The early marine distribution of Atlantic salmon in the North-east Atlantic: A genetically informed stock-specific synthesis
Date
2021-07-05
Journal Title
Journal ISSN
Volume Title
Publisher
Wiley
Abstract
The survival of Atlantic salmon (Salmo salar), an increasingly rare anadromous species,
has declined dramatically during its marine phase, with disproportionate impacts on
the poorly understood early post-smolt
period. Logistical constraints on collecting
oceanic data to inform this issue pose a formidable obstacle. To advance understanding
of post-smolt
distributional ecology in the North-east
Atlantic, a comprehensive
analysis of existing information was undertaken. Data were synthesized from 385 marine
cruises, 10,202 individual trawls, and 9,269 captured post-smolts,
spanning three
decades and ~4.75 million km2 of ocean, with 3,423 individuals genetically assigned
to regional phylogeographic origin. The findings confirm major migrational post-smolt
aggregations on the continental shelf-edge
off Ireland, Scotland and Norway, and an
important marine foraging area in the Norwegian Sea. Genetic analysis shows that
aggregational stock composition does not simply reflect distance to natal rivers, with
northern phylogeographic stock groups significantly under-represented
in sampled
high-seas
aggregations. It identifies a key foraging habitat for southern European
post-smolts
located in international waters immediately west of the Vøring Plateau
escarpment, potentially exposing them to a high by-catch
mortality from extra-territorial
pelagic fisheries. Evidence of the differential distribution of regional stocks
points to fundamental differences in their migration behaviours and may lead to inter-stock
variation in responses to environmental change and marine survival. The study
shows that understanding of post-smolt
marine ecology, as regards to stock-specific
variations in habitat utilization, biological performance and exposure to mortality factors,
can be significantly advanced by data integration across studies and exploiting
genetic approaches.
Description
Publication history: Accepted - 3 June 2021; Published online - 5 July 2021.
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Article
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Keywords
genetic stock identification, marine distribution, migration behaviour, pelagic trawls, post-smolts, Salmo salar
Citation
Gilbey, J., Utne, K.R., Wennevik, V., Beck, A.C., Kausrud, K., Hindar, K., Garcia de Leaniz, C., Cherbonnel, C., Coughlan, J., Cross, T.F., Dillane, E., Ensing, D., García‐Vázquez, E., Hole, L.R., Holm, M., Holst, J.C., Jacobsen, J.A., Jensen, A.J., Karlsson, S., Ó Maoiléidigh, N., Mork, K.A., Nielsen, E.E., Nøttestad, L., Primmer, C.R., Prodöhl, P., Prusov, S., Stevens, J.R., Thomas, K., Whelan, K., McGinnity, P. and Verspoor, E. (2021) ‘The early marine distribution of Atlantic salmon in the North‐east Atlantic: A genetically informed stock‐specific synthesis’, Fish and Fisheries. Wiley. doi:10.1111/faf.12587.