Large silver fish is a small economic fish unique to East Asia, and is considered a high-end tonic in Countries such as South Korea and Japan, and is highly sought after by consumers. In China, the silver fish is also a favored aquatic product, and its distribution range extends from the Heilongjiang River to the south to the Yangtze river and pearl river basins.
Wild silver fish caught by fishermen in the Three Gorges
In 1985, the first successful transplant trial of large silver fish in China was carried out by the Sericulture College in Suzhou and the transplant site in Daihai, Inner Mongolia. Dai Hai is a highly alkaline lake, pH up to 9.3, natural conditions are not suitable for the development of fisheries, but the large silver fish can grow and breed freely in this lake. The transplantation of large silver fish in Daihai sea has important foundational significance, and the fishery development of other highly alkaline lakes in China has ushered in a new turning point.
After the case was reported, a wave of transplantation was set off nationwide, and the large silver fish spread to 21 different provinces across the country under the impetus of artificial introduction. As a typical cold-water fish, the large silver fish grows better in the north, and all provinces north of the Yangtze River in China have had transplant cases of large silver fish, and have achieved widespread success.
The appearance and general length of the large silverfish
Before the 1980s, domestic research on large silver fish was mainly focused on morphology, and the understanding was very limited. It was not until the 1980s that researchers began to study the basic biology of the large silver fish. Since 1995, the economic benefits of large silver fish transplantation have become the focus of domestic experts, and how to improve the success rate of transplantation and how to increase fishing yields have also become hot topics at that time.
In the past 30 years, the ecological safety problems brought about by the transplantation of large silver fish have gradually attracted people's attention. In many pristine lakes, the large silver fish poses a fatal threat to indigenous fish species due to rapid reproduction, ecological niche preemption, and egg ingestion, among which the more typical "victims" include the big head fish of Bosten Lake and the large white fish of Xingkai Lake. There are many more tragedies like this, and the big silver fish has also been on the "blacklist" of invasive species because of such "bad deeds".
Xingkai Lake large white fish / Xingkai lake bass
Up to now, a total of 17 species of silverfish have been found in the world, and there are 15 species in China, many of which have important economic value, such as the alligatory silverfish in the Taihu Lake Basin, which is the highest local production and the most famous high-grade "lake fresh". In Dongting Lake, Chao Lake, Poyang Lake and Chao Lake, silver fish has also been an important fishing object and is of great value. In the 1980s and 1990s, fishermen could earn a considerable income just by catching silver fish, and silver fish even surpassed the four major fish at one point.
Among the large families of silverfish, the large silverfish is the largest. The largest reported large silver fish was found in the Sanlizhuang Reservoir in Shandong Province, with a total length of 32 centimeters and a weight of 50 grams. Nearby villagers reported that the silver fish caught in the Sanlizhuang Reservoir are generally very large, which is estimated to have a lot to do with the abundant biological bait in the reservoir.
Great silverfish (scientific name: Protosalanx hyalocranius)
However, large silver fish with a body length of more than 30 cm are very rare, and the vast majority of individuals are around 8 to 10 cm. Compared to other freshwater fish, the large silverfish is not particularly large, but this species has an advantage that other fish do not have - the survival strategy of winter breeding.
The large silverfish population in the north begins to breed in mid-to-late December and begins to reach its peak in January of the following year. The broodstock die after breeding, and this once-in-a-lifetime characteristic is very similar to salmon salmon in salmon (by the way, salmon and salmon have very similar reproductive habits, but the former can reproduce multiple times).
After the eggs of the large silverfish are fertilized, the egg membrane will absorb water and expand, attaching to the matrix and slowly hatching. Due to the low water temperature in winter, the metabolism of other fish will be greatly weakened, and the feeding activity will also be significantly reduced, so the chance of predatory offspring of large silver fish is often very low.
Fresh large silver fish
By the following spring, the water temperature in the north gradually rises, and other fish begin to enter the breeding season, by which time the large silver fish has successfully hatched into juvenile fish. In the juvenile stage, the large silverfish feed on zooplankton in the water, and when it grows to a certain body length (6-8 cm), the feeding habits of the large silverfish will change significantly, and it will begin to feed mainly on fish and shrimp. Of course, the eggs of other fish are also on the prey list of large silverfish.
In terms of feeding habits, the large silver fish is enough to be described as "greedy", and in the absence of food, it will also show obvious cannibalism - researchers have repeatedly found the corpses of the same kind in the stomach of the big silver fish. In the Taihu Lake Basin, large silverfish will also prey on other small silverfish, such as oligodental shortsnout silverfish, Ray's silverfish, etc., and even kill wheat ear fish, small crucian carp and anchovies.
Big silver fish and other small trash fish in Taihu Lake
Judging from these ecological habits, the large silverfish does have the ferocious traits and potential risk of becoming an invasive species. However, even such a "fierce character" has fatal shortcomings. Large silverfish are annual fish, stocks fluctuate greatly, in natural circumstances, if only commercial fishing is carried out without the release of fertilized eggs, then the wild population of large silver fish is likely to decline due to insufficient reserve population.
In this regard, you may wish to first take a look at the transplant case of large silver fish in Xingkai Lake.
Xingkai Lake produces a very famous freshwater fish, the Xingkai Lake Fish, which is one of the four famous fish in China. In the 1980s, the Xingkai lake carp accounted for more than 80% of the total local fishery production, and it is the absolute dominant species in the lake.
Xingkai Lake and Small Xingkai Lake
However, after the introduction of large silver fish into Xingkai Lake, the production of Xingkai Lake bass began to decline continuously, and the foreign large silver fish was "anti-customer-oriented" and gradually became the main fishing object in the lake. According to a 2010 survey, the catch of large silver fish has reached 37%, while the proportion of Xingkai lake carp in the catch has dropped to 7%.
In order to control the production of silverfish, in recent years, Xingkai Lake has no longer stocked fertilized eggs of large silver fish, and all the harvesting production only relies on natural reproduction. Under the enormous pressure of commercial fishing, the stock resources of the large silver fish in Xingkai Lake have been in a state of decline, and the significant reduction of indigenous fish stocks has not occurred again.
Silver fish are abundant
In fact, although the reproductive ability of large silver fish is very strong, the fertilized eggs are easily affected by the physical environment such as water temperature and water flow during the incubation process, and there is even a risk of extinction in extreme environments. For example, the transplantation of large silver fish in the Daihai Sea of Inner Mongolia, although the transplantation experiment was successful, but in the 10th year of transplantation, the large silver fish in the lake suddenly disappeared, and this dramatic contrast was directly related to the hydrological environment of that year.
In most reservoirs where large silverfish are transplanted, annual introduction (stocking of fertilized eggs) is required to maintain production, and perennial transplantation does not necessarily achieve a 100% success rate. Some reservoirs have been transplanting fertilized eggs for many years without success, and as for the specific reasons behind them, many experts are also puzzled.
Whitebait
In short, it is not easy for large silver fish to "stand firm" and reproduce stably, which has a lot to do with environmental factors such as water quality, water temperature, and wind power. Although large silver fish are not prone to flooding and populations are relatively easy to control, many practitioners tend to pursue economic benefits one-sidedly while ignoring the protection of indigenous fish when it comes to fishery production.
It is undeniable that the transplantation of large silver fish is indeed a cost-effective "project" to increase economic income, but the transplantation process should also pay attention to the "ecological bottom line" problem - for example, in some special fish nature reserves, the transplantation of large silver fish may trigger a species extinction crisis. In addition, in the natural water bodies where endangered species and vulnerable indigenous fish species live, it is best not to transplant large silver fish, otherwise it may lead to irreparable ecological losses.
Objectively speaking, the large water surface that is currently most suitable for transplanting large silver fish should be a closed reservoir and no undeveloped "virgin lake". In Xinjiang, Qinghai and Tibet, there are many lakes with relatively high salinity, the water quality of the lake is not suitable for the survival of other fish, in such a nutrient-poor "virgin lake", the transplantation of large silver fish can play a positive effect, and the ecological risk is also minimized.
What do you think about the transplantation of large silverfish? Feel free to leave a message in the comments section to discuss!
#谣零零计划 #