Expertise for making sustainable choices 2/16/2012 1

Evolutionary genetics of Baltic salmon and its relevance for today's management Marja-Liisa Koljonen, Finnish Game and Fisheries Research Institute

Essential for conserving genetic diversity of the whole Baltic salmon

• To know how genetic diversity is distributed

• - The population structure and the hierarchy

• To know reasons behind the current structure

• - genetic history (colonisation lineages)

• - gene flow levels

• - human impact

• We already know much

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Whole range genetic study: -Barents Sea, -White Sea, - Russian lakes, - Atlantic poulations included (Irish, Scottish, Norwegian, Swedish) In all 38 pops.

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Structure: Strong Three genetic lineages within the Baltic Sea. Larger differences than in the other Europe East, South and West. Similarity: South –Barents Sea-White Sea Säisä et al. 2005

Genetic history

• There has been Atlantic salmon in the Scandinavian area before the last glaciation.

• When the ice sheet advanced from the northwest the inter(pre)glacial salmon populations were forced to move east and south to drainages draining southwards.

• Baltic salmon is not genetically homogenous, but rather exeptionally strongly genetically structured for one sea basin

• There are also older and younger gene pool layers, which have surprisingly well remained distinct after the glaciation, indicating very low levels of gene flow and precise homing behaviour.

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Glaciation history of the Baltic salmon and the three colonisation routes

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Three genetic lineages three colonisation directions

• EAST

• The range of the population of the eastern lineage matched the area of the first stage of the Baltic Sea, the Baltic Ice Lake (10 500 - 10 200 B.P.), before the deglaciation of Finland and northern Sweden.

• Then Lake Ladoga was still part of the Baltic Ice Lake.

• Lake Onega isolated already earlier (12 500 - 11 500 B.P)

• As there is salmon population in Lake Onega it indicates that salmon had already colonised the Baltic Sea before the opening of the western route.

• Refugial areas in lakes in the upper Volga area and River Onega Basin. Lake Onega first drained south into River Volga system, and only later via River Svir to Lake Ladoga.

Glaciation history 2, south • SOUTH

• The southern area was free of ice already at the Baltic Ice Lake stage, but the southern stocks Emån and Mörrumsån differ very significantly from the eastern lineage.

• Southern stocks are more similar with Barents Sea and White Sea salmon than Baltic stocks

• There has been salmon in the south.

• Refugial areas in the Neman, Vistula, Odra and Elbe drainage basins.

• These rivers may be remnants from an older Atlantic-type of salmon.

• Freshwater fishes like perch and grayling are assumed to arrive from the south as well.

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Glaciation history west 3

• WEST

• The range of the western lineage corresponds to the geographical area that was liberated from the ice at the Yoldia Sea stage about 10 300 - 9000 P.B.

• A wide sound across central Sweden, Närke strait, and the first large ingress of sea water turned the water of the Baltic Sea into brackish water.

• The colonisation of the northern Baltic Sea coasts by salmon from the North Sea was possible and at the same time Finland and most of the Swedish coast were free of ice and spawning habitats were available in rivers.

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The relationship of geographical and genetic distances – isolation by distance model -IBD

• In case a isolation-by-distance model fits the data - a balance between gene flow and differentiation is assumed.

• In complete isolation no pattern can be found, often lake populations.

• The geographical and genetic distances of Baltic salmon stock pairs fit the one-dimensional isolation-by-distance pattern. (linear coast model, rather than plane model)

• The correspondence was highly significant for wild stocks, but not for hatchery stocks.

• Geographical distances ( gene flow) alone explains part of the differentiation observed within lineage.

Isolation by distance - for lineages

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WEST: y = 7E-05x + 0,039

R2 = 0,21

INTER REGION: y = 1E-05x + 0,182

R2 = 0,004

EAST: y = 0,0001x + 0,043

R² = 0,57

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0 500 1000 1500

Fst/

(1-F

st)

km

Baltic Sea wild stocks

Northern Baltic

Southern Baltic

Inter regional

Eastern Baltic

Linear (Northern Baltic) Linear (Inter regional)

Linear (Eastern Baltic)

The amount of gene flow at wild state

• Is very difficult to assess with any methods, especially when stocks are similar

• Rough estimates of gene flow levels in the wild state can be calculated from the genetic differentiation levels (Fst).

• Migrants = (1-Fst/2Fst).

• A linear negative regression would be expected between

• log(Migrants) and geographic distance of the river mouths

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Relationship between geographical distance and estimated migrant levels – less than 10, migrants over 100 km distances

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0

0,5

1

1,5

2

2,5

0 0,5 1 1,5 2 2,5 3 3,5

Lo

g1

0 M

igra

nts

Log10km

Wild populations within the eastern lineage

Isolation by distance: Relationship of gene flow to geographical distance all stocks (Koljonen et al. 1999)

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-0,5

0

0,5

1

1,5

2

2,5

3

0 0,5 1 1,5 2 2,5 3

Log m

igra

nts

Log (geographical distance) km

Relation of gene flow to geographical distance wild and hatchery fish

Western lineage

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0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

0 0,5 1 1,5 2 2,5 3

Lo

g (

Mig

ran

ts)

Log (geographical distance)

Western lineage, 4 wild stocks

Gene flow in hatchery stocks no more is related to

geographical distances of the river mouths, but is regulated by human activity .

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-0,5

0

0,5

1

1,5

2

2,5

3

0 0,5 1 1,5 2 2,5 3 3,5

Lo

g (

mig

ran

ts)

Log (geographical distance, km)

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Hierarchical diversity analysis: dividing genetic diversity into hierarchical levels

• Five hierarchical levels were used : total – (Baltic –Atlantic) - Baltic Sea lineage- sea area - stock.

• The total between stock diversity component was 11% from the total genetic diversity

• (G ST = 0.114), half of this was a consequence of differentiation between the three lineages within the Baltic Sea.

Hierarchical diversity analysis of Baltic salmon stocks

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Management and conservation need to have common goals – strategies need also prioritising

• The internationally accepted common long-term goal for the both conservation and management of all living natural resources is to maintain their future evolutionary potential.

• It gives priority to future evolutionary potential even over attained adaptation or historical structures

• It requires maintenance of large evolutionary units, - diversity within lineages

• Conservation values versus extinction risks

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For the strategy:

• The conservation strategy to be constructed from the top of the hierarchy instead of from the individual stock level.

• The population sizes maintained within units will limit the level to which it is possible to proceed in splitting the structure.

• Separate strategies are needed to ensure maintenance of genetic diversity of the upper hierarchical levels (lineages – sea areas separately), not only based on individual stocks

• In all information is needed from:

genetic differentiation, potential reproduction areas,

stock numbers, smolt production levels,

geographical location of stocks, survival risks,

fishing pressure and possible differences in quantitative traits such as migration behavior

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Application for the Baltic salmon

• To preserve genetic diversity throughout the Baltic Sea range with a diversity and viability sufficient to permit the continuous evolution of self-sustaining populations of this isolated, brackish water adapted form of salmon.

• Many salmon stocks and their habitats have been irreversibly lost, only a fraction is left of what it was before human impact

• There can be no return to the original state of Baltic salmon stocks; we can only safeguard the continuous evolution from the present state, in an environment with clearly more limited potential for natural reproduction than in the wild state.

Baltic Salmon 2

• The lack of potential reproduction areas limits enhancement projects, there are homeless stocks

• Care need to be taken of large populations as they include the true evolutionary potential

• The long-term strategy should seek a match between recent genetic material and potential reproduction areas - to ensure that all genetic material and all potential reproduction habitats are in use.

• For the genetic resources of hatchery stocks to become a viable component of salmon evolution, they need to be reintroduced into the wild as naturally reproductive stocks.

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Expertise for making sustainable choices

Genetic effects of large scale releases • 1) Genetic effects to the released stocks themselves:

• They tend to change genetically

• (loss of general amount of diversity, growth rate, age at maturity, survival, migration pattern)

• 2) Genetic effects to the other naturally reproductive stocks:

• Direct genetic effects are related to the amount of gene flow,

• Gene flow depends on the distances between rivermouths,

• number of released fish, and release practice (imprinting of smolts into correct river mouth is essential.

• Previous delayed releases were harmful

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What are the risks of halting the releases

• Risk of loosing diversity of the current hatchery stocks !

• Power plants have the obligation to compensate for the lost catches to sea fishery and to maintain the gene pools of the lost rivers ’forever’.

• If halting of releases will occur, the until now kept gene pools will be lost, if no other solutions are found.

• In Sweden where releases are produced by catching of spawners the genetic resources will be very soon lost.

• In Finland they are kept as long as the broodstocks live.

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Wild (17) and hactchery (17) stocks from salmon baseline

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Stock Country Prop. Stock Country Prop.

1 Tornionjoki, W Fin, Swe Wi 18 Ljungan -"- Wi

2 Tornionjoki, H Fin Ha 19 Ljusnan -"- Ha

3 Simojoki -"- Wi 20 Dalälven -"- Ha

4 Iijoki -"- Ha 21 Emån -"- Wi

5 Oulujoki -"- Ha 22 Mörrumsån -"- Wi

6 Kalixälven Swe Wi 23 Neva, Fi Russia Ha

7 Råneälven -"- Wi 24 Neva, Rus -"- Ha

8 Luleälven -"- Ha 25 Luga -"- Wi, Ha

9 Åbyälven -"- Wi 26 Narva Est, Rus Ha

10 Byskeälven -"- Wi 27 Kunda Estonia Wi

11 Skellefteälven -"- Ha 28 Keila -"- Wi

12 Vindelälven -"- Wi 29 Salaca Latvia Wi

13 Umeälven -"- Ha 30 Gauja -"- Ha

14 Öreälven -"- Wi 31 Daugava, Lat -"- Ha

15 Lögdeälven -"- Wi 32 Venta -"- Wi

16 Ångermanälven -"- Ha 33 Neumunas Lithaunia Ha

17 Indalsälven -"- Ha

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52┌─ Tornionjoki wild 2011

│

85├── Tornionjoki wild 2000

┌─┤

│ ├──── Tornionjoki H 2006

73│ │

┌──23└─── Kalixälven 2002

│ │

75│ │┌───── Simojoki 2006

┌─┤ └┤

│ │ 62└───────── Iijo 2006

52│ │

┌─┤ └─────────────────────────── Råne 2003

│ │

│ │ ┌────── Oulujoki 2006

37│ └────────┤

┌┤ 100└─ Oulujoki 2009

││

57││ ┌─── --Åbya 2003

┌┤└────┤

││ 99└─── Byske 2003

34││

┌┤└───────────────── Skellefteälven 1996

││

54││ ┌────────────────── Öreälven 2003

┌─┤└───────────┤

│ │ 100└─────────── Lögde 2003

│ │

Torneälv

2000- 2011

Fst = 0.0001 ,

No significance

Oulujoki

2006 – 2009

Fst = 0.0043

Significant

Finnish compensation releases

• Bothnian Bay

• Kemijoki: 610 000 smolts

• Iijoki: 315 000 smolts

• Oulujoki: 200 000 smolts

• Total: 1 125 000 smolts

• Bothnian Sea: Komemäenjoki: 50 000 smolts

• Gulf of Finland: Kymijoki: 100 000 smolts

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Number of strayers is low – tens of fishes

• Only 1 fish tagged fish from compensation releases, was found from a wild river (Tornionjoki), during 10 years (2001 to 2011).

• Only 1.7 fish, from 100 000 tagged fish s were found in a wild river

• If about ¼ of tags are found = 6.8 hatchery fish

per 100 000 released fish, and about 60 to 70 fish from all compensation releases annually.

• From the 4364 river samples näytettä, 8 released fish were found - (0,18%), in all about 45 fish per year, when number of spawners is about 25 000 (Romakkaniemi)

• There has been relatively large change in offshore fishery in 2008, when drif net fishery was closed.

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Proportions of Atlantic salmon stocks groups in Åland Sea catches – increase of hatchery stocks in 2008

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0 %

10 %

20 %

30 %

40 %

50 %

60 %

70 %

80 %

90 %

100 %

2000 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Proportions of stock groups in Åland Sea catches

Hatchery, SWE

Hatchery, FIN

Wild

Potential means for avoiding gene flow

• Increasing fishery at the river mouths of closed rivers

• Decrease the amount of released fish to a safe level – sufficient amount spawners return – without straying

• Release geographically and genetically close stocks (identification problem)

• Increase geographic distance from realease sites to wild rivers, to a safe distance

• Decrease fishig pressure gradually, to see if straying rate really increases.

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References • Kallio-Nyberg, I., Saloniemi, I., Koljonen, M-L. 2007. Effects of parental and smolt

traits on the marine survival of released Atlantic salmon (Salmo salar). Aquaculture 272: 254-266.

• Koljonen, M.-L., Jansson, H., Paaver, T., Vasin, O. and Koskiniemi, J. 1999. Phylogeographic lineages and differentiation pattern of Atlantic salmon in the Baltic Sea with management implications. Can. J. Fish. Aquat. Sci. 56: 1766-1780

• Koljonen, M.-L. 2001. Conservation goals and fisheries management units for Atlantic salmon in the Baltic Sea area. Journal of Fish Biology. 59 (Supplement A), 269-288, doi:10.1006/jfbi.2001.1757

• Säisä, M., Koljonen, M.-L., Gross, R., Nilsson, J., Tähtinen, J., Koskiniemi, J., Vasemagi, A. 2005. Population genetic structure and postglacial colonization of Atlantic salmon in the Baltic Sea area based on microsatellite DNA variation. Can. J. Fish. Aquat. Sci. 62, 1887-1904.

• Säisä, M., Koljonen, M.-L. and Tähtinen, J. 2003. Genetic changes in Atlantic salmon stocks since historical times and the effective population sizes of the long-term captive breeding programmes. Conservation Genetics 4, 613- 627.

• Vainikka A., Kallio-Nyberg I., Heino M., Koljonen M.-L. 2010. Divergent trends in life-history traits between Atlantic salmon Salmo salar of wild and hatchery origin in the Baltic Sea. Journal of Fish Biology. 76: 622-640.

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Thank you