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Smolt tagging Spring 2022: Vosso, Aurland, Tysse and Modalen

Spring has arrived, and smolts are preparing for a long and challenging downstream migration through the Vosso and Aurland system. As part of the LaKES project, our team newly finished tagging and releasing a total of 124 smolts (49 trout and 45 salmon) with acoustic tags implemented with predation sensors in the Vosso river, and 61 smolts (34 trout and 27 salmon) in Strandaelva in Aurland.

There are many aspects to be studied from the data we collect during the smolt migration in both Vosso and Aurland; we will study whether the hydropower outlet in lake Evangervatnet in the Vosso system affects the smolt's outmigration. We do this using a dense network of receivers and temperature loggers near the power plant outlet, which gives us detailed information about the smolts migration route through this part of the lake. The power plant will also be off during parts of the period when smolts migrate through the lake to give us a useful comparison of the migration with and without the hydropower. We will also study the proportion eaten by the trout predator in the lakes Evangervatnet and Vangsvatnet (Vosso system). This is analyzed through the implemented predation sensor in the acoustic tag that perceives the fish's orientation, and thus can register if and when the smolt is eaten by a predator; a smolt that has been eaten will have an unnatural orientation when they pass through the digestive system of a predator.

Apart from the LaKES project, our team simultaneously tagged 50 smolts in each of the two hydropower affected rivers Tysseelva and Modalselva. In collaboration with the largest energy company in Western Norway, Eviny, we aim to study the effect of hydropower stations on salmon smolt survival during their outmigration through the stations in hopes of understanding the risk for smolts at these critical migration points.

Check out our gallery for pictures from the whole tagging season!

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