"The Yangtze River white sturgeon found in 2003 is a female, and it can mate and lay eggs in April and May, and we wanted to keep it, but unfortunately there were no artificial breeding conditions at that time." Zhang Zhiying, director of the Fisheries Administration Department of the Sichuan Provincial Fisheries Bureau, recalled that it was the last time he saw the Yangtze River white sturgeon, and it was also the last Yangtze River white sturgeon in the world to be rescued.
Zhang Zhiying, who joined the work in 1985, began to engage in fishery administration and management in 1986, and has dealt with major rivers and fish for more than 30 years. Regarding the news of the recent extinction of the Yangtze River white sturgeon, Zhang Zhiying said that he personally prefers the statement of functional extinction, that is, the surviving Yangtze River white sturgeon has been unable to achieve the continuation of the population.
"Large fish such as Yangtze River white sturgeon, Chinese sturgeon, and Yangtze River sturgeon are like important health indicators such as red blood cells, white blood cells, and platelets in human blood for large rivers." Zhang Zhiying sighed slightly, saying that in addition to these three large fish, there are hundreds of endemic fish in the upper reaches of the Yangtze River, and at least more than ten species he has not heard of appearing in the wild environment for a long time.
↑ Photographs taken by Zhang Zhiying on the spot when he rescued the Yangtze River white sturgeon in Yibin in 2003
In 2003, he rescued the Yangtze River white sturgeon
It was intended to be kept in captivity, but the conditions were not enough to miss
"Since 2003, there have been two Yangtze River white sturgeons in the entire Yangtze River." Zhang Zhiying recalled that one of them was in Nanjing, Jiangsu Province, and another in Yibin, Sichuan. "That afternoon we received the news and rushed over, when the Yangtze River white sturgeon had a stress reaction, it was already a bit of a belly, almost died", fortunately after rescue, the next day basically recovered.
Zhang Zhiying said, "In 2003, I wanted to leave 'her' behind, the Yangtze River white sturgeon is female, you can mate and lay eggs in April and May, but unfortunately there are no artificial breeding conditions at that time", raising large fish like the Yangtze River white sturgeon, two or three meters, or even three or four meters long, the pool currently used is at least more than 1,000 square meters.
"At that time, if there was a condition that another male fish could be caught, it could mate and breed, and the Yangtze River white sturgeon could lay more than 100,000 eggs at a time." Zhang Zhiying said that although it is difficult to go from fish eggs to fry to adult fish, there is at least hope. What is heart-wrenching is that later, when the conditions are ripe, it is difficult to see the Yangtze River white sturgeon anymore.
Zhang Zhiying showed the photos taken at the scene of the rescue of the Yangtze River white sturgeon, and what impressed him most was its length of more than three meters, and the three people standing shoulder to shoulder next to the fish were less than one-third of the fish's body.
For the specific number of Yangtze River white sturgeon, it is impossible to complete the population continuation, and Zhang Zhiying cannot give a number. Surveys of fish cannot be as intuitive as animals on land. In addition to specialized biological surveys, they know what's going on in the water more often than not by "catching" them. "Catch" is colloquially an aquatic animal caught by fishermen from the water. At present, the longest Yangtze River sturgeon specimen in Sichuan is more than four meters long, made from a dead Yangtze River white sturgeon in the 1990s, while most of the others are about two meters long.
The spawning grounds of the Yangtze River white sturgeon are basically in Sichuan
There are "three stones" as proof
Zhang Zhiying said that in the 1980s, Chinese sturgeon could still be seen in the Yangtze River; from the 1980s to the mid-90s, three or four Yangtze River white sturgeon could be seen in a year, and there were one or two yangtze river sturgeon; the Yangtze River sturgeon could still be seen every year until the end of the 90s. And this is related to their different life habits and environmental changes. "I dare not say that it originated in Sichuan, but several major spawning grounds are basically in Sichuan."
"When it comes to spawning grounds in Sichuan, I have to mention the 'three stones.'" Zhang Zhiying pulled out a copy of the "Photo Collection of Rare and Endemic Fish National Nature Reserve in the Upper Reaches of the Yangtze River" from the bookcase, and in a photo called "Three Stone White Sturgeon Chinese Sturgeon Spawning Ground", three boulders stood by the river. The spawning of the Yangtze River white sturgeon, Chinese sturgeon and Yangtze River sturgeon must have a turbulent water flow as an external stimulus, and the conditions such as the "three stones" itself and the rocky beach in the area just create a turbulent water environment in the area.
↑ Three-stone white sturgeon spawning grounds
On the functional zoning and planning map of the protected area at the end of the atlas, it can be seen that the three stone spawning grounds are located downstream of the Xiangjiaba Hydropower Station, down the river, and there are several major spawning grounds such as Nanxi. Further down, the water potential is relatively flat, suitable for fry growth. Unlike the Yangtze River sturgeon and the Yangtze River sturgeon, the Chinese sturgeon swim back to the sea to live after mating and breeding in the Yangtze River, while the Yangtze River white sturgeon and the Yangtze River sturgeon basically settle in the Yangtze River. "After the completion of the Gezhou Dam, the route of the Chinese sturgeon migration was interrupted, and the Chinese sturgeon was seen less and less in the Yangtze River." Zhang Zhiying said that after the completion of the Xiangjia Dam in Yibin, the traces of the Yangtze River white sturgeon and the Yangtze River sturgeon have become more and more difficult to find.
↑ Functional area zoning and planning map of protected areas
Dams blocking and compressing living space are one reason, and the loss of food is also a serious threat to the survival of these large fish. "When the water is clear, there are no fish, and some fishermen have said that the water of the Yangtze River is too clear." Zhang Zhiying said that for the entire aquatic ecosystem, water is not a good thing, and truly healthy river water needs a certain amount of sand content. Year after year, the same net goes down, in the past fishermen can hit more than 100 pounds of fish, many of which are close to the length of adults' small arms; now when they are less, they are even only a few pounds. There is less food, the spawning place can not go, coupled with the change of hydrological environment and other reasons, the comprehensive factors have caused a rare situation in the Yangtze River.
The nine-tailed wild Yangtze River sturgeon, which is more precious than the giant panda
The offspring are about to return to the wild
Missed the Yangtze River white sturgeon 17 years ago, and this time, Zhang Zhiying and his colleagues will no longer miss the nine-tailed wild Yangtze River sturgeon. They are preparing to release captive-reared sexually mature Daschshund into the Yangtze River.
Zhang Zhiying said that the yangtze River sturgeon is really called Dashi sturgeon, and the nine Dashi sturgeons, which have matured when they are caught from the wild, have successfully achieved large-scale mating and breeding under the condition of artificial rearing. A single female Daschshund can lay about 100,000 eggs at a time, of which 70% can hatch into fry. "In the past, we stocked small fish of 30 or 40 centimeters, and in recent years we have also released 500 sexually mature Dashi sturgeon about 1 meter, all of which are their offspring", and it takes 6 to 8 years for The Dasten sturgeon to reach sexual maturity.
↑ Dashi sturgeon is also called Yangtze River sturgeon
"It's not easy to raise fish!" Zhang Zhiying recalled that they had also experienced artificial injections and other processes before, and now they have created whirlpools through the impact of water currents to simulate the rapids in nature, and there is no need for manual intervention. According to his understanding, at present, chinese sturgeon has been successfully bred in captivity, but it has not yet been scaled up. And the Yangtze River white sturgeon because of the miss, everything is still zero. In addition to these well-known fish, such as bluestone crawlers and yellowstone crawlers, because they have not found a suitable "open bait", that is, breast milk, they cannot achieve artificial breeding; and the fry of the round-mouth bass will appear white spots on the body when they grow to the length of their fingers, and they will die in a few days, "more than ten years, or not conquered."
Excitingly, in a six- or seven-kilometer stretch of enclosed water between two hydropower stations in the middle of Hongya and Jiajiang in Sichuan Province, monitoring equipment is currently being installed, and Zhang Zhiying and his colleagues are preparing to release captive-reared sexually mature Dashi sturgeon. "There are both still currents and torrents in this section of the water, and it is hoped that they can mate and breed in them." The reason for the closed area is that it is easy to monitor, and the monitoring equipment on the shore receives the signal from the sonar installed on the fish. Through the artificial observation of the fish's activity trajectory in the water and the breeding period, the staff can understand their survival. However, monitoring the creatures in the water is more difficult than that of animals on land, and "it is already optimistic to expect to be able to mate and reproduce in the second year."
"This is the river dumpling that everyone usually eats, but now it is almost impossible to catch the wild." In the herbarium of the Sichuan Provincial Fisheries Bureau, Zhang Zhiying lamented that there are hundreds of endemic fish species in the upper reaches of the Yangtze River, and at least more than a dozen species he has not heard of in the wild for a long time.
Red Star News reporter Ye Yan Lin Cong photo report
Edited by Zhou Lin