The naked carp, a precious species that helps maintain the ecological security of China's largest inland saltwater lake, Qinghai Lake, in northwest China's Qinghai province, is now under better protection after experiencing a sharp drop in its population due to various reasons including mass killing decades ago.

Thanks to the efforts made by a group of young people who combat illegal fishing, build migration channels for the fish, and help the species reproduce, the volume of the fish exceeded 100,000 tonnes last year, more than 40 times the number at the beginning of the century.

Picture No.1 shows workers from a naked carp rescue and protection center on the bank of Qinghai Lake in northwest China's Qinghai province making holes in a freezing pond outside the center to feed fingerlings. 

Picture No.2 shows the magnificent winter scenery of Qinghai Lake in northwest China's Qinghai province. 

Picture No.3 shows Li Chaowei, a member of a patrol team that protects naked carp in Qinghai Lake in northwest China's Qinghai province, observing the condition of the freezing lake. (People's Daily/Liu Yurui)

Li Chaowei is one of the young members of a patrol team that protects this precious species along the shore of Qinghai Lake. For the 41-year-old man and the other three team members, patrolling a 186-km section of the shore to combat illegal fishing is just part of a daily routine.

According to Li, there are eight points along the section from which he and his team mates can get onto the frozen lake, and the patrol team inspects at least four of these points every day.

Poachers have to go along the same routes as the patrol team does, as the fences along the shore present a major barrier for anyone carrying heavy equipment, Li said, adding that poachers usually dig holes in the frozen lake to catch naked carp with nets in winter. He said that the patrol team once found 180 holes dug by poachers, the largest number they had ever discovered.

"The first thing to do once we get on the ice is to look for footprints and tyre marks," Li told People's Daily, explaining that since it often snows at night in the area, these marks are a good indication that poaching has been taking place, as poachers always fish at night.

Li recalled that they once waited five hours on a freezing winter night just to catch poachers red-handed. "I could barely feel my feet," he said with a smile.

"It's not easy in the summer, either," he said, adding that they always stay up all night during the season to catch poachers, as large numbers of naked carp often gather at river mouths in summer for their breeding migration.

In order to boost naked carp reproduction in Qinghai Lake, Gangcha county of Qinghai province addressed the lack of channels needed for the fish to carry out their migration.

Anadromous species like the naked carp spend most of their time in the lake, which has a high level of salt, but travel upstream to spawn during the breeding season, according to Dong Qu, a technician from the bureau of environmental protection, forestry and water conservancy of Gangcha county.

The travelling facilitates the gonadal development of the adult fish, and the fresh water upstream is more suitable for the fish eggs to thrive, Dong explained.

Unfortunately, the migration routes to the major upstream rivers that flow into Qinghai Lake, such as the Buha, Shaliu and Quanji rivers, were blocked by barrages built for irrigation purposes since the 1960s, which was a major reason for the decrease in the naked carp population.

To ensure that the fish can travel easily, technicians from the bureau worked tirelessly and conducted countless trials to find the right kind of fish passages, particularly in terms of their slope and width. Finally, they came up with the idea of the fish ladder. Today, 95 percent of the naked carp in Qinghai Lake can pass through the fish ladders smoothly, Dong said.

"The stepped fish passages effectively protect the fecundity of the species," Dong observed, adding that this is a crucial method of dealing with their declining numbers.

Artificial rearing is another important part of efforts to replenish naked carp resources in Qinghai Lake. The task is undertaken by a naked carp rescue and protection center on the bank of the lake.

Every year in mid-April, when naked carp gather at river mouths to begin their breeding migration, technicians from the center start to pick suitable parent fish from icy rivers for artificial cultivation. After the fish fry are hatched, they are brought to the rescue and protection center to be taken care of by professionals.

When the fingerlings turn one year old and reach 10 centimeters in length in June the following year, they are released into the rivers that flow into Qinghai Lake, according to Qi Hongfang, a technician from the center.

Statistics show that the number of fingerlings released by the center since 2002 has exceeded 100 million, representing 23 percent of the recovered naked carp resources in Qinghai Lake.