Variability in stream discharge and temperatures during ecologically sensitive time periods: a preliminary assessment of the implications for Atlantic salmon

• Main Authors: Tetzlaff, D., Soulsby, C., Youngson, A. F., Gibbins, C., Bacon, P. J., Malcolm, I. A., Langan, S.
• Other Authors: Department of Geography and Environment, FRS Freshwater Laboratory, Faskally, Macaulay Institute
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2005
• Subjects: [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Atlantic salmon; Salmo salar
• Online Access: https://hal.science/hal-00298643; https://hal.science/hal-00298643/document; https://hal.science/hal-00298643/file/hessd-2-691-2005.pdf

International audience This study focused on improving the understanding of the temporal variability in hydrological and thermal conditions and their potential influences on two life stages of Atlantic salmon ( Salmo salar) ? stream resident juveniles and returning adult spawners. Stream discharges and temperatures in the Girnock Burn, NE Scotland, a small nursery stream, were characterised over a time period of ten hydrological years (1994/95?2003/04). Frequency, magnitude, duration and timing of thermal, hydraulic and hydrological conditions were examined using data with a high temporal resolution (hourly and subhourly). Particular attention was focussed on assessing variations during ecologically sensitive time periods when salmon behaviour is most susceptible to environmental perturbations. The Girnock Burn was characterised by a strong inter- and intra-annual variability in the hydrological and thermal regime. This has clear implications for the likely feeding opportunities for juvenile fish in winter and early spring and the emergence of fry in the late spring. The movement of adult spawners towards breeding areas showed a complex dependence on hydrological variability. If discharges were low, fish movement was increasingly triggered by suboptimal flow increases as spawning time approached. Elucidating links between discharge/temperature variability and salmon habitat availability and utilization at appropriately fine temporal scales is a prerequisite to the development of better conservation management strategies and more biologically meaningful flow regimes in regulated river systems.