Changes in growth and migration patterns of sea trout before and after the introduction of Atlantic salmon farming

• Published in: ICES Journal of Marine Science
• Main Authors: Eldøy, Sindre Håvarstein, Ryan, Diarmuid, Roche, William, Thorstad, Eva Bonsak, Næsje, Tor, Sjursen, Aslak Darre, Gargan, Paddy, Davidsen, Jan Grimsrud
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press 2020
• Subjects: Atlantic salmon
• Online Access: https://hdl.handle.net/11250/2679883; https://doi.org/10.1093/icesjms/fsaa125

Marine growth has strong implications for reproductive potential and ultimate fitness of sea trout. Hence, the effects of anthropogenic factors on marine growth are important when evaluating population responses and implementing management measures. Temporal changes in growth patterns of sea trout from three Norwegian and two Irish watercourses were examined, covering time spans of 25–65 years. Elemental chemistry Ba:Ca profiles and visual reading of fish scales were used to estimate smolt length and lifetime growth after first sea entry. Reduced growth after the first sea entry coincided with periods of nearby (<14 km) salmon-farming activity in impacted watersheds in both countries. Increased Ba:Ca levels were also recorded during these periods, likely indicating reduced residency in marine habitats caused by premature return to freshwater and estuaries. An increase in estimated length at first sea entry coinciding with salmon-farming activity, for groups of fish sampled after sea migration, suggests a size-selective marine mortality, with the smallest individuals experiencing a larger mortality. publishedVersion This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.