An Italian NGO has published footage taken on intensive fish farms that appears to reveal troubling practices in an industry that so far has largely gone unregulated.

Shocking footage of intensively farmed fish has emerged in Italy which raises questions about working practices on aquaculture farms for supermarket produce, and which has sparked fresh calls for regulation.

Unlike mammals, fish have almost no legal protections in the EU and the images, secretly filmed in 2017 and 2018, represent the first investigation into Europe’s “factory farms” for fish.

The video shows separate schools of sea bream, sea bass and trout being scooped out of cramped nets, before they are dumped into plastic containers, and left to slowly asphyxiate. Many spend their last moments flapping helplessly on the floor.

Some of the fish that survive endure a suffocation that can apparently last up to an hour on slabs or containers filled with slush and ice in the slaughterhouse.