How climate change is driving dolphins into deadly contact with fishing fleets in the Bay of Biscay
In this article for the French daily newspaper Libération, journalist Julie Renson Miquel reports on new scientific findings that shed light on the surge in accidental dolphin captures along France’s Atlantic coast and the western English Channel. Drawing on a multi-year research project, the article argues that the rise in dolphin deaths since 2016 is closely linked to climate-driven ecological upheaval in the Bay of Biscay.
The findings come from the Delmoges project, conducted between 2022 and 2025 by Ifremer (the French institute for the study of the sea), the University of La Rochelle, the University of Western Brittany and the CNRS (France’s state-funded scientific research body). Speaking to Libération, Clara Ulrich, fisheries expertise coordinator at Ifremer and scientific co-lead of the project, explains that earlier assumptions about weakened dolphin health have now been ruled out. Necropsies show that most dolphins found entangled in nets were in good condition and had full stomachs, indicating they were actively hunting when captured.
The more plausible explanation, she says, is a “profound change” in the region’s ecosystem. Sea temperatures in the southern part of the Bay of Biscay have risen by 0.8°C over the past two decades. At the same time, nutrient levels have declined due to reduced rainfall and a 30 percent drop in flow from the Loire River. This has led to weaker water mixing and lower chlorophyll production, disrupting the base of the marine food chain.
The consequences ripple upward in what scientists describe as a trophic cascade. With fewer nutrients available, plankton production declines, sardines grow smaller, and offshore fish stocks shift. Dolphins, which depend heavily on anchovies and sardines, now have to consume more fish to meet their energy needs. The species they prey on are concentrating closer to the coast, at greater depths and in denser schools. Dolphins have followed.
This altered distribution explains why dolphins are now more frequently found in coastal waters during winter, often in smaller groups. But these areas overlap with gillnet fishing grounds (gillnets are a kind of vertical curtain-like net, weighted at the bottom) increasing the likelihood of accidental capture. Although the total number of fishing vessels and days at sea has declined in recent years, the content and deployment of nets, particularly by small-scale gillnetters with fewer reporting obligations, remains difficult to quantify. Scientists still cannot fully determine why some dolphins manage to escape the nets while others do not.
Emergency winter closures imposed by French and European authorities have shown measurable results. Nearly 300 vessels are required to remain in port between late January and late February, a measure that has reduced average winter strandings from around 4,700 between 2017 and 2023 to 1,900 in the 2024–2025 season. Yet the closures are politically contentious and economically painful for many fishers.
Technological solutions such as acoustic deterrent devices and onboard cameras are being tested, but Ulrich stresses that there is no simple fix. The crisis reflects a broader climate-induced transformation of the Bay of Biscay ecosystem. Science can clarify the mechanisms at work, but the path forward will depend on negotiations between researchers, fishermen, NGOs and policymakers confronting a rapidly changing sea.
The original source article by Julie Renson Miquel ‘Hausse des captures accidentelles de dauphins dans le golfe de Gascogne : L’écosystème de la région subit un changement profond à cause du réchauffement climatique’ was published in French, on January 6, 2026 in Libération.
It is available here.
Libération is a daily national newspaper based in Paris, France. It is widely known domestically and internationally as Libé. It is generally considered to have a centre-left editorial orientation, with a historical commitment to defending civil liberties and minority rights, although its political stance has evolved since its early years.
Summary by ZN
