Brexit: Why is there a fishing row in the Channel between the UK and France?

France has detained a British scallop trawler in the port of Le Havre and fined another UK fishing vessel.

The latest post-Brexit row over fishing waters has once again revived a French threat to British energy supplies.

And the UK has accused France of moving towards a breach of international law and promised an "appropriate and calibrated response".

Sky News looks at what's sparked the latest tensions in the Channel and how the row might escalate.

What's happened?

A scallop vessel named Cornelis, owned by Macduff Shellfish, was boarded by French authorities on Thursday and ordered into the port of Le Havre, the company said.

Macduff said its vessel was "legally fishing for scallop in French waters" and claimed it was being used as "another pawn in the ongoing dispute between the UK and France" over the implementation of post-Brexit fishing agreements.

The French sea ministry said in a statement that it had fined two British fishing vessels and "immobilised" one of them overnight.

They added that the fines resulted from new boat checks that are "part of the tightening of controls in the Channel, in the context of discussions on licences with the UK and the European Commission".

Annick Girardin, France's minister of the sea, said that one vessel was fined "for refusing to let the check take place", while the other vessel "didn't have the right to fish in the zone because it didn't have a licence".

The UK government has insisted the detained vessel did have a licence issued, but suggested it may have subsequently been withdrawn from a list of licensed vessels for "unclear" reasons.

What are the post-Brexit agreements on fishing?

Under the terms of the Brexit trade deal, which came into force on 1 January, EU access to UK waters and UK access to EU waters is now managed through a licensing system for fishing vessels.

Known as the Trade and Cooperation Agreement, the Brexit trade deal will also see UK fishing boats end up with a greater share of fish from UK waters, with part of the EU's previous share being transferred during an "adjustment period" until 2026.

Previously, when it was a member of the EU, the UK was part of the bloc's Common Fisheries Policy, which gave all European fishing fleets equal access to EU waters.

What do the UK and France disagree on?

According to the French government, the UK has only issued half the fishing licences that France believes it "is entitled to".

But Environment Secretary George Eustice has said the UK has licensed 98% of the EU vessels that applied for access to UK waters.

"Since 31 December last year, the UK has issued licences to fish in our exclusive economic zone to 1,673 EU vessels," he told MPs.

"This includes 736 French vessels, and 121 vessels have been licensed to fish in the UK six to 12 nautical mile zone, of which 103 are French."

Conservative MP David Duguid, who is the prime minister's fisheries envoy, suggested the dispute centred on French vessels not being able to provide the evidence required to obtain a licence.

He told Sky News: "I think there are many vessels on the French side who previously had access [to UK waters] but didn't necessarily build the track record.

"Or at least they can't provide the evidence of that track record which is required to obtain a licence."

Ms Girardin disputed the UK's claim, saying that only 90% (rather than 98%) of EU vessels who applied were granted UK licences.

"Obviously, the missing 10% are for the French," she added.

What about Jersey and Guernsey?

To complicate matters, the Channel Islands of Jersey and Guernsey are British Crown Dependencies and responsible for issuing their own licences to EU vessels to fish in their territorial waters.

The government of Jersey, an island that sits only 14 miles off the French coast, said the issuance of licences was a "complex, evidence-based process" that it was continuing to approach "with good faith".

They said that "further progress" has this week been made "on the outstanding applications from French vessels for licences to fish in Jersey's territorial waters".

What has France threatened?

Ms Girardin has described the dispute as "not war" but "a fight", adding: "The French fishermen have some rights, an agreement has been signed.

"We must have this agreement implemented, we have fishing rights, we must defend them and we defend them."

The French minister said her country does not yet have "the number of licences we expect", especially from Jersey.

And, as such, she warned of retaliatory measures being "progressively implemented" from next month.

Asked if France could revive its previous threat to cut off power to Jersey - which receives 95% of its electricity from France through undersea cables - Ms Girardin said it "wouldn't be serious to say we cut the electricity".

But she added that sanctions could include the raising of tariffs.

Other retaliatory measures being suggested by the French include:

• Banning British fishing vessels in some French ports
• Reinforcement of customs and hygiene controls
• Routine security checks on British vessels
• Reinforcement of controls on lorries to and from the UK

How did the UK respond?

Responding to the French threats, Mr Eustice said: "We believe these are disappointing and disproportionate and not what we would expect from a close ally and partner.

"The measures being threatened do not appear to be compatible with the Trade and Cooperation Agreement or wider international law and, if carried through, will be met with an appropriate and calibrated response."

Could the Royal Navy be brought in again?

In May this year, in a previous episode of the post-Brexit fishing dispute, the UK deployed two Royal Navy vessels to Jersey amid concerns of a possible blockade of the island by French boats.

But Number 10 has said, as yet, there are "no plans" to once again send the Royal Navy to protect British vessels in the Channel.

Have there been fishing disputes before?

Prior to the UK's membership of the EU's Common Fisheries Policy, there had been what were known as the "Cod Wars" between Icelandic and British fishing vessels in the late 1950s to 1970s.

These violent clashes were sparked by Iceland asserting control over the seas surrounding the island.

The Royal Navy became involved by escorting British trawlers.

In what was dubbed the "Scallop Wars" in the summer of 2018, tensions erupted between French and British boats around the Baie de Seine waters.

What about the French election?

Our Europe correspondent Adam Parsons has suggested next April's French presidential election could be a factor in the current fishing dispute.

"Emmanuel Macron is aware that, with a presidential election on the horizon, he wants to shore up his support in northern France, where fishing is a potent topic," he said.

"He also thinks that picking a fight with Britain has political value. The AUKUS submarine deal infuriated Macron and, after years of Brexit wrangling, there is mistrust of Westminster politicians.

"Macron is keen to portray himself as the de facto political leader of the EU and, right now, having a row with Boris Johnson won't do him any harm."