Expertise
ICES advice on fishing opportunities: What's behind it?
Alexander Kempf, Holger Haslob, Jens Ulleweit, Norbert Rohlf, Matthias Bernreuther, Christoph Stransky, Karl-Michael Werner, Uwe Krumme, Christopher Zimmermann, Sven Stötera, Stefanie Haase, Kristina Barz | 13.10.2023
In its annual advice, ICES provides an overview of the status of exploited fish stocks in the northeast Atlantic and publishes recommendations for future sustainable fishing opportunities. We explain what the advice means for German fisheries and why recommendations are at a certain level.
Each year, the International Council for the Exploration of the Sea (ICES) publishes the scientific advice on the status of fish stocks in the Northeast Atlantic (ICES Advice) and proposes sustainable fishing opportunities for the following year. Below, we explain the status of the most important fish stocks for German fisheries in the North Sea, the Baltic Sea and Northeast Atlantic and the background of scientific recommendations for total allowable catches.
Fortunately, the status of many fish stocks in the Northeast Atlantic and adjacent areas has improved in recent years. With reductions in fishing quotas and the resulting restrictions on fishing, the biomass of many stocks is showing a positive trend. From 2003 to 2021, the biomass of data-rich stocks with analytical assessments in the Northeast Atlantic increased by an average of 39%. However, the range of trends for individual stocks is large, and for some stocks it is negative (e.g., cod in the North Sea).
Many stocks are sustainably managed in line with the maximum sustainable yield (MSY) concept in EU waters, although the MSY target is not achieved for all stocks. In 2021, 60 out of 81 stocks for which corresponding reference values are available achieved the MSY criterion. This represents 74% of the assessed stocks, compared to only 27% in 2003. The fishing mortality rate, averaged over all stocks, was significantly below the MSY target values in 2021, while in 2003 the target value was exceeded by an average of 67%. This indicates that the level of overfishing has decreased considerably (data source: STECF Report 2023).
Fishing mortality is a measure of the amount of fish or other marine living resource taken by catch from the harvestable portion of a stock over a given period of time.
The recovery of stocks also has positive economic effects. However, other factors also play a crucial role. For example, the EU fishing fleet recorded net profits of EUR 800 million in 2020. However, due to the Corona pandemic and very high fuel costs, the EU fleet made an overall loss in 2022 for the first time since 2008. For 2023, at least a small overall net profit is expected.
Explanations on the ICES advice for 2024
Cod on the northern shelf has been divided into three substocks (Southern substock, North Western substock and Viking substock) since this year. Workshops to clarify the stock structure of cod in the North Sea and west of Scotland have shown that the three substocks differ genetically and/or in their biological characteristics (e.g. growth, maturity at age). The population sizes of the substocks have also developed differently. In particular, the southern substock shows a worse development than the north-western and Viking substock. For these reasons, ICES considers an assessment based on substocks to be appropriate.
According to the available stock calculations, all three substocks were fished above FMSY in 2022. While the north-western substock is within safe biological limits at the beginning of 2023, the Viking substock is slightly below this limit. The southern substock is currently well outside safe biological limits and below the Blim biomass limit. Since the southern substock in particular marks the southern limit of the cod distribution area, climatic changes play a role in addition to fishing.
The calculations based on the three substocks are based on the assumption that the substocks do not mix in the first quarter because they stay in their respective substock areas during the spawning season (Figure 1). In quarters two to four, however, substocks mix to a large degree.
By default, ICES gives advice based on the MSY approach. However, advice based on the MSY approach alone for each of the three substocks is not possible in this particular case, as no (genetic) data are available to quantify the mixing of the substocks in quarters two to four. An advice based purely on the MSY approach at the substock level is therefore not implementable for management, as without knowledge of the spatial distribution and mixing of substocks in quarters two to four, compliance with the adviced catch levels for all substocks cannot be ensured.
Therefore, to address the problem of unknown spatial distribution and mixing of substocks in quarters two to four, the weakest substock (the southern substock) is protected according to ICES advice. To achieve this, the fishing mortality for the north-western and Viking substock was reduced in the forecasts to the same extent (by 60.4%) in a precautionary approach as is required for the southern substock under the MSY approach. The resulting advice is a maximum allowable catch (TAC) for the stock complex (22 691 tonnes). As in the past, this advice can be implemented by allocating it among the existing TAC areas. Assuming constant fishing patterns, mixing and stock parameters, the maximum allowable catch will result in none of the substocks being overfished.
The other numbers in the advice per substock ("...which corresponds to 13 529 tonnes from the northwestern substock, 5240 tonnes from the Viking substock, and 3922 tonnes from the southern substock) serve mainly to explain how the 22 691 tonnes were derived. Also, due to the mixing of substocks ICES advices that these substock TACs should not be interpreted as area-specific advice (e.g. 13 529 tonnes should not be set as a TAC for the blue area in Figure 1).
The explanation of the Northern Shelf cod as a PDF download
Contact: Dr. Alexander Kempf
The stock is assessed to be just within safe biological limits in 2023. According to the latest assessment, the stock was fished just below FMSY in 2022. The productivity of the stock has been lower in the last 10 years than in previous decades, suggesting additional unfavourable environmental impacts.
ICES recommends a maximum catch of 73,815 tonnes under the MSY approach for 2024. This represents an increase of 25% compared to last year. This increase is explained by a higher estimate of stock biomass compared to last year's assessment.
All the larger fleets fishing directly for saithe saw a decrease in catch rates compared to the years around 2015, but between 2020 and 2022 there is a reversal of the trend and some increase in catch rates have been observed. The interpretation of the commercial data is not easy, however, as changes in catch patterns may also result from economic conditions. This increases the uncertainty around stock estimates. Since the scientific survey is not specifically targeting saithe either, the assessment as a whole is considered uncertain.
The explanation of the saithe in the North Sea as a PDF download
Contact: Dr. Alexander Kempf
Due to a strong decrease in the fishing effort of the main flatfish fleets since the beginning of the 2000s, the fishing pressure on plaice has decreased significantly since then. It has been below FMSY since 2007. The calculated recruitment has been mostly above average since 2010. Spawning stock biomass has increased significantly in recent decades, reaching its highest level in 2014. Since then, the stock has declined slightly due to natural fluctuations, but remains well above all biomass reference points.
The ICES catch recommendation under the MSY approach for 2024 for plaice from the North Sea and Skagerrak combined is no more than 155,015 tonnes. This is slightly above last year's recommendation (+3.1%). The total catch in recent years has always been well below the maximum recommended catch, as it does not seem profitable to fish out the quotas. High fuel costs are likely to further worsen the situation for flatfish trawlers.
The explanation of Plaice in the North Sea as a PDF download
Contact: Dr. Holger Haslob
The spawning stock biomass of sole in the North Sea showed a generally decreasing trend until 2007 after a high in the early 1990s. After this low, the stock recovered slightly, but remained below the critical reference level Blim for a long time. Due to a strong 2018 year class, the spawning stock biomass increased somewhat in recent years and the stock was estimated to be just above Blim in 2023. Fishing mortality (F) has declined overall since 1997, but was always well above the reference value of FMSY. Only since 2020 there has been a noticeable drop towards FMSY and for 2022 the fishing mortality rate is estimated to be below FMSY (but major problems with the estimation for the last years in the assessment, see below!). The calculated recruitment has mostly been below the long-term mean since the early 1990s with no discernible trend. However, the 2018 cohort is slightly larger, as mentioned above. Currently, the fishery mainly relies on this larger year class.
ICES recommends a total allowable of 3,588 tonnes for 2024, which is 61% lower than the previous year's recommended catch. The reason for the lower catch recommendation is problems in the assessment, which with each new data point estimates the spawning stock biomass significantly lower and the fishing mortality significantly higher than a year earlier. To compensate for this bias, it is assumed that this pattern also occurs in the latest assessment. Therefore, the forecasts are carried out with downward "corrected" values for the numbers per age class at the beginning of the forecast. A benchmark is planned for 2024 to improve the quality of the assessment.
The explanation of sole in the North Sea as a PDF download
Contact: Dr. Holger Haslob
The spawning stock biomass of North Sea herring has fluctuated between 1.2 and 2.4 million tonnes since the late 1990s. Since 1996, the spawning stock biomass has been within safe biological limits and fishing mortality has been consistently below FMSY.
Despite sufficient stock biomass, herring recruitment has been below average since 2003. Only 2013 produced a stronger year class. A somewhat larger recruitment is also calculated for 2022. From herring larval catches on the spawning grounds it is evident that sufficient larvae continue to hatch. However, in many years these do not reach the juvenile herring stage. The reasons for this are not conclusively clear. As a result of low juvenile production, the stock has declined over the last few years, but stays above bomass limits.
For 2024, ICES recommends a maximum catch of 532,166 tonnes (of which 522,832 tonnes are for human consumption fisheries) under the MSY approach. This is 31.8% more than the maximum catch set in 2023 for the human consumption fleet and 28.3% more than last year's ICES recommendation.
In addition to the fishery for human consumption (A fleet), there is also an industrial fishery in the North Sea for the production of fish meal and fish oil (B fleet). As juvenile herring are the main by-catch in the sprat fishery, this fleet segment has its own catch limit for herring by-catch (for 2024 this is 9,334t according to the ICES recommendation). In addition, herring stocks from the North Sea and the Baltic Sea mix and are caught together off the southern Norwegian coast, in the Skagerrak/Kattegat and in the western Baltic Sea. For Baltic herring from the western Baltic Sea, Skagerrak and Kattegat, ICES recommends a fishing ban for 2024 due to the poor stock status. Therefore, the corresponding recommendations for catch shares of North Sea herring in the areas mentioned (so-called C and D fleet) have been set to zero.
The explanation of herring in the North Sea as a PDF download
Contact: Dr. Norbert Rohlf
The spawning stock biomass of Northeast Atlantic mackerel has increased substantially since the 2000s to a maximum in 2014, and has been declining since then, but is still estimated to be within safe biological limits. Fishing mortality has declined since 2003 and has been below FMSY since 2016. Some large year classes have developed since the early 2000s. As a result of increased biomass and climatic changes, the stock has substantive expanded its area of distribution to the northwest (Iceland, Greenland) since the late 2000s, especially during the long summer feeding migrations. However, this process does not seem to be continuing at present.
An age-based model is used to assess the stock. This model uses - in addition to commercial data - the triennial mackerel egg survey, which targets the annual egg production, and for several years also a Nordic survey, which focusses on the stock during the feeding migration. In addition, the International Bottom Trawl Survey (IBTS) is used in Q4 and Q1 to provide estimates of juvenile abundance. Norwegian tagging data, using recapture rates to estimate stock size, have also been integrated into the assessment in recent years.
The latest scientific advice from 2023 sets a total allowable catch for 2024 of 739386 tons, which is five percent lower than the previous year's advice of 782066 tons. In recent years, however, coastal states (e.g. EU states, Norway, Faroes, Iceland, Greenland, Russia) have been unable to agree on a common total allowable catch and the sum of established unilateral quotas exceeds the scientific advice by far. Mackerel is also caught in international waters, which further complicates management.
The explanation on mackerel in the North-East Atlantic as PDF for download
Contact: Jens Ulleweit
As Russian scientists are currently excluded from ICES work, it was not possible to carry out a stock assessment within ICES in the last two years.
The explanation of cod in the East Arctic as a PDF download
Contact: Dr. Matthias Bernreuther
The German fleet fishes for redfish mainly on the Greenland shelf and until 2020 in the Irminger Sea. Two redfish species, the deep redfish (Sebastes mentella) and the golden redfish (S. norvegicus, formerly S. marinus), occur there in several stocks. The status of these stocks varies. On the East Greenland shelf, the two species are also caught together. Distinguishing between S. norvegicus and S. mentella is often difficult, resulting in misreporting between the co-occurring species or both species being reported together as "redfish". This complicates stock assessment and management.
The S. norvegicus stock on the East Greenland shelf is part of the stock largely found on the Iceland shelf. The spawning stock biomass has been within safe biological limits since 2003 and has been fished according to the MSY principle since 2006. The ICES catch recommendation of no more than 41,286 tonnes for 2024 is 62% above the maximum recommended catch for 2023 of 25,545 tonnes and follows the ICES MSY approach. The significant increase in the maximum recommended catch results from a new assessment approach adopted in a benchmark in 2023. In the medium term, however, there is concern about recruitment to the stock, as this has been low since 2014. It is expected that the spawning stock biomass will decrease in the future as a result.
The exact status of the S. mentella stock on the Greenland shelf cannot be accurately assessed. The stock has declined sharply since 2010 and has not improved in subsequent years. As the most recent Greenland Shallow Water Survey biomass index values from 2020 were close to zero and the index from 2022 was not much higher, ICES recommends zero catch from this stock in 2024.
In the neighbouring Irminger Sea, two other S. mentella stocks occur, which are caught with pelagic trawls. These two stocks have also declined so much that ICES has recommended no fishing for the shallow stock since 2010 and for the deep stock since 2017. In 2021, the stock status of the shallow S. mentella stock in the Irminger Sea could be reassessed for the first time since 2013. The result of the survey was slightly more positive, as the resulting biomass index showed the highest value since 2005, but remained at a low level in historical comparison. Despite the slightly more positive assessment, the recommendation of a zero catch remains, as the slihgtly more positive result must first be confirmed in the next scientific survey. The deep stock (> 500 m water depth) has been fished since the 1990s with a fishing mortality rate well above FMSY. The results of the above-mentioned survey in 2021 show the lowest biomass value for the deep stock since the beginning of the survey. While e.g. Russia continues to fish for these stocks, the EU currently does not allow fishing for either stock.
The explanation of redfish in the Greenland/Irminger Sea as a PDF download
Two redfish species of commercial importance are found on the Norwegian shelf, in the Norwegian Sea and in the Barents Sea: Beaked redfish (Sebastes mentella) and Golden redfish (Sebastes norvegicus).
The Sebastes mentella stock is currently most likely in a good condition. Spawning stock biomass increased steadily between 1992 and 2005 and has stabilised at a high level since then. Fishing mortality (F) has been low since 1997 (F = 0.01 - 0.06), and strong year classes of offspring have been observed again since 2006. Under the precautionary approach, ICES recommended a maximum catch of no more than 67,210 tonnes for 2022, slightly higher than the total allowable catch for 2021 of ≤ 66,158 tonnes. A triennial scientific survey in the Norwegian Sea has been conducted in August 2022. After the results of this survey have been analysed, the assessment of the stock status can be updated in 2023.
In contrast, the golden redfish stock (S. norvegicus) found on the Norwegian shelf and in the Barents Sea is currently in poor condition. The spawning stock biomass has declined steadily since the late 1990s and is at its lowest level in the time series. Therefore, ICES has recommended zero catch for 2022 and 2023. In addition, ICES recommends minimising bycatch of golden redfish in other fisheries, such as for cod and saithe. Nonetheless, 3,000 to 10,000 tonnes per year have been caught internationally in recent years.
The explanation of redfish in the Norwegian Sea/Barentssea as a PDF download
A benchmark in 2023 used new genetic information to divide the cod stock complex off Greenland into three stocks.
The western inshore stock lives in the extensive fjord systems and is divided into a northern and southern stock component. The offshore stocks are divided into a West Greenlandic and an East Greenlandic-Icelandic high seas stock based on genetic stock allocations. Historically, the peak of the cod fishery off Greenland in the 1950s and 1960s was associated with a large West Greenland stock, while the recovery since 2000 has been increasingly due to a strengthening of the East Greenland stock and/or increased exchange with the Icelandic stock. Overall, the stocks in Greenlandic waters mix during different life stages. Therefore, it is generally difficult to assign catches from the fishery directly to a stock. Only a subsequent genetic study can provide more clarity.
After the collapse of the stock in the early 1990s, there was a 10-year period of very low population density. After a moratorium until 2005, fishing has been allowed again in 2006.
A solid stock assessment for the East Greenland stock is currently not possible, as seasonal migrations between East Greenland and Iceland prevent separate calculations. Mixing with the Icelandic stock probably means that the majority of catches in East Greenland currently come from Dohrnbank, which lies in Greenlandic territorial waters between East Greenland and Iceland. Due to the lack of information, the recommendation of 23,518 tonnes maximum catch for 2024 is only based on a 20% reduction (precautionary buffer) compared to the observed catch in 2022.
The West Greenland offshore stock is at a low level compared to historic values, but above critical biomass limits set in the 2023 benchmark. The scientific advice for 2024 is for 2398 tonnes total allowable catch based on the ICES MSY concept.
The two components of the West Greenland inshore stock are not targeted by German fisheries. Both components are overfished with respect to the MSY concept, but are within safe biological limits.
The explanation of cod around Greenland as a PDF download
Contact: Dr. Karl-Michael Werner
For Greenland halibut as a deep sea stock, no consistent scientific research survey is available for the large assessment area including the Faroe Islands, Iceland and East Greenland. Accordingly, the stock dynamics are estimated to a greater extent from commercial catch data next to a combined research index derived from different surveys, with the results depending on the weighting of the individual input data.
A scientific stock assessment is available. The stock shows a slight recovery after stock density reached its lowest levels in 2006-2011. In recent years, the stock has been stable just within biologically safe limits. According to ICES recommendations for 2024, the annual catch should not exceed 21,541 tonnes. This represents a reduction of 19.4% compared to the previous year's recommendation. According to a benchmark in 2023, the stock status is estimated to be slightly worse than in previous years. According to the current assessment, fishing mortality has been above FMSY in recent years.
The explanation of Greenland halibut as a PDF download
Contact: Dr. Karl-Michael Werner
The directed fishery for cod in the eastern Baltic Sea has already been closed since mid-2019. In EU waters, only a bycatch quota in the mixed flatfish fishery is still in effect. The bulk of the remaining catch is taken by Russia. Although fishing pressure is now very low, the stock shows no signs of recovery. Natural mortality is considered more than ten times higher than fishing mortality. The lack of oxygen in the deep basins of the eastern Baltic Sea is particularly critical. As a result, important spawning and feeding areas are lost.
ICES again recommends the closure of the fishery for 2024 based on the precautionary approach. The EU has so far translated this into a bycatch quota of 595 tons and closed all recreational fisheries. The management objective is now no longer to rebuild the stock to sustainable levels, but to conserve what remains of that stock in order to allow for a recovery once the environmental conditions become more favourable.
The explanation of cod in the Eastern Baltic Sea as a PDF download
Contact: Dr. Uwe Krumme
This small but formerly very productive cod stock has been overfished since the early 2000s, i.e. fishing pressure has not been adjusted to the reduced production of offspring. Despite several warnings, politicians failed to adjust the management plan in force between 2007 and 2016 - mainly because the European Parliament and the Council of Ministers disagreed on who was in charge for this adjustment.
In 2015, however, the stock produced only 10% of the average amount of recruits: it collapsed. At this point, policymakers took the right measures, reduced the commercial catch drastically and involved recreational fisheries, which account for a significant share of the total harvest, in the recovery of the stock.
The following yearclass of 2016 appeared to be stronger, but did not contribute to the stock recovery as much as expected. Since 2023, the stock assessment is indicative of trends only and results are presented in relative terms. Due to a lack of reliable data, fishing mortality cannot be calculated. The relative harvest rate presented instead indicates that fishing pressure is now very low and has almost no influence on stock development anymore. Spawning biomass shows a slight increase in 2023, but remains far below the limit value. The reason for continued poor recruitment since 2017 has not yet been conclusively explained, but as with eastern cod, the influence of environmental conditions is apparently now much more important than that of fishing.
Since 2022, the directed fishery is closed, and a small bycatch quota (489 tons) has been set to keep the remaining fisheries open in the western Baltic Sea. The daily catch limit for the recreational fishery has been reduced to one cod. For 2024, ICES follows the standard approach for data-limited stocks and recommends a catch of only 24 tons (including angler’s catches).
The fishery reports that cod can no longer be caught in this area; therefore, the larger trawlers in Schleswig-Holstein, which largely targeted cod, have therefore been scrapped.
The explanation of cod in the Western Baltic Sea as a PDF download
Contact: Dr. Uwe Krumme
Western herring is the most important target species of the German coastal fishery, especially on the coast of Mecklenburg-Western Pomerania. Since about 2004, recruitment has been steadily declining and it took some time before catch levels were sufficiently adjusted to this situation. One main cause of the declining recruitment has been largely elucidated in 15 years of directed research: Later and warmer winters cause a mismatch between herring larvae and their most important food; most of the larvae starve to death.
As a result, the stock has declined sharply, and temporary was only half the limit reference value. ICES has therefore advised for the closure of the fishery for many years. For the Western Baltic management area, this recommendation was largely followed: Total allowable catches were reduced by 94% between 2017 and 2021. In contrast, in the northern part of the range (Kattegat and Skagerrak), where herring stay to feed in summer and fall, legal catches remained far too high: They were only reduced by 57% between 2017 and 2021. As a result, the German coastal fishery was deprived of its basis, but total outtake from the stock still remained so high that the stock could not recover. Only for 2022, Germany, Sweden, Denmark and Norway were able to agree on further drastic cuts in catches in the Kattegat and Skagerrak area as well. More than 80% of the catch is now taken in the eastern North Sea (under the North Sea Herring quota), and less than 10% in each of Kattegat/Skagerrak and the western Baltic Sea, respectively.
The stock remains far below the limit value, but appears to have increased over the past year. Fishing mortality has continued to decline in 2022 and is now for the first time sufficiently low to allow the stock to recover. This may take several years, and even then the stock can only provide half of the catch that could be sustainably fished in the 1990s. ICES maintains its recommendation for 2024 to close the fishery throughout its range.
The explanation of herring in the Western Baltic Sea as a PDF download
Contact: Dr. Christopher Zimmermann
Five flatfish species are commercially exploited in the Baltic Sea: plaice, flounder, dab, brill and turbot. Only plaice is limited by a quota. In the past, flatfish were mainly by-catch in the cod fishery; there were only small directed fisheries, e.g. for turbot. Since the closure of the two cod fisheries, flatfish have become one of the few exploitable target species in the western Baltic Sea.
The two plaice stocks seem to be doing well, benefiting mainly from the much lower predation pressure due to the poor condition of the cod. Recruitment is strong, ICES could therefore recommend an increase in catches for many years - catches of 17,947 tons are possible for 2024 in the Baltic Sea (SD22-32). However, the catches include discards, the vast majority of which have been illegal since 2017 and still account for over 20% of the catches from the area. The allowed plaice catch is not nearly fished out, due to a very uneven distribution of national quotas: Denmark is entitled to three quarters of the catch, the other nations share the rest. So for these fisheries, including Germany's, the quotas are very limiting, but not for Denmark.
There were first indications in 2022 that the plaice caught are becoming thinner, i.e. their corpulence factor is deteriorating. Whether this is a density effect or a consequence of changing environmental conditions, as is the case with cod, is unclear at this point.
The other flatfish stocks in the western Baltic Sea are also in good condition. However, the income achievable from flatfish fishing cannot come close to compensating for the catch losses of herring and cod.
The explanation of flatfish in the Baltic Sea as a PDF download
Contact: Dr. Sven Stötera
Sprat is one of the beneficiaries of the changed environmental conditions in the Baltic Sea. The biomass of this currently largest fish stock in the Baltic Sea (just under one million tons of spawning biomass) has been well within the green zone for many years, but fishing pressure is currently somewhat too high.
The German fishery exploit this resource with two large (about 50 meters long) and a few smaller trawlers, mainly for the production of fish meal and fish oil. The 2019 and 2020 year classes were above average, while the 2021 and 2022 year classes were rather weak.
ICES recommends a 10.3% reduction in catch (compared to the allowed catch for 2023) to a maximum of 241,604 tons in 2024 based on the multi-year management plan. This amount includes the Russian autonomous quota of about 45,000 tons. The stock calculation will be more uncertain in the future because Russian data will no longer be submitted, after Russia has been suspended from ICES.
The explanation of sprat in the Baltic Sea as a PDF download
Contact: Dr. Stefanie Haase
A comprehensive overview of the status of most marine fish stocks of importance to the German market is provided on the German website Fischbestände online.
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