Endangered fish returns to Yunnan's Dianchi Lake thanks to environmental efforts

In late spring, flocks of golden-line barbels (Sinocyclocheilus grahami) are swirling in the clear water of Heilongtan Park located in the upstream of Dianchi Lake, Kunming, capital of southwest China's Yunnan province, presenting a gorgeous image together with the Ottelia acuminata swaying in the crystal clear water and the flowers floating on the surface.

Red-billed gulls from Siberia come to Dianchi Lake, Kunming, southwest China's Yunnan province to winter, attracting a large number of visitors, Jan. 19, 2019. Photo by Zhu Wenbiao/People's Daily Online

The golden-line barbels are one of the four famed fishes of Yunnan province. The species' history traces back to over 3 million years ago when Dianchi Lake was just formed, so it is dubbed as an "antique" in the lake.

However, golden-line barbels had once disappeared in Dianchi Lake in 1980s, due to the increasing pollution and overfishing. Besides, the invasive alien species also threatened the environment of golden-line barbels' living and spawning.

The fish was not the only species vanishing. In 1960s, Dianchi Lake had 26 homegrown fish species, but now there are only four. Currently, 15 homegrown fish species in the region are endangered or vulnerable.

Dianchi Lake had long been a production-type lake, as to "fill the stomachs." Raising the output of aquatic products remained the most urgent task then.

Homegrown fishes dominated the lake before 1957. After the lake was stocked with bighead carps and grass carps in late 1960s, fishing production reached 3,080 tons in 1969. The figure went up to 8,363 in 1975, and the oriental river prawn and the Serbian prawn accounted for the majority. In 1980s, whitebaits, an alien species, became the main production out of the lake. The catch of the fish alone once hit 3,500 tons.

Local authorities started stocking the lake with homegrown fish - artificially bred golden-line barbels since 2010 for water treatment, according to Wang Yong, an official with local fishery administration, who noted the fishes introduced to diversify the food sources of the citizens had brought huge pressure on the survival of golden-line barbels.

The vulnerability of golden-line barbels' breeding in the lake indicated their high dependence on water quality, said Yang Junxing, a researcher with the Kunming Institute of Zoology, the Chinese Academy of Sciences (CAS). Yang added that the mountains, waters, forests, farmlands, lakes and plants are interdependent and share the same destiny, and the disappearance of the golden-line barbels in Dianchi Lake was indeed an early warning sign for human beings that the lake was "sick."

Red-billed gulls forage on Dianchi Lake, March 8, 2017. Photo by Li Faxing/People's Daily Online

Dianchi Lake, having suffered from ecological damages, was once one of the most-polluted lakes in China. Thanks to years of treatment, the water quality of the lake improved to Class V in 2016, a level that is mainly applicable to the water bodies for agricultural use and landscape requirement. Two years later, the quality met the standard of Class IV, the best performance in 30 years. The rating maintained the same last year.

"The protection of Dianchi Lake has entered a new window period, gradually turning from engineering treatment to focusing on homegrown species," said Li Weiwei, deputy curator of Kunming Natural History Museum of Zoology. Li noted that the enhanced biodiversity in Dianchi Lake will help shape a balanced ecological system.

The treatment of Dianchi Lake is a big concern of Yunnan and a key project of the province to build ecological civilization. Moving from treating only "point source pollution" to treating basin systems, the province is now placing more attention on ecological restoration.

The wetland recovered near Dianchi Lake has become a natural bird habitat that sees an increasing number of bird species, including the endangered glossy ibis, as well as ruddy turnstone and greater sand plover.

Pan Min, senior engineer with a Kunming-based research institute on plateau lakes, gave a high evaluation on the city's efforts to contain pollution and restore lake, forest and wetland by removing ponds, cropland, human activities and housing. "It is a universally recognized experience to solve exogenous pollution through engineering measures and then resort to ecological treatment of the water," Pan noted.

The golden-line barbels, turning from an endangered species to one that can breed thousands with human intervention, and from its disappearance in the lake to its contribution to local ecology, are offering new ideas for the treatment and restoration of lake ecology with its shared fate with Dianchi Lake.