To track Atlantic salmon movements from river to sea and back, millions of salmon have been tagged over the past fifty years as part of scientific international tagging programmes.
Recently ICES published a Cooperative Research Report documenting fifty years of marine tag recoveries from Atlantic salmon.
Programmes have included tagging of smolts, migrating out from their freshwater nurseries to the sea and their recaptures in high-seas fisheries off Norway and the Faroes, in coastal fisheries around Greenland and upon return to home waters. Other studies included tagging of adults caught at sea and their subsequent recaptures in home waters in coastal fisheries and by anglers.
"Tagging and related data efforts are crucial as scientists seek to improve understanding of wild Atlantic salmon distribution and migration at sea and the underlying causes of mortality. This is particularly important given that, despite initiatives that have mitigated some declines, abundance of the species has continued to drop in the last two decades," explained Niall O'Maoileidigh, Marine Institute.
Tagging has included various types of external "floy tags" focusing in the past 20 years on coded wire tags, less than 2 mm in length, delicately implanted into the nose cartilage of fish.
This report not only documents the history of these tagging programmes for posterity but also investigates migration patterns, timings, return rates, their changes and patterns.
"Mass marking techniques still provide basic information on survival rates, exploitation rates and migration in general. However, with current technology e-tagging is becoming far more informative, giving rise to information not only of the "when and where" of tagging-releases and recaptures, but also on the movements, routes, depths and behaviors in-between" added O'Maoileidigh.
With 2019 flagged as the International Year of the Salmon (IYS: https://yearofthesalmon.org/) there is no better time for ICES to release this report, setting the benchmark and stage for future investigations into these remarkable diadromous fish.
Link to report here