Con en s lis s a ailable a ScienceDi ec
Ma ine Policy
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Compa ing economic and biological managemen objec i es in he
comme cial Bal ic salmon ishe ies
Maija Holma
a,⁎
, Ma ko Lind oos
a
, A so Romakkaniemi
b
, Soile Oinonen
c
a
Depa men o Economics and Managemen , P.O. Box 27, 00014 Uni e si y o Helsinki, Finland
b
Na u al Resou ces Ins i u e Finland, Paa o Ha aksen ie 3, 90570 Oulu, Finland
c
Finnish En i onmen Ins i u e, La oka anonkaa i 11, 00790 Helsinki, Finland
ARTICLE INFO
Keywo ds:
MEY
MSY
CFP
Bioeconomics
Op imiza ion
Age-s uc u e
ABSTRACT
This pape compa es wo ishe ies managemen objec i es ecognized in he li e a u e and applied in p ac ice:
maximum sus ainable yield (MSY) and maximum economic yield (MEY). The Eu opean Union Common Fishe ies
Policy (CFP) se s he minimum a ge o ish popula ions a he MSY le el, de ined as he s ock le el ha
maximizes he ish ca ch. Al hough MSY is use ul in nudging o e -ha es ed s ocks back o biologically sus-
ainable le els, he CFP equi es he ha es ed s ocks o be main ained abo e le els ha can p oduce MSY
wi hou add essing he exac de ini ion o “abo e MSY”. One possibili y o main aining ish s ocks abo e MSY is
o apply he maximum economic yield (MEY) ha maximizes he discoun ed ne p esen alue o he ishe y.
Compa ison o he economic and ecological ou comes o he wo objec i es in he No he n Bal ic salmon ishe y
is conduc ed by applying a dynamic op imiza ion model coupled wi h age-s uc u ed salmon s ock dynamics.
The esul s a e u he es ed o he changes in s ock- ec ui men pa ame e s, and ela ed o he p ecau iona y
managemen a ge o eaching 75% smol p oduc ion capaci y. A sensi i i y analysis o he economic pa a-
me e alues is conduc ed. The esul s show ha as a a ge , MEY pe o ms be e han MSY in bo h conse ing
he s ocks and p o iding economic iabili y o he ishe s. Ta ge ing MEY while keeping MSY a hand as a
minimum biological objec i e was ound o be a p agma ic objec i e ha is in line wi h he goals o he CFP and
he EU Blue G ow h S a egy.
1. In oduc ion
Fishe ies managemen aims o ensu e he long- e m sus ainable use
o ish s ocks among o he desi able ou comes. A selec ion o e e ence
poin s a e used as ools o ela e he ecological eali ies o ish s ock
dynamics wi h he managemen objec i es. Wi h a ying success and
ailu e, maximum sus ainable yield (MSY) has been widely applied as a
managemen objec i e ha is said o de ine an ope a ional and quan-
i iable goal (e.g., [18,38,45]). The Eu opean Union Common Fishe ies
Policy (CFP) [11] is one example om he adhe en s o MSY – he
o e all managemen a ge o he CFP is o main ain ha es ed ish
s ocks abo e MSY le els. MSY de ines he maximum le el o ha es
ha can be aken wi hou educing he s ock size in he long un. S a ed
mo e ully, ha es ing a he le el o MSY esul s in he maximum
g ow h a e o he popula ion. In he CFP, MSY answe s he need o
de ining a minimum sus ainable le el o ish s ocks om a biological
poin o iew. This a ge is impo an since he ishing mo ali y
exceeds he MSY le el in 50% o ish s ocks
1
in he EU [50].
The e is, howe e , ano he se o equi emen s o a sound man-
agemen a ge aside om he biological de ini ion o sus ainabili y.
Acco ding o hese gene al ishe ies managemen equi emen s – also
s a ed in he EU CFP [11] – economic, social and employmen bene i s
as well as he a ailabili y o ood mus be consis en ly aken in o ac-
coun [35]. The lack o co espondence be ween he mul iple, and a
imes e en con lic ing, objec i es o he CFP is s iking, as is he me e
de ini ion o a limi e e ence poin a MSY, ye no uncommon when
iewed om a global pe spec i e [9,16]. No p ecise o mula ion o
“abo e MSY” s ock le els is p o ided, no is a u he quan i iable goal
gi en o mee he economic, social and employmen bene i s in he CFP.
I is clea ha i ishe ies managemen is o mee sus ainabili y by
combining biological, economic and social dimensions, i is no su i-
cien ha i s goals be only implici ly de ined [6].
To his end, he use o a managemen objec i e called maximum
economic yield (MEY) in he case o No he n Bal ic salmon ishing is
h ps://doi.o g/10.1016/j.ma pol.2018.11.011
Recei ed 18 Decembe 2017; Recei ed in e ised o m 26 Sep embe 2018; Accep ed 6 No embe 2018
⁎
Co espondence o: Depa men o Economics and Managemen , P.O. Box 27, La oka anonkaa i 5, 00014 Uni e si y o Helsinki, Finland.
E-mail add ess: [email p o ec ed] (M. Holma).
1
Taking in o accoun he ish s ocks o which he F
MSY
indica o has been compu ed.
Ma ine Policy xxx (xxxx) xxx–xxx
0308-597X/ © 2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license
(h p://c ea i ecommons.o g/licenses/BY-NC-ND/4.0/).
Please ci e his a icle as: Holma, M., Ma ine Policy, h ps://doi.o g/10.1016/j.ma pol.2018.11.011
explo ed, and compa ed wi h a ge ing MSY. Ins ead o maximizing he
ha es , MEY maximizes he sum o discoun ed ne p esen alue o he
ishe y o e ime o cap u e he e ec s o ca ch p ice, ishing cos s and
discoun ing [19,30]. To es he p agma ic MEY objec i e ha is in line
wi h bo h he CFP and he EU Blue G ow h S a egy [10], as well as he
adi ional MSY objec i e, a sensi i i y analysis is conduc ed. In addi-
ion, he biological unce ain y o e he s ock- ec ui men pa ame e s
is conside ed by ep oducing he modelling esul s wi h he s ock- e-
c ui men pa ame e s om he yea s 2010–2014. The esul s o bo h
MEY and MSY managemen a e compa ed agains he p ecau iona y
a ge se by he In e na ional Council o he Explo a ion o he Sea
(ICES) o eaching 75% o he Po en ial o Smol P oduc ion Capaci y
(PSPC) [20].
2. Fishe ies managemen a ge s in heo y and p ac ice
Alongside he biological eali ies o ish s ocks, ishing is essen ially
d i en by he economic maximiza ion o ishing ac i i y, and he po-
en ial economic bene i s om an e icien ly managed ishe y a e well
es ablished [12,13,51]. The a ailabili y o ish s ocks changes o e
ime, which makes he con inuum o ime impo an in ishe ies man-
agemen : Sco [51] s a es ha he p ospec s o e iciency in ishe ies
managemen s a egies inc ease when mo ing om sho - e m o long-
e m managemen . The ade-o be ween ishing now o la e , i.e.,
choosing o ha es he ish o gain he p o i s immedia ely e sus
con ibu ing o u u e ish esou ces by conse ing he ish while ha ing
o wai o he p o i s, is highligh ed in he seminal wo k on dynamic
de ini ion o MEY [2,3].
Whe he MEY can pe o m be e han MSY is unde deba e. The
biological, economic, and social goals a e essen ially con lic ing: o
example, MSY p o ides maximum biological p oduc ion, ye ailing o
maximize employmen , ecosys em p ese a ion and economic p o i -
abili y [16,48]. Hilbo n [16] also poin s o he simila i ies o en i on-
men al p o ec ion and economic maximiza ion in ha p oponen s o
hese objec i es would p e e high ish biomasses alongside s able
ca ches and low ishing e o . G a on e al. [14] a gue ha a ish s ock
a MEY is bigge han a s ock a MSY as long as he p ices, cos s, and
discoun a es a e easonable, which is opposed by Cla k e al. [4], who
sugges ha he possibili y o s ock ex inc ion unde MEY managemen
canno be igno ed. In esponse o he c i ique, G a on e al. [55] show
ha i he cu en biomass le el is lowe han a dynamic MEY solu ion,
no ade-o be ween s ock conse a ion and p o i abili y exis s. The
global pe o mance o MEY was es ed wi hin a su plus-p oduc ion
model se up whe e da a om 4713 ishe ies was analysed o ind ha a
managemen egime elying on MEY simul aneously maximizes he
global annual p o i s and biomass [5]. La ge di e ences be ween MSY
and MEY objec i es eme ge when he objec i es a e compa ed using
dynamic age-s uc u ed modelling and endogenous ha es ing se-
lec i i y [53].
As shown abo e, he simula ions o MEY managemen a e plen i ul
in he li e a u e; howe e , MEY has been implemen ed only ecen ly as
a p ac ical policy. In Aus alia, o example, he MEY based manage-
men o he no he n p awn ishe y (NPF) was implemen ed in 2008,
and has ecen ly ea ned a sus ainabili y ce i ica e om Ma ine
S ewa dship Council [44]. Ini ially, he unde lying bioeconomic model
buil o suppo he NPF en ailed a delay-di e ence model [7,30],
which was upda ed o conside he size-s uc u ed s ock dynamics, an
in eg a ed p o i unc ion and o wa d p ojec ions o size- ela ed p awn
p ice and uel cos s [46]. Building on he expe iences om he NPF
managemen , Dichmon e al. [8] p esen challenges ha occu in im-
plemen ing MEY in p ac ice, especially in speci ying he bioeconomic
es ima ion o MEY. No man-López and Pascoe [42] ound ha he MEY
based managemen in he NPF esul ed in o e all losses in he sho
e m, bu ne economic bene i was c ea ed in he long e m. Despi e he
challenges in speci ying he bioeconomic es ima ion o an MEY a ge ,
he Aus alian example indica es ha he challenges can be o e come
[19]. In 2007, he Pa ies o he Nau u Ag eemen implemen ed a
ans e able e o scheme in he Wes e n and Cen al Paci ic Ocean
una ishe ies aiming o maximizing economic e u ns in he long un
[15].
The Bal ic salmon s ocks a e u ilized by sequen ial ishe ies, in-
cluding in e na ional comme cial o sho e long lining, comme cial
coas al ap ne ishing and ec ea ional angling in i e s. The se-
quen ial na u e o he ishe y is explained by he anad omous li e cycle
– salmon a e bo n in a speci ic na al i e , mig a e o he sea, and e u n
o he na al i e o spawning – in addi ion o he spa ial ex en o
salmon eeding and spawning mig a ions. Du ing he spawning mi-
g a ion, salmon a e a ge ed by ap ne s along he mig a ion ou e on
he coas , and hen by ec ea ional angle s a he i e . The salmon
s ock o he Ri e To nionjoki is by a he la ges salmon s ock in he
Bal ic Sea egion, accoun ing o abou hal o all wild salmon in he
egion [25]. Coas al ap ne s a e he mos impo an i em o gea in he
Bal ic comme cial salmon ishe y; in 2016, ap ne ishing caugh
57.5% o he o al nominal ca ches in he Bal ic Sea egion [26]. To -
nionjoki i e s ock con ibu es o 34% o he o al salmon abundance
in he Gul o Bo hnia and is p edominan ly ha es ed on he Finnish
coas o he Gul [25]. The ICES uses he Po en ial Smol P oduc ion
Capaci y (PSPC) as he basis o es ima ing he e e ence poin s, and
sugges s o each a leas 75% o he PSPC in o de o eco e he
salmon popula ions o he MSY le el [20].
Thus, gi en he impo an ole o he To nionjoki in ep oduc ion
and ca ches especially o he Finnish salmon ishing indus y, he ocus
o his pape is on he To nionjoki i e s ock. Fu he mo e, Finnish
economic da a o he economic pa ame e s is used. The ha es ing
quo a o salmon is se o p o essional ishing only, and since he e-
c ea ional ishing is no explici ly conside ed in quo a decisions, his
pape conside s only he biological e ec o ec ea ional ishing on he
amoun o eggs p oduced by spawne s. This pape analyses he ela i e
pe o mance o MSY and MEY objec i es in he comme cial ap ne
ishe y a ge ing salmon o he Ri e To nionjoki in he No he n Bal ic
Sea o deepen he unde s anding o how o in eg a e economics in o
ishe ies managemen decisions. Bioeconomic modelling coupled wi h
dynamic op imiza ion is used in o de o compa e he economic and
ecological e ec s o a ge ing MEY, which maximizes he discoun ed
bene i s om he ishe y o MSY, which maximizes he ha es . Bo h
objec i e unc ions a e buil upon an age-s uc u ed salmon s ock
model. Addi ionally, he biological unce ain y o changes in s ock- e-
c ui men pa ame e s was analysed, and an economic sensi i i y ana-
lysis was ca ied ou . The ou comes o MSY and MEY objec i es a e
analysed wi h espec o he gene ic ICES scien i ic ad ice (2008) o
a ge ing 75% o PSPC.
3. Bioeconomic model o he No he n Bal ic salmon ishe y
3.1. To nionjoki salmon s ock dynamics and ha es ing
To os e he inclusion o ime-delay e ec s in he modelling o
s uc u ed popula ion (e.g. Tah onen [52]), an age-s uc u ed model-
ling app oach is u ilized o desc ibing he salmon s ock dynamics in
his pape . The age-s uc u ed salmon popula ion dynamics a e based
on he model i s desc ibed in Holma e al. [17] and Appendix A de-
sc ibes he model and i s pa ame e s in de ail. The baseline biological
pa ame e s alues a e lis ed in Tables A.1 and A.2. The salmon s ock
de elops acco ding o he ollowing unc ion, which speci ies he
numbe o salmon aged i=(1,...,10) a Bal ic Main Basin be o e coas al
ishing a ime +1(
+
sob i , , 1
) as a unc ion o he li e his o y ma ix
Aob ,
and he numbe o salmon aged ia ime unde he chosen manage-
men objec i e ob=(MEY o MSY):
=
+
s A s
ob i ob ob i , , 1 , , ,
.
The numbe o homing salmon (
spob i , ,
) o age ia ime is he e o e
gi en by
=sp s e y
ob i ob i mS i
, , , ,
, whe e
mS
is he ins an aneous na u al
mo ali y o homing salmon and ec o
yi
is he sha e o salmon o age i
heading o he spawning i e . The coas al ca ch o To nionjoki i e
M. Holma e al. Ma ine Policy xxx (xxxx) xxx–xxx
2
s ock is almos en i ely ha es ed by he Finnish coas al ap ne lee
[27]. The amoun o homing salmon is used as an inpu in he ha es
unc ion o he coas al ap ne lee :
=( )
H e sp1
ob i q E ob i
, , , ,
iob ,
(1)
Thus, he annual p o i s (
)
ob ,
o he ishe y unde a chosen man-
agemen objec i e, summed o e he salmon age g oups i, a e de ined
by he o al e enue minus he o al cos s om ha es ing:
=
=
p H cE
ob
i
iob i ob ,
1
10
, , ,
(2)
whe e ishe s ace he age-speci ic salmon wholesale p ices o gu ed
salmon,
pi
, and linea cos s pe uni o e o ,
c
, mul iplied by he choice
a iable, ishing e o
Eob ,
. The economic pa ame e alues a e p e-
sen ed in Table 1. The ishing e o is exp essed in gea days de ined as
uni s o gea mul iplied by he numbe o ishing days. The cos pe uni
o e o is scaled wi h he pa ame e θ o ma ch he cos s wi h he
p opo ion o he ca ch o igina ing om To nionjoki i e in he o al
salmon ca ch.
3.2. Dynamic op imiza ion model
To quan i y he economic and ecological e ec s o a ge ing ei he
MEY, which maximizes he discoun ed bene i s om he ishe y, o
MSY, which maximizes he ha es , a dynamic op imiza ion model is
used. The p ojec ions o e a 100 yea ime pe iod a e ca ied ou using
a KNITRO
2
nonlinea op imiza ion oolbox “kni oma lab” in MATLAB
8.3.
3
3.2.1. Maximum economic yield (MEY)
The MEY managemen objec i e (ob=MEY) akes in o accoun he
economic cha ac e is ics o he coas al ap ne ishe y, including
salmon ca ch p ices, ishing cos s and discoun ed alue o u u e ben-
e i s, in calcula ing he e enues om ha es ing. To discoun u u e
bene i s, an economic discoun a e ( = 0.03) is used. Following he
app oach o Kompas e al. [30] he MEY managemen a ge maximizes
he sum o discoun ed ne p esen alue o he ishe y o e ime by
choosing he op imal le el o ishing e o :
=
+
=
NPV
max [ ]
(1 )
MEY
E
MEY
1
100
,
1
MEY ,
(3)
subjec o an ini ial guess ha gea days, an ini ial condi ion o
si,1
,
=
+
sMEY i , , 1
s A
MEY i MEY , , ,
and he cons ain ha
=H e y s(1 )
MEY i q E iMEY i , , , ,
iMEY ,
.
3.2.2. Maximum sus ainable yield (MSY)
In calcula ing MSY, he objec i e is o ind he op imal le el o
annual e o ha maximizes he ha es o e ime (ob=MSY). The
op imiza ion p oblem unde MSY managemen is de ined as ollows:
=
=
MSY Hmax [ ]
E
MSY i
1
100
, ,
MSY ,
(4)
subjec o an ini ial guess o
=E5000
MSY ,1
, an ini ial condi ion o
si,1
,
=
+
sMSY i , , 1
s A
MSY i , ,
and he cons ain ha
=H e y s(1 )
MSYi q E iMSY i , , ,
iMSY ,
.
4. Resul s
4.1. Compa ing he managemen objec i es
Sol ing he dynamic op imiza ion models p esen ed in Eqs. (3) and
(4) o ind he e o le el ha ei he maximizes he ha es (ob=MSY)
o he ne p esen alue (ob=MEY) yields he esul s depic ed in Fig. 1
and in Table 2. The models a e popula ed wi h s ock- ec ui men
pa ame e s om he assessmen yea 2013. The gene ic ad ice om he
ICES o a ge ing 75% o he PSPC in he Bal ic Sea [20] is used o
de e mine how he modelling esul s ela e o he long e m p ecau-
iona y objec i e. The i e speci ic smol p oduc ion a ge s used in he
ICES ad ice a y be ween 60% and 80% o he PSPC.
The la ges s eady s a e ishing e o (Fig. 1a) was ealized unde
MSY managemen , and i ook app oxima ely 30 yea s o each he long
un equilib ium. The op imal e o le el unde he MEY managemen
a ge equi ed a mo a o ium on he salmon ishe y o i s wo yea s,
because he ini ial popula ion was low, and he mo a o ium allowed he
s ock o eco e . As he model assumes pe ec malleabili y, he adap-
ion cos s o he ishe y incu ed by he mo a o ium a e no explici ly
ea ed. Compa ing he a e age ac ual e o le el om 2013 o 2016 o
he op imiza ion esul s (Fig. 1a) e eals ha he ac ual e o le els
ha e been close o he op imized MSY e o le el in 2013 and 2014.
The summed discoun ed ne p esen alue o maximizing he ha -
es unde MSY is 4.06 M€, whe eas maximizing he alue o he ishe y
unde MEY yields a ne p esen alue ha is h ee imes highe
(Table 2). Annual undiscoun ed ishe y p o i s we e calcula ed using
Eq. (2) and we e posi i e o e ime o bo h he MSY and MEY objec-
i es (Fig. 1b). Du ing he i s se en yea s o op imiza ion, he p o i s
we e simila unde bo h managemen objec i es, and MSY pe o med
sligh ly be e du ing his ini ial pe iod. Howe e , in he long e m, he
s eady s a e p o i s unde MEY we e mo e han wo imes he p o i s
unde MSY. The economic e iciency o e o de ined as he a io o
p o i s pe e o unde MEY was ela i ely highe han unde MSY,
since he p o i s we e conside ably lowe unde MSY han unde MEY
while he e was a smalle dispa i y in ha es le els (Fig. 1c). Unde
MSY, he cos o uni o ha es is much highe han unde MEY. As-
suming ha Finland a ge s he MSY le el ins ead o MEY, he ishing
sec o will lose 263,000 € in annual p o i s in he long e m.
The numbe o smol s, i.e., he numbe o salmon ha begin he
mig a ion om he na al i e o he Bal ic Sea, ep esen s he s a us o
he salmon s ock and is depic ed in Fig. 1d. Unde MSY, he smol
p oduc ion o e ime was 23.5% smalle han he smol p oduc ion
unde he economic e e ence poin . Using he biological da a om yea
2013, nei he MSY no MEY smol le el a ained he PSPC a ge le el.
As he ishing e o in he ini ial pe iods is high unde MSY manage-
men , he ansi ion o he s eady s a e smol p oduc ion is mo e p o-
nounced du ing he i s decade when compa ed o MEY managemen ,
which is essen ially limi ed by he mone a y cos placed on e o ha
Table 1
Economic pa ame e alues.
Symbol De ini ion Value Sou ce (Uni )
θTo nionjoki salmon in o al ca ch 0.345 ICES (2015)
c
Uni cos o e o o a seal-sa e ap ne P opo ion o 47.945θKulmala e al. [56]
a
(€ / gea day)
pi
A e age age-speci ic ca ch p ice [0 0 0 0 0 9.127 30.54 56.13 54.92 66.25] Luke (2015) (€ / ish)
a
The uni cos in coas al ap ne ishing is based on Kulmala e al. [56], as upda ed in Salenius [57], and con e ed o 2015 eu os [58].
2
Ziena.
3
The Ma hWo ks Inc.
M. Holma e al. Ma ine Policy xxx (xxxx) xxx–xxx
3
ac s as a bu e o changes in he numbe o smol s.
4.2. E ec o changes in salmon s ock- ec ui men pa ame e s
The e is conside able unce ain y in he yea -speci ic es ima es o
salmon s ock- ec ui men pa ame e s, which is e lec ed by he changes
in he annual upda es o he pa ame e es ima es (Table 3). The bioe-
conomic op imiza ion esul s gi en he s ock- ec ui men pa ame e s
es ima ed by he ICES in assessmen yea s 2010–2014 (Table 3) we e
compa ed by epea ing he op imiza ion o he MSY and MEY objec-
i es wi h he s ock- ec ui men pa ame e s o he assessmen yea s
2010–2014. He e, he s eady s a e esul s o he op imiza ion a e p e-
sen ed.
Wi h he assumed p ices, cos s and discoun a e, choosing MEY
managemen b ough abou highe p o i s and ish s ocks in all yea s
om 2010 o 2014. Fishe y p o i s we e consis en ly highe unde MEY
han unde MSY managemen . Wi h he s ock- ec ui men pa ame e s
om assessmen yea 2010, ishe s ace nega i e p o i s unde MSY
managemen in he long un, whe eas unde MEY managemen , he
same da a gi e 202 M€ in p o i a he s eady s a e. The ishing e o is
consis en ly lowe unde MEY han MSY; he highes s eady s a e le el
o e o is ealized wi h da a om he yea 2012 ha ep esen s a high
p oduc i i y o he s ock (MSY 81,124 gea days, MEY 48,244 gea -
days), while he lowes e o is ealized wi h da a om he yea 2010.
As shown in Fig. 2, om an economic poin o iew, he p ecau-
iona y 75% o he PSPC a ge is easible only wi h he biological
pa ame e s om assessmen yea s 2011 and 2014. Wi h pa ame e s
om assessmen yea s 2010, 2012 and 2013, mee ing he 75% o PSPC
a ge would en ail cos s o socie y, as he ishing e o would be below
he economic op imum le el.
4.3. Va ia ion o economic ac o s
Fish ca ch p ices and ishing cos s a e cen al in MEY managemen .
On he one hand, hey make he ishe y p o i able and sus ainable when
he economic pa ame e s a e wi hin easonable limi s. On he o he
hand, i he economic pa ame e s become un easonable in ha p ices
a e ex emely high and cos s low, he p o i s o he ishe y may o e ide
i s sus ainabili y. To his end, he baseline scena io desc ibed in
Sec ions 3.2.1 and 3.2.2 is used wi h s ock- ec ui men pa ame e s om
yea 2013 o he economic sensi i i y analysis.
Due o he ma ke in eg a ion o wild caugh and a med salmon in
Finland, he p ice o impo ed a med salmon de e mines he p ice o
wild caugh salmon [49]. Un il ecen ly, he p ice o wild salmon has
dec eased subs an ially as a esul o inc eased compe i ion wi h he
eadily a ailable and cheap No wegian a med salmon. Howe e , he
global p oduc ion o a med salmon may dec ease because o a con-
inuing en i onmen al and sani a y c isis in he Chilean salmon a ming
indus y [34,36] and he slackening p oduc ion g ow h o he No we-
gian a med salmon indus y [1]. Since he demand o salmon is no
dec easing, his may esul in highe salmon p ices. Thus, he MEY
scena io is es ed wi h espec o p ice changes. In addi ion, he e ec s
o changes in he uni cos o e o and in he discoun a e we e
analysed.
Changes in he economic ac o s a ec he p ospec s o achie ing
he smol p oduc ion a ge as shown in Table 4. Wi h a 30% dec ease
in p ices he 75% o PSPC a ge is eached in he long- e m. Inc ease in
ca ch p ices has o be e y high o make he ishing e o high enough
o each he e o le el in MEY ha co esponds o he e o in MSY; a
3.6- old inc ease in ca ch p ices ( he baseline wholesale p ice a e aged
o e ages is 5.01 €/kg and he inc ease co esponds o 17.9 €/kg) made
he s eady s a e ishing e o unde MEY highe han unde MSY, which
also esul ed in a smol p oduc ion le el smalle han i was unde MSY.
Discoun a es had only mino e ec s on he salmon s ock, whe eas he
summed ne p esen alue was a ec ed. The ole o he discoun a e is
gene ally conside ed small in ishe ies managemen since i is usually
domina ed by he sensi i i y o ishing cos s o changes in he s ock
le el [19].
5. Discussion and conclusions
In his pape , he pe o mance o MEY as a managemen a ge ha
explici ly de ines he le el “abo e MSY” acco ding o he CFP was
analysed. Thus, he economic and ecological e ec s o a ge ing he
maximized ha es (MSY) e sus he maximized discoun ed ne p esen
alue o he ishe y (MEY) we e compa ed by applying bioeconomic
modelling and dynamic op imiza ion based on age-s uc u ed salmon
s ock dynamics. The baseline modelling esul s show ha choosing o
Fig. 1. Op imal ime pa hs o (a) ishing e o
in gea days, (b) ishe y p o i s in €, (c) ha es
in numbe o salmon and (d) numbe o salmon
smol s unde MEY and MSY managemen wi h
s ock- ec ui men pa ame e s om assessmen
yea 2013. The 75% o PSPC a ge is a gene ic
MSY based objec i e p oposed by he ICES
[20]. Ac ual e o s om 2013 o 2016 e e o
he comme cial salmon ap ne ishe ies e -
o s om assessmen uni 1 (AU1) [27]. Ho -
izon al axis e e s o ime in yea s om 2013
onwa d.
M. Holma e al. Ma ine Policy xxx (xxxx) xxx–xxx
4
a ge MEY enhances he ep oduc i e capaci y o he salmon s ock
while also p o iding highe p o i s o he ishe s. In MEY, ishing cos s
make he ishing e o an essen ially sca ce esou ce, and pu ing mo e
e o in o ishing also inc eases he cos s, i.e., he p ice o e o . This is
why he e o is usually lowe unde MEY compa ed o he e o unde
MSY. Unde MSY, he only limi ing ac o o ishing ac i i y is he size
o he ish s ock, whe eas ishing e o is no conside ed cos ly a all.
Thus, aside he size o he s ock, in MSY managemen all ac o s a -
ec ing ishe s' beha iou a e dis ega ded.
The sensi i i y analysis o MEY managemen showed ha inc eased
p ices and dec eased cos s imp o e he economic pe o mance o he
ishe y bu diminish he ep oduc i e capaci y o he salmon s ock. The
inhe en unce ain y in assessing he s ock- ec ui men da a is e lec ed
in bo h he esul s o MSY and MEY managemen . Ou esul s show ha
he ela i e economic adeo be ween MSY and MEY is highes when
he p oduc i i y o he ish s ock is high. In his si ua ion, he e iciency
o e o dec eases conside ably unde MSY managemen . Thus socie y
loses he mos om a ge ing MSY when he p oduc i i y o a salmon
s ock is high.
Ou esul s p o ide an example o op imized ishe ies managemen .
These esul s can be used o linking he economic iabili y and
ecological sus ainabili y in managing he coas al salmon ap ne
ishe y, which has ecen ly become he mos impo an comme cial
salmon ishe y in Finland. In he li e a u e, MSY is adi ionally jux a-
posed wi h MEY, which is unnecessa y in ou opinion as he objec i es
could be used as complemen s o capi alize on he bes ea u es o each
o hem. While a ge ing MEY, MSY could be used as an ecological limi
i he economic eali ies would sugges smalle s ock sizes han MSY
managemen , ha is, when MEY would no longe esul in a s a e o he
s ock ha is “abo e MSY”. MSY has an impo an ole as a limi a ge
and can be used as a cons ain o he MEY ad ice in an appa en ly
ela i ely a e si ua ion o high ish p ices, excep ionally low ishing
cos s o a high discoun a e, which a e condi ions ha could lead o a
s ock collapse unde MEY managemen . Based on he modelling esul s,
aiming o MEY and keeping MSY a hand is p oposed, as also sugges ed
by Voss e al. [54] who in oduce an ecologically-cons ained Maximum
Economic Yield (eMEY) in he case o he eas e n Bal ic cod ishe y.
Such a holis ic app oach would be a s ep owa ds he ecosys em-based
managemen as well as eaching he goals se in he EU Blue G ow h
S a egy.
Since he salmon ishing quo a is se o he comme cial ishe ies
only, he model in his pape conside s he op imiza ion o comme cial
ap ne ishing while conside ing he biological e ec s o ec ea ional
ishing. Howe e , he op imal managemen o sequen ial salmon ish-
e ies has been analysed by, e.g., Kulmala e al. [31], showing ha a
ealloca ion o ha es om o sho e o coas and i e would en ail
70% la ge bene i s in he case o he Simojoki i e salmon s ock.
These esul s a e suppo ed by Laukkanen [32], who shows ha ish-
e ies managemen could be imp o ed o ha ness he ull p oduc i e
po en ial o he No he n Bal ic salmon ishe y by mo ing away om
o sho e ishing. The o me ly domina ing o sho e ishe y now con-
ibu es o a much smalle p opo ion o salmon ca ches. The ongoing
ealloca ion o e o has also led o a shi owa ds ha es ing salmon
ha spawn o a e s ocked wi hin he coun y's own e i o y. This shi
o a mo e clea ly de ined owne ship o he salmon esou ce educes he
occu ence o s a egic beha iou among he sequen ial ishe ies ha
would o he wise equi e cos ly coope a ion and nego ia ion e o s
[33,43]. Modelling he economic dynamics o p o essional and e-
c ea ional ishe ies wi hin he con ex o MSY and MEY is le o u -
he s udy.
The scien i ic ounda ion o p o iding he managemen e-
commenda ions is s ill la gely based on biological modelling o he ish
s ocks. Ou modelling app oach is an example o coupling economic
and ecological sys ems in a ai ly simple single-s ock ishe y. This ype
o in eg a ed modelling is no ye an es ablished ool in suppo ing
managemen decisions, al hough i can p o ide in aluable in o ma ion
on he sus ainabili y and p o i abili y o ma ine esou ce use. The ICES
wo king g oup on in eg a ing ecological and economic models was
o ganized in 2015, and p o ides a p omising pla o m o in eg a ing
bioeconomic modelling wi h s ock-assessmen models. As ma ine
ishing is an essen ial elemen o in eg a ed coas al managemen , con-
side a ion o he socio-cul u al impac s and alues o ish, ishing and
ishe ies managemen (see e.g. [28,47]) would be a na u al ex ension o
he exis ing model. This could be done by e.g. elaxing he assump ion
Table 2
Baseline modelling esul s and cu en mean coas al ap ne ha es o To nionjoki salmon in numbe o ish om ICES sub-di isions 29–31 o e yea s 2010–2014.
Sum o discoun ed ne
p esen alue o e
ime (M€)
Annual undiscoun ed
p o i s a s eady s a e
( housand €)
Annual comme cial
ha es in numbe o ish
a s eady s a e
Op imal annual s eady s a e
e o in gea days
Numbe o smol s a
s eady s a e (in
millions) pe yea
Cu en mean comme cial
coas al ha es in numbe o
To nionjoki i e s ock ish
o e yea s 2010–2014
a
S a us quo 27,265
MSY 4.06 182.7 39,360 67,840 1.298
MEY 12.01 445.3 33,660 40,059 1.603
a
Mean coas al ha es es ima e is based on he esul s o he s ock-assessmen model by ICES [25] and includes a mino sha e o salmon ha es caugh wi h gill ne s.
Table 3
S ock- ec ui men pa ame e s o assessmen yea s 2010–2014.
Yea o assessmen Sou ce Alpha Be a PSPC median PSPC 75%
2010 ICES [21] 77.16 0.000384 2,090,000 1,567,500
2011 ICES [22] 54.11 0.000408 1,924,000 1,443,000
2012 ICES [23] 42.12 0.000374 2,408,000 1,806,000
2013 ICES [24] 53.31 0.000376 2,298,000 1,723,500
2014 ICES [25] 48.02 0.000383 2,020,000 1,515,000
62.1
77.6 73.4
69.8
81.7
47.5
61.7 60.7 56.5
66.6
0
10
20
30
40
50
60
70
80
90
2010 2011 2012 2013 2014
% o PSPC a ained
MEY: % o PSPC MSY: % o PSPC 75 % PSPC Ta ge
Fig. 2. Compa ison o pe cen age o he po en ial o smol p oduc ion capaci y
(PSPC) a ained in he s eady s a e wi h salmon ec ui men da a om assess-
men yea s 2010–2014. The dashed line indica es he gene ic 75% o PSPC
a ge sugges ed by he ICES.
M. Holma e al. Ma ine Policy xxx (xxxx) xxx–xxx
5
o pe ec malleabili y and gi ing a mone a y alue o bo h he non-
ma ke bene i o adi ional ishe ies’ exis ence and he salmon s ock as
pa o na u al he i age o analyze he employmen e ec s and im-
plica ions o he ishing communi ies and o econcile he e ec s o
sudden educ ions in ish s ock, ha es and e o . Fu he in eg a ed
assessmen and collabo a i e decision making could be de eloped by
in ol ing ishe s, scien is s, NGOs and policy make s as has been done
in he MEY based managemen o Aus alian Commonweal h ishe ies
[37].
The single-s ock modelling app oach could be ex ended om
To nionjoki i e s ock o conside he whole Bal ic salmon s ock ha is
essen ially cha ac e ized by mul iple i e s ocks wi h a ying p o-
duc i i ies. The op imal e o esul ing om a mixed-s ock ishe y
op imiza ion model is expec ed o be somewha lowe han he single-
s ock op imum epo ed in his pape , because To nionjoki i e s ock
ep esen s one o he highes p oduc i i ies among he Bal ic s ocks. In
case he ishe ies managemen e o s ac oss he Bal ic Sea we e no
cohe en , a game heo e ic modelling app oach could be used o ana-
lyze he e ec s o one coun y applying MEY managemen , while o he
coun ies s ick o he MSY managemen . Addi ionally, i should be
no ed ha he model builds on cons an cos and p ice unc ions, and
explo ing he e ec s o al e na i e unc ional o ms and ex ending he
p ice po olio o conside ish p ocessing would gi e new insigh in o
he economic and ecological dynamics o he ishe y sys em. These
ex ensions a e le o u u e s udies.
Acknowledgemen s
We hank Henni Pulkkinen om he Na u al Resou ces Ins i u e
Finland o p o iding he necessa y salmon s ock assessmen da a.
Funding
This esea ch was pa o he No den Top-le el Resea ch Ini ia i e
subp og am, “E ec S udies and Adap a ion o Clima e Change,”
h ough he No dic Cen e o Resea ch on Ma ine Ecosys ems and
Resou ces unde Clima e Change (No MER), and i was unded by he
Ella and Geo g Eh n oo h Founda ion and he Ol i Founda ion.
Decla a ion o in e es
None.
Appendix A
The s ock dynamics o salmon a e modelled by mimicking as closely as possible he ICES salmon assessmen model [39,40,41]) used o gi ing
scien i ic ad ice ha is equi ed by he EU CFP. To p edic he salmon popula ion dynamics, an age-s uc u ed ma ix model, some imes e e ed o
as he Leslie model, is used building on he salmon model i s used in Holma e al. [17]. The o iginal ICES s ock assessmen model is modi ied o
conside he wild salmon s ock and o accommoda e he ma ix modelling app oach. The model is pa ame ized o he To nionjoki i e s ock
u ilizing he ICES s ock assessmen esul s (Tables A.1 and 3).
Salmon a e classi ied in o
i
∈{1,…,10} age g oups. The salmon li e his o y model is cons uc ed as ollows o calcula e he numbe o salmon ha
ha e su i ed he o sho e longline ishe y a ime +1in he Main Basin be o e he spawning un:
=
…
…
…
…
+
+
+
+
+
s A s
s
s
s
s
FEC FEC FEC FEC
SUR
SUR
SUR
s
s
s
s
0 0 0
0 0 0
0 0 0
,
ob ob ob
i
i
i i
i
i
i
, 1 , ,
1, 1
2, 1
1, 1
, 1
1 2 1
1
2
1
1,
2,
1,
,
whe e he ec o
+
s,
ob 1,
con aining he numbe o indi iduals in each age class
i
a ime
+ 1
, is de e mined by he popula ion p ojec ion ma ix
Aob ,
mul iplied by he ec o
sob ,
,con aining he numbe o age
i
indi iduals a ime
. Salmon s ock dynamics a e speci ic o he managemen objec i e,
ob
{MEY o MSY}. The biological and ishe y ela ed pa ame e s and he elemen s o
A
a e p esen ed in Tables A.1 and A.2. In he ma ix
A
, he
elemen
FECi
is he pe capi a e ili y o age class
i
, and
SURi
is he age speci ic su i al a e a age i. The ICES s ock assessmen model does no
speci y he li e s ages om spawned eggs o smol s emig a ing he i e on a e age 4 yea s a e he spawning yea . Ins ead, a Be e on-Hol s ock-
ec ui men model is es ablished o cap u e all he biological p ocesses wi hin his s age o he salmon li e cycle. To ollow he app oach and o
cap u e he ime-delay e ec in he s ock dynamics o ou model, he su i al o he i s ou salmon li e-s ages is se o 1. The o sho e longlining
and i e ishe y en e he popula ion dynamics as cons an age-speci ic mo ali ies (OLL
i
and ec
i
) in he ma ix
A
.
See Appendix Tables A1 and A2.
Table 4
Economic sensi i i y analysis esul s unde MEY. The 75% o PSPC a ge le el is 1.72 million smol s acco ding o he s ock- ec ui men da a om assessmen yea
2013.
Summed discoun ed ne p esen alue
o e ime (M€)
Comme cial annual ha es in numbe o
ish a s eady s a e
Op imal s eady s a e annual
e o in gea days
Annual numbe o smol s a s eady
s a e (in millions)
Salmon wholesale p ices
- 10% / + 10% 9.05 / 15.16 32,065 / 34,893 36,573 / 43,094 1.638 / 1.573
- 20% / + 20% 6.33 / 18.46 29,833 / 35,810 32,373 / 45,682 1.679 / 1.546
- 30% / + 30% 3.92 / 21.9 26,526 / 36,518 27,130 / 47,941 1.725 / 1.522
Uni cos o e o
- 10% / + 10% 13.9 / 10.24 35,007 / 36,918 43,400 / 32,234 1.570 / 1.635
- 20% / + 20% 16.12 / 8.65 36,186 / 30,661 46,849 / 33,861 1.534 / 1.664
- 30% / + 30% 18.48 / 7.22 37,208 / 28,977 50,456 / 30,912 1.496 / 1.692
Discoun a e
- 40% / + 40% 18.42 / 8.48 33,096 / 34,189 38,756 / 41,297 1.617 / 1.591
- 60% / + 60% 23.65 / 7.31 32,764 / 34,412 38,032 / 41,852 1.624 / 1.585
- 80% / + 80% 31.21 / 6.38 32,403 / 34,619 37,268 / 42,378 1.631 / 1.580
M. Holma e al. Ma ine Policy xxx (xxxx) xxx–xxx
6
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Table A.1
Ini ial popula ion size and biological pa ame e s o salmon [25].
Symbol Value Desc ip ion (uni )
si,1
[175,600 175,600 175,600 175,600 1192.5 107.1 59.73 22.375 5.774 2.34] Ini ial s ock a = 1 (1000 ish)
zi
[0 0 0 0 0 0.02 0.5 0.5 0.5 0.5] Sex a io (p op. o emales)
yi
[0 0 0 0 0 0.1627 0.3446 0.537 0.467 1] Ma u a ion (p op. o spawne s)
qi
[0 0 0 0 0 0.00001411 0.00001325 0.00001325 0.00001325 0.000002851] Comme cial ishe y ca chabili y
ei
[0 0 0 0 0 3929 9142 13100 13650 17220] Eggs pe emale
eci
[0 0 0 0 0 0.837067 0.824833 0.824833 0.824833 0.824833] Ri e ishe y escapemen
cwi
[0 0 0 0 0 1.919 6.104 10.999 10.763 12.983] A e age ca ch weigh
a
(kg)
OLLi
[0 0 0 0 0 0.001958 0.11381 0.09637 0.09559 0.1015] Median o sho e longline su i al
53.31 Be e on-Hol Rec ui men pa ame e o yea 2013
0.000376 Be e on-Hol Rec ui men pa ame e o yea 2013
PSPC 2298000 PSPC median o yea 2013
0.75 Ta ge le el o PSPC
mps
0.1253 P opo ional pos -smol su i al (yea
−1
)
m
0.949 P opo ional na u al adul su i al (yea
−1
)
mins
0.052 Ins an aneous na u al adul mo ali y
mseal
8.4427 Ins an aneous seal mo ali y (July & Augus )
mS
+
mins mins
mseal
5
6 6
Ins an aneous na u al mo ali y o spawne s
m74
0.9625 M74 –synd ome su i al
b
(yea
−1
)
a
The a e age ca ch weigh o salmon akes in o accoun he e u ning spawne s, which makes he 4 and 5 sea win e salmon (age classes i= 9 and 10) ela i ely
slimme .
b
M74 synd ome is a ep oduc ion diso de ypical o salmon s ocks in he Bal ic Sea ha causes high mo ali y in ha ched y [29].
Table A.2
Elemen s o he li e his o y ma ix A
.
Elemen Desc ip ion Uni
=FEC e z y e
i i i iqiEob mS eci
,
,
Fecundi y
i{1, ... ,10}
Eggs pe emale
= =SUR j1, 1...3
j ,
Su i al assumed o be 1 o ages 1–3
=
+
SUR
m
s m
4, 74
(4, / 1000) 74
Rec ui men wi h gi en M74 su i al Numbe o smol s
=SUR y m OLL(1 ) ps566
Pos -smol su i al a Bal ic Main Basin Numbe o salmon
= = = +SUR y mOLL g k g(1 ) , 6...10, 1
g kk,
Adul su i al a he Main Basin Numbe o salmon
M. Holma e al.
Ma ine Policy xxx (xxxx) xxx–xxx
7
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