We are unveiling the survival rates of Atlantic salmon (Salmo salar) smolts during their seaward migration through the lower parts of streams, estuaries and fjords via the use of acoustic and radio telemetry.


  • SMOLTRACK is an EU-wide project coordinated by NASCO. By conducting field research and acquiring new data, SMOLTRACK acts as a platform for salmonid telemetry knowledge.
  • SMOLTRACK allows international lead researchers to come together and share knowledge and best practices, with the goal of establishing an EU strategic salmon telemetry advisory group.
  • SMOLTRACK will help scientists to learn about survival rates of salmon smolts during their migration through the lower parts of rivers, estuaries and coastal areas, providing data on smolt run timing and migration behavior.
  • Ultimately, SMOLTRACK will inform future salmon management and conservation work on an EU level.

What are we doing?


By attaching small transmitters to migrating fish, we are able to follow their movements as they swim downstream. To do so, we deploy listening stations in strategic points and have teams on-site equipped with antennas keeping record of the fish locations.


The tracking allows us to learn how many fish make it out of the river! Transmitters that stay in the same place for a long time or that disappear from the river without reaching the sea have likely been predated.


Understanding the drivers behind the smolts’ survival allow us to develop better management policies which aim to protect this important species and ensure the Atlantic salmon does not disappear from our rivers.


SMOLTrack V started in June 2023 and will end in April 2025.

Research conducted in Denmark, England, Ireland, Spain, Sweden and Northern Ireland through the EU-funded SMOLTrack and related initiatives, have indicated that smolt mortality during the early outward migratory phase from ‘source to sea’ is much higher than previously assumed. Thus, early smolt mortality may be more important than marine mortality. To support this hypothesis, various studies have demonstrated that a reduction in negative pressures (e.g. predation, aquaculture) on smolts in the relevant zone of influence can ultimately boost associated numbers of adult returns.

Therefore, it has become apparent that significant knowledge gaps remain to understand, quantify and partition the principal cumulative factors responsible for Atlantic salmon smolt survival during this critical life stage. In addition to the high mortality for smolts and post- smolts, there is significant mortality in the oceanic phase of Atlantic salmon. It is important to investigate if any part of this mortality may be managed.

The SMOLTrack V project will build on the ongoing and published work of the previous SMOLTrack projects, enabling studies of behaviour and survival rates of salmon during their migration through the lower parts of rivers, estuaries and coastal areas. Thus, the project will provide data on smolt run timing and migration behaviour, as well as generate ocean migration data through nano-DST tagging of smolt.

SMOLTrack V will further expand on the development of a ‘fit for purpose tagging programme’ to be able to follow the return migration of salmon from feeding areas in the Arctic Sea (East Greenland). Methodological refinements will be made to optimize representative results and improve experimental animal welfare. A part of the SMOLTrack V project will be allocated to analysing large datasets collected and publishing some of the overall results and conclusions.