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

Transcription

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

2 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

3 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

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

5 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

6 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

7 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

8 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%

9 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

10 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)

11 All advice available online at: Click on 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 contact (e.g. to enquire about workshops, registration to workshops...):

12 Widely distributed stocks

13 Blue whiting in Subareas 1-9, 12, 14 Advice for 2018, LTMS of EU, Faroes, Iceland and Norway: Catch 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%

14 Blue whiting in Subareas 1-9, 12, 14 Catch 2016: 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 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

15 Blue whiting in Subareas 1-9, 12, 14 Assumptions 2017: Catch = million t (based on declared quotas and expected uptake) SSB(2018)= 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 ) Other options MSY approach: F MSY F = F pa F lim SSB (2019) = B lim SSB (2019) = B pa SSB (2019) = MSY B trigger F = F SSB (2019) = SSB (2018) Catch (2019) = Catch (2018)

16 Norwegian spring-spawning herring (Subareas 1, 2, 5, & Divisions 4a, 14a) Advice for 2018, EU, Faroes, Iceland, Norway, Russia MP: Catch 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

17 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

18 Norwegian spring-spawning herring (Subareas 1, 2, 5, & Divisions 4a, 14a) Assumptions 2017: Catch = 805 kt (based on declared quotas) SSB(2018)= 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^ Other options MSY approach: F MSY SSB(2018)/MSY B trigger F MSY F = F pa SSB (2019) = B lim SSB (2019) = B pa = MSY B trigger ^^ F = F * 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

19 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

20 North Sea horse mackerel Advice for 2018 and 2019, Precautionary approach: Catch in each year 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 ~ 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

21 North Sea horse mackerel o Catch (2016) = t (10% discarded, non-directed fisheries) Advice follows approach for Category 3 stocks Index A (average of ) 692 indv/hour Index B (average of ) 254 indv/hour Ratio (A/B) 2.7 Uncertainty cap Applied 1.2 Precautionary buffer Applied 0.8 Advised catch for tonnes Catch advice for each of 2018 and 2019* tonnes Discard rate (average ) 13.35% Landings corresponding to the catch advice** 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 This exploitation pattern, catching mostly immature individuals, might hinder stock recovery.

22 Mackerel in Northeast Atlantic Advice for 2018, MSY approach: Catch 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

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

24 Mackerel in Northeast Atlantic Catch 2016: 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

25 Mackerel in Northeast Atlantic Assumptions 2017: Catch = 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 Other options F = F pa F lim SSB(2019) = B lim SSB(2019) = MSY B trigger = B pa F = F Catch(2018) = Catch(2017) - 20% Catch(2018) = Catch(2017) Catch(2018) = Catch(2017) + 20% F = F = F = F = F = F = F = F = F = F =

26 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

27 Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during , 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

28 Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during , 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

29 Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during , 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

30 Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during , 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

31 Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during , 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.

32 Norway, EU, Faroes request to evaluate LTMS for mackerel: Results Base-case: weights-at-age as during , 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.

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

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

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

36 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

37 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

38 Western horse mackerel Advice for 2018, MSY approach: Catch 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

39 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

40 Western horse mackerel Catch(2016) = t (~ 4% discarded) Assumptions 2017: Catch = (EU TAC) SSB(2018)= t < MSY B trigger ( 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 Other options F = F = F MSY = F pa F = F lim SSB (2019) = B lim SSB (2019) = MSY B trigger =B pa F = F * Catch(2018) relative to the ICES advised catch for 2017 ( t)

41 Southern horse mackerel Advice for 2018, MSY approach: Catch t. * F below F MSY and SSB above MSY B trigger over whole time series * Recruitment in above average Catch(2016) = 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

42 Southern horse mackerel

43 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 ( t) SSB (2019) spawning time % SSB change 2019 vs 2018 % Catch change* ICES advice basis MSY approach: F MSY Other options F = F = F F = F F = F F = F F pa F lim SSB (2019) = B lim SSB (2019) = B pa SSB (2019) = MSY B trigger 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.

44 Boarfish in Subareas 6-8 Advice for 2018 and 2019, Precautionary approach: Catch in each year 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) = 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

45 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 t Discard ratio (2016) 6.6% Precautionary buffer Not applied - Catch advice* t Wanted catch corresponding to the catch advice** 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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