By ITV News Multimedia Producer Lewis Denison
The issue of fish is a sticking point in Brexit talks.
From January 1, French fishermen may lose their access to British waters which would have a huge impact on their industry.
Likewise, exports of UK-sourced fish to the rest of Europe could be affected.
The EU has previously called the UK's position on fishing “simply unacceptable”, while Britain's chief negotiator has in the past accused the European Union of having "frozen" progress by refusing to budge on the issue.
There are other stumbling blocks in negotiations, such as road haulage and state aid, but both sides have repeatedly said fishing is where some of the biggest gaps lie.
And negotiators are running out of time to mullet over. The transition period finishes at the end of the year, meaning the UK will trade with the EU on World Trade Organization tariffs and terms if a deal is not reached and ratified by both sides before then.
So why has fishing - an industry that accounts for just 0.1% of the UK economy - left Brexit talks in such choppy waters, and why are both sides being so stubborn?
A summary of the issue
As part of any deal, the EU wants the UK to remain signed up to the Common Fisheries Policy, which, in essence, is an agreement that member nations do not control their own territorial waters with regards to fishing, and each country has access to all European fishing waters.
Each year, the EU decides what quota of fish each country is allowed to catch from waters around Europe.
The UK's fishing waters are some of the most bountiful in Europe and European fishing vessels catch catch a lot of their fish there, meaning EU negotiators are under significant pressure to maintain the current arrangement.
On the other hand, the UK says it would be an infringement of its sovereignty - a main issue in the Brexit referendum - if the EU continued to have control over Britain's fishing waters.
On top of that, British trawlermen say the Common Fisheries Policy is unfair and blame a decline in the UK's fishing industry on the EU's ability to assign foreign quotas in UK waters.
A lot of Europe's fish are swimming in UK waters
British fishers say they are treated unfairly by the Common Fisheries Policy, which the UK entered in 1970, because European vessels take a lot more fish out of UK waters than they do.
The EU is heavily reliant on the north east Atlantic - which includes UK waters - for its fishing industry, with 67% of fish landed by EU vessels coming from that patch of water in 2017, according to the UK government.
In the same year, 35% of fish caught by EU vessels in the north east Atlantic came from UK waters.
In comparison, just 13% of fish caught by UK vessels came from EU waters.
For some fishing nations in the EU, such as Greece, the UK's water is of little concern, as they take most of their fish from the Mediterranean Sea, however, for at least five European countries the UK's territorial water is no small fry.
Denmark, the Netherlands, Ireland, France, and Germany - the latter two being some of the most powerful within the EU - all catch around a third or more of their north Atlantic fish in UK waters, according to think tank The UK in a Changing Europe.
There's a lot more than just cod...
You might be surprised to learn that British staple cod is not necessarily the most sought after fish in UK waters.
In fact, 95% of cod eaten in the UK comes from outside British waters, according to seafish.org, because cod stocks around the UK are severely depleted.
For EU nations fishing in UK waters, the most valuable fish are herring, mackerel and sole, according to the British government, but they are by no means the only fish caught.
Denmark, in 2017, caught around 90% of all North Sea whitebait in UK waters and Holland caught almost 80% of North Sea sole, as well as the largest share of plaice.
France took a majority of the monkfish, hake and whiting from UK waters, while Irish vessels took most of the horse mackerel.
It will be no surprise that Britain takes the lion's share of North Sea cod, around 60% and around 90% of North Sea Haddock.
How much fish are UK vessels allowed to catch - and who decides?
British fishers would provide a simple answer to this question; "not enough" - and by looking at the way quotas are divided among countries, some might argue they are right.
Each year, fisheries ministers meet to decide how much of particular fish stocks can be caught within the EU - the Total Allowable Catch (TAC).
Ministers are advised by scientific bodies on what the TAC should be each year, however the Institute for Government says the recommendations are often disregarded.
While the TAC can vary from year to year, the percentage each country gets of it does not.
Once the TAC is decided by ministers, it is divided into quotas for individual EU members which were decided in the 1970s.
Quotas are designed to prevent overfishing of fish stocks.
Each country receives a fixed share of the TAC based on how much of a particular stock each country was fishing during a reference period between 1973 and 1978, according to the Institute for Government.
UK fishers say this is not fair or representative of their fishing needs, because a lot has changed since the 1970s.
Following Brexit, the UK wants to renegotiate its fishing quotas but the EU wants the fixed shares to remain in place permanently.
An example of what British fishers think is an unfair system is that France has 84% of the quota for cod in the English Channel, compared to the UK's tiny 9%.
According to britishseafishing.co.uk, European fishers catch up to 173 times more herring, 45 times more whiting, 16 times more mackerel and 14 times more haddock and cod from UK waters than Britons do.
The fishing industry is just 0.1% of the UK's economy...
Campaigners who supported Brexit argued fiercely that sovereignty over the UK's fishing waters would be a huge reward for leaving the EU.
While fishers are supportive of the UK regaining control of its fishing waters, Britain's fishing industry accounts for a "negligible proportion" of GDP, according to The UK in a Changing Europe.
The think tank says only 0.1% of gross value added (GVA) in the UK economy comes from the catching sector.
Despite fishing being such a big issue in the EU referendum, just 0.04% of the UK's jobs in 2018 were in the fishing sector - about 12,000.
This is no where near enough to harvest all the fish stocks currently caught in UK waters.
Brexit supporters argue sovereignty over fishing in UK waters would encourage companies to invest more in British fishing.
They also say the UK could sell quotas to other countries, if the UK was unable to harvest all of its own stock.
In summary, the British fishing industry is tiny at the moment, but supporters say having full control over it would allow it to flourish.
What are 'UK waters'?
Coastal countries have what are known as "territorial waters", the definition of which has changed variously over the centuries.
Once upon a time some countries argued it was the distance a cannonball could be fired from the coast.
Nowadays, after the introduction of the 1982 UN Convention on the Law of the Sea (UNCLOS), countries were allowed to claim an ‘Exclusive Economic Zone’ (EEZ) across 200 nautical miles from the coast.
Many countries around the world have control over their own EEZ, however in the EU, EEZs are regarded as a common resource, termed ‘EU waters’.
All EU vessels have a right to fish in EU waters, provided they hold a quota allocation for the stock of fish they want to catch, according to the Institute for Government.
UK fishers want the 200nm around the British Isles to be reserved for their ships.
Will an agreement be reached?
Judging by the gulf between the two sides, it is difficult to see how a deal on fisheries will be reached.
If the Brexit transition period ends on December 31 without a deal, then the UK would have its wish of full control over its fishing waters, but it wouldn't have unfettered access to EU markets.
The EU wants the UK to accept its position on fisheries before allowing talks to progress "in any other area".
The UK's chief negotiator David Frost said the European Union is making it "unnecessarily difficult to make progress" with its position.
Following the latest round of Brexit talks, the EU's chief negotiator Michel Barnier said it "seems unlikely" a deal will be reached before the deadline.