Evaluation of the minimum landing size for mackerel in the North Sea and Western Waters

Martin Pastoors, 30 March 2015

Introduction

The new landing obligation in EU creates an incentive to critically review the role of Minimum Landing Size (MLS), now called Minimum Conservation Reference Size (MCRS). Because all quota regulated under MCRS need to be landed but may not be used for direct human consumption, it is important to verify that the scientific background of the MLS actually reflects a sound reasoning that can underpin the MCRS concept.

This paper specifically deals with the MLS for mackerel. For this species the MLS for the North Sea has been set at 30 cm and for the other areas at 20 cm. At the same time, a substantial portion of the catch of the Western Stock component is taken in the northern North Sea under a special condition (between September and January). The recent interpretation from the EC and Member States is that the 30 cm minimum size also applies to mackerel caught under the flex arrangement.

So what is the rationale behind these MLS values and how do they apply to the different stock components identified by ICES? To address that question, a historical analysis of MLS will be carried out, going back over policy documents (e.g. technical measures), ICES documents (working group reports, advisory reports) and some scientific papers. In addition, the composition of mackerel catches (age, size, maturity stage) was analyzed to address the overall maturity stage in relation to potential arguments for setting MCRS.

Material and methods

A backwards snowballing method has been used to trace the history of MLS for mackerel. Starting with the most recent scientific advice on mackerel (ICES 2014a), the references to expert group reports and regulations were followed up. All references to MLS were quoted and references to earlier reports were then investigated. This lead to a year range of 1968-1998 as the most informative range on the background of the mackerel MLS.

The most recent of mackerel (ICES 2014b) was used as a basis to assess the maturity stage of current catches of mackerel and how that relates to potential indicators for MCRS.

Results

History of scientific advice and decisionmaking

An overview of historical documents advising on or setting values for MLS of mackerel are shown in Appendix 1 and summarized below.

Year Type Reference Contents 1968 Paper (Revheim and Proposed to raise the minimum legal size of mackerel for industrial Hamre 1968) purposes to 30 cm 1974 Working (ICES 1974) A 33 cm minimum landing size would give practically the same yield per group recruit and would give a better condition of the stock than one of 30 cm. For practical reasons, however, 30 cm is preferable. 1981 Advisory (ICES 1982) ACFM recommends a minimum landing size of 30 cm for mackerel in all Committee areas 1986 Advisory (ICES 1987) More general protection could be achieved by adoption of a minimum Committee landing size and ACFM recommends the introduction of a 30-cm limit for mackerel in all areas. Year Type Reference Contents 1986 Regulation (Council of the Minimum Landing Size for Mackerel (Scomber scombrus): Region 2 European Union North Sea only 30 cm, Region 3 to be determined. 1986) 1987 Advisory (ICES 1988) North Sea mackerel: “The 30-cm minimum landing size at present in Committee force in the North Sea should be maintained.” Western Mackerel: “ACFM reiterates its recommendation that a 30-cm minimum landing size should be implemented in all areas.” 1989 Working (ICES 1989) “The 30-cm minimum size limit was originally introduced in the North group Sea by Norway in 1971 and was intended to protect the very strong 1969 year class from exploitation in the industrial . It does not seem necessary to extend this measure to the Western area. The introduction of a 30-cm minimum size in the area in order to make it consistent with similar measures in the North Sea may result in an increase in the quantities of juvenile mackerel which will be slipped or discarded.” 1989 Advisory (ICES 1990a) “In the Western area, juvenile and adult mackerel were found to occur Committee within the same fishing locations, and an introduction of a minimum landing size could lead to a higher discard rate. ACFM, therefore, concluded that there would be no benefit from adopting a 30-cm minimum landing size in the Western area.” 1990 Working (ICES 1990b) “Again, as expressed in 1989, the introduction of a 30 cm minimum size Group for the Western area does not seem necessary on biological grounds and would lead to a higher discard rate when a strong year class enters the fishery.” 1991 Proposal for (Commission of the [unfortunately this document is not available of Eurlex] regulation European Communities 1991) 1992 Regulation (Council of the Minimum Landing Size for Mackerel (Scomber scombrus): Region 2 European Union North Sea only 30 cm, Region 1, 2, 3 and 5 (except North Sea): 20 cm. No 1992) underpinning of 20 cm provided. 1993 Working (ICES 1993a) “there appears to be no reason why fishing on the western stock should group not be permitted in Divisions Iva and Iia during the third and fourth quarters.” 1998 Regulation (Council of the Minimum Landing Size for Mackerel (Scomber scombrus): whole area European Union except North Sea: 20 cm. North Sea: 30 cm 1998)

The historical overview shows a number of important points:

 The MLS of 30 cm in the North Sea was originally introduced by Norway in 1971 and was intended to protect the very strong 1969 year class from exploitation in the industrial fishery. The 30 cm became the norm for the North Sea MLS on the basis of productivity assumptions.  In the early 1980s, ICES recommended to introduce the 30 cm MLS for mackerel in other areas in order to protect juvenile mackerel from being caught.  A full review by the Mackerel Working Group in 1989 resulted in a change of perception within ICES. It was no longer recommended to apply a 30 cm MLS for mackerel in other waters than the North Sea because it was expected to result in increased .  The MLS for mackerel in western waters was set at 20 cm in 1992. Unfortunately, the underpinning of that regulation (i.e. the European Commission proposal) is no longer available, so that the arguments cannot be reviewed or tested.  The MLS of mackerel in North Sea (30 cm) and other waters (20 cm) has remained in place since 1992 and have not been critically reviewed since. Mackerel catch composition

Catch numbers at age, weight at age (in the catch) and proportion mature of NEA mackerel were taken from WGWIDE 2014 (ICES 2014b). These variables were multiplied to derive the proportion of mature catch in weight and in numbers. This indicates that for the recent period (2000-2013), the landed catches consisted for 95% (weight) or 89% (numbers) of mature mackerel.

Catch compositions of Dutch freezer-trawlers fishing mackerel under the flex conditions, generally resulted in catches of mackerel of 25 cm and above.

Figure 1 NEA mackerel. Proportion of mature catch in numbers and in weight. Data calculated from WGWIDE 2014.

Conclusions

 Mackerel MLS in North Sea and Western Waters have largely been set on historically developed values without a very strong scientific underpinning or review.  Over the past years, the MLS of 20 cm has been used for catches of mackerel in the North Sea under the special condition in the TAC and Quota regulation (even though the MLS was formally at 30 cm for the whole of the North Sea)  The current practice of application of 20 cm MLS for western mackerel appears to deliver catch compositions that are largely consisting of mature fish (95% in weight, 89% in numbers).

Recommendation

Given the need to define MCRS under the landing obligation in order to make optimal use of the natural resources without jeopardizing the reproductive capacity of the stocks, it can be recommended to apply the 20 cm MLS of western mackerel also to the fishery that takes place under the flex arrangements in the North Sea and to include that reference in the special conditions that are allowed from 1st September to 15 February.

Appendix 1 Excerpts from ACFM report, WG reports and scientific papers

Revheim, A., and Hamre, J. 1968. A brief statement on the present state of the Norwegian mackerel fishery. ICES C.M. 1968 / H:24.

“The minimum legal size limit of mackerel for reduction is at present 20 cm. This low size limit has practically no effect on the purse-seine fishery off the coast, but was in fact introduced in order to protect the 0-age group of mackerel which occurs regularly in inshore waters during late Summer and Autumn. The increased exploitation of the mackerel stock in general and the winter landings of immature fish in particular, have given raise to suggestion of a higher minimum size limit than 20 cm, The question has been considered by the Institute of Marine Research which has proposed to raise the minimum legal size of mackerel for industrial purposes to 30 cm with 25 % allowance of under sized fish. (…)

This new minimum size level has thus been suggested more on a practical basis than on a scientificly founded assessment of the stock. But such a suggestion must in any case has as aim to increase the sustain yield of the stock at the existing level of exploitation” (Revheim and Hamre 1968)

Mackerel Working Group 1974

2. The Effect of Minimum Size Regulation.

“The Working Group considered the effect of the present minimum landing size of 30 cm for mackerel caught for industrial purposes in Division IIIa and Subarea IV.”

“A 33 cm minimum landing size would give practically the same yield per recruit and would give a better condition of the stock than one of 30 cm. For practical reasons, however, 30 cm is preferable. Above a size of 30 cm, mackerel are shoaling with the adult component of the stock and a minimum size limit above 30 cm would be difficult to implement and enforce.” (ICES 1974 p2)

ACFM 1981

“250. Measures to restrict fishing on juvenile mackerel below age 3 would help to restore or keep the spawning stock at the level sufficient to produce average recruitment. Since the growth patterns of mackerel in the North Sea and in the Western area are rather similar, ACFM recommends a minimum landing size of 30 cm for mackerel in all areas.” (ICES 1982)

ACFM 1986

“More general protection could be achieved by adoption of a minimum landing size and ACFM recommends the introduction of a 30-cm limit for mackerel in all areas. If this or some variant (e.g., with an allowed percentage of undersized mackerel) is not feasible, a second option would be to enable the immediate but short-term closure of areas where fisheries on 1- and 2-year-old mackerel develop.” (ICES 1987)

EU 1986/3094 Technical measures Mackerel (Scomber scombrus)

Region 2 North Sea only 30 cm

Region 3 To be determined (Council of the European Union 1986)

ACFM 1987

6.1.2 North Sea mackerel: “The 30-cm minimum landing size at present in force in the North Sea should be maintained and the present by-catch regulations should be continued.”

6.1.3 Western Mackerel: “ACFM reiterates its recommendation that a 30-cm minimum landing size should be implemented in all areas.” (ICES 1988)

Mackerel Working Group 1989

3.5.1 Minimum size regulation

The working Group has again been asked by ACFM to study in detail the practicality of a 30-cm minimum landing size for mackerel. A 30-cm minimum size limit is at present in operation in the North Sea and Division IIa, and ACFM, at its May 1988 meeting, reiterated its recommendation that this minimum size limit should be extended to all areas.

In order to study the landings of fish less than 30 cm, the length distributions per quarter per fleet for as many areas as possible were examined. These length distributions, together with details of the catches, are available in the working Group file. The percentage numbers of fish less than 30 cm were evaluated for as many areas and fleets as possible, and the weighted averages of these percentages are shown in Figures 3.5 - 3.8. The Working Group also had available the length distributions of the Scottish fleets in relation to a proposed 30-cm minimum landing size (Hopkins, working document).

The practicality of adopting a 30-cm minimum landing size throughout all areas was discussed in detail. It was felt that:

1. An examination of the F values of 0- and 1-year-old fish from VPA (Table 3.9) indicates that, in the most the exploitation of juvenile fish has been extremely low even when strong year classes entered the fishery, and would not suggest any need for a minimum landing 2. Apart from the "box" off Cornwall, young fish were also found during 1988 in other areas throughout Divisions VIa south, VIIb, VIIj, and IVb. While this was the pattern in 1988, the Working Group felt it would be unwise to draw conclusions about the distribution of young mackerel below 30 cm based on the length distributions of only one year. This is particularly true because of the continual changes in the distributions of these fish. 3. In general, the percentages of small mackerel are highest in the southern areas. However, even within these areas, there are extreme variations between the amounts of small mackerel landed by different fleets. Very high levels of small mackerel are taken by some fleets, but the landings, when viewed in the context of the total landings of the Western stock, are insignificant. 4. In the northern areas (Sub-areas II and VI), the percentage of small mackerel landed in 1988 was very small. However, the Working Group was aware that, when the strong 1984 year class recruited in 1985, it did not appear in quantity in the landings in the first two quarters in 1985. In the last two quarters, however, considerable quantities were taken particularly by the fleets fishing in the southern part of these areas.

The Working Group drew attention to the inconsistency of enforcing a 30-cm minimum landing size in the North Sea and not in the Western area when the bulk of the catches was taken in Division IVa. The Working Group. therefore, discussed the implications of either enforcing or removing the 30-cm minimum landing size regulation in both areas.

As discussed above, a 30-cm minimum landing size in the Western area does not seem necessary on biological grounds. Part of this argument is based on the low fishing mortality on juveniles. However. it was the view of the Working Group that the fleets were able to avoid areas of juvenile abundance in the North Sea area, and removal of the minimum landing size regulation could lead to higher juvenile fishing mortalities. In the Norwegian fishery, discarding is illegal, so that catches of small fish are slipped and the fleet moves elsewhere.

The introduction of a 30-cm minimum landing size in the Western area could lead to higher discard rates when a large year class enters the fishery. For example, catches of juveniles of the 1984 year class in the winter of 1985-1986 were high. Moreover. Evidence was presented which showed that the percentage of juveniles in the catches during this fishery varied from 0% to over 90% even within a very small area (Hopkins, working document). This suggests that juvenile areas cannot be avoided· and that the effect of a minimum landing size regulation would be to increase the incidence of slippage or discards. Available information from this area indicates a rather high mortality in slipped fish (Lockwood et al 1983). The 1987 year class also appears to be strong, and the percentage of juveniles in the catches may increase in the first quarter of 1989.

Conclusions

The 30-cm minimum size limit was originally introduced in the North Sea by Norway in 1971 and was intended to protect the very strong 1969 year class from exploitation in the industrial fishery. It does not seem necessary to extend this measure to the Western area. The introduction of a 30-cm minimum size in the area in order to make it consistent with similar measures in the North Sea may result in an increase in the quantities of juvenile mackerel which will be slipped or discarded. This would lead to an increase in the exploitation rate on juveniles and a deterioration in the age composition of the stock which is already becoming heavily dependent on incoming year classes. However, it is extremely important that the situation be kept constantly under review because of the changing state of the fisheries and of the delicate nature of the age composition of the stock (ICES 1989).

ACFM 1989

6.1.3 Western Mackerel: “ACFM has recommended various measures for the protection of young mackerel, including a minimum landing size of 30 cm. Such a minimum size is presently in operation in the North Sea area (Sub-area IV, Divisions IIa and IIIa), and ICES was asked to consider the practicality of adopting a 30-cm minimum landing size throughout all areas. In the Western area, juvenile and adult mackerel were found to occur within the same fishing locations, and an introduction of a minimum landing size could lead to a higher discard rate. ACFM, therefore, concluded that there would be no benefit from adopting a 30-cm minimum landing size in the Western area. ACFM finds that the demonstrated effect of the 30 cm minimum landing size (or minimum legal size) in the major fishery in the northern North Sea (Division IVa) ,the Norwegian Sea (Division IIa), and Skagerrak-Kattegat (Division IIIa) justifies the retention of the measure in those areas. (ICES 1990a)

Mackerel Working Group 1990

“Again, as expressed in 1989, the introduction of a 30 cm minimum size for the Western area does not seem necessary on biological grounds and would lead to a higher discard rate when a strong year class enters the fishery.” (ICES 1990b)

ACFM 1990

No specific comments on changes in minimum landing size (ICES 1991a)

Mackerel Working Group 1991

No specific comments on changes in minimum landing size. Serious concerns about discarding of small mackerel because of price difference with large mackerel.

Southern mackerel: “Matters that should be considered might include … the increase in the minimum landing size for mackerel from 15 cm to approximately 25 cm” (ICES 1991b)

ACFM 1991

No specific comments on changes in minimum landing size (ICES 1992a)

COM/91/209

Proposal for a Council Regulation ( EEC ) amending for the twelfth time Regulation ( EEC ) No 3094/86 laying down certain Technical Measures for the conservation of fishery resources. (Commission of the European Communities 1991)

This document is not available on Eur Lex!

WGMHSA 1992

No specific comments on changes in minimum landing size.

Southern Mackerel: “Previous working groups and ACFM have suggested methods for reducing the catches of juveniles. A minimum landing size of 20 cm has now been implemented in both Divisions V111c and IXa.” (ICES 1992b)

ACFM 1992

No specific comments on changes in minimum landing size (ICES 1993b)

EU 1992/345

COUNCIL REGULATION (EEC) No 345 / 92 of 27 January 1992 amending for the eleventh time Regulation (EEC) No 3094 / 86 laying down certain technical measures for the conservation of fishery resources

No underpinning presented of the 20 cm minimum landing size for mackerel. (Council of the European Union 1992)

WGMHSA 1993

No specific comments on the new 20 cm minimum landing size. A comment in the report states that “there appears to be no reason why fishing on the western stock should not be permitted in Divisions IVa and IIa during the third and fourth quarters.” (ICES 1993a)

ACFM 1993

No comments on change in minimum landing size (ICES 1994)

EU 1998/850

Council Regulation (EC) No 850/98 of 30 March 1998 for the conservation of fishery resources through technical measures for the protection of juveniles of marine organisms.

(Council of the European Union 1998)

References

Commission of the European Communities (1991). Proposal for a Council Regulation ( EEC ) amending for the twelfth time Regulation ( EEC ) No 3094/86 laying down certain Technical Measures for the conservation of fishery resources. COM(1991) 209. Council of the European Union (1986). Council Regulation (EEC) No 3094/86 of 7 October 1986 laying down certain technical measures for the conservation of fishery resourcesorganisms. OJ L 288, 11.10.1986. Council of the European Union (1992). Council Regulation (EEC) No 345 / 92 of 27 January 1992 amending for the eleventh time Regulation (EEC) No 3094 / 86 laying down certain technical measures for the conservation of fishery resources. OJ L 42, 18.02.1992. Council of the European Union (1998). Council Regulation (EC) No 850/98 of 30 March 1998 for the conservation of fishery resources through technical measures for the protection of juveniles of marine organisms. OJ L 125, 27.4.1998. ICES (1974). Report of the Mackerel Working Group, 30 January - 1 February 1974. ICES C.M. 1974 / H:2: 20. ICES (1982). Report of the ICES Advisory Committee on Fishery Management, 1981, ICES. Cooperative Research Report no. 114. ICES (1987). Report of the ICES Advisory Committee on Fishery Management, 1986, ICES. Cooperative Research Report no. 146. ICES (1988). Report of the ICES Advisory Committee on Fishery Management, 1987, ICES. Cooperative Research Report no. 153. ICES (1989). Report of the Mackerel Working Group, 27 February - 7 March 1989. ICES C.M. 1989 / Assess: 11: 89. ICES (1990a). Report of the ICES Advisory Committee on Fishery Management, 1989, ICES. Cooperative Research Report no. 168. ICES (1990b). Report of the Mackerel Working Group, 24 april - 2 may 1990. ICES C.M. 1990 / Assess: 19: 113. ICES (1991a). Report of the ICES Advisory Committee on Fishery Management, 1990, ICES. Cooperative Research Report no. 173. ICES (1991b). Report of the Mackerel Working Group, April/May 1991. ICES C.M. 1991 / Asess: 19. ICES (1992a). Report of the ICES Advisory Committee on Fishery Management, 1991, ICES. Cooperative Research Report no. 179. ICES (1992b). Report of the Working Group on the Assessment of Mackerel, Horse Mackerel, Sardine, and Anchovy, June 1992. C.M.1992/Assess:17. ICES (1993a). Report of the Working Group on the Assessment of Mackerel, Horse Mackerel, Sardine, and Anchovy, June/July 1993. C.M.1993/Assess:19. ICES (1993b). Report of the ICES Advisory Committee on Fishery Management, 1992, ICES. Cooperative Research Report no. 193. ICES (1994). Report of the ICES Advisory Committee on Fishery Management, 1993, ICES. Cooperative Research Report no. 196. ICES (2014a). Mackerel in the Northeast Atlantic (combined Southern, Western, and North Sea spawning components), Section 9.3.17b in Advice September 2014.In: Report of the ICES Advisory Committee, 2014, ICES advice, 2014: xxx pp. ICES (2014b). Report of the Working Group on Widely Distributed Stocks (WGWIDE), Copenhagen, 26 August-1 September 2014. ICES C.M. 2014 / ACOM:15. Revheim, A. and J. Hamre (1968). A brief statement on the present state of the Norwegian mackerel fishery, ICES C.M. 1968 / H:24.

Appendix 2 WGWIDE data

NEA Mackerel Variable: Catch in number Units : Thousands Source: WGWIDE 2014, table 2.6.2

Age 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 0 33101 56682 11180 7333 287287 81799 49983 7403 57644 65400 24246 10007 43447 19354 25368 14759 37956 36012 61127 67003 36345 26034 70409 14744 11553 12426 75651 19302 25886 17615 23453 30429 23803 11325 1 411327 276229 213936 47914 31901 268960 58126 40126 152656 64263 140534 58459 83583 128144 147315 81529 119852 144390 99352 73597 102407 40315 222577 187997 31421 46840 149425 88439 59899 36514 78605 62708 66164 46977 2 393025 502365 432867 668909 86064 20893 424563 156670 137635 312739 209848 212521 156292 210319 221489 340898 168882 186481 229767 132994 142898 158943 70041 275661 453133 135648 173646 190857 167748 113574 137101 115346 200064 226179 3 64549 231814 472457 433744 682491 58346 38387 663378 190403 207689 410751 206421 356209 266677 306979 340215 333365 238426 264566 223639 275376 234186 367902 91075 529753 668588 159455 220575 399086 455113 303928 322725 214251 430081 4 328206 32814 184581 373262 387582 445357 76545 56680 538394 167588 208146 375451 266591 398240 267420 275031 279182 378881 323186 261778 390858 297206 350163 295777 147973 293579 470063 215655 284660 616963 739221 469953 416037 342280 5 254172 184867 26544 126533 251503 252217 364119 89003 72914 362469 156742 188623 306143 244285 301346 186855 177667 246781 361945 281041 295516 309937 262716 235052 258177 120538 195594 455131 260314 319465 611729 654395 454147 437248 6 142978 173349 138970 20175 98063 165219 208021 244570 87323 48696 254015 129145 156070 255472 184925 197856 96303 135059 207619 244212 241550 231804 237066 183036 145899 121477 97061 203492 255675 224848 284788 488713 510469 421220 7 145385 116328 112476 90151 22086 62363 126174 150588 201021 58116 42549 197888 113899 149932 189847 142342 119831 84378 118388 159019 175608 195250 151320 133595 89856 63612 73510 77859 124382 194326 143039 244210 323103 338388 8 54778 125548 89672 72031 61813 19562 42569 85863 122496 111251 49698 51077 138458 97746 106108 113413 55812 66504 72745 86739 106291 120241 118870 94168 65669 38763 33399 59652 57297 73171 102072 113012 142390 192725 9 130771 41186 88726 48668 47925 47560 13533 34795 55913 68240 85447 43415 51208 121400 80054 69191 59801 39450 47353 50613 52394 72205 79945 75701 40443 23947 18961 30494 32343 29738 45841 53363 69454 118727 10 39920 146186 27552 49252 37482 37607 32786 19658 20710 32228 33041 70839 36612 38794 57622 42441 25803 26735 24386 30363 31280 42529 43789 45951 35654 18612 13987 16039 19482 14989 21222 25046 30573 46253 11 56210 31639 91743 19745 30105 26965 22971 25747 13178 13904 16587 29743 40956 29067 20407 37960 18353 13950 16551 17048 18918 20546 21611 25797 16430 7955 8334 11416 6798 7470 6255 12311 11648 18932 12 104927 199615 156121 132040 69183 97652 81153 63146 57494 35814 27905 52986 68205 68217 57551 39753 30648 24974 22932 32446 34202 40706 40280 30890 19509 10669 10186 12801 9581 5003 8523 10775 11741 17856

NEA Mackerel Variable: Weight in the catch Units : kg Source: WGWIDE 2014, table 2.6.3

age 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 0 0.057 0.06 0.053 0.05 0.031 0.055 0.039 0.076 0.055 0.049 0.085 0.068 0.051 0.061 0.046 0.072 0.058 0.076 0.065 0.062 0.063 0.069 0.052 0.081 0.067 0.048 0.038 0.089 0.051 0.104 0.048 0.029 0.089 0.091 1 0.131 0.132 0.131 0.168 0.102 0.144 0.146 0.179 0.133 0.136 0.156 0.156 0.167 0.134 0.136 0.143 0.143 0.143 0.157 0.176 0.135 0.172 0.16 0.17 0.156 0.151 0.071 0.12 0.105 0.153 0.118 0.113 0.123 0.173 2 0.249 0.248 0.249 0.219 0.184 0.262 0.245 0.223 0.259 0.237 0.233 0.253 0.239 0.24 0.255 0.234 0.226 0.23 0.227 0.235 0.227 0.224 0.256 0.267 0.263 0.268 0.197 0.215 0.222 0.213 0.221 0.231 0.187 0.234 3 0.285 0.287 0.285 0.276 0.295 0.357 0.335 0.318 0.323 0.32 0.336 0.327 0.333 0.317 0.339 0.333 0.313 0.295 0.31 0.306 0.306 0.305 0.307 0.336 0.323 0.306 0.307 0.292 0.292 0.283 0.291 0.282 0.285 0.281 4 0.345 0.344 0.345 0.31 0.326 0.418 0.423 0.399 0.388 0.377 0.379 0.394 0.397 0.376 0.39 0.39 0.377 0.359 0.354 0.361 0.363 0.376 0.368 0.385 0.4 0.366 0.357 0.372 0.37 0.331 0.331 0.334 0.34 0.333 5 0.378 0.377 0.378 0.386 0.344 0.417 0.471 0.474 0.456 0.433 0.423 0.423 0.46 0.436 0.448 0.452 0.425 0.415 0.408 0.404 0.427 0.424 0.424 0.438 0.419 0.434 0.428 0.408 0.418 0.389 0.365 0.368 0.374 0.359 6 0.454 0.454 0.454 0.425 0.431 0.436 0.444 0.512 0.524 0.456 0.467 0.469 0.495 0.483 0.512 0.501 0.484 0.453 0.452 0.452 0.463 0.474 0.461 0.477 0.485 0.44 0.479 0.456 0.444 0.424 0.418 0.411 0.401 0.386 7 0.498 0.499 0.496 0.435 0.542 0.521 0.457 0.493 0.555 0.543 0.528 0.506 0.532 0.527 0.543 0.539 0.518 0.481 0.462 0.5 0.501 0.496 0.512 0.522 0.519 0.496 0.494 0.512 0.497 0.45 0.471 0.451 0.431 0.406 8 0.52 0.513 0.513 0.498 0.48 0.555 0.543 0.498 0.555 0.592 0.552 0.554 0.555 0.548 0.59 0.577 0.551 0.524 0.518 0.536 0.534 0.54 0.536 0.572 0.554 0.539 0.543 0.534 0.551 0.497 0.487 0.494 0.468 0.428 9 0.542 0.543 0.541 0.545 0.569 0.564 0.591 0.58 0.562 0.578 0.606 0.609 0.597 0.583 0.583 0.594 0.576 0.553 0.55 0.569 0.567 0.577 0.58 0.612 0.573 0.556 0.584 0.573 0.571 0.538 0.515 0.54 0.503 0.457 10 0.574 0.573 0.574 0.606 0.628 0.629 0.552 0.634 0.613 0.581 0.606 0.63 0.651 0.595 0.627 0.606 0.596 0.577 0.573 0.586 0.586 0.603 0.6 0.631 0.595 0.583 0.625 0.571 0.62 0.586 0.573 0.58 0.537 0.472 11 0.59 0.576 0.574 0.608 0.636 0.679 0.694 0.635 0.624 0.648 0.591 0.649 0.663 0.647 0.678 0.631 0.603 0.591 0.591 0.607 0.594 0.611 0.629 0.648 0.63 0.632 0.636 0.585 0.595 0.599 0.604 0.611 0.538 0.493 12 0.58 0.584 0.582 0.614 0.663 0.71 0.688 0.718 0.697 0.739 0.713 0.708 0.669 0.679 0.713 0.672 0.67 0.636 0.631 0.687 0.644 0.666 0.665 0.715 0.684 0.655 0.689 0.666 0.662 0.63 0.63 0.664 0.585 0.554

NEA Mackerel Variable: Proportion mature Units : % Source: WGWIDE 2014, table 2.6.6

age 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0.105 0.109 0.11 0.111 0.116 0.116 0.116 0.116 0.116 0.116 0.116 0.116 0.116 0.116 0.116 0.116 0.116 0.109 0.109 0.109 0.118 0.118 0.118 0.12 0.12 0.12 0.107 0.107 0.107 0.108 0.108 0.108 0.105 0.105 2 0.487 0.503 0.511 0.532 0.486 0.487 0.497 0.412 0.404 0.419 0.406 0.466 0.523 0.558 0.607 0.573 0.588 0.608 0.626 0.606 0.637 0.632 0.696 0.705 0.719 0.704 0.68 0.61 0.588 0.585 0.547 0.545 0.527 0.546 3 0.84 0.817 0.877 0.88 0.871 0.888 0.923 0.924 0.917 0.916 0.913 0.92 0.93 0.936 0.941 0.922 0.916 0.859 0.873 0.874 0.906 0.909 0.944 0.939 0.94 0.941 0.913 0.905 0.91 0.912 0.909 0.912 0.91 0.916 4 0.933 0.919 0.934 0.97 0.968 0.967 0.989 0.99 0.99 0.993 0.994 0.993 0.995 0.996 0.997 0.996 0.997 0.987 0.988 0.988 0.987 0.984 0.994 0.99 0.99 0.991 0.994 0.994 0.996 0.997 0.997 0.997 0.997 0.999 5 0.963 0.971 0.97 0.991 0.988 0.988 0.99 0.996 0.994 0.999 0.999 0.998 0.998 0.999 0.999 0.999 1 0.997 0.997 0.997 0.997 0.996 0.999 0.999 0.998 0.998 0.999 0.999 0.998 1 0.999 0.999 0.999 1 6 0.98 0.978 0.98 0.995 0.996 0.994 0.997 0.997 0.997 0.998 1 0.998 0.996 0.996 0.996 0.996 0.998 0.998 0.998 0.999 0.998 0.998 0.999 0.999 0.999 0.999 1 1 1 1 0.999 0.999 0.999 0.999 7 0.983 0.98 0.979 0.994 0.994 0.996 1 1 1 1 1 1 0.999 0.999 0.999 0.999 0.999 1 1 1 1 0.999 0.999 0.999 0.999 0.999 1 1 1 1 1 1 1 1 8 1 0.999 0.999 0.998 0.998 0.997 0.997 0.997 0.997 0.997 0.998 1 1 1 1 1 1 0.998 0.998 0.998 0.998 0.999 1 1 1 1 1 1 1 1 1 1 1 1 9 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 10 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 12 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

NEA Mackerel Variable: Catch in number Units : Thousands Source: WGWIDE 2014, table 2.6.2, 2.6.3 and 2.6.6

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Catch weight 734950 754045 716987 672283 641928 614371 602201 654991 680491 585920 626107 675665 760690 824568 819087 756277 563471 573029 666316 640452 738762 737544 773900 679219 685185 550450 481247 590035 623361 740451 878144 948250 895116 931666 Mature catch weight 618020 638170 615200 577576 590653 562493 537021 610605 630392 525503 563021 631495 718833 779209 770943 701022 521158 522897 616443 602142 702022 707334 725982 624923 635418 519641 452602 556051 589954 711649 845895 920003 861723 888905 %mature catch weight 84% 85% 86% 86% 92% 92% 89% 93% 93% 90% 90% 93% 94% 94% 94% 93% 92% 91% 93% 94% 95% 96% 94% 92% 93% 94% 94% 94% 95% 96% 96% 97% 96% 95%

Catch numbers 2159349 2118622 2046825 2089757 2093485 1584500 1538930 1637627 1707781 1548397 1659509 1626575 1817673 2027647 1966431 1882243 1523455 1622021 1849917 1660492 1903643 1789902 2036689 1689444 1845470 1562654 1479272 1601712 1703151 2108789 2505777 2602986 2473844 2648191 Mature catch numbers 1509435 1509438 1557248 1661607 1629650 1228665 1215818 1450300 1410904 1225075 1349141 1431627 1598169 1781976 1703646 1621091 1280818 1344570 1575210 1442934 1692554 1641734 1725320 1418878 1644919 1426342 1197729 1406296 1517086 1969569 2319330 2433186 2274699 2455246 %mature catch numbers 70% 71% 76% 80% 78% 78% 79% 89% 83% 79% 81% 88% 88% 88% 87% 86% 84% 83% 85% 87% 89% 92% 85% 84% 89% 91% 81% 88% 89% 93% 93% 93% 92% 93%