Effects of sediment transport on intergravel flow and egg survival in silt-rich spawning beds

• Main Author: Zimmermann, André E.
• Other Authors: Lapointe, Michel (advisor)
• Format: Thesis
• Language: English
• Published: McGill University 2003
• Subjects: Sediment transport > Québec (Province) > Cascapédia River Watershed; Atlantic salmon > Effect of sediments on > Québec (Province) > Cascapédia River Watershed; Atlantic salmon > Effect of logging on > Québec (Province) > Cascapédia River Watershed; Logging > Environmental aspects > Québec (Province) > Cascapédia River Watershed; Atlantic salmon
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79215

Previous studies have shown fine sediment was removed from spawning beds when salmon dug nests and subsequent sediment deposition can re-clog the nests, which reduces intergravel flow and threatens egg survival. In the intensively logged Cascapedia watershed it is not known if there is enough sediment deposition to re-clog salmon nests. Furthermore, Cascapedia spawning beds are relatively silt-rich, whereas, the effect of fine sediment has been studied in rivers with sand-rich substrate. I evaluated if sediment-epositing events reduced intergravel flow and if these events inhibited egg survival. During the summer and fall 2001, sediment deposition into clean gravel occurred at rates proportional to the length and dose of suspended sediment transporting events. Based on the results of an experimental sensor, sediment deposition reduced intergravel water velocities. Habitat conditions within artificial salmon nests, however, remained above critical levels for egg survival. Eggs survived (81%) until mid-April, at which time they were at the pre-hatched life-stage. The data suggests that in Cascapedia rivers, egg survival is likely only inhibited if the spring-freshet erodes or clogs the salmon nests.