Endangered species

Collaboration uncovers new details of the marine migration of Atlantic salmon

Written by Oceanographic Staff

Coordinated efforts into establishing a new online International PIT Tag Database for wild salmon and trout has recorded its first success. A tiny PIT (Passive Integrated Transponder) tag from a wild juvenile salmon released in a French river (Scorff) in April 2022 has been subsequently detected during routine screening at a commercial fish processing plant in Iceland in July 2022.  Further investigation revealed the PIT tag was part of a haul from a mackerel fishing vessel some 200km north-east of Iceland on 25th July.

This adds new and important detail to the knowledge base around salmon marine migration and individual pathways. Taking the most likely migration route for this fish suggests that it has been covering an average of around 34km per day whilst in the sea before being recaptured.

This knowledge would not have been possible to obtain without the online database developed by the UK’s Missing Salmon Alliance (MSA) and Norwegian Institute of Marine Research (IMR). It follows coordinated efforts between these partners, the Icelandic Marine and Freshwater Research Institute (MFRI), the Directorate of Fisheries in Iceland, the French National Research Institute for Agriculture Food and Environment (INRAE), the French Observatory of Research on Diadromous Fish in Coastal Rivers (ORE DiaPFC) and the International Council for the Exploration of the Sea (ICES) working group on North Atlantic salmon.

PIT tags are increasingly being used in salmon and trout research and management programmes in countries around the North Atlantic, as in French long-term monitoring programs on index rivers. They are also routinely used in the stock assessment of commercially important marine fish species like mackerel and herring, requiring tag detectors to be operated at fish processing plants.

The International PIT Tag Database provides a new resource for recording and quickly comparing tagging and recapture data from multiple sources. It has the potential to match tag and detection details to provide new information on the migration and fate of Atlantic salmon and trout whilst at sea.

Colin Bull, principal investigator at the Missing Salmon Alliance, said: “This is essentially free opportunistic knowledge, and is an important demonstration of the power of international data sharing and collaboration. With PIT tagging being routinely undertaken for salmon and trout research in many countries, and the widespread use of tag detectors in commercial fishery operations I’m hopeful this is just the tip of the iceberg. With luck this result will encourage others who routinely use PIT tags for research to register their tags on the database and contribute to this effort”.

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Written by Oceanographic Staff

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