An international collaboration managed to detect the salmon more than four weeks into their harsh journey to northern feeding grounds.
A team of researchers used a remotely controlled ocean glider to track how salmon travel around the Atlantic Ocean.
The SeaMonitor project is led by the Loughs Agency and is funded by the EU’s Interreg VA programme. The ocean glider is an autonomous underwater vehicle that can collect data from a variety of water environments. These robotic explorers can collect data safely and at relatively low cost.
With a wide range of sensors to monitor temperature, salinity, currents and other ocean conditions, the vehicle can also detect tags that have been placed on fish and marine mammals, making it the perfect candidate for tracking salmon.
Over the course of two months, the glider managed to detect four individual young salmon smolts, measuring only 15-19cm, nearly 600km from their origin rivers in Ireland, Northern Ireland and Scotland.
These fish had been tagged between four and six weeks previously using electronic acoustic transmitting tags. Hundreds of other juvenile salmon were tagged as part of both the SeaMonitor project and the West Coast Tracking Project.
A central goal of these projects is to investigate the low survival rates of Atlantic salmon on their journey in the ocean to their feeding grounds in the north Atlantic.
Up until now, most studies tracking salmon have been limited to estuaries and coastal regions because of the need for stationary receivers.
“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,” said Dr Niall Ó Maoiléidigh of the Marine Institute, a principal investigator for the SeaMonitor project.
Gina McIntyre, chief executive of the special EU programmes body, said: “Our shared marine environment is under threat with many species such as Atlantic salmon being endangered. The research that is funded by the Interreg VA programme, is being undertaken by the SeaMonitor project, and will provide invaluable data that can be used to gain a better understanding of the migratory patterns of Atlantic salmon and what is potentially disrupting them.
“This research will inform future environmental protection efforts, on both sides of the border, and is a testament to the partnership-based approach which underpins the Interreg VA programme.”
The use of active tracking technology such as this ocean glider is a developing area. While these techniques have previously been used in the US and Canada, this is the first time it has been used in tracking Atlantic salmon in Europe.
The collaboration plans to use the ocean glider to track other sea animals such as basking sharks as well as generating physical oceanographic data. These data would allow for a thorough understanding of marine life while allowing for the establishment of further marine receivers.