Switzerland and France join forces to save a rare fish

Searching for the apron in the River Doubs @Pro Natura /Arthur Lehmann

An endangered fish has inspired French and Swiss efforts to restore habitat for wildlife along the River Doubs, which borders both countries. But these measures may have come too late to save one of the river’s native species, the apron.

The apron (Zingel asper) is a brown-beige, slender-bodied fish in the perch family, known in the Swiss canton of Jura as the Roi du Doubs (King of the Doubs). Because of habitat destruction and pollution, the species is critically endangered in Switzerland and endangered in France.

Both the Swiss and French governments have been trying to save the fish for some time. In 2016, the Swiss federal and cantonal governments adopted plans to restore the ecosystemsExternal link connected to the Doubs.

Switzerland adopted these measures after conservationists filed what became known as the “Apron complaint” under the Bern Convention, a binding international treaty aimed at saving European species from extinction.

But the help may have come too late. In 2012, researchers spotted 52 aprons in the River Doubs, the highest number in 15 years. But their numbers continued to dwindle and the last sighting was in 2023. Swiss public television, RTS, filmed a night-time search in the summer of that year.

The last remaining apron, a female found in Switzerland in 2023, was briefly in the Aquatis aquarium in the Swiss city of Lausanne, where it bred with French aprons before being transferred to the Citadel Aquarium in Besançon, France. The resulting offspring are now at Aquatis and Basel Zoo.

Could they survive if they were reintroduced into the Doubs? Aline Chapuis from the ‘Doubs Vivant’External link nature protection group has her doubts. “We won’t know until we try,” she says.

The Swiss female fish will now be part of French efforts External linkto breed Zingel asper in captivity and release them into the wild.

French aprons bred with Swiss: Aquatis aquarium, Lausanne swissinfo.ch

Why all the fuss about a little fish?

The fate of the apron is a sign of the collapse of biodiversity in an area of exceptional natural beauty.External link Only 14 of Switzerland’s 71 species of fish are not considered threatened.

“So in terms of fish fauna, we can see that biodiversity is in a bad way in Switzerland,” Chapuis says. “It may be starting with the disappearance of the apron in the Doubs, but it may continue with other species of fish. We have to take it as a warning.”

Ecologists point out that biodiversity isn’t just about saving species – it’s about maintaining life-supporting systems for the entire planet. Diverse ecosystems are more resilient to environmental changes, such as climate fluctuations and natural disasters. Diverse genetic poolsExternal link within populations enable species to adapt to changing climates more swiftly through natural selection.

Bern Convention shakes things up

In the 2011 “Apron complaint”, Swiss nature groups told the Bern Convention Standing Committee in Strasbourg that the fish faced serious threats. Agriculture and discharges from wastewater treatment plants had polluted the Doubs and left excess minerals and nutrients in the water.

In 2013 the Standing Committee recommendedExternal link that Switzerland and France strengthen the control of all emissions and discharges of pollutants into the waters of the Doubs and the Loue in eastern France, a tributary of the Doubs, and that Switzerland restore connectivity between critical habitats of the apron. The committee stressed cross-border coordination as a key element. Accordingly, French and Swiss researchers are now sharing data on water quality, fish populations and environmental changes.

In 2017 the two countries signed an agreement to improve the joint management of three hydroelectric dams on the Doubs. The regulations have helped to protect spawning grounds by reducing disruptions caused when the dams release water.

What action is needed now?

Rebekka Reichlin, head of communications at the federal environment ministry, says most of the action plan measures have been implemented and are “effective”. A wastewater treatment plant in the Swiss town of Le Locle is under construction, and problems with weirs in the municipalities of Ocourt in Switzerland and Bellefontaine in France are being addressed. Weirs are a concern for the apron and other fish as they can alter the flow of a river, impede fish migration, and affect temperature and the transport of sediments.

In December 2024 the Standing Committee of the Bern Convention welcomed the “gradual and sustainable” implementation of the Swiss plan for the Doubs. Nevertheless, the committee again urged Switzerland and France to step up their collaboration. The Swiss national action plan has been extended to 2030. France is now on its fourth action plan, which also expires in 2030.

The “Doubs Vivant” group has called for concrete measuresExternal link to protect the watershed from potentially harmful agricultural and forestry practices, and for closer collaboration between France and Switzerland on water quality, as “pollution knows no borders”.

One little fish might have disappeared from Swiss waters forever, but the efforts the apron inspired will benefit other species. As Chapuis points out: “It’s always worth working towards an ecosystem that is as close as possible to a natural state. It’s good for the environment, it’s good for us.”

Fish species threatened worldwide

Switzerland and France are not alone in facing extinction of fish species due to human activity.

The Chinese paddlefish, native to China’s Yangtze River, has not been seen since 2003. Overfishing and dams caused its demise.

The Black Cisco was once plentiful in the Great Lakes in North America, but it has not been sighted since 2006. Overfishing is partly to blame.

In 2024 two species of migratory Amazonian catfish were placed on an international protection list, victims of overfishing and the construction of hydroelectric plants on rivers in the Amazon.