Three knocks on the cabin door: "Half past midnight!"

It's time for the team from Sea Shepherd, a group dedicated to protecting the world's marine life, to start their nightly patrol.

Six volunteers set out in a semi-rigid boat to monitor and film the operations of a nearby fishing fleet.

They already know that increasing numbers of dead dolphins are washing up on France's Atlantic beaches.

Between January and April 2019, 1,200 small cetaceans washed up dead on the beaches of France's west coast - 880 of them common dolphins
Between January and April 2019, 1,200 small cetaceans washed up dead on the beaches of France's west coast - 880 of them common dolphins AFP / NICOLAS TUCAT

Their mission is to document the damage these vessels are doing to the local dolphin population.

Since December 22, Sea Shepherd's Sam Simon, a converted meteorological observation vessel, has been the base for these nightly patrols in the Bay of Biscay off the southwest coast of France.

The volunteers can spend hours waiting as the trawlers winch up their enormous nets.

But their presence is not welcome.

Members of marine conservation organisation Sea Shepherd hold a rally at the Trocadero in Paris, in front of two dead dolphin taken from the beaches of the Atlantic coast. They are calling for an end to the fishing methods that are believed to have killed
Members of marine conservation organisation Sea Shepherd hold a rally at the Trocadero in Paris, in front of two dead dolphin taken from the beaches of the Atlantic coast. They are calling for an end to the fishing methods that are believed to have killed the mammals. AFPTV / Viken KANTARCI

"Bunch of scavengers!" shouts one crew member from a trawler just a few yards away.

Although the trawlers are fishing for sea bass, Sea Shepherd wants to record whether dolphins -- or other cetaceans -- have also been caught in their nets.

Earlier in their campaign, they posted a video of two dolphins being hauled aboard a fishing trawler: one had apparently already drowned, but the other, still alive, was struggling to escape the netting.

Increasing numbers of dead dolphins are washing up on France's Atlantic beaches, and activists say fishing trawlers are to blame
Increasing numbers of dead dolphins are washing up on France's Atlantic beaches, and activists say fishing trawlers are to blame AFP / LOIC VENANCE

Operation Dolphin By-Catch aims to warn the public about the issue -- and pressure the authorities to take action.

They argue that industrial trawling is devastating the local dolphin population, with hundreds washing up dead on the west coast of France every year.

"The problem has been going on for 30 years, but there is a kind of omerta," says Lamya Essemlali, President of Sea Shepherd France.

Volunteers on the Sam Simon, a converted meteorological observation vessel, record how many dolphins turn up in trawler nets
Volunteers on the Sam Simon, a converted meteorological observation vessel, record how many dolphins turn up in trawler nets AFP / LOIC VENANCE

And according to the experts, the numbers are rising.

"2019 was the year of all the records," says marine biologist Helene Peltier of the University of La Rochelle on France's west coast.

Between January and April, when the toll is highest, 1,200 small cetaceans washed up dead on the beaches of France's west coast -- 880 of them common dolphins.

Of those they autopsied, 80 percent showed signs of collisions with fishing boats: cuts, broken teeth, battered heads, asphyxia.

Sea Shepherd's patrols are not always welcomed by the trawlers
Sea Shepherd's patrols are not always welcomed by the trawlers AFP / LOIC VENANCE

And because most dead dolphins sink or are carried off to sea, they estimate that in all, 11,300 dolphins died in 2019.

"The fishermen go to the zones where there are fish -- the dolphins too," says Yves Le Gall, head of the acoustic service at Ifremer, the French oceanographic research institute.

A 2016 report by University of La Rochelle's Pelagic Institute warned that fishing threatens the dolphin population in the Bay of Biscay, estimated at 200,000.

Peltier says that human activity is already killing more than 1.7 percent of the population -- the endangerment threshold.

"The animals that are killed accidentally are in good health," she noted.

In the first decade of the century, scientists and fishermen collaborated to develop acoustic devices known as "pingers" to warn off dolphins.

Although they succeeded in reducing the accidental captures, the pingers were not widely adopted.

The 2016 Pelagic Institute report appears to have prompted a greater sense of urgency.

"A real dynamic developed, with concrete actions" that galvanised fishermen, says Thomas Rimaud of Pecheurs de Bretagne (Brittany Fishermen).

"It's no fun for fishermen, capturing dolphins," says Hubert Carre, head of the National Committee for Maritime Fishing (CNPMEM).

Most recently, the fishing ministry has been pushing to have all trawlers in the Bay of Biscay fitted with the pinger devices. France is in talks with the European Union to ensure that all boats, not just French ones, must comply.

And the main trawler fleet, responsible for four percent of accidental captures of dolphins, has agreed to accept observers on board.

Ifremer meanwhile is working on more effective pinger devices and reflective equipment to make the massive nets more visible to dolphins.

But for Sea Shepherd, technological fixes only go so far.

They want a complete ban on all indiscriminate methods of fishing, such as trawling -- they have already called for a consumer boycott.

"Impossible," given the economic importance of the French fishing industry, says Carre at CNPMEM.

The authorities have banned the more damaging methods of trawling off some parts of the coast. But there are other boats fishing these waters, and it is difficult to tell how much damage they are doing, Peltier says.