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In this modern era where it is now possible to view real time footage of the surface of Mars from your mobile phone, the spawning migration of European silver eels to the Sargasso Sea, remains unseen despite being one of the largest and longest migrations on the planet.

Agri-Food Biosciences Institute (AFBI) in conjunction with LNFCS have been developing methods to track this migration using implanted acoustic tags.  As the silver eels leave the European coastline this technique allows us to follow them as the tags emit frequent beeps as they travel down river corridors.  Along this journey receiver stations are already in place to listen for these beeps and its associated code, which identifies individual silver eels.

An example of the acoustic tag


Using veterinary ultrasound technology (sonography), the AFBI team have now been able to explore the positioning of the tag following insertion and to demonstrate the lack of injury or displacement of any internal organs within the silver eel.

Veterinary ultrasound equipment


Control specimens held over a 20 day period also showed that none of the silver eels “dropped” (or excreted) the acoustic tags, adding additional validity to the telemetry studies (tracking animal movement) of silver eel migration.

Image of a tag in a Lough Neagh silver eel.


Results from previous tagging studies on Lough Neagh silver eels identified “beeps” from individuals that had swam down the Lower River Bann, out the Bann estuary at Castlerock, turning left, with their signals  detected along the Donegal coast as they migrated westwards into the Atlantic Ocean.