Deep habitats are important for juvenile Atlantic salmon Salmo salar L. in large rivers

Abstract

Linnansaari T, Keskinen A, Romakkaniemi A, Erkinaro J, Orell P. Deep habitats are important for juvenile Atlantic salmon Salmo salar L. in large rivers. Ecology of Freshwater Fish 2010: 19: 618–626. © 2010 John Wiley & Sons A/SAbstract – Juvenile Atlantic salmon were studied by underwater video surveillance and self contained underwater breathing apparatus‐diving in deep (i.e. >1.0 m), fast flowing areas of two large river systems (River Teno, River Tornionjoki) in northern Finland. Both video and diving data indicated that young‐of‐the‐year (YOY) salmon (0+) and salmon parr (>0+) readily utilised habitats deeper than 1 m. Young‐of‐the‐year salmon and parr were observed through a range of 0.5–1.9 m and 0.4–2.2 m, respectively. A negative linear relationship between the mean abundance of YOY salmon and mean depth was noted from the diving transects. Salmon parr were similarly abundant throughout the range of depths studied. Video data showed that deep habitats were used throughout the summer (June–August). It was concluded that deep, fast‐flowing areas in large rivers may constitute a significant habitat resource for juvenile salmon that has not been traditionally accounted for when estimating salmon production.