will be sustainable. This corresponds to zero catches.

Study on the accumulation of oceanic contaminants in marine mammals. No summary available.

A Management Strategy Evaluation (MSE) analysis was conducted for North Sea saithe (subarea IV, Division IIIa and subarea VI) in response to a joint EU–Norway request to ICES for an assessment on options to revise the long-term management plan for saithe in the North Sea. Population trajectories for North Sea saithe were ex-plored under five alternative management scenarios in conjunction with the potential for optimistic (high recruitment and growth) and pessimistic (low recruitment and growth) biological production. B-Adapt was used for the operating model, and XSA was used as the basis for the management model corresponding with the methodolo-gy used in the 2012 ICES WGNSSK working group report. Future population trajec-tories for North Sea saithe depend on the management options adopted as well as the level of incoming recruitment and growth. Results for 2020 indicate that although the current management plan yields a favourable trade-off between the risk of spawning stock biomass remaining above Blim and median catch under an optimistic biological production scenario, this trade-off deteriorates under a pessimistic biological produc-tion scenario. When just considering the probability of spawning stock biomass re-maining above Blim, the management options that use alternative TAC stability mechanisms achieve similar values to the current plan under an optimistic biological production scenario, but also perform slightly more favourably under a pessimistic biological production scenario.

Description not yet available.

Version 2 has changes made to Table 2: extra scenarios added, as well as labelling and rounding updates. ICES advises that when the MSY approach and precautionary considerations are applied, there should be zero catch in 2024. ICES notes the existence of a precautionary management plan, developed and adopted by one of the relevant management authorities for this stock. Management should be implemented at the stock level.

Report from Russia on seal biology and on seal hunting. This publication is part of Rapport et Proces-Verbaux des Reunions Vol. 8. To see all other articles and illustrations in this volume, please click on the keyword "RPVR Vol. 8". Publication in German.

The variability of transport processes and stratification in the North Sea is investi­gated using the results of a 40-year simulation with the 3-D hydrodynamic model HAMSOM (HAMburg Shelf Ocean Model). The results show that there is consider­able variability of physical processes potentially impacting on ecosystem dynamics. Stratification and transport processes are characterized by year-to-year variability. However, resolution of decadal variability is possible. Long periods with similar strati­fication as well as transport conditions have been resolved and the 1990s have been identified as having been an outstanding period with respect to two key biologically relevant physical parameters both potentially impacting on the ecosystem dynamics; the exchange flow into the North Sea and Skagerrak in February/March and the timing of the onset of stratification in spring. There is pronounced interannual variability and a comparison of variability in different seasons indicates that the between-season correlations are small for water transports as well as for stratification conditions. Article from Marine Science Symposia Vol. 219 - "Hydrobiological variability in the ICES Area, 1990-1999", symposium held in Edinburgh, 8-10 August 2001. To access the remaining articles please click on the keyword "MSS Vol. 219".

The present communication is restricted to a consideration of the changes which have taken place in the haddock population of the North Sea plateau during the last decade. A census of the moving and ever-changing pop­ulation in this extensive area during the period under review has been obtained by a combination of three methods :- The collection of statistics and measurements of fish caught in the region and landed at British ports. Ichthyometrical observations made at sea on commercial vessels by the Ministry of Fisheries (England) Measurers to assess the proportions of unmarketable sizes of haddocks in the total catches from different grounds. Periodic trawling surveys of the principal haddock grounds with Standard Otter Trawl by the Scottish Research Vessel ’’Explorer” to amplify the market statistics and to obtain data with regard to the abundance and distribution of demersal haddocks of small sizes which normally escape capture by the ordinary commercial fishing gear. The ideal aimed at has been a monthly censusof the densities and distributions of the several age classes which make up the total demersal haddock population. Inludes 3 appendices: A) The Magnitude of the Destruction of Haddock of Unsaleable Sizes.(by A. B.), B) A Comparison of the Vigneron-Dahl Trawling Gear with the Ordinary Otter Trawl in the Haddock Fishery, (by A. B.), and C) The Food and Feeding Habits of the Haddock, by Alfred Ritchie, B.Sc Reports of the proceedings of a special meeting held on June 24th 1932, at Copenhagen; 'The Effect upon the Stock of Fish of the Capture of Undersized Fish'.This publication is part of Rapport et Proces-Verbaux des Reunions Vol. 80. To see all other articles in this volume, please click on the keyword "RPVR Vol. 80".

The 2012 advice for this stock is biennial and valid for 2013 and 2014 (see ICES, 2012): “Based on the ICES approach for data limited stocks, ICES advises that catches should be no more than 11 tonnes”. ICES advises that the same catch advice is still applicable to 2015.

The object of this paper is not to submit new considerations to the general discussion on the effect of thinning on the stock of fish, but simply to enphasize the necessity of obtaining abundant numerical data before we may consider ourselves in position to decide whether thinning or protection is preferable in each of the natural sections of the continental coast of the North Sea. We want to obtain more details about the normal density and variations of each young-fish population, the local productivity of food and the amount of destruction resulting from commercial fishing and shrimping operations. Reports of the proceedings of a special meeting held on June 24th 1932, at Copenhagen; 'The Effect upon the Stock of Fish of the Capture of Undersized Fish'. This publication is part of Rapport et Proces-Verbaux des Reunions Vol. 80. To see all other articles in this volume, please click on the keyword "RPVR Vol. 80".