Management of wild salmon populations in Denmark

Transcription

1 Management of wild salmon populations in Denmark Anders Koed, Danish Technical University, Section for Freshwater Fisheries and Ecology

2 Outline 1. The Danish salmon in a historical perspective what vent wrong? 2. How the (some) salmon populations were saved...

3 Annual catches of salmon in the estuary of River Skjern, Number of salmon caught Otterstrøm (1938) and Statistic yearbooks, the Ministery of Fisheries

4 River Skjern Å land claim project implemented in the 1960 erne Impaired migration and spawning and nursery areas of salmon disappeared

5 1940 Poulsen 1935 Salmon catches in River Gudenåen Number caught

6 Power plant development in 1921 River blockage prevented the salmon in reaching the spawning areas the River Gudenå salmon vent extinct

7 Cause (what vent wrong): Sewage and waste-water caused habitat loss and habitat degradation. This was stopped in 1980 ties.

8 Cause (what vent wrong): Dredging and canalization, Caused habitat loss and habitat degradation.

9 Cause (what vent wrong): Mills ponds, Caused habitat loss and impaired migration.

10 Cause (what vent wrong): Hydropower development, Caused habitat loss and impaired migration.

11 Cause (what vent wrong): Fish farming, Caused habitat loss, habitat degradation and impaired migration. About 800 in 1970, 250 left today.

12 The causes were identified by research. Example negative effects of weirs and barriers Loss and delay of smolts Loss and delay of spawners Loss of habitats Jepsen, Nielsen & Deacon (2005) Svendsen, Koed & Aarestrup (2004) Aarestrup & Koed (2003) Koed, Jepsen, Aarestrup & Nielsen (2002)

13 Smolt loss at barriers Types Number Avg. smolt loss investigated (%) Mills 5 30 Fish farms Hydro Power stations 7 82 Loss when passing 3 fish farms in a river: (1-(1-0.42) 3 )= 80 %! Aarestrup & Koed (2003)

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15 Predation in fish farms

16 Delay desmoltification

17 ...the negative trend can be reversed Salmon spawning-run - River Skjern

18 Wild sea trout smolt production in Denmark, Baltic area

19 using original fish in restored habitats

20 Stocking using original fish in restored habitats In the 1980 ies the salmon populations in Denmark were believed to have gone extinct, except for the one in River Skjern... River Storå River Gudenå River Skjern Å River Varde Å River Sneum Å River Kongeå River Ribe Å River Brede Å River Vidå

21 River Storå development in catches, Stocking of non native orgin

22 using original fish in restored habitats DNA from old scales compared with DNA collected during Old DNA ( ) Present =

23 using original fish in restored habitats 4 indigenous populations left in 1999! River Storå River Gudenå River Skjern River Varde River Sneum River Kongeå River Ribe Å River Brede River Vidå Nielsen, Hansen & Bach (2001)

24 River Storå development in catches, Stocking of native vs non native origin

25 Still need for a supportive stocking programme...

26 Salmon are brought to the hatchery

27 Fry..

28 Stocking of ½ and 1 yearlings

29 Film by Bo Skelmose

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33 River Skjern Å restoration project largest in Northern Europe Povl Toft

34 ..migration barriers have been removed and habitats restored

35 Research based management is central for successful restoration of fish populations this has saved the Danish wild salmon: Regulation of the gear fishery and a quota system in the rivers. Assessment programme of the population size quarto annual. A focused and knowledge based stocking programme. River restoration, e.g. removing obstacles.

36 this has taken us here.

37 Habitat restoration and using original fish Angler-caught salmon and Number of salmon caught New supportive breeding procedure implemented: Only F1 and indigenous fish

38 Successful restoration of salmon populations is based on knowledge obtained from research and monitoring Salmon spawning-run - River Skjern Restoration of habitats Cormorant culling programme in the estuary Supportive breeding procedure optimised: F1, indigenous fish, when reintroducing - geographic closest population Restrictive regulation of the Fishery - Estuary: no-take zone - Restrictive regulation of the commercial fishery - River: restricted period, catch limit, C&R

39 Research based management is central for successful restoration of fish populations

40 In 2004 the Danish Management Plan for Salmon was published it is a unique tool describing which measures should be taken to secure the Danish salmon populations

41 The Management Model for Freshwater Fishes in Denmark Goal: Self-sustaining populations Management system - Habitat restoration - Population restoration Research and Monitoring Legislation - Ministry of Fisheries - Ministry of the Environment Stakeholders - Anglers - Fishermen

42 Research is swiftly feed into management... Goal: Self-sustaining populations Management system - Habitat restoration - Population restoration Research and Monitoring Legislation - Ministry of Fisheries - Ministry of the Environment Stakeholders - Anglers - Fishermen

43 Thanks for your attention!