Qiandao Lake, also known as Xin'anjiang Reservoir, is located in Chun'an County, Hangzhou City, Zhejiang Province, and connects a small part of the northwest of Jiande City, Hangzhou City.
The Qiandao Lake Reservoir Dam is 105 meters high and 462 meters long; The reservoir is about 150 kilometers long, and the widest point is more than 10 kilometers; The deepest depth is more than 100 meters, the average water depth is 30.44 meters, and under normal water level, the area is about 580 square kilometers, and the water storage can reach 17.8 billion cubic meters.
According to statistics, there are 114 species of fish in Qiandao Lake, including 9 species of exotic fish, among these 9 species of fish, there is a giant predatory fish, which is known as the "vicious dog in the water" pike, so in the face of the invasion of pike, the native fish of Qiandao Lake can hold their position?
1. Dogfish
Dogfish is a freshwater fish of the genus Pike of the salmoniformes family Pike, and the species of pike in the world include striped pike, white pike, North American pike, dark pike, black pike, reticulated pike, and insect pike.
There are two kinds of pike on the mainland, namely the pike, which is found in the alpine rivers of Asia, Europe and North America, and the main stream of the Irtysh River and its tributaries in China.
The distribution of pike is mainly distributed in Heilongjiang, Ussuri River, Nenjiang River, Songhua River, Suifen River and other water systems, lakes and reservoirs, and is also found in Jingpo Lake and Wudalianchi.
It is not difficult to see from the distribution of pike and pike that they mainly survive in the north and belong to cold-water fish, but it is not afraid of heat, and the water temperature range is 0~30 °C, and it can still survive in the case of 35 °C water temperature, and the best feeding temperature is 16~26 °C.
This adaptability of the pike allows it to have almost the ability to be distributed throughout the country, and the pike that appears in Qiandao Lake is the white pike. Pike is a giant fish with adult males up to 100 cm in length, females up to 150 cm long, and some large individuals can weigh up to 35 kg in natural water bodies.
But this is not the largest record of the pike, through the query it is known that in Russia waters, due to the relatively small catch, the giant pike body length is more than 1.5 meters, the weight is more than 50 kilograms, a proper giant freshwater fish.
It is not clear how the pike entered the Qiandao Lake, and there is no information, but it may be that the cage culture escaped, because in the 90s of the last century, the cage culture in the Qiandao Lake was rampant, and many foreign fish were cultivated.
For example, tilapia, sunfish, spotted catfish, etc., these fish have now settled in Qiandao Lake, all of which are invasive fish, and pike should have entered the Qiandao Lake reservoir area during this time, thus surviving.
The 2-3 years old of pike are sexually mature, and they begin to reproduce in April every year, and the breeding period is short, lasting about 1 month; The number of eggs is 20,000-70,000 per kilogram of body weight, and the incubation period is about 8-15 days, and it takes 21 days from hatching to fin formation.
2. The hazards of pike
Biological invasion refers to the phenomenon that a certain organism is naturally introduced from other places or artificially introduced into the wild state and causes certain harm to the local ecosystem. It is mainly the feeding habits of dogfish.
The pike is a giant predatory fish that is resistant to low temperatures, can survive in cold water at high latitudes, and can also grow in deep water at low temperatures, and is highly adaptable and aggressive.
Newly hatched pike larvae are docile and often live in groups, feeding mainly on plankton such as rotifers, small cladopods and copepods. When the body grows to 5-7 cm, it preys on other fish, and the adult fish inhabits alone.
Pike has the characteristics of phased cannibalism, more than 8 cm, mutual defense ability is enhanced, and the phenomenon of cannibalism is gradually alleviated, and after 15 cm, the phenomenon of cannibalism is basically controlled, but when the bait fish is lacking in the adult stage, it will still appear.
Even after adulthood, they kill each other when there is not enough bait, and adults can devour small pike fish that make up 10-20% of their body weight. The main food of adult fish is other fish, such as frogs, voles, water birds, wild ducks, etc.
Due to its low temperature tolerance, pike do not stop eating in winter, and the peak eating period is April every year, which is the breeding season of pike, and the pike during the breeding period are very greedy. When the female fish spawns, the male fish do not dare to approach at will, because the body size of the male fish is relatively small compared to the female fish, and there is a risk of being swallowed, which shows the ferocity of the pike.
In the lower reaches of the Irtysh River, in the Ob River, anglers catch pike with everything in their stomachs, and snakes and waterfowl are common, as snakes and waterfowl are relatively easy to catch.
The pike eats a very large amount of food, and when the food is sufficient, it can eat almost the same food as its own weight every day, and in the waters where it lives, the pike is the apex predator and has no natural predators.
But now in the Irtysh River Basin, Bosten Lake Basin and so on in Xinjiang, because the catch is too large, the reproduction and growth rate cannot keep up with the fishing speed, plus this fish is a high-grade edible fish, its natural resources have been very limited. White spot was included in the list of national key protected economic aquatic animal and plant resources (the first batch) in mainland China
There are two main harms of pike, one is that it is not a native fish in Qiandao Lake, and after it enters Qiandao Lake, it will have an impact on local fish; The second is that there are no natural enemies, and the lack of natural enemies allows them to reproduce and grow in disorder.
3. Can native fish hold their ground?
So in the face of the invasion of pike, can the native fish hold their ground? I think "yes" for the simple reason that the pike is not without its shortcomings, and its shortcomings are fatal.
Disadvantage 1: Pike do not have the behavior of egg protection, and fish want to increase the population quickly, either because of the fast reproduction rate or the high survival rate. Fast reproduction rate means that the spawning volume is large, such as: crucian carp, sunfish, etc., which can quickly increase the population in a short time.
A high survival rate means a low mortality rate of hatched juveniles, such as tilapia and blackfish. After tilapia spawns, it swallows the eggs into the mouth, hatches them in the mouth, and takes the young fish to grow for a period of time after hatching, and the young fish can survive independently before the adults leave.
After the blackfish spawns, the husband and wife jointly guard the hatching of the cubs, and the hatched cubs will only leave after the hatching cubs are accompanied by the parents of the blackfish and have the ability to survive independently.
Not only does the pike not protect the eggs, but the female pike after spawning will also swallow some of the eggs due to hunger, how can you reproduce quickly? And the eggs of the pike hatch too slowly! At a water temperature of 5-11 °C, the zygotes hatch after about 185 hours of development.
185 hours, almost 8 days, that's a long time! The eggs are not guarded by the adults, and if they are underwater for so long, they will definitely be found by other fish, and other fish will definitely swallow the eggs of dogfish in large quantities.
Therefore, the slow reproduction rate is the disadvantage of the dogfish, although the dogfish has a huge body when it is an adult, and sharp teeth, and a ferocious nature, but it is destined to be difficult to dominate in the waters!
Disadvantage 2: It is too ferocious, and the hatched pike juveniles are active in groups, and the adults are scattered to feed, move quickly and agilely, and often move in aquatic grasses.
After hatching, the juveniles of the pike have a process of survival of the fittest, and some juveniles with poor mobility, or emaciated juveniles, or injured juveniles, are food for other juveniles.
Not only that, when the juveniles grow to about 5 cm, the eating habits change greatly, feeding on other fish and shrimp, and cannibalism is more serious when the food is insufficient, because although it is the same batch of hatched juveniles, the individual size difference is huge, and the survival rate of small individual black fish cubs is extremely low, and it is easy to be swallowed by the same kind.
This process continues until the body is about 8 cm long, but stopping does not mean that there will be no cannibalism, if there is not enough food, it will still kill each other again. The body length is more than 8 cm, the mutual defense ability is enhanced, and the phenomenon of cannibalism is gradually alleviated, and after 15 cm, the phenomenon of cannibalism is basically controlled, but it still appears when there is a lack of forage fish in the adult stage.
That is to say, when the pike is an adult, if there is not enough food, it will still kill each other, and this way of survival of the pike, although the survival of the fittest, is too cruel, causing its population to grow slowly, even in the absence of natural predators, their population increases relatively slowly.
Because the sexual maturity of pike is relatively late, the initial sexual maturity age of pike is 2-3 years, the male is 2 years old, and the female is 3 years old, and the initial sexual maturity of the individual weight is concentrated in about 1 kg.
It takes 2-3 years to reach sexual maturity and begin to spawn, and the maturity time is relatively long, although the amount of spawning is not a lot, but the loss of fish eggs is too large, and the survival rate of juvenile fish is relatively low, which makes it difficult for pike to dominate in Qiandao Lake.
Through these two aspects, do you think native fish can hold their ground? I don't think it's a problem, because the ferocity of the dogfish "made itself dead". The reason is simple, after the pike spawns, many native fish will definitely swallow the eggs, because there is no adult fish to protect it, even the crucian carp can swallow its eggs.
In addition, the mortality rate of pike is too great during the growth process, and the juveniles begin to kill each other, and when there is a lack of food after the adult fish, they will still devour each other, causing their population to grow very slowly.
The only thing to worry about is that there are many fish in Qiandao Lake, not only large fish, but also small fish, these fish are the "dog food" that pike ask for at will, if the food is sufficient, then the situation of pike cannibalism will be greatly reduced, and the reproduction rate and survival rate will be accelerated.
Finally, the mainland stipulates that the standard for invasive fish is that all native fish that are not locally owned are invasive fish. Although the pike is a mainland fish, it is not a native fish in the waters of Qiandao Lake, so it is also an invasive fish.
If the pike is not so ferocious, has the behavior of protecting the eggs after spawning, and after the eggs hatch, they protect the young, and leave after the young fish can forage on their own, then I think the pike can not only dominate the waters of Qiandao Lake, but also in many waters in the north, the population of pike will not be less. So with a situation where there is plenty of food in Qiandao Lake, do you think pike can reproduce quickly and thus increase their populations quickly?
#长文创作激励计划#