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ICES WGMHSA Report 2006

ICES Advisory Committee on Fishery Management ICES CM 2006/ACFM:36

Report of the Working Group on the Assessment of Mackerel, Horse Mackerel, Sardine and Anchovy (WGMHSA)

5 - 14 September 2006

Galway, Ireland

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International Council for the Exploration of the Sea Conseil International pour l’Exploration de la Mer

H.C. Andersens Boulevard 44-46 DK-1553 Copenhagen V Denmark

Telephone (+45) 33 38 67 00 Telefax (+45) 33 93 42 15 www.ices.dk

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Recommended format for purposes of citation:

ICES. 2006. Report of the Working Group on the Assessment of Mackeral, Horse Mackerel, Sardine and Anchovy (WGMHSA), 5 - 14 September 2006, Galway, Ireland. ICES CM 2006\ACFM:36. 601 pp.

For permission to reproduce material from this publication, please apply to the General Secretary.

The document is a report of an Expert Group under the auspices of the International Council for the Exploration of the Sea and does not necessarily represent the views of the Council.

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ICES WGMHSA Report 2006 i

0 Executive Summary

The Working Group on the Assessment of Mackerel, Horse Mackerel, Sardine and Anchovy (WGMHSA) met in Galway from 4-15 September, to assess and provide catch options for these four widely distributed pelagic species in the Northeast Atlantic Ocean. The WG reports on the status of 7 stocks (see Fig. 0.1 for stock definitions), and in case of Sardine also on the status of the species distributed outside current stock definition. This year a benchmark analytical assessment is available for Sardine and update analytical assessments are available for Northeast-Atlantic Mackerel and Anchovy in Biscay. Due to its depleted state Anchovy in Biscay is now on the observation list. Exploratory analysis continued on western and southern Horse mackerel stocks and Gulf of Cadiz anchovy. All these assessments are still in a developmental stage, whilst no assessment was possible for North Sea horse mackerel due to lack of coherent data.

Northeast-Atlantic (NEA) Mackerel. This species is distributed in the whole ICES area and currently supports one of the most valuable European fisheries (with around 500 kt annual landings). Mackerel is fished by a variety of fleets (ranging from open boats using hand lines on the Iberian coasts to large freezer trawlers and Refrigerated Sea Water (RSW) vessels in the Northern Area. The stock is historically divided into three components, with the North Sea component considered to be over fished since the late 1970s, and the Western component contributing the vast majority of biomass and catch to the stock. The quality of sampling data remains good. The NEA mackerel assessment was treated as an update, with new inputs to the assessment coming only from fishery dependent data. However there has been some progress made on the putative effect of different misreporting levels on the assessment, and its interpretation for advice. There are a number of issues outlined which will need to be addressed in the Benchmark in 2007, and the WG has made a number of recommendations for intercessional work. The WG concludes that the accuracy of landings and estimates of total discards are still inadequate.

Horse Mackerel. For North Sea horse mackerel effort was applied this year finalise whether there were any coherence in the available data. The data exploration again showed inconsistent signals in the catch at age data and a survey index, which may be missing an important component of the stock due to seasonal migration. The WG concluded that more intensive age sampling and a directed survey will need to be available before an analytical assessment can be attempted for this stock. The exploratory analysis for western horse mackerel was refined to incorporate information on age structure into the egg abundance index. This allows in an indirect way the assessment to be scaled. The assessment indicates that the current level of biomass is at or above that in 1982. However large uncertainty surrounds the estimates of stock parameters. The analyses confirms strong recruitment of the 2001 year class however this is not estimated to be the same order of magnitude as the 1982 year class. An exploratory analyses was conducted for southern horsemackerel. The 2 surveys were surveys combined a clear cohort signal was evident. However the previously adopted AMCI approach required strong conditioning and gave unrealistic results, so the data were explored in an XSA model. A declining trend in SSB is still apparent.

Sardine The results of the SARDYN project were presented and were not conclusive with respect to the most suitable assessment model and the level of migration between areas. Both single area and multi area assessments were considered. The multi area assessments required either strong conditioning or assumptions on fixed migration rates from expert judgement.

However in a bayesian framework, useful indications on the probability of emigration from the Biscay shelf to the Cantabrian Sea could be made. The single area AMCI model was explored in detail and some changes in conditioning were made. The most significant of these was the merging of the 2 Spring surveys and the treatment of the DEPM as relative. Although

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2 ICES WGMHSA Report 2006

much progress has been made with these issues, there remain some outstanding issues with the final assessment, which will require further exploration.

Anchovy is a short-lived species, showing large fluctuations in biomass. This is driven by recruitment which in turn might be driven by a combination of environmental factors. In Bay of Biscay Anchovy catches consist mainly of 1- and 2-yr old fish. In 2005 there was a failure of the commercial fishery for the Biscay stock, and this prompted much intercessional work since May 2005. Exploration of both the old ICA assessment and new Bayesian biomass based model (BBM) are provided. This included the sensitivity of the Bayesian production model to informative priors, and the effect and consequences of treating both surveys as relative measures of stock abundance. The prognosis for Bay of Biscay Anchovy is that the stock is still in a depleted state, although recruitment in 2006 shows improvement. The assessment of Anchovy in Cadiz is developed further this year with a standardisation of the CPUE index. However this exploratory assessment is sensitive to new information in 2006.

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Figure 0.1: Distribution of the four species assessed by the ICES Mackerel, Horse Mackerel, Sardine and Anchovy WG: Stock and component definitions as used by the 2004 WG. Map source: GEBCO, polar projection, 200 m depth contour drawn. a: Northeast Atlantic Mackerel (with North Sea, Western and Southern component), b: Horse Mackerel: North Sea, Western and

“Southern“ stock, c: Sardine, d: Anchovy: Stock in area VIII and stock in IXa.

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1 Introduction

1.1 Terms of Reference

The Working Group on the Assessment of Mackerel, Horse Mackerel, Sardine, and Anchovy [WGMHSA] met in Galway, Ireland from 5–14 September 2006 to address the following terms of reference, as decided by the 93^rd Statutory Meeting:

a ) assess the status of and provide management options for 2007 for the stocks of mackerel, sardine stock in Divisions VIIIc and IXa, western horse mackerel, southern horse mackerel, anchovy in Subarea VIII and anchovy in Division IXa;

b ) carry out in-depth exploratory assessments for Sardine and anchovy in Subarea VIII;

c ) for the stocks mentioned in a) perform the tasks described in C.Res. 2ACFM01.

In resolution 2ACFM01 the following general terms of reference are relevant to this working group

1) based on input from e.g. WGRED and for the North Sea NORSEPP, consider existing knowledge on important environmental drivers for stock productivity and management and if such drivers are considered important for management advice incorporate such knowledge into assessment and prediction, and important impacts of fisheries on the ecosystem;

2) Evaluate existing management plans to the extent that they have not yet been evaluated.

Develop options for management strategies including target reference points if management has not already agreed strategies or target reference points (or HCRs) and where it is considered relevant review limit reference points (and come forward with new ones where none exist) – following the guidelines from SGMAS (2005, 2006), AGLTA (2005) and AMAWGC (2004, 2005, and 2006); If mixed fisheries are considered important consider the consistence of options for target reference points and management strategies. If the WG is not in a position to perform this evaluation then identify the problems involved and suggest and initiate a process to perform the management evaluation;

3) where mixed catches are an important feature of the fisheries assess the influence of individual fleet activities on the stocks and the technical interactions;

4) update the description of fisheries exploiting the stocks, including major regulatory changes and their potential effects. Comment on the outcome of existing management measures including technical measures, TACs, effort control and management plans. The description of the fisheries should include an enumeration of the number, capacity and effort of vessels prosecuting the fishery by country;

5) where misreporting is considered significant provide qualitative and where possible quantitative information, for example from inspection schemes, on its distribution on fisheries and the methods used to obtain the information; document the nature of the information and its influence on the assessment and predictions;

6) provide for each stock information on discards (its distribution in time and space) and the method used to obtain it. Describe how it has been considered in the assessment;

7) report as prescribed by the Secretariat on a national basis an overview of the sampling of the basic assessment data for the stocks considered;

8) provide specific information on possible deficiencies in the 2006 assessments including, at least, any major inadequacies in the data on landings, effort or discards; any major inadequacies in research vessel surveys data, and any major difficulties in model formulation; including inadequacies in available software. The consequences of these deficiencies for both the assessment of the status of the stocks and the projection should be clarified.

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Term of reference a is addressed under the respective stocks. The WG clarified with ACFM chair that there must have been an error in ToR b as a benchmark assessment had been attempted on Bay of Biscay Anchovy in 2006. Due to the current depleted state of the stock the WG treated Bay of Biscay anchovy as a stock on the Observation list, and in addition to ToR a, a special request was responded to, This is dealt with in section 1.x

The structure of Sections 7 and 8 address term of reference b, with special consideration given to the results of the “Sardyn” project. Using new information from “Sardyn”, data and model exploration focused on the spatial dynamics of the assessed component of the Sardine population in VIIIc and IXa.

The NEA mackerel assessment was treated as an update, with new inputs to the assessment coming only from fishery dependent data. The western horse mackerel assessment model has been refined in an attempt to address the scaling issues, and some HCR scenarios are presented, however the production of quantitative short term advice still remains problematic.

A quantitative assessment for North sea horse mackerel is still not possible due to the lack of coherent catch at age data and a suitable index. An update assessment was performed for Southern Horsemackerel where the surveys were merged. Anchovy in Cadiz was also treated as an update assessment.

Where relevant terms of reference 1-6 are addressed under the respective stocks. An overview of the input data and their shortcomings (addressing terms of reference 7-8) is given in Section 1.3, and an overview of the assessment methods in Section 1.4.

The present report is structured as last year. Specific attention has again been given to the explicit treatment of uncertainties in either the input data or the assessment assumptions.

1.2 Participants

Esther Abad Spain

Pablo Abaunza Spain

Sergei Belikov Russia

Miguel Bernal Spain

Lisa Borges The Netherlands

Andy Campbell (part time) Ireland

Mariella Canales Chile

Bruno Caneco (part time) Portugal Carryn Cunningham (part time) South Africa Mark Dickey-Collas The Netherlands Leonie Dransfeld Ireland

Erwan Duhamel France

Afra Egan Ireland

Emma Hatfield UK (Scotland)

Leire Ibaibarriaga Spain

Svein A. Iversen Norway

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Jan Arge Jacobsen (part time) Faroe Islands Ciarán Kelly (Chair) Ireland

Jacques Massé France

Alberto Murta Portugal

Fernando Ramos Spain

Beatriz Roel UK (England and Wales)

Begoña Santos Spain

Evgeny Shamray Russia

John Simmonds UK (Scotland)

Alexandra Silva Portugal

Dankert Skagen Norway

Per Sparre Denmark

Andres Uriarte Spain

Dimitri Vasilyev Russia

1.3 Quality and Adequacy of Fishery and Sampling data.

1.3.1 Sampling data from commercial fishery

The Working Group again carried out a brief review of the sampling data and the level of sampling on the commercial fisheries. Sampling coverage in 2005 increased for mackerel to 83% but the intensity of sampling with numbers measured and aged has decreased since last year. The proportion of the sampled horse mackerel catch has again increased after the low sampling intensity in 1999 and a decrease in 2004. In 2005 the sampling level was 78% and this is still considered inadequate for some Divisions and periods (especially in the juvenile areas). Sardines continue to be well sampled with samples now provided by Portugal, Spain and France. However, to facilitate age-structured assessment, samples should be obtained from all countries with catches of sardines, which includes Ireland, the Netherlands and the UK. The EU data collection regulation does not require sampling of sardines north of VIIIc.

Anchovy sampling continues at a high level. A short summary of the data, similar to that presented in recent Working Groups is shown in the relevant stock sections. Sampling programmes by EU countries have been partially funded under the EU sampling directive and this has contributed to the improvement in sampling levels. Under this data collection regulation fish in EU countries are supposed to be sampled in the country into which they are landed.

The sampling programmes on the various species are summarised as follows:

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Mackerel

YEAR TOTAL CATCH T (WGCATCH)

%CATCH COVERED BY SAMPLING PROGRAMME*

NO. SAMPLES

NO. MEASURED

NO. AGED

1992 760,000 85 920 77,000 11,800 1993 825,000 83 890 80,411 12,922 1994 822,000 80 807 72,541 13,360 1995 755,000 85 1,008 102,383 14,481 1996 563,600 79 1,492 171,830 14,130 1997 569,600 83 1,067 138,845 16,355 1998 666,700 80 1,252 130,011 19,371 1999 608,928 86 1,109 116,978 17,432 2000 667,158 76 1,182 122,769 15,923 2001 677,708 83 1,419 142,517 19,824 2002 717,882 87 1,450 184,101 26,146 2003 617,330 80 1,212 148,501 19,779 2004 611,461 79 1,380 177,812 24,173 2005 543,486 83 1,229 164,593 20,217

* Percentage related to Working Group catch

In 2005, 83% of the total catch was covered by the sampling programmes. This constitutes a small increase to last year’s coverage, however sampling intensity has decreased with lower numbers of samples and numbers of fish aged and measured than in 2004. Denmark, Spain, Portugal and Russia carried out intensive programmes and covered 100% of their catches.

Ireland, Norway and Scotland also sampled their entire catch thoroughly with over 90% of their catches covered, however, the Netherlands only sampled 58% of their catch. England &

Wales continued to sample only a small fraction of their catches, while France, the Faroe Islands, Northern Ireland, Belgium, Iceland and Sweden did not sample any catches. This is despite there being significant catches taken by the first three of those countries.

The sampling summary of the mackerel catching countries is shown in the following table.

COUNTRY OFFICIAL CATCH

% OF CATCH SAMPLED* NO. SAMPLES NO.MEASURED NO.AGED

Belgium 1 0 0 0 0

Denmark 23,212 100 21 1,788 1,788 UK (England &

Wales) 14,677 4.3 60 8,069 1,797 Faroe Islands 9,769 0 0 0 0

France 16,338 0 0 0 0 Germany 19,040 65 28 10,366 1012 Ireland 45,687 95 35 5,114 2,303

Iceland 363 0 0 0 0

Norway 119,678 99 240 49,753 1,459 Portugal 1,509 100 261 24,441 1,368

Poland 570 0 0 0 0

Russia 40,495 100 62 19,330 1904 UK (Scotland) 129,990 91 116 16,237 3,487

Spain* 52,753 100 360 26,076 3,949 Sweden 3,204 0 0 0 0 The Netherlands 25,1262 58 46 3,419 1,150

UK (Northern

Ireland) 8,038 0 0 0 0

Total 510,445 83 1,229 164,593 20,217

* Percentage based on Working Group catch ** Values related to official catches

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The following text table shows sampling levels of mackerel by relating numbers measured and numbers aged to the size of the catch in each ICES division. Insufficient sampling was carried out in divisions IIIa, IVb-c, VIIc,d and VIIIa,d amounting to a total catch of 27,000t.

Divisions IIIb and VIIa,g,k were also not sampled, however these areas represent only minor catches of 210 t.

AREA OFFICIAL CATCH WG

CATCH NO SAMPLES NO AGED NO MEASURED

NO AGED/ 1000 TONNES**

NO MEASURED/ 1000 TONNES**

IIa 54,025 54,025 72 1,838 20,033 34 371 IIIa 1,026 1,026 0 0 0 0 0

IIIb 1 1 0 0 0 0 0

IVa 202,662 250,396 307 4,884 61,548 24 304

IVb 314 252 0 0 0 0 0

IVc 783 547 1 25 64 32 82 Vb 2,496 104 4 216 658 87 264 VIa 117,416 91,361 93 3,203 14,227 27 121

VIIa 174 174 0 0 0 0 0

VIIb 24,470 26,246 27 1,629 3,784 67 155 VIIc 1,489 2,259 0 0 0 0 0 VIId 5,787 6,470 12 300 985 52 170 VIIe 727 908 35 399 5,489 549 7,551 VIIf 366 366 25 1,398 2,580 3,817 7,044

VIIg 32 32 0 0 0 0 0

VIIh 823 2,033 1 25 43 30 52 VIIj 29,097 35,637 22 725 3,998 25 137

VIIk 0 2 0 0 0 0 0

VIIIa 10,442 13,028 8 200 502 19 48 VIIIb 2,923 7,716 53 661 3,186 226 1,090 VIIIc east 151 38,377 166 2,043 13,145 53 343 VIIIc west 0 4,625 83 666 5,899 144 1,275 VIIId 989 1,284 0 0 0 0 0 IXa central-north 1,509 1,509 261 1,368 24,441 907 16,201 IXa north 0 5,107 59 637 4,011 125 785

0 0 0 0 0

Total 457,704 543,486 1,229 20,217 164,593 44 360

** Values related to official catches

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Horse Mackerel

The following table shows a summary of the overall sampling intensity on horse mackerel catches in recent years:

Year Total catch t (WG Catch)

% Catch covered by sampling programme *

Samples Measured Aged 1992 436,500 45 1,803 158,447 5,797 1993 504,190 75 1,178 158,954 7,476 1994 447,153 61 1,453 134,269 6,571 1995 580,000 48 2,041 177,803 5,885 1996 460,200 63 2,498 208,416 4,719 1997 518,900 75 2,572 247,207 6,391 1998 399,700 62 2,539 245,220 6,416 1999 363,033 51 2,158 208,387 7,954 2000 272,496 56 1,610 186,825 5,874 2001 283,331 64 1,502 204,400 8,117 2002 241,336 72 1,768 235,697 8,561 2003 241,830 79 1,568 200,563 12,377 2004 216,361 68 1,672 213,066 16,218 2005 234,876 78 2,315 241,629 15,866

∗ WG catches

The decrease in overall sampling levels on horse mackerel seen in 2004 was reversed in 2005.

The large numbers of samples and measured fish are due mainly to intensive length measurement programs in the southern areas. In 2005, 72 % of the horse mackerel measured were from Division IXa.

Countries that carried out comprehensive sampling programmes (>90%) in 2005 were Norway, Spain, Ireland, and the Netherlands. In 2005, France and UK (England & Wales) took considerable catches but no samples were available. Some of these catches may be landed outside these countries. The lack of sampling data for relatively large portions of the horse mackerel catch continues to have a serious effect on the accuracy and reliability of the assessment and the Working Group remain concerned about the low number of fish that are aged.

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The following table shows the most important horse mackerel catching countries and the summarised details of their sampling programme in 2005:

Country Official catch t

Samples Measured Aged

Belgium 6 0 0 0 0

Denmark 14,197 85 10 845 394 UK (England &

W l ) 7,419 0 0 0 0

Faroe Islands 3,695 0 0 0 0

France 15,926 0 0 0 0

Germany 18,982 65 47 18,758 1,496 Ireland 35,361 92 36 5,881 2,135 UK (Northern Ireland) 426 0 0 0 0 Norway 25,113 99 11 1,492 288 Portugal 13,307 76 1,569 159,387 2,153

UK (Scotland) 142 0 0 0 0

Spain* 26,440 98 566 43,408 3,119

Sweden 239 0 0 0 0

The Netherlands 69,024 92 82 12,329 1,975 Total* 234,876 78 2,321 242,100 11,560

∗ WG catches

The following tables have information broken down by horse mackerel stock.

The horse mackerel sampling intensity for the Western stock (N.B. this now includes VIIIc – see section 3) was as follows:

% Catch covered by sampling programme

*

Belgium <1 0 0 0 0

Wales) 3,560 0 0 0 0

Faroe Islands 3,695 0 0 0 0 France 10,690 0 0 0 0

Germany 16,734 70 35 13,481 995 Ireland 35,361 92 36 5,881 2,135 UK (Northern

Ireland) 426 0 0 0 0

Norway 25,113 98 11 1,492 288 UK (Scotland) 142 0 0 0 0

Spain* 16,636 100 387 28,593 2,552

Sweden 148 0 0 0 0

The Netherlands 43,445 92 54 8,437 1,275

Total* 181,994 82 530 58,532 7,442

∗ WG catches

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The horse mackerel sampling intensity for the North Sea stock (IVb,c, VIId and the eastern part of IIIa) was as follows:

Belgium 6 0 0 0 0

Wales) 3,859 0 0 0 0

France 5,236 0 0 0 0

Germany 2,248 37 12 5,277 501

Sweden 91 0 0 0 0

The Netherlands 25,579 91 28 3,892 700

Total* 29,771 48 43 9,366 1,398 ∗ WG catches

The horse mackerel sample intensity for the North Sea stock was again low and only a small improvement from 2004 (38%). There were no samples from any quarters in Division IIIa, and only during the first quarter in Division IVc.

The sampling intensity for the Southern stock (N.B. this no longer includes VIIIc) was as follows:

Samples Measured Aged Portugal 13,307 76 1,569 159,387 2,153 Spain* 9,804 98 179 14,815 567 Total* 23,111 84 1,748 174,202 2,720

∗ WG catches

The horse mackerel sampling intensity for the Southern stock was lower than in 2004 (when it was 99% coverage).

A significant proportion of the unsampled horse mackerel catches are taken by foreign flagged freezer trawlers landing into the Netherlands. The Working Group strongly recommends that the Netherlands samples these landings.

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The sampling intensity of horse mackerel for the different Divisions was as follows

Division WG Catch Sampled Catch

% Catch covered by sampling

programmeNô samples Nô measured Nô measured / 1000

tons* N^o aged N^o aged / 1000 tons*

IIa 176 0 0 0 0 0 0 0

IIIa 357 0 0 0 0 0 0 0

IVa 26,315 24,937 95 11 1,492 57 288 11 IVb 2,780 558 20 4 257 92 222 80 IVc 11,112 1,617 15 4 383 34 100 9 VIa 22,055 19,735 89 22 3,320 151 1,151 52

VIIa 60 0 0 0 0 0 0 0

VIIb 22,166 19,667 89 20 3,429 155 1,218 55 VIIc 1,106 0 0 0 0 0 0 0 VIId 15,522 12,081 78 35 8,726 562 1,076 69 VIIe 9,937 5,969 60 17 4,299 433 466 47

VIIf 1 0 0 0 0 0 0 0

VIIg 3 0 0 0 0 0 0 0

VIIh 32,699 27,114 83 20 3,860 118 739 23 VIIj 25,981 17,687 68 29 4,714 181 623 24 VIIIa 23,217 17,690 76 24 8,825 380 405 17 VIIIb 2,953 1,851 63 39 2,717 920 567 192 VIIIcE 6,025 6,023 100 208 14,903 2,474 1,099 182 VIIIcW 8,750 8,750 100 140 10,973 1,254 886 101 VIIId 550 0 0 0 0 0 0 0 IXaN 9,382 9,382 100 173 14,344 1,529 567 60 IXaCN 5,561 5,247 94 1,010 100,510 18,074 2,153 387 IXaCS 4,437 3,010 68 150 12,172 2,743 2,153 485 IXaS 3,731 1,806 48 409 46,705 12,518 2,153 577 sum 234,876 183,124 78 2,315 241,629 1,029 15,866 68

* Values related to WG catch

Coverage and sampling intensity in 2005 improved across the North Sea, in Divisions VIIh and VIIj, and in Divisions VIIIa and VIIIb. It decreased in parts of Division IXa. Despite an increase in coverage in the North Sea, the numbers measured per 1000 t are still low. The working group therefore remains concerned about the low sampling intensity in some Divisions.

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Sardine

The sampling programmes on the assessed sardine stock in VIIIc and IXa are summarised as follows.

YEAR TOTAL CATCH T %CATCH COVERED BY SAMPLING PROGRAMME

SAMPLES MEASURED AGED

1992 164,000 79 788 66,346 4,086 1993 149,600 96 813 68,225 4,821 1994 162,900 83 748 63,788 4,253 1995 138,200 88 716 59,444 4,991 1996 126,900 90 833 73,220 4,830 1997 134,800 97 796 79,969 5,133 1998 209,422 92 1,372 123,754 12,163 1999 101,302 93 849 91,060 8,399 2000 91,718 94 777 92,517 7,753 2001 110,276 92 874 115,738 8,058 2002 99,673 100 814 96,968 10,231 2003 97,831 100 756 93,102 10,629 2004 91,886 100 932 112,218 9,268 2005 97,345 100 925 116,400 9,753

The summarised details of individual sampling programmes in 2005 are shown below. These catches cover all areas where sardine is caught. Landings from the Netherlands (in IV, VII and VIII) have been provided this year to the WG for the first time and are included in the table.

COUNTRY OFFICIAL

CATCH T

%CATCH COVERED BY SAMPLING PROGRAMME

Spain 40,753 100 424 47,775 3,238 Portugal 57,490 100 501 68,625 6,515 France 26,324 58.7 47 3,381 1,382 UK (England 3,457 0 0 0

Ireland 1,448 0 0 0

Germany 221 0 0 0

The Netherlands 2,232¹ 0 0 0

Total 136,120 84 972 119,781 11,135

1Preliminary figures

The overall sampling levels for sardine are adequate for the stock in area VIIIc and IXa.

Length distributions and catch-at-age data for 2005 in areas VIIIa,b were reported to the WG by France. Catches of sardine in Area VII are not sampled. This is considered to be relevant given that catches in this area can be important in some years.

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Anchovy

The sampling programmes carried out on anchovy in 2005 are summarised below. The programmes are shown separately for Subarea VIII and for Division IXa. Sampling throughout Divisions VIIIa, VIIIb and VIIIc appears to be satisfactory.

The overall sampling levels for recent years are shown below

YEAR TOTAL CATCH VIII+IXA

%CATCH COVERED BY SAMPLING PROGRAMME

1992 40,800 92 289 17,112 3,805 1993 39,700 100 323 21,113 6,563 1994 34,600 99 281 17,111 2,923

1995 42,104 83 ? ? ?

1996 38,773 93 214 17,800 4,029 1997 27,440 76 258 18,850 5,194 1998 31,617 100 268 15,520 5,181 1999 40,156 100 397 33,778 10,227 2000 39,497 99 209 18,023 4,713 2001 49,247 58 317 28,615 4,683 2002 26,313 94 216 45,909 4,685 2003 15,864 96 205 22,081 5,324

2004 22,200 97 304 22,436 6,553 2005 5,643 98 145 8,918 3,601

The sampling programmes for France and Spain in Subarea VIII in 2005 are summarised below.

COUNTRY DIVISION OFFICIAL CATCH

%CATCH COVERED BY SAMPLING PROGRAMME

France VIII a, b 952 100 23 1,115 653 Spain∗ VIII a 0 - - - - Spain∗ VIII b 75 100 15 818 770 Spain∗ VIII c

t 101 100 8 733 340

Total VIII 1,128 100 46 2,766 1,713

∗ WG catches

The sampling programmes for the fisheries in Division IXa in 2005 are summarised below.

COUNTRY DIVISION OFFICIAL CATCH

%CATCH COVERED BY

SAMPLING PROGRAMME

Spain∗ IXa 4,389 100 49 6,152 1,888 Portugal IXa 126 0 0 0 0 Total IXa 4,515 97.2 49 6,152 1,888

∗ WG catches

No catches of anchovy from Portugal were sampled for length and age in Division IXa in 2005.

1.3.2 Catch data

Recent working groups have on a number of occasions discussed the accuracy of the catch statistics and the possibility of large scale underreporting or species and area misreporting.

These discussions applied particularly to mackerel and horse mackerel in the northern areas.

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The working group considers that the best estimates of catch it can produce are likely to be an underestimate. Anecdotal information from the UK, and the specific changes reported by the UK in 2005 (see Section 2.8.2), suggest substantial under reporting in the catches. Numerical information is not available for most countries (see section 2.8.3. and 2.8.4 for a discussion on the implications for the assessment of NEA mackerel.

For mackerel and horse mackerel it was concluded that in the southern areas the catch statistics appear to be satisfactory.

For sardines and adult anchovy the WG assumption is that the landings figures are not significantly under reported.

1.3.3 Discards

In pelagic fisheries discarding occurs in a sporadic way compared to demersal fisheries. This is because the nature of pelagic fishing is to pursue schooling fish, creating hauls with low diversity of species and sizes and consequently often extreme fluctuation in discard rates (100% or null discards). The sporadic occurrence of these extreme discard behaviours (such as slippage) may be considered statistically as rare events, which may require specific statistical assumptions and analysis methodologies. Furthermore, the estimators normally used in demersal fisheries to raised sampled discard data to population levels, such as effort or catch related variables, may not be applicable to pelagic fisheries.

Discard estimates of pelagic species from pelagic fisheries and demersal fisheries have been published by several authors. Discard percentages of pelagic species from demersal fisheries were estimated between 3% to 7% (Borges et al., 2005) of the total catch in weight, while from pelagic fisheries were estimated between 4% to 11% (Pierce et al., 2002; Hofstede and Dickey-Collas, 2006). Slipping estimates has only been published for the Portuguese purse seine fishery targeting sardine, with values at around 60% of the total catch (Stratoudakis et al., 2002). Nevertheless, the majority of these estimates were obtained without careful examination of the issues described previously and are therefore open to criticism.

Discard estimates for some countries for mackerel, horse mackerel, anchovy and sardine were provided to the working group. These data included sampling levels and raised discard estimates. The raising methods used, namely the estimators used as a proxy of fishing activity, are not clear. In addition, the associated sampling levels are low, and therefore the data should be treated with caution. The necessary steps involved in providing discard data to stock assessments require further research.

Because of the potential importance of significant discards levels on pelagic species assessments the Working Group again recommends that observers should be placed on board vessels in those areas in which discarding may be a problem. Existing observer programmes should be continued.

Mackerel

The Netherlands, Germany and Scotland provided 2005 discard data on mackerel to the working group. Age and length disaggregated data was only available from the Scottish fishery in the first quarter in area IVa and VIa, a fishery having 29% and 71% of total catches for these areas, respectively. Discard estimates were available from the German freezer trawlers in the first quarter in areas IVa, VIa and VIIj, and in the fourth quarter in area VIIIa.

The Netherlands provided discard estimates for the following areas: IVa-c, VIa, VIIb-e,h,j and VIIIa.

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Horse Mackerel

In the past discards of juvenile horse mackerel have been thought to constitute a problem.

However, in recent years a targeted fishery has developed on juveniles, including 1-year old fish. Therefore discarding of juveniles is now thought to be unlikely. In 2005 the Netherlands and Germany provided discard data on horse mackerel to the working group. Horse mackerel catches of the Netherlands and Germany represent app. 40% of the total catch.

Sardine

A discard programme, sampling purse seine vessels, has recently started in Portugal.

Nevertheless, discard estimates are still not available to the working group. Germany has provided discard estimates of sardine. However, the German catch data is not in the assessment area of sardine.

Anchovy

An onboard observer programme was conducted in 2005 to estimate discards by the Spanish fisheries (trawl, purse seine and artisanal) in the Gulf of Cadiz (see Section 11.2.3).

Preliminary discard estimates for purse seine vessels show that 10.1% of anchovy catch in numbers and 10.7% in weight is discarded. Such ratios should be, however, considered with caution given the extremely high CV associated to the estimates (CV= 157.2 for discarded catch in weight). There are no recent estimates of discards in the French and Spanish anchovy fishery in the Bay of Biscay. It is not known if discarding in this fishery is significant.

1.3.4 Age-reading

Reliable age data are an important pre-requisite in the stock assessment process. The accuracy and precision of these data, for the various species, is kept under constant review by the Working Group.

Mackerel

It is now five years since the last age reading workshop and, therefore, the Working Group on the Assessment of Mackerel, Horse Mackerel, Sardine, and Anchovy again recommends that institutes examine their otolith preparation technique for mackerel before a new mackerel otolith exchange be carried out to evaluate the otolith processing techniques of all institutes that are providing age data to this Working Group.

Horse mackerel

At the 2004 WG meeting possible age reading problems were identified in the age compositions of Dutch and German samples collected in Divisions VIId,e,h (ICES, 2005/ACFM:08 and Zimmermann et al., W21/04). The German catches contained a very high proportion of the 2001 year class, while the Dutch samples contained high proportions of both the 2001 and 2002 year class. A preliminary small-scale otolith exchange after the WG meeting indicated that 2 age readers assigned ages according to the German age reading method but the other 2 readers according to the Dutch age reading method. This is probably due to the known difficulty of interpreting the juvenile rings in the otoliths. The accuracy in age reading is likely to improve once these year classes are mature, because then the interpretation of the rings at the time they were juveniles becomes easier. In 2005 the age distribution from Dutch and German samples from the same area was again significantly different.

A workshop on age reading horse mackerel will take place in the Netherlands in November 2006 to detect, evaluate and try to solve the observed problems in age reading across all the horse mackerel stocks.

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Anchovy

For the Bay of Biscay anchovy, two exchanges of otoliths took place some years ago, of which results were available at the previous meeting (Astudillo et al. 1990 & Villamor et al.

WD 1996). An exchange of otoliths for anchovy in IXa (Cadiz) has also taken place (Garcia 1998).

In 2001 a new exchange, followed by a workshop in 2002 on age determination of otoliths from anchovy took place. The major goal was to identify major difficulties in age determination and standardise anchovy otolith ageing criteria for the Bay of Biscay and for division IXa (Uriarte 2002).

In 2005 an otolith exchange programme for anchovy from the Bay of Biscay took place. The results of this exchange were submitted to the 2006 ICES Planning Group on Commercial Catch, Discards and Biological Sampling (PGCCDBS) held in February 2006. The exchange was made between French and Spanish institutes monitoring anchovy. Two readers from each institute (AZTI, IEO, IFREMER) read a total of 510 otoliths to evaluate current precision in otolith age reading of anchovy and detect major difficulties. The major findings were that:

• The average percentage agreement (90.9 %) and CV (13.9%) are quite good and quite similar to the results achieved in the 2002 workshop (agreement of 92% with a CV of 10%)

• During the first half of the year the percentage agreement is high (93%) and precision is high (CV low, 8.1%) with a small amount of bias (0.03).

• During the second half of the year the percentage agreement is lower (87.7%) and precision decreases (to 22%) with a small amount of bias (0.04). However, already noticeable since age 2: there are two sets of readers diverging during the second half of the year on the allocation of a certain amount of otoliths either to age 1 or 2.

• Depending on the correct reading of those otoliths the percentage in the catches of 2 year olds could have doubled or halved for the second half of the year.

• The ultimate reasons for these discrepancies have not yet been examined over individual otolith cases of disagreement and their examination is left for the next workshop.

A workshop is planned to take place in the autumn of 2006 to examine the results from the exchange programme and to improve the consistency and accuracy of age readers. The WG recommends that this workshop should, in particular, address the abnormal abundance of 2-ring fish observed in the 2006 spring surveys to determine whether it is the result of incorrect age determination.

The working group endorses the workshop initiative.

Sardine

A workshop on sardine age reading took place in June 2005 to discuss the results of an otolith exchange carried out during 2004. The otolith exchange and workshop aimed to evaluate readers’ agreement and ageing precision, to assess the extent of ageing difficulties previously identified (identification of the first annual ring and ageing of older individuals) and to propose guidelines for their minimization. The consistency of age readings in time (comparison of the 1980s, 1990s and 2004) and in space (comparison with Mediterranean and northwest African areas) was also explored and the consequences of the assumed birth date for the estimation of growth were discussed. In addition, profiting from the experience of the workshop attendants, biological sampling methodologies (assignment of sexual maturity

ACFM3606.pdf (25.95Mb)

ICES WGMHSA Report 2006

ICES Advisory Committee on Fishery Management ICES CM 2006/ACFM:36

Report of the Working Group on the Assessment of Mackerel, Horse Mackerel, Sardine and Anchovy (WGMHSA)

5 - 14 September 2006

Galway, Ireland

International Council for the Exploration of the Sea Conseil International pour l’Exploration de la Mer

Contents

0 Executive Summary

1 Introduction