Forsøksdyr: Influence of lakes on the survival of migrating salmon smolts

Godkjenningsdato 19.02.2020

Godkjenningsperiode 18.02.2020-18.02.2022

We propose to advance the understanding of tagged Atlantic salmon smolt survival through lake environments using biotelemetry enhanced by predation sensors. This project builds on a successful pilot study conducted in spring of 2019. Five hundred Atlantic salmon and sea trout smolts will be collected from the Vosso and Aurland river River, anaesthetized with Finquel (MS-222), and tagged with small, lightweight electronic tags that have predation sensors (Vemco, Halifax, Canada). The expected impact of these tags on the smolts is expected to be minimal but tagging and handling can be stressful, which is why we tag under anaesthesia and provide post-operative care. These tags transmit signals on 69 kHz and we will therefore place acoustic listening stations at key checkpoints within the lake. Smolts recorded at the checkpoints will be known to have survived that phase of the lake migration, those detected with the predation sensor triggered will be known to have been eaten and to have not survived. At the end of the summer we will conduct a manual tracking of Lake Evanger using a VR-100 mobile receiver, which can detect and georeference tags that remain in the lake, presumed to be mortalities, at the conclusion of the study. This will give a highly accurate description of the fate of fish released in this study to improve our ability to model the fates of fish released and determine the relative balance between predation and non-predation mortality during the lake migration.

In addition, 30 sea trout predator will be tagged in lake Evanger to be able to validate that predation tags actually work. This can be done by analyzing the behavioral changes of tags using statistical learning approaches on the depth use and triangulation data from the receiver array.

Finally, a holding study will be conducted using 100 salmon smolts in a net pen (4x4x5 meters) in lake Evanger to confirm that salmon smolts do have any post surgical effects on behavior such as issues with buoyancy. The tags used in the holding study will be custom build to include three different tag masses to make inference about the effect of tag load on the vertical behavior of the fish.

This project builds on a pilot study under the principles of reduction, which we now will scale up. We also use a new, smaller tag (V6) compared to earlier tagging studies of salmon smolts, another refinement to our study that will improve animal welfare. The parallel study on brown trout is a refinement that will maximize the value of the tagging results to ensure we can interpret the findings. The holding study will ensure that the effect of tagging will have no adverse effects on the animals.