Speaking of Qiandao Lake, the first thing that comes to mind may be organic silver carp, and the word "organic" has long become the consensus of consumers. The silver carp produced in Qiandao Lake is tender and delicious, and it is widely welcomed by the market, and the water quality here is also well-known in China.
Qiandao Lake is a national first-class water source, the water quality is maintained at the level of national surface water 1 to 2 all year round, is the largest freshwater artificial lake in the Yangtze River Delta region, and also plays the heavy responsibility of strategic water source. The water body in the reservoir area is refreshing and blue, the transparency is high, and the deep water can be directly drunk, which is an important source of drinking water for Hangzhou citizens.
With excellent water quality and leading the country's "water-retaining fishery", the silver carp of Qiandao Lake not only preserves the ecology, but also turns the "green water and green mountains" into "golden mountains and silver mountains", creating considerable wealth and truly realizing "raising water with fish and enriching the people with fish". In October this year, CCTV media once again focused on organic fish in Qiandao Lake, with giant net fishing as the highlight, which once again attracted the attention of all sectors of society.
<h1 class="pgc-h-arrow-right" data-track="40" > giant net fishing in Qiandao Lake</h1>
Qiandao Lake, also known as Xin'an River Reservoir, was officially intercepted by the dam in 1959 and has been storing water for more than 60 years. Taking the yellow sea elevation as a reference, the design water level of the reservoir area is 108m, and the water storage area is about 580 square kilometers, which is under the jurisdiction of Zhejiang and Anhui provinces. Qiandao Lake belongs to the valley type deep-water reservoir, with an average water depth of more than 30 meters, from a high altitude, it can be seen that the islands are dotted with dots, the shoreline is meandering, and the reservoirs are staggered and interconnected, which is very suitable for the development of fisheries.
The giant net fishing in Qiandao Lake seems easy, but it is actually full of wisdom and experience. Different from other reservoirs, there are as many as 1078 islands of more than 3 acres in Qiandao Lake, the water surface is relatively scattered, the bottom of the reservoir is uneven, and the landform and terrain are complex, which brings great difficulties to fishing activities. In 1962, after two years of hard work, the Freshwater Fisheries Research Institute of Zhejiang Province and the local fishery farm finally explored the joint fishing method of "stopping, catching, stabbing and zhang", which achieved great results.
There are more than 100 people in the Qiandao Lake fishing team, which are specially equipped with netting classes, zhang net classes and gillnet classes, as well as transportation classes, cooking classes, and even special shipyards, weaving net factories, refrigeration plants and cannery factories, with comprehensive configuration, high efficiency and strong professionalism.
Fishing team members have been dealing with fish for many years, and they are experienced and can identify specific fish species through eyes and ears. For example, silver carp generally make a "popping" sound when they jump out of the water, bighead carp have a "grunting" sound, carp has a "crackling" sound, and eels have a "whooshing" or "booming" sound. For example, in the spring, the jumping sound of carp and silver carp is very similar, which can be judged by combining the terrain. If you take off at the shoals of the island, most of them are carp, and if you take off in deep waters, 80% of them are silver carp.
With the ability to "listen to the sound and identify the fish", it is far from enough. In the actual fishing, the investigators also need to have a detailed understanding of the landform, area, water depth and other conditions of the operation fishing ground, so as to determine the location of the net, gillnet and the lower net of the net, and the length and height of the various nets should also be known.
When silver carp and bighead carp gather on a large scale, it is a great time to catch. Generally speaking, when the water rises upstream of the reservoir, the broodstock will habitually rise to the water, resulting in migratory behavior, large and neat size, and large numbers. At this time, the fishing team first surrounds the fish through the net and gillnet, and then drives the fish in a directional manner, and finally kills the broodstock in the net.
From May to September of each year, the water temperature gradually rises, and the silver carp enters an active period, accounting for more than 80% of the total annual production in these five months. It is worth mentioning that the fished silver carp is basically above 6 kg, because the net of the net is controlled at about 15 to 18 cm, and the silver carp below 6 kg can leak out of the net, avoiding small fish entering the net and ensuring the sustainable use of fishery resources.
<h1 class="pgc-h-arrow-right" data-track="68" what's the mystery of "organic fish" >? </h1>
At the autumn equinox of this year, the Qiandao Lake reservoir area was boiling, and a huge net was salvaged with 120,000 kilograms of silver carp, and the mainstream domestic media rushed to report it. In fact, such a harvest scene is very common, in recent years, the annual output of Qiandao Lake has reached 6 million kilograms, and the "Chun" brand organic fish is full of stamina and is highly sought after by the market.
However, some people think that the organic fish of Qiandao Lake are "not simple": there are big fish to catch every year, and there are more than 100,000 kilograms in a net.
In fact, the secret of qiandao lake to maintain high yields is not complicated, artificial release, orderly fishing is the focus.
As early as 1964, the local fishery has begun to cultivate fry independently, and now it has perfected the three-level cultivation technology of summer flowers, winter flakes and old-mouth fish species, and the discharge flow has been greatly improved. In recent years, more than 10 million fingerlings have been stocked in the reservoir area, and the weight of fish species has exceeded 1 million kilograms!
In terms of fishing specifications, fisheries have also set strict restrictions, silver carp starting at 3 kg and bighead carp at 4 kg, strictly limiting production and not overfishing. Each catch is basically a big fish, which ensures that there are enough young fish species in the reservoir area.
The organic properties of The Qiandao Lake silver carp are also "insured":
First of all, the silver carp in Qiandao Lake passed the national organic food certification as early as 2000. The certification puts forward strict controls on water quality, bait, breeding, fishing and other aspects to ensure quality and safety.
Secondly, the local county-level fishery administration bureau and the farm supervise the whole process, and it is strictly forbidden to use laokou cages for "fish washing" operations. In the northwest of the lake area, 7 fishery management groups are waiting in a strict line, leaving no dead ends in supervision, and will conduct random inspections from time to time every month to ensure that there is no room for "bathing fish".
Finally, the organic fish of Qiandao Lake is a "traceable fish". From fingerling breeding to natural stocking, production files and responsibility systems have been established, and signs have been set up in Laokou cages; and drug residue testing is carried out uniformly before fish fingerlings are put into storage, which ensures quality and safety while ensuring production capacity and meets "organic" standards.
<h1 class="pgc-h-arrow-right" data-track="69" > Why stock fish species in Qiandao Lake? Can't broodstock reproduce naturally? </h1>
Before the xin'an river dam was built, the upper reaches of the Qiantang River were interconnected and the water flow was unimpeded, and the silver carp at that time was able to reproduce naturally. However, after the dam was built, the water flow in the reservoir area was cut off, the broodstock lacked water flow stimulation, and it was difficult to reproduce even if the gonads were mature.
Silver carp and bighead carp are typical semi-migratory fish. In the Yangtze River, Xiangjiang River and other open water systems, mature silver carp will swim upstream in the spring every year, migrating tens or even hundreds of kilometers upstream to spawn. During migration, continuous water flow stimulation and suitable water temperature can promote the development of the female's ovaries from stage IV to mature stage V, which is a hard indicator of ovulation in females.
Still water area in front of the dam
After the completion of the Xin'anjiang Dam, the water flow in the reservoir area slowed down, and a still water area was formed in front of the dam. Only in April to June of each year, when there is more water in the upstream Anhui section and there is a rising water process, the broodstock will rise to the water and a large group of spawning groups will appear. However, due to the short migration distance, the peak of the flood is too small, the water flow stimulation is not enough, the ovaries cannot transition to the Vth stage, and natural reproduction is interrupted.
Therefore, silver carp can only be stocked through stocking to achieve resource growth. It is gratifying that the released silver carp has neat specifications and high survival rate, successfully provoked the "girder", and the ecological benefits are also very significant.
Take the Anhui section of Qiandao Lake as an example, which is located in the northwest of the lake area, with more pollutants and prominent eutrophication problems, but also more abundant bait. The old-mouth culture cage of silver carp is located here, and the fry absorb a large amount of nitrogen and phosphorus by feeding on algae and organic matter, improving water quality. It is estimated that 800 tonnes of fry can take 23.5 tonnes of nitrogen and 1.08 tonnes of phosphorus from the Northwest Lakes region each year, purifying water quality and increasing yields.
It is worth mentioning that not only silver carp but also detritus-eating fish such as fine scaled carp and yellowtail carp are released in the reservoir area, which has made an important contribution to alleviating the crisis of nitrogen and phosphorus. In the future of Qiandao Lake, silver carp is still the main force, as for the effectiveness of water control, we will wait and see!
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