Abstract
AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 8:77-88 (2016) - DOI: https://doi.org/10.3354/aei00165 Area use and movement patterns of wild and escaped farmed Atlantic salmon before and during spawning in a large Norwegian river Karina Moe1,2, Tor F. Næsje1,*, Thrond O. Haugen2, Eva M. Ulvan1, Tonje Aronsen1, Tomas Sandnes3, Eva B. Thorstad1 1Norwegian Institute for Nature Research (NINA), PO Box 5685 Sluppen, 7485 Trondheim, Norway 2Norwegian University of Life Sciences (NMBU), PO Box 5003 NMBU, 1432 Ås, Norway 3Aqua Kompetanse AS, 7770 Flatanger, Norway *Corresponding author: tor.naesje@nina.no ABSTRACT: We compared the within-river movements and distribution of wild and escaped farmed Atlantic salmon Salmo salar before and during spawning in the Namsen river system of Central Norway. A total of 74 wild and 43 escaped farmed salmon were captured at sea, tagged with radio transmitters and released. Based on our examinations, most, if not all salmon (farmed and wild) entering the River Namsen were sexually mature. Farmed salmon entering the river system had a higher probability than wild individuals of reaching the migration barrier in the upper part of the river, 70 km from the sea. During the pre-spawning and spawning periods, farmed salmon were located mainly in the upper parts (50 to 70 km from the sea), whereas wild salmon were evenly distributed along the entire river during both periods. Consequently, the probability of farmed × wild inter-breeding varied among river sections. Our finding that the distribution of escaped farmed salmon may differ from that of wild salmon and among river sections in the pre-spawning and spawning periods—and that it may also vary over time—must be taken into consideration when (1) designing monitoring programs aimed at estimating the proportion of escaped farmed salmon in rivers and (2) when interpreting monitoring results. Furthermore, targeted fishing in the river aimed at reducing the number of farmed salmon prior to spawning may be more effective in upper rivers sections, and below major migration barriers. KEY WORDS: Radio telemetry · Farmed escapees · Within-river movements · Pre spawning · Spawning period · Introgression risk · River Namsen Full text in pdf format Supplementary material PreviousNextCite this article as: Moe K, Næsje TF, Haugen TO, Ulvan EM, Aronsen T, Sandnes T, Thorstad EB (2016) Area use and movement patterns of wild and escaped farmed Atlantic salmon before and during spawning in a large Norwegian river. Aquacult Environ Interact 8:77-88. https://doi.org/10.3354/aei00165 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 8. Online publication date: February 02, 2016 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2016 Inter-Research.
Highlights
The population of wild Atlantic salmon Salmo salar L. has declined over the last decades, despite efforts to reduce fishing pressure (ICES 2014)
The distribution of wild and escaped farmed Atlantic salmon differed throughout the pre-spawning period (Fig. 2)
The predicted probability of farmed Atlantic salmon migrating to the barrier was 0.5, while that of wild Atlantic salmon was 0.1 (LR χ2 = 37.7, df = 35, p < 0.01)
Summary
The population of wild Atlantic salmon Salmo salar L. has declined over the last decades, despite efforts to reduce fishing pressure (ICES 2014). In areas of intensive salmon aquaculture, populations of wild salmonids may be negatively impacted by increases in the abundance of salmon lice Lepeophtheirus salmonis and other infections. Norway is the world’s largest producer of farmed Atlantic salmon, with a total production of 1 220 000 metric tons in 2014. The total catches of wild Atlantic salmon in Norway were 490 t in the same year (Anonymous 2015b). Escaped farmed salmon can contribute to the depletion of wild salmon populations because of their reduced adaptations to environmental conditions. Wild salmon populations differ in genetic composition as a result of local adaptations to different eco-
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