Effects of silt and very fine sand dynamics in Atlantic salmon ( Salmo salar ) redds on embryo hatching success

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Levasseur, Mylène, Bergeron, Normand E, Lapointe, Michel F, Bérubé, Francis
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2006
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1139/f06-050; http://www.nrcresearchpress.com/doi/pdf/10.1139/f06-050

We conducted a 2-year field experiment examining the survival to hatching of Atlantic salmon (Salmo salar) in relation to the seasonal and spatial variations of silt and very fine sand (SVFS; <0.125 mm) content within a large set of artificial redds at two spawning sites of the Sainte-Marguerite River, Quebec, Canada. Each artificial redd consisted of an infiltration cube (30 cm × 30 cm × 20 cm) buried in a morpho-sedimentological unit resembling a salmon redd. One hundred fertilized Atlantic salmon eggs were inserted in a number of infiltration cubes during redd construction. The results indicate no significant relation between survival to hatching in spring and values of the sand index or total percent fine sediment <2 mm in redds at that time. However, the proportion of SVFS in the redds explained 83% of the variation in embryo survival, with a threshold at approximately 0.2% SVFS, above which survival dropped sharply below 50%. Infiltration of these very fine fractions mostly occurred under ice cover, during the low-flow winter period. However, during the spring flood period, infiltration-flushing patterns varied spatially and reflected spatial differences in local intensity of bed-load transport and fine sediment availability.