One hundred years after disappearing from Swedish waters, scientists in June began a 10-year project to reintroduce the Atlantic sturgeon to a cleaned river in the west of the country.
At the start of the project, 100 juvenile sturgeon transferred from a farm in Germany were released into the waters of the Göta älv River.
"To be the person who has the opportunity to reintroduce a species that has gone extinct nationally - that's a huge gift," biologist Dan Calderon, who originated the idea, told AFP.
"It's probably the best thing I've done," Calderon said.
The project, called "Storens aterkomst" (The return of the sturgeon), is led by the Swedish Fishermen's Association, which is working with several universities and the Gothenburg Natural History Museum.
The species lived in the river until the end of the 19th century, but gradually disappeared due to overfishing and pollution.
According to the University of Gothenburg, today the river is much cleaner, and conditions are again suitable for the sturgeon, which can reach over 5 meters and weigh over 600 kilograms.
"I feel full of hope because this is something really good that we are achieving here, and it's a good start," said Linnea Jagrud, project leader.
The effect of reintroducing the fish into the river ecosystem will be carefully studied by the researchers.
Sturgeons feed from the bottom of the river, which helps enrich the sediments in the riverbed with oxygen, which is beneficial for the small organisms that live there.
Large sturgeons can also serve as a host for other species, such as the sea lamprey.
"One hundred doesn't make a population, but with continued work we will build a strong population and continue to work to restore the river and restore the riparian area outside of it," Jagrud said.
Like salmon, Atlantic sturgeons - recognizable by their sharp noses and scaleless skin - spend the first few years of their lives in fresh water.
When it is large enough to tolerate the salinity, it migrates out to sea in search of food and then returns to fresh water to spawn.
But it can take up to 10 years for the river dweller to reproduce.
"It will therefore be necessary for the sturgeon to gradually recover each year over a decade to form a population capable of surviving without human help," Jagrud explained.
To map the river's characteristics and its suitability for the species, acoustic telemetry receivers have been placed underwater and transmitters have been placed on some fish to track their movements.
"These types of receivers are deployed all over Europe, in European waters and also abroad," Jagrud said.
"This means that they are all connected to the same tracking network, meaning that if 'my' fish goes to Portugal, Spain, France or the UK, the European tracking network will report back to me and I will know that my fish, released in June 2024, made it all the way to Italy," she continued.
On 18 June, a crowd gathered on the shores of Göta älv to witness the historic return of the endangered species.
"This is where many northern countries have had their reunions and great feasts," said Miguel Odhner, mayor of the riverside town of Kungalv. He explained that fish often featured on the menu of royal guests, which at the time was caught in abundance.
"Now it's time to give back to nature," Odhner said. | BGNES
