'Extinct' Yangtze sturgeon makes comeback in wild
The Yangtze sturgeon, which had been declared extinct in the wild by the International Union for Conservation of Nature and Natural Resources, has reproduced in the wild in Sichuan province, albeit with a little nudge from humans.
Researchers hailed the development as a key step in rebuilding the Yangtze sturgeon population.
In July, the IUCN released an updated report about the Red List of Threatened Species, in which it declared the Yangtze sturgeon — a rare and iconic species — to be extinct in the wild.
But last month, researchers placed 20 mature males and females into the Jiang'an section of the Yangtze River in Yibin, Sichuan. The fish lived in experimental cages of 45 cubic meters. Two days later, using underwater monitors, researchers discovered that natural spawning had taken place. And in the following days, fertilized sturgeon eggs hatched.
Nearly eight months since the species had been declared extinct in the wild, it had reproduced naturally in the wild, said Du Hao, a researcher at the Yangtze River Fisheries Research Institute of the Chinese Academy of Fishery Sciences.
The success of the experiment proves that the Yangtze sturgeon has retained its instinct for reproducing in the wild. It represents a step forward in establishing a practical foundation for the restoration of its habitat and the rebuilding of wild sturgeon populations, Du said.
The Yangtze River Sturgeon Rewilding and Reproduction Experiment was conducted by Du's institute, in conjunction with the Fisheries Institute of the Sichuan Academy of Agricultural Sciences and the Yibin rare aquatic animals institute.
Du was the project leader, and Zhou Liang, head of the Yibin institute, participated in the whole process.
"The 20 Yangtze sturgeon that were involved in the experiment came from my institute," Zhou said.
Many researchers have said that without the Zhou family, the Yangtze sturgeon might have become truly extinct, both in the wild and in captivity.
In 1993, Zhou's father Zhou Shiwu, a fan of aquatic fauna, founded the institute — the country's first private organization for the protection of rare fish. In 1998, the institute successfully bred Yangtze sturgeon, and six years later it started breeding the species on a large scale.
After Zhou Shiwu died of cancer in 2016, his son Zhou Liang took charge of the institute. Each of the 20 Yangtze sturgeons involved in the experiment was about 1.2 to 1.4 meters long.
Two days after being placed in the river, the fish began spawning. On March 26, many fry hatched from the eggs. The fry were about 5 or 6 millimeters long, like small tadpoles, with small tails and white bodies.
In recent years, many breeding sturgeons have been released into the Yangtze River to allow them to grow freely, but researchers have never been able to monitor them in the river until now.
The fish were kept in cages for the experiment so that researchers could monitor them, the younger Zhou said.
"The IUCN declared the Yangtze sturgeon extinct in the wild because no Yangtze sturgeon had been found spawning in the wild for two decades. It's possible they have spawned in the wild, but researchers cannot find evidence of it," he said.
The sturgeon population declined sharply from the 1960s to the 1980s in the face of human activity, including overfishing with advanced tools, as well as sand and rock dredging, navigation channel regulation and water pollution.
New experiments may be made in wider areas of the Yangtze River in the wake of the successful spawning experiment, Zhou said.
For example, a wider body of water in the Yangtze River will be blocked to conduct the experiment again. The ultimate goal, he said, is to release sturgeon into the Yangtze River so that they can spawn and increase their populations naturally.
