Reproductive capacity of commercially exploited stocks of UK interest
The reproductive capacity indicator assessment shows that 53% of marine quota fish spawning stock biomass being at or above reference levels for maximum sustainable yield and meeting the criteria for GES. The estimation of biomass and associated references to assess this indicator for non-quota shellfish stocks is an area for continued research.
Background
The UK Marine Strategy (HM Government, 2010, 2019, 2025) continues with the policy commitment to achieve Good Environmental Status (GES) in UK waters that includes descriptor 3 commercially exploited fish and shellfish stocks being within safe biological limits. We report here the results from one indicator, reproductive capacity (D3C2) that refers to the proportion of stocks with a spawning stock biomass being at or above biomass levels capable of producing the maximum sustainable yield (MSY).
The key driver is the commercial fishing, taking place for decades as part of the international exploitation of marine fisheries resources, is managed by a range of national and international management measures aiming to protect and conserve marine fisheries resources. The UK Fisheries Act 2020 is a key regulatory framework to manage the pressure of commercial fishing activity, requiring stocks to be exploited sustainably to provide the maximum sustainable yield, defined as the highest theoretical equilibrium yield that can be continuously taken on average from a marine stock under existing environmental conditions without significantly affecting the reproduction process.
Further information
The reproductive capacity indicator assessment considers commercially exploited quota stocks (fish and Nephrops) and non-quota national shellfish stocks. The quota stocks, are internationally exploited, monitored, and assessed by the International Council for the Exploration of the Sea (ICES) and subject to agreed national total allowable quotas to manage the fishing pressure at or below maximum sustainable yield levels. The non-quota shellfish stocks reported in this assessment are shellfish stocks in UK waters that are not managed by agreed national allowable quotas. Although most of the non-quota shellfish stocks were not routinely monitored or formally assessed before the late 90’s, national stock assessments are undertaken and developed for crab, lobster and scallop to estimate biomass and reference points to establish a harvest rate or fishing pressure that can sustain the maximum sustainable yield (Dobby and others 2017; Delargy and others 2019; Cefas 2020a; 2020b; Lawler and others, 2023; Mesquita et al., 2023).
Data were lacking for biomass MSY reference point for the majority of national non-quota shellfish stocks, so trends in this indicator could be assessed only through the spawning stock biomass of marine quota fish stocks.
Assessment method
The reproductive capacity indicator was evaluated for 58 marine quota fish stocks. The GES assessment method for these stocks is evaluated at the level of stocks rather than species and is based on stock assessments results and threshold values from the lates ICES’ approach within the assessment cycle or period of 6 years (ICES, 2016) and compared with previous assessment cycles.
The reproductive capacity indicator (described as criterion D3C2) defines GES criteria as spawning stock biomass being at levels which in long term leads to maximum sustainable yield, by applying the threshold value for spawning stock biomass being at or above biomass levels capable of producing maximum sustainable yield (MSY) from the latest stock assessment to the spawning stock biomass recorded across the years of the assessment period (ICES, 2016, EU commission 2022). Stocks meeting such criteria are categorised as in ‘Good’ environmental Status, otherwise are classified as ‘not Good’ environmental status, and in cases where there is a lack of stock assessment providing spawning biomass estimates and MSY references are classified as unknown. Progress towards GES is assessed by comparing the results, as percentages achieving GES, between the latest and previous assessment cycles for the same list of stocks.
Results
The reproductive capacity indicator assessment shows that 53% of marine quota fish spawning stock biomass being at or above reference levels for maximum sustainable yield and meeting the criteria for GES. There is an increase towards GES for this indicator (Figure 1) from previous periods.
Figure 1. Reproductive capacity indicator for quota stocks showing GES changes in three assessment periods from 2004 to 2021.
The percentage of quota stocks with a reproductive capacity in Good status increased from 41% (2002-2009) to 52% (2010-2015) and to 53% (2016-2021). The percentage of quota stocks with unknown status did not change much between assessment periods.
The reproductive capacity indicator assessment (2016-2021) by regional seas (Figure 2) shows that 67% of quota stocks widely distributed and 61% of quota stocks in North Sea achieved GES, followed by 44% of quota fish stocks in the Celtic Seas. The percentage of quota stocks with unknown status for reproductive capacity is higher in the Celtic Seas (32%), that in Greater North Sea (17%) and widely distributed (16%).
Figure 2. Reproductive capacity indicator results for commercially exploited quota fish stocks in the UK Marine Strategy regions.
The reproductive capacity indicator results (2016-2021) are presented by individual quota stocks in Table 1.
The quota stocks in the Celtic Seas with reproductive capacity in good status are: Black-bellied anglerfish in Celtic Seas and Bay of Biscay; Cod in Irish sea; Haddock in the Irish Sea; Haddock in the southern Celtic Seas and English Channel; Herring in the Irish Sea; Megrim in Rockall; Megrim in west and southwest of Ireland; Nephrops in West Scotland, North Minch, Nephrops in West Scotland, South Minch, Nephrops in West Scotland Firth of Clyde and Sound of Jura, Nephrops in the Irish Sea East; Nephrops in the Irish Sea West, Nephrops in the west of southwest of Ireland, Porcupine Bank; Plaice in the Irish Sea; Sole in Western English Channel, Sole in Bristol channel , and Whiting in Rockall (whg.27.6a). White Anglerfish in Celtic Seas and Bay of Biscay.
In the Greater North Sea, the quota stocks with reproductive capacity indicator in Good status are: Megrim in northern North Sea and West of Scotland; Herring in the North Sea, Skagerrak and Kattegat, eastern English Channel, Herring in the Northeast Atlantic; Nephrops in northern North Sea, Fladen Ground, Nephrops in the Central North Sea, Firth of Forth; Nephrops in the Central North Sea, Moray Firth, Plaice in the North Sea and Skagerrak; Whiting in North Sea and easter English Channel.
The quota stocks widely distributed across the Norh East Atlantic ecoregions with reproductive capacity indicator in Good status are: Blue whiting in the Northeast Atlantic and adjacent waters; Hake in the Greater North Sea, Celtic Seas and the northern Bay of Biscay, mackerel in the Northeast Atlantic and adjacent waters; Spurdog in the Northeast Atlantic and adjacent waters.
Table 1. Reproductive capacity indicator GES results for commercially exploited marine quota fish.
|
Quota fish stock name |
Stock code |
Regional Sea |
Reproductive Capacity GES |
|
Anglerfish (Lophius budegassa. Lophius piscatorius) in subareas 4 and 6, and Division 3.a (North Sea, Rockall and West of Scotland, Skagerrak and Kattegat) |
anf.27.3a46 |
Greater North Sea |
Unknown |
|
Black-bellied anglerfish (Lophius budegassa) in Subarea 7 and divisions 8.a-b and 8.d (Celtic Seas, Bay of Biscay) |
ank.27.78abd |
Celtic Seas |
Good |
|
Blue whiting (Micromesistius poutassou) in subareas 1-9, 12, and 14 (Northeast Atlantic and adjacent waters) |
whb.27.1-91214 |
Widely distributed |
Good |
|
Cod (Gadus morhua) in Subarea 4, Division 7.d, and Subdivision 20 (North Sea, eastern English Channel, Skagerrak) |
cod.27.47d20 |
Greater North Sea |
Not Good |
|
Cod (Gadus morhua) in Division 6.a (West of Scotland) |
cod.27.6a |
Celtic Seas |
Not Good |
|
Cod (Gadus morhua) in Division 6.b (Rockall) |
cod.27.6b |
Celtic Seas |
Unknown |
|
Cod (Gadus morhua) in Division 7.a (Irish Sea) |
cod.27.7a |
Celtic Seas |
Not Good |
|
Cod (Gadus morhua) in divisions 7.e-k (eastern English Channel and southern Celtic Seas) |
cod.27.7e-k |
Celtic Seas |
Not Good |
|
Haddock (Melanogrammus aeglefinus) in Subarea 4, Division 6.a, and Subdivision 20 (North Sea, West of Scotland, Skagerrak) |
had.27.46a20 |
Greater North Sea |
Not Good |
|
Haddock (Melanogrammus aeglefinus) in Division 6.b (Rockall) |
had.27.6b |
Celtic Seas |
Unknown |
|
Haddock (Melanogrammus aeglefinus) in Division 7.a (Irish Sea) |
had.27.7a |
Celtic Seas |
Good |
|
Haddock (Melanogrammus aeglefinus) in divisions 7.b-k (southern Celtic Seas and English Channel) |
had.27.7b-k |
Celtic Seas |
Good |
|
Herring (Clupea harengus) in subareas 1, 2, 5 and divisions 4.a and 14.a, Norwegian spring-spawning herring (the Northeast Atlantic and Arctic Ocean) |
her.27.1-24a514a |
Greater North Sea |
Good |
|
Herring (Clupea harengus) in Subarea 4 and divisions 3.a and 7.d. autumn spawners (North Sea, Skagerrak and Kattegat, eastern English Channel) |
her.27.3a47d |
Greater North Sea |
Good |
|
Herring (Clupea harengus) in Division 6.a North (North of 56°00'N and East of 07°00'W), autumn spawners (West of Scotland) |
her.27.6aN |
Celtic Seas |
Unknown |
|
Herring (Clupea harengus) in Division 6.a South (South of 56°00'N and West of 07°00'W) and 7.b-c (northwest and west of Ireland) |
her.27.6aS7bc |
Celtic Seas |
Unknown |
|
Herring (Clupea harengus) in divisions 7.a South of 52°30'N. 7.g-h. and 7.j-k (Irish Sea, Celtic Sea, and southwest of Ireland) |
her.27.irls |
Celtic Seas |
Not Good |
|
Herring (Clupea harengus) in Division 7.a North of 52°30’N (Irish Sea) |
her.27.nirs |
Celtic Seas |
Good |
|
Hake (Merluccius merluccius) in subareas 4, 6, and 7, and divisions 3.a, 8.a-b, and 8.d, Northern stock (Greater North Sea. Celtic Seas. and the northern Bay of Biscay) |
hke.27.3a46-8abd |
Widely distributed |
Good |
|
Horse mackerel (Trachurus trachurus) in Subarea 8 and divisions 2.a, 4.a, 5.b, 6.a, 7.a-c, e-k (the Northeast Atlantic) |
hom.27.2a4a5b6a7a-ce-k8 |
Widely distributed |
Not Good |
|
Ling (Molva molva) in subareas 3, 4. 6-9, 12, and 14 (Northeast Atlantic and Arctic Ocean) |
lin.27.346-91214 |
Widely distributed |
Unknown |
|
Mackerel (Scomber scombrus) in subareas 1-8 and 14 and Division 9.a (the Northeast Atlantic and adjacent waters) |
mac.27.nea |
Widely distributed |
Good |
|
Megrim (Lepidorhombus spp.) in divisions 4.a and 6.a (northern North Sea, West of Scotland) |
lez.27.4a6a |
Greater North Sea |
Good |
|
Megrim (Lepidorhombus spp.) in Division 6.b (Rockall) |
lez.27.6b |
Celtic Seas |
Good |
|
Megrim (Lepidorhombus whiffiagonis) in divisions 7.b-k, 8.a-b, and 8.d (west and southwest of Ireland, Bay of Biscay) |
meg.27.7b-k8abd |
Celtic Seas |
Good |
|
Norway lobster (Nephrops norvegicus) in Division 6.a, Functional Unit 11 (West of Scotland, North Minch) |
nep.fu.11 |
Celtic Seas |
Good |
|
Norway lobster (Nephrops norvegicus) in Division 6.a, Functional Unit 12 (West of Scotland, South Minch) |
nep.fu.12 |
Celtic Seas |
Good |
|
Norway lobster (Nephrops norvegicus) in Division 6.a, Functional Unit 13 (West of Scotland, the Firth of Clyde and Sound of Jura) |
nep.fu.13 |
Celtic Seas |
Good |
|
Norway lobster (Nephrops norvegicus) in Division 7.a, Functional Unit 14 (Irish Sea. East) |
nep.fu.14 |
Celtic Seas |
Good |
|
Norway lobster (Nephrops norvegicus) in Division 7.a, Functional Unit 15 (Irish Sea. West) |
nep.fu.15 |
Celtic Seas |
Good |
|
Norway lobster (Nephrops norvegicus) in divisions 7.b-c and 7.j-k, Functional Unit 16 (west and southwest of Ireland, Porcupine Bank) |
nep.fu.16 |
Celtic Seas |
Unknown |
|
Norway lobster (Nephrops norvegicus) in divisions 4.b and 4.c, Functional Unit 5 (central and southern North Sea, Botney Cut-Silver Pit) |
nep.fu.5 |
Greater North Sea |
Unknown |
|
Norway lobster (Nephrops norvegicus) in Division 4.b, Functional Unit 6 (central North Sea, Farn Deeps) |
nep.fu.6 |
Greater North Sea |
Good |
|
Norway lobster (Nephrops norvegicus) in Division 4.a, Functional Unit 7 (northern North Sea, Fladen Ground) |
nep.fu.7 |
Greater North Sea |
Good |
|
Norway lobster (Nephrops norvegicus) in Division 4.b, Functional Unit 8 (central North Sea, Firth of Forth) |
nep.fu.8 |
Greater North Sea |
Good |
|
Norway lobster (Nephrops norvegicus) in Division 4.a, Functional Unit 9 (central North Sea, Moray Firth) |
nep.fu.9 |
Greater North Sea |
Good |
|
Plaice (Pleuronectes platessa) in Subarea 4 (North Sea) and Subdivision 20 (Skagerrak) |
ple.27.420 |
Greater North Sea |
Good |
|
Plaice (Pleuronectes platessa) in Division 7.a (Irish Sea) |
ple.27.7a |
Celtic Seas |
Good |
|
Plaice (Pleuronectes platessa) in Division 7.d (eastern English Channel) |
ple.27.7d |
Greater |
Not Good |
|
Plaice (Pleuronectes platessa) in Division 7.e (western English Channel) |
ple.27.7e |
Celtic Seas |
Unknown |
|
Plaice (Pleuronectes platessa) in divisions 7.f and 7.g (Bristol Channel, Celtic Sea) |
ple.27.7fg |
Celtic Seas |
Unknown |
|
Pollack (Pollachius pollachius) in subareas 6-7 (Celtic Seas and the English Channel) |
pol.27.67 |
Celtic Seas |
Unknown |
|
Roundnose grenadier (Coryphaenoides rupestris) in subareas 6-7 and divisions 5.b and 12.b (Celtic Seas and the English Channel, Faroes grounds, and western Hatton Bank) |
rng.27.5b6712b |
Celtic Seas |
Unknown |
|
Saithe (Pollachius virens) in subareas 4, 6 and Division 3.a (North Sea, Rockall and West of Scotland, Skagerrak and Kattegat) |
pok.27.3a46 |
Greater North Sea |
Unknown |
|
Sole (Solea solea) in Subarea 4 (North Sea) |
sol.27.4 |
Greater North Sea |
Not Good |
|
Sole (Solea solea) in Division 7.a (Irish Sea) |
sol.27.7a |
Celtic Seas |
Not Good |
|
Sole (Solea solea) in Division 7.d (eastern English Channel) |
sol.27.7d |
Greater North Sea |
Not Good |
|
Sole (Solea solea) in Division 7.e (western English Channel) |
sol.27.7e |
Celtic Seas |
Good |
|
Sole (Solea solea) in divisions 7.f and 7.g (Bristol Channel, Celtic Sea) |
sol.27.7fg |
Celtic Seas |
Good |
|
Sprat (Sprattus sprattus) in Division 3.a and Subarea 4 (Skagerrak, Kattegat and North Sea) |
spr.27.3a4 |
Greater North Sea |
Unknown |
|
Sprat (Sprattus sprattus) in Subarea 6 and divisions 7.a-c and 7.f-k (West of Scotland, southern Celtic Seas) |
spr.27.67a-cf-k |
Celtic Seas |
Unknown |
|
Spurdog (Squalus acanthias) in subareas 1-10, 12 and 14 (the Northeast Atlantic and adjacent waters) |
dgs.27.nea |
Widely distributed |
Good |
|
White anglerfish (Lophius piscatorius) in Subarea 7 and divisions 8.a-b and 8.d (Celtic Seas, Bay of Biscay) |
mon.27.78abd |
Celtic Seas |
Good |
|
Whiting (Merlangius merlangus) in Subarea 4 and Division 7.d (North Sea and eastern English Channel) |
whg.27.47d |
Greater North Sea |
Good |
|
Whiting (Merlangius merlangus) in Division 6.a (West of Scotland) |
whg.27.6a |
Celtic Seas |
Unknown |
|
Whiting (Merlangius merlangus) in Division 6.b (Rockall) |
whg.27.6b |
Celtic Seas |
Unknown |
|
Whiting (Merlangius merlangus) in Division 7.a (Irish Sea) |
whg.27.7a |
Celtic Seas |
Not Good |
|
Whiting (Merlangius merlangus) in divisions 7.b-c and 7.e-k (southern Celtic Seas and eastern English Channel) |
whg.27.7b-ce-k |
Celtic Seas |
Not Good |
Conclusions
This UKMS GES assessment provides an indication of the reproductive capacity on commercially exploited quota stocks.
This indicator shows 53% of marine quota stocks with a spawning stock biomass being at or above reference levels for maximum sustainable yield and meeting the criteria for GES.
Data to assess the reproductive capacity for non-quota shellfish stocks is very limited.
Marine quota fish are shared stocks and internationally exploited so the UK progress towards GES is influenced by international agreements and cooperation to maintain the spawning stock biomass to levels at or above maximum sustainable yield.
Depending on the future availability of a wider range of stocks assessments, the number of stocks (quota fish and non-quota shellfish) to include in the next assessment period could be increased.
Knowledge gaps
Monitoring and research programmes are required to address the lack of robust data and knowledge gaps in the underlying biology for data-limited stocks, and non-quota finfish and shellfish stocks, to feed into future stock assessments and determine sustainable reference points for more stocks, and to inform fisheries management advice.
The estimation of biomass and associated reference points are lacking for most non-quota shellfish; this is an area of continued research.
In addition to the fishing activities as pressure on the biomass of commercially exploited fish and shellfish stocks, there is a need to consider a wider range of combined pressures to assess GES, including the effect of environmental, climate and ecosystem changes on fish and shellfish populations.
References
Campón-Linares, V., McIntyre, R and Garnacho, E. (2025). Fish and shellfish stock assessments data for the UK Marine Strategy 2004 assessment of descriptor 3. Cefas, UK. V1. doi: https://doi.org/10.14466/CefasDataHub.173
Cefas. (2020a). Lobster (Homarus gammarus). Cefas Stock Status Report 2019. https://www.gov.uk/government/publications/crab-and-lobster-stock-assessments-2019
Cefas. (2020b). Edible crab (Cancer pagurus). Cefas Stock Status Report 2019. https://www.gov.uk/government/publications/crab-and-lobster-stock-assessments-2019
Dobby, H., Millar, S., Blackadder, L., Turriff, J., and McLay, A. (2012). Scottish Scallop Stocks: Results of 2011 Stock Assessments. Scottish Marine and Freshwater Science Volume 3 Number 10. ISSN: 2043-7722. https://www.gov.scot/publications/scottish-marine-freshwater-science-volume-3-number-10-scottish-scallop/
Delargy, A., Hold, N., Lambert, G. I., Murray L. G., Hinz H., Kaiser M. J., McCarthy, I., and Hiddink J. G. (2019). Welsh waters scallop surveys and stock assessment. Bangor University, Fisheries and Conservation Report No. 75. pp 48.
European Commission. (2022). MSFD CIS Guidance Document No. 19, Article 8 MSFD, May 2022. https://circabc.europa.eu/sd/a/20abe862-2684-4a16-9e25-52ffc2e71de6/GD19%20-%20MSFDguidance_2022_Art.8Assessment_REV_12-12-2023.pdf
ICES. (2016). ICES guidance on the practical methodology for delivering an MSFD GES assessment on D3 for an MSFD region/subregion. https://doi.org/10.17895/ices.advice.18686882
Lawler, A., Nawri, N., Harvey, J., Clarke, D., Vanstaen, K., and Benedet, R. (2023). Assessment of king scallop stock status for selected waters around the English coast 2021/2022. Cefas stock assessment report. https://www.gov.uk/government/publications/assessment-of-scallops-stocks-202122
HM Government. (2010). The Marine Strategy Regulations 2010. UK Statutory Instruments 2010 No. 1627. https://www.legislation.gov.uk/uksi/2010/1627
HM Government (2019). The Marine Strategy Part One: UK updated assessment and Good Environmental Status. https://www.gov.uk/government/publications/marine-strategy-part-one-uk-updated-assessment-and-good-environmental-status
HM Government. (2020). Fisheries Act 2020. UK Public General Acts 2020 c. 22. https://www.legislation.gov.uk/ukpga/2020/22
HM Government (2025) Marine strategy part three: 2025 UK programme of measures. https://www.gov.uk/government/publications/marine-strategy-part-three-2025-uk-programme-of-measures
Mesquita, C., Ellis, A., Miethe, T., and Dobby, H. (2023). Crab and Lobster Fisheries in Scotland: Results of Stock Assessments 2016-2019. Scottish Marie and Freshwater Science Vol 14 (5). 123 pp. https://doi.org/10.7489/12451-1.
Authors
Eva Garnacho1, Victoria Campón-Linares1, José De Oliveira1, Ewen Bell1
1Centre for the Environment, Fisheries and Aquaculture
Assessment metadata
| Assessment Type | UK MSFD Indicator Assessment |
|---|---|
D3.2 Reproductive capacity of commercially exploited stocks of UK interest
| |
| Point of contact email | marinestrategy@defra.gov.uk |
| Metadata date | Sunday, June 1, 2025 |
| Title | Reproductive capacity of commercially exploited stocks of UK interest |
| Resource abstract | |
| Linkage | |
| Conditions applying to access and use | |
| Assessment Lineage | |
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