| Summary: | Gjelland, K.Ø., Johansen, N.S., Orell, P., Kytokörpi, M., Grønmo, S. & Holter, T. 2024. Downstream migration success of Atlantic salmon smolts in River Tana, 2021. NINA Report 2396. Norwegian Institute for Nature Research. Several of the salmon stocks in the Tana watercourse have had a severe decline over the last two decades. The status of the stocks in the upper headwaters are currently very low. This has caused the Finnish and Norwegian management to agree on closing all Atlantic salmon fishery in the Tana watercourse and the Tana fjord from 2021. There is a concern that that predation on out-migrating smolt may have a much stronger impact on population growth when the population is small as compared to when the population is large. This may hinder the expected salmon population recovery during the fishing moratorium. There is a pressure to have predator culling on smolt eaters such as the northern pike and the sea trout. The effect of such potential measure is not known, as the effect of predation itself on Atlantic salmon population growth is not known. The pattern and survival of the freshwater phase of the smolt migration have not yet been studied. The aim of this study was to investigate migration pattern and survival of radio tagged smolts, and to identify bottle necks on the 240 km long route from the tagging site to the ocean. To achieve this, we planned to tag 100 smolts, and track them on a network of 22 fixed radio receivers as they migrate down the watercourse. The smolt migration is normally at its peak between mid-June and mid-July in the Tana watercourse. The smolt trap was initially placed in the small tributary Geaimmejohka on 22nd of June. No salmon smolts were caught there until the 28th of June, and the trap was then moved to the much larger tributary Kárášjohka. From 3rd – 7th of July the trap was fishing successfully, and a total of 65 salmon parr/smolts were caught, and 27 smolts (14.3 cm length, standard deviation ± 8.2 cm) were tagged and released. During the first days of July ...
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