Do Atlantic salmon from Southern Norway migrate as far north as previously tagged salmon from Northern Norway?
We do not follow juvenile Atlantic salmon during the first ocean migration, because they are too small for the tags. Atlantic salmon may spawn several times and migrate to the ocean for feeding between each spawning. We tag adult salmon (kelts) in the spring, after they spawned last autumn and have stayed in the river during winter and are ready for a new sea migration. Photo: Eva B. Thorstad
We have tagged salmon from the rivers Etne and Nidelva (Arendal) with pop up satellite tags, and are excited to see where the tags might pop up in some months.
The North Atlantic Ocean is big, and to examine what influences sea survival and growth of Atlantic salmon, we first need to know where in the ocean they reside.
Tagging of salmon from Northern Norway with satellite- and geotags has shown that previous knowledge regarding salmon feeding at the Faroes and Greenland is not the full story. Salmon from Rivers Alta and Neiden tagged with satellite- and geotags migrated much further north than previously known, to Arctic areas, at Spitsbergen, Jan Mayen and in the Barents Sea.
Since fish are in water, they cannot be continuously be followed by satellite tracking. Fish tags therefore collect and store data on light, depth and temperature during the migration. At a predetermined time next winter the tags release from the fish, floats to the surface, tell the satellite where it is, and downloads stored data. The downloaded data are used to estimate the migration route from tagging to the pop up location.
The cost of tags does not allow for tagging of a large number of fish, but with the present lack of knowledge, detailed migration tracks from only a few fish are valuable.
Now, just sit and wait and see if we get some good news reported from the satellites.