Contrasting temperatures, waterflows, and light: seasonal habitat selection by young Atlantic salmon and brown trout in a boreonemoral river

Abstract

Habitat use and habitat selection by young Atlantic salmon and brown trout were investigated by direct underwater observation. We sampled during winter and summer water temperatures (low: 3 -7°C; high: 9 -12°C) coinciding with low and high waterflows (12-20 and 60-80 m 3 s − 1 ), and during day and night in winter, and on six selected stations in the river. Observations of 396 salmon and 120 trout indicated a distinct seasonal pattern in behaviours and habitat selection. Feeding was the dominant behaviour at high water temperatures during summer. In winter, there was a diurnal pattern in behaviour; both species sheltered in interstitial spaces in the substrate during daylight, but during night held positions on or close to the substrate in slower flowing stream areas. Coarse substrate providing cover was therefore an important habitat factor during daylight at low water temperatures, while slow-flowing water was important during night. Although spatial niche overlap was considerable both in summer and winter, salmon and trout segregated with respect to meso-and microhabitat selection, and relatively more at low temperatures. Both species changed their use of mesohabitats towards more slow-flowing glide/flat habitats in winter. Irrespective of season, trout preferred in general more slow-flowing water than salmon did, but the difference was more pronounced in winter. Salmon used a wider range of water depths and in particular water velocities, than did trout. Both species were less tolerant of high water velocities at low water temperatures. The seasonal and diurnal pattern in habitat selection reported have important implications for habitat research and habitat-hydraulic modelling. Copyright

Habitat Use by Native and Stocked Trout (Salmo Trutta L.) in Two Northeast Streams, Portugal

“…Furthermore, it has been argued that HSC must be developed for each species taking into account the developmental stages (alevins, juveniles, adults), seasonal (summer vs. winter) and day cycles (night vs. day) and the main activities exhibited by fish (i.e. feeding or resting) (ROUSSEL et al, 1999;HEGGENES and DOKK, 2001). …”

The influence of hydroelectric power generation on the body composition of juvenile Atlantic salmon

“…Cunjak and Therrien, 1998;Olsen and Vøllestad, 2001;Mitro and Zale, 2002;Finstad et al, 2004b;Johnston et al, 2005). Spatial limitations are evident as fluvial Atlantic salmon parr in winter use only a portion of available habitats (Heggenes et al, 1999, Heggenes andDokk, 2001), which may be altered by ice and flow . Seasonal patterns of survival of young salmonids may thus be of considerable significance.…”

Does ice matter? Site fidelity and movements by Atlantic salmon (Salmo salar L.) parr during winter in a substrate enhanced river reach

“…spring, summer and/or autumn). However, the winter habitats of stream salmonids have been shown to differ from those used during warm water conditions (Heggenes and Dokk, 2001;Mäki-Petäys et al, 2004) possibly due to the need to find refugia from predation or ice (Heggenes et al, 1993;Valdimarsson and Metcalfe, 1998). In particular, a shift into deep, low velocity habitats is often reported in association with the use of coarse substrate material (Saunders and Gee, 1964;Heggenes and Dokk, 2001;Mäki-Petäys et al, 2004).…”