Greenpeace UK activists have placed giant boulders on the seabed in the Southern North Sea Marine Protected Area (MPA) to stop bottom trawlers fishing there, in what the group calls an underwater “boulder barrier”.
The campaigners laid the boulders, each weighing up to two tonnes, over the weekend off England’s east coast. Greenpeace says the barrier effectively closes 116 sq km of the MPA to bottom trawling. The protest coincided with the first episode of Blue Planet III on BBC One on Sunday.
The MPA was designated to protect harbour porpoises. Yet according to Greenpeace analysis of Global Fishing Watch data, bottom trawlers logged at least 37,200 hours of fishing there in 2025, far more than in any other UK offshore MPA.
The Southern North Sea supports nearly 20% of the UK North Sea harbour porpoise population. The site was designated to prevent “significant disturbance” of the species and to keep prey available, but there are no fishing restrictions across most of it. The group says trawling depletes fish stocks leaving porpoises with less food, while the noise disrupts their ability to hunt.
Across all the UK’s offshore MPAs, Greenpeace says bottom trawlers and dredgers dragged gear over a cumulative 55,600 sq km of seabed in 2025, an area 58 times the size of Dartmoor National Park. They spent at least 115,000 hours towing gear along the seabed in these areas, equivalent to more than 13 years of non-stop fishing.
The group has declared the area an “ocean park” and will patrol it in its ship, the Arctic Sunrise, to deter other destructive fishing, including mid-water gear that affects porpoises.