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- Lundqvist, H, et al.
(författare)
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Monitoring Juvenile Atlantic Salmon and Sea Trout in the River Sävarån, Northern Sweden
- 2010
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Ingår i: Conservation Monitoring in Freshwater Habitats. - Netherlands : Springer Netherlands. - 9781402092770 - 9781402092787 ; , s. 207-218
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Bokkapitel (refereegranskat)abstract
- Wild salmon stocks have declined worldwide (NRC 1996) . In many Baltic Sea riversmost wild populations of Atlantic salmon ( Salmo salar L.) and anadromous trout(sea trout, Salmo trutta L.) have been destroyed, with the remaining stocks foundprimarily in rivers within northern Sweden and Finland. Here they suffer high ratesof fishery exploitation, while hydropower regulation and the re-engineering of riversfor floating timber has led to the loss of spawning and rearing habitat and to a lossof connectivity among habitats (McKinnell 1998) .To remain viable in the face of demographic and environmental stochasticity,salmonid populations require a certain level of abundance, positive growth rates,adequate spatial structure, and access to (connectivity among) habitats of sufficientquantity and quality to express their life history and genetic diversity (McElhanyet al . 2000) . To understand what is limiting their productivity and viability anddevelop conservation actions for these threatened populations, we need informationon both the freshwater and marine phases of the salmon and sea trout life cycles.The Salmon Action Plan (SAP) 1997–2010 was adopted by IBSFC (InternationalBaltic Sea Fishery Commission), and states that by 2010 natural production inBaltic rivers should be >50% of the maximum production potential. To date, maximumnatural production levels have primarily been based on expert knowledge ratherthan empirical estimates (e.g. WGBAST 2008) . The Swedish Government nowrecognises the need for index rivers to obtain reliable estimates of abundance,productivity, population structure, and to collect the information on life-historydiversity needed to manage salmonid stocks.From 2005 to 2008, a pilot study was implemented in the River Sävarån (a small,unregulated forest river in northern Sweden), to monitor the downstream migrationsof salmon and trout, and explore its suitability as an index river. Rotary screwtraps were used to investigate the abundance of smolts as well as their timing, sizeand age, and to obtain samples to analyse the genetic composition of the stock. Parrdensities from electro-fishing surveys were compared with screw-trap data to determinewhether the two approaches produced similar smolt production estimates.
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- Lundqvist, H., et al.
(författare)
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Upstream passage problems for wild Atlantic salmon (Salmo salar L.) in a regulated river and its effect on the population
- 2008
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Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 602, s. 111-127
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Tidskriftsartikel (refereegranskat)abstract
- Due to hydropower development, the upstream migration of wild anadromous salmon and brown trout is impaired in many European rivers, causing negative effects on the long-term survival of natural salmonid populations. This study identified problems for Atlantic salmon during upstream migration in a regulated river in northern Sweden, Umealven (mean flow: 430 m(3) s(-1)). Tagging from 1995 to 2005 involved radio tags (n = 503), PIT tags (n = 1574) and Carlin tags (n = 573) to study the spawning migration of salmon from the coast past the regulated section of the river to a fish ladder at the dam/spillway 32 km upriver. The results demonstrate that migration success from the coast to the fish ladder varied between 0% and 47% among years, indicating an average loss of 70% of potential spawners. Discharge from the turbines attracted the salmon away from the bypass route. Echo-sounding in the turbine outlet showed that salmon were normally found at 1-4 m depths. They responded with upstream and/or downstream movements depending on flow changes; increased spill in the bypass channel attracted salmon to the bypass. Once in the bypass channel, salmon could be delayed and had difficulties passing the first rapid at high spills. Additional hindrances to upstream migration were found at rapids and the area of the fish ladder, located further upstream in the regulated river section. The average migration duration was 44 days from the estuary to the top of the fish ladder, with large variation among individuals within years. Modelling the salmon population dynamics showed a potential population increase of 500% in 10 years if the overall migration success could be improved from the current 30% to levels near 75%. Consequently improved migration facilities at the regulated river section should be implemented to achieve a long-term sustainability of these threatened anadromous salmonids.
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