BEIJING -- Chinese scientists have successfully assembled the chromosomal-level genome of the critically endangered Ochetobius elongatus, a rare fish species from the Yangtze River.

This marks the first time that a high-quality genome at the chromosomal level and annotation information has been obtained for the species, and it represents a significant advancement to restore the fish population, China Science Daily reported on Thursday.

The achievement was made by a research team led by Professor Lu Jianguo from the School of Marine Sciences at Sun Yat-sen University and researchers of the agricultural science institute of Jiujiang city, East China's Jiangxi province. The research findings were published in Scientific Data, a scientific journal under Nature, on Dec 19.

The Ochetobius elongatus, once an important freshwater economic fish in China and widely distributed in the Yangtze River Basin, has experienced a sharp decline in population over the past three decades due to environmental degradation and human activities, said Liang Xuanguang, co-first author of the research article.

The fish has a small and slender body, with a maximum length of 55 centimeters and a weight of 500 to 1,000 grams. As a migratory fish, it reproduces from April to June each year. After hatching, the young fish leave the rivers and migrate to lakes for feeding and overwintering. It takes three to five years for them to reach sexual maturity.

The species was listed as "critically endangered" in China's Red List of Biodiversity in 2023, Liang said.

Following the implementation of the 10-year fishing ban in the Yangtze River at the beginning of 2020, an improvement has been seen in the fishery resources of the river.

In December 2020, seven individuals of Ochetobius elongatus were discovered in the Gong'an section of the Yangtze River. This marked the third time the species had been observed since June 2017 and November 2020, and it was the first instance of multiple individuals being recorded in recent years, said Liang.

The reappearance of the rare fish provides an opportunity for conservation efforts.

Despite the application of conservation genetics and genomics in the protection of several endangered species within the Yangtze River Basin, such as the Yangtze finless porpoise, Gobiocypris rarus (a freshwater species of cyprinid fish endemic to China), and Leptobotia elongata (a species of botiid fish)?— all of which have had their genomes sequenced and assembled, the critically endangered Ochetobius elongatus had yet to have its genome assembled until this time.

The researchers assembled the chromosomal-level genome of the Ochetobius elongatus based on various sequencing technologies. According to Liang, a total of 28,674 protein-coding genes were predicted, with 28,637 genes (99.87 percent) annotated, indicating the high quality of the genome assembly.

"This is the first release of the genome information of Ochetobius elongatus. It is crucial for understanding genetic diversity, identifying unique adaptations, and formulating effective conservation strategies for the species," said Lu Jianguo, the corresponding author of the research article.

In the future, Lu's team plans to focus on research on artificial breeding and aquaculture techniques for the rare fish, aiming to achieve sustainable artificial breeding of the species.