Female dolphin dying younger in Bay of Biscay

Scientists carrying out tests on over 700 common dolphins who died after being stranded on shores along the Bay of Biscay over two decades have discovered that the average age of the females dropped significantly over time, a trend that could result in a fall in population numbers.

Experts were able to determine how old the dolphins were from their teeth, information that then revealed the average age of stranded females decreased from 24 to 17 years over the length of the study from 1997 and 2019.

This kind of drop in the lifespan of so many females could have a critical impact on population growth, with fewer adult females resulting in lower birth rates. This also poses a threat to the wider marine ecosystem.

The Bay of Biscay, which is situated off the west coast of France and stretches down towards northern Spain, is a popular destination for dolphins in winter because of the warm and nutrient-rich waters which attract sources of prey such as anchovies and sardines. The presence of these small fish also makes the location a target for many fishing vessels.  It is estimated that 9,000 common dolphins die in nets in the region each year, and in 2024, following pressure from us and other groups, the French government agreed to close the Bay of Biscay to fishing for one month every January.

We have been campaigning for more action to be taken to reduce the harm caused to whales, dolphins and porpoises from entanglement in nets, including in this area. Together with environmental groups we have been urging both the French and Spanish governments to urgently adopt adequate measures to prevent these unnecessary deaths every winter, something they are legally required to do under EU environmental law.