Chinese paddlefish and wild Yangtze sturgeon have officially been declared extinct by the International Union for Conservation of Nature (IUCN), drawing to a close a decades-long effort to save both river fish species.

The IUCN's latest list of threatened species, published on its website on Thursday, showed that 100 per cent of the world's remaining 26 sturgeon species are now at risk of extinction, up from 85 per cent in 2009.

"The assessments are based on new calculations [that] show their decline over the past three generations to be steeper than previously thought," the conservation group said, adding that the reassessment had also confirmed the extinction of the Chinese paddlefish.

Both the Chinese paddlefish and the Yangtze sturgeon — one of the oldest vertebrates in the world that has existed for more than 200 million years — were common species in the Yangtze River basin, which has been plagued by heavy shipping traffic, overfishing, and water pollution.

The extinction of the two species became one of the most discussed topics on China's Weibo — a social media platform similar to Twitter — with users urging greater environmental protections.

"A biological population that lived for 150 million years was actually made extinct by modern civilisation? I want to ask: Where is our civilisation?" one user posted.

The Chinese paddlefish was one of the world's largest freshwater fish species and could grow up to 7 metres in length. The IUCN first declared it "critically endangered" in 1996.

The Yangtze sturgeon — which could grow up to 8 metres in length — was highly sensitive to increased noise on the river. Its meat was considered a delicacy in China and it was also fished as a source of caviar.

"Everyone, support the ban on fishing in the Yangtze River, and protect the habitats that are still in the Yangtze River," another Weibo user posted.

Despite maintaining a breeding program for the sturgeons, the country has not been successful at maintaining them in the wild. China implemented a fishing ban in some parts of the Yangtze River in 2021.

In 2005, more than 10,000 sturgeon fry, 200 junior sturgeon and two adult fish were released into the Yangtze River as part of a continued effort to repopulate the species' battered numbers. They were only the latest in the five million of the fish, bred in captivity, to have been released into the wild over the past two decades.

ABC/Reuters