Volunteers across France are undertaking urgent operations to rescue fish from rivers severely impacted by successive heatwaves and extreme drought conditions. Along the Odet River in Brittany, fisher Mathieu Le Bouter and a team of a dozen volunteers are actively catching hundreds of trout and young salmon, not for sport, but to transfer them to safer, more oxygenated waters further downstream. The water levels in sections of the Odet, which flows from the Black Mountains in Finistère for approximately 65km to the Atlantic Ocean, are reportedly barely reaching knee-height.
Le Bouter, representing the Finistère fishing federation, described the situation as “catastrophic,” citing the combination of very high temperatures and critically low dissolved oxygen levels as lethal for fish, especially trout and young salmon. The rescued fish are temporarily held in tanks of oxygenated water before being released 10 to 12 miles downstream, where tributaries contribute to higher water levels. Forecasters anticipate no significant rain and continued high temperatures over the next 10 days, exacerbating the already dire situation for aquatic ecosystems.
The plight of French rivers serves as a stark indicator of the profound impact of extreme heat, intensified by the ongoing climate crisis. France’s longest river, the Loire, is at a historical low, with some sections, including those flowing through Orléans, reduced to mere trickles between sandbanks. The national low water observatory previously reported that 16% of French rivers had dried up, with a quarter of smaller streams becoming stagnant or disappearing entirely, a situation that has seen little improvement due to continued low rainfall since April.
The situation extends beyond regional rivers, with the Seine, vital for Paris’s drinking water supply, now described as being “on life support.” Approximately half of the Seine’s flow is currently being drawn from upstream reservoir lakes and tributaries in Champagne and Burgundy, a measure typically not required until later in the year. In Vernon, Normandy, the Seine’s flow has plummeted from an average of 200 cubic metres per second in July 2025 to 110 cubic metres per second this month. Across France, 99 out of 101 departments are now under water restrictions, with 58 having declared a state of emergency.
The Ministry for Ecological Transition has confirmed that almost a third of river monitoring stations have recorded their lowest levels in two decades, noting a concerning increase in fish deaths linked to rising water temperatures. An emergency agriculture bill, recently passed by the French parliament, aims to facilitate the construction of water storage tanks for irrigation, raising concerns among environmental groups and fishing federations about equitable water resource sharing and potential prioritisation of agricultural needs over conservation efforts. Claude Roustan, president of the national fishing federation, highlighted that rivers are suffering not only from drought and climate change but also from “excessive extraction” for crop irrigation.