London (CNN) Putt-putting out into the Portsmouth channel on England's south coast, the small vessel is soon swallowed by the early morning fog.

To the uninitiated, the mist appears to cloak any landmark, bar the occasional cormorant marking time atop a buoy, but the boat's captain isn't fazed.

"You're a hunter but you can't see anything. It's like hunting bears with a blindfold."

This is how Matt Varndell describes his day at work fishing for clams. However, given its political dangers, economic risks and the uncertainty that still haunts the process, "blindfolded bear hunting" sounds like a metaphor for Brexit and the UK government's attempts to leave the European Union (EU).

While it only accounts for 0.12% of the UK economy , fishing has been at the heart of the rhetoric around Brexit. Paraded by the pro-Brexit camp as an icon of EU regulation strangling a quintessentially British industry and way of life, fishing has had an outsized presence in Brexit-related headlines.

But from seabed to table top, the wider economic "food chain" of British seafood -- catching, trading and serving fish -- highlights the Gordian Knot of issues that have bedeviled the UK's efforts to divorce from the EU.

The catch

Varndell has worked at sea since he was a teenager, when his father first took him out on his boat, the Versatile.

"It was the freedom of fishing that attracted me to this job. The unknown," he said. "Being at sea, the sea water gets in your blood."

This is not a career for the faint-hearted, however. Each tow of his dredge along the sea floor yields just one or two clams all morning. A good tow may only drag up a dozen. At the end of the day he splits his catch 75-25 with his deck hand, Richard, netting between £400 and £450 ($522-$587) in total.

As he zigzags his boat through the waters near Portsmouth, Varndell rails at the suffocating hold he feels regulations have on his work.

"The legislation has gone beyond reasonable and the fleet is getting smaller and smaller by the year," he said.

British inshore fishing is regulated by local Inshore Fishery and Conservation Authorities (IFCA), who state their aim as balancing "social, environmental and economic benefits to ensure healthy seas, sustainable fisheries and a viable industry." Although a UK body, they enforce EU directives on managing the environment.

"Of course fishing has to be sustainable otherwise I'm out of business," Varndell said, but added that IFCAs are more focused on conservation than on balancing fishermen's needs with the environment.

"It's making a very difficult job almost impossible."

The wider fishing industry has complained about EU controls on what they can catch, with boats forced to throw back into the sea dead fish that exceed their allocated quotas. Many also argue that Brits' share of the quota from British waters -- only 36% in 2016 -- unfairly favors larger foreign vessels able to exploit rich UK fisheries.

Varndell refuses to blame European fishermen. "If I had the opportunity and a vessel big enough to go to France and exploit their fishing grounds, which yielded a lot more catch than what my fishing grounds do, I would do it," he said.

"There was a promise of taking back control of British waters," he said of the 2016 pro-Brexit referendum campaign. According to one pre-referendum poll, 92% of UK fishermen supported Brexit . "It wasn't the only reason I voted to leave but it was one of the main issues."

The trade

From the coast, fish flows through the hands of traders like Eric McLeod in British fish markets. His Portsmouth-based firm, Viviers, buys fish from local fishermen along the southern English coast as well as from abroad.

"I don't sell fish just in the UK. We export to mainly Spain, France and we used to sell a lot to Italy," he said.

Due to local tastes, the UK imports 70-80% of the fish Brits eat (such as cod) and exports up to 80% of its catches (more diverse produce such as shellfish).

McLeod has long thought that EU membership was bad for Britain, even protesting at sea when the UK joined the European Economic Community in 1972.

But for others, Brexit is a worrying prospect.

If the UK enters a new customs agreement with the EU, at borders where goods currently flow unimpeded by inspections, new checks and paperwork could mean significant delays, especially as the system is newly introduced.

"If [UK traders'] product is very fresh or even still alive, any delays reduce the freshness, the shelf-life and therefore the value and, if the delay is long enough, could potentially render the product valueless to the purchaser," said Hazel Curtis, Corporate Relations Director at Seafish, a public body supporting the UK seafood industry.

McLeod shrugs off such concerns, buoyed by his experiences dealing with EU fish traders. "They do not want to be without trading with the UK," he said. "If another country wants our fish and I'm sure they will, they'll have to pay the increased charges."

"I think there's been too much political argument within all parties," he said. "Unless they've worked in the fishing industry, they wouldn't have a clue."

The sale

The plates of Cornerstone restaurant, tucked away in a gentrifying corner of post-industrial London and specializing in seasonal produce, is the end of the journey for some British fish.

Consequently, Tom Brown, the establishment's young chef-owner, feels the ripples of concerns upstream the fish "food chain." Brown buys all of his seafood directly from local merchants or fishermen in Cornwall and is very conscious of how difficult life is for people like Varndell under EU regulations.

But potentially increasing import taxes driving up price of the foreign wine he buys and a post-Brexit financial fallout hitting customers' pockets weigh heavily on the restauranteur.

"We're a small, family-operated-style business. We don't have anything else behind us to absorb any sort of massive hit," Brown said.

"If people don't have a lot of disposable income, what's the first thing that goes out the window? Eating out at restaurants."

But one possible Brexit side effect could quite literally change the face of his business.

"All of the staff that we have that work on the front of house are non-British citizens," Brown said.

Cutting immigration was a rallying cry of the pro-Brexit campaign in 2016 and there is little certainty on how leaving the EU will affect the current rights of EU citizens to live and work in the UK. Some 75% of waiters and waitresses in the UK hospitality industry come from other EU countries

"Jobs in the front of house are, by British people, seen as a stopgap, something that you do at university or looking for another job. On the continent it seems much more like a career choice," he said.

"A restaurant manager is France is regarded in the same way as a bank manager so it's taken very seriously."

The UK government has promised that the 3.7 million non-British Europeans already living in the UK would be allowed to stay post-Brexit but Brown worries about the cost of any potential work visas for his staff.

"If suddenly we had to help all our staff pay tons of money in visas, if we had to lose a lot of staff really quickly it would be a massive hurdle for us to get over in a restaurant," he said.

"The thing is more the uncertainty," Brown said. "I mean I probably know as much as the government about Brexit, which is nothing."

With just over a month to go until "Brexit Day" -- Britain's planned departure from the EU on March 29 -- uncertainty stains what the EU-UK divorce will actually look like, how it will work or whether it will happen.

From port to plate, wading through fishing rights, trade taxes and immigration controls, looking at British seafood it's obvious why.