Marine Policy 36 (2012) 235–240

Contents lists available at ScienceDirect

Marine Policy

0308-59

doi:10.1

n Corr

E-m

journal homepage: www.elsevier.com/locate/marpol

Why is the Eastern Baltic cod recovering?

Margit Eero n, Friedrich W. Koster, Morten Vinther

Technical University of Denmark, National Institute of Aquatic Resources, Charlottenlund Castle, 2920 Charlottenlund, Denmark

a r t i c l e i n f o

Article history:

Received 1 November 2010

Received in revised form

16 March 2011

Accepted 23 May 2011

Keywords:

Eastern Baltic cod

Recovery

Management

Compliance

Recruitment

7X/$ - see front matter & 2011 Elsevier Ltd. A

016/j.marpol.2011.05.010

esponding author. Tel.: þ45 3588 3318; fax:

ail address: mee@aqua.dtu.dk (M. Eero).

a b s t r a c t

The Eastern Baltic cod stock was until recently below safe biological limits and suffered from high

fishing pressure. In most recent years, fishing mortality substantially declined and spawner biomass

more than tripled. Similar developments have not been observed for any other depleted cod stock in the

North Atlantic during the last few decades. This paper investigates relative impacts of changes in

different ecological and management-related drivers, which could have contributed to the rapid

recovery of the Eastern Baltic cod. The results show that the success to reduce fishing mortality below

management target in 2008 was due to a combination of increased recruitment and improved

compliance with TAC. The reversal of the negative trend in biomass and rebuilding of the stock to

the present level were largely driven by increased recruitment. Harvest control rules of the multi-

annual management plan for setting TACs currently maintain the fishing mortality at a low level, which

allows the stock to accumulate biomass and further accelerate its recovery. Relatively strong incoming

year-classes and recently better control over removals distinguish the Eastern Baltic cod from other

depleted European cod stocks, which have not shown similar positive trends in recent years. Sound

management measures and compliance to those as well as favourable biological conditions are required

for a successful stock recovery.

& 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Many of the world’s fisheries and fish stocks have declined inrecent decades, at least partly due to overfishing. Rebuildingdepleted fish populations to the levels where they can producemaximum sustainable yields is a global imperative emerging fromthe World Summit on Sustainable Development in Johannesburgin 2002, and this target has been given a deadline of 2015 [1]. TheEuropean Commission recently recognised that 88% of Europeanfish stocks are fished beyond the level corresponding to max-imum sustainable yield and 30% of these stocks are outside safebiological limits [2]. Recovery plans have been implemented for anumber of depleted stocks in different parts of the world includ-ing Europe, but with variable success [3–5]. Each example wherea stock recovery has taken place can therefore provide somevaluable insights to what is required to reverse declining trends infish populations and enable them to recover to sustainable levels.

Eastern Baltic cod provides an example of one of the mostrapid recoveries of a heavily exploited demersal fish stockobserved in North Atlantic waters in recent decades. In 2005,spawner biomass (SSB) of the Eastern Baltic cod was at the lowestlevel observed in the time-series since the 1960s. Since then, thespawning stock has been increasing from less than 70 000 t in

ll rights reserved.

þ45 3588 3333.

2005 to 220 000 t in 2009 and is predicted to be close to 300 000 tin 2010 (Fig. 1) [6]. The stock can therefore be considered asabove safe biological limits according to the precautionary bio-mass reference points that have previously been used for thisstock (Bpa¼240 000 t) [7]. Fishing mortality (F) has declined fromabove 1.0 in 2004 to 0.25 in 2008 and is currently at the lowestlevel among all European cod stocks [6,8–11]. The reduction infishing mortality and stock recovery of the Eastern Baltic codduring a short period of time is receiving increasing attention atboth scientific and policy level. Hence, it is important to under-stand the main drivers responsible for these positive changes,which may also give some indication why similar developmentsare not seen for other depleted cod stocks in the Atlantic.

Several changes in the Eastern Baltic cod biological para-meters, fisheries and management have occurred in recent years,all of which could have potentially had an influence on thedevelopment of the stock. The purpose of this paper is todisentangle these effects and quantify their relative importancefor the observed recovery of the Eastern Baltic cod.

2. Recent changes in the Eastern Baltic cod management,fisheries and recruitment

The average total catch of the Eastern Baltic cod in 2002–2006was 70 000 t. In 2007 and 2008, the catch declined to 55 000 and46 000 t, respectively (Fig. 2) [6]. Total allowable catch (TAC) was

1980

0

Thou

sand

tons

1970

Fish

ing

mor

talit

y

0.0

SSBF

1990 2000 2010

0.5

1.0

1.5

100

300

500

700

Fig. 1. Spawning stock biomass (SSB) and fishing mortality (F) of the Eastern Baltic

cod (data from [6]).

0

10

20

30

40

50

60

70

80

2002

Thou

sand

tons

TAC Illegal landingsDiscard Total catch

2003 2004 2005 2006 2007 2008 2009

Fig. 2. Catch of the Eastern Baltic cod. Total catch in 2004–2009 is broken down to

landings corresponding to TAC (before 2004, TAC was set combined for Eastern

and Western Baltic cod), illegal landings and discards (data from [6]).

1970

0

Mill

ions

R re

lativ

e to

SS

B

0.5

RR/SSB

200

400

600

800

1980 1990 2000 2010

1.0

1.5

2.0

2.5

Fig. 3. Absolute and relative recruitment (R) of the Eastern Baltic cod. Relative

recruitment is represented by the numbers of recruits per unit of spawning stock

biomass (R/SSB) (data from [6]).

M. Eero et al. / Marine Policy 36 (2012) 235–240236

at the same time only reduced by 5000 t in 2007 compared to2006 (from 49 000 to 45 000 t) and further by 3000 t in 2008. Thereduction in total catch was mainly due to reduced illegal land-ings. In 2004–2006, ICES estimated total landings to be about 30%higher than the TAC, while the landings in 2008 and 2009 used inthe assessments were in line with the TAC [6]. Catches increasedto 52 000 t, i.e. by around 15%, in 2009 resulting from increasedTAC according to the multi-annual management plan.

The multi-annual management plan (MP) aiming at recoveryand sustainable exploitation of Baltic cod stocks was agreed uponin 2007 and fully implemented in 2008 [12]. The plan contains atarget fishing mortality at 0.3 for the Eastern Baltic cod to beachieved by applying certain harvest control rules for setting TAC,fishing effort restrictions and ensuring compliance with the rules.The harvest control rules of the plan imply a gradual reduction offishing mortality (F) by 10% per year until the target of 0.3 isreached, and a 715% constraint for changes in TAC from one yearto the next, except when the fishing mortality in the year ofapplication of the TAC would be above 0.6. The harvest controlrules of the plan were for the first time formally applied in 2009,which resulted in a 15% increase in TAC, even though the resultingfishing mortality stayed below the management target.

In addition to catch regulations, fishing effort in terms of thenumber of fishing days allowed per vessel in cod fisheries wasreduced by 35% during the period 2006–2009, in relation to themanagement plan. Also, various new technical regulations onfishing gears have been implemented during the 2000s, andclosed areas and seasons have been in place. But as the focus ofthis paper is on the effects of changes in realized catch vs. changesin biological productivity, the effects of restrictions of fishingeffort and other parameters likely influencing the catch were notanalysed.

Recruitment (numbers of cod at age 2) in each year during2005–2009 has been 20–50% higher than the average in 2002–2004 [6]. Relative recruitment, i.e. number of recruits producedper unit of spawner biomass, has, in recent years, been among thehighest in the entire time-series (Fig. 3).

Relative fishing mortality, i.e. selection at age, has changed inrecent years compared to the selection pattern observed in earlierperiod. Traditionally selection has increased with age, levelling offat the age of around 5. In 2006–2009, selection was highest on4–5 years old cod, declining for older age groups [6].

3. Analyses to quantify the effects of changes in differentfactors on F and SSB

The recent decline in F and an increase in SSB of the Eastern Balticcod were considered to have been influenced by the above-describedchanges in (i) total catch, (ii) recruitment and (iii) selection at age.Additionally, potential effects of inter-annual variations in (iv) meanweight at age were considered, though mean weights of different agegroups did not show consistent trends during the analysed period. Ina second step, changes in total catch were broken down to the effectsof (v) reduction in TAC and (vi) improved compliance with TAC.Finally, the effect of (vii) the harvest control rule of the MP for settingthe 2009 TAC was addressed. In the ICES advice for 2009, all scenariosresulting in fishing mortality at, or below, 0.6 (previously usedprecautionary F reference point) were considered consistent withthe precautionary approach. If the precautionary approach had beenfollowed instead of the MP, the TAC for 2009 would have been setsubstantially higher and very likely also realized, which would haveresulted in substantially higher catches in 2009 than was the caseunder the MP.

Within the analyses, simulations were conducted to determinehow F (average of age groups 4–7, which is used as a referencefishing mortality for this stock) and SSB would have developedduring 2005–2010 if the observed changes in factors (i–vii) wouldnot have taken place. The term ‘‘observed’’ in this context refers tothe values, which have been used as input to the stock assessmentor are outputs of it, not considering uncertainties of these data orof the assessment. The contribution of each factor (i–vii) to theobserved decline in F and increase in SSB was investigatedseparately, ‘‘turning off’’ the observed changes in a correspondingvariable, while keeping the rest as observed in each particular year.

The simulations used the observed stock numbers in 2004 as astarting point. Stock numbers were subsequently projected for-ward with different input values (i–vii) using the standard stocknumbers and catch equations, which form the basis for fish stockassessment [13]:

Ntþ1;j ¼Nt;je�zt;j

M. Eero et al. / Marine Policy 36 (2012) 235–240 237

where N is the number of individuals of age j and year t and z isthe total mortality of age j (due to age-specific exploitation, Fj, andnatural mortality, Mj; z¼FþM).

The numbers of fish removed by fishing are represented by

Ct;j ¼Ft;j

Ft;jþMt;j

� �Nð1�e�zt;j tÞ

where C is the catch in numbers of fish at age j and year t [13].To simulate a situation without an observed recent change in

one of the factors (i–vii), the following values were applied forcorresponding variables:

i)

Fig. 4proje

age (

total catch (in weight) in 2007–2009 was set to the averagelevel observed in 2002–2006 (68 000 t);

ii)

recruitment (age 2) for each year in 2005–2009 was set to theaverage level observed in 2000–2004 (130 millions);

iii)

selection pattern (relative F at age) in 2006–2009 was set tothe average observed in 2003–2005;

iv)

weight at age, both in the catch and in the stock in 2005–2009,was set to the average observed in 2002–2004;

v)

TAC of 2006 (49 000 t) was applied for 2007–2009, assumingobserved annual proportions of illegal landings and discards;

vi)

the proportion of illegal landings in 2007–2009 was set to theaverage level estimated for 2004–2006 (27%); TAC andproportion of discards for each year were applied as observedand

vii)

catch in 2009 was set to correspond to fishing mortality at 0.6(previously used precautionary reference point).

In order to demonstrate the combined influence of changes inmainly naturally driven processes in comparison with the effectof catch regulations, an additional simulation was conductedwhere recruitment, weight at age and selection (ii–iv) weresimultaneously set to the values specified above, while keepingthe total catch as observed in each individual year.

Fig. 5. Effects of changes in different forcing factors on observed decline in fishing

mortality (F) and increase in spawning stock biomass (SSB). The bars show the

proportions how much the F would have been higher and SSB lower if the

observed changes either in catch (from 2007), recruitment (from 2005), selection

(from 2006) or weight at age (from 2005) would not have taken place. The

proportions are calculated as 1�SSBsim� SSBobs�1 and 1�Fobs� Fsim

�1 for SSB and F,

respectively, where sim refers to the simulated scenario without a change in

particular forcing factor and obs refers to the values from the latest stock

assessment [6].

4. Results

Results from simulations show that observed changes in totalcatch, recruitment and selection at age, as well as variations inmean weight at age, all contributed to the recent increase inspawner biomass (SSB) and/or the decline in fishing mortality (F)of the Eastern Baltic cod. All simulations, applying values fromearlier years for these variables, resulted in higher F and/or lower

2000

0.2

Fish

ing

mor

talit

y

BaselineCatchSelectionRecruitmentWeight0.4

0.6

0.8

1.0

1.2

1.4

2002 2004 2006 2008 2010

. Fishing mortality (F; panel A) and spawning stock biomass (SSB; panel B) from sc

cted developments in SSB and F (average of ages 4–7), if the observed changes eithe

from 2005) would not have taken place. Baseline refers to F and SSB from the lat

SSB for most of the years during 2005–2010 than estimated fromthe latest stock assessment (Fig. 4A and B). Especially the declinein F since 2006 was due to a combination of simultaneouschanges in different variables. In contrast, the recovery of SSB tosafe biological limits appears to be mainly driven by one singlefactor, i.e. improved recruitment success (Fig. 4B). If the recruit-ment had remained at the 2000–2004 level, this would haveresulted in an SSB at around 155 000 t in 2010, which is only halfof the level estimated from the most recent assessment.

Changes in different factors contributed to the development inF and SSB in varying proportions in different years (Fig. 5). Thecumulative effect of each factor over the years is represented byF and SSB estimates for the latest year, i.e. 2009 for F and 2010for SSB.

2000

100

Thou

sand

tons

BaselineCatchSelectionRecruitmentWeight

150

200

250

300

2002 2004 2006 2008 2010

enarios without recent changes in different forcing factors. The scenarios represent

r in catch (from 2007), recruitment (from 2005), selection (from 2006) or weight at

est stock assessment [6].

M. Eero et al. / Marine Policy 36 (2012) 235–240238

Increased recruitment and reduced catch were the mainfactors, which equally contributed to the decline in F to thepresent low level, whereas the effect of recruitment continuouslyincreased with years. If the observed changes in either recruit-ment or catch had not taken place, F in 2009 would in either casehave been about 40% higher than estimated from the latest stockassessment (Fig. 5). If the selection pattern would not havechanged towards higher selection of younger ages, referencefishing mortality (average of ages 4–7) in 2009 would have beenabout 15% higher than that is currently estimated from theassessment. Observed variability in mean weight at age in thecatch reduced the F by around 15% in 2005–2006, but had less oralmost no influence on F in later years (Fig. 5). The increasingeffect of recruitment with years is particularly apparent withrespect to SSB. Recruitment has clearly been the main factorresponsible for a continuous increase in SSB during 2006–2010(Fig. 5). The increased recruitment had twice as much influence ofthe SSB in 2010 compared to reduced catch, while variability inweight at age and selection had only minor effects on SSB insome years.

Assuming that the observed changes in recruitment, weight atage and selection at age are due to natural variability rather thanmanagement, natural variations had a similar influence onachieving the observed reduction in F to below the managementtarget in 2008, than changes in total catch (Fig. 6). Among the twocomponents of total catch, i.e. TAC and illegal landings, theimproved compliance with TAC had almost twice as muchinfluence on achieving the reduction in F than the reduction inTAC itself (Fig. 6). Further, the reduction in TAC in 2007–2008 hadalmost no influence on fishing mortality for 2009. In contrast,limiting the increase in TAC to only 15% in 2009, according to themanagement plan, largely determined the level of fishing mor-tality in 2009. Under the previous precautionary approach, fishingmortality in 2009 could, in principal, have increased up to 0.6,which is higher than it would have been with previous levels of

F in 2008SSB in 2009

46%8%

15%

56%36%

20%

F in 2009SSB in 2010

49%

6%

19%

23% 50%

38%

61%

3%

Unmanaged processesTAC reductionCompliance with TACTAC limit

Fig. 6. Relative contributions of changes in TAC, compliance with TAC and

unmanaged processes (recruitment, weight at age and selection) to the recovery

of the Eastern Baltic cod. The numbers show the percentage how much the SSB in

2009 and 2010 would be lower and F in 2008 and 2009 higher than estimated

from the latest assessment [6] if the observed changes in respective

factor(s) would not have taken place. TAC limit represents the effect of harvest

control rule of the multi-annual management plan for setting the TAC for 2009.

illegal landings or recruitment. Fishing mortality at 0.6 in 2009would have resulted in a 23% lower SSB in 2010 than currentlyestimated.

5. Discussion

The objective of the multi-annual management plan for Balticcod stocks is to ensure that the stocks can be exploited undersustainable economic, environmental and social conditions [12].Achieving this objective for the Eastern Baltic cod required,amongst others, rebuilding the stock to its full reproductivecapacity. This goal can be considered to have been reachedalready in 2009 when the spawning stock biomass (SSB)increased to above 240 000 t, i.e. the level that has previouslybeen used as the precautionary biomass reference point for theEastern Baltic cod [7] below which the stock has been classified asbeing in risk of suffering from reduced reproductive capacity.Fishing mortality (F) corresponding to the management target(0.3) was already reached in 2008, i.e. even before the harvestcontrol rules of the plan were fully implemented. The estimates ofthe stock status, especially for the terminal year, are associatedwith uncertainties [14], which is generally characteristic foroutputs from stock assessment models. This is, however, notexpected to invalidate the trend in strongly declining F andincreasing SSB.

A large part of the achieved reduction in F was due toelimination of illegal landings (Fig. 2). Fisheries control has beensubstantially intensified in recent years to diminish illegal codlandings in the Baltic Sea (e.g. [15–18]). The catches of the EasternBaltic cod have been uncertain throughout most of the 2000s andthe amounts of illegal landings used in stock assessments arebased on largely unofficial information available to the ICESAssessment Working Group [6]. Consequently, the magnitude oftotal catch and its inter-annual change are associated withrelatively large uncertainties. However, a real reduction in codcatches is believed to have taken place in recent years as a resultof an intensified control [6]. This confirms that regardless of thestrength of management measures and regulations, these are onlyeffective when enforced and complied with [19]. The need toensure compliance with the management measures also forms acentral part of the multi-annual management plan for Baltic codstocks [12].

Reduction in fishing effort likely has contributed to reducedcatches as well. The number of days at sea allowed when fishingwith a mesh size equal to, or greater, than 90 mm was annuallyreduced by 10–20% during 2007–2009, resulting in 35% lowernumber of days allowed in 2009 compared to 2006. A preliminaryanalysis [20] estimated the effort in terms of kilowatt-days to beabout 40% lower in 2007–2008 compared to 2005–2006.

The results of the analyses conducted in this paper suggestthat the observed reduction in catch alone would have beensufficient to achieve a substantial reduction in F, though thecurrent level would still be above the management target of 0.3.The SSB would, however, not yet have recovered to the previouslyused precautionary reference level (Fig. 4). A relatively large catchreduction in 2007 compared to 2006, in combination with astronger year-class 2003 dominating in fisheries, implied that asubstantial reduction in fishing mortality was achieved withinone year (2007). The subsequent recovery of the stock supportsthe observations from other areas that most successful rebuildingprogrammes have incorporated substantial reductions in fishingmortality at the onset instead of relying on small gradual reduc-tions over time [21].

The performance of multi-annual management plan for Balticcod stocks has been evaluated by stochastic simulations under

1.0

0.5

0.0

-0.5

-1.0

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

1.0Recruitment

Mortality

SSB

Pro

porti

on o

f cha

nge

Pro

porti

on o

f cha

nge

M. Eero et al. / Marine Policy 36 (2012) 235–240 239

different sources of uncertainties and stock–recruitment relation-ships [22]. This evaluation concluded that the plan is likely toreach precautionary targets for the Eastern Baltic cod by 2015even at a low average recruitment as observed in previous twodecades. However, the level of SSB projected for 2015 was lowerthan currently estimated for 2010 from the most recent stockassessment. The realized recovery of the Eastern Baltic cod hasthus been considerably faster than projected, assuming previouslow recruitment [22]. This confirms that the applied stock–recruitment relationship is the major driver of stock dynamicsand determines the probability of Eastern Baltic cod stockrecovery [7].

The relatively high recruitment in most recent years, mainlybeing responsible for the rapid recovery of the Eastern Baltic cod,is still only about a half of the average recruitment level observedin the 1960–1980s. But in relative terms, the recruitment wasoutstandingly high, especially when considering the low SSB,which originated these year-classes (Fig. 3). Thus, the exampleof the Eastern Baltic cod supports the earlier findings thatrecovery of a stock is generally more likely at positive recruitmentevents related to favourable productivity regimes [3,23,24]. Theobserved high recruitment production per unit of SSB of theEastern Baltic cod stock in most recent years is likely related to acomplex of environmental and/or ecological processes, whichaffect reproduction and survival of early and juvenile life stages[25]. Fisheries could potentially influence the survival of pre-recruit cod as well, mainly through discarding. Discarding ofyoung cod in the Eastern Baltic has indeed reduced in the mid-2000s [6] due to introduction of a more selective trawl [26,27].However, available discard data suggest the numbers of coddiscarded as age 1 being relatively low also prior to the recentdecline in discarding (around 2% of the recruitment).

Larger incoming year-classes are likely to be responsible forthe recent change in selection pattern towards higher selection ofcod at age groups 4–5. A number of new regulations on fishinggears have been implemented in the period since 2002 [27]. Theseare, however, mostly expected to influence the selection of youngcod, and not the selection pattern of older fish. A fact that likelycontributed to a change in selection pattern was a reduction inthe proportion of cod landings taken by gill-netters, whichgenerally catch a relatively larger proportion of older cod [6]. In2005, around 40% of the Eastern Baltic cod landings were taken bygill-netters; this proportion was reduced to 30% by 2009. Despiteits effect on the average F, the change in selection pattern had nomeasurable effect on the spawning stock biomass (Figs. 4 and 5).

Year2004

Rel

ativ

e ch

ange

in T

AC

0.2

0.4

0.6

0.8

1.0

1.2

cod-2532 cod-2224 cod-kat cod-nsea cod-scow cod-iris

2005 2006 2007 2008 2009

Fig. 7. Changes in the TAC of some selected cod stocks in 2005–2009 relative to

the TAC in 2004. Acronyms denote cod in the Eastern Baltic (cod-2532), Western

Baltic (cod-2224), Kattegat (cod-kat), North Sea (cod-nsea), west of Scotland

(cod-scow) and Irish Sea (cod-iris).

Large reductions in catch at the start of the recovery processhave often played a key role in the ability of a fish population torecover [23,24]. In relation to this, the rapid recovery of theEastern Baltic cod is exceptional as catches were not drasticallyreduced in this period and only to the extent corresponding toillegal fisheries. Reducing TAC did not contribute significantly tothe reversal of the negative biomass trend and recovering thestock to above safe biological limits by 2009. However, theharvest control rules for setting TAC under the management plancontributed substantially to rebuilding of the stock from 2009onwards. The relatively low target F and the 15% constraint forinter-annual changes in TAC prevented an immediate increase infisheries removals in reaction to the increased biological produc-tion, and thereby allowed the stock to accumulate biomass, giventhat compliance with the TAC was ensured.

0.5

0.0

-0.5

-1.0

Pro

porti

on o

f cha

nge

cod-

2532

cod-

2224

cod-

Kat

cod-

nsea

cod-

scow

cod-

iris

Fig. 8. Recent changes in mortality (estimated total mortality in excess of

assumed natural mortality), spawning stock biomass (SSB) and recruitment

of some selected cod stocks. The proportion of change is calculated as

(xpresent�xprevious)xprevious�1 , where ‘‘present’’ values are for 2009 for mortality and

SSB, and average for 2005–2009 for recruitment; ‘‘previous’’ values are for 2002–

2004 (data from [6,8,11]). Acronyms denote cod in the Eastern Baltic (cod-2532),

Western Baltic (cod-2224), Kattegat (cod-kat), North Sea (cod-nsea), west of

Scotland (cod-scow) and Irish Sea (cod-iris).

M. Eero et al. / Marine Policy 36 (2012) 235–240240

In comparison with some other depleted cod stocks in Eur-opean waters, it is noteworthy that the Eastern Baltic cod hasrecovered without a major reduction in TAC. In fact, among thecod stocks in the Baltic Sea, Kattegat, North Sea, Celtic Sea andwest of Scotland, which are characterised by high mortality andrelatively low stock size in recent years, the Eastern Baltic cod hasbeen subjected to least reductions in TAC in recent five years(Fig. 7). In contrast, the development of F and SSB of the EasternBaltic cod stock are far more positive than in any other of thesestocks. Management of most of these stocks has severe problemswith unallocated removals, which are in some cases estimated tobe several times higher than reported landings [6,8,11]. In such asituation, pronounced reductions in TAC have apparently hadlimited effects in reducing removals. Moreover, recent changes inrecruitment are also most positive for the Eastern Baltic codcompared to the other cod stocks (Fig. 8). In the Baltic Sea, cod isthe dominant species in the demersal fisheries [22,28]. Conse-quently, mixed fisheries issues, which complicate fisheries man-agement for many other areas [29], are of minor importance inthe management of the Eastern Baltic cod stock.

In conclusion, the example of the Eastern Baltic cod demon-strates that a substantial reduction in F can be achieved whencorrespondence between the TAC and fisheries removal isensured. Rapid recovery of the stock, however, requires highrecruitment production. Relatively strong year-classes enteringthe fisheries would have reduced F of the Eastern Baltic cod evenat constant catches. When stock production increases due tohigher recruitment, positive surplus and consequently an increasein biomass can be achieved without a drastic decline in catch. Incontrast, attempts to recover some other depleted European codstocks by pronounced reductions in TAC, but at relatively poorrecruitments, have so far been less successful.

Acknowledgements

The present study is based on the results of the EU FP6 SpecificTargeted Research Project 022717 (UNCOVER) and contributes tothe EU FP7 Integrated Project 212085 (MEECE), and to the jointEU FP7 (217246) and the Baltic Sea research and developmentprogramme BONUS project ECOSUPPORT.

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