Journal Article

Interannual changes in recruitment of the Atlantic salmon (<i>Salmo salar</i>) population in the River Oir (Lower Normandy, France): relationships with spawners and in-stream habitat

Jean-Luc Baglinière, Frédéric Marchand and Vincent Vauclin

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 62, issue 4, pages 695-707
Published in print January 2005 | ISSN: 1054-3139
Published online January 2005 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2005.02.008
Interannual changes in recruitment of the Atlantic salmon (Salmo salar) population in the River Oir (Lower Normandy, France): relationships with spawners and in-stream habitat

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Since 1985, the dynamics of the Atlantic salmon (Salmo salar) population in the River Oir, a spawning tributary of the River Sélune (Lower Normandy, France), have been studied from a data set of parr density and the number and the age structure of migrating fish (smolts and adults). Parr densities (1.5–17.4 per 100 m2) and smolt production (0.25–9.2 per 100 m2) varied considerably from year to year. Migrating juveniles were mainly 1 year old. Abundance of parr and smolts was strongly correlated with 0+ densities. Egg-to-smolt survival rates were highly variable year on year (0.044–1.07%). During the juvenile freshwater phase, mortality was highest between the egg and the 0+ stage (97.5–99.9%). The fluctuations in abundance of juvenile salmon appear to be linked to the number and distribution of spawners within the stream during spawning, and also to the amount of silt deposition on the spawning beds. As a result, mortality was highest during the under-gravel phase, and the mean survival rate from egg to smolt was much lower than in rivers less impacted by human activities. Therefore, during the study period, the low production of smolts during some years might lead to a low renewal rate of the salmon population.

Keywords: abundance; anthropogenic impact; Atlantic salmon; silt deposition; survival

Journal Article.  6413 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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