This article is part of POLITICO’s Westminster Survival Guide.

Europe’s small fishing sector is making a big splash in Brexit negotiations.

The fishing industry, together with agriculture and forestry, accounts for just 1.6 percent of the total goods and services produced in the Europe Union every year. And yet, despite the fact that it’s such a tiny economic sector, officials in Brussels have made reaching a deal on fisheries conditional to the future relations between the two sides.

For the European Union, the fear is that not reaching a deal that favors its fishermen would devastate coastal countries that deeply depend on access to British waters. The Commission, therefore, declared during a briefing with EU diplomats last week that there must be a “direct link” between trade negotiations and fisheries talks.

The U.K., meanwhile, has turned the issue into one of national sovereignty — a symbolic way for the country to assert its new independence from the bloc its people voted to leave.

In short, the EU27 wants to retain the same access its fishermen have now, while the U.K. wants to be treated like any other non-EU country.

Neither side will likely be willing to budge at the start, setting the stage for a major fight given the short 11-month time frame to reach a deal before the end of the year.

“Fisheries has always been politically important,” said Emiel Brouckaert, director of Belgian fishing industry group Rederscentrale. “It’s symbolic. Just like Ireland, it’s about territory, and granting each other access to each other territories.”

Small fish, big pond

Only 178,000 people work in Europe’s fishing industry — just 0.03 percent of the total population. About 12,000 of them are British, which is around 0.02 percent of the U.K. population. The fishing industry in the U.K. only accounts for 0.1 percent of the country’s GDP.

At the same time, European fishermen are highly dependent on access to the seas around the U.K.: 42 percent of all fish caught by EU fishing crews are plucked out of British waters, according to the European Fisheries Alliance.

That figure is even higher for fishermen from nearby coastal countries like Belgium and the Netherlands.

“The water that is in front of our coast is basically a post stamp. Two-thirds of our fishing happens in U.K. waters,” said Johan Nooitgedagt, president of the Dutch Fishermen’s Association. “You can imagine the mood among Dutch fishermen is very bad, as it’s theoretically possible that U.K. waters would be closed off.”

Flemish Minister of Fisheries Hilde Crevits said that the “fish industry is a small sector, but it’s a sector that we don’t want to lose. Our fishermen can’t move their activities since the share of their catch from British waters is so big. As minister of fisheries, it is one of my jobs to help the sector survive.”

That’s why the EU wants to directly link the fisheries agreement to the entire trade negotiation.

“If there would be a separate negotiation on fish, we would not have such a strong negotiation position toward the U.K.,” said Brouckaert of the Belgian fishing industry organization.

It’s a big political bet to make the entire trade deal dependent on a minor economic sector that is only relevant for Western coastal countries. The EU-U.K. Political Declaration states that both sides should try to reach a new fisheries agreement by July 2020, but it does not explicitly say whether that deal is considered part of the overall trade talks.

Yet the proposal to connect the two issues went down without a fight, according to an EU diplomat who was at last week’s Brexit briefing. “The discussion on fisheries was very straightforward and relatively short. All EU countries seem to be on the same page on this.”

Tough talks

The link could make talks with the U.K. even harder than they are already set to be, especially since British Prime Minister Boris Johnson has insisted his country “will take back control of our fishing waters.”

“On the one hand, we are told that we’ll become a third country when we are leaving the EU,” said a U.K. official in Brussels. “We fully agree with that. On the other hand, we have been told that fisheries is such a difficult and complicated area that you have to maintain the status quo. We don’t accept that, since we are leaving the EU, which makes us an independent coastal state. As we are leaving the EU, U.K. waters will no longer be EU waters.”

That doesn’t mean the U.K. will simply close off its waters and catch as many fish as possible. Rather, London wants to be treated the same as other third countries, such as Norway, which negotiates its terms with Brussels each year.

“We are very happy to get into a detailed discussion about sustainable fisheries, managing shared stocks and access to our waters,” the U.K. official said.

That likely won’t fly with Brussels, which fears the consequences for poor fishing villages. During the Brexit briefings for EU diplomats last week, the Commission stated that the objectives of the negotiations would not just be “sustainability and conservation,” but also “socioeconomic.”

The EU hopes to gain an upper hand in fish talks by tying them to trade negotiations, in which Johnson has said he will push for an ambitious deal of “zero tariffs, zero quotas.”

“You have to use the weight of the general trade negotiations and what importance that has for the U.K. to get a good agreement also in the fisheries,” said Jensen, Denmark’s fisheries minister, in December.

But the U.K. could also try to use the EU’s reliance on its waters to its advantage to win its own “trade-offs” from Brussels, which EU Trade Commissioner Phil Hogan said last week would be most likely to happen at the end of negotiations.

“The EU will be seeking concessions on fishery access, and the U.K. will very probably be seeking concessions on financial services,” Hogan said.

At that point the EU would have to make rapid decisions about what to include and what to leave out in a trade deal before the deadline. The unity the EU27 has shown so far on fisheries could be tested as countries start to weigh up their own national interests.

If the two sides don’t reach a deal by the end of December, and Johnson continues to refuse to extend the transition period, the U.K. could theoretically cut off access for EU vessels to its waters. This could slash the net profits for European fleets in half and lead to job losses for at least 6,000 people, according to the European Fisheries Alliance.

The U.K.’s waters would exclusively become its own again under the U.N. Convention on the Law of the Sea. But those principles also require countries that share maritime borders to manage shared fish stocks, meaning Brussels and London will have to start up yet another round of negotiations, which both sides will be reluctant to do.

Or as the European Fisheries Alliance puts it: “We’re all in the same boat.”