The barrier has been created in the Offshore Brighton marine protected area in the English Channel, which the organisation said was one of the UK’s most heavily bottom trawled protected areas.
The boulders, dropped by activists aboard the Greenpeace ship Esperanza, will close 55 square nautical miles of Offshore Brighton – one fifth of its total area – to bottom trawling.
Celebrities including Thandie Newton, Hugh Fearnley-Whittingstall, Paloma Faith, Bella Ramsey, Mark Rylance, Jarvis Cocker and Ranulph Fiennes have signed their names to boulders.
Bottom trawlers spent 3099 hours fishing in Offshore Brighton in 2019, according to Greenpeace.
Offshore Brighton was established in 2016 to protect its seabed habitat, the organisation said.
Currently, there are no full bottom trawling bans in any of the UK’s offshore protected areas.
Data released by Oceana last year revealed that 97 per cent of the UK’s offshore marine protected areas are being bottom trawled.
After Greenpeace built a similar boulder barrier in the Dogger Bank Special Area of Conservation, the UK government announced new bylaws which would totally close the Dogger Bank and South Dorset protected areas, and partially close two other protected areas, to bottom trawling.
Greenpeace said this action demonstrated ‘some political will, following Brexit, to properly protect the UK’s offshore waters’.
This was previously difficult because introducing restrictions on fishing operations in offshore UK waters required agreement from other EU member states, the organisation said.
But Chris Thorne, an oceans campaigner at Greenpeace UK and one of those aboard the Greenpeace ship Esperanza, said the move ‘barely touches the tip of the iceberg in terms of what is needed to save our oceans’.
He said of offshore Brighton: “It exists specifically to protect the seabed, but bottom trawlers spend thousands of hours each year ploughing this sensitive habitat.”
Hugh Fearnley-Whittingstall said: “I’m proud to have had the chance to put my name on one of these boulders.
“This action will play a small but significant role – and far more than our Government has so far done – to actually protect Offshore Brighton in a pragmatic and effective way.”
Greenpeace is calling on the government to ban bottom trawlers and supertrawlers from fishing in all of the UK’s marine protected areas.
A Department for Environment Food & Rural Affairs (DEFRA) spokesman said: “The UK is a global leader in the fight to protect our seas, with our ‘Blue Belt’ of Marine Protected Areas extending across 38 per cent of UK waters.
“The Marine Management Organisation’s current proposals to introduce byelaws to safeguard four of our precious offshore Marine Protected Areas demonstrate our commitment to achieve a healthy, thriving and sustainable marine environment.
“Everyone needs to act within the law. As there is a live investigation underway, we are unable to comment further on Greenpeace’s activities.”