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Depu a ion o geosmin- and 2-me hylisobo neol-induced o - la o s in eci cula ing
aquacul u e sys em (RAS) a med Eu opean whi e ish Co egonus la a e us
© The Au ho (s) 2019
Published e sion
Lindholm-Leh o, P.C.; Vielma, J.; Pakkanen, H.; Alén, R.
Lindholm-Leh o, P.C., Vielma, J., Pakkanen, H., & Alén, R. (2019). Depu a ion o geosmin- and 2-
me hylisobo neol-induced o - la o s in eci cula ing aquacul u e sys em (RAS) a med
Eu opean whi e ish Co egonus la a e us. Jou nal o Food Science and Technology, 56(10), 4585-
4594. h ps://doi.o g/10.1007/s13197-019-03910-7
2019
ORIGINAL ARTICLE
Depu a ion o geosmin- and 2-me hylisobo neol-induced o -
la o s in eci cula ing aquacul u e sys em (RAS) a med
Eu opean whi e ish Co egonus la a e us
P. C. Lindholm-Leh o
1
•J. Vielma
1
•H. Pakkanen
2
•R. Ale
´n
2
Re ised: 18 June 2019 / Accep ed: 1 July 2019
ÓThe Au ho (s) 2019
Abs ac Eu opean whi e ish Co egonus la a e us has
inc easingly become an impo an species o aqua ic ood
p oduc ion, especially in he No dic coun ies. Whi e ish is
p oduced in adi ional cage and pond ope a ions, and in
eci cula ing aquacul u e sys em (RAS) in which, un o -
una ely, o - la o s and odo s, mos ly caused by geosmin
(GSM) and 2-me hylisobo neol (MIB), can accumula e in
ish lesh om he ci cula ing wa e . GSM and MIB ha e
e y low human senso y de ec ion limi s and, he e o e,
o en disliked by consume s e en a low concen a ions. In
his s udy, concen a ions o GSM and MIB in RAS a med
Eu opean whi e ish we e s udied by an analy ical me hod
based on headspace solid phase mic oex ac ion and gas
ch oma og aphy–mass spec ome y. Concen a ions we e
de e mined in di e en pa s o ish: ille , neck, belly, and
ail du ing a depu a ion pe iod and in depu a ion wa e .
The highes ini ial concen a ions we e on a e age
32 ng g
-1
(GSM) and 24 ng g
-1
(MIB) in Eu opean
whi e ish ille and 128 ng L
-1
(GSM) and 94 ng L
-1
(MIB) in wa e , espec i ely. A e a depu a ion pe iod o
16 days, concen a ions dec eased o below he de ec ion
limi s, indica ing he impo ance o he depu a ion pe iod.
Keywo ds Depu a ion Eu opean whi e ish Geosmin 2-
Me hylisobo neol RAS a ming
In oduc ion
Aquacul u e has been a apidly g owing ood p oducing
sec o and nowadays accoun s o mo e han hal o he ish
used o human consump ion (FAO 2016). O - la o -in-
duced ain ing o ish has adi ionally occu ed in ou doo
ponds bu has o en been obse ed also in eci cula ing
sys ems (Houle e al. 2011; Sch ade and Dennis 2005). In
eci cula ing aquacul u e sys ems (RAS), unwan ed o -
la o s wi h unpleasan odo s can accumula e in ci cula ing
wa e and in ish lesh (Ha hu usingha and Da ey 2014;
Houle e al. 2011; Howga e 2004). O - la o s in ish lesh
ha e been widely documen ed o , e.g. a c ic cha
Sal elinus alpinus (Houle e al. 2011), A lan ic salmon
Salmo sala (Bu e al. 2012), ba amundi La es calca i e
(Pe ci al e al. 2008), la gemou h bass Mic op e us sal-
moides, Nile ilapia O eoch omis nilo icus (Yamp ayoon
and Noomho m 2003), and ainbow ou Onco hynchus
mykiss (Robe son e al. 2005). The p esence o o - la o
in ish lesh is pe cei ed as a quali y de ec and o en
disliked by consume s, which can lead o high inancial
losses in p oduce s’ ea nings. O - la o s a e ypically
emo ed by depu a ing he ish in clean wa e . Un o u-
na ely, his o en akes om days o weeks, and can lead
e en o signi ican economic losses due o delays o ha es
and high consump ion o clean wa e (Bu e al. 2012).
O - la o is o en caused by wo sa u a ed bicyclic
e penoids, geosmin (GSM, ans-1,10-dime hyl- ans-9-
decalol) and 2-me hylisobo neol (MIB (1-R-exo)-1,2,7,7-
e ame hyl-bicyclo[2.2.1]hep an-2-ol) (Ge be 1968,
1969), p oducing ea hy and mus y odo and as e. GSM
Elec onic supplemen a y ma e ial The online e sion o his
a icle (h ps://doi.o g/10.1007/s13197-019-03910-7) con ains sup-
plemen a y ma e ial, which is a ailable o au ho ized use s.
&P. C. Lindholm-Leh o
[email p o ec ed]
1
Aqua ic P oduc ion Sys ems, Na u al Resou ces Ins i u e
Finland (Luke), Su on ie 9A, 40500 Jy a
¨skyla
¨, Finland
2
Depa men o Chemis y, Uni e si y o Jy a
¨skyla
¨, Box 35,
40014 Jy a
¨skyla
¨, Finland
123
J Food Sci Technol
h ps://doi.o g/10.1007/s13197-019-03910-7
and MIB a e p oduced as seconda y me aboli es by a
a ie y o bac e ia, including ac inomyce es, cyanobac e ia,
p o eobac e ia and ungi (Dickscha e al. 2005). Typically,
s ep omyces, myxobac e ia, and ac inomyce es a e he
o ganisms esponsible o GSM and MIB p oduc ion in
indoo eci cula ing sys ems (Dickscha e al. 2005). Wa e
phase and he bio il e s ha e been sugges ed as he main
sou ce o GSM-p oduce s in RAS, bu so a , he e is no
consensus on which RAS compa men is dominan in
GSM and MIB p oduc ion (Lukassen e al. 2017).
GSM and MIB a e semi- ola ile compounds wi h oc a-
nol-wa e pa i ion coe icien s 3.57 o GSM and 3.31 o
MIB (Howga e 2004). E en low concen a ions in wa e
can be abso bed by ish and accumula ed in lipid- ich is-
sues (Houle e al. 2011; Howga e 2004), gi ing an
unpleasan as e and odo o wa e (Smi h e al. 2002) and
ish (Howga e 2004). Addi ionally, bo h compounds a e
pe cei ed a e y low concen a ions ( 1ngg
-1
)by
human senses (Da idson e al. 2014; Robe son e al.
2005).
The a con en o ish has an e ec on he la o sen-
sa ion and he senso y h eshold o lipophilic GSM and
MIB (Howga e 2004; Zimba and G imm 2015). Senso y
h esholds o GSM and MIB (muddy and ea hy la o )
inc ease wi h a con en s o ish (D ake e al. 2010;
Howga e 2004), lea ing a highe concen a ion unde ec ed
as he a con en inc eases. Th eshold alues a e used in
senso y analyses and gene ally de ined as he p obabili y o
de ec ion (Ridgway e al. 2010). Acco ding o he de ini-
ion, 50% o popula ion will de ec he ain a ha le el.
Howe e , indi iduals ha e di e en abili ies in de ec ing
as es and odo s and some indi iduals can be mo e sensi-
i e o ce ain compounds.
GSM and MIB a e abso bed in o he ish ia gills, skin
and gas oin es inal ac by lipid- ich issues, gills being
he main pa h o up ake (Howga e 2004). GSM and MIB
a e concen a ed in o he ish lesh un il an equilib ium
s a e is eached be ween he wa e phase and he ish. Thei
concen a ions in wa e and he ime o exposu e a e he
main ac o s a ec ing hose in ish lesh (Howga e 2004),
bu also e.g. ish species, wa e empe a u e, size, and age
o ish a e o impo ance (Pe ci al e al. 2008). The
exchange o chemicals is assumed o p oceed h ough a
passi e p ocess, a ec ed by he lipophilic na u e o he
compounds and he concen a ion in he aqueous pa o
ish (Howga e 2004).
Se e al me hods ha e been s udied and es ed o emo e
o dec ease he o ma ion o GSM and MIB in RAS,
including ozona ion (Powell and Scolding 2018), o he
ad anced oxida ion p ocesses (AOPs) (Ru angwa and
Ve degem 2015), algicides (Ha hu usingha and Da ey
2014), adso p ion, o example, wi h ac i a ed ca bon (Bu
e al. 2012), and zeoli es (Ghasemi e al. 2018). Mo e
ecen ly, me hods based on pho oca alysis, such as modi-
ied TiO
2
wi h sun ligh (Fo iou e al. 2015) and palladium
modi ied ungs en ioxide pho oca alys (Xue e al. 2016)
o deg ade o - la o compounds seem p omising in he
u u e. Howe e , depu a ing wi h clean wa e is so a he
only e icien me hod a ailable o emo e he o - la o s.
Depu a ion can ake om days o weeks, depending on, o
example, he ini ial concen a ions o GSM and MIB, he
species, and he size o ish, bu equi es la ge olumes o
wa e (Bu e al. 2012). Addi ionally, ish a e ypically no
ed du ing he depu a ion o ensu e as good wa e quali y
and e icien depu a ion as possible, which can lead o hei
weigh loss.
Eu opean whi e ish Co egonus la a e us is a whi e- le-
shed eshwa e species which belongs o he amily Sal-
monidae and a genus Co egonus spp. The g oup includes
ma ine, anad omous, and eshwa e species widely dis-
ibu ed in No he n Eu ope, No h Ame ica, and Asia
(Boi eanu e al. 2016). In ecen yea s, Eu opean whi e ish
has inc easingly become an eme ging species o aqua-
cul u al ood p oduc ion in he No dic coun ies. Typically,
whi e ish is consumed as aw pickled, smoked, ille o
o he p oduc s, including ca ia (Se a
¨la
¨2008).
So a , concen a ions in o GSM and MIB in ish lesh
o di e en species ha e been a subjec o limi ed numbe
o s udies. Addi ionally, only ew s udies ha e been con-
duc ed o de ec he loca ion o o - la o accumula ion in
ish (Zimba and G imm 2015). Acco ding o ou knowl-
edge, his is he i s s udy ega ding GSM and MIB con-
cen a ions in Eu opean whi e ish du ing a depu a ion
pe iod. Aim o his esea ch was o ex ensi ely s udy he
loca ion o o - la o accumula ion in ish lesh and he
ime equi ed o su icien depu a ion.
Ma e ials and me hods
Chemicals and ma e ials
S anda d solu ion (T aceCERT
Ò
, 100 lgmL
-1
in MeOH)
o (?/-) GSM and MIB we e pu chased om Me ck.
High-pe o mance liquid ch oma og aphy (HPLC) g ade
me hanol and hexane we e ob ained om J.T Bake and
solid NaCl (pu i y 98%) om Me ck. Ul a-high quali y
(UHQ) wa e om Millipo e (Bed o d, MA, USA) was
used in he analyses. Addi ionally, 10 mL headspace (HS)
glass ials and poly e a luo oe hylene (PTFE) sep um caps
we e pu chased om Me ck.
Manual solid phase mic oex ac ion (SPME) assembly
wi h an ex ac ion ibe coa ed wi h S ableFlex di inyl-
benzene/ca boxene/polydime hyl siloxane (DVB/CAR/
PDMS), 1 cm, 50/30 lm (pa no. 57328-U) in a manual
holde we e pu chased om Supelco (Me ck).
J Food Sci Technol
123
Sampling and p e ea men
P ocess condi ions in RAS
Eu opean whi e ish was aised in a comme cial indoo RAS
a m. The ish we e ed un il he beginning o he depu-
a ion pe iod wi h comme cially p oduced d ied pelle s,
con aining 0.8–1.7% phospho ous and 5.9–8.5% ni ogen
wi h highe concen a ions in ju enile eeds. In gene al, he
main ing edien s o eeds a e ish meal, ish oil, soya,
whea , and apeseed oil, supplemen ed wi h i amins and
ace elemen s. A he a m, a e age biomass o Eu opean
whi e ish was 30 , ed 200 kg eed pe day. In he RAS
p ocess, ammonium was emo ed by ni i ica ion in he
bio- il e , while dissol ed ca bon dioxide was emo ed
om he wa e by packed ae a ion owe . In he ci cula ion
sys em, i e wa e o wa e om a d ill well was used as
he sou ce o he enewal wa e . The ci cula ion wa e was
disin ec ed wi h ozone and UV ligh , pH adjus ed wi h
sodium hyd oxide o sodium bica bona e, and ae a ed
be o e ci cula ing back o anks. Solid o ganic ma e ial was
emo ed wi h a d um il e and phospho ous ma e ial was
p ecipi a ed by using polyaluminum chlo ide and polyme ,
lea ing 2.5% o o al phospho ous. The loccula ed ma e-
ial was led o a band il e o emo e he emaining wa e .
In he beginning o he depu a ion, he ank o 127 m
3
wi h 5500 kg o ish illed wi h ci cula ion wa e was pu
on low h ough. Ri e wa e was led o he depu a ion ank
(3 L s
-1
), displacing he ci cula ion wa e o e ime.
Tempe a u e o he incoming wa e emained unadjus ed,
being nea 0 °C in he win e . The ishes we e no ed
du ing he depu a ion. Fish we e sampled om one depu-
a ion ank du ing one p ocedu e.
Sampling o ish and ci cula ion wa e
Sampling o RAS a med Eu opean whi e ish was pe -
o med a e 1, 3, 7, 10, 13 and 16 days o depu a ion. Fi e
ishes we e aken o each sampling. The ish we e ins an ly
ozen a e sampling and s o ed a -24 °C un il mel ed
and used o he analyses. On a e age, each ish weigh ed
600 g wi h a slaugh e yield o 90.1%. De- ozen ishes
we e ille ed and pieces (15 g ±1 g) o neck, ail, s omach,
and ille as desc ibed by Ha hu usingha and Da ey (2016)
we e collec ed o analysis, consis ing o 5 ish wi h ou
sampling poin s pe ish. Fou pa allel analyses we e pe -
o med o each sample piece (n = 5 94). All analyzed
pa s o ish consis ed o lesh, while isible pieces o non-
edible pa s we e disca ded.
Wa e om he depu a ion ank was aken o analysis
a e 1, 2, 5 and 8 days. Wa e samples we e collec ed in
1 L high-densi y polye hylene (HDPE) bo les and s o ed
ozen a -24 °C be o e he analyses. Pa allel analyses
(n = 4) we e pe o med o each sample.
Lipid con en s
Lipid con en s o each sample piece (neck, ail, belly, and
ille ) o ish a e 1, 3, 7, 10, 13 and 16 days o depu a ion
we e de e mined by Synlab (Synlab, Analy ics and Se -
ices Finland Oy). The acc edi ed me hod (Synlab in e nal
me hod 076) included lyophiliza ion combined wi h acid
hyd olysis o de e mine he lipid con en o he ish lesh.
P e ea men
GSM and MIB we e ex ac ed om he sample ma ix by
headspace solid phase mic oex ac ion (HS-SPME), mod-
i ied om he me hod epo ed by Peng e al. (2014). Fi s ,
1 g o ish lesh o 1 mL o wa e was placed in a 10 mL
HS ial. A sa u a ed NaCl (aq) solu ion was p epa ed and
750 lL added o he ial. The me hod o s anda d addi ion
wi h i e addi ions was used o cons uc calib a ion cu es
o quan i ica ion o GSM and MIB in bo h ish and wa e
samples. Fou eplica es o each sample we e p epa ed and
analyzed o de e mine he s anda d de ia ions.
Sealed sample ials we e placed in a wa e ba h a
60 °C. The sep um o he sample ial was pie ced wi h a
needle and he DVB/CAR/PDMS ibe was exposed in he
headspace o ex ac ion. The ex ac ion ook 30 min
be o e in oducing he ibe di ec ly in o he GC–MS
injec ion po o deso p ion.
Gas ch oma og aphy–mass spec ome y (GC–MS)
An Agilen 6890 se ies/5973N GC/MSD (Palo Al o, CA,
USA) sys em wi h a Phenomenex Zeb on ZB-5MSi (To -
ance, CA, USA) capilla y column (30 m 90.25 mm 9
0.25 lm) was used o sepa a e and de ec he analy es. The
empe a u e o he injec o was adjus ed o 270 °C in he
spli less mode. The ca ie gas was helium a he low a e
o 0.7 mL min
-1
. The empe a u e o he o en s a ed a
45 °C o 3 min and inc eased 30 °C min
-1
o achie e
300 °C ( o al ime 14.5 min). The elec on impac (EI)-MS
condi ions we e selec ed 230 °C o ion sou ce, 5 min
delay ime and ionizing ol age o 70 eV. Selec ed ion
moni o ing (SIM) mode was used o he de ec ion o GSM
and MIB wi h m/z 112, 126, 182 (GSM) and m/z 95, 135,
168 (MIB). Base peak a eas o m/z 95 and 112 we e used
o he quan i ica ion o GSM and MIB.
Me hod alida ion
The analy ical me hod was alida ed in e ms o linea i y,
le el o de ec ion (LOD), le el o quan i ica ion (LOQ),
J Food Sci Technol
123
sensi i i y, p ecision, and epea abili y. Me hod alida ion
was de e mined in e ms o ci cula ion wa e and ish
samples.
Linea i y
Linea i y was s udied by i e s anda d addi ions o GSM
and MIB solu ions o ci cula ion wa e , anging
10–50 ng L
-1
and 20–60 ng g
-1
o ish lesh. Bo h sample
ypes showed adequa e co ela ion coe icien s and linea -
i y: R
2
0.9877 (GSM) and R
2
0.9878 (MIB) o ci cula ion
wa e and R
2
0.9862 (GSM) and R
2
0.9883 (MIB) o ish
lesh.
Sensi i i y, le els o de ec ion, and quan i ica ion
Fo he ch oma og aphic analysis o GSM and MIB, LOD
and LOQ we e de e mined based on signal- o-noise a io
(S/N) = 3 o LOD and S/N = 10 o LOQ in he SIM mode.
The esul s o wa e and ish samples a e lis ed in Table 1.
Addi ionally, sensi i i ies we e calcula ed and also lis ed in
Table 1.
P ecision and epea abili y
Yields o s anda d addi ion o GSM and MIB s anda ds a e
lis ed in Table 2. Yields ha e been calcula ed bo h o
ci cula ion wa e and whi e ish lesh. Addi ions ha e been
conduc ed wi h i e eplica i e measu emen s (n = 5) and
based on hem, calcula ed he s anda d de ia ions (SDs).
Depu a ion model
Modelling he depu a ion o Eu opean whi e ish in gene al
and he dec ease o GSM and MIB in RAS sys em was
pe o med as epo ed by Sch am e al. (2017). The model
was p epa ed o show he decline o GSM and MIB in
ela ion o e.g. ish biomass, wa e low a e, ank olume,
and le els in he wa e . Based on his, he elimina ion a e
cons an s we e de e mined o Eu opean whi e ish, which
a e gene ic, bu s ill speci ic o he size, lipid con en and
empe a u e. Equa ion 1desc ibes he dec ease o o - la-
o concen a ions in ish in clean wa e , assuming negli-
gible accumula ion o chemicals in he wa e .
CBð Þ¼CBð ¼0Þeðk2 Þð1Þ
C
B( = 0)
is he ini ial concen a ion o GSM o MIB in ish
in he beginning o he depu a ion pe iod, he ime o
depu a ion in hou s, k
2
elimina ion a e cons an o GSM o
MIB o he wa e , and C
B( )
he concen a ion o GSM o
MIB in ish as a unc ion o ime.
Ra e cons an k
2
is calcula ed o each body pa ( ille ,
neck, belly, and ail) by he non-linea eg ession analysis
based on he dec ease o concen a ions and he depu a ion
ime by Sys a 13.1 (SYSTAT So wa e, Inc. 2009). By
inse ing he k
2
alues in Eq. 1and ecalcula ing pe d y
lipid con en s, ln- ans o med concen a ions we e ob ained
o each body pa .
Resul s and discussion
GSM and MIB in whi e ish
Concen a ions o GSM and MIB in Eu opean whi e ish
ille anged om 0 o 32 ng g
-1
, dec easing du ing he
16 days o depu a ion (Fig. 1). Be o e he depu a ion pe -
iod, concen a ions we e ai ly high compa ed o
0.2–0.9 ng g
-1
o MIB and 0.10–0.115 ng g
-1
o GSM in
A lan ic salmon (S. sala ) epo ed by Da idson e al.
(2014). Ha hu usingha and Da ey (2016) s udied ba a-
mundi (L. calca i e ) in a ci cula ion sys em wi h 6% (w/
w) body a and ound 0.01–7 ng g
-1
GSM and
0.01–7 ng g
-1
MIB. On he o he hand, highe concen a-
ions o GSM and MIB ha e been epo ed by Zimba e al.
(2012). They ound 4.8–19.7 ng g
-1
MIB and
0.27–0.59 ng g
-1
GSM in RAS a med ainbow ou (O.
mykiss). Sch am e al. (2017) s udied depu a ion o Eu o-
pean eel (Anguilla anguilla) wi h 33.7% (w/w) a con en
and ound high concen a ions o GSM (22 ng g
-1
) be o e
he depu a ion. The esul s we e in he same ange wi h
hose o his s udy.
The o e all a con en o Eu opean whi e ish wi h
a e age size o 600 g was ela i ely high, bu dec eased
o e he ime o depu a ion (Table 3). Howe e , i is in he
same ange wi h ha (11.1%) epo ed by Boi eanu e al.
(2016) o a med C. ma aena, weigh ing 290–380 g.
Kause e al. (2011) ound 12.2% lipid con en in Eu opean
Table 1 Le el o de ec ion
(LOD), le el o quan i ica ion
(LOQ), and sensi i i y o
Eu opean whi e ish (ng g
-1
),
and ci cula ion wa e samples
(ng L
-1
)
Sample ype Compound LOD LOQ Sensi i i y
Eu opean whi e ish Co egonus la a e us GSM, ng g
-1
1.4 2.1 5.5
MIB, ng g
-1
0.5 1.5 0.9
Ci cula ion wa e GSM, ng L
-1
2.1 2.8 2.3
MIB, ng L
-1
0.8 1.6 1.2
GSM—Geosmin, MIB—2-me hylisobo neol
J Food Sci Technol
123

Table 2 Yields o s anda d addi ion o GSM and MIB o ci cula ion wa e (10–50 ng L
-1
addi ion) and o Eu opean whi e ish lesh
(20–60 ng g
-1
addi ion) wi h ela i e s anda d de ia ions (±RSD)
GSM (in wa e ) MIB (in wa e ) GSM (in whi e ish) MIB (in whi e ish)
S anda d
addi ion
(ng L
-1
)
Yield (%) S anda d
addi ion
(ng L
-1
)
Yield (%) S anda d
addi ion
(ng g
-1
)
Yield (%) S anda d
addi ion
(ng g
-1
)
Yield (%)
10 94.5 ±2.8 10 96.0 ±2.6 20 101.1 ±3.5 20 101.7 ±3.6
20 94.1 ±2.7 20 105.7 ±2.1 30 97.6 ±2.9 30 103.2 ±3.0
30 99.4 ±2.9 30 103.1 ±1.3 40 96.3 ±3.1 40 100.1 ±3.2
40 96.9 ±3.5 40 104.8 ±2.8 50 103.8 ±3.4 50 105.6 ±2.9
50 98.6 ±2.0 50 95.6 ±2.2 60 103.7 ±3.0 60 103.2 ±3.3
GSM—Geosmin, MIB—2-me hylisobo neol
Fig. 1 Concen a ions o GSM
(a) and MIB (b) in ille , neck,
belly, and ail o Eu opean
whi e ish lesh du ing he
depu a ion o 16 days (±SD)
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whi e ish, anging in size 540–710 g, while Ai aksinen and
Riihima
¨ki (2014) epo ed lipid con en s o abou 9% o
a med whi e ish C. la a e us wi h ha es weigh o 995 g.
The lipid con en a e 10 days in depu a ion show sudden
inc ease in all body pa s o ish, al hough he lipid con en
in o al shows up o 50% dec ease du ing he ime o
depu a ion. This can be due o a ia ion in ish size a
di e en sampling poin s, suppo ed by he inc eased limi s
o e o a ha poin .
The di e ences in a con en s we e pa ly explained by
he size o ish. Howe e , o he ac o s also ha e an e ec
on he a con en . Suomela e al. (2017) showed ha he
ype o eed has a s ong in luence on he o al lipid con en
o Eu opean whi e ish and on he a y acid p o ile o ish.
Addi ionally, cul u e condi ions a ec he a y acid com-
posi ion as well as wa e empe a u e, becoming mo e
unsa u a ed in colde wa e (Haa d 1992).
The highes concen a ions o GSM we e de ec ed in
ille and belly and o MIB in ille and neck. In all pa s o
ish, concen a ions dec eased o e he depu a ion pe iod
(Fig. 1). So a , he e a e only ew s udies a ailable
ega ding o - la o s and a con en s in di e en pa s o
ish. Ha hu usingha and Da ey (2016) ound he highes
lipid con en in he belly and he lowes in he ail pa o
ba amundi. Howe e , hey did no de e mine concen a-
ions o o - la o s in di e en pa s o ish. Pe ci al e al.
(2008) s a ed ha GSM and MIB we e no homogeneously
dis ibu ed in he ish bu based on lipid concen a ions,
while Pe e sen e al. (2011) ound no co ela ion be ween
a con en and concen a ions o GSM and MIB, only a
posi i e co ela ion wi h he ish size. Pe ci al e al. (2008)
also s a ed ha highe le els de ec ed in la ge ish is mos
likely caused by he highe lipid con en o la ge ish. In
his s udy, he esul s indica ed lowe concen a ions o
MIB in he belly, he pa wi h ypically highe lipid con-
en s compa ed o ille and ail. In he case o GSM, he
highes concen a ions we e de ec ed in ille and belly, and
somewha lowe in he neck and ail. Howe e , he e we e
no signi ican di e ences be ween he a e age alues o
di e en body pa s. I is possible, ha GSM and MIB as
lipophilic compounds we e mos ly concen a ed in he a y
issue. Only he edible lesh pa s we e s udied and he a y
pa s disca ded which migh ha e led o lowe de ec ed
concen a ions. On he o he hand, his could be due o
di e en species o ish and la ge size (Pe ci al e al.
2008).
The concen a ions o GSM we e mos ly below he
de ec ion limi s a e 13 days o depu a ion (Fig. 1), while
in he s udy o Robe son e al. (2005), he concen a ions
dec eased apidly a i s (24 h) and hen slowe du ing he
es o he o al 168 h o depu a ion. In he case o GSM,
howe e , he e is a mo e p onounced dec ease in concen-
a ions a e he i s 7 days (Fig. 1). On he o he hand,
Da idson e al. (2014) epo ed a slow dec ease in MIB
concen a ion du ing he i s 6 days and an inc eased a e
o dec ease owa ds 10 days o depu a ion. The depu a ion
pe o mance and ime o depu a ion depend on se e al
ac o s, such as ini ial o - la o concen a ion in ish,
wa e empe a u e, ish densi y, wa e enewal a e, and he
o - la o concen a ion in he depu a ion sys em supply
wa e (D ake e al. 2010; Howga e 2004), leading o
a ying a es o depu a ion.
The lowes ini ial le els o MIB we e ound in he belly,
e en hough i con ained he highes amoun o a . This
may be explained by he ac ha he lipophilic GSM and
MIB ind hei ways especially in o he a issue, while
bo h lesh and a we e chosen o he chemical analysis.
Howe e , he a e o emo al in he belly was simila o
hose in ille , neck, and ail.
The a e cons an k
2
o he dec ease o MIB was
0.007 h
-1
o neck, 0.007 h
-1
o belly, 0.005 h
-1
o il-
le , and 0.008 h
-1
o ail. In he case o GSM, he a e
cons an k
2
was 0.008 h
-1
o neck, 0.008 h
-1
o belly,
0.008 h
-1
o ille , and 0.007 h
-1
o ail. These we e
somewha lowe han he a e cons an k
2
0.014 h
-1
epo ed by Sch am e al. (2017), desc ibing mo e e icien
depu a ion. This is consis en wi h he slow change o
ci cula ing wa e o clean wa e in he beginning o he
depu a ion.
The dec ease o GSM and MIB concen a ions o e he
ime o depu a ion o each body pa has been p esen ed
Fig. 2(ln GSM ng g
-1
lipid). Fi s , he a e cons an k
2
was
calcula ed o ille , neck, belly, and ail o bo h GSM and
MIB (Supplemen a y ile S1), which we e used in
Table 3 Lipid con en s (w/w,
±limi o e o , %) o Eu opean
whi e ish Co egonus la a e us
a e 1, 3, 7, 10, 13 and 16 days
o depu a ion
Depu a ion ime,
days
Lipid con en pe d y lesh (%)
Neck Fille Belly Tail
1 24.9 ±2.5 15.4 ±1.5 30.1 ±3.0 19.5 ±2.0
3 18.0 ±1.8 11.7 ±1.1 15.6 ±1.6 15.6 ±1.6
7 17.5 ±1.8 11.4 ±1.1 17.0 ±1.7 10.1 ±1.0
10 21.2 ±2.1 13.8 ±1.4 22.7 ±2.3 12.2 ±1.2
13 13.0 ±1.3 9.8 ±1.0 17.3 ±1.7 9.3 ±1.9
16 12.8 ±1.3 9.4 ±1.9 13.3 ±1.3 9.7 ±1.0
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ecalcula ing he decease pe lipid con en . The a e o
emo al in di e en body pa s p oceeds a simila a es.
The ini ial concen a ions in ille we e highe han in he
o he body pa s, despi e he ac ha he highes lipid
con en s we e ini ially ound in he belly and neck
(Table 3). The esul s also show ha e en a e 16 days o
depu a ion, in some cases, low le els o o - la o com-
pounds emained in he ish lesh.
GSM and MIB in wa e
Concen a ions in wa e dec eased du ing he depu a ion
ime, as shown in Fig. 3. This is in ag eemen wi h he ac
ha a his pa icula a m, he ci cula ion wa e was
g adually changed o clean wa e du ing he ime o
depu a ion. In he beginning, he concen a ions we e ai ly
high, on a e age 128 ng L
-1
o GSM and 94 ng L
-1
o
MIB. The esul s can be conside ed ypical o ci cula ion
wa e o a RAS a m, e en hough he concen a ions a y
widely among RAS a ms based on ope a ional choices,
p ocess condi ions, and wa e quali y (Ha hu usingha and
Da ey 2016).
GSM and MIB a e assumed o be exchanged be ween
wa e and ish by passi e di usion ia he gills. The
depu a ion p ocess, d i en by he ugaci y and chemical
po en ial, seeks equilib ium be ween he lipid ac ions o
ish and wa e , eaching equilib ium as he ugaci ies in
lipids and wa e a e equal (Howga e 2004). E en hough
Fig. 2 Ln ans o med GSM
(a) and MIB (b) concen a ions
in ille , neck, belly, and ail o
Eu opean whi e ish (ng g
-1
lipid) as a unc ion o
depu a ion ime, 1–16 days (h).
Dashed line desc ibes he
concen a ion o de ec ion limi s
o GSM o MIB based on
senso y and analy ical me hods
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GSM and MIB we e exc e ed om he ish du ing he
depu a ion pe iod, he olume o wa e is e y la ge
compa ed o inc ease in GSM and MIB le els and ypi-
cally, no ne inc ease in hei concen a ions could be
de ec ed (Sch am e al. 2017). Howe e , e y high ish
densi ies and low wa e exchange a es can lead o
inc eased le els o compounds exc e ed by he ish
(Sch am e al. 2009). In his s udy, he ish load du ing he
depu a ion was a abou 43 kg m
-3
. The esul s showed a
dec ease in concen a ions o GSM and MIB bo h in ish
and wa e (Figs. 1and 3), sugges ing an adequa e olume
o pu e wa e o he depu a ion p ocedu e. The concen-
a ions de ec ed in he depu a ion wa e mos ly o igina ed
om he ci cula ion wa e used o ill he depu a ion ank a
he beginning o he depu a ion pe iod, and GSM and MIB
eleased by he ish. Addi ionally, bio ans o ma ion o
GSM and MIB o hei deg ada ion p oduc s migh occu
(Sch am e al. 2018).
Conclusion
This s udy is he i s o epo GSM and MIB concen a-
ions in Eu opean whi e ish lesh and hei dis ibu ion in
di e en pa s o ish. The le els ound in Eu opean
whi e ish we e likely caused by he high le els in ci cula-
ion wa e and accumula ion in o he ish. In he u u e,
s udies ega ding he accumula ion in di e en species
unde simila condi ions can gi e mo e insigh .
The gene al depu a ion model was buil o p edic he
emo al o o - la o s om Eu opean whi e ish mo e
gene ally, wi h he e ec s o p ocess condi ions o his
pa icula plan in mino pa . The esul s show he g ea
e ec o a con en in Eu opean whi e ish lesh. The
dec ease p oceeds ai ly simila ly in all body pa s, e en
hough he ini ial concen a ions we e di e en . Addi ion-
ally, he a con en s dec eased up o 50% om hei
o iginal alues du ing he depu a ion, showing he e ec o
as ing.
The esul s show ha depu a ion up o 16 days is
equi ed o MIB, bu o GSM sho e ime seems su i-
cien . In his s udy, ci cula ion wa e was g adually chan-
ged o esh wa e du ing he depu a ion pe iod, inc easing
he ime equi ed o ull emo al o o - la o s. Op i-
miza ion o he depu a ion ime is c ucial in o de o educe
he p oduc ion cos s bu s ill p oduce he high quali y ish
p oduc s. The impo ance o depu a ion is emphasized
pa icula ly, when p oducing mild- la o ed Eu opean
whi e ish which mus no p o ide any o - la o sensa ion,
no e en o he mos sensi i e consume .
Acknowledgemen Open access unding p o ided by Na u al
Resou ces Ins i u e Finland (LUKE). Financial suppo by he Eu o-
pean Ma i ime and Fishe ies Fund is g a e ully acknowledged.
Au ho con ibu ions The expe imen was planned by JV and PCL-
L. HP was consul ed ega ding he me hod de elopmen and he
analy ical wo k. PCL-L conduc ed he sample p epa a ion, analyses,
and d a ed he manusc ip . RA, HP and JV c i ically examined and
e ised he manusc ip .
Con lic o in e es The au ho s decla e ha hey ha e no con lic s o
in e es .
Fig. 3 Concen a ions o GSM
and MIB in depu a ion ank
du ing 1, 2, 5 and 8 days, n = 4
(±SD)
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