HR: 1340h
AN: H53C-1275    [Abstracts]
TI: Linking channel morphology, stream flow and micro-scale hydraulics in habitats utilized by spawning Atlantic salmon
AU: * Moir, H
EM: hjmoir@ucdavis.edu
AF: LAWR, University of California, Davis, One Shields Ave, Davis, CA 95616 United States
AU: Gibbins, C
EM: geo399@abdn.ac.uk
AF: School of Geosciences, Aberdeen University, Elphistone Road, Aberdeen, AB24 3UF United Kingdom
AU: Soulsby, C
EM: geo290@abdn.ac.uk
AF: School of Geosciences, Aberdeen University, Elphistone Road, Aberdeen, AB24 3UF United Kingdom
AU: Webb, J
EM: J.Webb@marlab.ac.uk
AF: Atlantic Salmon Trust, Moulin, Pitlochry, PH16 5JQ United Kingdom
AB: The study examines how instream hydraulics respond to varying flow in differing channel geometries and how this corresponds to habitat utilization by spawning Atlantic salmon. Data on the location, discharge and channel morphology associated with 474 incidences of spawning activity were obtained at the Allt a' Ghlinne Bhig, Scotland. Six study sites were selected that represented the range of channel size and morphology utilized by spawning fish in the stream. Repeat hydraulic surveys were carried out at these sites over the range of stream flows observed to have been utilized by spawners. The hydraulic surveys provided data on how depth, velocity and Froude number distributions varied with stream flow at each of the 6 study sites. Hydraulic geometry-type relationships were produced that related discharge to each hydraulic parameter at each site. These relationships were applied to the discharges associated with specific spawning observations, describing the meso-scale channel hydraulics of each site at the flows under which utilization by fish was observed. This showed that, although the upper limit to the discharges used by spawning fish varied considerably between the 6 study sites, the associated hydraulic characteristics exhibited much less variation, implying a channel morphology control. Indices of hydraulic variability for each site correlated with the associated number of spawning incidents and the discharge range at which they occurred. Habitat suitability criteria applied to the raw hydraulic survey data produced relationships between discharge and habitat availability that were compared to specific spawning discharge observations at each site. This showed that higher flows predicted as providing suitable habitat were not utilized by spawning fish at any of the sites. Although higher flows provide suitable habitat, the flashy hydrological regime of the stream means that these conditions do not persist long enough to permit completion of spawning. It is suggested that in systems with a dynamic hydrological regime, the rate of change of discharge and its effect on channel hydraulics should be considered in habitat modeling exercises.
DE: 1824 Geomorphology (1625)
DE: 0400 Biogeosciences
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting