Groundwater, critical habitats, and behaviour of Atlantic salmon, brown trout and Arctic char in streams

• Main Authors: Heggenes, Jan, Bremset, Gunnbjørn, Brabrand, Åge
• Format: Report
• Language: English
• Published: Norwegian Instutitute for Nature Research 2010
• Subjects: Arctic; Atlantic salmon
• Online Access: http://hdl.handle.net/11250/2642611

Heggenes, J., Bremset, G. & Brabrand, Å. 2010. Groundwater, critical habitats, and behaviour of Atlantic salmon, brown trout and Arctic char in streams. – NINA Report 654, 28 pp Streams are characterized by turbulent hydraulic forces, varying discharge and temperatures, short water retention times, bedload transport and dynamic channel morphology. Alluvial groundwater is more stable with laminar flow, longer residence times, less variable tempera-tures, and constant sediment structure. Surface waters and groundwaters are closely connected in the hyporheic ecotone which can act as a source or sink, depending on complex physical and chemical spatial and temporal patch characteristics, direction and volume of flows, in-substrate pore space and connectivity, and movement patterns of organisms. Outflow-ing groundwater provides base flows, differs in temperature, dissolved oxygen levels and water quality from the surface water. Areas of groundwater inflow may at times provide moderated habitat conditions and possibly refugia for mobile stream salmonids. A literature review suggests that groundwater may be important to salmonids by 1) modulating temperatures, 2) influencing water quality (nutrients, oxygen), 3) providing river base flows, and 4) providing refugia. It is well documented that salmonids may use groundwater inflow sites for behavioural thermoregulation to avoid near-lethal temperatures, and maintain energetically favourable body temperatures. Such thermoregulation may be effected through short vertical movements into the substrate, in particular for small fish, or through longer longitudinal movements. Such behaviour is observed during summer high temperatures and low flows, and at the onset of winter and ice formation. Actual field documentation varies among species, but it is likely a general behavioural strategy in mobile salmonids. Because of the local complexity in surface-subsurface and hyporheic flow connectivity and pattern in space and time, in situ studies are required. Spawning site ...