Preparing this year’s work

Team meeting

The SMOLTRACK partners came together in Dublin, Ireland, to discuss the way forward and set this year’s plans in motion! Learn more in IFI’s press release.

New research shows young salmon survival is surprisingly low when migrating to sea

New research shows young salmon survival is surprisingly low when migrating to sea

Inland Fisheries Ireland hosts international scientists as innovative project gives insight into salmon migration journey during International Year of the Salmon

Wednesday, 13th of February 2019: A new study shows low salmon survival leaving freshwater is an important factor in declining European salmon populations, according to early results from a project examining the early migration phase of salmon smolts (young salmon) from rivers across Europe. Leading salmon scientists from Denmark, Spain, Sweden, UK and Ireland are today attending an important meeting in Dublin, hosted by Inland Fisheries Ireland, to mark International Year of the Salmon. The scientists will discuss some of their new findings from the international SMOLTRACK project, the results of which reveal factors in the known decline of salmon stocks.

The SMOLTRACK Project, which is funded by the North Atlantic Salmon Conservation Organisation (NASCO) / EU, aims to help determine the survival rates of young salmon as they move from rivers into the marine environment. Work commenced in 2017 and early results show that survival during movement from rivers to the sea is lower than expected. While it was already accepted that salmon are impacted by a number of factors when they migrate at sea including the effects of climate change, limited feeding opportunities and sea lice induced by fish farms, the low survival rate in river systems which is presenting in this research is a new development. 

The low survival of smolts in some river systems could be attributed to changes in temperature and flow while predators have also been shown to impact on the numbers entering the sea. The survival of smolts varies by catchment and in a bad year, survival of smolts can be three times lower than in a good year. These results will be published in international journals on completion of the research.

The international project sees scientists from each participating country tag salmon smolts with miniaturised acoustic and radio transmitter tags in rivers in their own country, and track their migration journey through the lower parts of rivers, estuaries and coastal areas. This study includes populations in Southern Europe which are most vulnerable to climate change. In Ireland, this work is being carried out in the River Erriff, Inland Fisheries Ireland’s National Salmonid Index Catchment (NSIC).

In addition to the activity in Ireland, tagging is being carried out on the River Bush (Northern Ireland), River Tamar (England), River Ulla and River Minho (Spain), River Göta and River Högvadsån (Sweden), River Skjern and River Storaa (Denmark).  This information will help scientists to understand the survival rates of salmon smolts during their migrations under varying conditions ranging from cooler climates in Sweden to warmer climate in Spain. Already SMOLTRACK is providing new data on the initial migration of salmon smolts which will inform future management and conservation measures for this iconic species.

Dr William Roche, Senior Research Officer at Inland Fisheries Ireland said: “Understanding and comparing early marine survival of salmon in EU waters is a key output of this project in addition to providing data on smolt run timing and migration behaviour. The project has established a European-wide counting, tagging and tracking system to monitor smolts and will also contribute to understanding of the possible impacts of climate change.”

Dr Cathal Gallagher, Head of Research and Development at Inland Fisheries Ireland said: “We have seen a substantial reduction in the numbers of salmon returning to Irish shores in recent decades. This project is examining what is happening to our young salmon as they migrate to sea and what the international community needs to do to help salmon populations. While this research identifies issues in early mortality of salmon, this part of a salmon’s life cycle is where management actions can be targeted to support the future of these salmon stocks. International Year of the Salmon offers an opportunity to share knowledge across the Northern Hemisphere with a view to inspiring action and collaboration with positive effect on salmon survival.”

International Year of the Salmon is a joint world-wide initiative of the North Atlantic Salmon Conservation Organisation (NASCO) and the North Pacific Anadromous Fish Commission (NPAFC) alongside other partners across the globe, creating an international framework for collaborative outreach and research. It is hoped that IYS will raise awareness of what humans can do to ensure salmon and their habitats are conserved and restored against a backdrop of several environmental factors.

For more information about the SMOLTRACK project, visit and to find out more about International Year of the Salmon, go to and .

#yearofthesalmon #salmonandpeople

Fresh from the press!

Published results

A good part of the smolts migrating out of river Skjern faces difficulties in finding their way to the sea. When testing different groups of smolts, our team found that naturalised smolts were more likely to survive the fjord crossing. An unexpected result!

Naturalised Atlantic salmon smolts are more likely to reach the sea than wild smolts in a lowland fjord


The survival rates of three groups of seaward-migrating Salmo salar smolts were investigated in 2005, 2016, and 2017 in the River Skjern and River Omme, as well as in the Ringkøbing Fjord using acoustic telemetry. Ringkøbing Fjord extends for approximately 300 km2, and has a narrow, regulated outlet to the sea. Smolts of three different origins: (a) wild smolts, (b) hatchery-reared smolts previously released at half-year-old, and (c) hatchery-reared smolts previously released at 1-year-old were captured in rotary screw traps and surgically implanted with acoustic transmitters. The progress during seaward migration was monitored with a network of automatic listening stations deployed in the river estuary, fjord mouth and sea opening.

The smolts’ probability of survival in the river was related to their length, with larger smolts being more likely to reach the fjord. Once in the fjord, the probability of reaching the sea was related with the smolt’s group, with smolts previously released at half-year-old being more likely to succeed than wild smolts. However, none of the biometric or behavioural variables explained the difference between the studied smolt groups, masking the potential reasons behind this difference in survival probability.

Overall, approximately 47% of the tagged smolts were registered at the last array of automatic listening stations (i.e., entered the sea), demonstrating the early migration as a critical bottleneck for the local Atlantic salmon population. Ultimately, this limits the number of Atlantic salmon that survive to adulthood and return to River Skjern and River Omme for spawning.

Find the full article here

Fieldwork season is up

Hydrophone deployment

Before the smolt run begins, the SMOLTRACK partners must set up the equipment. After deploying all the hydrophones, our partners will capture, tag, release and follow the Atlantic salmon smolts during their migration to the sea!

Discussing the results

Team meeting

After the fieldwork season has passed and the results were analysed, the SMOLTRACK partners came together in Belfast, Northern Ireland, to discuss the results.

SMOLTRACK Meeting held at AFBI

SMOLTRACK is a European Maritime Fisheries Fund (EMFF) funded project quantifying Atlantic salmon mortality during the early part of the outward migration as juveniles from river to high seas.

Pictured above from left to right: Dr Richard Kennedy (AFBI), Mr Hugo de Moura Flávio (National Institute of Aquatic Resources (DTU Aqua), Denmark), Dr Kim Arestrup (National Institute of Aquatic Resources (DTU Aqua), Denmark), Dr Andy Moore (Centre for Environment, Fisheries and Aquaculture Science (Cefas), UK), Dr Robert Rosell (AFBI), Dr Willie Roche (Inland Fisheries Ireland, RoI), Dr Pablo Caballero Javierre (Galician Government (Xunta de Galicia), Spain), Dr Niels Jepsen (National Institute of Aquatic Resources (DTU Aqua), Denmark), and Dr Dennis Ensing (AFBI).

Over recent decades, the abundance of wild Atlantic salmon stocks has been in decline throughout their range, despite significant management measures put in place both domestically and at an international level.  There is evidence that the initial mortality immediately after migratory juveniles (smolts) enter salt water is very high and that this ‘point mortality’ may explain most of the variation seen in return rates of adult salmon.

This project will determine the mortality of salmon smolts during their migration through the lower parts of rivers, estuaries/fjords and near-shore areas through case studies using acoustic telemetry in rivers in five areas: Denmark, England, Ireland, Northern Ireland and Spain.

The recent (November 7-8) meeting convened at AFBI HQ with representatives from all five areas present, reviewed the results of the first year of the project (2017), and agreed on small changes to standard operating procedures based on the lessons learned in 2017.

In addition a proposal for funding a one-year extension of the project by the EMFF was drafted at the meeting, which has subsequently been granted.


Setting the equipment

Smolt traps

Rotary screw traps allow us to harmlessly capture Atlantic salmon smolts as they migrate, while ensuring that predators do not enter the trap and eat the fish before we can release them!