Why do marine crabs die in large numbers during shelling?

The death of marine crabs in the shelling period shows that a large number of marine crabs die before shelling (failed shelling), and many marine crabs die after shelling (too much physical consumption after shelling, soft shell does not harden, etc.). The causes of death of marine crabs during shelling period are as follows:

(1) the water body is polluted and the dissolved oxygen is low, which affects shelling and leads to death.

(2) unbalanced nutrition of marine crabs (lack of calcium, phosphorus, magnesium, zinc, iron, vitamins, etc.)

(3) if irritant drugs are used during the shelling period, some people will die.

(4) the pH value is too low or too high to be in the range of suitable pH (the suitable pH is 7.8-8.4).

(5) the content of molting hormone in marine crabs can not meet the requirements of normal shelling.

(6) the shelling activity of marine crabs will be hindered when they get sick.

(7) Marine crabs parasitized by ciliates sometimes cause failure of shelling.

(8) during the shelling period, the factors such as water temperature, water level and salinity change too much.

Treatment methods: different treatments are made according to the above reasons:

(1) pay attention to the changes in water quality, improve the water quality or sprinkle grain oxygen to increase the dissolved oxygen in the pond, so as to provide the dissolved oxygen needed for shelling of marine crabs.

(2) add multi-dimensional crab to the diet to balance its nutrition, sprinkle hard shell treasure in the whole pool, increase the content of trace elements, enhance disease resistance and promote shelling at the same time.

(3) during the peak shelling period, avoid sprinkling irritant drugs in the water (such as quicklime, trichlorodisinfectant, algaecide, moss remover, copper sulfate, etc.); at the same time, the number of operations in the pond should be reduced to prevent marine crabs from being frightened.

(4) adjust the seawater to a suitable pH range.

(5) to find ciliates, timely use shrimp and crab ciliates, ciliates or crab Jing'an to clean ciliates.

(6) fresh sea water can be replaced in the early stage of the shelling peak (3-5 days), and the water quality can be adjusted by Dr. Hai's super microbes.

2. What are the foods of marine crabs?

The bait varieties of marine crabs are mainly natural bait, such as small shellfish, small miscellaneous fish and shrimp, crabs, barnacles, snails and snail ships. Frozen fish and so on, in addition, can also be fed to animal offal, artificial formula feed is also being tried.

What does g / 1000L mean?

On a lot of data, we will see the word of a certain gram / 1000L, which indicates the concentration of a substance in water. The concentration of a substance dissolved in 1 gram weight in a ton of water is 1 gram / 1000L, that is to say, the concentration of 1 gram per cubic body of water is 1 gram / 1000L. Similarly, if the concentration of 5g / 1000L is 5g / cubic water, then the dosage of water depth of 1 mu and 1m is calculated as follows: 5g / m3 water × 66m2 × 1m water depth = 3330 g.

4. What are the factors related to the occurrence of marine crab diseases?

There are always a lot of diseases in the process of marine crab culture. light ones affect the growth of marine crabs, and in serious cases, it will lead to a large number of deaths and bring serious losses to aquaculture production. So how on earth did these diseases come about? After long-term investigation, it is found that the occurrence of all these diseases is related to the following factors: the quality of the water environment, the health of marine crabs, and the disease-causing organisms in the water (or the bottom of the pond). The occurrence of all diseases is related to these three factors, which together lead to a variety of problems in the breeding process of marine crabs. At the same time, these three also complement each other, that is to say, when the water environment becomes bad, the pathogenic organisms in the water are bound to increase greatly, and at this time, the physique of shrimp and crabs becomes weaker due to poor water quality, so diseases will occur. In the actual production process, we can analyze the problems from the above three aspects.

5. What is the relationship between the disease of marine crabs and the pathogenic organisms in the water environment?

With the exception of nutritional diseases (diseases caused by malnutrition), almost all diseases are related to pathogenic organisms in water. Pathogenic organisms are: bacteria, fungi, parasites, viruses and so on. There are all kinds of disease-causing organisms in the usual aquaculture water, so we need to pay attention to three points:

(1) in good water bodies, the number of these pathogenic organisms is very small, which does not cause marine crabs to get sick, so they usually do not get sick.

(2) the pathogenic organisms (bacteria, viruses) in the water will multiply in large numbers when the water quality is poor, and a large number of pathogenic organisms will invade healthy marine crabs, thus causing marine crabs to get sick.

(3) even when there are many pathogenic organisms in the water, healthy marine crabs are generally not easy to get infected and get sick. The key point is that most of the marine crabs are not in good health at the time of onset.

Usually, diseases such as rotten Gill, black Gill, rotten limb, enteritis and decaying shell (carapace ulcer) are caused by bacteria; ciliosis is caused by parasites; mycosis is caused by fungi; yellow water disease and white water disease are caused by comprehensive factors.

6. How should marine crabs get yellow water disease and white water disease?

Because the yellow water disease and white water disease of marine crabs are caused by bacteria, viruses and other comprehensive factors, it is relatively difficult to treat, but it is not impossible to treat when the internal organs are still intact at the initial stage of the disease. At this time, the method of internal administration and external use can also recover a certain loss, that is, adding crab disease and antiviral Chinese herbal medicine fungicide or Sanhuang powder to the feed to enhance its antibacterial and antiviral ability. At the same time, external use of fungus Duqing, double-stranded quaternary amine salt iodine and so on were thoroughly disinfected and sterilized in the whole pool. However, once the disease comes to the later stage of visceral ulceration, there is no way to return to heaven, so the disease focuses on prevention. It is often disinfected with bacteriocin or aquatic bromochlorohydantoin, and the feed is often added to the diet of crabs with multi-dimensional crab disease, Sanhuang powder or bacterial poison to kill stars, so as to enhance the disease resistance of marine crabs.

The yellow water disease and white water disease of marine crabs are often caused by the change of aquaculture water quality, especially by the emergence of a large number of noctilucent insects in the sea area. the water quality of this kind of pond is often black and smelly, and it is easy to occur in high temperature season in summer. Therefore, the prevention and control of these diseases should start with the improvement of water quality or killing noctiluca scintillans with bacteriophage. we can use the whole pond to sprinkle microorganisms to purify the pond water and quickly degrade the organic matter and humus in the pond water. transform ammonia nitrogen, nitroso nitrogen and other toxic and harmful factors in pond water. At the same time, the main mechanism of increasing oxygen in the whole pond is that it can rapidly increase the dissolved oxygen at the bottom of the pond where the water quality has been seriously anoxic, and rapidly oxidize the toxic substances such as hydrogen sulfide, ammonia nitrogen and nitroso nitrogen gathered in the bottom of the pond. reduce the toxicity of these toxic factors to benthic marine crabs, through these means, the water quality of the pond condition can be quickly improved, but also put an end to the occurrence of diseases.

7. I am a marine crab farmer. I would like to ask why my marine crabs still suffer from serious disease frequently after using some disinfectants and internal medicine on the market.

At present, there are many kinds of drugs popular on the market, many of which are products produced by informal manufacturers without any quality assurance. In addition, some internal medicines and disinfectants are products developed by manufacturers for freshwater aquaculture. Due to the large buffer capacity of seawater to drugs, there is no effect. At this time, disinfectants and internal medicine and water quality improvers produced by some regular manufacturers should be selected to buy. at the same time, we should see clearly the marked object of use on the description of these products, and the key is to treat the patients and avoid using drugs indiscriminately, otherwise, it will not only waste money but also delay the treatment of the disease, resulting in unnecessary losses.

8. What are white crabs, thin crabs, flower crabs and red paste crabs?

White crab: unmated female crab with an individual of 150 to 200 grams, characterized by a grayish black belly navel. In strong light, there is no clear gonadal outline on both sides of the carapace from the base of the eye to the ninth tooth. White crabs should be reared with males at the ratio of 3:1 or 4:1 (female / male) to mate. After a reproductive molt, the white crab can be bred with enough food for 40-50 days.

Lean crab: a newly mated female crab with an individual of more than 250 grams. Observed in strong light, there is a semilunar outline of the ovary on both sides of the carapace from the base of the eye stalk to the ninth lateral tooth, which is transparent above and below, which is the expansion range of ovarian maturity. This kind of crab can become green crab with plump ovaries after being raised for 30-40 days.

Flower crab: a female that has been mating for nearly one month. The ovary has begun to mature and expand, but it has not yet extended to the edge of the carapace. In the light, some transparent places can be seen, like a half-moon-shaped curve. The dots above the navel turn from milky white to yellow, and then after 15-20 days of intensive breeding, you can develop red paste crabs.

Red paste crab: the ovary has matured, weighing more than 250 grams, the carapace is full of red ointment, the body is strong, there is no transparent area under light observation, the dots above the navel have turned red, and some carapace have been bright red.