Why were more than 200,000 Chinese sturgeons released into the river?

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More than 200,000 artificially bred Chinese sturgeon were released into the Yangtze River on Saturday as part of a conservation project for the critically endangered species.

The sturgeons were bred by the China Sturgeon Research Institute of the China Three Gorges Corporation (CTG). The release – off the city of Yichang in central China’s Hubei Province – was the second on such a large scale since the Yangtze River Protection Law went into effect on March 1. ‘last year.

The fish is considered a national treasure, like the giant panda, but its population in the wild is on the brink of extinction. According to Jiang Wei of the China Sturgeon Research Institute, releasing artificially bred fish into the river at this scale could have a positive impact on the recovery of the species.

From 1984, when the release was first carried out, until today, nearly 5.3 million sturgeons have been released into the Yangtze by the China Sturgeon Research Institute. But decades of hard work have so far paid little dividend.

A Chinese sturgeon is released into the river on April 9, 2022. /CTG

A Chinese sturgeon is released into the river on April 9, 2022. /CTG

Conservation takes time and effort

“So far, we haven’t seen any obvious effect because the number released needs to be expanded and increased, and the whole natural environment (river and sea) needs to be improved as well,” he said. said Jiang, who studied China. sturgeon for years.

Questions have been raised as to whether artificial breeding can save the species. More than 200,000 Chinese sturgeon seems like a large amount, but considering the natural survival rate, only a small number of sturgeon can successfully reach the sea and migrate to breed.

Chinese sturgeons can live up to 40 years. The fish head to their spawning grounds in the Yangtze River in autumn to lay their eggs. After five to six days, the fertilized eggs grow into fish, then they swim out to sea to spend most of their lives there. It is not until sturgeons reach sexual maturity, around the age of 14, that they begin to migrate to rivers to spawn.

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The research path

The released Chinese sturgeon face an arduous journey between river and sea and back. At first, researchers sought to trace them by rudimentary methods. They tagged the fish with a simple card, Jiang said, and had to wait for the fishermen to call the phone number left on the card when the fish was caught.

But more recently modern technologies have been deployed including sonar tagging, DNA and PIT (passive integrated transponder) tagging as well as T (telephone and code numbers) tagging. With these new tracking methods, researchers can collect a lot more data.

Artificially bred sturgeons migrate to the ocean in much the same way as their naturally bred counterparts. Once released, most of them head directly downstream and arrive in the East China Sea. The bigger the sturgeon, the more likely it is to survive the trip. Data from 2019 showed that 73.3% of sturgeons managed to reach the sea. Experts can only wait and hope that the fish can grow up and return to the river to lay their eggs.

A Chinese sturgeon is released into the Yangtze River, April 2021. /CTG

A Chinese sturgeon is released into the Yangtze River, April 2021. /CTG

No wild eggs, but hope remains

Last November, a group of experts from institutes such as Chinese Academy of Fisheries Science, Chinese Academy of Sciences, Ministry of Water Resources and CTG conducted research on the Yangtze River in the hope of discovering wild Chinese sturgeon eggs.

But they were disappointed. For five years, no sign of natural reproduction of the species has been recorded. Another difficulty, the marine area is black, hampering the study of the customs of their subjects, which remain mysterious.

Jiang has started a long-term project to place satellite beacons to study the marine habitat history of Chinese sturgeons. By tracking tagged sturgeons and collecting data, he hopes to learn more about fish life in the vast ocean and see if there are any differences between life there and life in fresh water.

The oldest traceable Chinese sturgeon released is now 9 years old, according to Jiang, and researchers must wait another 5 years until it can reach sexual maturity and migrate to the river. By then, they hope to learn more about the behavior of the species.

A Chinese sturgeon wearing a tracker is released into the water, April 2021. /CTG

A Chinese sturgeon wearing a tracker is released into the water, April 2021. /CTG

Other aquatic creatures also decreased in number over the period. “Chinese sturgeons were once widely distributed in many areas, such as the Yellow River and the Pearl River, but the species can only be found in the Yangtze River now. Not only Chinese sturgeons, but many other species also show a decline over the same period,” Jiang said.

In the 1970s, Chinese sturgeons lost their natural reproduction in the Pearl River. And in the late 1990s, no wild sturgeon were seen in the Pearl River, Jiang told CGTN.

A year after the implementation of the Yangtze River Protection Law, other endangered species such as Yangtze finless porpoises have been spotted more often. The law is seen as offering a good chance to rebuild the river’s fish stocks, including Chinese sturgeon.

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