Chongqing - Staff at the Rare and Endemic Fish National Nature Reserve, a feralization and domestication base in Wanzhou District, Chongqing, threw fish food into the net cage to improve the quality and nutrition of meals for the "special guests" - Yangtze sturgeon (Acipenser dabryanus), a first-class protected animal, and other second-class protected animals.

The IUCN has declared the Acipenser dabryanus extinct in the wild, but it is now mostly being propagated artificially.

Since 2010, the Wanzhou District Fisheries Research Institute has been researching the artificial reproduction of the Yangtze sturgeon. In the past few years, as some of the Yangtze sturgeons reached sexual maturity, the institute has been developing technological breakthroughs to help release the captive Yangtze sturgeons into the open water and revitalize the species' population.

Finding a home for Yangtze sturgeons

Established in 2009, the base serves two purposes. One is to domesticate the rare Yangtze River fish in the wild and artificially propagate them when they reach sexual maturity. The other is to let the captive fry adapt to the wild environment and then propagate artificially and release them as they become mature.

"There are 50 Yangtze sturgeon parent fish and backup parent fish we transplanted and domesticated living here," said Fu Qiumin, an aquatic expert at Wanzhou District Fisheries Research Institute.

Breeding parent fish is the key to artificial reproduction for rare and endangered species in the Yangtze River. After acquiring a school of Acipenser dabryanus through introductions in 2010, the researchers placed some of the fish in the Shuanghekou Rare Fish Reproduction Plant for pond breeding, some for micro-flow breeding, and some in the Dazhou Feralization and Domestication Base.

As a result of continuous experimentation, it has been found that Yangtze sturgeons living in the feralization base in the Yangtze River enjoy the most optimal conditions due to the correct temperature and quality of the water. "In fact, the Yangtze River is an ideal habitat for them to thrive," explained a member of the staff. Upon moving to the feralization base, these Yangtze sturgeons were officially relocated.  

Helping the Yangtze sturgeons Settle Down

The Yangtze sturgeons take a long time to reach sexual maturity, and they have high requirements for water temperature, flow, quality, space, and nutrition. Therefore, settling them down is hard.

The staff tried to supplement nutrition for the Yangtze sturgeons to ensure healthy parent fish. Initially, there was no special Yangtze sturgeon parent fish feed on the market, so they purchased the best Yangtze sturgeon feed. However, they soon discovered the meal was only for adult fish and adversely affected their gonadal development. Therefore, they quickly replaced the feed with special parent fish feed. Furthermore, to meet the natural habits of Yangtze sturgeons, they bought small fish and searched for water earthworms along the riverbank. Each year, the staff flush the water by water pumps so that Yangtze sturgeons can exercise for gonadal development in March and April.

This is how Yangtze sturgeons grew up.

The researchers began artificial propagation when some of the Yangtze sturgeons reached sexual maturity. However, the eggs could not be fertilized since the female gonads were still not mature.

Despite this, the researchers remain optimistic. "We will never stop researching the artificial reproduction technology for Yangtze sturgeons and their release regardless of whether this year's experiment is successful," said Liu Benxiang of Wanzhou District Fisheries Research Institute.

Sending the Yangtze sturgeons Home

With the implementation of the Yangtze River fishing ban and the release of the Yangtze River Protection Law, wild fish numbers in Wanzhou District have increased significantly.

A monitor cruise conducted by the Wanzhou District Agriculture Administration and Law Enforcement Detachment on March 12 this year caught a Yangtze sturgeon.

It is the first time the Yangtze sturgeon has been found in Wanzhou District since the "ten-year fishing ban" was implemented. Fu Qiuming said the Yangtze sturgeon was about 50 centimeters long and weighed 0.498 kilograms. The fish is about two years old and has been living in the wild for a long time. 

"We hope to overcome the technical challenges of artificial propagation as soon as possible to add a school of Yangtze sturgeons to the Yangtze River." Liu Benxiang said.

(Tan Sirui, as an intern, also contributed to the report.)