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Blue whiting - Northeast Atlantic, 2008
Marine Resource  Fact Sheet
ICES Advice 2009
Blue whiting - Northeast Atlantic, 2008
Fact Sheet Citation  
Blue whiting combined stock (Subareas I-IX, XII and XIV)
Owned byInternational Council for the Exploration of the Sea (ICES) – More
Related observationsLocate in inventorydisplay tree map
 
Species:
FAO Names: en - Blue whiting(=Poutassou), fr - Merlan bleu, es - Bacaladilla, ar - غُبَر أزرق, zh - 小鳍鳕, ru - Путассу северная
Geographic extent of Blue whiting - Northeast Atlantic
Main Descriptors
Considered a single stock: Yes        Spatial Scale: Sub-Regional
Management unit: Yes
 
 
Habitat and Biology
Depth zone: Shelf (50 m - 200 m).   Vertical distribution: Demersal/Benthic.  

Geographical Distribution
Jurisdictional distribution: Straddling between High Seas and EEZ

Water Area Overview
Spatial Scale: Sub-Regional

Geo References
Resource Structure
Considered a single stock: Yes
Exploitation
 

Factors affecting the fisheries and the stock

Impact of the environment on the fish stock

Understanding of the environmental factors which influence blue whiting recruitment has improved, but is still too limited for providing recruitment forecasts. The position and strength of the North Atlantic subpolar gyre appears to influence the spawning success of blue whiting by constraining spawning along the European continental slope and south of Porcupine Bank (Hatun et al., 2009). The ICES Workshop on blue whiting recruitment (WKBLUR) will meet in late 2009 to examine whether blue whiting recruitment, can be predicted or described in a quantitative manner.

Growth rate and the weights-at-age in the catches and the stock have been declining since the early 1990s. This trend now seems to have ceased in the stock, but has continued in the catches. The reason for this difference is that an increasing proportion of the landings are now taken from the spawning area, where weights-at-age are lower. The cause for the overall decrease is unknown. Further analyses to examine the link between the environment and growth should be initiated.

Large changes in the abundance of blue whiting are likely to have a wide impact on the ecosystem. Blue whiting is an important prey to a large range of predators. Blue whiting preys upon larger crustaceans and small fish, including smaller blue whiting.
Assessment
 
Assessment Model
Methodology

Scientific basis

Data and methods

The assessment is based on catch-at-age data from commercial catches from 1981–2008 and three acoustic surveys (Norwegian spawning ground survey 1993–2003, international ecosystem survey in the Nordic Seas 2000–2009, and the international blue whiting spawning ground survey 2004–2009). The international blue whiting spawning ground survey is the only survey that covers almost the entire distributional area of the spawning stock. The same assessment model has been used during the last four years. However, in this year’s assessment, the results from the spawning ground survey were accorded greater statistical weight than in previous assessments because the survey time-series is now longer than when the survey was initially included in the stock assessment (2007). The actual weighting factors used this year were internally estimated within the modelling framework.

The model assessment setting were changed this year compared with last year resulting in higher weights being given to the estimates of the comprehensive international blue whiting spawning ground survey in the stock estimates. The actual weights used this year were internally estimated within the modelling framework. This was done because the time series is now longer than when the survey was initially included in the stock assessment (2007).

Uncertainties in assessment and forecast

The comprehensive international blue whiting spawning ground survey shows a large inter-annual variation in the age-structured indices. This information could be taken into account in the management plan by adopting constraints on TAC changes; i.e. limiting inter-annual variability in TAC. At present, this has not been agreed (see Article 7).

Limited information was available on discarding and discards are not included in the assessment. However, discarding is considered to be minor.

Indications of low recruitment of year classes 2005–2008 are consistent in both the survey and catch data.

The catch in the intermediate year (2009) was assumed to be the agreed TAC and additional allocation to Russia.

Comparison with previous assessment and advice

The updated assessment has a lower fishing mortality in 2007 and a higher SSB in 2008 than estimated in last year’s assessment. The estimated SSB for 2008 has been revised upwards by 40% and the estimated fishing mortality in 2007 has been revised downwards by 13%. Around 40% of the change in SSB is due to the greater reliance this year on spawning ground survey results (relaxation of the constraint on survey CV), and the remainder due to the addition of recent data.

Last year the advice was based on precautionary limits. This year the advice is based on the agreed management plan.
Overall Assessment Results


Figure 9.4.4.1. Blue whiting in Subareas I–IX, XII, and XIV (Combined stock). Summary of stock assessment: landings, fishing mortality, recruitment, and SSB.


Figure 9.4.4.2. Blue whiting in Subareas I–IX, XII, and XIV (Combined stock). Stock–recruit relationship and precautionary approach plot.


Figure 9.4.4.3. Blue whiting in Subareas I–IX, XII, and XIV (Combined stock). Comparison of current assessment with previous assessments.


Table 9.4.4.2. Blue whiting in Subareas I–IX, XII, and XIV (Combined stock). Landings (tonnes) by country for the period 1988–2008, as estimated by the Working Group.

Table 9.4.4.3.
Table 9.4.4.4. Blue whiting in Subareas I–IX, XII, and XIV (Combined stock). Landings (tonnes) by main areas.
Area Norwegian Sea fishery (SAs 1+2; Divs. Va, XIVa-b) Fishery in the spawning area (SA XII; Divs. Vb, VIa-b, VIIa-c) Directed- and mixed fisheries in the North Sea (SA IV; Div. IIIa) Total northern areas Total southern areas (SAs VIII+IX; Divs. VIId-k) Grand total
1988 55 829 426 037 45 143 527 009 30 838 557 847
1989 42 615 475 179 75 958 593 752 33 695 627 447
1990 2 106 463 495 63 192 528 793 32 817 561 610
1991 78 703 218 946 39 872 337 521 32 003 369 524
1992 62 312 318 081 65 974 446 367 28 722 475 089
1993 43 240 347 101 58 082 448 423 32 256 480 679
1994 22 674 378 704 28 563 429 941 29 473 459 414
1995 23 733 423 504 104 004 551 241 27 664 578 905
1996 23 447 478 077 119 359 620 883 25 099 645 982
1997 62 570 514 654 65 091 642 315 30 122 672 437
1998 177 494 827 194 94 881 1099 569 29 400 1128 969
1999 179 639 943 578 106 609 1229 826 26 402 1256 228
2000 284 666 989 131 114 477 1388 274 24 654 1412 928
2001 591 583 1045 100 118 523 1755 206 24 964 1780 170
2002 541 467 846 602 145 652 1533 721 23 071 1556 792
2003 931 508 1211 621 158 180 2301 309 20 097 2321 406
2004 921 349 1232 534 138 593 2292 476 85 093 2377 569
2005 405 577 1465 735 128 033 1999 345 27 608 2026 953
2006 404 362 1428 208 105 239 1937 809 28 331 1966 140
2007 172 709 1360 882 61 105 1594 695 17 634 1612 330
2008 68 009 1111 292 36 090 1215 704 30 761 1246 465


Table 9.4.4.5. Blue whiting in Subareas I–IX, XII, and XIV (Combined stock). Summary of stock assessment.
Year Recruitment SSB Landings Mean F
  Age 1     Ages 3-7
  thousands tonnes tonnes  
1981 3284498 2940822 922980 0.278
1982 4088118 2420040 550643 0.224
1983 14672348 1973555 553344 0.262
1984 18224469 1716655 615569 0.341
1985 10523138 1985473 678214 0.381
1986 8551933 2296947 847145 0.504
1987 8994301 1989511 654718 0.389
1988 6692565 1789894 552264 0.379
1989 9362232 1714449 630316 0.497
1990 24610077 1544634 558128 0.483
1991 8667227 1980116 364008 0.232
1992 5722465 2646105 474592 0.208
1993 5369215 2569728 475198 0.213
1994 5804864 2492748 457696 0.188
1995 8308089 2315299 505176 0.247
1996 23772577 2163908 621104 0.332
1997 46286345 2250223 639681 0.330
1998 28885207 3240493 1131950 0.457
1999 24350488 3939065 1261030 0.415
2000 40416845 4260778 1412450 0.530
2001 62386545 4729365 1771810 0.471
2002 56651469 5868596 1556950 0.432
2003 55104356 7352308 2365320 0.473
2004 49375747 7445350 2400790 0.539
2005 27925442 7049337 2018340 0.429
2006 8127171 7129418 1956240 0.331
2007 4862194 5995302 1612270 0.323
2008 6617187* 4748673 1251851 0.288
2009   3588248    
Average 19988280 3521967 1029992 0.363
* Replaced by 3869000 in forecast.

Reference Point
 


  Type Value Technical basis
Precautionary approach Blim 1.5 million t Bloss
  Bpa 2.25 million t Blim exp(1.645*), with = 0.25.
  Flim 0.51 Floss
  Fpa 0.32 Fmed (1998).
Targets

Fy

By

0.18

> 2.25 million t

= F0.1 and target F in the agreed management plan

= trigger SSB for F <0.18

(unchanged since 1998, targets added in 2008 on the basis of the agreed management plan; Btrigger updated in 2009).



ICES evaluated the biomass limit reference point in 2007. The original reference point was set in 1998, before the period of high productivity became apparent. ICES examined the consequences of these new observations on the reference points and concluded that the reference points did not depend on the productivity regime and should remain unchanged.


Yield and spawning biomass per Recruit F-reference points (2008).
  Fish Mort Yield/R SSB/R
  Ages 3–7    
Average last 3 years 0.41 0.05 0.16
F0.1 0.18 0.04 0.26
Fmed 0.34 0.05 0.18



Fmax is not well-defined.

Candidates for reference points which are consistent with high long-term yields and a low risk of depleting the productive potential of the stock are in the range of F0.1.
Projection


Outlook for 2010. Basis: Catch(2009) = 606 (Coastal States TAC + NEAFC allocation) ; Catch constraint, F2009 = 0.17; SSB(2009) = 3586; SSB(2010) = 3041; R(2010,2011) = GM(1981–1996) = 8.83 billion at age 1.
Rationale

Catch

(2010)

Basis

F

(2010)

SSB

(2011)

%SSB change1 % TAC change2
Zero catch 0 F=0 0 3168 +4% -100
Status quo 816 Fsq= F2008 0.29 2353 -23% +35%
Management Plan 540 Target F (F=0.18) 0.18 2627 -14% -11%
High long-term yield 540 F0.1 0.18 2627 -14% -11%
Precautionary limits 94 F2008 * 0.1 0.03 3074 +1% -84%
  229 F2008 * 0.25 0.07 2938 -3% -62%
  441 F2008 * 0.50 0.14 2726 -10% -27%
  636 F2008 * 0.75 0.22 2532 -17% +5%
  891 Fpa = F2008*1.14 0.32 2279 -25% +47%
  921 Maintain SSB>Bpa 0.33 2249 -26% +52%

Weights in thousand tonnes.

1 SSB 2011 relative to SSB 2010.

2 TAC 2010 relative to TAC 2009.

Scenarios in italics are not considered consistent with the precautionary approach.



Scientific Advice

Single-stock exploitation boundaries

ICES advises on the basis of the agreed management plan that catches in 2010 should be 540 000 t.

Exploitation boundaries in relation to existing management plans

Following the agreed management plan implies landings of 540000 tonnes in 2010 which is expected to lead to a decline in the SSB of 14% by 2011.

Exploitation boundaries in relation to high long-term yield, low risk of depletion of production potential and considering ecosystem effects

F0.1 corresponds to the target fishing mortality in the management plan.

Exploitation boundaries in relation to precautionary limits

The agreed management plan is consistent with the precautionary approach.


Table 9.4.4.1. Blue whiting in Subareas I–IX, XII, and XIV (Combined stock). Single-stock exploitation boundaries (advice), management, and catch.
Year

ICES

Advice

Predicted catch corresp.

to advice

Agreed

TAC

ICES catch
1987 TAC for northern areas; no advice for southern areas 950 - 665
1988 TAC for northern areas; no advice for southern areas 832 - 558
1989 TAC for northern areas; no advice for southern areas 630 - 627
1990 TAC for northern areas; no advice for southern areas 600 - 562
1991 TAC for northern areas; no advice for southern areas 670 - 370
1992 No advice - - 475
1993 Catch at status quo F (northern areas); no assessment for southern areas 490 - 481
1994 Precautionary TAC (northern areas); no assessment for southern areas 485 6501 459
1995 Precautionary TAC for combined stock 518 6501 579
1996 Precautionary TAC for combined stock 500 6501 646
1997 Precautionary TAC for combined stock 540   672
1998 Precautionary TAC for combined stock 650   1125
1999 Catches above 650 000 t may not be sustainable in the long run 650   1256
2000 F should not exceed the proposed Fpa 800   1412
2001 F should not exceed the proposed Fpa 628   1780
2002 Rebuilding plan 0   1556
2003 F should be less than the proposed Fpa 600   2321
2004 Achieve 50% probability that F will be less than Fpa 925   2378
2005 Achieve 50% probability that F will be less than Fpa 1075   2027
2006 F old management plan 1500 21002 1966
2007 F should be less than the proposed Fpa 980 18473 1612
2008 F should be less than Fpa 835 12504 1246
2009 Maintain stock above Bpa 384 6065  

2010

Follow the agreed management plan 540    

Weights in ‘000 t.

1NEAFC proposal for NEAFC regions 1 and 2.

2 Agreed TAC from four Coastal States of 2 million tonnes, and an additional allocation to Russia in the international zone of 100 000 t.

3Agreed TAC from four Coastal States of 1.7 million tonnes, and an additional allocation to Russia and Greenland of 147 000 t.

4Agreed TAC from four Coastal States of 1.1 million tonnes, and an additional allocation to Russia and Greenland.

5Agreed TAC from four Coastal States of 0.59 million tonnes, and an additional allocation to Russia (0.016 million tonnes).



Management
Management unit: Yes

Management Objectives

The management plan was agreed by Norway, EU, The Faroe Islands and Iceland, and NEAFC in November 2008.

  1. The Parties agree to implement a long term management plan for the fisheries on the Blue Whiting stock, which is consistent with the precautionary approach, aiming at ensuring harvest within safe biological limits and designed to provide for fisheries consistent with maximum sustainable yield, in accordance with advice from ICES.
  2. For the purpose of this long term management plan, in the following text, “TAC” means the sum of the coastal State TAC and the NEAFC allowable catches.
  3. As a priority, the long term plan shall ensure with high probability that the size of the stock is maintained above 1.5 million tonnes (Blim).
  4. The Parties shall aim to exploit the stock with a fishing mortality of 0.18 on relevant age groups as defined by ICES.
  5. While fishing mortality exceeds that specified in paragraph 4 and 6, the Parties agree to establish the TAC consistent with reductions in fishing mortality of 35% each year until the fishing mortality established in paragraph 4 and 6 has been reached. This paragraph shall apply only during 2009 and 2010.


For the purposes of this calculation, the fishing percentage mortality reduction should be calculated with respect to the year before the year in which the TAC is to be established. For this year, it shall be assumed that the relevant TAC constrains catches.

  1. When the fishing mortality in paragraph 4 has been reached, the Parties agree to establish the TAC in each year in accordance with the following rules:


  • In the case that the spawning biomass is forecast to reach or exceed 2.25 million tonnes (SSB trigger level) on 1 January of the year for which the TAC is to be set, the TAC shall be fixed at the level consistent with the specified fishing mortality.
  • In the case that the spawning biomass is forecast to be less than 2.25 million tonnes on 1 January of the year for which the TAC is to be set (B), the TAC shall be fixed that is consistent with a fishing mortality given by:


F = 0.05 + [(B – 1.5)(0.18 – 0.05) / (2.25 – 1.5)]

  • In the case that spawning biomass is forecast to be less than 1.5 million tonnes on 1 January of the year for which the TAC is to be set, the TAC will be fixed that is consistent with a fishing mortality given by F = 0.05.


  1. When the fishing mortality rate on the stock is consistent with that established in paragraph 4 and the spawning stock size on 1 January of the year for which the TAC is to be set is forecast to exceed 2.25 million tonnes, the Parties agree to discuss the appropriateness of adopting constraints on TAC changes within the plan.
  2. The Parties, on the basis of ICES advice, shall review this long term management plan at intervals not exceeding five years and when the condition specified in paragraph 4 is reached


ICES has evaluated the agreed management plan and concluded that the agreement is consistent with the precautionary approach (the risk of falling below Blim in the long term 10–20 years is less than 5%).
Management Advice

Management considerations

The upward revision of SSB from the assessment this year (Figure 9.4.4.3) indicates that the absolute estimate of SSB is uncertain. However, all model results showed a steep decline in SSB, such that SSB in the start of 2009 is only half of what it was in the period 2003–2006. All available information shows that the recruitment (age 1 fish) has been at a low level since 2006. The advice is based on the management plan, which gives a TAC of 540000 t in 2010, based on a fishing mortality of 0.18. Even such a low fishing mortality will lead to a decrease in SSB by 14% in one year, and the decline is expected to continue if recruitment remains at the recent low level.

Recent work on stock identification of blue whiting based on genetics and growth rates suggests that there is likely to be more than a single stock in the Northeast Atlantic. While more work is required to confirm the stock composition, blue whiting populations in areas VIIk and VIIj and further south likely form a separate unit from all other Northeast populations.

Any agreed TAC should cover all areas where blue whiting is fished. It is noted that there currently exists large catches of blue whiting in international waters.

Management plan evaluations

In July 2008 a draft management plan was proposed by the Coastal States (Norway, Faroe Islands, Iceland, and EU). ICES has evaluated the draft management plan and considers it precautionary providing “that to be consistent with the precautionary approach it is necessary to reduce F according to the HCR in one year. In addition, ICES notes that a trigger biomass of at least 2.5 million tonnes is expected to have a less than 10% probability of driving the stock below Blim. Therefore, a trigger biomass of at least 2.5 million tonnes could be used as an appropriate trigger biomass for the proposed management plan“ (ICES, 2008).

A management plan was subsequently agreed in November 2008 which stipulated a maximum reduction of 35% in fishing mortality in the first two years (2009 and 2010) of the plan and a trigger biomass set at 2.25 million tonnes. In evaluating the draft management plan, ICES has also evaluated the harvest control rule contained in the agreed management plan and concluded that the agreement is consistent with the precautionary approach in the long-term (the risk of falling below Blim in the long term 10–20 years is less than 5%).

In the advice provided by ICES in 2008, both the trigger biomass and the percentage reduction to target fishing mortality were based on a short-term outlook (less than 7 years). Given the status of the stock, the percentage reduction in fishing mortality is not an issue in 2010. In the long term, the harvest control rule was found to be precautionary for the range of the trigger biomass explored: 2250 to 2750 thousand tonnes (ICES, 2008).
Biological State and Trend
Exploitation rate: Harvested sustainably
Abundance level: Full reproductive capacity


Spawning biomass in relation to precautionary limits Fishing mortality in relation to precautionary limits Fishing mortality in relation to high long term yield Fishing mortality in relation to agreed target Comment
Full reproductive capacity Harvested Sustainably

Overfished

Above target  



Based on the most recent estimates of SSB (in 2009) and, fishing mortality (in 2008), ICES classifies the stock as having full reproductive capacity and being harvested sustainably (F=0.29). Year classes 2005-2008 are among the lowest observed. Due to recent low recruitment, SSB has declined from its historical peak in 2003-2004 of more than 7 million tonnes to 3.6 million tonnes at the beginning of 2009, and the decline is expected to continue in the short-term.
Source of information
 
ICES. 2009. Report of the ICES Advisory Committee, 2009. ICES Advice, 2009.
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