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In the process of breeding crabs, you will encounter many common diseases, and now tell you about several disease prevention and control methods for crabs:
1. Water mold disease
The surface of the body of the sick crab, especially the wound site, grows cotton flocculent hyphae, and the sick crab is slow to move, the feeding is reduced, and the wound does not heal, causing the tissue at the wound site to ulcerate and spread, resulting in death. The cause is injury to river crabs and the intrusion of mold into the wound.
Prevention and control methods:
(1) Use salt water 3% to 5%, soak the sick crab for 5 minutes, and use iodine wine for 5%, and apply to the affected area.
(2) Do not injure the crab body during the operation of fishing, transportation, stocking and so on.
(3) Use peacock green 0.25ppm, sprinkle the whole pool, and apply it again every 5 days.
2. Ciliated disease
Ciliate protozoa can be attached to the joints, foot, dorsal shell, forehead, appendages and gills of the diseased crab. Sick crabs have more dirt on their bodies, their mobility and feeding ability are weakened, and the heavy ones can die before dawn. The disease is caused by excessive fertilizer in the pond, long-term non-change of water, and the proliferation of ciliate protozoa and parasitism in crab bodies.
(1) Mix 0.5~1ppm with potassium permanganate 5~10ppm with neogel and wash the sick crab for 10 minutes.
(2) Use peacock green 0.2 to 0.3 ppm and sprinkle along the pond edge where river crabs are densely packed with aquatic weeds.
(3) Use formaldehyde 5 ~ 10ppm, the whole pool sprinkled.
(4) Use ketone sulfate and ferrous sulfate (5:2) mixture of 0.7ppm and sprinkle the whole tank.
3. Intestinal and stomach blasting disease
Sick crab indigestion, intestine, stomach inflammation, flatulence, open the abdominal cap, lightly press the anus, visible yellow mucus outflow. The disease is caused by uneven feeding or spoiled or indigestible feed.
Prevention and control methods: (1) Regular feeding. (2) Add garlic to the feed, add 100 grams of garlic per kilogram of feed, and feed 3 times. (3) 1 g of furazolidone per kilogram of feed, made into medicinal bait, fed for 3 days.
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4. Molting disease
A crack appears at the junction of the posterior edge of the cephalothorax and the abdomen of the sick crab, but the old shell cannot be shed, and the sick crab is blackened until death. The cause of the disease is related to the lack of certain mineral elements during growth.
(1) Regularly use quicklime 10 to 15ppm, sprinkle the whole pool.
(2) Add an appropriate amount of metakinin and shell powder, bone meal, eggshell powder, fishmeal and other substances with more mineral content to the feed.
5. Curved arch back disease
The larvae have brown patches on their abdomen, no food in their intestines, and bend their tail backs to their heads, causing the larvae to die.
With oxytetracycline 0.5 ppm, regularly disinfect the aquaculture pond water body.
6. Polycoelastic disease
Polycoccosis belongs to the protozoa phylum , Ciliates , The order Tricariaceae , and the family Bellworm. Polycontolytic insects are dendritic, and individuals produce many cilia, which form large groups fixed on objects, and their roots parasitize the cephalothorax and abdomen of the larvae of the river crab. The eggs of egg-holding crabs also have polyconder parasitism. When stimulated, the entire group contracts. When the salinity of the sea is 0.003 and the water temperature is 18 to 20 ° C, the polycontoplasms multiply rapidly on the larvae. The intensity of the infection is 1 to 5, more than 2 to 3 times the size of the larvae, so that the larvae float on the surface of the water and appear white flocculent. Infected larvae are weak in mobility, weak in physique, difficult to molt, and severely die.
At present, two drugs are formaldehyde or neogelamine. Use a concentration of 10 ppm, sprinkle the whole pool, and bathe for 30 to 40 minutes. Use formaldehyde concentration of 20ppm whole pool sprinkling, encroachment bath for 8 hours, but within 1 day should be a water body exchange to exclude the remaining formaldehyde.
7. Rhomboid-shaped sea algae disease
Rhomboid seaweeds are part of the order Planktonic diatoms , whose cells are connected in colloidal form stellate or serrated populations with narrow rod-shaped shells.
Rhomboidal sea algae cells are 30 to 116 microns long and 5 to 6 microns wide, and are widely distributed, when the salinity of seawater reaches about 0.03 and the water temperature is 18 to 20 ° C, in the fertile and well-lit cultivation pond, it can rapidly reproduce on the larvae. After the larvae possess the seaweed, they constantly twist their abdomen and struggle to get rid of it, and the victimized larvae die within 4 to 5 days.
Preventive measures such as increasing the number of water changes, controlling light, and heating appropriately to promote larval metamorphosis are generally adopted.
8. Crab slave disease
Crabs belong to crustaceans, crustaceans, and root leaders. Crabs have parasitic crab slaves, there is no very obvious lesion, only the ventral surface of the umbilicus is slightly enlarged, open the umbilical cap, visible diameter 2 to 5 mm, thick 1 mm milky white or translucent granular insect body.
After the crab slave parasitizes, it directly destroys the gonadal development of the river crab, causing the river crab to grow slowly and become inedible. The disease is mainly caused by the salt content of the pond water above 0.001, the crab slave breeding in large numbers, and the spread of infection in the larvae.
The crab nu disease epidemic has seasonal variations, the proportion of females is larger than that of males, starting roughly from July, reaching a peak in September, gradually decreasing after October, and basically stopping after November.
(1) Thoroughly clear the pond, kill the crab slave larvae, commonly use bleaching powder, enemy insects, formaldehyde, etc.
(2) Replace the pool water and inject new fresh water.
(3) Use potassium permanganate 20ppm solution and soak the diseased crab for 10 to 20 minutes.
(4) Use copper sulfate 8ppm solution and soak the sick crab for 10 to 20 minutes.
(5) Copper sulfate, ferrous sulfate (5:2), with 0.7ppm solution, sprinkle the whole tank.
9. Rotten shell disease
The tip of the aquatic disease crab foot is broken, becomes a black ulcer and decays, and then the white spots appear on the various segments of the foot and the dorsal carapace and chest plate, and gradually become a black ulcer, and in severe cases, the carapace is corroded into a hole, and the muscle or skin membrane can be seen, resulting in the death of the river crab. The disease is caused by damaged infection bacteria at the tip of the river crab foot.
(1) Use quicklime to thoroughly clear the pond, keep the water quality clean, and often fill new water in summer to remove the silt at the bottom of the pond. During the feeding period, the whole pool of quicklime is sprinkled regularly, and its concentration is 15 to 20ppm.
(2) The treatment is sprinkled with bleach powder 20ppm concentration in the whole pool, and sulfonamide drugs are added to the feed, 1 g per kilogram of feed is added, and continuous feeding is 3 days.
10, there is something wrong
After the river crab's cheeks, forehead, and foot joints are attached to the silky algae such as sponges, the river crab moves slowly and eats less, such as blocking the water hole, causing the river crab to suffocate and die. The disease usually occurs at the end of April and the beginning of May.
prevention and cure:
(1) Avoid using farmland fertilizer.
(2) After the peak period of river crab growth molting in April and May, cover 1/2 of the pond water surface with green ash (grass and tree ash), so that the water green lacks sunlight and dies, and the dead water green is fished out.
(3) From June to July, 20 kg of quicklime (water depth of 1 meter) per mu is sprinkled in the whole pond, and by increasing the pH value, inhibiting the breeding of water green, and using it again every 10 to 15 days to eliminate the infection of this disease.
(4) Sprinkle with a whole tank of copper sulfate, and use a concentration of 0.8ppm to kill moss better.
(5) Sprinkle the whole pool with raw gypsum powder to show a total of 25 to 30ppm, spray 3 times in a row, and the interval between each time is 3 to 4 days.
11. Black gill disease
Sick crab gills are infected and discolored, when the disease is mild, the left and right gill filaments appear dark gray or black, when the disease is serious, the gills all become black, the sick crabs are slow to move, breathing difficulties, commonly known as sighing disease, the disease mostly occurs in the late stage of adult crab breeding. Deterioration of water environmental conditions is the main cause of the disease.
(1) Clear the pond with quicklime, remove the silt at the bottom of the pond, and if the disease occurs during the feeding period, sprinkle the whole pond with quicklime water, the concentration is 15 to 20ppm, and it is used twice continuously.
(2) The diseased crab is soaked in 2 to 3 ppm furazolidone solution for 3 to 4 times.
12. Rotten limb disease
The sick crab's abdomen and appendages rot, the anus is red and swollen, feeding is reduced or stopped, the activity is slow, and finally it is unable to molt and die. The disease is caused by infection caused by injuries caused by predators during capture, transport, stocking or growth.
(1) The operation should be careful, do not cause the crab body to be injured.
(2) Soak in furazolidone 2ppm solution for 10 minutes before stocking.
(3) Sprinkle with oxytetracycline or furacillin 1ppm whole pool.
(4) Use quicklime 15 to 20ppm, sprinkle the whole pool, and use it 2 to 3 times continuously.
13. Edema disease
The abdomen, umbilicus and under the dorsal shell of the sick crab are enlarged and transparent, and the sick crab stops eating at the edge of the pool and dies in the shallow waters of the pool. The disease is caused by infection with bacteria injured in the abdomen of river crabs during the cultivation of their crabs.
(1) In the breeding process, the operation should be careful, do not cause injuries to the abdomen of the crab body.
(2) Sprinkle with oxytetracycline or furacillin 1ppm and sprinkle the whole pool.
(3) Use furazolidone 0.2ppm and sprinkle the whole tank.
(Source: China Aquatic Products Network )