When a flotilla of fishing boats sailed out of the south-west English port of Newlyn in 2016 to campaign for the UK to leave the EU, Gavin Addison was one of the fishermen aboard hoping Brexit would herald a new age of plenty for the sector.

Nearly five years and one EU trade deal later, Mr Addison, now working out of Peterhead in north-east Scotland, the UK’s largest fishing port, said Britain’s leaders had failed to deliver on their Brexit promises.

“We thought it was going to help the industry, that it was going to put the fishing back into the control of British fishermen,” Mr Addison said. “We were shafted.”

Mr Addison’s disappointment is widely shared. Across the UK, fishermen complain that the trade deal sealed by prime minister Boris Johnson last month locks in substantial access to British waters for European boats for at least five years and potentially indefinitely.

There is also anxiety in the seafood sector about the permanently increased cost of exports to the EU caused by post-Brexit paperwork, which many fear will outweigh what they see as a meagre increase in the share of fish UK fishermen can catch.

In the first few weeks following the end of the Brexit transition period on December 31, sales to key European markets stalled and the price of many species plunged, forcing boats to tie up in harbour or sail directly to EU ports.

The initial disruption appears to be easing, but some fishermen say Brexit will be remembered as an industry sellout alongside the UK’s accession to the European Economic Community in 1973. The EU’s “common fisheries policy” allocated national quotas according to historical fishing patterns, giving boats from other member states a large and continuing share of the catch from UK waters.

“We’ve been sold down the river again,” said James Cowie, who lands langoustine, haddock and monkfish at Fraserburgh, 18 miles north of Peterhead. Mr Johnson sacrificed British fishing interests to reach a deal with European governments more committed to their sectors, Mr Cowie said. “They’ve got what they wanted,” he said.

“Boris collapsed,” agreed Jeremy Hoskins, a Newlyn skipper who catches crab and lobster inside the UK’s 12-mile coastal zone. Mr Hoskins said the deal, which allows French, Dutch and Belgian boats to operate inside the zone, fell far short of pre-Brexit promises to “take back control”. “The long and the short of it is that we’ve been betrayed again,” he said.

Mr Johnson waves aside such accusations. In parliament this week, the prime minister accepted fishermen currently faced “complications over form-filling”, but insisted they were getting a “huge uplift” in quota.

“By 2026, the fishing people of this country will have access to all the fish in all the territorial waters of this country,” Mr Johnson said, a prospect he likened to reaching the fabled golden city of El Dorado.

“It doesn’t feel like that to my members, that’s for sure,” said Elspeth Macdonald of the Scottish Fishermen’s Federation.

The UK government points out the deal secured extra fishing rights for Britain worth 25 per cent of the EU’s previous catch in UK waters. But Ms Macdonald said the real gains from the changes, being phased in over five years, would be much more limited.

Fishermen would lose access to a system of quota swaps under the EU common fisheries policy and a mechanism for adjusting allowable catches known as The Hague Preference, actually leaving those in Scotland worse off when it comes to more than half of the most important whitefish stocks, Ms Macdonald said.

The UK government said the deal provided for the creation of a “mechanism for voluntary in-year transfers of fishing opportunities” that could make up for the loss of CFP swaps, but the details have yet to be agreed.

In Fraserburgh, skipper Stefan Murdoch said he been told he would have less quota than before, a heavy blow as he is struggling to pay off the loan on a new boat. “Everyone around the harbour is gutted,” he said.

Many UK fishermen are also sceptical of Mr Johnson’s golden vision for 2026, when some transitional fisheries arrangements in the trade deal end.

During negotiations, the prime minister and ministers insisted they would not allow fishing rights in UK waters to be linked to access to the EU single market for British seafood. “They are two completely separate things,” Michael Gove, Cabinet Office minster and the adopted son of an Aberdeen fish processor, said during a visit to Peterhead in 2019.

But the deal explicitly sets out how either side can take “compensatory measures” — including imposing tariffs on seafood imports — if there is any change to “the level and conditions of access to waters” once the transition period expires in mid-2026.

That will give the European Commission leverage to resist UK moves to ban EU boats from British waters. And the trade deal also describes the quota shares at the end of the transition as being in place for “2026 onwards”. A spokesperson for the commission told the Financial Times the deal was clear that any subsequent quota changes would require “mutual consent of the parties”.

“They’ve got us over a barrel,” said Mr Hoskins, the Newlyn skipper.

UK fishermen are not the only ones complaining, however. Expressing sentiments echoed in all EU nations bordering UK coastal waters, Esben Sverdrup-Jensen, chief executive of the Danish Pelagic Producers Organisation, said the deal’s transfer of quotas was a “massive blow” to the Danish fleet. “No doubt there will be fishermen who will go out of business here, and lose their vessels,” Mr Sverdrup-Jensen said.

Many UK producers are still focused on merely getting their seafood to EU markets that value species such as langoustine, crab or monkfish more highly than do domestic consumers.

Exports this week began to flow more smoothly, with leading shipper DFDS restarting “groupage” services where numerous consignments are carried on the same lorry — although deliveries for now still take 24 hours longer than before the end of the Brexit transition.

Donna Fordyce, of trade body Seafood Scotland, said that, even after teething problems were resolved, each consignment to the EU would cost £160 more in certification and other paperwork, a major hit for smaller exporters.

The extra cost of exporting to the EU could lead to a permanent increase in the number of UK boats that take catches directly to ports on the continent.

“We have been informed of vessels heading to land in the markets in Denmark,” said Michael Murray, convener of the Fraserburgh harbour commissioners. “We wouldn’t want to see that as a trend, because the fishing industry is a huge part of the local economy for Fraserburgh.”

In Peterhead, skipper Michael Wilson said he had considered landing his langoustine and whitefish in Denmark, but was deterred by the 30-hour voyage each way.

Tied up in port because of the poor market, he said there were plenty of things he would like to say to Mr Johnson and Mr Gove about their handling of Brexit — but that he did not expect to get the chance to do so in person anytime soon.

“I think they will be scared to show their faces around here,” Mr Wilson said. “There’s a lot of angry people.”