Gene ic e ec s o suppo i e s ockings on na i e pikepe ch
popula ions in bo eal lakes – h ee cases, h ee di e en ou comes
MATTI SALMINEN 1 , MARJA-LIISA KOLJONEN 1 , MARJATTA S Ä IS Ä 2 and JUKKA RUUHIJ Ä RVI 3
1 Finnish Game and Fishe ies Resea ch Ins i u e, Helsinki, Finland
2 Depa men o Ag icul u al Sciences, Uni e si y o Helsinki, Helsinki, Finland
3 Finnish Game and Fishe ies Resea ch Ins i u e, E o, Finland
Salminen, M., Koljonen, M.-L., S ä is ä , M. and Ruuhij ä i, J. 2011 . Gene ic e ec s o suppo i e s ockings on na i e pikepe ch
popula ions in bo eal lakes – h ee cases, h ee di e en ou comes. – He edi as 149 : 1–15. Lund, Sweden. eISSN 1601-5223.
Recei ed 27 May 2011. Accep ed 20 Sep embe 2011.
The gene ic consequences and gene l ow o pikepe ch ( Sande luciope ca ) s ocking we e assessed in h ee bo eal lakes based on
admix u e model analysis and compa ison o he p e- and pos - elease pa e ns o gene ic a iabili y a 9 DNA mic osa elli e loci in
he ecipien popula ions. In wo ou o he h ee cases, he eleases o i sh om o eign popula ions caused signi i can changes in
he gene ic s uc u e o he ecipien popula ion. The la ges changes we e obse ed in Lake Ouluj ä i, whe e he pos - elease sam-
ple was almos iden ical o he eleased Lake Vanajanselk ä popula ion, and abou 90% o he ca ch was composed o he eleased
popula ion. The gene ic composi ion o Lake Lohjanj ä i pikepe ch also shi ed ma kedly owa ds ha o he eleased Lake Vana-
janselk ä popula ion, and abou hal o he la e ca ch was o eleased Vanajanselk ä o igin. In Lake Vanajanselk ä , in con as , eleases
o pikepe ch om lakes Painio and A e ia had only a small impac on he gene ic s uc u e o he pikepe ch popula ion. These esul s
indica e ha he cu en s ocking p ac ices c ea e an e ec i e a i i cial gene l ow ha may s ongly shape and educe he gene ic
di e en ia ion among he emaining na i e pikepe ch popula ions. A common ea u e o all h ee cases was he lack o p io app aisal
o he po en ial gene ic and ecological isks in ela ion o he expec ed bene i s o he elease p og ammes.
Ma i Salminen, Finnish Game and Fishe ies Resea ch Ins i u e, PO Box 2, FIN-00791 Helsinki, Finland. E-mail: ma i.salminen@
k l. i
The na i e dis ibu ion o pikepe ch ( Sande luciope ca )
in no he n Eu ope is assumed o be ela ed o he Lake
Ancylus ( eshwa e ) s age o he p esen Bal ic Sea
(L Ö NNBERG 1899; LEHTONEN e al. 1996), which ca 9200 –
9000 BP (B J Ö RCK 1995) p o ided he species a dis ibu-
ion pa h o a eas co e ed by he o me lake, up o
100 – 150 m abo e he p esen wa e le el o he Bal ic Sea.
Since he ini ial coloniza ion, adap i e selec ion, gene
l ow and d i ha e shaped he pa e ns o gene ic di e si y
wi hin he species, esul ing in a ela i ely high le el o
gene ic a iabili y (B J Ö RKLUND e al. 2007; S Ä IS Ä e al.
2010) compa able o ha epo ed in Scandina ian whi e-
i sh ( Co egonus la a e us, S Ä IS Ä e al. 2008), g ayling
( Thymallus hymallus, K OSKINEN e al. 2000), pe ch ( Pe ca
l u ia ilis , NESB Ø e al. 1999) and A lan ic salmon popula-
ions ( Salmo sala , S Ä IS Ä e al. 2005).
Since he la e 1800s, he dis ibu ion and gene ic di e -
si y o pikepe ch has also been shaped by human-in l u-
enced gene l ow h ough in oduc ions and ha che y
eleases. In Denma k, he i s in oduc ion ook place in
1898, and since hen pikepe ch ha e been es ablished in
o e 70 wa e bodies ( DAHL 1982). In Sweden, No way and
Finland he pikepe ch is a na i e species, bu has also been
he mos commonly in oduced non-salmonid i sh ( TAMMI
e al. 2003). In Finland, he pikepe ch is na i e in ca 650
lakes, bu due o in oduc ions, he p esen dis ibu ion
includes ca 2300 lakes ( LAPPALAINEN and TAMMI 1999).
The expansion o pikepe ch has been exclusi ely ega ded
as a posi i e phenomenon, unlike in Tu key, he UK and
Denma k, o ins ance, whe e he expansion has in some
cases in ol ed undesi able ecological e ec s ( CRIVELLI
1995; COWX e al. 1997; JEPSEN e al. 2000).
Un il he mid-1900s, in oduc ions in Finland we e
mos ly ca ied ou using epea ed ans e s o adul i sh o
e ilized eggs ( HALME 1961, 1962), a me hod ha seems o
ha e been qui e e ec i e in ans e ing gene ic ma e ial
( S Ä IS Ä e al. 2010). Some o he mos i al na u ally ep o-
ducing pikepe ch popula ions in Finland s em om hese
ea ly in oduc ions, including wo majo sou ce s ocks o
cu en ha che y p oduc ion. Apa om he s ocking p es-
su e (no. o s ocking e en s and indi iduals eleased; KOLAR
and LODGE 2001) and he ai s o he species, he success o
he ea ly in oduc ions may ela e o he a ailabili y o
a ou able habi a s a al i udes abo e he Lake Ancylus
wa e le el, and o he ac ha he sou ce s ocks we e usu-
ally loca ed close o he ecipien lakes. In he Rh ô ne del a
o F ance, he in asi e success o pikepe ch has simila ly
been explained by he ai s o he species and he s ocking
p essu e, main aining a high le el o gene ic a iabili y in
he in oduced popula ions ( POULET e al. 2008).
A new e a o pikepe ch s ocking was ca alyzed by he
collapse o se e al impo an pikepe ch s ocks du ing he
He edi as 149: 1–15 (2012)
© 2012 The Au ho s. This is an Open Access a icle. DOI: 10.1111/j.1601-5223.2011.002230.x
2 M. Salminen e al. He edi as 149 (2012)
1960s and ea ly 1970s ( COLBY and LEHTONEN 1994). The
managemen s a egy de ised in his si ua ion was based
on he s ocking o young-o - he-yea (YOY) pikepe ch.
Mo e e i cien ea ing me hods we e de eloped ( RUUHI-
J Ä RVI and HYV Ä RINEN 1996), inc easing he p oduc ion o
YOY pikepe ch o ca 10 million yea
⫺1 ( ANON . 2004). The
p oduc ion was mainly di ec ed o new in oduc ions and
e-s ocking p ojec s aiming a e-es ablishing los pike-
pe ch popula ions. In ecen yea s, he i sh ha e mainly
been used in a ious enhancemen p ojec s aimed a he
mi iga ion o ep oduc ion ailu es o he e ec s o o e -
i shing, o simply a imp o ing i shing possibili ies.
The popula i y o enhancemen p og ammes has aised
ques ions abou hei sus ainabili y. Despi e he high cos s o
he p og ammes, hei economic bene i s ha e o en no been
p ope ly e alua ed. S ocking also has been a emp ing solu-
ion in many cases, as i educes he need o s ic i shing
egula ion. The main conce n, howe e , is he po en ial
ad e se e ec o eleases o o eign gene ic ma e ial on he
gene ic di e si y and adap abili y o he species as a whole.
Due o insu i cien con ol and planning, p ac ically all s ock-
ing p og ammes in Finland ha e elied on h ee o ou sou ce
s ocks, all o hem wi h a sou he n o igin. The possibly small
e ec i e popula ion size o he b oods ocks used has also
aised conce ns, as i causes loss o di e si y ( RYMAN and
L AIKRE 1991). Du ing he las wo decades, p ac ically all
emaining indigenous eshwa e pikepe ch s ocks a e likely
o ha e been subjec ed o he l ow o o eign sou he n genes
h ough ha che ies. The gene ic e ec s o eleases such as
compe i ion be ween na i e and in oduced species o s ocks,
he eplacemen o na i e s ocks, mixing o s ocks and ex inc-
ion o na i e s ocks ha e been widely discussed ( COWX e al.
1997).
In his s udy, we assessed he gene ic consequences o
pikepe ch s ockings o indigenous na i e popula ions in
h ee bo eal lakes in Finland: Lake Lohjanj ä i, Lake
Vanajanselk ä and Lake Ouluj ä i. Gene ic in o ma ion
was a ailable om he h ee ecipien pikepe ch popula-
ions be o e eleases, om he h ee eleased ha che y
popula ions and also he admixed popula ions in each lake
a e he eleases, allowing us o assess he p opo ion o
new gene ic ma e ial in he na i e popula ions a e he
eleases. Finally, o add ess he o e all sus ainabili y o
cu en s ocking p ac ices, we con as ed he obse ed
gene ic e ec s o he h ee s ocking p og ammes wi h
hei expec ed socioeconomic bene i s.
MATERIAL AND METHODS
S udy lakes
Lake Lohjanj ä i
The indigenous pikepe ch is ec ea ionally and econom-
ically one o he mos impo an i sh species in Lake
Lohjanj ä i (a ea 89 km
2 , mean dep h 13 m), sou he n
Finland (Fig. 1). In mail su eys, epo ed pikepe ch
ca ches om 1981 – 2002 a ied om 4 – 21 ons yea
⫺1
( SALMINEN and RUUHIJ Ä RVI 2004). Abou 90% o he
ca ches ha e been aken by gillne s, while olling
accoun s o 10% o he o al yield. The ca ches a e
mainly used o household needs, bu some i she men
also sell i sh.
L EHTONEN and MIINA (1988) epo ed high i shing mo -
ali y and a low age a ec ui men (4 – 6 yea s) o Lake
Lohjanj ä i pikepe ch. G ow h o e - i shing was ega ded
as e iden and ec ui men o e - i shing possible. A la ge
gill-ne mesh size (50 – 55 mm, ba leng h) and a la ge
minimum landing size (MLS; 40 – 42 cm) we e sugges ed
and in 1992 also implemen ed o inc ease he age a
ec ui men . Releases o YOY pikepe ch we e also
expanded o inc ease and s abilize ca ches, and in he
1990s hey eached he le el o 100 000 indi iduals yea
⫺1
(ca 11 ind. ha
⫺1 , Fig. 2).
N
0100 km
ESRI 1999
©
Oulujä i
Lohjanjä i
Vanajanselkä
A e ia
Painio
Ki ijä i
Kemijä i
FINLAND
Fig. 1. The loca ion o he h ee s udy lakes (blue do s; Lakes
Lohjanj ä i, Vanajanselk ä and Ouluj ä i) and he h ee pike-
pe ch popula ions addi ionally used in he eleases (g een do s;
Lakes A e ia, Painio and Ki ij ä i). The pikepe ch popula ion
o Lake Kemij ä i (yellow do ) was used as an ou g oup in he
gene ic dis ance analyses.
He edi as 149 (2012) Gene ic e ec s o suppo i e s ockings on pikepe ch 3
Lake Lohjanjä i
0
20 000
40 000
60 000
80 000
100 000
120 000
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
B2: 1998-2002B1: 1991-1995
Lake Vanajanselkä
0
10 000
20 000
30 000
40 000
50 000
60 000
70 000
80 000
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
A: 1984-1986 B: 1998-2002
Lake Oulujä i
0
100 000
200 000
300 000
400 000
500 000
600 000
700 000
800 000
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
A e ia Vanajanselkä Painio
A: 1936-1943, 1961-1968 B2: 2001B1: 1990-1992
A: 1979-1981
Fig. 2. Releases o YOY pikepe ch acco ding o he yea -class
(1979 – 2003) and sou ce s ock in Lake Lohjanj ä i, Lake Vana-
janselk ä and Lake Ouluj ä i. A ows indica e he yea -classes o
p e- (A) and pos -s ocking (B) samples (Table 1).
Lake Vanajanselk ä
Lake Vanajanselk ä is he la ges lake (103 km
2 , mean
dep h 8 m) o he Vanaja esi wa e cou se in he Ri e
Kokem ä enjoki basin. The ela i ely s ong and s able
indigenous pikepe ch popula ion ( TOIVONEN e al. 1981)
suppo s impo an pikepe ch i she ies and has also se ed
as a sou ce o ea ly ans e s o adul i sh and eggs ( HALME
1961, 1962; RUUHIJ Ä RVI and SALMINEN 1992), and since he
1980s also o la ge-scale YOY p oduc ion ( RUUHIJ Ä RVI
and HYV Ä RINEN 1996). Pikepe ch ca ches o ec ea ional
i she men ha e ecen ly been ca 20 ons yea
⫺1 . Se en
p o essional i she men (in 2006, Pekka Ko honen pe s.
comm.) also i sh pikepe ch in he lake, hei ca ch being
5 – 10 ons yea ⫺1 .
Gill-ne ing wi h mainly 45 mm ne s accoun s o ca
90% o he pikepe ch ca ch, he es being caugh mainly
by olle s ( KIVINEN 2009). Despi e he good g ow h a e
o Lake Vanajanselk ä pikepe ch, he ecommended ises
in he minimum landing size (p esen 37 cm) and gill-ne
mesh size ha e no been implemen ed. Ins ead, enhance-
men eleases ha e been ca ied ou (Fig. 2), despi e he
good ec ui men o he na i e popula ion.
Lake Ouluj ä i
Un il he la e 1950s, Lake Ouluj ä i (a ea 928 km
2 , mean
dep h 7.6 m) pikepe ch sus ained a l ou ishing i she y,
wi h ca ches amoun ing o 100 – 150 ons yea
⫺1 ( SUTELA
and HYV Ä RINEN 2002). The ea e , ca ches began o decline
and he bo om, less han 100 kg yea
⫺1 , was eached in
he ea ly 1980s. In he 1990s, ca ches began o eco e and
ha e ecen ly been a ound 100 ons yea
⫺1 . Pikepe ch a e
mainly aken by ec ea ional gill-ne e s and angle s, bu
also p o ide an impo an a ge o he 32 p o essional
i she men ope a ing in he lake (in 2006, Pekka Ko honen
pe s. comm.).
Po en ial causes o he collapse o he pikepe ch s ock
and ca ches in Lake Ouluj ä i, as in nume ous o he bo eal
lakes, we e he declining empe a u es in 1940 – 1970 com-
bined wi h inc easing exploi a ion caused by he shi
om co on o mo e e i cien nylon mono i lamen gill-
ne s ( COLBY and LEHTONEN 1994). Enhancemen s ocking
was he main managemen ac ion ecommended in his
si ua ion ( SALOJ Ä RVI e al. 1981), and based on his ecom-
menda ion eleases we e s a ed in 1985, eaching he
le el o 500 000 indi iduals yea
⫺1 in he 2000s (Fig. 2,
ca 5 ind. ha
⫺1 ).
The p oduc ion and eleases o ha che y pikepe ch
The p oduc ion o YOY pikepe ch elies on he annual
cap u e o wild spawne s om he spawning a eas using
ap-ne s ( SALMINEN and RUUHIJ Ä RVI 1991; RUUHIJ Ä RVI and
H YV Ä RINEN 1996). A e ha ching he la ae a e s ocked a
20 000 – 40 000 ind. ha
⫺1 in o 1 – 2 ha dams p oducing na u-
al ood. The a e age ha es in la e Augus – Sep embe ,
i.e. a e 3 – 4 mon hs o ea ing, is abou 10 000 YOY pike-
pe ch ha
⫺1 , anging in o al leng h om 60 – 80 mm.
As he backg ound o YOY pikepe ch has no been an
issue among he manage s, he p oduc ion o la ae has
concen a ed on a limi ed numbe o dense sou ce popula-
ions, all wi h a sou he n o igin. Ano he ac o po en ially
in l uencing he gene ic consequences o eleases is amily
size, i.e. he numbe o ju eniles p oduced pe emale.
Gi en he high ecundi y in a i i cial ea ing ( SALMINEN
e al. 1992) and high su i al du ing ea ing, one la ge
emale may p oduce up o 200 000 ju eniles, which may
4 M. Salminen e al. He edi as 149 (2012)
493 (0.5 – 3.0 kg) adul i sh om Lake Vanajanselk ä
(Fig. 3, Table 1) ( SUTELA e al. 1995).
Pikepe ch samples
The analysis o gene ic impac s was based on admix u e
modelling and he compa ison o gene ic a iabili y wi hin
he h ee ecipien popula ions in Lakes Lohjanj ä i, Vana-
janselk ä and Ouluj ä i, be o e and a e s ocking. F om all
h ee lakes, one p e-s ocking sample and one o wo (in Lake
Ouluj ä i) pos - elease admix u e samples we e analyzed
(Table 1). The h ee pikepe ch popula ions addi ionally used
in he eleases ( om lakes A e ia, Painio and Ki ij ä i) we e
also sampled o he DNA analyses. The pikepe ch popula-
ion o Lake Kemij ä i was used as an ou g oup in he
gene ic dis ance analyses ( S
Ä IS Ä e al. 2010).
In he case o Lohjanj ä i i was possible o o ganize an
addi ional es , independen o he gene ic da a, as he
ju eniles ( om Lake A e ia and Lake Vanajanselk ä )
eleased he e in 1991 – 1995 we e ma ked using ho -
b anding ( SAURA 1996; SALMINEN and RUUHIJ Ä RVI 2004),
allowing he iden i i ca ion o hei s ock o o igin (Table
1, Fig. 2). Thei s ock-speci i c p opo ions we e eco ded
among adul pikepe ch sampled in 1994 – 2000.
hen cons i u e a la ge pa o o e en he whole yea -class
s ocked in one o wo la ge o se e al smalle lakes. To p e-
en his, ha che ies ha e been ad ised o mix he o sp ing
o emales ha spawn a app oxima ely he same ime, bu i
is no known o wha ex en his ac ually happens.
Ou h ee s udy lakes o e ypical examples o he
complex ans e s o pikepe ch om one wa e -body o
ano he :
1) In Lake Lohjanj ä i, h ee o eign popula ions we e
used in he eleases (Fig. 3, Table 1). Two o hem
(Lake A e ia and Lake Painio) a e gene ically close
o Lake Lohjanj ä i pikepe ch ( S Ä IS Ä e al. 2010), as
hey ha e hei oo s in ea ly (1930s) ans e s om
he same Lake Lohjanj ä i, while he hi d sou ce
popula ion (Lake Vanajanselk ä ) is gene ically mo e
dis an ( S Ä IS Ä e al. 2010).
2) In Lake Vanajanselk ä , bo h i s own indigenous popula-
ion, and he popula ions o Lake A e ia and Lake
Painio ha e been used in he eleases (Fig. 3, Table 1).
3) In Lake Ouluj ä i, pikepe ch om Lake Vanajanselk ä
ha e been s ocked, mos ly ia a special b ood-
i sh lake (Lake Ki ij ä i) housing a pikepe ch popu-
la ion es ablished in he la e 1980s by ans e ing
Lake Lohjanjä i
Lake
Vanajanselkä
Lake Oulujä i
Lake
Ki ijä i
Lake
A e ia
Lake
Painio
1985–2003
1981–2003
1980s
1993–2003
1999–2001
1930s
2000
1930s
1993–1996
A e ia (Lohjanjä i)
- S1/o iginal (1984)
- S2/ om Lohjanjä i (1994–2000)
Painio (Lohjanjä i)
- S3/o iginal (2006)
Case Lohjanjä i
- S4/o iginal (1982–1986)
- S5/wild (1994–2000)
- S6/mixed (2002–2003)
Case Vanajanselkä
- S7/o iginal (1988–1991)
- S8/ om Lohjanjä i (1994–2000)
- S9/mixed (2001–2006)
Case Oulujä i
- S11/o iginal (1946/1974)
- S12/mixed
- S13/mixed (2002)
Ki ijä i (Vanajanselkä)
- S10/o iginal (2008)
Fig. 3. Gene ic backg ound and popula ion ans e his o y o he sampled Finnish pikepe ch popula ions. Dashed lines indica e ans-
e s o adul i sh, solid lines ans e s o YOY. Sample numbe s (S) e e o Table 1.
He edi as 149 (2012) Gene ic e ec s o suppo i e s ockings on pikepe ch 5
be ween popula ions we e assessed by he - es o pai ed
obse a ions ( NEI 1987). Analysis o he di e ences
be ween samples was based on allele equency di e -
ences, using pai wise F
s alues ( WEIR and COCKERHAM
1984), which we e es ima ed wi h FSTAT e . 2.9.3 ( GOUDET
2001). S anda d de ia ions and con i dence in e als we e
es ima ed h ough boo s apping. Gene ic dis ances
be ween samples we e calcula ed using Nei ’ s D
A dis ances
( NEI e al . 1983). A phylogene ic ee was cons uc ed
using a neighbou joining (NJ) algo i hm ( SAITOU and NEI
1987) wi h DISPAN so wa e ( OTA 1993). Boo s apping
wi h 1000 eplica es was used o es he s a is ical s eng h
o he b anches.
To analyse he popula ion mix u es in he ecipien
lakes, Bayesian clus e ing algo i hms we e used in he
p og am STRUCTURE ( e . 2.2.3) ( PRITCHARD e al. 2000;
F ALUSH e al. 2003; PRITCHARD and WEN 2004). The p o-
g am assigns indi idual i sh o one o mo e g oups, wi h
hei ela i e equency o p edic ed membe ship o alling
1.00. This allowed analyses o admixed popula ions wi h
p io in o ma ion om he sou ce popula ions. In all cases,
he op ions o using popula ion in o ma ion and applying
he admix u e model o he unknown ca ch sample we e
used. Mo eo e , alpha , desc ibing he amoun o popula-
ion mixing, was allowed o a y in all cases and was di -
e en o each popula ion. The o al leng h o he uns was
150 000 i e a ions, wi h a bu n-in o 100 000 i e a ions
and he las 50 000 i e a ions being used o he es ima es.
DNA analysis and calcula ions
DNA ex ac ion and mic osa elli e labo a o y analysis
we e conduc ed acco ding o he desc ip ion o S Ä IS Ä e al.
(2010). Va ia ion in he ollowing nine mic osa elli e loci
was de e mined: P l aL3, P l aL8 ( LECLERC e al. 2000),
S i4, S i6, S i18, S i33 ( BORER e al. 1999), S iL7, S iL8
and S iL11 ( WIRTH e al. 1999).
The numbe o alleles in samples was compa ed using a
a e ac ion-based allelic ichness measu e ( EL MOUSADIK
and PETIT 1996; PETIT e al. 1998), which was calcula ed
wi h FSTAT so wa e e . 2.9.3 ( GOUDET 2001). The p o-
g am calcula es allelic ichness o he smalles numbe o
indi iduals yped o any locus. Each locus was calcula ed
sepa a ely wi h he same numbe o e all popula ions, and
he mean was calcula ed o e loci. Popula ion di e en ia-
ion was analyzed wi h he GENEPOP ( e . 4.0) so wa e
package ( RAYMOND and ROUSSET 1995; ROUSSET 2008)
wi h Ma ko chain pa ame e s, 300 ba ches and 3000
i e a ions. The Bon e oni co ec ion ( RICE 1989) was
applied o co ec o he numbe o es s in he H-W equi-
lib ium. The po en ial occu ence o null alleles was
also checked by GENEPOP. Indica ion o a null allele in
locus S i33 could be seen, bu i was s ill included in
he analysis, as indica ion o null alleles may esul om
Ha dy-Weinbe g de ia ions as well.
The expec ed he e ozygosi y le el in each sample was cal-
cula ed using Popgene e . 1.32 ( YEH and BOYLE 1997). Di -
e ences in he mean he e ozygosi ies and allele ichness ’ s
Table 1. Analysed pikepe ch samples. Sample numbe , gene ic backg ound o he popula ion, sampling si e (Fig. 1),
sampling pe iod (A ⫽ p e-s ocking, B ⫽ pos -s ocking), sample size (n), ca ch yea , yea class and s a us o s udied
pikepe ch samples. * Indi iduals o he sample we e ecognized om ho b anding ma ks.
Sample Gene ic backg ound Sampling lake
Sampling
pe iod n Ca ch yea Yea class S a us
S1 Lohjanj ä i (b oods ock) A e ia – 63 1984 1979 – 1982 o iginal/sou ce
S2 Lohjanj ä i Lohjanj ä i B1 59 1994–2000 1991 – 1993 Lake A e ia o igin *
S3 Lohjanj ä i (b oods ock) Painio – 74 2006 1985 – 2005 o iginal/sou ce
S4 Lohjanj ä i Lohjanj ä i A 60 1982–1986 1979 – 1981 O iginal
S5 Lohjanj ä i Lohjanj ä i B1 60 1994–2000 1991 – 1995 wild *
S6 Lohjanj ä i and Vanajanselk ä Lohjanj ä i B2 200 2002–2003 1998 – 2002 cu en , mixed
S7 Vanajanselk ä Vanajanselk ä A 60 1988–1991 1984 – 1986 o iginal
S8 Vanajanselk ä Lohjanj ä i B1 60 1994–2000 1993 – 1995 Vanajanselk ä o igin *
S9 Vanajanselk ä
and Lohjanj ä i
Vanajanselk ä B 208 2001–2006 1998 – 2002 cu en , mixed
S10 Vanajanselk ä
(b oods ock)
Ki ij ä i – 31 2008 1992 – 1998 o iginal/sou ce
S11 Ouluj ä i Ouluj ä i A 8, 15 1946, 1974 1936 – 1943,
1961 – 1968
o iginal
S12 Ouluj ä i and
Vanajanselk ä
Ouluj ä i B1 100 1990s 1990 – 1992 mixed
S13 Ouluj ä i and Vanajanselk ä Ouluj ä i B2 100 2002 2001 cu en , mixed

6 M. Salminen e al. He edi as 149 (2012)
Fig. 4a – d. Es ima ed popula ion s uc u e o pikepe ch om Bayesian STRUCTURE analysis o ou ca ch mix u es. Each indi idual
is ep esen ed by a hin e ical line, which is pa i ioned in o K colou ed segmen s ha ep esen i s es ima ed popula ion g oup mem-
be ship ac ions. Black lines sepa a e indi iduals om di e en numbe ed samples. Sample names and numbe s a e gi en sepa a ely
o each case. ( a ) Lake Lohjanj ä i 2000, Popula ion 1 ⫽ A e ia, ed (S1), 2 ⫽ Painio, g een (S3), 3 ⫽ Vanajanselk ä , blue (S7), and
4 ⫽ o iginal Lohjanj ä i, yellow (S4), 5 ⫽ ca ch mix u e o Lake Lohjanj ä i in 2000 (S6). ( b ) Lake Vanajanselk ä 2000, (Popula ion
1 ⫽ A e ia, ed (S1), 2 ⫽ Painio, g een (S3) and 3 ⫽ o iginal Vanajanselk ä , blue (S7), 4 ⫽ ca ch mix u e om Lake Vanajanselk ä in
2000 (S9). ( c ) Lake Ouluj ä i 1990. Popula ion 1 ⫽ Ki ij ä i, ed (S10), 2 ⫽ Ouluj ä i o iginal, g een (S11) and 3 ⫽ ca ch mix u e
om Lake Ouluj ä i in he 1990s (S12). ( d ) Lake Ouluj ä i 2000. Popula ion 1 ⫽ Ki ij ä i (S10), 2 ⫽ Ouluj ä i o iginal (S11) and
3 ⫽ ca ch mix u e om Lake Ouluj ä i in 2000 (S13). Numbe s in b acke s e e o Table 1, sample numbe .
Con e gence o all uns was checked. In all cases, he
numbe o con ibu ing popula ions, K, was known, which
simpli i ed he analyses. Se e al uns we e ca ied ou o
each admix u e and he consis ency o he uns was
assessed. Changes in K we e also es ed wi h K alues o
one mo e o less han he known numbe o popula ions,
and esul s wi h he g ea es pos e io p obabili ies a e
p esen ed.
Admix u e analysis was also pe o med wi h maximum
likelihood es ima ion by WANG (2003), included in he
LEADMIX so wa e. This is based on he p inciple ha
allele equencies o he admixed popula ions should be
He edi as 149 (2012) Gene ic e ec s o suppo i e s ockings on pikepe ch 7
he e ozygosi y (H
e ⫽ 0.54) in he p e-s ocking sample o
Lake Ouluj ä i (S11; Table 2). The lowes allelic ichness
(3.6 alleles) was obse ed in he Lake Painio popula ion
(S3) and in he p e-s ocking sample om Lake Lohjan-
j ä i (S4), and he lowes expec ed he e ozygosi y in he
o iginal Lake A e ia popula ion (S1; 0.41). The geno ype
dis ibu ions o he h ee na i e popula ions in lakes
Lohjanj ä i, Ouluj ä i and Vanajanselk ä did no de ia e
om Ha dy–Weinbe g equilib ium a e Bon e oni co -
ec ion.
The gene ic di e si y was in gene al ela i ely high in
all cases bo h be o e and a e s ock ans e s (Table 2),
and no dec ease in gene ic di e si y could be obse ed as
a esul o s ocking. In all h ee cases, allelic ichness was
ac ually somewha highe a e eleases han in he o igi-
nal p e-s ocking popula ion. In Lakes Lohjanj ä i and
Vanajanselk ä , he mean he e ozygosi y was also highe in
he con empo a y han in he na i e popula ion.
The only s a is ically signi i can di e ence in he mean
he e ozygosi y was be ween he Lake Painio popula ion
(S3) and he con empo a y admixed popula ion o Lake
Lohjanj ä i (S6), which had a highe di e si y. Allelic ich-
ness was also s a is ically signi i can ly highe in he con-
empo a y Lohjanj ä i sample (S6) han in he samples
om Lake A e ia (S1), Lake Painio (S3) and e en in he
sample om he na i e Lake Lohjanj ä i popula ion (S4).
Samples S2 and S8 om Lake Lohjanj ä i, bo h ep e-
sen ing h ee consecu i e yea -classes o adul F
1 i sh
iden i i ed o hei s ock o o igin (Lake A e ia and Lake
Vanajanselk ä , co espondingly) by ma king, showed
gene ic di e si y compa able o ha in hei sou ce popu-
la ions (S1 and S7), indica ing ha gene ic di e si y was
linea combina ions o hose o he con ibu ing pa en al
popula ions a he ime when admix u e occu s. In addi-
ion o some p e ious p og ams, i also akes in o accoun
gene ic d i ha has po en ially occu ed in pa en al pop-
ula ions and in admix u e popula ions since he admix-
u e, and e en he po en ial d i o he pa en al popula ions
be o e admix u e occu ed. The p og am addi ionally
gi es 95% con i dence in e als o he admix u e p opo -
ions. Resul s o he STRUCTURE and LEADMIX analy-
sis we e compa ed wi h he popula ion g ouping analysis
based on gene ic dis ances.
Analysis was ca ied ou o ou ca ch mix u e popula-
ions: Lohjanj ä i 2000 (Table 1, S6), Vanajanselk ä 2000
(Table 1, S9) Ouluj ä i 1990s (Table 1, S12) and Oulu-
j ä i 2000 (Table 1, S13). Fo he Lake Lohjanj ä i case,
he po en ial addi ional con ibu o s we e he popula ions
om Lakes Painio, A e ia and Vanajanselk ä , and o Lake
Vanajanselk ä , he popula ions om Lakes Painio and
A e ia, (Fig. 3). Fo he Lake Ouluj ä i case, he only
po en ial con ibu ing o eign popula ion was he Ki i-
j ä i b ood s ock o Vanajanselk ä o igin.
RESULTS
Gene ic di e si y in pikepe ch samples
The o e all expec ed mean he e ozygosi y (H
e ) o all sam-
ples was 0.51 and he mean allelic ichness o e all sam-
ples was 4.1 alleles loci
⫺1 . The F ST o e all popula ions
was as high as 0.08. The highes allele ichness was
obse ed in he Lake Ki ij ä i b oods ock popula ion
(S10), wi h 4.6 alleles loci
⫺1 , and highes expec ed
Table 2. The gene ic di e si y o he pikepe ch samples o he h ee cases, he sampling lake, ca ch yea , s a us o he
popula ion, mean sample size o nine loci, mean expec ed he e ozygosi y ( H
e ) and i s s anda d e o (SE), and a e age
allelic ichness (A
) o nine DNA mic osa elli e loci.
Sample Sampling lake Ca ch yea S a us Mean n/locus H
e SE A
Case Lohjanj ä i
S1 B oods ock, A e ia, 1984 o iginal/ sou ce 58.0 0.41 0.08 3.7
S2 Lohjanj ä i 1994 – 2000 A e ia, o igin 56.6 0.46 0.08 3.9
S3 B oods ock, Painio 2006 o iginal/ sou ce 69.9 0.45 0.08 3.6
S4 Lohjanj ä i 1982 – 1986 o iginal 59.1 0.44 0.09 3.6
S5 Lohjanj ä i 1994 – 2000 wild 59.4 0.45 0.08 4.0
S6 Lohjanj ä i 2002 – 2003 cu en , mixed 195.0 0.51 0.08 4.4
Case Vanajanselk ä
S7 Vanajanselk ä 1988 – 1991 o iginal 58.7 0.49 0.09 4.3
S8 Lohjanj ä i 1994 – 2000 Vanajanselk ä , o igin 58.4 0.48 0.09 4.1
S9 Vanajanselk ä 2001 – 2006 cu en , mixed 204.2 0.53 0.08 4.5
Case Ouluj ä i
S10 B oods ock, Ki ij ä i 2008 o iginal/ sou ce 30.7 0.52 0.09 4.6
S11 Ouluj ä i 1946, 1974 o iginal 14.6 0.54 0.07 3.8
S12 Ouluj ä i 1990s Mixed 95.3 0.46 0.10 4.0
S13 Ouluj ä i 2002 cu en , mixed 98.4 0.47 0.09 4.2
Mean 0.51 0.08 4.1
8 M. Salminen e al. He edi as 149 (2012)
Table 3. Mean p opo ions (%) o indi iduals assigned o each o he p e-de i ned popula ions om each o he ou
admixed pikepe ch samples by he Bayesian STRUCTURE p og am (Bayes es ima e), and s ock p opo ion es ima es
wi h hei 95% con i dence in e als (CI) om he maximum-likelihood es ima ion o he LEADMIX p og am (MLE
es ima e) .
Bayes es ima e % MLE es ima e % 5% CI 95% CI
S1 Lohjanj ä i 2000
A e ia
6.4 10.2 0.0 20.9
S3 Painio 5.4 0.0 0.0 12.3
S7 Vanajanselk ä 1980 47.8 54.6 45.8 72.5
S4 Lohjanj ä i 1980 40.5 35.2 14.8 43.6
Vanajanselk ä 2000
S1 A e ia 6.0 10.8 10.7 10.8
S3 Painio 2.2 3.1 3.1 3.2
S7 Vanajanselk ä 1980 91.8 86.2 86.1 86.2
Ouluj ä i 1990
S10 Ki ij ä i-Vanajanselk ä 89.0 99.9 92.8 100.0
S11 Ouluj ä i, o iginal 2.7 0.0 0.0 8.5
S12 Ouluj ä i 1990 8.3 – – –
Ouluj ä i 2000
S10 Ki ij ä i-Vanajanselk ä 89.8 98.3 89.9 100.0
S11 Ouluj ä i, o iginal 6.5 1.7 0.0 11.8
S13 Ouluj ä i 2000 3.7 – – –
in his case qui e e i cien ly ans e ed h ough ea ing
and s ocking om he sou ce lakes o he ecipien popula-
ion.
Admix u e analysis o h ee pikepe ch popula ions
Lake Lohjanj ä i
In he Lake Lohjanj ä i case, a ma ked gene ic con i-
bu ion could be obse ed as esul o he eleases. The
admixed ca ch sample was mainly composed o bo h
Lake Vanajanselk ä and Lake Lohjanj ä i popula ions
(Table 3, Fig. 4a). A la ge p opo ion o indi iduals
we e admix u es. Vanajanselk ä pikepe ch comp ised a
leas abou hal o he ca ch in Lake Lohjanj ä i.
The maximum likelihood es ima e o he con ibu ion
o Vanajanselk ä was 54.6% (95% con i dence in e al
(CI), 45.8 – 72.5%), and ha o indigenous Lake Lohjan-
j ä i pikepe ch was co espondingly only 35.2% (CI:
14.8 – 43.6%) (Table 3). The Bayesian es ima e o he
con ibu ion o Vanajanselk ä was sligh ly less,
being 47.8%, and o Lohjanj ä i somewha mo e,
40.5%. In all cases, he Bayesian es ima es we e wi hin
he 95% con i dence in e als o he maximum likeli-
hood es ima es.
The es ima ed con ibu ion o he Vanajanselk ä popula-
ion in he admix u e was somewha less han he obse ed
con ibu ion o ma ked Vanajanselk ä pikepe ch (62 – 72%)
o Lake Lohjanj ä i ca ch samples om yea -classes
1993 – 1995 ( SALMINEN and RUUHIJ Ä RVI 2004).
The mos commonly eleased s ock in Lake Lohjan-
j ä i has been Lake A e ia pikepe ch (Fig. 2). The la -
es eleases ha e been ca ied ou wi h Lake Painio
pikepe ch, bu e y li le gene ic e ec o hese eleases
could be obse ed, despi e he ela i ely la ge numbe s
o eleased i sh. The la ge con ibu ion om he Lake
Painio pikepe ch eleases could be excluded (shown in
Fig. 4a as g een), bu eleases om Lake A e ia we e
possibly con ibu ing o he ca ch sample, as he
maximum likelihood es ima e was 10% wi h a p oba-
bili y in e al o 0 – 20% o he A e ia s ock con ibu-
ion. The mo e success ul Lake Vanajanselk ä i sh we e
only eleased in 1993 – 1995, and also in much smalle
numbe s.
Lake Vanajanselk ä
In he Lake Vanajanselk ä case, e y li le gene ic con ibu-
ion could be seen as a esul o he eleases (Fig. 4b), and
he o iginal Vanajanselk ä pikepe ch s ill accoun ed o he
majo i y o he ca ch. Acco ding o he Bayesian es ima e,
91.8% o he admix u e gene pool o igina ed om he
indigenous Vanajanselk ä popula ion, and wi h he maxi-
mum likelihood es ima ion he p opo ion was somewha
less, being 86.2% (Table 3). Abou 10% o igina ed om
He edi as 149 (2012) Gene ic e ec s o suppo i e s ockings on pikepe ch 9
(Lohjanj ä i g oup), Lakes Vanajanselk ä , Ouluj ä i mixed
samples, Ki ij ä i and Lohjanj ä i samples he second
g oup (Vanajanselk ä g oup) and he wo no he n na i e
popula ions om Lakes Kemij ä i and Ouluj ä i he hi d
g oup (Fig. 5). The gene ic di e en ia ion be ween allele
equencies o he popula ions be o e and a e eleases
emained s a is ically signi i can wi hin all hese g oups,
and in ac all pai wise compa isons be ween popula ions
we e s a is ically signi i can .
The mean gene ic dis ance wi hin he Lohjanj ä i g oup
was 0.06 and wi hin he Vanaja esi g oup 0.04. The o igi-
nal Lake Ouluj ä i sample was he mos dis inc o he
o he samples and g ouped oge he wi h he sample o
indigenous pikepe ch om he no he n Lake Kemij ä i
(Fig. 1), which was used as an ou g oup in he analysis. In
gene al, he esul s on he gene ic s uc u e con i med he
changes obse ed in he ecipien popula ions in admix-
u e analysis, and esul s om bo h analyses we e cong u-
en o all cases.
Lake Lohjanj ä i
Fi e o he six samples o igina ing om Lake Lohjanj ä i
pikepe ch g ouped in o he same b anch in he dend o-
g am (Fig. 5). The A e ia 1984 sample was mos simila o
he o iginal Lohjanj ä i sample, Painio had some unique
ea u es and he ca ch sample om he 1990s (wild i sh
iden i i ed by ma king) had also shi ed somewha om he
o iginal popula ion. The mos dis inc i e was, howe e ,
he las sample, he admix u e om he yea s 2002 and
2003, which g ouped in o he Vanajanselk ä g oup ins ead
o he Lohjanj ä i g oup. The F
ST be ween he Lohjanj ä i
he A e ia popula ion eleases, and ha dly any om he
Painio popula ion eleases, al hough his popula ion was
he mo e commonly used s ock in eleases, and easily dis-
inguishable om o he popula ions. The 95% con i dence
in e al o he MLE es ima e was na ow, and he Bayes-
ian es ima e did no all wi hin hese limi s.
Lake Ouluj ä i
In he case o Lake Ouluj ä i pikepe ch, he indigenous
popula ion has nea ly disappea ed. The esul s show ha a
la ge majo i y o he con empo a y Lake Ouluj ä i pike-
pe ch popula ion o igina ed om he eleases o Ki ij ä -
i-Vanajanselk ä pikepe ch. In bo h mixed samples, om
1990 and 2000, he p opo ion o i sh o igina ing om he
eleases was abou 90% when es ima ed wi h he Bayesian
me hod (Table 3, Fig. 4c – d). When he po en ial e ec o
gene ic d i was included in he maximum-likelihood
me hod, he p opo ion o he o iginal Vanajanselk ä popu-
la ion inc eased e y close o 100% (Table 3). Fo bo h
Ouluj ä i mixed samples, he pos e io p obabili ies we e
highe in he Bayesian me hod when he numbe o con-
ibu ing popula ions was se o h ee a he han o wo,
indica ing ha he admix u e could no comple ely be
explained by he wo popula ions, and he esul s a e he e-
o e gi en acco dingly.
Gene ic di e en ia ion among s ocks be o e
and a e s ocking
Acco ding o gene ic dis ances, he popula ions g ouped
in o h ee main g oups, whe e Lakes A e ia, Painio and
he o iginal Lohjanj ä i samples o med he i s g oup
Oulujä i 1990s, mixed, S12
90 KEMIJ
Ä
RVI 2006, o iginal
OULUJÄRVI 1946, 1974, o iginal, S11
91
60 Oulujä i 2002, mixed, S13
42
VANAJANSELKÄ 1988–1991, o iginal, S7
82 Vanajanselkä 2001-2006, cu en mixed, S9
36 Vanajanselkä 1994–2000, in Lake Lohjanjä i, S8
Ki ijä i 2008, Vanajanselkä o igin, S10
77
Lohjanjä i 2002–2003, cu en mixed, S6
A e ia 1994–2000, in Lake Lohjanjä i, S2
Lohjanjä i 1990s, wild, S5
54
58
58
78
Painio 2006, S3
A e ia 1984, S1
LOHJANJÄRVI 1980s, o iginal, S4
Fig. 5 . Gene ic dis ances based on nine mic osa elli e DNA loci. Names o indigenous popula ions in capi al le e s. Sample numbe s
(S) e e o Table 1.