Overlooking the Yangzong Sea.
Photo by Jiang Tao (People's Vision)
Yangzonghai held a breeding and release activity.
Photo by Li Juan (People's Vision)
Yangzong Sea with clear water.
Photo by Ma Jianyun (People's Vision)
Core Reading
Yangzonghai in Kunming, Yunnan Province, is beautiful by the water, but also trapped by the water. More than ten years ago, Yangzonghai was banned from drinking, swimming and fishing due to serious pollution. In recent years, with continuous management and protection, Yangzong has restored water quality and improved ecology, and has embarked on a new path of ecological priority and green development.
Yangzonghai in May is as vast as a mirror. On the surface of the lake, the fish leap and sparkle, and the gulls and herons soar and gather; On the shore, visitors are weaving, and the breeze is green.
Yangzonghai is one of the nine major plateau lakes in Yunnan, only 36 kilometers from the main city of Kunming. It is hard to imagine that the beautiful Yangzong Sea was banned from drinking, swimming and fishing more than ten years ago because of serious water pollution. With the continuous management and intensification of protection, the average water quality of the whole lake has gradually recovered from the inferior class V in 2008 to class II., the water environment has been stable and improving, and the fish resources have gradually recovered.
How to continuously improve the water ecology? How can fish community diversity be restored? The reporter recently interviewed Yangzonghai's front-line protection personnel, scientific research workers and surrounding fishermen, and explored the "policy of many lakes" with the "governance of one lake".
Conduct resource surveys
The situation of endemic fish stocks is not optimistic
The morning light dewed, with the roar of the fishing boat engine from far and near, Shi Guoliang, a villager of Haiyan Village, Yangzong Town, drove the fishing boat slowly to the shore, Xiong Qinghai and his colleagues who were waiting at the wharf early also jumped on the bow of the boat, and after confirming the time, place and weather conditions of the net, all the fish caught were brought to the management office for classification and identification.
"Whitebait, body length 48.7 mm ......" As the director of the Fishery Technology Development and Promotion Department of Kunming Institute of Fishery Sciences, Xiong Qinghai and his colleagues reported the number and recorded it alone. It seems boring and repetitive, but it is the most basic work to understand the fish community structure in Yangzonghai.
According to the literature, there were as many as 20 species of indigenous fish in Yangzonghai, including five endemic fish in Yangzong, such as Yangzong goldenrod, Yangzong white fish, and short-tailed squid, and Yunnan endemic fish such as Fuxian catfish and Yunnan barbed catfish. Shi Guoliang said that the last time he saw Yangzong Baiyu was more than ten years ago. What other fish are in the lake now? First of all, it is necessary to find out the bottom number of fish communities.
Xiong Qinghai introduced that there may be great differences in the types and quantities of fish that can be caught in deep water areas, shallow water areas, south and north shores, upper and lower layers of lakes, and even day or night, winter or summer. "To carry out fish population surveys, it is necessary to choose the location of sampling and survey, and cover as many different areas and time periods as possible." Xiong Qinghai said that traditional fishing methods are more occasional, and ultrasonic detection can reflect the size, quantity, orientation, and water layer of the fish in more detail, and the data obtained by traditional fishing combined with assisted ultrasonic detection is more accurate.
From 2022 to 2023, a total of 25 species of fish were collected from the Yangzonghai Fish Resources Survey, including 6 indigenous species and 19 alien species. However, in the past two years of fish resource survey, none of the five species of endemic fish in Yangzonghai have been caught.
"The population situation of Yangzonghai's endemic fish is not optimistic." Xiong Qinghai said that the survey showed that the number of indigenous fish species in Yangzong Sea has decreased sharply, and the population of alien fish accounts for more than 80 percent, forming a new community structure in which the majority of introduced species and indigenous species are in obvious decline.
"The introduction of fish species in plateau lakes must be cautious." Experts say that the rapid disappearance of indigenous fish is not unrelated to the introduction and invasion of alien species.
According to reports, in the eighties and nineties of the last century, in order to increase production, Yangzonghai introduced new silverfish from Taihu Lake, but it did not expect to bring disaster to the indigenous fish. The whitebait are abundant and reproduce quickly, and the eggs of some indigenous fish have also become a delicacy for whitebait, while the young indigenous fish and whitebait that have been hatched with great difficulty do not have an advantage in grabbing food, and their growth is affected. In the past, whitebait was fished by trawling, and many indigenous fish were also fished ashore, which is also one of the reasons for the sharp decline of indigenous fish populations.
Restoration of population structure
Equal emphasis is placed on restocking and scientific fishing
How can the structure of fish populations be restored as indigenous fish populations decline? After getting the results of the Yangzonghai fish resources survey, Yang Jianhong, deputy director of the Kunming Institute of Fishery Sciences, frowned. "The last time I saw Yangzong golden-threaded catfish was in 1992." Yang Jianhong said that the disappearance of five endemic fish species means the decline of the entire community, and if measures are not taken in time, rare and endemic species may disappear in the future.
"To restore indigenous fish populations and improve the complexity and stability of fish communities in Yangzonghai, manual interventions such as restocking are indispensable." Xiong Qinghai said.
Five species of indigenous fish endemic to Yangzonghai have long since disappeared. In desperation, the research team selected the Yunnan glossy lip fish, which was available in the market and had previously been recorded in the Yangzong Sea, as the indigenous fish species that were restocked and released.
Yang Zesong, Secretary of the Party Working Committee and Director of the Management Committee of Yangzonghai Scenic Area, said that in recent years, the local government has carried out 14 breeding and releases, with a total of 11.695 million fish fry, and since 2022, 275,000 indigenous fish have been added and released to Yangzonghai. Nowadays, the breeding and release of Yangzonghai has formed a structure with a reasonable mix of silver carp, bighead carp filter-feeding fish and indigenous fish.
It is gratifying to note that the two indigenous fish have a high rate of recatch and are well adapted. "The indigenous fry that have been restocked have increased their weight rapidly and have a high level of intestinal fullness. This shows that the water ecological environment of Yangzonghai can meet the growth needs of these two indigenous fishes. Yang Jianhong said.
While restoring indigenous fish populations, it is imperative to regulate the populations of exotic species such as whitebait. According to reports, to reduce the number of whitebait, it is necessary to carry out artificial fishing. In order to avoid catching other fish by mistake when catching whitebait, the special whitebait fishing has now been replaced by a special gillnet for whitebait, which is caught by light at night. At the same time, the amount of resources is scientifically calculated, and the fishing time is determined according to the law of growth and reproduction.
In the past few years, Xiong Qinghai and fishermen have continued to take samples, record the specifications of whitebait at different times, and finally finalized the special whitebait fishing in early November, and determined a 45-day special whitebait fishing period, which can not only effectively control the number of whitebait, but also ensure the fishermen's income.
During the fishing period, at night, the surface of Yangzonghai Lake is dotted with stars, and fish lamps reflect the water surface. Whitebait are attracted by the light and caught in a gillnet and cannot break free, while indigenous fish are too large to enter the net and are not caught by mistake. After several years of special fishing, the amount of whitebait resources has now dropped from 90% at the peak to no more than 1/10.
Drive the masses to benefit
Let fishermen share the fruits of ecological governance
Monitoring data show that in Yangzonghai Lake, the resources of medium and large fish such as silver carp and bighead carp that play a role in water purification account for more than 80%. However, the ability of silver carp and bighead carp over 4 years old to filter algae and the nitrogen and phosphorus conversion efficiency decreased significantly.
"Only by properly carrying out ecological regulation and control fishing, catching large and letting go of small fish, can the purification efficiency of silver carp and bighead carp be maximized." Xiong Qinghai introduced that in 2019 and 2023, Yangzonghai carried out ecological regulation and control fishing of large silver carp and bighead carp twice, and regulated the community structure of silver carp and bighead carp in the lake by "catching big and leaving small", while increasing fishermen's income.
"I'm a new fisherman and an old fisherman." Shi Guoliang said that he has not fished for more than a decade since Yangzonghai was banned from fishing in 2008. In 2019, the village party secretary of Haiyan Village went door-to-door to inform that he could re-enter Yangzonghai to fish, and Shi Guoliang immediately purchased more than 30,000 yuan of fishing tools and electric boats.
"When is the right time to fish?" "When is the price a little higher?" In June 2023, after inviting fishermen to a discussion, the Yangzonghai Management Office set the start time of special fishing for silver carp and bighead carp around the National Day and Mid-Autumn Festival. Everyone agreed: "There are many tourists, and the fish is easy to sell!" ”
During the special fishing period, the fishermen of Yangzonghai tasted the joy of a bumper harvest: they went out at three or four o'clock in the afternoon, went ashore in the early morning, and went home in the morning, and there was a harvest every day. "On the first day I opened the lake, I caught more than 1 ton of fish." Shi Guoliang said that in 15 days, his income was close to 40,000 yuan, and with the special whitebait fishing in November, the annual income from fishing in Yangzonghai exceeded 60,000 yuan.
King of Fish Auction, Fish Feast Tasting, Happy Fishing, Fishing Experience...... During the fishing period, the surrounding tourists come to visit, the front foot just bought a big fish to try it, and the back foot joined the ranks of fishing and fishing, and had a lot of fun.
"Only by allowing fishermen to share the fruits of ecological governance can the restoration and conservation of indigenous fish be scaled up in a long-term and sustainable manner." Yang Jianhong said.
In the ecological tank in the exhibition hall on the first floor of the Yangzonghai Management Office, several indigenous fish swim in it. The staff said: "I hope that in the future, the indigenous fish population will recover, and the fishermen will also have a higher income. ”
Source: People's Daily
Editor: Zhao Ziwei
Editor: Lin Shuaichao
Final review: Zhao Wen