Silver eels, therefore having reached the age of sexual maturity, were captured in the Cagne, a coastal river in the Alpes-Maritimes, and fitted with transponders.
Understanding how their journey in fresh water is organized would make it possible to preserve it "by stopping the turbines as they pass", explains the Migrateurs Rhône Méditerranée association, in charge.
The operating “table” installed this week on the banks of the Cagne, in Vence, saw particularly viscous patients.
Silver eels, therefore having reached the age of sexual maturity, were captured in this coastal river of the Alpes-Maritimes and equipped with chips, tiny transponders.
“They react with antennas that we have installed along the watercourse and mobile sensors.
At each pass, various parameters are also recorded, such as the flow rate and the temperature of the water.
We hope to be able to determine the mechanisms that trigger their downstream migration to the sea, ”explains Géraldine Verdot of the Migrateurs Rhône Méditerranée association, in charge.
“Critically endangered”
These great travelers, who leave the rivers to reproduce in the Sargasso Sea, in the Caribbean, 7,000 km away, are still very mysterious.
And their populations have been steadily declining in recent years.
The species is also classified as “critically endangered” by the International Union for Conservation of Nature (IUCN).
Understanding how its journey in fresh water is organized would help to preserve it.
"We can already avoid mortality linked to human activity by stopping the turbines as they pass", continues the spokesperson for the association.
A long-term job, started since 2017 with several marking campaigns, and particularly meticulous.
The capture is carried out using electricity by specialists from the Fishing Federation.
"It's harmless," says Alexandre Viguier, environmental inspector at the French Office for Biodiversity, who was on site.
The current disorients the fish which are collected using a landing net.
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Weighed, measured, the specimens are put to sleep.
And the transponders are inserted into the belly through a small incision.
Several hundred eels have already been chipped and numerous surveys have already been carried out.
But the first concrete results should still take a few years.
In the meantime, another threat to this migrant has been identified.
Significant mortality seen in the nearby Wolf River this summer has been attributed to drought.
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