News November 2023

Yet another piece of eel mystery unravelled

To help the critically endangered European eel recover, it is important to better understand their complex life cycle. Indeed, the 6,000-kilometre migration to their breeding grounds in the Atlantic Ocean is one of the greatest mysteries in the animal kingdom. We still do not know exactly where they reproduce and how long the migration takes.

Together with the Flanders Marine Institute (VLIZ), we investigated eel migration in the North Sea. This was done within the European LifeWatch project. We already knew that eels leaving Belgian rivers towards their breeding grounds take two routes: a southern route via the Channel or a northern route around the UK.

Recent research revealed that eels use the tides to migrate energetically efficient: when the seawater flows towards the Atlantic Ocean, the eels move into the water column. If the current changes direction, they stay close to the bottom, probably because it allows them to stay out of the strong current. Once in the ocean, they swim at depths of almost 1,000 m during the day and continue their journey at around 300 m at night.

This research teaches us how eels navigate and orient themselves in the sea. This knowledge can give us a better understanding of the human impact on eel migration in the sea. In rivers and canals, we already know the bottlenecks well, but most of the migration takes place in the sea, and there we are still in the dark.

Pieterjan Verhelst

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Image above: the two migration routes eels use (INBO)


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