Chaohu City is named after Chaohu Lake, its written history of about 4,000 years, Chaohu Lake has a unique geographical location, on the map of the Land of China, the great rivers and lakes meet here, and the culture of Jiangnan and Jiangbei gathers here. The miraculous creation of nature has made Chao Lake a "land of fish and rice" in the north of the Jiangsu River, and the water of Chao Lake in the Yangtze River has nurtured generations of coastal residents, and has also left a precious natural and historical heritage for today's Chao Lake.
Chao Lake, together with Poyang Lake, Dongting Lake, Taihu Lake and Hongze Lake, is listed as one of the five major freshwater lakes in China, and its main aquatic products are silver fish, beautiful white shrimp and lake crabs, which are known as the "Three Fresh Foods of Chao Lake". In addition, in the fish stocks, the lake mackerel dominates the production of the Chao Lake fishery. Red carp, "four big fish", carp, crucian carp and other fish are all high-quality fresh stocks in Chaohu Lake.
< h1 class="pgc-h-arrow-right" > the fish of Chao Lake</h1>
As early as the 1950s, the annual fishery output of Chaohu Lake reached 3500 to 4000 tons, and the main fish were planted with four major fish, as well as lake mackerel, red carp, silver fish and so on. These fish are the foundation of the fishermen's survival in Chaohu Lake, and are the most important economic source for thousands of fishery workers in 18 townships around the lake.
Whitebait
Silver fish is the most famous specialty of Chaohu Lake, it is a very calcium-rich, high-protein, low-fat fish, the whole body is almost transparent, there is no fish spines, suitable for children to eat. In 1996, chaohu silverfish produced 169 tons, and by 2013, the growth area of chaohu silverfish was 750 square kilometers, with an annual output of about 600 tons.
Lake bream
Lake fish is a kind of knife fish, and although the knife fish in Chao Lake is not as famous as the Yangtze River knife fish, it is also the pillar fish of Chao Lake. It feeds on small fish, shrimp, fish eggs, aquatic insects, zooplankton, algae, aquatic plants, etc., and has a huge stock in Chao Lake. According to modern nutritional analysis, the protein and fat content in the muscles of lake trout is significantly higher than that of other conventional economic fish, and it is an excellent economic fish. Locals call this fish a hairy fish, because of its characteristics of dying when it comes out of the water, it is generally dried and sold. Pickled and dried and stir-fried with green and red peppers, it is a rare delicacy.
The local management department has long taken precautions for the sustainable development of Chao Lake. As early as 1984, Chaohu Lake took the lead in implementing the seasonal closed lake fishing ban period system among many lakes in the Yangtze River Basin, and has been adhering to it for more than 30 years. For more than three decades, the seasonal closure of Chao Lake and the increase and stocking of Chao Lake in recent years have restored the fishery resources of Chao Lake and have not faced depletion like other lakes. But it is not enough to increase and release, the problem of fish is solved, and the problem of water comes again.
<h1 class= "pgc-h-arrow-right" > the water of Chao Lake</h1>
Chaohu Lake was originally an important water source for Hefei and Chaohu City, but in recent years it has been particularly polluted, especially in the Tangxi waters of Hefei's drinking water source.
There are three main reasons for the pollution of Chao Lake:
1. A large amount of industrial wastewater is discharged into Chao Lake. According to incomplete statistics, Chaohu has more than 50 large and medium-sized enterprises in the city, as well as a number of listed chemical enterprises, in the 90s of the last century, a large number of industrial sewage was directly discharged into Chaohu lake without treatment. Although all units have rectified the discharge of pollutants, the pollution problems left behind in the early years cannot be eliminated in the short term.
2. Discharge of urban domestic sewage. Most of the city's domestic sewage is directly discharged into Chao Lake, and residents along the lake discharge about 100 million tons of sewage to Chao Lake every year. Hefei is crossed by the Nanmi River and the Fifteen Mile River, both of which eventually merge into Chao Lake, where pollution problems are obvious, with domestic and medical waste floating in the water all year round, and pet rotting corpses from time to time.
3. Farmers along the lake use pesticides and fertilizers in large quantities, and over time, they flow into Chao Lake to form pollution.
The water quality of Chao Lake is polluted by nitrogen, phosphorus nutrient salts and oxygen-depleting organic compounds, and the comprehensive water quality of the whole lake is inferior to the ground class V water standard, mainly because the total nitrogen and total phosphorus exceed the standard, and the whole lake is in a state of eutrophication.
In 2016-2018, the production of major fish such as Chaohu specialty "three fresh" and big fish has declined to varying degrees, among which, hair fish fell from 15735 tons in 2016 to 7627 tons, silver fish fell from 678 tons to 567 tons, shrimp fell from 4094 tons to 3443 tons, and big fish fell from 4637 tons to 2962 tons.
<h1 class="pgc-h-arrow-right" > a bloom in Chao Lake</h1>
In the summer of 2007, a serious bloom broke out in Chao Lake, floating on the surface of the water with paint-like green cloth and emitting a strong fishy odor, and even the appearance of dead fish with white bellies from time to time. It was also in that year that China listed Taihu Lake, ChaoHu Lake and Dianchi Lake in the national pollution control project of "Three Lakes Governance", and the "nutritional disease" of Chaohu Lake became a major problem related to the national economy and people's livelihood.
Due to the eutrophication of the water quality, the fish in the water cannot digest, allowing the cyanobacteria to grow explosively, forming a layer of blue-green and foul-smelling foam on the surface of the water, which is what fishermen call blooms. The common cyanobacteria in Chao Lake also include fibrillary algae, fishy algae, aeruginosa microcystis, etc. The large number of cyanobacteria worsens the ventilation, light and lack of oxygen in the water, resulting in the growth and reproduction of plankton in the water, thereby hindering the photosynthesis of the algae. And these algae in Chao Lake have cyanobacterial toxins, and animals may be poisoned if they eat algae containing cyanobacterial toxins, and they will die within a few hours, and the fish and shrimp in the lake will also die in large quantities. Whenever cyanobacteria erupt in summer, the fishy smell of cyanobacteria and the putrid smell of dead fish and shrimp are mixed and fermented, making the entire Chao Lake shore smell unstoppable.
Zhejiang's Qiandao Lake has also had many outbreaks of blooms, and later the local biological control methods have been adopted for treatment, silver carp and bighead carp to filter the plankton in the water as bait, every kilogram of growth, can consume nearly 40 kg of blue-green algae, a large number of silver carp into the breeding effectively improve the water purification capacity, so that the water quality of Qiandao Lake has been greatly improved. However, Qiandao Lake is small in size and has outstanding self-purification ability in deep water, while Chao Lake is large in area and shallow in water, relying on increasing the number of silver carp to control cyanobacterial blooms, and the effect is extremely limited.
<h1 class= "pgc-h-arrow-right" > pollution control still needs a long time</h1>
In recent years, Hefei has established the Chaohu Lake National Ecological Civilization Pilot Demonstration Zone, comprehensively established the "lake chief system", spent more than 20 billion yuan to continuously implement the ecological protection and restoration project around Chao Lake, during the "Thirteenth Five-Year Plan" period, the water quality of Chao Lake has reached the best level since the monitoring record was recorded in 1979, and the water quality of the lake and the river has continued to remain excellent. In 2020, the water quality of ChaoHu Lake improved from inferior class V. in 2015 to class IV.; the biodiversity of the basin gradually recovered, and the oriental white stork, known as the "national treasure", reappeared in the wetlands of chaohu peninsula.
Although the water quality has greatly improved, the "nutritional disease" for many years has not been treated overnight. The source of pollution should be treated, the protection of wetlands should be paid attention to, the breeding and stocking should be sustained, and the ten-year ban on fishing must not be discounted.
When the 2022 River Introduction Jihuai Project is completed, the Yangtze River and Chao Lake will be connected again, the exchange of rivers and lakes will greatly improve the water purification capacity of Chao Lake, and the comprehensive treatment of Chao Lake is expected to usher in an inflection point.
postscript
After the complete ban on fishing in Chao Lake, I occasionally go to some tributary small rivers for wild fishing, in the summer of 2020, Anhui suffered a hundred years of no major floods, the water level of various rivers grew wildly, the fish in Chao Lake all ran into the small river, my companions and I harvested a lot, and also obviously felt the increase in the number of fish in Chao Lake. The cyanobacteria of Chaohu Lake still erupted this summer, and the entire Binhu New Area was filled with a foul odor. Interestingly, due to the relocation of Hefei Provincial Government and various construction plans, the Binhu New Area near Chaohu Lake has become the fastest growing place in Hefei, and the binhu one-bedroom room that is filled with a foul smell for half a month is difficult to find, and the price has soared. Some people joke that there is a set of real estate in Hefei that can smell the stench of Chaohu Lake, which is also a symbol of the identity of Hefei people.
The fishing ban is still continuing, fishermen have come ashore, and various pollution control work has continued to be carried out, I believe that after 10 years, Chao Lake will be brilliant again, and then we will witness it together again.