The impact of abiotic factors on daily spawning migration of Atlantic salmon (Salmo salar) in two north Swedish rivers

摘要: Atlantic salmon (Salmo salar) depends on two major migrations to fulfil their life cycle, from birth place in rivers sea, and back upstream the river again spawn. Salmon stocks have been heavily reduced during last century due human activities such as hydropower timber floating. Construction of fish ladders restoration are recent management actions taken aiming at improving remaining stocks. monitored get information stock status. This study focused how environmental factors correlated with adult spawning migration data northern Sweden, Vasterbotten County, Umealven Byskealven. both were obtained counters placed ladders. The ladder was equipped VAKI counters, 2010-2013 used. 2009-2013 Byskealven used, a PORO counter 2009-2012, 2013. There three questions that led study; (I) which variables can explain daily variations migration? (II) Are there any differences between influencing an exploited compared unexploited river? (III) Can factor be greater or less importance for first half season? Stepwise linear regressions used create models find migration. Both had seasonal pattern most migrating early season. Water flow influence studied rivers. difference second 50 % Adjusted Julian day number explained best model temperature, water flow, adjusted