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Publication - Research Publication

Economic impacts for Scottish and UK seafood industries post-Brexit: report

Published: 5 Jun 2018
Part of:
Brexit, Marine and fisheries

The report presents findings from research examining the possible impacts of EU exit on Scottish and UK seafood industries.

101 page PDF


101 page PDF


Economic impacts for Scottish and UK seafood industries post-Brexit: report
Appendix H: Zonal Attachment Calculations

101 page PDF


Appendix H: Zonal Attachment Calculations

Changes to production in the scenarios were based on a redistribution of quotas between the EU and the UK, moving from quota allocation based on Relative Stability and to one based on the zonal attachment ( ZA) principle.

Zonal attachment estimates for individual species, from the University of Aberdeen & SFF (2017) report, were used to calculate the potential additional catch for UK vessels, above their current (baseline) level of reported landings. The availability of zonal attachment information for the ten species is shown in Table H.1.

For each species (comprising several stocks), the new landings level (N), was calculated as:

N = L + M


L = current level of landings for a species (2011-2015 annual average, tonnes, from FAO production database)

M = extra landings as a result of zonal attachment redistribution of quotas for the species

M was calculated as:

Mathematical Equation


k = stock

ZUK = UK quota allocation based on zonal attachment

YUK = (current) UK landings

And Z UK was calculated as:

Mathematical Equation


A = zonal attachment percentage for UK waters

QEU28 = Quota for EU-28 (i.e. UK quota + rest of EU quota)

So, the full equation would be:

Mathematical Equation

Table H.1. Availability of zonal attachment information for key species

Species Zonal Attachment Information Available?
Crab N/a (non-quota species)
Nephrops No Zonal attachment was calculated based on the stock advice for each Functional Unit, together with an estimate of the proportion of the Functional Unit within UK waters
Salmon N/a (aquaculture production)
Scallops N/a (non-quota species)

The change in production value as a result of the distribution of quotas according to the zonal attachment principle was calculated as follows:

  • UK landings under ZA were calculated by applying the ZA average percentage from University of Aberdeen & SFF (2017) for North Sea and West of Scotland stocks to the TAC for each stock (taken from the TACs and Quotas Regulation) for 2015. Exceptions to this were:
    • For mackerel, the ZA percentage was applied to the overall TAC from the management plan agreed by the EU, Norway and the Faroes (1,054,000 t).
    • For herring in the North Sea, ZA percentages were provided separately for the adult and juvenile portions of the stock. Based on herring reaching maturity at age 3, and most herring in the North Sea being under 7 years old, the adult ZA percentage was pro-rated 4/7 (reach maturity @ age 3, most under 7 yr old); and the juvenile ZA pro-rated 3/7 (year classes 0, 1, 2).
    • For hake, the lower 95% quantile estimate was used instead of the average, because the Aberdeen University & SFF (2017) study probably overestimates the zonal attachment of this species because it is based on survey data from Area VI (which predominantly lies in UK waters) but the stock distribution covers a much wider area.
    • For Nephrops, ZA was based on the ICES stock advice for each Functional Unit ( FU), together with an estimate of the proportion of each FU in UK waters.
  • Distribution of quota from Area VII was assumed not to change, as no ZA estimates were available for Area VII stocks (i.e. cod, haddock, saithe, herring), with the following exceptions:
    • Hake, for which the stock management unit incorporates Areas VI, VII, Union and international waters of Vb, international waters of XII and XIV [32] , and the ZA percentage was applied to the whole stock management area;
    • Nephrops, for which the calculation was based on Functional Units (see above).
  • The potential additional landings for the UK under ZA were calculated from the ZA estimate compared to the actual level of 2015 UK landings (taken from quota uptake spreadsheets from Marine Scotland/ MMO).
  • It was assumed that there was no change in landings of Nephrops from North Sea and West of Scotland, because uptake of quota in these areas in 2015 was low (45% and 85% of initial quota allocation, respectively). The increase in Nephrops landings modelled was based on an increase in quota for Area VII grounds (an additional 1,244 tonnes). This is comparable with the potential increase in UK quota from the Zonal Attachment principle, compared to the UK’s initial quota allocation (an additional 1,471 tonnes). [33]
  • The change in UK landings was assumed to result in an inverse change in EU landings, except for haddock, where the decrease in EU landings was limited to the absolute level of increase of UK quota.
  • The change in the value of production was calculated based on the change in landings and the average value of production per tonne of live weight landings. Average value of production per tonne of live weight landings was calculated for the UK and EU, and applied to the change in landings expected from ZA. Using these average values of production incorporates the existing pattern of processing of each species in each country (group).

Detail of the change in landings as a result of using zonal attachment to determine the distribution of quotas is provided in Table H.2.

Table H.2. Calculations for change in landings based on zonal attachment distribution of quotas

Stock EU28 TAC/ Quota (t) (2015) Overall TAC (t) (2015) UK Uptake* UK ZA%** ZA Allocation ( UK) (t) UK Landings (t) (2015) Change to UK Landings (t) Change to EU Landings (t) Comments
NS Cod 24,227 29,189 130% 0.60 17,513 14,818 2,696 -2,696 Spare catching capacity in demersal sector - UK likely to be able to catch extra quota
WS Cod 74 74 416% 0.93 69 187 - 118 118
Other Cod stocks 6,955 6,955 107% 0.09 593 633 - 40 40 No ZA estimate - based on current allocations
Cod total 18,175 15,638 2,538 - 2,538
NS Haddock 34,197 40,711 90% 0.80 32,569 25,824 6,745 -3,784 Quota uptake was low in 2015 due to mismatch between the science and what is actually happening on the grounds - increasing quota but low availability of haddock on fishing grounds. Assumed UK catches increase to ZA allocation; EU reduction in landings limited to absolute increase in UK quota.
WS Haddock 4,536 4,536 86% 0.87 3,946 3,052 895 - 414
Rockall Haddock 2,580 2,580 99% 0.56 1,445 2,052 - 607 607
Other Haddock stocks 9,523 9,523 99% 0.15 1,400 1,393 7 -7 No ZA estimate - based on current allocations
Haddock total 39,360 32,321 7,039 - 3,598
NS Hake 3,190 3,190 519% 0.31 989 2,978 - 1,989 1,989 Lower 95% quantile used for ZA percentage ( ZA estimate based on survey from VIa to 300 m depth, but stock area covers VI, VII, Vb, XII, XIV), although this may still overestimate UK allocation.
WS Hake 50,944 50,944 84% 0.62 31,585 7,723 23,862 - 23,862
Other Hake stocks 47,803 47,803 0.00 - 174 - 174 174
Hake total 32,574 10,875 21,699 - 21,699
NS Herring 369,115 504,677 109% 0.55 275,409 73,087 202,323 - 202,323 ZA estimate based on adult ZA pro-rated 4/7 (ages 3-6), and juvenile ZA pro-rated 3/7 (ages 0-2)
WS Herring 22,690 22,690 111% 0.87 19,740 15,260 4,481 -4,481
Other Herring stocks 24,982 24,982 129% 0.16 4,079 5,249 - 1,170 1,170 No ZA estimate - based on current allocations
Herring total 299,229 93,595 205,634 -205,634
Mackerel 521,689 1,056,427 0% 0.36 380,314 247,979 132,335 -132,335 ZA percentage applied to management plan TAC
NS Nephrops 18,843 18,843 45% 0.81 15,321 6,959 - - Assume no increase in landings from ZA, as uptake is only 45% currently. ZA would potentially reduce UK quota by 188 t (1%).
WS Nephrops 14,190 14,190 85% 1.00 14,190 11,744 - - Assume no increase in landings from ZA, as uptake is only 85% currently. ZA would potentially increase quota by 336 t (2.4%), but current landings are >2000 t below UK quota allocation.
Nephrops VII 21,619 21,619 101% 0.39 8,415 7,171 1,244 -1,244 ZA based on ICES advice for landings for Functional Units
Nephrops total 37,926 25,874 1,244 - 1,244
NS Saithe 31,383 66,006 170% 0.46 30,363 8,923 21,439 - 21,439
WS Saithe 6,348 6,848 109% 0.84 5,752 3,286 2,466 -2,466
Other Saithe stocks 3,176 3,176 24% 0.14 434 103 331 - 331 No ZA estimate - based on current allocations
Saithe total 36,549 12,312 24,237 - 24,237