Speaking of knife fish, many people first think of the Yangtze River knife fish, one of the "three fresh yangtze river". In fact, knifefish is not only a specialty of the Yangtze River Basin, but also has the distribution of wild knifefish in the Yellow River Basin in the north, and the historical fishing production is not low, and the economic value is also very high.
Knifefish (Coilia nasus)
In the 1970s, the Yellow River knifefish was harvested at 1.5 million kilograms, making it one of the most common economic fish in the entire Yellow River Basin. According to old fishermen near the mouth of the Yellow River, the price of Yellow River knife fish in the 1970s was very cheap, and it was only a dime a pound. Now, wild Yellow River knifefish are very rare, and occasionally catch one and even sell for thousands of yuan.
<h1>Yellow River knifefish in crisis</h1>
Corresponding to the "river knife", "lake knife" and "sea knife" in the Yangtze River Basin, the knife fish in the Yellow River Basin is called "river knife". Every year around the Qingming Festival, knifefish at the mouth of the Yellow River will swim upstream, migrating for more than 400 kilometers.
Schematic map of the Yellow River Basin
Adult Yellow River knifefish are generally 30 to 40 cm long and weigh about 200 grams. Wild Yellow River knifefish grow slowly and take at least 2 to 3 years to mature. Common knifefish are generally no more than 500 grams in size, and knifefish weighing more than 1 kilogram are even rarer – according to old fishermen, such giant knifefish can be regarded as "head knives", and in the eyes of diners, they are also the best knifefish.
During the migration, the Yellow River knifefish rarely eat, but the physical exertion is very large, so the more upstream the knifefish, the thinner the body and the harder the intermuscular spines. The vast majority of Yellow River knifefish migrate to Dongping Lake and stay, spawning and breeding in the lake, and a small number of groups will continue to migrate to Henan.
Fishermen use gillnets to catch knifefish
Dongping Lake in Shandong is the most important spawning ground for yellow river knifefish and the most important "shelter" for this population. However, in the 1980s, the Yellow River knifefish resources declined surprisingly quickly, and this species also faced an unprecedented existential crisis. Not only the Yellow River knifefish, but also other migratory fish in the Yellow River are facing a similar fate, mainly for two reasons: one is the construction of the gate and dam in the eastern section of the Yellow River, and the other is the regular interruption of the Yellow River, both of which have led to the blockage of the migratory passage of the fish, and a large number of broodstock cannot reproduce smoothly.
In addition, the "encirclement, pursuit and interception" of fishermen in the Mouth of the Yellow River and along the Yellow River also has an unshirkable responsibility (especially in the Mouth of the Yellow River). Formal fishing operations are not too much of a problem, but the practice of "catching the big and leaving the small" cannot be implemented to every fisherman, and many fishermen will not hesitate to "take risks" in order to pursue economic interests, and even use electric fish, poisonous fish, and the use of "nets" to catch fish. From the perspective of resource recovery, these extreme approaches are neither wise nor responsible.
<h1>The Yangtze River knifefish is strongly "on the top", and the south water is diverted to the north into the second "lifeline"? </h1>
With an area of 627 square kilometers, Dongping Lake is the second largest freshwater lake in Shandong Province and has always been an important local fishing production base. According to statistics, there are 55 kinds of fish in Dongping Lake, including many economic fish with high economic food value, such as carp, blackfish, crucian carp, catfish, yellow eel, mandarin fish, etc., of course, there are also Yellow River knifefish that migrate here.
Satellite map of Dongping Lake
In particular, there are two different ecological types of knifefish in Dongping Lake, one is migratory (long-jawed squid) and the other is freshwater settlement (lake mackerel, short-jawed squid) – as the name suggests, the latter has always lived in the lake area and has not undergone long-distance migratory migration in its life history. Although the names of the two are different, after genetic identification, experts found that the two knifefish are actually the same species.
The question is, why are there two types of knifefish in Dongping Lake? This phenomenon should also start from the "South-to-North Water Diversion Project".
Since 2000, with the continuous advancement of the "South-to-North Water Diversion Project", knifefish stocks from the Huai River and Yangtze River basins have begun to spread to the North Dang area, and many of them have settled in Dongping Lake. Dongping Lake was originally an ideal spawning ground for the Yellow River knifefish, with plenty of food, and the knifefish from the south soon prospered and grew, and the proportion of fish in the catch increased year by year.
Fishermen catch knifefish
Even now, the production of knife fish in Dongping Lake is still very high. However, migratory knifefish in the lake are very rare, and the vast majority of knifefish are settled. Due to the lack of long-distance migration, the settled knifefish population is not really a "river knife" in the true sense of the word, and it is more appropriate to call it a "lake knife".
Some people say that since the migration path of the fish was cut off by the sluice dam, the "South-to-North Water Diversion Project" has become the second "lifeline" to save the Yellow River knifefish. There is some truth to this statement, but it is not entirely true.
First of all, the knifefish (lake fish) migrating from the southern water system cannot be directly equated with the "Yellow River knifefish", and there are obvious differences in the life history process between the two. Secondly, the knife fish that has undergone long-distance migration is better than the sedentary knife fish in terms of taste and flavor, and its status in the hearts of local fishermen and consumers is also significantly higher. In addition, in terms of economic value, the Yellow River knifefish is also significantly higher than the lake fish, the former has long been "difficult to find a fish", and the latter is quite common.
<h1>The last "self-reserved land" of the Yellow River knifefish</h1>
Dongping Lake is the flood detention area of the Yellow River, which plays a very important role in regulating the floods of the Wen River and the Yellow River. Therefore, China has invested a lot of money to repair the embankment and build the gate, but the construction of water conservancy projects is tantamount to pronouncing a "death sentence" on migratory fish.
Yellow River Dam
Over the past 40 years, the production of species such as Yellow River carp, Yellow River knifefish, red bass and eel has declined dramatically – especially the Yellow River knifefish and eel, whose natural populations are almost extinct. It is certain that the "endangered species defense war" in the Yellow River Basin is imminent, and there is no doubt that Dongping Lake is one of the most important "battlefields".
Back 10 years ago, the surface of Dongping Lake was still densely packed with bamboo poles and purse seines, and local fishermen stocked fry and fed feed in the purse seines, a "hot and hot" breeding scene. Monitoring data from 2008 show that the water quality of Dongping Lake was often in a state of serious pollution at that time, and the sources of pollution included large-scale purse seine farming and agricultural non-point source pollution in addition to industrial wastewater and municipal domestic wastewater.
In July 2011, Dongping Lake was full of purse seine culture
By 2017, the local government began to control the ecological environment of Dongping Lake, dismantling as much as 18,500 mu of seine nets and removing more than 9,600 cages. By 2018, the purse seines and cages in Dongping Lake were completely dismantled, and the intensity of breeding and stocking was also increasing.
In short, improving the ecology is the first and most critical step in saving the Yellow River knifefish. As for the migration channel, many people may think of solving it by building a "fish road" - this way is theoretically possible, but China's current fish road engineering technology is not perfect enough, and the newly built fish road can rarely achieve the expected effect.
Schematic diagram of the principle of the fish road
At this stage, China has become the country with the largest number of large-scale water conservancy facilities in the world, with nearly 100,000 dams of various sizes and storage capacity of nearly 900 billion cubic meters. However, many large and medium-sized hydropower projects in China did not take into account the problem of fish roads before construction, and only nearly 20 fish road projects have been built or are planned.
Compared to the huge base of hydroelectric dams, the number of fishing facilities can be said to be negligible – which is obviously a very embarrassing situation, but also exposes serious ecological problems.
fishway
Although the investment cost of the fish channel is large, it is a permanent building connecting the reservoir and the river under the dam, which is of great significance for the conservation of rare fish resources. In the long run, the design of the fish road is definitely worth studying, which is not only related to the recovery of the resources of the Yellow River knifefish, but also related to the survival fate of dozens of endangered species such as Chinese sturgeon, round mouth copper fish and even Yangtze River anchovies.
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#Yellow River knifefish ##Protect ecology ##渔业 #