Taihu Lake is one of the five famous freshwater lakes in China, and has been a well-known fishery production base since ancient times. The Taihu Lake Basin has a mild climate and a dense water network, with as many as 107 species of recorded fish, including not only the famous "Taihu Sanbai", but also valuable aquatic products such as eels, river crabs, and eels, and eels, which are highly praised in the market.
Satellite map of Taihu Lake
With its rich fishery resources, Taihu Lake has won the reputation of "Sunrise Doujin" and "Natural Live Fish Reservoir", and has also become an important economic source for the surrounding 14,000 fishermen. Domestic research on the fishery resources of Taihu Lake began in 1951, when fishermen along the Taihu Lake could earn a good income simply by catching wild fish.
However, like Poyang Lake, Chao Lake and Dongting Lake, the traditional fisheries of Taihu Lake are also facing many problems, especially since the beginning of the new century, the phenomenon of overfishing has become more and more obvious.
The "overdraft" of the Taihu Lake fishery should also start from the local fishing mechanism. After the reform of the Taihu Lake fishery, it has gradually formed a family-based fishing mechanism - which means that fishermen eat entirely on their own abilities, and the more fish they catch, the more they earn. In order to obtain the greatest economic benefits, fishermen continue to "pressure" the fish and shrimp in the lake, and this vicious competition is the beginning of the "bankruptcy" of the Taihu Fishery.
On September 1, 2006, fishermen in Taihu Lake fished more than 60,000 kilograms of lake fish
According to a recent survey report, more than 80% of fishermen in the Taihu Lake Basin are over 45 years old, the highest level of education is only junior high school, and about 60% of fishermen have only primary school education. It is undeniable that the "national fish reservoir" of Taihu Lake is related to the livelihood of many fishermen, but after decades of overfishing, the fishery resources of Taihu Lake have been seriously declined, and there are less than 50 common fish species (less than half of the recorded fish), which is an indisputable fact.
Since the liberalization of the price of aquatic products in Taihu Lake, the number of motorized fishing boats on the lake has been growing. In the 1970s, the number of motorized fishing boats on Lake Taihu was only 184, and in 1997 it increased to 4282. Today, there are more than 6,600 motorized fishing boats in the Taihu Lake basin – and the fishing intensity of fishermen has far exceeded the fishing capacity of Taihu Lake itself.
Based on primary productivity estimates, Taihu Lake can produce an average of 113.9 kg of aquatic products per hectare of water surface, according to this standard, the annual fishing output of the Taihu Lake Basin should be controlled at about 28,000 tons. However, since 2006, the actual catch in the Taihu Lake Basin has exceeded 35,000 tons, and in 2017, it reached 68,000 tons.
Overfishing in Taihu Lake has been going on for more than 20 years, and many economic fish have not yet grown to commodity size before they are caught and fished ashore and sold at low prices. If these juveniles are put back into the lake for a period of time, they can be sold for a higher price – for fishermen and Taihu fisheries, the depletion of juvenile resources is obviously a greater loss.
What is even more deplorable is that some irrational operation methods lead to the waste of catches is also very common. For example, in September every year, the fishing method of the high-stepping net will appear on the surface of Taihu Lake on time. In just 25 days, the high-end net can "net out" 60% of the lake's fishery resources, which will inevitably cause waste. Due to the small size of the mesh, the fry of many economic fish are also doomed, which is obviously not conducive to the sustainable development of fisheries.
Fishermen in Taihu Lake use high-stepping nets to catch fish, and the nets are dense, which can be called "absolute nets"
In order to "support" the fishery production of Taihu Lake, the fishery department will manually release a large number of silver carp, bighead carp, grass carp, carp and other fry every year. However, the survey shows that most of the stocked fry will be caught and landed in the same year, and the artificial release has not achieved the expected effect, and the "stock" of the remaining fish in the lake area is not optimistic.
Judging from the catch in recent years, miniaturization, low age and low value have become a phenomenon that can be seen everywhere, and the comprehensive income of fishermen is not ideal. Fortunately, from October 1, 2020, the Taihu Lake Basin officially began a ten-year fishing ban period, including four large fish, economic fish will receive at least 2 to 3 breeding cycles, and the indigenous fish in Taihu Lake will have enough time to recuperate.
Since the beginning of this year, the problem of overfishing has no longer become a problem for the Taihu Lake fishery, and fishermen have washed their feet and gone ashore to find another way. Today, what really brings a crisis to the ecology of Taihu Lake is the eutrophication pollution in the lake - like the "nutritional disease" of ChaoHu Lake, the cyanobacteria outbreak in Taihu Lake is also a rather stubborn "old disease".
Since the 1980s, cyanobacterial disasters in Taihu Lake have occurred frequently, and the water quality of the lake has been deteriorating. It should be pointed out in particular that although the lake area of Taihu Lake is as much as 2427 square kilometers, the average water depth is only 1.89 meters, and the water exchange and self-purification capacity is low, which is also the "hard wound" of Taihu Lake.
The range of cyanobacterial eruptions is so large that they are clearly visible in satellite imagery
Eutrophication has a big impact on fishery resources in lakes, such as changing the size of fish populations – the most typical case is the lake squid. With the increasing eutrophication of Taihu Lake, the plankton in the lake continues to multiply and the biomass is extremely abundant, which provides a large amount of basic food for the growth of lake sturgeon.
The main fish produced in Taihu Lake were originally four large fish, but the lake fish used the "east wind" of plankton to increase production and eventually succeeded in "ascending". In 2008, the proportion of lake fish in the catch reached 63%, becoming the absolute dominant species in Taihu Lake. Silver carp, bighead carp, and silverfish also feed on plankton, and production increased during this period.
Therefore, proper eutrophication is not a bad thing, it is good for the increase in fishery production, but once the pollution is excessive, it will lead to cyanobacterial outbreaks (also known as "blooms"), which can turn into a disaster.
Cyanobacteria erupt in Taihu Lake, and fishermen are struggling to salvage
Cyanobacteria is a very headache of algae, common algae species such as aeruginosa microcystis, fibrillary algae, candida algae and so on. The algal toxins in cyanobacteria have a toxic effect on humans and aquatic organisms, so every cyanobacteria outbreak is a big impact on the fish and shrimp in the lake. In order to control the cyanobacteria disaster, experts have come up with various methods, the most noteworthy of which is the atypical biological manipulation technology of controlling cyanobacteria with silver carp and bighead carp.
It is a common practice to use silver carp to regulate water quality. After people introduced silver carp and bighead carp in Wuhan East Lake, the cyanobacterial blooms in East Lake did disappear in a short period of time; from 1998 to 1999, the cyanobacterial disasters in Qiandao Lake for two consecutive years were also solved by stocking silver carp and bighead carp. With these experiences, increasing the stocking density of silver carp in Taihu Lake has become the preferred way to control "blooms".
silver carp
Since 2013, the Taihu Lake Fisheries Management Committee has used silver carp as the "main force" to control cyanobacteria, a technology known as "fish control of algae". Since 2014, the stockpillars of silver carp and bighead carp in Taihu Lake have reached nearly 500 million, and the cumulative consumption of algae is 6.58 million tons, which has achieved very good ecological and economic benefits.
The monitoring results show that after 10 months of growth, the average weight gain of fry is more than 20 times. In the waters of Meiliang Lake and Zhushan Lake, the density of phytoplankton has decreased by 42.67%, which shows that the inhibition effect of silver carp on algae in Taihu Lake is still quite obvious.
With the full implementation of the 10-year fishing ban plan, the "nutritional disease" of Taihu Lake will surely change greatly - after all, the ecological protection along the Yangtze River has been placed in an overwhelming position, and the next ten years will be a great opportunity for ecological governance of Taihu Lake.
Can the silver carp and bighead carp in Taihu Lake play the magical effect of the "Qiandao Lake Mode"? We'll see!
What do you think about the fisheries and ecology of Taihu Lake? Feel free to leave a message in the comments section to discuss!
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