River crabs belong to the class Crustacea, suborder Decapoda, and genus Eriocheura.
In recent years, river crabs have become one of the main species for artificial breeding and culture.
With the increasing stocking density of river crab breeding and the destruction of the breeding environment, crab diseases have become increasingly serious, posing a greater threat to the river crab breeding industry and causing huge losses to farmers.
After collecting, sorting, and studying a large amount of data and cases, we have more than 500 front-line technicians across the country and concluded that to control crab disease outbreaks, we mainly focus on the reasonable breeding environment, seed procurement, and aquatic animal care. Starting from several aspects such as application, in a nutshell, it is Yumeikang's healthy and efficient breeding model of "repairing prevention with nourishment, strengthening health and eliminating evil".
Through this model, we can achieve high efficiency and high yield, reduce unnecessary economic losses of farmers and friends, and at the same time improve economic benefits.
The following is a summary of relevant experience in river crab disease prevention that the author has summarized while engaged in technical service work for crab breeding for several years. I hope it can be helpful to the majority of farmers.
Enteritis
Symptoms: The overall food intake at the entrance of the pond has decreased, some crabs have jejunum, and the crabs dumped from cages on the ground have poor vitality, slow movement, and difficulty in turning over. Some sick crabs will vomit yellow foam at the mouth. .
Open the shell and check the intestines. The inner intestine and jejunum are inflamed, red and without feces. When squeezed by hand, there will be turbid liquid, which will be accompanied by edema and liver problems.
Cause: Enteritis is usually caused by poor water quality and partially rotten aquatic plants, mainly bacterial infections caused by animal feed (chilled fish) or moldy feed. At the same time, it may also be caused by external input. Germs.
The main pathogenic bacteria are Aeromonas hydrophila, Salmonella, and Escherichia coli, which are extremely contagious.
Suggested solution: Step 1: Remove the sick and dead crabs in time, pass through external water or groundwater, and then proceed to the next step.
The second step: Sprinkle special iodine in the whole pool, and take Meikang 2 6 Water Gold and Combining orally at the same time.
The third step: Dikang No. 1 and Dikang No. 3 are used to nourish water and detoxify.
Step 4: Spray the entire pool with special aldehyde for disinfection.
Gill rot
Symptoms: The gills of diseased crabs are infected and discolored, and the gill filaments appear yellowish or black, with inflammation and local ulceration. The diseased crabs have decreased vitality, slow movement and difficulty breathing. Difficulty, reduced food intake, and death in severe cases. This disease mostly occurs in the middle and late stages of river crab farming.
Cause: Gills are the respiratory and excretory organs of river crabs and maintain the metabolism of the entire body.
Under normal circumstances, if the gill function of river crabs is damaged, the liver will also atrophy, severe liver necrosis, and death will occur if you are not careful.
Gill rot is mainly caused by bacteria, mainly Vibrio, Aeromonas, and Edwardsiella. Deterioration of water quality, harmful bacteria in the substrate, and long-term feeding of spoiled or moldy bait can induce gill rot. main factors.
Suggested plan: Change the bottom of Dikang No. 1 to Dikang No. 3, splash the whole pool with special iodine for disinfection, take Meikang No. 2 and Meikang No. 6 Water Golden Combinine orally, and use special iodine again three days later .
Attachments on the body surface of crabs
Symptoms: There are attachments on the surface of the crab body, which are slippery to the touch and look a little black. The crab eats less and is active in catching grass. At the same time, I would go to the shore and get out of the water at noon, holding my paws up.
There are also parts that are colored like moss or a layer of mud.
Hazards: The vitality of river crabs attached to ciliates will gradually weaken, causing the crabs to lack nutrition, decline in physical fitness, slow growth, and easily die in the pond. The body surface is dirty, the appearance is poor, and they cannot sell well. It will cause damage to the gills, difficulty breathing in river crabs, secondary bacterial infection, and massive death of river crabs.
Cause: Crab ciliate disease is a parasitic disease that often occurs in river crabs in autumn. The pathogen is caused by ciliate parasites such as branchworms, bellworms, and polyconstrictors that parasitize on the surface of crabs. , appendages, gills and other parts.
For those who often feed chilled fish, residual bait and feces will accumulate on the bottom of the pond, resulting in poor and dirty bottom quality. There will be too much rotten grass and residual bait and feces, and they will not pay attention to bottom modification and water transfer, resulting in water quality and bottom pollution. Provides favorable conditions for ciliates to reproduce.
Suggested solution:
Dikang No. 1 improves the substrate, uses Bacillus to decompose organic matter in the water body, and uses Jiangsu No. 2 to treat ciliates on crabs.
Water crab disease
Since 2015, "Water crab disease" has become one of the major diseases in river crab farming. Its incidence and spread have basically swept through the major breeding areas across the country. , causing huge economic losses to river crab farmers.
There are also different opinions on the root cause of water flatulence disease. At present, experts in the industry have not come to a conclusion. There are all kinds of theories. Some say it is caused by viruses, and some people say that water flatulence disease is caused by viruses. It is caused by Vibrio or Aeromonas hydrophila, and some people say it is caused by microsporidian infection. There are various theories.
I personally think that there are many reasons for water deficiency.
Symptoms:
Very low energy, not eating much, not molting, or having difficulty molting, hepatopancreas white and eroded, it is difficult to distinguish liver filaments, open There will be a lot of body fluids in the shell, the surface of the gills is intact, the muscles are atrophied, there is a lot of tissue fluid in the appendages, the shell is very thin, the exoskeleton is very soft when pinched by hand, the intestines are basically devoid of food or may be yellow, that is, the hepatopancreas Expelled.
These are very typical symptoms.
↓↓The factors that may induce this disease are as follows↓↓
Seed problems: Due to the impact of the epidemic this year, management of crabs after overwintering has been neglected, and nutrition cannot keep up. At the same time, the demand for seedlings is much greater in February. Many people use drugs to drive the seedlings, such as polyester, and the harm to the seedlings can be imagined.
Aquatic weed problem: The density of aquatic weed is too thick and the distribution is uneven, which will affect the flow of the water body and cause the water body to be stratified. There will be sufficient dissolved oxygen in the upper layer and insufficient dissolved oxygen in the bottom layer, affecting crab feeding. Increased pH value will also affect crabs. All are big.
The weather has changed abnormally this year: the temperature has slowly risen at the beginning of the year, but the epidemic has caught up with it, and it is impossible to go out to feed the crab seedlings. When the epidemic is over, the crabs will be removed from the pond and fed in large quantities. Animal bait will be used in the early stage Excessive use will affect the digestive system of crabs. The bait cannot be digested well and will be excreted from the body. This will cause the crabs to seem to eat a lot. In fact, the nutrition of the crabs is not enough, and it also increases water pollution.
In June, there was abundant rain, and the continuous rainy days were extremely abnormal. These aspects also had a great impact on the occurrence of water chest disease.
Harmful bacteria problem: Bacteria in normal ponds include beneficial bacteria and harmful bacteria.
We are now carrying out high-density breeding, which has high requirements on the overall environment, especially bacterial species. Commonly encountered in crab ponds are Vibrio, Aeromonas, Aeromonas hydrophila, Escherichia coli, Salmonella, etc. These are relatively harmful bacteria. We should carry out regular sterilization and disinfection, and then regularly replenish beneficial bacteria so that the number of beneficial bacteria in the pond is higher than harmful bacteria to achieve the goal of antibacterial bacteria. Effect! Generally, liver necrosis will be accompanied by edema, enteritis and other symptoms during examination!
Feed nutrition issues: The first thing is the feed. There should be no moldy feed, especially animal feed, and no spoiled feed. Using these feeds for feeding is equivalent to poisoning! Furthermore, through a large number of practical case studies in Tangkou, the author found that the probability of developing water gallbladder in Tangkou who takes it regularly orally is very low. At the same time, the probability of curing water gallbladder in Tangkou who takes it regularly is about 80%.
Oral administration combination package: Meikang No. 1 Meikang No. 2 Meikang No. 6 Water Gold
Meikang No. 1 mainly uses lactic acid bacteria to improve intestinal digestion and absorption; Meikang 2 No. 6 mainly plays a great role in the repair of crab liver; Meikang No. 6 is mainly a coated vitamin that participates in the metabolism of the entire body and helps to restore the crab's physical condition; Water Gold, the main component is a patented fig polysaccharide product, which can improve crab resistance Bacteria, anti-viral ability, improve immunity, increase crab resistance! !
Dissolved oxygen problem: This year’s continuous rainy days, low air pressure and heavy rain will lead to hypoxia in water bodies.
In July, the temperature has not yet risen and the water temperature is low, which will also lead to poor food intake and low immune function of crabs.
If there are too many aquatic plants and they are too thick, the water body cannot circulate, and hypoxia will also occur.
Continuous rainy days must prevent aquatic plants from rotting. Continuous rainy days can also cause muddy water, bottom heat, return to the bottom, and lack of oxygen in the bottom layer.
It is very important to use Dikang No. 1 and Dikang No. 3 regularly to reduce bottom heat and reduce oxygen debt, a factor of dissolved oxygen.
Drug residue problem: Regarding this factor, we must first start with the seedlings. There are many crab owners who want to grow a large number of seedlings in a short period of time. They usually use drugs to drive the seedlings. , such as: polyester, will slightly poison the seedlings, which is very common in the breeding process and is a very important factor.
Also during the breeding process of adult crabs, if there are lobsters in the pond, special drugs will usually be used to drive away the lobsters. If they have stimulating and killing effects on the lobsters, they will also be the same for crabs, and they will reappear. Mild poisoning.
There is also the problem of insecticide. We choose some irregular small-manufacturer drugs and blindly pursue the effect. The drug residue is quite heavy. The crabs are also slightly poisoned. Generally, the food is worse and the activity is worse. , and then the water becomes very transparent, etc. There are many such phenomena. These are very important factors, but we usually ignore them.
Shivering Disease
Symptoms: In the early stages of Shivering Disease in river crabs, sick crabs eat less or no food, have difficulty in shedding their shells, and have weakened mobility.
Sick crabs have symptoms such as constant trembling, twitching and spasming of their appendages. The appendages are weak and often tremble every time they are touched.
Sometimes the legs tuck together and curl up into a ball, so some places call it ring-leg disease or trembling disease.
_Sometimes they are light rusty or slightly black in color. They often lie quietly on the shore or next to aquatic plants without taking in food.
Pathogen: The etiology of this disease has not yet been determined. Mainstream reports include viruses and spiroplasmas. Among viral pathogens, Chinese mitten crab reovirus is more commonly reported.
Predisposing factors: The dissolved oxygen at the bottom of the pond has been low for a long time, especially in high temperature weather, when the dissolved oxygen at the bottom is low, and the incidence of shivering disease is serious.
A large number of aquatic plants are rotting, and river crabs will become sick in large numbers after they float and crawl around due to severe lack of oxygen.
Ponds that usually use irritating drugs to treat problems, such as killing insects or cyanobacteria (or moss), have a higher incidence rate.
Ponds with large amounts of feeding and endless food are also prone to disease.
In areas where ponds are not completely cleared or cannot be cleared in the early stage of breeding, the incidence rate is generally higher.
Preventive measures: Preventing "tremor disease" should start with eliminating the source of the disease.
1. Clean the pond: dredge the pond mouth and disinfect it with quicklime or bleaching powder at the dosage of 500 kilograms and 80 kilograms per mu respectively.
After disinfection, drain the water and dry the pond for 2 to 3 months.
2. The selection of crab fry, Yumeikang crab fry, has guaranteed quality and traceability.
3. For aquatic plant management, 30% of the entire pond is enough, not too much. High pH is also one of the inducing factors.
4. Strengthen the control of water quality and substrate, and carry out substrate improvement regularly. Dikang No. 1 once a week, Yangshuibao once a week, Junmei No. 2 and EM mother bacteria once a week.
5. The feed should be fed with reasonable nutrition and should not be moldy or spoiled. Especially animal feed should not be fed too much.
6. Comprehensive management starts from the aspects of physiology, intestines, and liver and gallbladder.
In terms of ecology, attention should be paid to controlling the overall water environment substrate; in terms of production, attention should be paid to scientific pond management in terms of reasonable aquatic plant layout and reasonable feeding methods.
Crab slave disease
Brief description: Diseased crabs grow slowly, have underdeveloped gonads, and it is difficult to distinguish between male and female.
When crab slaves are seriously parasitized, river crab meat becomes smelly and inedible, commonly known as "bed bug crabs".
The disease is most likely to occur in brackish water ponds with high salt content.
Symptoms: The abdomen of the sick crab is slightly bloated. When the umbilical cover is opened, 2-5 mm of milky white or translucent granular worms about 1 mm thick can be seen parasitic on the appendages or breast plates. The growth of the sick crab is slow. River crabs that are seriously parasitized by crab slaves have foul-smelling meat and cannot be eaten. The main reason for the disease is that the pool water has high salt content, crab slaves breed in large numbers, and the larvae spread and become infected.
The onset season is from June to September, especially August is more common.
Cause: The crab parasite lives on the abdomen of the crab. The parasite body is divided into two parts: the crab slave's outer body and the crab's slave's endosome. The former protrudes outside the host, including the handle and incubation sac, which is commonly seen. the interumbilical particles; the latter are branch-like thin tubes that parasitize outside the body of the crab, extend into the host body, and spread to the muscles, nervous system, internal organs and other tissues of the crab body and appendages, forming white tubes with a diameter of about 1 mm. Linear branches used to absorb nutrients from the crab body.
(Excerpted from Baidu)
Defensive measures: Clean the pond thoroughly to kill crab slaves.
Starting from the selection of seedlings, strict screening is carried out, the bottom is changed regularly, the eggs are oxidized, and the eggs are regularly observed in ground cages and disinfected regularly.
Self-cut regeneration
Crabs have strong self-repair and protection capabilities.
When subjected to strong stimulation, hypoxia, poisoning, mechanical damage or failure to molt, insufficient food intake and excessive stocking density will also occur.
There is also the phenomenon of escaping with broken claws. For example, when a human suddenly catches a crab, if it only catches 1-2 legs, it will quickly detach its attached legs and run away. And new feet have grown.
Especially when fishing in large numbers, we sometimes see large differences in the size of crabs' claws, which is the result of self-cutting and regeneration.
Crabs regenerate themselves after cutting themselves. The severed limbs of crabs have fixed parts, which are always between the base and seat segments of the appendage. The structure here is special, which can prevent bleeding and regrow new legs. Come.
The phenomenon of self-cut regeneration of crabs only exists before the third shell of young crabs in the growth and molting stage. Crabs after sexual maturity do not have the function of regeneration.
When you find that there are many such situations, take Meikang No. 1, Meikang No. 2, Meikang No. 6 Water Gold Growth Promoting Hard Shell Treasure orally to supplement nutrients and trace elements.
Black and yellow bottoms
Factors for the formation: There are two factors. Crabs are benthic animals. The quality of water and bottom determines the quality of crabs: 1. Bottom Causes, such as sulfur, iron, ammonia and other elements.
2. In the later stage of river crab breeding caused by poor management in the later stage, due to the increase in feeding amount, a large amount of residual bait and feces were not decomposed in time. In addition, aquatic plants rotted and a large number of algae died and sank to the bottom of the pond, forming a large number of Organic matter and organic debris ferment and decay with the participation of bacteria, causing the sediment to become acidified and turn black and smelly.
Acidic corrosive substances accumulate at the bottom of the pond. Crabs live in such an environment. The floor is easily corroded by acidification. The corroded parts lose the outermost layer of protection and become slippery. There is no luster, and the bottom plate is yellow or black. Not only does it look unsightly, but it also affects the quality of crabs and affects sales.
Preventive measures: Maintain aquatic plants and apply grass fertilizer regularly.
The aquatic plants in the pond are rotten or there are no aquatic plants. Remove the aquatic plants that can be fished out to prevent them from continuing to rot. Regularly add Dikang No. 1 and Junmei No. 2. If the water quality is clear, you can fish some of the aquatic plants into the pond. Use Aquatic Plant God regularly. Dew ensures the nutrition of aquatic plants.
Regularly use EM mother bacteria to regulate water quality.
In situations that have already occurred or are very serious, use citric acid in an appropriate amount as appropriate.