The ability to track free-swimming salmon juveniles has been extended hundreds of kilometres into the open ocean using advanced robotic technology.
As part of the EU INTERREG VA-funded SeaMonitor project, Dr Ross O'Neill of the Marine Institute and Kieran Adlum, P&O Maritime, tested a remotely operated ocean glider along the steeply sloping area of the shelf edge some 130km north-west of the Scottish Hebrides.
The torpedo-shaped device, equipped with an acoustic tag detector, was deployed from the RV Celtic Explorer on 16 April during the 2021 Irish Anglerfish and Megrim Survey.
This is the first time such active tracking technology has been applied to Atlantic salmon in Europe.
During its two-month mission, the glider successfully detected four individual juvenile salmon smolts measuring only 15-19cm, nearly 600km from their home rivers in Ireland, Northern Ireland and Scotland.
These fish had been tagged between four and six weeks previously with electronic acoustic transmitting tags along with hundreds of other juvenile salmon as part of the SeaMonitor project as well as the West Coast Tracking Project, a partnership between the Atlantic Salmon Trust, Fisheries Management Scotland and Marine Scotland, EU INTERREG VA-funded COMPASS project and Agri-Food Biosciences Institute (AFBI) research initiatives.
One of the main aims of these projects is to investigate the persistent low marine survival of Atlantic salmon in the early stages of their oceanic migration to feeding grounds in the North Atlantic.
The four fish originated from the River Burrishoole in Co Mayo, the River Bann in Northern Ireland and the rivers Clyde and Awe in Scotland.
Up to now, most tracking studies had been limited to estuarine or coastal areas due to technology limitations and the need for stationary receivers.
According to Dr Niall Ó Maoiléidigh of the Marine Institute and principal investigator for the SeaMonitor project: “The detection of these fish confirms the importance of the shelf edge in this amazing journey, as the faster currents associated with the steep slopes most likely act as an aquatic transport system facilitating the northward migration of these tiny fish through a very harsh environment.”
Prof Colin Adams of the University of Glasgow and principal investigator for the SeaMonitor Project added: “This study shows that tracking salmon over considerable distances at sea can be achieved which is crucial for research into highly migratory marine species especially where mortality may be occurring far from the shore.”
Dr Ciaran Kelly, director of fisheries ecosystems and advisory services at the Marine Institute, said: “The use of the glider to track the movements of even very small fish has been clearly demonstrated and this will encourage the use of autonomous underwater vehicles to improve information on many marine species of animals which may be endangered or threatened without interfering with their natural migrations.”
The SeaMonitor project is “breaking the boundaries of research into the marine migration journey of the iconic Atlantic salmon”, said Loughs Agency chief executive Sharon McMahon.
“This innovative research will help to identify migratory routes and factors influencing salmon survival at sea, providing data to inform future research and decision making.”
The glider is part of the SeaMonitor integrated cross-jurisdiction major network of acoustic receivers, robotic underwater vehicles, satellite tracking and passive acoustic receivers in European waters and its use will be extended to track cetaceans, basking shark and skates as well as to collect physical oceanographic data.
When combined, the data will enable a holistic view of the regions mobile marine species and will prove invaluable to the regions managers, as well as establishing an integrated network of marine receivers for future applications and extended monitoring.
Match-funding for the project has been provided by Northern Ireland’s Department of Agriculture, Environment & Rural Affairs (DAERA) and the Department of Housing, Local Government and Heritage in Ireland.
For more information about the project visit the Lough Agency’s SeaMonitor portal or follow the project on Twitter at @SeaMonitor1.
