A large number of wild fish appear again in the Yangtze River Basin!
Recently, swarms of wild fish appeared in the waters of Qingjiang River, Yuxiakou Town, Changyang Tujia Autonomous County, Hubei Province. The water in Qingjiang is clear and highly transparent. The fish swim freely close to the water surface, splashing water from time to time. The scene is attractive. Invigorate.
This batch of fish schools is huge, and "black fish balls" are formed on the water surface. According to estimates from the local fishery department, the total weight of the fish school is about 150 tons. Based on the average weight of each fish of 5 kilograms, the number of river fish is about 30,000, and the resource density is considerable.
It can be clearly seen from the video that most of the fish schools are composed of silver carp and bighead carp. The back of the fish body is dull and gray-black in color, and the snout has a large cleft. The scene is quite spectacular. Such a large school of fish in is very rare, and what is the reason behind it?
First of all, it is because fish in the Yangtze River are in the ten-year fishing ban protection period. Overfishing in "One River and Seven Rivers" no longer exists, and the tributaries of the Yangtze River have also been protected with unprecedented intensity. Otherwise, the prosperous fish stocks may have become A fisherman's bag.
Secondly, the proliferation and release of in various places has begun to take effect. Silver carp and bighead carp are the conventional and main released fish species. As a recognized "water purifier fish", silver carp and bighead carp also have the potential to "explode fish schools": they have a short reproductive cycle, can lay eggs up to 1 million, and they also have the habit of swimming in groups. Therefore, in many incidents where fish schools emerge, the protagonist is often "either silver carp or bighead carp". This is the case with the Qingjiang fish school this time.
Finally, there is a very important point, which is related to reproduction and foraging. Silver carp and bighead carp are semi-migratory fish that reproduce in the main streams of rivers. They can lay eggs and throw seeds when the water temperature reaches 18~25℃. From May to July every year, the temperature range in the Yangtze River and lakes generally rises to this range, and the peak breeding period comes. With the massive reproduction of algae and the increase in primary productivity, wild fish in various parts of the Yangtze River have also entered an active period of foraging.
Interested friends may have noticed that recently, fish schools in the Yangtze River Basin often appear in "gatherings". From the Three Gorges in the upper reaches to the Yangtze Estuary in the lower reaches, good news frequently comes from the river section of more than 1,700 kilometers, for example:
Anhui There are a large number of restless fish schools in the waters at the Huangpen Gate, and the hundreds of meters long river section is full of mature big fish; the Shili River Bay in Wuhu, Anhui also welcomes a large school of fish, including grass, carp, crucian carp, and bream. Most of them, local managers said, were rare to see in 50 years; hundreds of silver carp jumped out of the water in the Zhenjiang section of the Yangtze River. This scene happened to be photographed by the fishery officials on inspection, and the people present could not hide their excitement.
Most netizens expressed angry praise for this, but some netizens expressed concern: the fish in the Yangtze River have shown an "explosion" trend! There have been so many fish since the fishing ban lasted just over a year. If the ten-year fishing ban ends, won’t the fish in the river flood and cause an ecological tragedy?
In fact, this kind of worry is completely unnecessary. At this stage, the Yangtze River ecology is still in the recovery stage, and the fish integrity index is not as good as it was in the 1990s. Talking about "flooding" is not only premature, but also unnecessary.
Because the Yangtze River is a complete ecosystem, there are more than 4,300 kinds of aquatic organisms and more than 400 kinds of fish, including herbivorous, carnivorous, filter-feeding fish , and the ecological chain is linked together. Various fish species restrict and compete with each other, and there is no risk of flooding.
Even alien species that have jumped out of the native ecosystem will find it difficult to dominate the Yangtze River where there are so many experts. Take tilapia , mosquitofish and other fish species as examples: first, they must overcome the low-temperature hydrological conditions of the Yangtze River, and secondly, they must complete the four stages of introduction, colony establishment, dispersal and invasion, and the success rate is very low. According to ecologist Williamson's "one-tenth rule", the probability of alien species forming harmful invasive species is about 1/1000, which is almost negligible.
Since the fishing ban, the biodiversity of the Yangtze River is increasing, and there is no high-risk flooding problem of native fish and exotic fish.On the contrary, what is worth worrying about is the survival of endangered species in the Yangtze River, because from the perspective of biodiversity, the current Yangtze River has not yet gotten rid of the "fish dilemma."
What is "fish trap"? From the monitoring of fish resources in the Yangtze River, we can get a glimpse of the whole situation.
In 2021, Professor Wei Qiwei and veteran fisherman Master Zheng conducted fishery monitoring in the Yangtze River. The fishing operation lasted all morning. In the end, the long net of hundreds of meters only harvested 5 to 6 kilograms of fish, and the sizes were generally small. The fish caught are all indigenous fish in the Yangtze River, including mandarin fish, copper fish, trout, longnose bream, etc. The longest one is only 20~30cm.
According to the price of ten yuan per catty, this batch of fish can only be sold for fifty or sixty yuan, and traditional fishermen cannot survive on this. If fishing is no longer prohibited, there will only be fewer and fewer fish in the Yangtze River. The necessity of banning fishing is self-evident.
said at the beginning that fish stocks in the Yangtze River have increased, but here he also said that the fish catch has decreased. Is this contradictory? This is not the case. Because the effects of the Yangtze River fishing ban are reflected differently in different fish species. The first to see the effects are fish with short life cycles, such as the Yangtze saury.
Swordfish is one of the " Yangtze River Three Fresh Foods ". In the 1990s, the population began to experience sexual maturity in advance. It has the ability to reproduce at the age of 1 to 2, and the amount of eggs it lays is considerable. In addition, the number of dry spawning grounds There are many, so recovery is fast. The survey in the Jiangsu section also showed that the number of migratory saury in the same section of the river increased 2.5 times compared with previous years, and the resource density increased significantly.
But for organisms with long life cycles, the recovery effect is very limited. For example, the Chinese sturgeon, known as the "King of Fish in the Yangtze River", takes 9 years at the earliest for male fish to mature, and at least 14 to 16 years for female fish, which is not even enough to breed once during the fishing ban. The "Goddess of the Yangtze River" Baiji dolphins are also "late maturing" and can reproduce only after they are 6 to 8 years old. They reproduce every two years and only give birth to one cub each time.
Therefore, the effect of the Yangtze River fishing ban "varies by species." The higher the trophic level and the longer the reproductive cycle of an organism, the more difficult it is to recover in theory, and the harder it is to see the corresponding group.
In fact, to determine the overall effect of the Yangtze River fishing ban, it is necessary to carry out resource surveys in the entire basin, compare historical and current fish species and quantities, outline the ecological outlines of different periods, and comprehensively assess the health of the Yangtze River ecology. , the resulting data and conclusions are representative.
Fish resources in the Yangtze River have changed greatly. Can fish stocks still appear commonly?
Many friends have no intuitive impression of the Yangtze River fishery. At its peak, the Yangtze River was a paradise for wild fish, and the richness of its resources was no less than that of Beidahuang, where people beat roe deer with sticks and scooped fish with gourds.
In the 1950s, the main stream of the Yangtze River could catch up to 430,000 tons of fish a year. Fish stocks in the river were common. The Yangtze River anchovy and Yangtze saury fish floods were huge and huge. Thousands of fishing boats were spread across Jiangsu and Anhui. , Jiangxi, Hunan, Hubei and other river sections. In the words of an old fisherman: "If the net is used, the weight of the catch will not even be bearable by the boat." However, this scene can only be understood at present.
Can thriving fish schools still appear commonly in the main stream of the Yangtze River? Similar scenes may appear again in , but certain fish schools will never return. The typical case is the Yangtze River shad.
Anchovy The fishing output of anchovy in the Yangtze River once reached 1,575 tons, and a single anchovy can exceed 4 kilograms. The last anchovy was discovered in the Anhui section of the Yangtze River in 1994. It has been extinct for nearly 20 years, and the fish population has recovered again ( fish flood ) The possibility is slim.
The Yangtze River’s “fish dilemma” focuses on saving endangered species. Once germplasm resources are lost, there is no possibility of recovery in the future. During the current fishing ban period, the protection of endangered fish species should be given full attention.
From 2017 to 2020, our country’s scientific research institutions launched a resource survey in the main stream of the Yangtze River. The results showed that among more than 400 species of fish in the Yangtze River, more than 30% are facing a survival crisis, and nearly one-third of the fish species have been in decline for four consecutive years. It has not been detected in surveys for years, indicating that its population has been severely reduced.
We don’t have to be too pessimistic about species that have been extinct for many years. The ban on fishing in the Yangtze River has improved the water environment and increased the possibility of endangered species reappearing. The appearance of the "mysterious species" anchovy in the middle reaches of the Yangtze River is strong proof.
Finally, I borrowed the opinion of experts and professors: Now the technology has matured. As long as we find another paddlefish, we can restore its population, and the same may be true for the Baiji dolphin. For the endangered elves in the Yangtze River, we might as well retain our expectations and hope that we still have a chance to meet them in the near future.
