ICES advice for 2018: widely distributed pelagic stocks. Carmen Fernández, ICES ACOM vice-chair For PelAC (The Hague, October 4, 2017)

ICES advice for 2018: widely distributed pelagic stocks Carmen Fernández, ICES ACOM vice-chair For PelAC (The Hague, October 4, 2017)

Basis of ICES Advice Management Basis Plan for / ICES Strategy Advice Consistent with Precautionary Approach & agreed by competent authorities as potential basis for advice No ICES MSY approach No ICES PA approach

Basis of ICES Advice Stock categories (based on available knowledge) 1 Stocks with an accepted analytical assessment and forecast 2 Stocks with an analytical assessment and forecast accepted for trends only 3 Stocks with abundance or biomass indices indicative trends Advice basis MSY approach MSY approach Precautionary approach MSY approach being developed 4 Stocks with reliable catch and biological data Precautionary approach MSY approach being developed 5 Only landings available Precautionary approach 6 Only landings available and largely discarded Precautionary approach

ICES MSY approach (Category 1 stocks) Maximize long term average yield Safeguard against low SSB Stay within precautionary boundaries (WKMSYREF 2, 3 & 4, 2014-15) ICES MSY Advice Rule (AR): more caution below B lim F MSY B trigger F MSY SSB at start of advisory year

Advice framework for stocks in categories 3-6 Implemented since 2012 Various approaches depending on available information Advice Rules providing quantitative advice are available for all stock categories ICES MSY approach for Category 1 stocks

Category 3 (stocks with abundance index) Advice based on previous advice ICES [or recent MSY catch approach or landings], modified according to index information; typically last 5-year index trend: Advice = previous advice x also incorporating: average of index in last 2 years average of index in 3 previous years 1. Uncertainty cap (20% change limit, to dampen noise) 2. Precautionary buffer (20% reduction if status in relation to reference points unknown --- exceptions if significant increases in stock size or reductions in exploitation) o Advice normally does not change every year

Advice framework for stocks in categories 3-6 Now in the process of developing MSY proxy reference points for stocks in categories 3 & 4 ICES MSY approach for Category 1 stocks

Catch advice o ICES advice: A. if discards can be quantified catch advice ICES MSY approach B. if discards unknown (possibly qualitative information) catch advice if information indicates discard rate < 5% (discards negligible in the context of precision of advice) landings advice if information very uncertain or discard rate considered to be > 5%

Terminology: Wanted & Unwanted catch For stocks starting EU landing obligation: ICES MSY approach To provide clear linkage to previous advice on catch and landings the advised catches are split into two components, termed wanted catch and unwanted catch. o Wanted catch is used to describe fish that would be landed in the absence of the EU landing obligation o Unwanted catch refers to the component that was previously discarded. This split, based on the past performance of the fishery, is expected to evolve and the relative magnitude of the components will change, e.g. after some years of LO data, we may have: landings wanted, landings unwanted, discards

Advice format For each ecoregion: New structure of advice: o Stock advice (new format implemented last year: shorter and more directly focussed on the catch advice) o Fisheries advice / overviews (being developed) o Ecosystem advice / overviews (being developed)

All advice available online at: Click on http://www.ices.dk Follow Advisory process Latest advice In addition to advice items, Introduction to ICES Advice document describes principles and advice basis For advice release dates, follow link: Follow Advisory process Advice requests and advice release dates Email contact (e.g. to enquire about workshops, registration to workshops...): advice@ices.dk

Widely distributed stocks

Blue whiting in Subareas 1-9, 12, 14 Advice for 2018, LTMS of EU, Faroes, Iceland and Norway: Catch 1 387 872 t * SSB above MSY B trigger * F above F MSY * Recent recruitment above average, but low in 2017 * LTMS evaluated and found precautionary F (TAC yr) LTMS SSB (Jan 1, TAC yr) o TAC constraint (20% down, 25% up) applied if SSB(TAC yr) and SSB(TAC yr 1) are B pa & the change in TAC is 40%

Blue whiting in Subareas 1-9, 12, 14 Catch 2016: 1.183 million t Discard ratio is < 0.5 % Landings: 98% pelagic trawl, 2% bottom trawl Main fisheries target spawning and post-spawning fish. ~ 90% of catch taken in first two quarters of the year 2 500 000 2 000 000 1 500 000 1 000 000 500 000 Total southern areas (SAs8+9;Divs.7.d-k) Directed- and mixed fisheries in the North Sea (SA4; Div.3.a) Fishery in the spawning area (SA 12.; Divs. 5.b, 6.a-b, 7.a-c) Norwegian Sea fishery (SAs1+2;Divs.5.a,14a-b) 0

Blue whiting in Subareas 1-9, 12, 14 Assumptions 2017: Catch = 1.559 million t (based on declared quotas and expected uptake) SSB(2018)= 5.907 million t > MSY B trigger (2.25 million t) ICES advice basis Basis Catch (2018) tonnes * Catch(2018) relative to estimated catch in 2017 (1.559 million t) F(2018) SSB (2019) tonnes % SSB change 2019 vs 18 Likely decrease in stock size and fishing opportunities when the low 2016 year class is fully in the fishery, from 2019 % Catch change ** Long-term management strategy (F = F MSY ) 1 387 872 0.32 5 181 388 12 11 Other options MSY approach: F MSY 1 387 872 0.32 5 181 388 12 11 F = 0 0 0 6 509 015 10 100 F pa 2 116 435 0.53 4 491 803 24 36 F lim 3 088 351 0.88 3 582 582 39 98 SSB (2019) = B lim 5 410 452 2.51 1 500 131 75 247 SSB (2019) = B pa 4 546 226 1.68 2 253 487 62 192 SSB (2019) = MSY B trigger 4 546 226 1.68 2 253 487 62 192 F = F 2017 1 688 386 0.40 4 896 239 17 8 SSB (2019) = SSB (2018) 631 861 0.135 5 902 594 0 59 Catch (2019) = Catch (2018) 1 554 741 0.37 5 022 934 15 0

Norwegian spring-spawning herring (Subareas 1, 2, 5, & Divisions 4a, 14a) Advice for 2018, EU, Faroes, Iceland, Norway, Russia MP: Catch 546 472 t * SSB declining, now below MSY B trigger * F below F MSY * Last large recruitment (age 2) was 2006 Re-evaluation of reference points and LTMP to take place before the WG in 2018

Norwegian spring-spawning herring (Subareas 1, 2, 5, & Divisions 4a, 14a) Catch 2016: 383 kt Discarding negligible Landings: ~49% purse seine, ~51% pelagic trawl 2016 fishery had similar pattern to recent years Q1: Fishery began in January on Norwegian shelf (overwintering, pre-spawning, spawning and post-spawning fish) Q2: fishery insignificant Q3: Faroese, Icelandic and Greenlandic waters Q4: Central part of Norwegian Sea and overwintering area in fjords and oceanic areas north of Tromsø 52% of catches taken in Q4

Norwegian spring-spawning herring (Subareas 1, 2, 5, & Divisions 4a, 14a) Assumptions 2017: Catch = 805 kt (based on declared quotas) SSB(2018)= 4.364 million t < MSY B trigger (5 million t) Basis Catch (2018) tonnes F W (2018) SSB (2019) tonnes % SSB change 2019 vs 18 % Catch change * ICES advice basis Agreed management plan^ 546 472 0.106 4 132 000 5 32 Other options MSY approach: F MSY SSB(2018)/MSY B trigger 665 779 0.131 4 028 000 8 17 F MSY 754 509 0.15 3 950 000 9 6 F = 0 0 0 4 613 000 6 100 F pa 754 509 0.15 3 950 000 9 6 SSB (2019) = B lim 2 437 455 0.624 2 500 000 43 203 SSB (2019) = B pa = MSY B trigger ^^ --- 5 000 000 --- --- F = F 2017 813 228 0.163 3 899 000 11 1 * Catch(2018) relative to estimated catch in 2017 (805 kt) ^ Because SSB(2018) is between Bpa and Blim, F in 2018 is obtained from a straight line between F=0.125 at SSB=Bpa and F=0.05 at SSB=Blim. ^^ Even with zero catch in 2018 the stock is predicted to be below Bpa and MSY Btrigger in 2019

Horse mackerel (Trachurus trachurus) North Sea stock: 3a, 4bc, 7d Western stock: 2a, 4a, 5b, 6a, 7 (exc. 7d), 8 Catch in Divisions 3a and 4a: Q1 & Q2: allocated to North Sea stock Q3 & Q4: allocated to Western stock Southern stock: 9a

North Sea horse mackerel Advice for 2018 and 2019, Precautionary approach: Catch in each year 17 517 t complete discard estimates only in some years o Discarding in target pelagic fisheries considered negligible o Information from bottom trawl fisheries not directed to horse mackerel indicates discarding (average discarding in 2015-2016 ~ 13% of total stock catches). Discarding in earlier years expected to have been similar. * Benchmarked in 2017, now Category 3: Stock abundance index combining CGFS (Q4 in 7d) and NS-IBTS (Q3 in 4bc) * The stock remains at a low level, with some signs of improvement F in 2016 above the F MSY proxy

North Sea horse mackerel o Catch (2016) = 15 341 t (10% discarded, non-directed fisheries) Advice follows approach for Category 3 stocks Index A (average of 2015-2016) 692 indv/hour Index B (average of 2012-2014) 254 indv/hour Ratio (A/B) 2.7 Uncertainty cap Applied 1.2 Precautionary buffer Applied 0.8 Advised catch for 2017 18 247 tonnes Catch advice for each of 2018 and 2019* 17 517 tonnes Discard rate (average 2015-2016) 13.35% Landings corresponding to the catch advice** 15 179 tonnes * [Advised catch for 2017] [uncertainty cap] [precautionary buffer]. ** [Catch advice] [1 discard rate]. o Precautionary buffer (20% reduction) last applied in 2014 o F currently above the F MSY proxy Precautionary buffer is applied this year Since 2013, signals of better recruitment, specially in Division 7d Fisheries focussed on smaller fish in 2015 and 2016. This exploitation pattern, catching mostly immature individuals, might hinder stock recovery.

Mackerel in Northeast Atlantic Advice for 2018, MSY approach: Catch 550 948 t Existing measures to protect North Sea spawning component should remain in place * SSB above MSY B trigger * F above F MSY * Several large year classes since 2002 Benchmarked in 2017: o Modifications to IESSNS indices and how assessment deals with it o Ages 3-11 of IESSNS now in assessment o Additional tagging data (fish released since 2011) now in assessment o Tagging data were revised o Reference points updated: B lim = 1.94 million t B pa and MSY B trigger = 2.57 million t F lim = 0.48, F pa = 0.35, F MSY = 0.21

Mackerel in Northeast Atlantic Overall stock perception similar to previous assessment, but lower estimates of SSB and higher estimates of F in recent years

Mackerel in Northeast Atlantic Catch 2016: 1.094 million t Discard ratio is < 1 % Landings: ~78% pelagic trawl, ~20% purse seine, ~2% others Quarter 1 Quarter 2 Geographical expansion of the northern summer fishery in recent years. Quarter 3 Quarter 4 Since 2010, close to half of the catch taken in Q3

Mackerel in Northeast Atlantic Assumptions 2017: Catch = 1.179 million t (based on declared quotas & interannual transfers) Basis Catch (2018) tonnes F 4-8 (2018 and 2019) * Catch(2018) relative to estimated catch in 2017 (1.179 million t) SSB (2018), t Spawning time SSB (2019), t Spawning time % SSB change 2019 vs 2018 % Catch change * ICES advice basis MSY approach: F MSY 550 948 0.21 3 123 519 3 162 312 1.2-53 Other options F = 0 0 0 3 213 067 3 698 314 15-100 F pa 864 415 0.35 3 065 670 2 867 908-6.5-27 F lim 1 122 906 0.48 3 013 235 2 631 351-13 -4.7 SSB(2019) = B lim 1 915 301 1.0 2 815 222 1 944 804-31 62 SSB(2019) = MSY B trigger = B pa 1 196 775 0.52 2 997 345 2 564 830-14 1.5 F = F2017 977 765 0.405 3 043 254 2 763 463-9.2-17 Catch(2018) = Catch(2017) - 20% 943 080 0.39 3 050 205 2 795 307-8.4-20 Catch(2018) = Catch(2017) 1 178 850 0.51 3 001 241 2 580 927-14 0.0 Catch(2018) = Catch(2017) + 20% 1 414 620 0.65 2 947 809 2 371 562-20 20 F = 0.20 527 025 0.20 3 127 707 3 185 107 1.8-55 F = 0.22 574 658 0.22 3 119 338 3 139 767 0.7-51 F = 0.23 598 156 0.23 3 115 166 3 117 466 0.1-49 F = 0.24 621 445 0.24 3 111 000 3 095 407-0.5-47 F = 0.25 644 527 0.25 3 106 842 3 073 588-1.1-45 F = 0.26 667 404 0.26 3 102 692 3 052 005-1.6-43 F = 0.27 690 078 0.27 3 098 548 3 030 654-2.2-41 F = 0.28 712 551 0.28 3 094 413 3 009 535-2.7-40 F = 0.29 734 825 0.29 3 090 285 2 988 642-3.3-38 F = 0.30 756 903 0.30 3 086 164 2 967 975-3.8-36

Norway, EU, Faroes request to evaluate LTMS for mackerel Request to evaluate rules of the following form: F F target B trigger SSB(spawning time, TAC yr) o Range of Btrigger between 2 and 5 million tonnes and appropriate range of F targets o All rules tested without and with interannual TAC limit, of the following form: If SSB(spawing time, TAC yr) Btrigger interannual TAC limit: 20% down and 25% up o Rules tested with fixed weights-at-age and density-dependent weights-at-age

Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during 2011-2015, i.e. low No TAC constraint: Long-term yield (median value) for different (Ftarget, Btrigger) combinations, identifying combinations that are precautionary and result in highest long-term yield on average: Btrigger 0.1 0.13 0.15 0.16 0.17 0.18 0.19 0.2 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 0.29 0.3 0.31 0.32 0.33 0.34 0.35 600 557 618 647 658 668 677 684 691 696 699 702 703 703 703 702 701 699 696 693 688 684 679 674 1940 557 618 647 659 669 678 685 691 697 701 704 706 706 707 707 707 706 705 703 700 697 694 691 2000 557 618 647 659 669 678 685 692 697 701 704 706 707 708 708 707 706 706 704 702 699 696 694 2200 557 618 647 659 669 678 686 692 698 702 705 708 710 711 711 711 711 710 709 707 706 705 703 2400 557 618 647 660 670 679 687 693 699 703 708 711 713 715 716 717 717 715 716 716 715 714 714 2570 557 618 648 660 670 680 688 695 700 706 709 714 717 719 721 722 723 723 723 724 724 724 723 2600 557 618 648 661 671 680 688 695 701 706 710 715 718 720 721 723 724 724 725 725 725 726 724 2800 557 619 649 662 672 682 690 697 703 709 714 719 723 725 727 730 732 733 734 735 735 735 734 3000 557 619 649 663 674 684 693 701 707 714 719 724 728 732 735 738 740 741 742 741 740 737 732 3200 557 620 651 664 676 686 696 704 711 719 724 729 734 739 743 744 746 746 745 742 738 731 724 3400 558 621 653 666 678 689 699 708 716 724 730 736 741 745 747 747 747 744 739 734 727 721 713 3600 558 623 655 668 681 693 704 714 722 730 736 742 746 747 745 743 741 735 729 723 716 709 701 3800 559 624 657 671 685 698 709 719 728 735 740 744 744 743 740 735 730 724 718 712 706 700 693 4000 560 627 660 675 689 702 714 724 731 735 738 738 736 732 727 721 717 712 707 702 697 692 687 4200 561 629 663 679 693 706 717 725 730 731 730 728 723 720 714 710 706 702 697 694 690 685 681 4400 562 631 667 683 697 708 716 721 722 721 718 714 710 706 702 700 696 694 690 687 683 680 675 4600 564 634 670 685 698 706 711 711 710 707 705 702 699 695 693 690 688 687 683 680 677 675 672 4800 566 637 672 684 694 698 698 698 697 696 694 692 689 685 685 682 681 679 676 674 672 670 667 5000 568 639 670 679 684 685 686 685 685 685 684 683 680 678 677 676 674 673 671 668 667 665 664

Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during 2011-2015, i.e. low TAC constraint: Long-term yield (median value) for different (Ftarget, Btrigger) combinations, identifying combinations that are precautionary and result in highest long-term yield on average: Btrigger 0.1 0.13 0.15 0.16 0.17 0.18 0.19 0.2 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 0.29 0.3 0.31 0.33 0.34 0.35 600 557 619 648 661 672 681 689 695 699 703 706 706 707 706 707 703 700 692 690 680 675 669 1940 558 620 650 663 674 683 692 698 703 708 712 715 717 718 718 719 718 718 717 713 711 709 2000 558 620 650 663 674 684 692 698 703 709 712 716 718 719 719 720 719 720 717 715 713 710 2200 558 621 651 664 675 685 693 700 705 710 715 719 721 721 722 722 723 722 721 719 716 711 2400 558 621 651 664 676 685 694 701 707 712 717 720 723 724 725 726 725 724 722 718 714 709 2570 558 621 652 665 676 687 695 703 709 714 718 722 723 725 726 725 724 723 721 716 713 708 2600 558 621 652 665 676 687 696 703 709 714 718 722 724 725 727 725 723 722 721 716 713 707 2800 559 622 653 667 678 688 697 704 710 715 720 722 724 725 724 723 723 722 720 713 711 710 3000 559 623 654 667 679 690 697 704 710 715 719 721 724 724 722 721 721 720 718 713 711 711 3200 559 623 655 668 679 688 697 704 711 715 718 720 721 722 720 719 719 719 718 714 712 711 3400 559 624 655 668 679 688 696 703 708 711 715 716 717 718 720 719 718 719 719 717 714 713 3600 560 624 654 667 678 687 695 701 705 709 712 713 716 717 719 718 718 719 719 716 716 714 3800 560 623 654 666 677 685 692 697 702 706 711 712 713 716 718 720 719 720 719 716 715 712 4000 560 623 653 664 674 682 689 695 701 706 710 711 712 715 715 716 717 718 718 716 713 710 4200 559 622 650 662 671 679 686 693 699 704 706 709 711 713 713 714 715 716 715 712 709 707 4400 559 620 647 658 667 676 683 689 695 699 704 707 709 710 711 710 710 710 710 707 707 705 4600 559 617 643 654 664 672 679 685 691 696 699 703 704 706 705 705 706 705 705 704 702 699 4800 558 613 640 650 661 668 676 682 688 692 696 699 700 700 701 701 700 701 701 698 695 693 5000 556 610 636 647 656 663 672 679 683 686 691 693 694 694 696 695 695 695 694 692 691 690

Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during 2011-2015, i.e. low No TAC constraint: Interannual variability in TAC (median long-term value): increasing the Ftarget or the Btrigger results in higher interannual variability in TAC: Btrigger 0.1 0.13 0.15 0.16 0.17 0.18 0.19 0.2 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 0.29 0.3 0.31 0.32 0.33 0.34 0.35 600 17 18 18 18 18 18 19 19 19 19 19 20 20 20 20 20 21 21 21 21 21 22 22 1940 17 18 18 18 18 19 19 19 20 20 20 20 21 21 21 22 22 22 23 23 24 24 24 2000 17 18 18 18 19 19 19 19 20 20 20 20 21 21 21 22 22 23 23 23 24 24 25 2200 17 18 18 18 19 19 19 19 20 20 20 21 21 21 22 22 23 23 23 24 24 25 25 2400 17 18 18 19 19 19 19 20 20 20 21 21 22 22 22 23 23 24 24 25 25 26 26 2570 17 18 18 19 19 19 20 20 20 21 21 22 22 22 23 23 24 25 25 26 26 27 27 2600 17 18 18 19 19 19 20 20 20 21 21 22 22 23 23 24 24 25 25 26 26 27 27 2800 17 18 19 19 19 20 20 21 21 21 22 22 23 23 24 24 25 26 26 26 27 27 28 3000 17 18 19 19 20 20 21 21 21 22 22 23 24 24 25 25 26 26 27 27 28 28 29 3200 17 18 19 20 20 21 21 22 22 23 23 24 24 25 26 26 27 27 28 28 29 29 30 3400 18 19 20 20 21 21 22 22 23 23 24 25 25 26 26 27 28 28 29 29 30 30 31 3600 18 19 20 21 21 22 22 23 24 24 25 25 26 27 27 28 28 29 29 30 30 31 31 3800 18 19 21 21 22 23 23 24 24 25 26 26 27 27 28 29 29 30 30 31 31 32 32 4000 18 20 21 22 23 23 24 25 25 26 26 27 28 28 29 29 30 30 31 32 32 32 33 4200 19 21 22 23 23 24 25 25 26 26 27 28 28 29 30 30 31 31 32 32 32 33 33 4400 19 21 23 23 24 25 25 26 27 27 28 28 29 30 30 31 31 32 32 33 33 33 34 4600 20 22 23 24 25 25 26 27 27 28 28 29 30 30 31 31 32 32 33 33 33 34 34 4800 20 22 24 24 25 26 27 27 28 28 29 30 30 31 31 32 32 33 33 33 34 34 35 5000 21 23 24 25 26 27 27 28 28 29 30 30 31 31 32 32 33 33 33 34 34 35 35

Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during 2011-2015, i.e. low TAC constraint: Interannual variability in TAC (median long-term value): increasing the Ftarget or the Btrigger results in higher interannual variability in TAC: Btrigger 0.1 0.13 0.15 0.16 0.17 0.18 0.19 0.2 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 0.29 0.3 0.31 0.32 0.33 0.34 0.35 600 17 18 19 19 19 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 1940 18 18 19 19 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 2000 18 18 19 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 2200 18 19 19 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 21 22 23 2400 18 19 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 21 22 24 25 25 2570 18 19 20 20 20 20 20 20 20 20 20 20 20 20 20 20 21 23 23 25 25 25 25 2600 18 19 20 20 20 20 20 20 20 20 20 20 20 20 20 20 22 23 24 25 25 25 25 2800 18 19 20 20 20 20 20 20 20 20 20 20 20 20 22 23 24 25 25 25 25 25 25 3000 18 19 20 20 20 20 20 20 20 20 20 20 21 23 24 25 25 25 25 25 25 25 25 3200 18 20 20 20 20 20 20 20 20 20 21 22 23 24 25 25 25 25 25 25 25 25 25 3400 19 20 20 20 20 20 20 20 20 22 23 24 25 25 25 25 25 25 25 25 25 25 25 3600 19 20 20 20 20 20 20 21 22 23 25 25 25 25 25 25 25 25 25 25 25 25 25 3800 19 20 20 20 20 20 22 23 24 25 25 25 25 25 25 25 25 25 25 25 25 25 25 4000 20 20 20 20 21 22 23 24 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 4200 20 20 20 21 22 24 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 4400 20 20 21 22 24 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 4600 20 20 23 24 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 4800 20 21 24 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 5000 20 22 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 25 26

Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during 2011-2015, i.e. low For any given (Ftarget, Btrigger) combination, the effect of incorporating the TAC constraint is minor: o The difference in median long-term yield with or without constraint never exceeds 5%. o For most (Ftarget, Btrigger) combinations, both the probability of SSB falling below Blim and the interannual yield variability are somewhat lower with TAC constraint than without it. With the TAC constraint, the catch could get trapped at a low level if the stock is forecast to be below Btrigger in one year: o When the stock is forecast to drop below Btrigger, the catch could potentially experience a big decrease because the TAC constraint would no longer apply. o Once the stock recovered above Btrigger, the 25% constraint on TAC increase could lead to a loss in potential catch because of the constraint on the TAC increase being applied to a low starting point. Discontinuities in advice rules are in general not desirable and it could be useful to consider ways of achieving a smoother transition around Btrigger.

Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during 2011-2015, i.e. low For any given (F target, B trigger ) combination, a wide range of yield and interannual yield variability values may occur in the future. Future values could be quite different from the medians reported in the tables. The range of possible future values widens as the F target increases. For interannual yield variability the range widens considerably with increases in either the F target or the B trigger ; in such cases interannual yield variability values that are much higher than the medians reported in the tables cannot be ruled out.

Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during 2011-2015, i.e. low Simulated distribution of long-term yield vs F target (each column is a value of Btrigger):

Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during 2011-2015, i.e. low Simulated distribution of long-term interannual yield variability vs F target (each column is a value of Btrigger):

Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during 2011-2015, i.e. low TAC constraint Simulated distribution of SSB, Catch and F in years 2018-2052 (each column is an (Ftarget,Btrigger) combination) and 1 particular realisation:

Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Density-dependent weights-at-age: Better scientific understanding of the link between stock size and growth and the development of an appropriate modelling approach would be needed before changes in growth can be incorporated in the evaluation of the harvest control rule. The simulations conducted by ICES with density-dependent weights are for illustrative purposes. They indicate the likely direction of impacts of density dependent growth on the performance of an HCR. According to the simulations conducted: Under density-dependence: o It would be possible to have higher target Fs while remaining precautionary. o Likely some loss in yield if the management strategy is based on recent low weights but the losses in yield relatively minor in the medium and long term. If, on the contrary, the mackerel weights remain at current low values: o A management strategy based on an assumption of density dependence would not be precautionary, i.e. it would result in greater than 5% probability of the stock going below B lim

Horse mackerel (Trachurus trachurus) North Sea stock: 3a, 4bc, 7d Western stock: 2a, 4a, 5b, 6a, 7 (exc. 7d), 8 Catch in Divisions 3a and 4a: Q1 & Q2: allocated to North Sea stock Q3 & Q4: allocated to Western stock Southern stock: 9a

Western horse mackerel Advice for 2018, MSY approach: Catch 117 070 t * Dependent on occasional high recruitment * Recruitment since 2002 low, but a bit higher in last 3 years * SSB currently at lowest observed * F has increased after 2007, presently below F MSY Benchmarked in 2017: o New assessment model (Stock Synthesis) o Uses age and length data o Tuning data: triennial egg survey, recruitment (age 0) index from IBTS, acoustic survey from Division 8c o New reference points

Western horse mackerel Overall perception of stock trends similar to previous assessment, but higher estimates of SSB and lower estimates of F in recent years The inclusion of 2016 data (in WGWIDE this year) increased the absolute biomass estimate for the last decade relative to the benchmark assessment, indicating that there is still considerable uncertainty in this assessment

Western horse mackerel Catch(2016) = 98 810 t (~ 4% discarded) Assumptions 2017: Catch = 95 500 (EU TAC) SSB(2018)= 818 082 t < MSY B trigger (911 587 t) Basis Catch (2018) F total (2018) SSB (2019) ICES advice basis %SSB change 2019 vs 2018 % Advice change * MSY approach: F MSY SSB(2018)/MSY B trigger 117 070 0.097 896 248 9.55 69.21 Other options F = 0 0 0.00 996 723 21.84-100 F = F MSY = F pa 129 703 0.108 885 460 8.24 87.47 F = F lim 177 493 0.151 844 756 3.26 156.54 SSB (2019) = B lim 394 869 0.38 661 917-19.09 470.74 SSB (2019) = MSY B trigger =B pa 99 130 0.081 911 587 11.43 43.28 F = F 2017 102 253 0.084 908 915 11.10 47.79 * Catch(2018) relative to the ICES advised catch for 2017 (69 186 t)

Southern horse mackerel Advice for 2018, MSY approach: Catch 55 555 t. * F below F MSY and SSB above MSY B trigger over whole time series * Recruitment in 2011-2015 above average Catch(2016) = 40 730 t (~ 47% purse-seine, 47% trawl, 6% other gears; discarding negligible) Benchmarked in 2017: o No significant change in overall stock perception o No changes to the reference points

Southern horse mackerel

Assumptions 2017: F(2017) = F(2016) Basis Southern horse mackerel Catch (2018) T. trachurus F (2018) SSB (2018) spawning time * Catch(2017) relative to the ICES estimated catch in 2016 (40 730 t) SSB (2019) spawning time % SSB change 2019 vs 2018 % Catch change* ICES advice basis MSY approach: F MSY 55 555 0.11 487 407 462 707-5 +36 Other options F = 0 0 0 489 532 516 525 6-100 F = F 2017 40 249 0.077 488 013 477 475-2 -1 F = F 2017 1.2 47 957 0.093 487 710 470 032-4 +18 F = F 2017 1.6 63 046 0.124 487 104 455 497-6 +55 F = F 2017 2.0 77 708 0.155 486 499 441 418-9 +91 F pa 55 555 0.11 487 407 462 707-5 +36 F lim 95 457 0.19 485 743 424 437-13 +134 SSB (2019) = B lim 455 403 1.60 459 043 103 000-78 +1018 SSB (2019) = B pa 360 990 1.04 469 570 181 000-61 +786 SSB (2019) = MSY B trigger 360 990 1.04 469 570 181 000-61 +786 Advice is for T. trachurus, while TAC is for all Trachurus species. Percentage of other Trachurus species in the horse mackerel catch varies by year (estimated to be < 10% in 2016). ICES considers that management of several species under a combined TAC prevents effective control of the singlespecies exploitation rates and could lead to overexploitation of any of the species.

Boarfish in Subareas 6-8 Advice for 2018 and 2019, Precautionary approach: Catch in each year 21 830 t * Stock status relative to potential reference points is unknown * Stock biomass at lower level since 2014 Category 3 stock: Exploratory assessment with biomass dynamics model: indicative of trends in stock biomass Catch(2016) = 19 315 t (~ 6.6% discarding, from demersal gears; all landings from pelagic fishery) o Assessment uses several survey indices: 6 from bottom trawl (each considered indicative of trends in its area) and 1 acoustic survey. o Overall biomass index influenced by acoustic survey. Acoustic survey was redesigned in 2017 to improve stock coverage. o Limited understanding of the stock dynamics

Boarfish in Subareas 6-8 Advice follows approach for Category 3 stocks Index A (2016, 2017) 0.61 Index B (2013, 2014, 2015) 0.99 Index ratio (A/B) 0.62 Uncertainty cap Applied 0.8 Advised catch for 2017 27 288 t Discard ratio (2016) 6.6% Precautionary buffer Not applied - Catch advice* 21 830 t Wanted catch corresponding to the catch advice** 20 380 t * (Recent advised catch) x cap ** (Catch advice) x (1 discard ratio) Precautionary buffer applied last year. Not reapplied this year.

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