genetic diversity and population structure of sea trout in gulf of finland: implications for...
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Genetic diversity and population structure of sea trout in Gulf of Finland:
implications for conservation and management
Riho Gross, Marja-Liisa Koljonen, Oksana Burimski, Jarmo Koskiniemi
• There are approximately 1000 sea trout populations in the Baltic Sea of which about 500 reproduce naturally in Baltic rivers, including about 100 populations in Gulf of Finland (HELCOM 2011).
• Based on electrofishing surveys of parr densities, the sea trout populations in the Gulf of Finland are in an adverse state due to excessive fishing pressure, obstacles to migration, habitat degradation and variation in water flow.
• Stocking of sea trout is widely practiced with the aim of increasing their production. Potential threats:
– irreversible changes of the genetic composition of native populations due to direct (stocking for enhancing purposes) or indirect (immigration of hatchery fish from neighboring rivers) impact;
– non-natural selective pressures under captive conditions (domestication effect) or loss of genetic variation through genetic drift and inbreeding (that always occur in populations of restricted size such as hatchery stocks) may compromise local adaptations of the native populations and pose threat to the evolutionary potential of the species.
• In contrast to the Atlantic salmon, the current knowledge of genetic diversity and structure of sea trout populations in the Baltic Sea is very limited. Only local populations in different countries (e.g. Denmark, Sweden, Poland, Lithuania) have been studied by using various genetic markers but information about the populations in the whole Baltic Sea or even within different major subdivisions of it (including the Gulf of Finland) is still missing.
Background
Average densities of 0+ trout in Estonian (EE) Finnish (FI) and Russian (RU) rivers in Gulf of Finland (ICES 2012)
1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Estonia
NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN 14 6 8 9 12 10 21 6 15
Finland
0 196 260 271 330 318 288 348 176 332 330 398 379 428 373 310 281 190 279 258 316 291 213 239
Russia
NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN 5 3 0 13 95 25 10 3 7
25
125
225
325
425
Sea trout smolt releases (*1000) to the Gulf of Finland by country in 1988-2011
Aims of the study
• to reveal the genetic structure of sea trout populations within the Gulf of Finland
• to estimate the level of genetic variation of sea trout populations within the Gulf of Finland
• to give general recommendations for management
MaterialSampled sea trout rivers in the Gulf of Finland
(22 populations)
(16 populations)
(12 populations)
Sampled sea trout rivers in the Gulf of Riga and from Estonian islands
7 populations
5 populations
Methods:
• Genomic DNA was isolated from fin clips or muscle tissue• 15 microsatellite loci: Ssosl417, Str60INRA, SSa407,
SSosl1311, BS131, SSosl438, Strutta58, SSsp2201, Str15INRA, OneU9, Str73INRA, Ssa85, Str85INRA, SSsp1605, Ssa197
• PCR amplification products were separated by capillary electrophoresis on AB3500 (Tartu) and AB3130 (Helsinki) Genetic Analyzers and the sizes of the microsatellite alleles were determined using Genemapper software
• Allele sizes of microsatellite loci were calibrated and standardized by exchange of reference samples
Data analysis• The genotype data were analysed by standard population genetic
analysis tools (GENEPOP, ARLEQUIN, FSTAT, POPULATIONS, MEGA)• Genetic diversity was estimated as an allelic richness and an
average observed/expected heterozygosity of populations• The level of population differentiation was esimated by pair-wise FST
values• Hierarchical distribution of genetic diversity was estimated by
AMOVA method• Genetic similarities/dissimilarities between populations were
estimated based on pair-wise DA genetic distances and depicted graphically as an unrooted neighbour-joining dendrogram
Results and Discussion
Genetic similarity of sea trout populations:NJ dendrogram (Nei’s Da distance)
Inga
rski
lanj
oki
Kos
kenk
ylan
joki
98
Sip
oonj
oki
87
Man
kinj
oki
80
Espo
onjo
ki
Vanta
anjok
i
Kymijo
ki
Summanjoki
99
AurajokiFiskarsinjoki
99Kiskonjoki
53
PaimionjokiUskelanjoki
78
KarjaankjokiSiuntionjoki
Urpalanjoki
Vilajoki
VirojokiMustajoki
SantajokiVammeljoki
RajajokiNotkopuro
Pikkuvamm
eljokiInojoki
Kuokkalanpuro Luga
Udria S
ista
52
Tre
ppoj
a
Vaa
naA
ltja
Pad
aP
urts
eV
alkl
a
Vosu
Vainup
ea
KeilaVasalemma
Leiva
SeljaLoobu
Toolse
70
Kunda
62
MustojaValgejoeLoo
Pudisoo
Pyhajogi
95
TorvaOngu
Punapea
PidulaK
ydema
Jama
ja64
Tosta
maa
Tim
mkanalLem
me
Haadem
eesteK
olgaKadaka
Loode
88
0.01
Population structure
Average genetic diversity of sea trout populations in different geographic regions
Estonia + Luga, Sista Finland Fin/Rus Russian Karelia
Genetic diversity of sea trout populations in the Gulf of Finland
Differentiation of sea trout populations
Fst = 0.031
Fst = 0.106 Fst = 0.060
Fst = 0.137
• global FST = 0.108• 4.8 % - between geographic
regions • 6.0 % - among populations
within the geographic regions• 89.2 % - within populations
Gulf of Finland:
EST_G. Fin FIN_G. Fin FIN/RUS_G. Fin RUS_G. Fin EST_G. Riga EST_IslandsEST_G. Finland 0.040 0.115 0.123 0.075 0.068 0.063FIN_G. Finland 0.115 0.132 0.172 0.138 0.148 0.116FIN/RUS_G. Finland 0.123 0.172 0.132 0.115 0.139 0.105RUS_G. Finland 0.075 0.138 0.115 0.062 0.094 0.080EST_G. Riga 0.068 0.148 0.139 0.094 0.059 0.075EST_Islands 0.063 0.116 0.105 0.080 0.075 0.028 Average from other 0.089 0.138 0.131 0.100 0.105 0.088
Average FST within (along diagonal) and between regions:
Conclusions• The average level of genetic variation of sea trout populations in Gulf of Finland
was comparable to that in Gulf of Riga but a little bit lower than in Estonian islands.
• Within countries, the level of genetic variation among populations was relatively similar in Estonia and Russia but more variable in Finland and Finnish/Russian border area. Populations with the highest genetic variation should be considered as a basis for forming hatchery stocks within each region.
• The overall level of genetic differentiation between studied populations in Gulf of Finland was moderate (FST = 0.108). The populations were most differentiated in Finland and Finnish/Russian border area and least differentiated in Estonia and Russia.
• Based on genetic distances, the populations clustered well according to the geographic regions. These 4 geographic groupings should be managed separately.
• The results of our study allow to propose genetic management and conservation units for sea trout in the whole Gulf of Finland and enable genetic data based planning for hatchery rearing and enhancement releases.
Thank you for your attention!