Interactive effects of substrate sand and silt contents, redd-scale hydraulic gradients, and interstitial velocities on egg-to-emergence survival of Atlantic salmon ( Salmo salar)
We conducted laboratory incubation experiments with Atlantic salmon (Salmo salar) eggs to test a number of hypotheses concerning the relative sensitivity of the incubating eggs to variations in silt (diameter < 0.063 mm) in interaction with sand (0.63 mm < diameter < 2 mm) fractions in the...
Published in: | Canadian Journal of Fisheries and Aquatic Sciences |
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Main Authors: | , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Canadian Science Publishing
2004
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Subjects: | |
Online Access: | http://dx.doi.org/10.1139/f04-236 http://www.nrcresearchpress.com/doi/pdf/10.1139/f04-236 |
Summary: | We conducted laboratory incubation experiments with Atlantic salmon (Salmo salar) eggs to test a number of hypotheses concerning the relative sensitivity of the incubating eggs to variations in silt (diameter < 0.063 mm) in interaction with sand (0.63 mm < diameter < 2 mm) fractions in the incubating gravels, as well as to different strengths of local hydraulic gradients pushing flow across the egg pocket. Our results show that variations of only a few percent of silt content can strongly degrade survival to emergence. Higher silt loadings (>0.5%) are detrimental to survival for all substrate mixtures, except those that are very sparse in sands (<5%). For sand contents over 10%, an increment of 1% silt has over three times the effect on survival as a 1% increment in sand. Increasing hydraulic gradients had a positive effect on median survival, but the effect depended both on the details of the fines composition and on the gradient level. Our results suggest that silt loadings over 1.5% in redds cannot easily be mitigated by stronger gradients. Our data conclusively show that there is no single threshold interstitial flow velocity that insures survival to emergence. Even when maintaining a constant interstitial velocity, survival tended to reduce in higher fines-content substrate. |
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