Monitoring Juvenile Atlantic Salmon and Sea Trout in the River Sävarån, Northern Sweden

• 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.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Nyckelord

Atlantic salmon

sea trout

smolts

rotary screw tap

genetic analyses

Publikations- och innehållstyp

ref (ämneskategori)

kap (ämneskategori)