On Thursday, tensions flared in waters off the Channel Island of Jersey as France and the United Kingdom mobilized naval vessels to defend fishing rights in the area. While it may seem strange for two democratic countries to engage in displays of military force, given the lack of wars between democracies, this type of maritime engagement is quite common.

My research explains why clashes at sea occur between democratic countries. Even among allies, competition for fishing resources often triggers diplomatic and militarized conflicts.

What are France and the U.K. fighting about?

The two countries have historically contested islands and maritime areas in the English Channel. English ownership of the Channel Islands was settled by the International Court of Justice in 1953, while arbitration in 1977 and 1978 resolved remaining disagreements over the continental shelf and maritime boundaries. Under that agreement, island authorities such as Jersey could exercise jurisdiction over fisheries in the 12-nautical-mile territorial sea area.

The Jersey dispute came about because local authorities changed the conditions for fishing licenses in their territorial waters: French boats now have to demonstrate a history of fishing in the area to receive a license. Britain’s exit from the European Union in January created an opportunity for Jersey officials to alter existing fishing arrangements because the U.K. left the common fisheries policy that previously established rules for E.U. members.

French fishermen responded by sailing dozens of boats in the area in protest, and a French trawler rammed a British boat. The French government defended French fishing rights with a naval show of force and a threat to cut off electricity to the island.

Are democratic fishing disputes common?

While democracies don’t escalate crises to all-out war, they often engage in lower-level conflicts that involve naval displays, like moving government vessels to an area or using militarized force — like seizing another country’s fishing vessel. My research with Brandon C. Prins catalogued the diplomatic issues at stake in militarized disputes between democracies from 1946 to 1992. We discovered that 43 percent of these conflicts involved offshore fishing, oil and mineral resources, just like last week’s clash between France and the U.K.

My research with Kelly Daniels examines whether this pattern extends to diplomatic disagreements over maritime areas, even where no uses of military force occur. We analyze data on maritime conflicts between 1900 and 2010 in the Americas, Europe and Asia, collected as part of the Issue Correlates of War (ICOW) project, which I co-direct with political scientist Paul Hensel.

We find that pairs of democracies are much more likely than autocracies to experience diplomatic conflicts over maritime areas involving sovereignty — like drawing an Exclusive Economic Zone boundary — or resource rights, like access to fishing grounds. Today’s French-British fishing row is thus part of a repeating pattern of clashes at sea such as the U.K.-Iceland cod wars, the Canada-Spain turbot wars and the tuna wars between the United States and Ecuador and Peru.

In all of these clashes, democracies defended marine sovereignty and resources with force. Our research also shows that escalation is more likely if contested fishing grounds contain migratory stocks because the movement of fish stocks across boundaries results in fishermen crossing such lines to catch fish and vessel seizures by neighboring countries.

Why fight over fish?

Fishing and offshore oil/mineral resources are very important for many countries’ economies. High levels of economic development in democratic countries create more opportunities for large-scale fishing fleets. It’s no surprise that countries with large fishing fleets like the United States, the United Kingdom, Spain, Japan, Norway and Peru are frequently involved in fishing disputes.

Our research suggests that maritime clashes are more likely between similarly sized economies, a dynamic we have seen when comparing the French and British economies over time. I also find that countries with greater naval capabilities initiate more diplomatic conflicts with their coastal neighbors to defend their interests at sea — France and the U.K. rank among the top 10 global naval powers.

Can UNCLOS and the E.U. help resolve fishing disputes?

The French-British dispute over Jersey fishing waters was resolved quickly through peaceful negotiations. My co-written research shows that countries that have jointly ratified the U.N. Law of the Sea Convention (UNCLOS) treaty, such as Britain and France, are more likely than nonmembers to settle disputes through bilateral negotiations, mediation or international courts.

France and the U.K. also share membership in several other organizations, such as NATO, the United Nations and the Group of Seven, providing them with more opportunities for active conflict management by these international institutions. Brexit severed one of those cooperative ties, but France and Britain have foreign policy connections through many other organizations, suggesting that any future fishing disputes will be resolved quickly and peacefully, as in this case.

While the U.K. departure from the E.U. created the recent dispute by changing fishing license requirements for French fishermen around Jersey, my research with Holley Hansen and Stephen Nemeth suggests that the E.U. hasn’t been particularly effective at managing fishing disputes. European Court of Justice judgments to settle maritime disputes have 100 percent compliance rates. However, E.U. nonbinding settlement attempts like mediation or multilateral negotiations to resolve maritime issues produced successful agreements only 10 percent of the time. Other regional organizations such as the Organization of American States have a better conflict management track record — OAS-led mediation efforts produced agreements to resolve maritime disputes 72 percent of the time.

The future of democratic fishing disputes

The 2021 Jersey fishing dispute ended quickly, but it is part of a larger pattern of repeated clashes at sea between democratic nations. Declines in global fish stocks and rising sea levels may generate more maritime disputes in the future. While such disagreements have the potential to escalate, the norms and institutions that have preserved the democratic peace to date are holding steadfastly.

Sara Mitchell (@sbmitche) is the F. Wendell Miller Professor of Political Science at the University of Iowa and author of six books and more than 50 journal articles and book chapters.