Ferries to Bilbao provide a chance for everyone to spot playful porpoises, dolphins and whales, and a vital source of information for scientists studying our best-loved marine mammals

The cinema is due to open at 11:30 but there's a long queue by 11:15. Doors open and two hundred people file in. The show is free and key to understanding the bigger show that nature is putting on in the wide blue spaces of the Bay of Biscay. We are on the P&O ferry from Portsmouth to Bilbao. In summer this is routed along the edge of the Bay's continental shelf and the long hours of daylight give an excellent opportunity to see whales and dolphins in their natural environment.

The Bay of Biscay is an important habitat for these animals. The bay is deep, over 3000m, and the steep edge of the continental shelf causes nutrient-rich water to well up, encouraging small animals to grow that provide food for larger ones, all the way up to the whales and dolphins that feed here. A group of dedicated scientists and volunteers work on the Biscay Dolphin Research Project, BDRP. For thirteen years they have recorded observations of numbers and behaviour of the whales and dolphins from every ferry crossing and use these to study the changes taking place.

The data that they collect is valuable because it can start to show how whale and dolphin species are coping with the many difficulties they face. Are numbers recovering now that wholesale slaughter by industrialised whaling has thankfully ceased here? Or are issues with fishing methods, disturbance by sonar testing or climate change threatening their survival?

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Text by Jenny Fowler.

Images by Charles Sterling.