Abstract
Atlantic salmon Salmo salar smolts were sampled at weirs from two Icelandic rivers (Ellidaár and Vesturdalsá) for a 15-year period to test four hypotheses: (1) longer smolts (i.e., at the high end of the length-frequency distribution) will have higher survival to adulthood than shorter smolts (i.e., in the middle and lower parts of the distribution); (2) plumper (i.e., higher condition factor) smolts will have higher survival to adulthood than leaner (slim or average) smolts; (3) middle-age smolts (i.e., in the middle part of the freshwater age distribution) will have higher survival rates than fish at the extremes of the age distribution; and (4) fish in the middle portion of the smolt run will have higher smolt-to-adult survival than smolts emigrating early and late. Among the three length-groups, significant differences were found in smolt-to-adult survival in each river. In pairwise comparisons, long smolts had significantly higher survival rates than middle-sized and short smolts for both rivers. Among the three condition groups, significant differences were found in smolt-to-adult survival for the Ellidaár but not for the Vesturdalsá. Ages of smolts in the Ellidaár ranged from 1 to 5 years, and more than 98% of smolts were age 2-4. Smolts in the Vesturdalsá ranged in age from 2 to 7 years, and more than 99% of smolts were age 3-5. Among the dominant three age-groups for each river, significant differences were found in smolt-to-adult survival. Among the three migration timing groups, significant differences were found in smolt-to-adult survival in both rivers. In pairwise comparisons for the Ellidaár, late-migrating smolts had significantly higher survival rates than middle and early smolts. In the Vesturdalsá, late-migrating smolts had significantly higher survival than early and middle smolts, which did not differ from each other. These results are placed in the context of optimization of life history strategies and ideas about the process of smoltification in Atlantic salmon life history.
| Original language | English |
|---|---|
| Pages (from-to) | 1688-1698 |
| Number of pages | 11 |
| Journal | Transactions of the American Fisheries Society |
| Volume | 139 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - 2010 |
Bibliographical note
Funding Information:We thank members at the Fisheries Association in Vesturdalsá and Orkuveita Reykjavikur for their support, and we thank the staff at the Institute of Freshwater Fisheries in Iceland for field assistance. Three anonymous reviewers and Dennis L. Scarnecchia provided valuable comments on the manuscript, which we appreciate. This study was partly funded by the Salmon Enhancement Fund in Iceland.