preface
The Chinese giant salamander is a rare amphibian with tail, and because its call resembles the cry of a child, it is also known as the "baby fish".
Giant salamander is a national second-class protected aquatic organism, and is a key cultivated variety of mainland agricultural industrialization and characteristic agriculture. It is a genetically protected wild animal.
Originating 160 million years ago, the Chinese giant salamander is the largest amphibian ever discovered, and it is also a species of great medicinal value.
Due to the complex life history of Chinese giant salamander, high dependence on water environment, and poor migration, its population is very sensitive to habitat changes.
In the past few decades, due to the continuous destruction of the natural environment and the overhunting of wild individuals, the distribution area of the Chinese giant salamander has shrunk sharply, and its population has also declined sharply.
In China, the giant salamander is a widely distributed species, found in rivers and rivers in the middle and upper reaches of the Yangtze, Yellow and Pearl Rivers. The giant salamander is fished extensively due to its high edible and medicinal value, resulting in a decline in its wild population on the mainland.
In addition, due to environmental pollution caused by human activities, its habitat has been severely damaged, resulting in a continuous decline in its population.
In order to better protect the resources of giant salamanders and better meet the needs of the market for giant salamanders, the artificial breeding of giant salamanders has become a research hotspot in recent years.
First, the appearance of the Chinese giant salamander
The body of the Chinese giant salamander is a smooth ovate shape, its belly is white, and the rest is gray and brown to black; Its body consists of the head, torso, tail, and limbs.
The head is large and flat, with obvious sarcoma granules on the surface, very small eyes and nose, and round and blunt at the end of the snout; The trunk is flat, there are broad streaks on the sides of the body, the body surface is moist and smooth, the glands are dense, and the body color varies according to the habitat.
The limbs are short and stout, the forelimbs and hindlimbs are amphibians, the forelimbs have only four fingers, no claws, and the hindlimbs have five toes, each with a thin membrane connection between them.
There is a big difference in body length and weight between adult salamanders and juvenile giant salamanders, the maximum individual length can reach 1.8 meters, and the maximum individual weight can reach 50 kg.
Second, the reproduction and feeding behavior of the Chinese giant salamander
1. Mating
The reproductive cycle of Chinese giant salamanders is 5-8 months, and its reproductive mode is mainly internal pollination. During the breeding period, the male salamander keeps circling the female salamander, and touches the cloaca of the female salamander with the end of his mouth to send a courtship signal to the female salamander;
When stimulated by the male, the female follows and wraps the semen excreted by the male with her own cloaca, so that the egg and sperm combine to produce a fertilized egg.
2. Juvenile salamander feeding
The Chinese giant salamander is invertebrate as its main food source in juvenile years.
During the development of Chinese giant salamanders, their food structure and digestive ability have also changed greatly: the food structure of small giant salamanders has changed from easily digestible earthworms to large clades;
As the larvae age, their feeding on large silkworms gradually increases. When it grows to 50 grams, it can feed on small loaches, small fish and shrimp. Those trained wild boars feed on grain.
3. Adult salamander feeding
Adults of Chinese giant salamanders feed mainly on nematodes, crabs, insects, fish, frogs, etc., and sometimes juvenile giant salamanders.
The species of food of giant salamanders vary with the food species structure of the region, and have obvious seasonality: frogs and fish are the main ones in summer, nematodes are the main ones in autumn and winter, and in severe winter, the river water temperature decreases, and the feeding species of giant salamanders are significantly reduced.
The results showed that the feeding habit of Chinese giant salamander had a strong correlation with the seasonal changes of its habitat.
3. Distribution of giant salamanders, wild resources and conservation
1. Geographical location
The Chinese giant salamander is distributed in the middle and upper reaches of the Yangtze River, the Yellow River, the Pearl River Basin, and 18 provinces in Hebei, Henan, Shaanxi, Shanxi, Qinghai, Gansu, Sichuan, Chongqing, Guizhou, Hubei, Hunan, Jiangxi, Anhui, Jiangsu, Zhejiang, Fujian, Guangdong, and Guangxi Zhuang Autonomous Region.
It is distributed in 18 provinces in central, southern, southern, southern, and southwestern China.
In addition, some scholars believe that plants of this genus also have a certain distribution in Yunnan. In China, Hunan, Hubei, Shaanxi and Henan are the main ones.
2. Wild germplasm
In the 70s and 80s of the twentieth century, Chinese giant salamanders distributed a large number of wild resources in Shaanxi, Hunan and Anhui, distributed in most mountainous areas, streams and rivers.
However, since the 80s of the last century, due to severe habitat damage, the population of this species has plummeted, and in some areas it is only sporadic and mostly found in underground dark rivers under karst landforms, and many areas have become extinct.
Studies in recent years have shown that there are five species of Chinese giant salamanders, including Shaanxi, Sichuan, Guangxi, Guizhou and Anhui, and have a good relationship with the geographical distribution of mainland rivers.
In addition, studies have shown that there are two different evolutionary branches in the captive-bred giant salamander population in the mainland, and combined with the group in the Qinghai-Tibet Plateau, there are 8 species in China, but this inference needs to be confirmed by more studies.
3. Protection
Affected by ecological environment damage and overfishing, the global distribution area of the Chinese giant salamander has gradually shrunk, the population has decreased year by year, and some species have become endangered.
Therefore, it is necessary to reasonably protect it, and develop and utilize it reasonably.
(1) Strengthen the ecological and environmental protection of China's giant salamander industry, correctly handle the contradiction between capital construction and the protection of wild species, and advocate and establish the awareness of the whole people on the protection of wild species.
(2) Seek suitable habitats, scientifically zoning and planning them, and scientifically plan and construct them.
(3) Strengthen fishery administrative law enforcement and create a good ecological environment.
(4) Appropriate artificial release according to the origin and population distribution of giant salamanders.
(5) Set up artificial breeding sites in the distribution area of giant salamanders, or select waters suitable for their life, and set up relevant scientific research and protection units.
Fourth, the design of breeding ponds
Mainland wild salamanders are mainly distributed in mountain streams 300-800 meters in the middle and upper reaches of the Yangtze River, Yellow River and Pearl River, because the giant salamander has the characteristics of joy and fear, fear of cleanliness and pollution, and love of shade and wind.
Therefore, when raising giant salamanders, the selection of their breeding ponds fully considers their characteristics, with natural caves or mountain streams as the best, and if there are no natural caves or mountain streams in the local area, caves can be dug on the cliffs where the stream flows to raise them.
The advantage of this farming method is that it can make the breeding environment of giant salamanders closer to the living environment of wild giant salamanders, and can better reflect the growth characteristics of giant salamanders.
1. Determine the breeding location
First of all, attention should be paid to the water supply of giant salamander breeding bases, not only to ensure sufficient water supply, but also to meet the water quality requirements for aquaculture.
You can choose groundwater, mountain streams, reservoir water, etc., the water quality is clear, the water temperature is suitable, and it is an ideal water source for breeding giant salamanders.
Secondly, pay attention to the environment around the pond, preferably a place that is inaccessible and densely wooded, such a place has fresh air, low temperature, and is relatively quiet, which is very suitable for the growth of giant salamanders. In addition, it is necessary to consider the problem of transportation, eating or not.
2. Design and construction of cultivation ponds
In the design and construction of giant salamander culture ponds, it is necessary to carry out according to its different growth periods, and the area of the pond should be determined according to the specifications of giant salamanders.
Among them, the juvenile pond is about 0.5-1 square meters, the juvenile fish pond is about 1-2 square meters, and the adult fish pond is about 2-4 square meters.
The giant salamander breeding pond in each period should be oval or rectangular, with 2-3 times the length of the cultured salamander as the height of the salamander breeding pond to ensure the bottom and surrounding of the giant salamander breeding pond to be flat, and set up a square escape net at the top of the giant salamander breeding pond to avoid the giant salamander escaping from the breeding pond.
In addition, in the pond where the salamander is kept, more holes should be dug in order to provide them with a place to hide and hide.
It should be ensured that each salamander pond has a separate drainage facility, so that the water level of the fish pond can be effectively controlled, and the sewage treatment of the fish pond can be facilitated.
5. Breeding density
There are many factors that influence the feeding density of giant salamanders. It mainly includes: the size of the giant salamander, the water source, bait, water quality of the breeding base, etc.
In the seedling stage of giant salamander, due to its low feed intake and small range of activity, its feeding density can be appropriately increased. However, for adult salamanders, due to their mutual aggression, and their range of activity is relatively large, and their predation ability is relatively strong.
Therefore, the stocking density of adult salamanders should be appropriately reduced. Generally, the feeding density of giant salamanders at the seedling stage is about 60~100 per square meter, and the feeding density of adult giant salamanders is about 5~20 per square meter.
In addition, when stocking giant salamanders, it is necessary to put the same size of salamanders together as much as possible, usually the difference between giant salamanders should be controlled within 0.5 times.
6. Feeding management
1. Feed feeding
Since salamanders like to eat the offal of fish, shrimp and other animals, you must pay attention to the freshness of the food when feeding.
Pay attention to feeding the salamander regularly, depending on its activity, preferably at night. In places where the giant salamander inhabits, it is necessary to place it around its nest as much as possible to reduce its mobility and facilitate its feeding.
When screening bait for giant salamanders, pay attention to the freshness of the bait to avoid changes in the type of bait and cause anorexia of giant salamanders.
The salamander eats a large amount, so when feeding it, it should be decided according to its specific situation, generally between 10% and 15% of the salamander's body weight. In addition, when feeding bait for giant salamanders, it is also necessary to comprehensively consider weather conditions, water temperature and other factors, and combine the individual characteristics of giant salamanders to determine the feeding amount of bait.
When the giant salamander eats, pay attention to maintaining a certain quiet, so as not to startle the salamander, otherwise, the startled salamander is likely to spit out what it swallows, thus affecting the eating effect.
2. Adjust the water temperature and adjust the light
In the breeding of giant salamanders, attention should be paid to the control of pond water temperature. Because the salamander is very sensitive to water temperature, if the water temperature is too high, it will make it go dormant;
If the temperature is too low, the salamander will go into hibernation. Therefore, in the summer, it is necessary to do a certain cooling work; Warm as necessary in winter.
Therefore, it ensures that the temperature of the giant salamander pond is suitable for the growth of the giant salamander, and provides a good growth environment for the giant salamander. At the same time, because the giant salamander also has the characteristics of fear of light, so when breeding the giant salamander, pay attention to the light protection of the farm, and can use the shading net to shield the farm to prevent the farm from direct sunlight.
When patrolling at night, be especially careful not to use strong light flashlights and other instruments to shine on the farm.
3. Ways to prevent escape and theft
Since the ecological breeding of giant salamanders is usually established in the wilderness, preventing theft and theft is a more difficult task.
Because the giant salamander is fast, and its speed, and it has a high height and weight, this increases its defense difficulty, and a careless one will be seized by it.
Therefore, when raising giant salamanders, it is necessary to always improve vigilance, and anti-escape devices should be set up in the breeding pond and even in the inlet, out, and land passages of the entire farm to prevent giant salamanders from escaping.
In addition, when raising giant salamanders, it is necessary to do a good job of anti-theft, because the economic value of giant salamanders is very high, and it is easy to be coveted by lawbreakers, so effective measures must be taken to ensure the safety of breeding and prevent theft by lawbreakers.
conclusion
Chinese giant salamander not only has high application value in biological evolution and genetic diversity, but also has high application value in medicine, so the protection, development and breeding of Chinese giant salamander have good development prospects.
The ecological protection of China's giant salamander industry should be strengthened, and further research should be carried out on the conservation and breeding technology of Chinese giant salamander, so as to maximize the biological, medicinal and economic value of Chinese giant salamander.
[References]:
[1] DUAN Yan, XIONG Bin, YAN Wenbo, et al. Biological research progress of giant salamander[J].Heilongjiang Agricultural Sciences,2018(2):144 148.)
[2] LI Cheng. Key matters of giant salamander seedling culture[J].Contemporary Fisheries,2013(8):83 84.)
[3] Luo Lintong, Wan Hongling, Lan Xiaoping, et al. Research progress on conservation genetics of giant salamander in China[J].Guangdong Agricultural Sciences,2011,38(17):100 103.)
[4] ZHANG Hongxing, WANG Kaifeng, QAN Qingzhuan, et al. Observation of reproductive ecology and behavior of giant salamander in China[J].Journal of Shaanxi Normal University,2006,34(s1):70 75.)