On the restoration of the Yangtze River ecosystem from the Yangtze finless porpoise
In Wuhan, Hubei Province, finless porpoises are artificially raised in the Institute of Hydrobiology, Chinese Academy of Sciences. Our reporter Zhou Mengshuang photo/bright picture
[Rivers flow — — Report from the Yangtze River Economic Belt]
"My family has been fishermen for generations. I was born on a fishing boat in Huanggang, Hubei Province. I have been living on the Yangtze River since I can remember." Shu Yin ‘an, 51, has been fishing for 40 years and witnessed the Yangtze finless porpoises changing from small to large.
In June 2017, Shu Yinan put away his fishing net and signed up as a member of the patrol team of the finless porpoise in Hukou, Poyang Lake. "When I was a child, finless porpoises could be seen everywhere on the Yangtze River. Now it is not only difficult to find finless porpoises, but even the fish species such as shad and river bream are almost extinct."
In 1990, 3,600; In 2006, 1,800; In 2012, 1,045 heads; In 2018, 1012 heads … … In the past 30 years, as Shu Yinan felt, the population of Yangtze finless porpoise is declining. The bigger problem of fermentation behind this is the heavy pressure that the Yangtze River ecosystem is facing.
"The extreme endangerment of the Yangtze finless porpoise population is the result of a variety of human activities, such as the great decline of fish population caused by the obstruction of rivers and lakes and the overfishing of cool fish, the lack of food for finless porpoises, the rapid development of shipping industry interfering with the sonar communication of finless porpoises, water pollution reducing their fertility, fishing gear and ships accidentally injuring finless porpoises, etc." Xu Xudong, a researcher at the Institute of Hydrobiology, Chinese Academy of Sciences, said, "The Yangtze finless porpoise is a mammal at the top of the food chain of the Yangtze River ecosystem and is very sensitive to environmental changes. Their number is a mirror reflecting the health of the Yangtze River ecosystem."
In the view of many aquatic experts, "no food" is the primary reason that restricts the population of Yangtze finless porpoise.
The Yangtze River basin is a natural spawning ground for many freshwater fishes, and fishery resources were once extremely rich. However, today, the fishery resources in the Yangtze River have declined in an all-round way: the annual output of shad has basically disappeared from 1570 tons in 1974 to now, and the annual output of Coilia ectenes has been 4,000 tons in the 20th century. In recent years, it has been impossible to form a fish season. Compared with the 1950s, the number of seedlings of the "four big fish" has dropped by more than 90%, and the number of eggs laid has dropped from the highest 30 billion to the lowest 100 million … … The finless porpoise, which feeds on fish, has also been hit by the "food crisis".
"Many fish in the Yangtze River are Jianghu migrants, and their life history cannot be completed without migration." Xu Xu told reporters that the four well-known fish, namely, grass, silver carp and bighead carp, will fatten in the lake with rich food and migrate from the lake to the Yangtze River when they are sexually mature. When the water temperature reaches above 18 degrees and the river surges, they can be stimulated to estrus and reproduce, and then the fry hatched in the Yangtze River will swim back to the lake.
However, since the 1950s, most of the Tongjiang lakes in the middle and lower reaches of the Yangtze River have been artificially blocked, and many kinds of fish have declined or even died with the disappearance of migration routes, resulting in the loss of important food sources for the Yangtze finless porpoise. "Due to the decline of fishery resources, many fishermen use a large number of illegal fishing methods such as electric fishing, purse seine, ecstasy and rolling hook to make a living, which further causes the serious decline of fishery resources and also causes many finless porpoises to be accidentally caught and killed." Hao Yujiang, an associate researcher at the Institute of Hydrobiology, Chinese Academy of Sciences, introduced.
According to the latest data, there are about 457 Yangtze finless porpoises living in Poyang Lake, accounting for about half of the existing population of Yangtze finless porpoises, and the waters from Ezhou to Anqing in the main stream of the Yangtze River, that is, the waters upstream and downstream of the Poyang Lake estuary, are also the waters with the highest distribution density of Yangtze finless porpoises in the main stream.
"Poyang Lake is one of the three remaining Tongjiang lakes in the middle and lower reaches of the Yangtze River. Natural hydrological changes and smooth migration channels have given birth to relatively rich fishery resources, which has also become an excellent habitat for the Yangtze finless porpoise to survive." Hao Yujiang said. In his view, in order to restore the fishery resources of the Yangtze River, firstly, the problem of fishermen should be fundamentally solved at the national level, and fishermen should be helped to change jobs, so that the fish resources of the Yangtze River can be recuperated for two or three generations to promote the rapid recovery of fishery resources; Second, actively promote the natural ecological protection of the Yangtze River, restore the natural coastline and sandbar vegetation of the Yangtze River, restore the connection between rivers and lakes where conditions permit, create a natural habitat suitable for aquatic organisms, and restore the natural life characteristics of the Yangtze River.
"Fishery resources are typical open public resources, which can easily lead to overuse ‘ Tragedy of the commons ’ 。” Ma Yi, director of the Fishery Supervision and Administration Office of the Yangtze River Basin of the Ministry of Agriculture and Rural Affairs, said that the annual catch of the Yangtze River has been less than 100,000 tons, accounting for only 0.15% of the national freshwater catch, which has basically lost the value of fishery production. The current system of closed fishing season in the Yangtze River has played an extremely important role, but it has not fundamentally changed the general trend of the sharp decline of fishery resources in the Yangtze River. "In order to protect the Yangtze finless porpoise and protect the biodiversity of the Yangtze River, it is imperative to accelerate the comprehensive ban on fishing in key waters of the Yangtze River Basin." Ma Yi said.
The Yangtze finless porpoise, whose number is less than that of giant pandas, has not been adjusted since it was designated as a second-class protected animal in 1989, and the lagging legal status has become another important reason to limit the protection of the Yangtze finless porpoise to some extent. Ma Yi told reporters that in 2014, the former Ministry of Agriculture asked all localities to implement the strictest protection and management measures for the Yangtze finless porpoise according to the national first-class key protected wild animal standards, but wanted to update the List of National Key Protected Wild Animals and formally identify the Yangtze finless porpoise as a national first-class key protected wild animal, which involves the coordination and unification of various departments in charge of wildlife protection, and the Ministry of Agriculture and Rural Affairs is currently actively promoting it.
"Protecting the Yangtze finless porpoise is to restore the fishery resources of the Yangtze River and protect the ecosystem of the Yangtze River. ‘ 1012 heads ’ The latest investigation results of the Yangtze finless porpoise show that the deterioration trend of the Yangtze River ecosystem has been curbed. " Hao Yujiang thinks that the future of the Yangtze finless porpoise and the future of the Yangtze River is "very promising".
(Reporter Zhou Mengshuang)