“We need aid to increase the selectivity of the fishing gear,” he said, to reduce the netting of unwanted species. “We also need to invest in finding new markets for species that traditionally had no value,” but which can no longer be discarded under the new rules.

Part of the challenge for people on both sides of the debate is that no one, not even the European Commission, is certain how much money is flowing to the industry, which employs about 400,000 people, according to Europêche, including more than 120,000 working on 85,000 boats. Oceana, a marine conservation group, estimates that since 2000, the European Union has provided 8 billion euros of subsidies to the industry, with national governments led by Ireland, Spain, Italy and France topping that up with an additional total of 4.9 billion euros.

A scathing report by the French Court of Auditors, leaked in July to the newsmagazine Le Nouvel Observateur, illustrates the lack of transparency. According to the auditors, not even the authorities in Paris know how much public money France is handing out because there is no central record of the aid that is given out across all levels of government. But the subsidies, the report notes, are critical; without them, many French fishing operations “would not be viable.”

Claire Nouvian, director of Bloom Association, a French environmental organization, pointed to a direct link between subsidies and environmental destruction. She notes that the French industry has nine bottom deep sea trawlers, boats that fish in a manner that has been compared to “driving a tractor across the seabed.”

“Just take away the fuel-tax exemption and these boats would already be unprofitable,” Ms. Nouvian said. But the boats also receive millions of euros a year aid directly from the French state, she said. Without the various subsidies, she said, “they’d be bankrupt.”

While the focus of attention is on subsidies to the big operators, even the artisanal fishermen lauded by conservationists gain. Mr. Pennarun, the Breton, acknowledged that if he did not receive a diesel-tax exemption, for example, his fuel bill — currently about 40 euros a day — would rise, and he would have to catch more fish each day just to break even.

In a good week, Mr. Pennarun, who learned the trade from his father, can bring in 250 kilograms of fish, worth as much as 3,500 euros, much of which travels no further than the plates of guests at the Hotel du Bac restaurant here in Combrit. But it is an irregular business. When the weather in Brittany is poor, as it often is, days may pass before he can venture out, and in February and March, when the fish are spawning, he does not go out at all.