Forty French fishing boats attack five British boats in the Channel. Stones and smoke bombs are thrown. Rude words are exchanged in two languages. The British retreat.

UK defends scallop boats after clashes with French vessels Read more

Similar incidents have been happening for 15 years – or arguably for the last 900 years. The rights and wrong are complicated. Yesterday evening the French boats were undoubtedly the aggressors. They put to sea not in order to fish, but to harass the English and Scottish boats that had entered “their waters”.

It was foolhardy of the French fishermen, but they do have reasons to be exasperated. The latest outbreak of the Baie de la Seine scallop war should be seen in the context of Brexit and the deep uncertainties and exaggerated expectations encouraged by simplistic and vague UK plans to reclaim “our seas” and “our fish”.

Ironies abound. In the this dispute, British boats are asserting their right to fish in French waters even when they are closed to French trawlers. This right depends on EU rules, but pre-dates the EU fishing policy.

In any case, the row is not just about France v Britain. It is also about Big Boats v Small Boats, and the ecological damage caused by modern methods of industrial-scale fishing.

First, some facts. The clashes took place in “French waters” – that is to say about 15 miles from the French coast at a point where the Channel is about 100 miles wide, well beyond any possible legal definition of British waters. There were 40 French boats and five British – but the French boats were tiny and the British boats were large.

The French are furious that British boats don’t observe the summer closure of the ​​scallop fishery to conserve stocks

Since so much has been said about European boats “pillaging” British fishing grounds, it is worth dwelling on the fact that this was one of the many cases in which UK-registered boats depend on access to “European waters”. The scallop grounds off the Norman coast are among the richest in the world. The scallops – or coquilles Saint-Jacques – dredged by UK boats are mostly sold back to the continental market.

Under the terms of the common fisheries policy, British boats do have a right to dredge scallops up to 12 miles from the French shoreline. The French fishermen have never disputed that right.

They do, however, accuse some British boats of fishing inside the French 12-mile limit. They are also furious that British boats don’t have to observe the summer closure of the scallop fishery (from 15 May to 1 October) imposed 15 years ago by French authorities to conserve stocks.

Since this is a national regulation, independent of the common fisheries policy, British and Irish boats do not have to respect it. In recent years the British and French governments have negotiated a bilateral agreement. Small British boats could enter the “closed” French waters for a limited number of “days at sea”.

No such agreement has been reached this year. Worse, from the French point of view, the relatively small British boats that used to come over from Newlyn and Brixham in the West Country have been joined by mega-boats from Scotland. One of the vessels attacked on Tuesday night was the Honeybourne III from Peterhead, a Scottish vessel belonging to a Canadian-owned company.

The French fishermen complain that the large boats, with heavier dredging tackle and freezing equipment, are capable of hoovering up enough scallops in one day to keep local fishermen in work for a month. They also claim – and this is disputed – that the large ships leave the seabed like a “ploughed field”.

War on the seabed: the shellfishing battle Read more

One British crew leader says, off the record: “Dredging is an awful kind of fishing. Not all fishermen want to be dredgers. It leaves the marine environment in a terrible mess.”

The aggressively pro-Brexit Fishing for Leave organisation, which represents a relatively small number of British fishermen, says the Seine Bay dispute reveals French “hypocrisy”. European fishermen have been pillaging “60%” of the fish in British waters for the last three decades, Fishing for Leave claims. Why should they object to a few British boats entering French waters?

In truth, the Seine Bay war is a storm warning. It shows what may happen on a wider scale if a hard Brexit removes all common rules for management of fisheries in European seas. It is also a useful reminder that some British boats rely on European rules for access to their prey – and the European single market to sell their produce.

Above all, as one leading British voice pointed out: “It shows how complicated fisheries policy is. We have access to those waters because of historic rights that go back well before the common fisheries policy. The same applies to French and other fishermen in our waters. Those rights will not disappear with Brexit, whatever some politicians and fishermen’s leaders may say.”

• John Lichfield is a former EU correspondent based in France