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ICES WGANC REPORT 2 0 0 8

ICES ADVISORY COMMITTEE

ICES CM 2 0 0 8 / ACOM:0 4

Report of t he Working Group on Anchovy (WGANC)

13 - 16 June 2008

ICES Headquart ers, Copenhagen

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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

[email protected]

Recommended format for purposes of citation:

ICES. 2008. Report of the Working Group on Anchovy (WGANC), 13 - 16 June 2008, ICES Headquarters, Copenhagen. ICES CM 2008 ACOM:04. 226 pp.

For permission to reproduce material from this publication, please apply to the Gen- eral 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 WGANC REPORT 2008 i

Co n t e n t s

1 Introduction ... 1

1.1 Terms of reference... 1

1.2 Comments to the new WG structure and working schedule... 1

2 Anchovy general... 2

3 Anchovy in Subarea VIII (Bay of Biscay) ... 2

3.1 ACFM advice for 2007 and STECF recommendations... 2

3.2 The fishery in 2007 and 2008... 4

3.2.1 Fishing fleets ... 4

3.2.2 Catches... 5

3.2.3 Catch numbers at age ... 5

3.2.4 Weights and lengths at age in the catch ... 6

3.3 Biological data ... 6

3.3.1 Maturity at age ... 6

3.3.2 Natural mortality and weight at age in the stock ... 6

3.4 Fishey independent information... 6

3.4.1 DEPM surveys ... 6

3.4.2 Acoustic survey 2008 ... 8

3.4.3 Historical series DEPM & acoustic surveys... 11

3.4.4 Juveniles surveys... 12

3.5 State of the stock... 15

3.5.1 Method... 15

3.5.2 Data and model exploration ... 17

3.5.3 Final assessment ... 18

3.5.4 Quality of the assessment... 18

3.6 Prediction ... 20

3.6.1 Recruitment prediction... 20

3.7 Management considerations... 23

3.7.1 Reference points for management purposes ... 23

3.7.2 Development of management plans... 24

3.7.3 Recent recruitment failure... 26

4 Anchovy in Division IXa ... 29

4.1 ACFM Advice Applicable to 2007 and 2008... 29

4.2 The Fishery in 2007 ... 30

4.2.1 Fleet composition and métiers ... 30

4.2.2 Catches in 2007 ... 31

4.2.3 Discards ... 34

4.2.4 Effort and Catch per Unit Effort... 34

4.3 Biological Data... 37

4.3.1 Weights at age in the stock... 37

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ii | ICES WGANC REPORT 2008

4.3.2 Maturity at Age ... 37

4.3.3 Natural Mortality ... 37

4.4 Fishery-Independent Information ... 38

4.4.1 Acoustic Surveys ... 38

4.4.2 Egg Surveys... 42

4.4.3 Recruitment surveys ... 42

4.5 Data exploration... 43

4.5.1 Methods ... 43

4.5.2 Exploratory runs... 44

4.5.3 Conclusions of the Exploratory Assessments... 45

4.6 Predictions... 46

4.7 Management considerations... 46

4.7.1 Stock definitions ... 46

4.7.2 Reference points for management purposes ... 46

4.7.3 Harvest Control Rules ... 46

4.7.4 Current management situation ... 47

4.7.5 Scientific advice and contributions ... 48

5 References... 49

Annex 1: Revision of the JUVEN A 2006 biomass estimation and comparison between JUVENA and DEPM indices ... 129

Annex 2: D istribution pattern of anchovy abundance and biomass in D ivi- sion IXa from research surveys in 2007 and 2008 ... 141

Annex 3: Preliminary estimates of the Spawning Stock Biomass of the Bay of Bis- cay anchovy (Engraulis encrasicolus, L.) applying the DEPM... 167

Annex 4: Direct assessment of anchovy and other pelagic species by the PELGAS08 acoustic survey... 189

Annex 5: List of Participants ... 216

Annex 6: Technical Minutes from the Review Group on Anchovy (RGANC) ... 218

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ICES WGANC REPORT 2008 1

1 In t r o d u ct i o n

1 .1 Ter m s o f r ef er en ce

Council resolution 2007/2/ACOM04:

The Working Grou p on Anchovy [WGAN C] (Chair: Dankert Skagen*, N orw ay (to be confirm ed )) w ill be established and w ill m eet at ICES H ead qu arters, 13-16 Ju ne 2008 to:

a ) collate, review and , w hen essential, revise w orking d ocu m ents on d ata and/or assessments of the status and forecasts for (Generic ToR 1-4):

i) anchovy in Division IXa;

ii ) anchovy in Subarea VIII (Bay of Biscay).

The assessm ents w ill be carried ou t in N ational Laboratories coord inated in the table below:

b ) su m m arise the statu s of the stocks and catch op tions forecasts based on the u p d ate assessm ents and w here it is p art of the stand ard p rocedure, particularly include environmental, ecosystem and fisheries information.

WGANC will report by 19 June 2008 for the attention of ACOM.

These terms of reference are adapted to the situations where most assessments can be d one beforehand and p resented as Working Docu m ents. For the Anchovy, notably the Anchovy in Su barea VIII, w hich is the m ain stock, the assessm ent and ad vice is a fast track in-year advice. The purpose is to translate recent survey and catch data into an ad vice once they are available. The su rveys, w hich are the backbone of the assessm ent, w ere finished ju st a few d ays before the m eeting. Therefore, the m ain issu e at the m eeting w as to consid er the recent d ata and to p erform an assessm ent and catch forecast based on preliminary results from the surveys. The second issue was to rep ort on recent p rogress in scientific w ork relating to assessing and ad vising on anchovy.

1 .2 Co m m en t s t o t h e n ew WG st r u ct u r e an d w o r k i n g sch ed u l e.

The tim e for the m eeting w as constrained by the tim ing of the su rveys on one hand and the need for m anagers to im p lem ent the ad vice im m ed iately on the other. It w as p ossible to ad d ress the term s of reference at this m eeting, bu t only becau se no m ajor obstacles ap p eared . Any d ifficu lties w ith d ata or m od el assu m p tions, or even m ajor alterations of the state of the stock that w ou ld requ ire a d ifferent ad vice, w ou ld have p reclu d ed finalizing the task. It is hard ly p ossible to start the m eeting closer to the finalizing of the su rveys. H ence, an extension of the m eeting tim e w ill have to lead to a d elayed ad vice. There is a clear trad e-off betw een the tim ing of the ad vice and the risk that no ad vice can be p rovid ed , w hich w ill hap p en once u nforeseen p roblem s ap pear, and also the risk of errors in the advice.

Previou sly, the assessm ent WG has served a foru m for com m u nication of d evelop- m ents both in biology, ecology, assessm ent and m anagem ent of anchovy. With the new w orking grou p stru ctu re, the short m eeting for u p d ating the assessm ent cannot serve that p u rp ose. The WGAN C considers that it is im p ortant that these asp ects are taken care of. Parts of the issu es w ill be p icked u p by the WGACEGG, in p articu lar analyses of su rvey d ata and the integration of the su rvey resu lts in an environm ental

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2 ICES WGANC REPORT 2008

and ecological context. There is, how ever, also a strong need for a benchm ark w orkshop to consolid ate im p lications in the assessm ent of the revisions of egg su rvey calcu lation m ethod s, d efinition of reference p oints as w ell as the d evelop m ent of m anagem ent strategies. Finally, it is noted that there is a strong interaction betw een WGAN C and variou s bod ies in the EC, w here coop eration and coord ination shou ld be ensu red and d ou ble w ork avoid ed . In p articu lar, w hen the fishery can be re- op ened and the inform ation on incom ing year classes im p roves (See Section 3.4.4.), there will be an need for an updated advice for the fishery in the spring.

2 An ch o vy g en er al

The distribution of anchovy in Atlantic European waters is nowadays mainly concentrated in tw o w ell d efined areas; the Bay of Biscay and the Gu lf of Cád iz (Figu re 2.1).

H ow ever, som e resid u al coastal p op u lations exists along the Iberian coast (see Figu re 2.1 and Section 4), as w ell as in the English Channel, Celtic Sea and N orth Sea (Beare et al. 2004; ICES 2007a). Anchovy p op u lation in the northern areas seem s to show an increase in recent years (Beare et al. 2004; ICES, 2004), although time series of anchovy abu nd ance in those areas are incom p lete, m aking it d ifficu lt to analyze the abu n- d ance trend s. Within the Iberian p eninsu la and ou tsid e the m ain nu cleu s of the Bay of Biscay and the Gu lf of Cád iz, resilient anchovy p op u lations have been d etected in all fishery ind ep end ent su rveys (ICES, 2007b) and p reviou s record s on large catches in ICES area IXa N orth and Central N orth (Section 4.2.2.1) su ggest that abu nd ance in those areas have been high in early years of the tim e series. In the sou th, ou tsid e the Gu lf of Cád iz anchovy is abu nd ant to the East of the Strait of Gibraltar, in the Med i- terranean Sea (GFCM, 2002) as well as in northern Africa, where a combined Spanish- Morocco fishery p rod u ces land ings of u p to 12000 tn (Millan, 1992; García-Isarch et al., 2008).

Desp ite the know n flu ctu ations in anchovy d istribu tion and abu nd ance along the Atlantic Eu rop ean w aters (see also Section 3.7.3.1), and even in the cu rrent low abu n- dance situation in the Bay of Biscay, both the Bay of Biscay and the Gulf of Cádiz continu e to be regard ed as the m ain nu cleu s for Atlanto-Eu rop ean anchovy. Migration intensity betw een those m ain nu cleu s and su rrou nd ing areas are how ever u nknow n and d ata for Atlanto-Eu rop ean anchovy ou tsid e the m ain nu cleu s is scarce and is not rou tinely rep orted to ICES WGAN C. This WG recom m end s that anchovy land ings, length and age d istribu tion are rou tinely record ed in the d ifferent EU sam p ling plans, and reported to this WG.

3 An ch o vy i n Su b ar ea VIII (Bay o f Bi scay)

3 .1 ACFM ad vi ce f o r 2 0 0 7 an d STECF r eco m m en d at i o n s

In Ju ly 2005 the fishery w as closed d u e to the low levels of biom ass of the anchovy population. This closu re has been p rolonged step w ise, and is at p resent valid u ntil July 2008.

In Decem ber 2006, the EU Cou ncil d ecid ed to continu e the fishery closu re and established a zero TAC for the Bay of Biscay anchovy in 2007. In ad d ition, the EU Cou ncil stated that to gather information on the state ofthe stock, after consultation of the STECF and under the supervision of the Commission, a maximum of 10 % of the French and Spanish fishing effort (20 Spanish vessels and 8 French vessels) may be deployed in zone VIII for ex- perimental fishing with scientific observers on board from 15 A pril until 15 June 2007. Catch reports have to be submitted to the Commission every 15 days by the M ember States con-

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cerned. The Commission will suspend the experimental fishery once sufficient data has been collected. The Commission will then, as appropriate, adopt the decision foreseen in Article 5(5) of this Regulation on the basis of an STECF advice.

Accord ingly, in an attem p t to m axim ise the u tility of any inform ation from the fishery for stock assessm ent, the STECF convened an exp ert w orking grou p in Febru ary 2007. The STECF considered that the current spring surveys are already sufficient to assess the status of the stock in spring and provide management advice for the rest of the yearand that a free commercial fishery would not provide any useful additional data for an evaluation of stock status or incoming year-class strength in 2007. Therefore, the STECF recom- mended that the commercial vessel effort proposed for such a fishery would be better de- ployed in a consort role to provide supporting fishing and surveying activity for the existing research vessel surveys in the spring of 2007 (PELGA S, PELA CUS and BIOM A N ) and thatif additional commercial vessel effort beyond that to support the surveys is allowed to take place in 2007, a multi-vessel acoustic/fishing survey ( Rake survey) should be carried out by commercial vessels.

In Ap ril 2007, the Com m ission and the concerned m em ber states agreed the cond i- tions for the 10 fishing vessels (7 Sp anish and 3 French vessels) p articip ating in the consort su rveys for the BIOMAN and PELGAS Sp ring su rveys and for the exp eri- m ental fishing of the rem aining 18 vessels (13 Sp anish and 5 French vessels). The Sp anish p u rse seines not p articip ating in the consort su rveys collaborated in a rake survey, whereas the French vessels conducted an experimental fishing.

The STECF m et again in Ju ne 2007 to assess the anchovy sp aw ning stock biom ass based on the inform ation from the sp ring scientific su rveys and to analyse the valu e of the information gathered by the commercial vessels. The STECF noted that there are clear signs that the stock situation has improved compared to 2005. However, spawning stock biomass remains very low and maximum protection of the remaining spawning population is required. STECF recom m end ed that the fishery should remain closed in 2008 until reliable estimates of the 2008 SSB and 2007 year class become available based on the results from the spring 2008 acoustic and DEPM surveys. This implies a closure of the fishery until at least July 2008.

Follow ing the STECF ad vice and after close exam ination of the su bm issions m ad e by m em ber states, the Com m ission d ecid ed on 19^thJu ly 2007 that the Bay of Biscay anchovy fishery will not be reopened until the end of the year.

In October 2007 ICES stated : Based on the most recent estimates of SSB, ICES classifies the stock as being at risk of reduced reproductive capacity. SSB in 2007 is estimated to be between Blim and Bpa, and is estimated at 27% higher than in 2006. Low recruitment since 2001 and almost complete recruitment failure of the 2004 year class are the primary causes of the stock collapse.

The ACFM ad vice w as: ICES recommends that the fishery should remain closed in 2008 until reliable estimates of the 2008 SSB and 2007 year class, based on the results from the spring 2008 acoustic and DEPM surveys, become available. This implies a closure of the fish- ery until at least July 2008.

The ICES ad vice w as end orsed by STECF and the Cou ncil of fishing m inistries the Eu rop ean Union d ecid ed to keep the closu re of the fishery u ntil Ju ne 2008, w hen a revision ou ght to be m ad e accord ing to the scientific inform ation collected d u ring the first half of 2008 and to the d egree of form u lation of a m u ltiannu al p lan for the m an- agement of anchovy (Council Regulation Nº 40/2008 of TACs and Quotas). There was no experimental fishery in spring 2008.

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Du ring the first half of 2008 a cou p le of m eetings to d eal w ith a Long Term Manage- ment plan for the anchovy fishery were convened by STECF (see section 3.7.2).

3 .2 Th e f i sh er y i n 2 0 0 7 an d 2 0 0 8

There w as no com m ercial fishery for anchovy in the Bay of Biscay in 2007 and 2008.

The text below refers to the fishery prior to the closure.

3 .2 .1 Fi sh i n g f l eet s

Tw o fleets op erate on anchovy in the Bay of Biscay: Sp anish p u rse seines and French fleet constitu ted of p u rse seiners and p elagic traw lers. The p attern of each fishery has not changed in recent years.

Sp anish p u rse seine fleet: The Sp anish fleet is com p osed of p u rse seiners (of abou t 200 boats) (Table 3.2.1.1) that op erate at the sou th-eastern corner of the Bay of Biscay (in Divisions VIIIc and b), m ainly in sp ring, w hen u su ally m ore than 80 % of the Sp anish annu al catches occu rred . The m ajor p art of this fleet goes for tu na fishing in su m m er tim e and by then they u se sm all anchovies as live bait for its fishing. These catches are not land ed bu t the observations collected from logbooks and fisherm an interview (u p to 1999) ind icate that they are su p p osed to be less than 5 % of the total Sp anish catches. The Sp anish fleet d id not go to fish in Su barea VIIIa since 2002. The number of Spanish purse seiners is decreasing since 1997.

French fleet: the main catches are produced by pair trawlers. The French fishery starts normally at the beginning of the year in the centre of the Bay of Biscay. Progressively, the fishery is m oving tow ard s the sou th of the Bay of Biscay (generally in Ap ril). Af- ter a volu ntary break of the p elagic fishery (bilateral agreem ent) in Ap ril and May, the fishery m oves north, and reaches som etim es thenorthern p art of VIIIa in Au gu st or Sep tem ber. Later, the fishery m oves to the centre of the bay. The m ajor fishing areas are the north of the VIIIb in the first half of the year and VIIIa, m ainly, d u ring the second half. Area VIIIc is p rohibited to the French p elagic fleet. A p art of p elagic traw lers are op p ortu nistic and p olyvalent: looking at annu al catches vessel by vessel, a high nu m ber of them can catch a sm all am ou nt of anchovy at least once a year.

Therefore the nu m ber of French p elagic traw lers involved in the anchovy fishery is variable: it depends on the biomass of fish available (Duhamel E. et al, WD 2004).

Table 3.2.1.1 show s for the French fleet, the nu m ber of vessels that have cau ght a significant am ou nt of anchovy each year, and not the total nu m ber of vessels. A threshold of 50 tons p er year has been d ecid ed to sep arate target traw lers to occasional ones. Becau se of the low biom ass d u ring the last 3 years and the ban on the anchovy fishery for the second half of years 2005 and 2006, it has been necessary to consid er a low er threshold of annu al catches to select com m ercial vessels that really target anchovy in these years. This has been m ad e by d ecreasing the threshold of 50 tons p er years to 10 tons. Since 1995 the nu m ber of p elagic traw lers w as qu ite stable (abou t 50).

French p u rse seiners are also op p ortu nistic and they alw ays op erate arou nd their hom e harbor, in coastal w aters. Catches of anchovy by p u rse seiners are not regu lar becau se their real target sp ecies is sard ine. Som e French p u rse seiners located in the Basqu e cou ntry fish m ainly in sp ring in VIIIb and the Brittanish one fish occasionally anchovy during autumn in the north of the Bay of Biscay. The total number of French p u rse seiners are slightly increasing since 2000 (33 in 2000; 41 estim ated in 2004), bu t it does not imply a real increase in term of catches as their real target is still sardine.

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3 .2 .2 Cat ch es

3 .2 .2 .1 Cat ch st at i st i cs

H istorically catches p eaked in the sixties (Table 3.2.2.1 and Figu re 3.2.2.1), d rop p ed to low valu es in the eighties and recover in the context of the cu rrent international m ixed fishery in the nineties. Since 2002 a p rogressive d ecrease of catches occurred u ntil the collap se of the fishery in 2005, after w hich rep eated closu res of the fishery are taking place in the context of management to rebuild the anchovy population.

In the p eriod before recent closu res of the fishery (1992-2004), m ost of Sp anish land- ings (85 %) w ere u su ally cau ght in d ivisions VIIIc and VIIIb in sp ring, w hile 35 % of the French land ings are cau ght in d ivisions VIIIb in the first half of the year and 65%

in summer and autumn in division VIIIa (Table 3.2.4.1).

Catches in 2007 :The fishery w as still closed in 2007 ju st an exp erim ental fishery w as allow ed d u ring sp ring. After the STECF ad vice in Ju ne from the sp ring su rvey s SSB estimates, the fishery was totally closed in July 19th 2007.

N o catches have been taken d u ring the first half of 2008 given the closu re of the fishery decided by the EU fishery Council.

3 .2 .2 .2 Di scar d s

There are no estimates of discards in the anchovy fishery but it did not appear to be a significant problem.

3 .2 .3 Ex p er i m en t al f i sh i n g

An exp erim ental fishery took p lace d u ring sp ring 2007. Fisherm en w ere allow ed to sell their catches u nd er strict cond itions, in ord er to avoid a too strong fishing p res- su re on an u ncertain biom ass and to avoid scientific su rveys d istu rbance. Land ings by France am ou nted to 140 tons d u ring this exp erim ental fishery. Sp anish fisherm en d id not p articip ate in this exp erim ental fishery and therefore, no significant land ings w ere rep orted for Sp ain. Arou nd 1 ton w as cau ght w hen they p erform ed a Rake su r- vey in 2007 to locate fish concentrations.

A proper report of this French fishery and the Spanish Rake surveys were included in last year rep orts (ICES 2007sections 10.2.3). For the p u rp oses of the cu rrent u p d ate assessm ent no inp u t from these exp erim ental fisheries are inclu d ed in the assessment.

3 .2 .4 Cat ch n u m b er s at ag e

Table 3.2.4.1 record s the age com p osition of the international catches since 1987, on a half-yearly basis. Usu ally 1-year-old anchovies have d om inated in the catches d u ring both halves of m ost of the years. The few cases w hen 2 years old anchovies are p re- dominant in the international catches during the first half of the year are indicative of failu res of the 1 year old recru its as in 1999, 2002 and 2005. Figu re 3.2.4.1 show the Spanish and French catch at age compositions of the first half of the year since 1987.

No age composition of the French experimental fishery catches during the first half of 2007 was available for the WG.

The catches of anchovy corresp ond ing to the Sp anish live bait fishery have not been p rovid ed since 2000. The d ata available for the p eriod 1987 1999 w as inclu d ed in

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table 10.3.1.3 of last year rep ort. These are trad itionally catches of sm all anchovy mainly of 0 and 1 year old groups amounting about 5 hundred tonnes or less.

3 .2 .5 Wei g h t s an d l en g t h s at ag e i n t h e cat ch

The series of m ean w eight at age in the fishery by half year, from 1987 to 2006, is show n in Table 3.2.5.1 The French m ean w eights at age in the catches are based on biological sam plings from scientific survey and commercial catches.

Sp anish m ean w eights at age w ere calcu lated from rou tine biological sam p ling of commercial catches.

Sam p ling d u ring second half of 2006 w as very p oor becau se of the low level of catches (closure in July). Therefore, the weights at age for this period are not accurate.

This has no impact on assessment as these data are not used in Bayesian mod el.

3 .3 Bi o l o g i cal d at a 3 .3 .1 Mat u r i t y at ag e

As rep orted in p reviou s years rep orts, anchovies are fu lly m atu re as soon as they reach 1 year old , at the follow ing sp ring after they hatched . N o d ifference in sp ecific fecu nd ity (nu m ber of eggs p er gram of fem ale bod y w eight) accord ing to age has been found so far (Motos, 1994).

3 .3 .2 Nat u r al m o r t al i t y an d w ei g h t at ag e i n t h e st o ck

N atu ral m ortality and grow th are com bined in the g p aram eter u sed in the tw o- stage biom ass d ynam ic m od el. The valu e for natu ral m ortality is fixed (M = 1.2) and the growth (G) is determ ined by the historical w eights at age. Thu s the g p aram eter is estimated from the subtraction: M G (see section 3.5.1).

3 .4 Fi sh ey i n d ep en d en t i n f o r m at i o n 3 .4 .1 DEPM su r veys

DEPM (Daily Egg Prod u ction Method ) su rveys to estim ate the sp aw ning stock bio- m ass (SSB) in the Bay of Biscay anchovy have been im p lem ented from 1987 to 2008 with a gap in 1993 (Table 3.4.1.1)

3 .4 .1 .1 Met h o d o l o g i cal i ssu es

In 2007 and 2008 DEPM su rveys, the d aily egg p rod u ction (P0) and d aily m ortality rates (Z) w ere estim ated by fitting an exp onential m ortality m od el to the egg abu n- d ance by cohorts and corresp ond ing m ean age u sing a Generalized Linear Mod el w ith N egative Binom ial d istribu tion and log link instead of fitting a Weighted N on Linear Regression Mod el as w as u sed in the historical series. That fitting w as recom- m end ed and ad op ted by the SGSBSA in 2003 to im p rove the m ethod bu t this change d oes not affect to the P0 and z estim ates w hich m eans that the p resent estim ates are comparable with the ones estimated in the past.

The m ethod related to the sp aw ning fraction has been revised in WGACEGG (ICES, 2007b). This revision w ill lead to changes in the sp aw ning stock biom ass estimates p rovid ed by the DEPM. H ow ever a fu ll revision for all years has not been com p leted . Once finished, it will be made available to WGACEGG for review and adoption.

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3 .4 .1 .2 DEPM su r vey 2 0 0 8

3 .4 .1 .2 .1 Descr i p t i o n o f su r vey

The research su rvey BIOMAN 2008 for the ap p lication of the Daily Egg Prod u ction Method (DEPM) in the Bay of Biscay anchovy has been cond u cted in May 2008 from the 6th to the 26th covering the w hole sp aw ning area of the sp ecies. This year tw o vessels w ere u se: the R/V Investigad or to sam p le the p lankton (544 stations) and the R/V Emma Bardán to sample the adults (39 pelagic hauls).

The area covered w as the sou theast of the Bay of Biscay, w hich corresp ond s to the m ain sp aw ning area and season of anchovy. The lim it of the sp aw ning area w as w ell d elim ited : 3º33 W to the West in the Cantabrian Coast and 48º10 N to the N orth in the French p latform . The su rvey started from the West of Santand er (4º14 W), and covered the Cantabrian Coast eastw ard s u p to Pasajes. Then, the su rvey continu ed to the north, in ord er to find the N orthern lim it of the sp aw ning area (Figu re 3.4.1.1). The species composition in the trawl hauls is shown in Figure 3.4.1.2.

The sam p les obtained w ere fixed in form ald ehyd e. After 6h of fixing, anchovy, sar- d ine and other sp ecies eggs w ere id entified and sorted ou t. All the sam p les w ere sorted on-board.

The Continu ou s Und erw ay Fish Egg Sam p ler (CUFES) w as also u sed to record the eggs fou nd at 3m d ep th (1,200 stations). The sam p les obtained w ere im m ed iately checked u nd er the m icroscop e so that p resence/absence of anchovy eggs w as d e- tected in real tim e. This allow ed know ing w hether there w ere anchovy eggs in the area. When no anchovy eggs w ere fou nd in 6 consecu tive CUFES sam p les in the oce- anic area transect was left.

3 .4 .1 .2 .2 Eg g p r o d u ct i o n est i m at e

The total area surveyed was 69, 150 Km2 and the spawning area was 33,502Km2.

From 544 PairoVET, 237 w ere p ositive for anchovy eggs (43%) w ith an average of 7 eggs/0.1m 2 p er station and a m axim u m of 306 eggs/0.1m 2 in the area of Cap Breton once p assed the isoline of 200m in transect 29. (The highest observation in Figu re 3.4.1.3)

The anchovy eggs w ere concentrated in tw o p rincip al areas: the area of Cap Breton and the area of influ ence of the Girond e River in the area of 50m d ep th, close to the coast. Egg abundance was scarce across the Cantabrian coast.

Once the staged eggs w ere transform ed into d aily cohort abu nd ances u sing the Bayesian ageing m ethod , Daily egg p rod u ction (P0) and d aily m ortality rates (Z) w ere estim ated by fitting an exp onential m ortality m od el to the egg abu nd ance by cohorts and corresp ond ing m ean age w ith a glm (generalized linear m od el) w ith a negative binom ial and log link. Ptot w as calcu lated as the p rod u ct of the sp aw ning area and the daily egg production rate (P0).

Two different estimates of P0 and z were presented to the WG (Santos WD, Annex 3), based on the inclu sion or exclu sion of a station w hich show s a large abu nd ance of eggs in the second d aily cohort. The d ifferent estim ates of P0 and z d id not show large d ifferences, and the WD recom m end ed u sing the estim ates exclu d ing the station to estim ate z, consid ered as an ou tlier. H ow ever, the WG d ecid ed to u se the estim ate w ithou t exclu d ing any station, becau se the observed situ ation is com m on in DEPM su rveys, there w as no clear ind ication that the station cou ld be consid ered er- roneou s, and becau se the error d istribu tion u sed (negative binom ial, recom m end ed

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by ICES SGSBSA and WGACEGG; ICES 2004; ICES, 2007b) is consid ered to be robu st to stations that show large abu nd ances. The influ ence of this station in the estim ate is m inor. The estim ates are given in Table 3.4.1.2 and the final m ortality cu rve m od el used is shown in Figure 3.4.1.3.

3 .4 .1 .2 .3 Ad u l t sam p l i n g an d ad u l t p ar am et er s

The ad u lt sam p les w ere obtained on-board the p elagic traw ler R/V Em m a Bard án.

This vessel w as covering the sam e area as the p lankton vessel. When the p lankton vessel encou ntered areas w ith anchovy eggs, the R/V Em m a Bard án w as d irect to those areas to fish. The fishing hau ls for ad u lt sam p ling are su m m arised in Annex I (Santos WD, Annex 3).

From the 39 p elagic traw l hau ls 29 had anchovy bu t only on 20 w as fou nd a m ini- m u m of 60 anchovies that is the m inim u m to consid er the sam p le for the analysis.

The sp atial d istribu tion of the sam p les and their com p osition is show ed in Figu re 3.4.1.2. Figu res show ing, the p ositive hau ls for anchovy and the cap tu re, the ad u lts m ean w eight and ad u lts m ean size, are in Santos WD, Annex 3. Figu re 3.4.1.4 show s the age composition by haul.

As the adult samples are not fully processed yet, the DF estimate was obtained from a linear regression m od el betw een DF and sea su rface tem p eratu re (SST), follow ing the procedure u sed in STECF (2006). The coefficient of d eterm ination of the relation betw een DF and SST w as 35%, and the p red icted Daily Fecu nd ity valu e p red icted by this regression is 67.44 egg/gram (CV = 0.041), w ith 95 % confid ence intervals 42.5 and 92.4 eggs/gram.

3 .4 .1 .2 .4 SSB est i m at e

A p relim inary SSB estim ate is obtained as the ratio betw een the total d aily egg p ro- d u ction (Ptot) and the d aily fecu nd ity (DF) estim ates from the linear regression m od el. The p relim inary biom ass estim ate in that m anner is 26,461 t w ith a coefficient of variation of 19% what is similar to the last year estimate (25,973 t; CV 14%).

Ap p roxim ately 58% (CV=10%) of the p op u lation in m illions of ind ivid u als (71% in m ass) is old er than one year. This ind icates a new failu re in the recru itm ent, as in the last years.

3 .4 .2 Aco u st i c su r vey 2 0 0 8

3 .4 .2 .1 Descr i p t i o n o f su r vey

The 2008 acou stic su rvey PELGAS08 (Massé & al. - WD 2008 Annex 4) w as carried ou t in the Bay of Biscay from Ap ril 26th to May 26th on board the French research vessel Thalassa. The objective w as the sam e than since 2000, to stu d y the abu nd ance and d istribu tion of p elagic fish in the Bay of Biscay and to stu d y the p elagic ecosystem as a w hole. The target sp ecies w ere m ainly anchovy and sard ine bu t w ere considered in a multi-species context.

Another acou stic su rvey (PELACUS0408) w as carried ou t ju st before PELGAS08 (28 March 23 Ap ril) and su rveyed the Galician and Cantabrian area. This area d oes not cover the m ain d istribu tion area for Bay of Biscay anchovy, bu t nevertheless p rovid e som e inform ation on the d istribu tion, abu nd ance and biology of anchovy in the sou thern lim it of the Bay of Biscay anchovy (see Section 2 for general d istribu tion of anchovy in Atlanto-Eu rop ean w aters). Anchovy in PELACUS0408 w as only observed in a few traw ls in the Galician area and in the sou thern Bay of Biscay area (Figu re

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3.4.2.1). Abu nd ance in the Galician area and in VIIIc w as sim ilar to p reviou s years (300 and 470 tn resp ectively), w hile abu nd ance in the sou thern VIIIb area (not fu lly covered by this su rvey) is higher than in p reviou s years (12000 tn). Size stru ctu re show average to large individuals in the Galician area and in VIIIc (modes of 16.5 and 15.5 cm resp ectively), and large ind ivid u als in sou thern Bay of Biscay (m od e of 18 cm).

In the rest of the section,resu lts w ill refer to the PELGAS08 su rvey, as those are the ones used for assessment.

To obtain an op tim al horizontal and vertical d escrip tion of the p elagic ecosystem in the area, tw o typ es of actions w ere com bined : i) Continu ou s acqu isition by storing acou stic d ata (from five d ifferent frequ encies : 18, 38, 70, 120 & 200 kH z) and p u m p- ing sea-w ater u nd er the su rface, in ord er to evalu ate the d istribu tion of fish eggs u s- ing CUFES system , and ii) d iscrete sam p ling at stations (by traw ls, p lankton nets, CTD). Concu rrently, a visu al cou nting and id entification of cetaceans and of bird s (from board) was carried out in order to characterize the higher level predators of the pelagic ecosystem.

A consort survey was organized with French pair trawlers. This approach, in the continu ity of last year su rvey, w as officially d ecid ed three w eeks before the PELGAS su rvey and organized taking into accou nt the last year exp erience. They w ere this year equ ip p ed w ith a p recision w eighting m achine and a calibrated echo-sounders (Sim rad ER60 70 kH z) able to store d ata at a stand ard form at. Their consort su rveying and fishing op erations can be so consid ered this year as qu alitative and qu antita- tive as w ell. The catches and biological d ata have been d irectly u sed at the sam e level than Thalassa one for identification and biological characterization. The echo sounder w as im p lem ented on a sm all tow ed bod y and becau se of a non su fficient stability d u ring the first 2 w eeks (15m vessel length) the d ata w as stored only d u ring sm all sequ ences w hen notable echo-traces w ere observed and m ainly after fishing. Com- m ercial vessel acou stic d ata w ill be p rocessed later in ord er to com p are the echo typ es and energies to Thalassa one in id entical p lace or sim ilar cond itions. They w ere not available for the present WG.

The fou r com m ercial vessels (tw o p air traw lers) p articip ating to PELGAS08 su rvey were:

- "le Natif / la Roumasse" from St Gilles Croix de vie (from 27th april to 12th may) - "Cintharth / Marilude" from La Turballe (from 15th to 21th may)

The collaboration betw een Thalassa and com m ercial vessels w as excellent. It w as a very good op p ortu nity to exp lain to fisherm en ou r m ethod ology and m ore, to verify that both scientists and fisherm en observe the sam e typ es of echo-traces and that the catches w ere w ell com p arable (in p rop ortion of sp ecies and , m ost of the tim e, in quantity as well).

Only 3 d ays of rather bad w eather occu rred d u ring the first w eek of su rvey bu t it d id n't d istu rb that m u ch the stability and it w as consid ered that the w hole p otential area for anchovy d istribu tion w as covered in su itable cond itions and its biom ass estim ate by acou stic w as p ossible. The op erations carried ou t by Thalassa and by p ro- fessional vessels were all carried out during day time.

Acou stic d ata w ere collected by Thalassa along 2800 nau tical m iles, u p on w hich 1850 nautical m iles w ill be u sed for biom ass estim ate (Figu re 3.4.2.2). A total of 102 hau ls w ere carried ou t d u ring the assessm ent coverage inclu d ing 46 hau ls by Thalassa and 56 hau ls by com m ercial vessels (Figu re 3.4.2.3). Excep t 3 hau ls consid ered as non

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valid , 99 w ere u sable for assessm ent. It w as im p ossible to p rocess sep arately esti- m ates u sing only Thalassa hau ls or both as it w as d one last year becau se the fishing strategy has been followed all along the survey in order to profit of the best efficiency of each vessel. Taking into account the fact that pair trawlers are more efficient at surface than back traw lers, the com m ercial vessels carried ou t m ostly su rface hau ls w hen Thalassa fish p referably in the bottom layer. The d ecision on fishing w ere all taken from Thalassa in ord er to maximize the nu m ber of sam p les, in term of id entification and biological parameters as well.

A total of 19 690 fish were measured (including 3 897 anchovy and 4 375 sardine) and 1747 otoliths were collected for age determinations (908 anchovy and 839 sardine).

3 .4 .2 .2 Di st r i b u t i o n (an ch o vy an d o t h er s)

Accord ing to Thalassa catches (m ainly close to the bottom ) and com m ercial vessels one (mainly close to the surface), a distribution of species observed during the survey can be seen on Figure 3.4.2.3.

Anchovy w as observed along the coast from Bayonne (43° 40 N ) to Rochebonne (46°00 N ), m ostly m ixed w ith sard ine and som etim es w ith horse m ackerel in the sou th of the Girond e then often alone u ntil Rochebonne w here it w as m ixed w ith sp rat. On the p latform , anchovy w as qu ite om nip resent betw een 50m and 100m depth but always mixed with horse mackerel or sardine. Echo-traces were most of the tim e sep arated vertically as alread y d escribed by Massé (1996), horse m ackerel close to the bottom and anchovy as soft and sm all schools 15 to 25 m above. Anchovy w as totally absent in the area called "Fer à cheval" and very rare sou thern along the shelf break, except some rare small surface schools.

The sp atial extent of the low salinity is from the coast to the isobath 50 m ap p rox, w here as the p lu m e (salinity <34) m ay extent to the isobath 100 m . Su rface flu orescence w as m axim u m close to Belle-Ile and at the shelf break arou nd 46°N . There w as low flu orescence in the low haline coastal w aters, p robably becau se of the strong d ischarge. A coastal cu rrent oriented to the N orth w as evid enced by d ep loying bu oys, which is associated to the low salinities of the river discharges.

It can be also noticed that Tem p eratu re and salinity record ed d u ring PelGas w ere affected by w eather cond itions before and d u ring the su rvey. At the start of the su r- vey in the South, temperature were low (14-15°C) due to low heating and strong mixing before and during the first week of the survey. Then good weather resulted in sea su rface w arm ing and therefore the N orth of the Bay show s higher sea su rface tem- p eratu res (16-17°C) than the Sou thern p art. H igh river d ischarge gave low salinity p lu m es oriented to the north for Ad ou r, Girond e and Loire. The sp atial extent of the low salinity is from the coast to the isobath 50 m approx, where as the plume (salinity

<34) may extent to the isobath 100 m.

Anchovy eggs abu nd ance w as close to the average of the tim e series since 2000. Eggs w ere abu nd ant on Plateau d es Land es arou nd 44°N and arou nd the Girond e p lu m e.

N orth of Girond e, eggs w ere coastal only and in low qu antity. Both abu nd ance and sp atial d istribu tion d isp lay an average p attern. This year, som e eggs w ere fou nd on the south coast of Brittany but in a low quantity

Abou t top p red ators, 2559 seabird and cetacean sightings have been record ed d u ring the Pelgas 2008 su rvey. Tw enty-seven bird sp ecies and nine cetacean sp ecies have been identified.

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3 .4 .2 .3 St o ck est i m at e

It was not possible to process all the acoustic data for the time of WGANC. Neverthe- less, all the sou thern area w as p rocessed and anchovy w as rather absent in the northern one. Therefore it is p ossible to consid er that the sou thern coverage is su fficient to be representative of the anchovy biomass in May 2008.

As the p reviou s years, after echogram scru tiny, the global area has been sp lit into strata w here coherent com m u nities w ere observed (sp ecies associations) in ord er to minimize the variability due to the variable mixing of species (Figure 3.4.2.4.). Alloca- tion to sp ecies w as therefore d one u sing the stand ard m ethod (Massé,J, WD2001) and biom ass w ere estim ated for m ain p elagic sp ecies accord ing to aggregation categories and identification hauls (Table 3.4.2.1.).

The anchovy biom ass w as estim ated to 37 358 t w ith a coefficient of variation of 12.4% (the m ethod is d etailed in Petitgas et al., 2003) m eaning that the anchovy bio- m ass accord ing to acou stic d ata and p elagic hau ls shou ld be betw een 28 093 and 46 623t. Anchovy distribution is shown in Figure 3.4.2.5

An anchovy biomass estimate in tons and in number has been processed for each area at age grou p (table 3.4.2.2.), u sing length d istribu tions at each closest hau l and global age/length key. Length d istribu tion of anchovy is show n in Figu res 3.4.2.6 and 3.4.2.7.

The length and age d istribu tion as observed d u ring PELGAS08, show ed tw o d istinc- tive strata with considerable anchovy biomass: the south coastal area and the Gironde one (see Figu re 3.4.2.5). Estim ates have been calcu lated in nu m bers for each area and the resu lts are show n in table 3.4.2.3. It show s that 86 % of age 1 in 2008 w ere concentrated in Girond e area and that only big 2 and 3 years old w ere p resent in the sou thern area (Figures 3.4.2.8).

3 .4 .2 .4 Co n cl u si o n

The anchovy biom ass from the Pelgas08 su rvey has been estim ated at 37 000t. The nu m ber of 1 year old anchovy is at a m ed iu m level bu t still low com p are to good years and w as estim ated at 960 m illions fish. The global p op u lation observed in the Bay of Biscay w as com p osed of 47 % of age 1, 40 % of age 2 and 13 % of age 3+ in nu m bers. H alf of the biom ass w as in Girond e area and contained 87 % of the recru it- m ent (2007 year class). This fish w as very sm all com p are to 1 year old in the p ast years. The second half of the biom ass w as essentially big fish (2 and 3 years old ) and distributed along the coast in the southern area.

3 .4 .3 Hi st o r i cal ser i es DEPM & aco u st i c su r veys

Acou stic su rveys w ere carried ou t from 1989 to 1998 by IFREMER, covering the m ain anchovy area d istribu tion in the sou thern p art of Bay of Biscay. Sam p ling strategy and echo-sou nd ers w ere d ifferent of those u sed now ad ays, bu t w ere consid ered reliable for biom ass estim ation becau se of ap p rop riate calibration of system s and ad ap ted sam p ling strategy. A new series started in 2000 covering the w hole Bay of Biscay with a constant sampling strategy and simultaneous data collecting for ecosystem purposes.

Biom ass estim ates have been revised recently (ICES, 2007b) for the last series (2000 2008) u sing new tools for stratification of areas, system atic w ays of calcu lation and use of identification hauls through a common data base (BARACOUDA) and benefits

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from new incom ing inform ation. They are p resented together w ith DEPM estim ates in Figure 3.4.3.1.

Geograp hic d istribu tion m ap s are p resented in Figu res 3.4.3.3.and 3.4.3.2 Anchovy seems to be more concentrated in the southern area and more coastal nowadays.

It m u st be noticed that recent observations show ed that anchovy m ay have rap id local d isp lacem ent. The sm all fishes localized in the sou th of Girond e area at the beginning of the PELGAS08 su rvey (Figu re 3.4.2.4.) w ere localized again 10 d ays later d u ring the BIOMAN 08 su rvey (Figu re 3.4.1.1, Figu re 6 Santos w d , Annex 3) 20 nau tical m iles fu rther N orth. The sam e grou p w as localized again at the very end of PEL- GAS08, 10 days later, 15 nm southern and a little bit more offshore. This suggests this fish p erform s fast m ovem ents at a local scale w hich cannot be consid ered as real m i- gration, bu t m ore as resp onses to changes in local environm ental cond itions in ord er to rem ain in a su itable habitat. Ind eed , the river p lu m e as observed by satellite im- agery showed drastic changes between the beginning and the end of PELGAS survey.

This strengthens the id ea that a d irect assessm ent su rvey m u st be carried ou t in the shortest possible time window.

DEPM su rveys have been carried ou t since 1987 by AZTI-tecnalia, covering the sou theast of the Bay of Biscay, w hich corresp ond s to the m ain sp aw ning area and sp aw ning season for anchovy. Sm all changes havebeen d one in the sam p ling strategy and the m ethod ology all along the series being the final p op u lation estim ates comparable.

The d evelop m ent of the stock as it is seen in the tw o su rveys is show n in Figu res 3.4.3.1 and 3.4.3.4. The general trend is similar for both DEPM and acoustic based SSB estim ates (see also section 3.5.2 and 3.5.4, and a revision and com p arison of the series in ICES, 2007b). A shrinkage of the d istribu tion area d u ring the recent p eriod of low recru itm ent is evid ent in both su rveys. The fraction of age 2 fish has increased recently, w hich is how one w ou ld exp ect the effect of the closu re of the fishery to m ate- rialize in the survey results.

3 .4 .4 Ju ven i l es su r veys

3 .4 .4 .1 Back g r o u n d an d h i st o r y

N ow ad ays tw o acou stic su rveys are taken p lace on anchovy ju veniles in the Bay of Biscay in Autumn:

The JUVEN A series (acou stic su rveys for anchovy ju veniles) aim at esti- mating the abundance and spatial distribution of anchovy juveniles during early autumn in the Bay of Biscay. The series in conducted by AZTI (Spain) as resu lt of the d em and of the Basqu e and Sp anish fisheries m inisters for m onitoring of the anchovy p op u lation. The series began in 2003 and its fifth su rvey took p lace in au tu m n 2007 (Table 3.4.4.1) (Boyra et al., 2004, 2005a, 2005b, Boyra & Uriarte, 2005 and Boyra et al., 2007; see a review in ICES, 2007b). The long term objective of this su rvey-p roject is to p rovid e an estim ate of the strength of the anchovy recru itm ent entering the fishery the next year (as 1 year old ) so as to help on the p rovision of scientific advice to m anagers. In ad d ition, the sp atial d istribu tion of the ju venile p op u- lation, the grow th cond ition and the hyd rological characterization are stu d ied . The su rvey is p resented , review ed and coord inated w ithin WGACEGG (ICES, 2007b). Som e revisions and im p rovem ents w ere u nd er- taken since 2005 in the estim ation p roced u res and su rveying coverage, fol-

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low ing su ggestions and share exp ertise in STECF, WGH MSA and WGACEGG. Recom m end ations from WGACEGG have been p rogressively im p lem ented in the JUVEN A su rveys, and a revision of the w hole tim e series, w ith the excep tion of 2006 w as p resented to the 2007 WGACEGG m eeting (ICES, 2007b). Resu lts of the 2006 su rvey w ere revised in the in- terim tim e betw een WGACEGG and WGAN C and are p resented in this year WGANC meeting.

The PELACUS 2007 cru ise (au tu m n PELACUS), inclu d ed in the IEO p roject ECOPEL (p elagic fish com m u nity and ecosystem ), aim s to stu d y the abu nd ance and d istribu tion of anchovy ju veniles, as w ell as the recru it- m ent p rocess. The cru ise has been carried ou t in 2006 and 2007 on board RV Thalassa betw een Sep tem ber and October in the sou thern Bay of Bis- cay. In 2007 the PELACUS 1007 su rvey w as p lanned and carried ou t in coord ination w ith the Ju vena 07 cru ise, cond u cted in the sam e area approxim ately at the sam e p eriod and w ith sim ilar objectives. The coord i- nation involved : 1) an agreed sam p ling strategy, d iscu ssed in WGACEGG 2006 (ICES, 2007); 2) p erm anent com m u nication and transfer of inform a- tion betw een the research vessels involved in the resp ective cru ises d u ring the campaigns; and 3) joint re analysis of the acou stic and fishing hau l d ata acqu ired d u ring the cru ises (Workshop on ju venile acou stic cru ises carried out in 2007; 12 14 November, held in the Centro Oceanográfico de Gijón.

3 .4 .4 .2 Su r veys i n 2 0 0 7

3 .4 .4 .2 .1 JUVENA Ser i es an d t h e su r vey i n 2 0 0 7 .

The JUVEN A series, u p to the last su rvey in au tu m n 2007, has been d iscu ssed and rep orted in WGACEGGs (ICES, 2007b). A final revision of the 2006 estim ate w as not available at the tim e of last WGACEGG m eeting, bu t has been m ad e available to the WGANC 2008 meeting (Boyra et al., WD2008), in order to complete the revision of the JUVEN A series and com p are the ind ex of ju venile abu nd ance w ith the one year old estimates provided by ICES anchovy assessment. The revision of the 2006 survey was requ ired to overcom e the bad fu nctioning of one the 38 KH z transd u cers m ou nted in one of the tw o vessels p articip ants in the su rvey, as rep orted to WGACEGG (ICES, 2007b). Such a revision was possible thanks to several com mon tracks done in parallel betw een the tw o vessels for inter-calibration p u rp oses (see d etailed inter-calibration results in the WD attached to this report).

In 2007, as hap p ened in year 2006, the su rvey took p lace onboard tw o vessels equ ip p ed w ith scientific acou stic equ ip m ents and w ith tw o d ifferent fishing gears:

the p u rse seiner Gu re Aita Joxe (GAJ) and the p elagic traw ler Em m a Bard an (EB).

The su rvey took p lace d u ring 28 d ays in Sep tem ber, su rveying 4100 n.m i., along the continental shelf and shelf break ofthe Bay of Biscay. The su rvey grid p rovid ed an effective sam p ling d istance of 1500 n.m i. and a coverage of abou t 22000 n.m i.2, from the 5º W in the Cantabrian area u p to 47º 20 N at the French coast (Figu re 3.4.4.1).

Seventy hau ls w ere d one d u ring the su rvey to id entify the sp ecies d etected by the acoustic equipment, 37 of which resulted positive of anchovy.

The biom ass of ju veniles estim ated for this 2007 is 13000 tones, a low valu e in com- p arison w ith the p reviou s valu es of the tem p oral series of JUVEN A, only higher than the 2004 estimate (Table 3.4.4.2 where the JUVENA series is also included). This value is abou t one ord er of m agnitu d e less than the higher estim ates of the series (the ones

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corresponding to 2003 and 2005) and suggests that a high recruitment was unlikely to happen in 2008. The spring surveys in 2008 confirmed this.

3 .4 .4 .2 .2 PELACUS 2 0 0 7 .

The au tu m n PELACUS su rvey has been carried ou t for the years 2006-2007 (ICES, 2007b). Resu lts of this su rvey have so far been u sed to obtain inform ation on ju venile anchovy d istribu tion and habitat, environm ental cond itions in the Bay of Biscay p e- lagic ecosystem in au tu m n and to stu d y the anchovy recru itm ent p rocess in the Bay of Biscay and cross-valid ate the resu lts of the JUVEN A series. Both the JUVEN A and the PELACUS su rveys p rovid e com p lem entary inform ation on the ju venile d istribution and habitat, and their com p arison have so far allow ed to im p rove the su rvey design required to estimate juvenile abundance (ICES, 2007b).

Resu lts of the PELACUS 1007 have been p resented in WGACEGG (ICES, 2007b) and are su m m arised in Figu res 3.4.4.3 and 3.4.4.4 and Table 3.4.4.4. Anchovy w as local- ised in tw o zones: N orth of cap e Breton Les Land es (CP LL) and in the zone off La Girond e (G) estu ary. In CP LL, anchovy w as d etected close to the coast (<50 m isobath), p resenting a m od al size betw een 10 13 cm . In the G zone, anchovy w as d e- tected in the inner shelf, from the coast u p to the 100 m isobath, show ing a clear coastal offshore grad ient in term s of m od al size (and age), w hich ranged from 11 to 16 cm of m od al size (Figu re 3.4.4.4). Total anchovy biom ass w as estim ated as 16900 tn, of which 3039 tn corresponded to juveniles (Table 3.4.4.2.).

3 .4 .4 .2 .3 Bal an ce o f j u ven i l e i n d ex ser i es; cu r r en t st at u s an d p o t en t i al u se f o r m an ag e- m en t .

As pointed out by WGACEGGs report (ICES, 2007b), the Bay of Biscay juvenile Index of anchovy has su ffered large and thou ghtfu l review s in the p ast years. The p ossibility of com p aring the ju venile tim e series (JUVEN A) w ith another su rvey w ith sim ilar objectives carried ou t sim u ltaneou sly (PELACUS) has allow ed cross valid ation of the su rveys, and has yield an im p rovem ent of the m ethod s requ ired to obtain a stable and u nbiased ju venile abu nd ance ind ex. Both the JUVEN A and PELACUS cru ises have p rovid ed d ifferent resu lts in the p ast tw o years. N evertheless, d u ring p ast in- terim w orkshop s and the last WGACEGGs m eeting, the m ain sou rces of d ifferences betw een the su rveys have been id entified and are m ainly allocated to d ifferences in coverage as w ell as to sm all m ethod ological p roblem s. Recom m end ations on how to im p rove the su rvey coverage have been p rod u ced , and the m ain m ethod ological problems identified have been overcome.

The series of JUVENA acoustic estimates of anchovy juvenile abundance in the Bay of Biscay is show n in Table 3.4.4.3. Althou gh the su rvey have su ffered som e m od ifica- tions in m ethod ology and coverage,, both the WGMH SA and WGACEGGs con- clu d ed that the resu lt of the ju veniles su rvey can be u sed as an ind ex of the evolu tion of ju venile abu nd ance (ICES, 2007a and 2007b).. The qu estion rem aining is the valid- ity of the obtained ju venile abu nd ance ind ex as an ind ex of recru itm ent strength (ICES, 2007b).

Figure 3.4.4.3 compares the times series of the JUVENA anchovy juveniles abundance ind ex w ith the estim ates of biom ass at age 1 (m ed ian valu es) p rod u ced by Bayesian assessm ent inclu d ed in this rep ort. The JUVEN A ind ex show s tw o m inim a at 2004 and 2007, w hich coincid es w ith the low er recru itm ent estim ated in 2005 and 2008.

H ow ever, the correlation betw een the w hole JUVEN A series and the assessm ent- based estim ates of recru itm ent are not statistically significant at 5% significance level

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(R=0.76, P(R)=0.134). The lack of statistical significance in this analysis m ay be m ainly due to the few observations available and to the characteristics of the period analysed (lackof contrast in the recru itm ent levels). The series of recru itm ent estim ates on the period covered by the JUVENA surveys are of similar levels and among the lowest of all the tim e series since 1987 (see Section 3.7.3.1). Therefore taking into accou nt the u sual variability of both the acoustic index and the recruitment estimates and the low number of estimates available, the lack of statistical significance is not surprising.

The WG d iscu ssed the above resu lts in the p ersp ective of its p erform ance and p otential use for management, making the following concluding remarks:

Using the JUVEN A ju venile ind ex to estim ate recru itm ent at age 1 for the following year appears to be promising, as. so far some general parallelism of the trend s in the series has been seen. H ow ever, the lack of contrast in the estim ated recru itm ents for this short p eriod p revents a su fficient statistical analysis of the perform ance of the index.

The ability of the JUVEN A ind ex to p red ict a large recru itm ent has not been confirmed yet. A high juvenile abundance observation should be confirm ed by the follow ing sp ring su rveys. Until the p erform ance of this in- d ex has been valid ated , a high ju venile abu nd ance observation shou ld not be used as a basis for a decision to re-open the fishery. The WG encourages the continu ity of the series both for the qu ality of the inform ation achieved and for the p otential u se in assessm ent and m anagem ent ad vice, once its p erform ance is evalu ated , Coord ination w ith PELACUS10 su rvey at ICES WGACEGG is also encou raged , to ensu re cross-valid ation of the estim ates and m axim ize the am ou nt of inform ation gathered on ju venile anchovy habitat.

In su m m ary, the resu lts from the five years of the JUVEN A abu nd ance ind ices of anchovy juveniles are encouraging, but the short life of this series and the lack of contrast p revents yet a p rop er evalu ation of its p erform ance as a p red ictor of the age 1 entering the popu lation and the fishery the next year.

3 .5 St at e o f t h e st o ck 3 .5 .1 Met h o d

The assessm ent for the Bay of Biscay anchovy p op u lation is based on a tw o-stage biomass-based m od el, w here the p op u lation d ynam ics are d escribed in term s of bio- m ass w ith tw o d istinct age grou p s, recru its or fish aged 1 year, and fish that are 2 or more years old. The biomass decreases exponentially on time by a factor g accounting for intrinsic rates of grow th (G) and natu ral m ortality (M) w hich are assu m ed year- and age-invariant.

Tw o p eriod s are d istingu ished w ithin each year. The first begins on 1 Janu ary, w hen it is assu m ed that age increm enting occu rs and age 1 recru its enter the exp loitable population, and ru ns to the d ate w hen the m onitoring research su rveys (acou stics and DEPM) take p lace. The second p eriod covers the rest of the year (from 15th May to 31st Decem ber). Catch is assu m ed to be taken instantaneou sly w ithin each of these p eriods.

The observation equ ations consist on log-norm ally d istribu ted sp aw ning stock bio- m ass from the acou stics and DEPM su rveys, w here the biom ass observed is p rop or- tional to the tru e p op u lation biom ass by the catchability coefficient of each of the

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su rveys, and the beta d istribu ted age 1 biom ass p rop ortion from the acou stics and DEPM su rveys, w ith m ean given by the tru e age 1 biom ass p rop ortion in the p op u lation.

The m od el u nknow ns are the initial p op u lation biom ass (in 1987), the recru itm ent each year, the catchability of the su rveys and the variance related p aram eters of the observation equ ations. The m od el can be cast into a Bayesian state-sp ace m od el fram ew ork w here inference on the u nknow ns is d one u sing Markov Chain Monte Carlo (MCMC).

A first version of this m od el w as u sed for the benchm ark assessm ent in WGMH SA in 2005 (ICES 2005) and it w as ad op ted by ACFM as the official assessm ent for the stock in 2006 (ICES 2006). Last year, the assessment presented in the WGMHSA (ICES 2007) was just an update of the benchmark assessment. A modified version of the two-stage biomass-based m od el w as p u blished at the beginning of this year (Ibaibarriaga et. al 2008). The differences between both models consist on:

a ) parameterization of the recru itm ent p rocess. In Ibaibarriaga et. al

(2008) recruitment is modelled as a log-normal process, so that the parameters to estim ate are the m ean recru itm ent (in log scale) and its p recision (inverse of variance) together w ith the yearly d eviations of the recru itm ent w ith resp ect to the m ean. Alternatively, in WGMH SA, yearly recru itm ents are estimated.

b ) p rocess errors. The m od el u sed in WGMH SA inclu d es log norm ally d istribu ted p rocess errors into the d ynam ics of the age 1 p op u lation d u ring the first p eriod (from the beginning of the year u ntil su rveys take p lace).

This im p lies 2 new u nknow n states to be estim ated for each of the years.

These process errors are not included into Ibaibarriaga et. al (2008).

c ) estim ation of g. The m od el in Ibaibarriaga et. al(2008) allow s to estim ate the parameter g accounting for growth and natural mortality, which is not possible in the model used in WGMHSA.

d ) the u nknow ns and the p rior d istribu tions. The d ifferences into the m od el specifications exp lained above lead to d ifferent p aram eters to estim ate. In ad d ition, som e of the p rior d istribu tions and their hyp er-p aram eters w ere d ifferent. For instance, the d istribu tion of the initial biom ass w hich is norm ally d istribu ted in WGMH SA, is log-norm al in Ibaibarriaga et. al (2008) and the hyp er-p aram eters of the gam m a d istribu tions of the p recision of the biom ass from the su rveys are chosen to have m ean 10 in WGMH SA, w hereas in Ibaibarriaga et. al(2008) are selected to have m e- dian 10.

Fu rther d etails of each of the m od els can be fou nd in the WGMH SA rep ort (ICES 2007) and in Ibaibarriaga et. al (2008) respectively.

The w orking grou p consid ered the p u blished version of the m od el m ore ad equ ate than the one p reviou sly u sed in ICES. On the one hand , the p aram eterization of the recru itm ent p rocess is m ore general and cou ld allow the introd u ction of d ifferent fu nctional form s if w anted , and on the other hand , the p ossibility of estim ating g is d esirable, althou gh there is no enou gh inform ation on the su rveys them selves by now to overcom e the ind eterm inacy of the resu lts. In ad d ition, since little gain w as obtained by inclu d ing p rocess errors into the age 1 biom ass d u ring the first p eriod , it w as consid ered m ore ad equ ate to assu m e d eterm inistic exp onentially d ecreasing biomass p op u lation d ynam ics. Therefore, the w orking grou p d ecid ed to p resent an

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u p d ate assessm ent of the Bayesian tw o-stage biom ass-based m od el (BBM) based on the published version.

The high p osterior correlations betw een the su rveys catchability p aram eters,annu al recru itm ents, total initial biom ass, the rate of biom ass d ecrease (if estim ated , as in Ibaibarriaga et. al 2008) and the age 1 biom ass p rocess errors in the first p eriod (if estim ated as in WGMH SA 2007) illu strate the ind eterm inacy of the p roblem . Infer- ence on recru itm ent levels w ill be d ep end ent on the assu m p tions m ad e on the su r- veys catchabilities, on the rate of biom ass d ecrease and on the p rior d istribu tions for recru itm ents. So, w ithou t any ad d itional inform ation, given the near im p ossibility of d eterm ining the absolu te level of the p op u lation, the estim ated recru itm ent valu es shou ld be consid ered as relative rather than as absolu te valu es. For the tim e being, and for consistency w ith the p ast p ractices, the u p d ate assessm ent consid ers the DEPM as absolu te and g fixed at 0.68, w hich m eans that the assessm ent p resented is scaled w ith resp ect to these assu m p tions. Figu re 3.5.1.1 show s the com p arison of the p osterior d istribu tion of sp aw ning stock biom ass from WGMH SA (ICES 2006) and from Ibaibarriaga et. al (2008), w hen the DEPM catchability p aram eter is taken as 1, g is fixed at 0.68 and the first set of p riors of each m od el is u sed . Und er these assu m p- tions the resu lting p osterior SSB d istribu tions are alm ost the sam e, ensu ring the consistency with past assessments.

3 .5 .2 Dat a an d m o d el ex p l o r at i o n

The inp u t d ata entering into the assessm ent of the anchovy stock consist on total biom ass and biom ass at age one as estim ated by the research su rveys cond u cted in spring, namely, DEPM and acoustic surveys (see sections 3.4.1 and 3.4.2) and on catch inform ation from the d ifferent fleets exp loiting the stock that are d escribed in section 3.2. In ad d ition, the age com p osition and the m ean w eights at age d erived from the biological sampling of the catches are also used.

The historical series of sp aw ning stock biom ass (SSB) from the DEPM and acou stic surveys are compared in detail in section 3.4.3. The acoustic estimates since 2000 were revised and p resented to WGACEGG (ICES 2007b). Excep t in som e of the years, like 1994, 1998 or 2004, in w hich there are som e d iscrep ancies, the trend s in biom ass from both su rveys are sim ilar. In p articu lar, in the last years a p arallel trend bu t w ith larger biom ass estim ates from the acou stic su rveys is ap p arent. The agreem ent betw een both su rveys is higher w hen estim ating the age stru ctu re of the p op u lation. Figu re 3.5.2.1 com p ares the historical series of the p rop ortion of age 1 biom ass of DEPM and acoustic surveys.

Figu re 3.5.2.2 show s the historical series of age 1 and total catches in the first p eriod (1st Janu ary-15th May) and of the total catches in the second p eriod (15th May-31st Decem ber), w hich are u sed in BBM. Catches in the second p eriod are larger than in the first p eriod and m ost of the catches in the first p eriod corresp ond to age 1. In the last years d u e to the low level of the p op u lation and variou s fishery closu res, the catches have been very low being zero in the last year.

In p reviou s years d ifferent m od el op tions w ere exp lored regard ing the catchability assump tions from the su rveys and d ifferent set of p riors fro the BBM. H ow ever, this year, given the u p d ate natu re of the assessm ent and the red u ced tim e available for the m eeting, no alternative op tions have been exp lored and only the assessm ent u p- date is presented.