Pieterjan Verhelst

Monitoring Eel

Monitoring Eel in the Westerschelde and the north of Belgium

In Belgium I have met Pieterjan Verhelst. Currently he is working on his doctorate on the mystery that is eel migration. He works in collaboration with the University of Gent, Institute for Nature and Forestry and the Flemish institute for Sea.  Pieterjan invited me in his office at the University of Gent and showed me his research.

He explained that: after eels grow in the in the freshwater bodies of Belgium and its nearby coastal waters the Westerschelde. Eels travel back over the Atlantic to the Gargasso sea to spawn and presumably die. This migration route of over 5000 km is blocked by numerous obstacles: Commercial and recreational fishing, pumping stations, dams, sluices and hydropower, but also water pollution and habitat degradation.  

Pieterjan is one of the Belgium scientists that have established a network of 200 receivers in the Shelde river, Shelde estuary and the Belgium part of the North Sea to track eels.  To know when a eel is swimming by the receiver’s a small portion, that represent the population, of eels is tagged. Pieterjan is on of the scientist that is qualified to operate on eels.  To opperate on eels you first need to catch them out of the water with a net. Then the eels will be individually placed on a small board. The head gets covered to minimise stress and a small incision will be made to put the transmitter in the eel and afterwards the incision will be sewn shut.


Left picture: you can see pieterjan at the operation table. Within minutes the work is done and the eel can be released again.

Right picture: there is a clear difference between female and male. Above the female is measured and under the male

These below skin transmitters make a sound and when picked up by the receivers, data is send to the scientists computer.  Scientist can then determine how eels behave and respond to rainfall, temperature and discharge. Providing environmental legislators and regulators with “know-how” how to operate in peak eel migration periods. Like lowering weirs and opening sluices. These environmental windows are used to help eels to migrate freely. Also we do know now that not all eels travel equally. Eels do not only travel around scotland but also through the english channel. These kind of information and other behavior aspects is continued analysed to tackle obstacles and overcome barriers to preserve eels population.

Monitoring network

This is the established monitoring network of at least 200 Vemco recievers. Stretching from the Shelde river, Shelde estuary and the Belgium part of the North Sea to track eels

Tagging research on eel in Belgium

​​Pieterjan had this beautiful video made, to give more people insight into how eel migrate all the way from Belgium to the Sargasso Sea

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