Abstract
Sea age, size, and condition of adult Atlantic salmon (Salmo salar) are prime determinants of individual, and hence population, productivity. To elucidate potential mechanisms, 151 000 records of salmon returning to six Scottish coastal sites over 44 years were analysed for length, weight, and condition, by site, sex, sea age, and river age. After correcting for capture effort biases, all sites showed seasonal increases in length and weight for both 1 sea winter (1SW) and 2SW fish. However, whereas condition increased slightly with season for 2SW, it decreased notably for 1SW. Sites showed common decadal trends in length, weight, and condition. Within years, length and weight residuals from trends were coherent across sites, but residuals from condition trends were not. Rates of seasonal condition change also showed decadal trends, dramatically different between sea ages, but common across sites within sea-age groups. Longer salmon were disproportionately heavy in all seasons. 1SW condition was markedly lower in 2006. Detrended correlations with oceanic environmental variables were generally not significant, and always weak. A published correlation between the condition of 1SW salmon caught at a single site and sea surface temperatures in the Northeast Atlantic could not be substantiated for any of the six fisheries over the wider time-scales examined.
Original language | English |
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Pages (from-to) | 844-859 |
Number of pages | 16 |
Journal | ICES Journal of Marine Science |
Volume | 66 |
Issue number | 5 |
Early online date | 17 Apr 2009 |
DOIs | |
Publication status | Published - 1 Jun 2009 |
Bibliographical note
We thank all the owners and occupiers of the net fisheries at the North Esk, Strathy Point, Spey, Dee, Tay, and Tweed sites who kindly allowed our staff long-term access to their salmon catches, so to obtain the subsamples from which these data were derived. The Atlantic Salmon Trust provided grant 2007/11 to defray some of the costs of the statistical analysis, and the EU FinE project also part-funded some final details of the work. We thank Ronald Campbell, Ross Gardiner, John Gilbey, Sarah Hughes, Philip McGinnity, and Richard Shelton for discussions and constructive comments, and two anonymous referees for valued comments on the submitted draft.Keywords
- Climate change
- Condition
- Marine environment
- NAO
- Salmo salar
- Sea surface temperature