Thanks to its decontamination for the Paris 2024 Olympic Games, fishermen are observing the return of biodiversity in the Seine

The holding of the Olympic Games is not the only issue. The decontamination of the Seine also makes it possible to create more favorable development conditions for fish and birds.

A new Olympic event is taking place in the Seine on Friday, August 9, with the marathon swim. After the women, the day before, over 10 kilometers, it’s time for the men to take on the same distance. Beyond the events organized in a river that, despite doubts, is much cleaner than before, after years of work to clean it and especially 1.5 billion euros spent, the legacy of the Games is also a Seine that is more welcoming to biodiversity.

Hubert is passionate about fishing. For 20 years, this hydrobiologist walks the banks of the Seine, like this August day, in Levallois-Perret, for predatory fishing. Fish that he then releases.“There the perch came to give a kiss, but it didn’t get stung…”, comments this member of the Union of Fishermen of Paris, at the end of an hour of fishing marked by false hopes. If he did not catch any fish that day, Hubert was able to have a good overview of the biodiversity of the river, which is richer every year. “We saw roach, pike, chub, perch and bleak, he describes. It’s still rare to come up empty-handed these days in the Seine, in Paris.” The fisherman indicates having already caught, “exceptional perch of more than 40 centimeters, or pikeperch that approach a meter”. He has only recently seen such catches, in such numbers.

“Really, you can have miraculous catches from autumn onwards. It’s not unusual to catch thirty fish in one or two hours.”

Hubert, fisherman in the Seine

to franceinfo

The fish are becoming more numerous, confirms Léo Lelièvre of the Maison de la pêche et de la nature, located right next door. : “In Paris, in the 60s and 70s, when the water was very polluted, there were only three or four species of fish that survived. Today, we really have several dozen. At least thirty, in the Paris basin.”

All species are exhibited in aquariums at the House of Fishing and Nature. We find catfish, bullfish, carp, and even pike, which have been back in Paris for a few years. “We have a small pike of about thirty centimeters which is very sensitive to pollution, continues Léo Lelièvre. This is really the number one indicator of relatively healthy water.”

He greets “the fact that there are treatment plants with larger storage facilities” .“Treat more water” allows to have “less nitrogen, less organic matter and therefore more oxygen in the water.” What helps fish live better : “Between 2010 and 2020, we saw a decrease of 30% of nitrogen in water leaving sewage treatment plants. That’s huge !,”underlines Léo Lelièvre.

Birds, including kingfishers, are also more numerous. To further enrich this biodiversity,“We must continue what we are already doing”concludes Léo Lelièvre. Investing in treatment plants, continuing to connect homes to the wastewater network, building other reservoirs to prevent sewers from overflowing, like the one in Austerlitz. All of these works have accelerated significantly in recent years, in the run-up to the Olympic Games.