Predation on adult Atlantic salmon by endothermic fish (bluefin tuna and porbeagle), large toothed whales and other fish was recorded.
The lead author, John F. Strøm, with one of the Atlantic salmon tagged with a pop-up satellite archival tag before release. Photo: Audun H. Rikardsen
Both predation rates and total mortality were larger for Atlantic salmon from Canada, Ireland, and Spain than for salmon from Denmark and Norway. This geographical variation in ocean mortality correlates with ongoing population declines, which are more profound for southern populations. Hence, low ocean survival of adults may act as an additional impact to already vulnerable populations.
The study was based on tagging Atlantic salmon from 12 rivers with pop-up satellite archival tags.
Data were collected in previous projects, but the finalisation of data analyses and publishing was funded by the SeaSalar project.
The study is published open access in Scientific Reports and can be downloaded here.