Were there only 3 species of fish left in the Seine in the 1970s, compared to almost 40 today, as Amélie Oudéa-Castéra claims?

According to the resigning Minister of Sports Amélie Oudéa-Castéra, the Seine was so polluted in the 1970s that there were only three species of fish left living there, compared to nearly 40 today. This statement is true.

It’s a topic that has been much talked about since the start of the Paris Olympics: the cleanliness of the Seine. The mixed relay triathlon was finally maintained on the morning of Monday, August 5, despite the announcement by the Belgian Olympic Committee that one of its triathletes fell ill after diving into the river for the women’s event on July 31. However, according to the resigning Minister of Sports Amélie Oudéa-Castéra, the investment to clean up the Seine was worth it. According to her, we must look at the state of the river over a much longer period of time. “In the 1970s, there were only three species of fish left in the Seineshe reports. Today, there are almost 40 that have been restored.”

The minister’s statement is true, given that we are talking about the Seine in the Paris region. Some sources mention only three species present in the Seine in the 1970s, others go as high as four. Thus, according to the Fédération de Paris, des Hauts-de-Seine, de la Seine-Saint-Denis et du Val-de-Marne pour la pêche et la protection du environnement aquatique, at the time there were carp, roach, eels and bream in the Seine. The head of French ichthyofauna at the Muséum national d’histoire naturelle Gaël Denys mentions roach, bream, carp and river perch.

In the 1970s, the Seine was very polluted. More than half of the wastewater, from toilets, showers, and industries, produced by the Paris metropolitan area was dumped into the river without any treatment. Because of this pollution, there was very little oxygen in the water and few fish could live there. Moreover, at that time, the Seine was considered “almost biologically dead”This is what the SIAAP, the public sanitation service for the Paris region, reports in a report.

Since the 1980s and 1990s, the region has made great efforts to clean wastewater before discharging it into the Seine. To do this, it sent this water to treatment plants, including the one in Achères in the Yvelines. “Emissaries”, a kind of water highway, were built to bring this water to the treatment plants. We also learned how to better depollute the water by removing not only carbon but also nitrogen and phosphorus. And it worked. In the 1990s, still according to the SIAAP, there were 14 species of fish in the Seine in the Paris region.
Today, there are 36 in this same portion of the river and 37 in the Marne, its tributary.