What are the fishing techniques of natural saw edged blue crab crab fry? What are the fishing method

The first point is that the most important technique is to pay attention to the whole process of the house, the second point is to pay attention to the method of fishing, you must treat it correctly, and the third point is to pay attention to your model, you must master it well, otherwise you will die.

1) Crab basket bait: This is a special type of operation that is usually carried out in the inner bay or estuary. The basket is made of bamboo, and the crabs can easily enter, but there is no way to escape.

When trapping, bait** such as oyster meat is caught in a basket and sinks into the sea. After some time, the basket is hoisted to take out the crab seedlings, and so on. The seedlings caught in this way are robust, simple and convenient, and are an excellent method.

2) Capture by predatory habits: The phenomenon of foraging at high tide is very obvious. At high tide, blue crabs swim in groups to feed on areas where shellfish thrive.

Especially when the tide is just low around the shellfish farm, it is easy to catch crab fry.

At present, under the condition that the productive artificial seedlings of saw-edge blue crab have not yet made a comprehensive breakthrough, and the saw-edge blue crab breeding industry is developing rapidly, it is still an effective method and an important way to alleviate the shortage of saw-edge blue crab seedlings by fully developing and utilizing the natural saw-edge blue crab seedling resources, and losing no time in organizing the fishing of saw-edge blue crab big-eyed larvae, and strengthening the cultivation into juvenile crabs.

1 Fishing season for blue crab seedlings:The fishing season for blue crab fry varies from place to place, and can be caught almost all year round on the coast of the South China Sea from April, for example, there are two peak seasons in eastern Guangdong, namely May July and September November.

2 Fishing Method:Fishing methods are adapted to the locationWe have a lot of experience in harvesting natural crab fry from all over the world. Here are a few common ways to do this:

(1) Crab basket bait trapping:This is a kind of special operation, often carried out in the inner bay or estuary, the basket is made of bamboo, the crab is easy to enter and cannot escape, when trapping, the bait such as oyster meat is sandwiched in the basket, sinking into the sea, and after a period of time, the basket is lifted to take out the crab seedlings, and so on repeatedly. The seedlings caught by this method are strong, and the method is simple and convenient, which is an excellent method.

(2) Use predatory habits for capture:The phenomenon of foraging for fish at high tide is very obvious, and with the high tide they swim in groups to the site where shellfish grow and flourish to feed. Especially when the tide is just low around the shellfish farm, it is very easy to catch crab fry.

In some areas, crabs at low tide have the habit of hiding in burrows, and a large number of crab fry can be caught during the second dry tide by consciously digging some burrows or stepping on rows of footprints near tidal flats or shellfish farms where there are many crab crabs in the intertidal zone.

(3) Net fishing method:There are three ways to catch nets: one is to use fixed nets to fish, fix the nets on the seaside tidal flats, and when the tide rises, the crab fry enter the nets with the tide and can be caught; the second is to use push net fishing, which can be operated at high and low tide, and the catch is larger at low tide; The third is that when the tide rises to the shore, use a net to catch crab seedlings.

Because crab fry have the habit of foraging in the evening or at night, the catch in the evening or night is more than that during the day, and the crab fry are easy to die due to the high temperature during the day. Therefore, the general fishing of crab fry is mostly carried out in the evening or at 3 or 4 o'clock in the morning, and the effect is better.

The saline-alkali pond culture of blue crab is suitable for polyculture, and the use of blue crab likes to eat humus at the bottom of the pond and feeds on diseased individuals, which can not only effectively reduce the spread of diseases, make full use of the water space, but also increase economic benefits and achieve the purpose of increasing yield.

In the polyculture process, it is not necessary to feed the blue crab specifically. There are two modes of polyculture of blue crabs in saline-alkali ponds:

1) Choose a crab with strong physique, complete appendages, no injury, no disease, strong vitality and a weight of 50 grams in polyculture, and about 300 crabs can be stocked per mu. Tilapia, barracuda and other fish are stocked with the same amount of large-size seed as seed crabs. Through 4 to 5 months of growth, the saw-edged blue crab can grow to more than 400 grams, and the survival rate is about 50%.

2) 500 800 bean crabs in the stocking period of the general mu with shrimp polyculture mode, and the high-quality crab seedlings with neat specifications, strong vitality ability, no damage to the body surface, and no lesions in the crab body are selected. The stocking of shrimp fry is 30,000 40,000.

Blue crab and shrimp are polycultured, and bean crabs should be put when the shrimp seedlings grow to 3 4 cm to avoid the bean crabs from eating the shrimp seedlings. In the breeding to ensure the supply of artificial feed, production practice shows that to create a good shrimp and crab growth environment, in the case of sufficient bait, shrimp and crabs can live in peace, the survival rate of soybean crabs is about 25% 35%, and good economic benefits are obtained.

1.Bacterial diseases.

Vibrio bacterial disease.

Vibrio bacteria (e.g., Vibrio eel, Vibrio parahaematomycera) can cause diseases in aquatic animals such as fish, shellfish and crustaceans, and these diseases cause huge economic losses to the aquaculture industry. Mao Zhijuan et al. reported that Vibrio Cincinnati, Vibrio algaelyticus, Vibrio parahaemolyticus and other pathogenic vibrio species were isolated from the thoracic and foot tissue fluid of diseased blue crabs.

Crustacean ulcer disease.

Crustacean ulcer disease is mainly caused by chitin-degrading bacteria, such as the common Aeromonas, Xantin spp., Pasteurella and Vibrio microbibrio, etc., which mainly degrade the exoskeleton of crustaceans, causing the infection of chitin-containing epidermal tissues by chitin-degrading bacteria and fungi, causing ulceration and erosion of crustacean tissue.

Fungal diseases.

The fungal diseases of saw-edged blue crabs are mainly mycosis, such as Streptochytridium spp., Treptochytrid spp., and Treptochytrid spp., which can cause crab pathology. The larvae of saw-edged blue crabs with fungal diseases usually have poor phototaxis, decreased viability, and are mostly free in the middle and lower layers or bottom of the aqueous layer; The development of the egg is stunted and it cannot be hatched.

Viral diseases.

The viruses that cause disease in saw-edged blue crabs mainly include reovirus, herpes virus, and vitiligo syndrome virus.

Parasitic diseases.

The common parasites of the parasitic saw-edged blue crab are crab slaves, barnacles, gill worms, sea clams, etc. Once this parasite enters the crab body, it begins to multiply and infect the gill cavity, abdomen, muscles and other tissues and organs, and finally leads to the death of the blue crab.

Traditional prevention and control measures are mainly based on prevention, supplemented by **, which is mainly reflected in the following aspects:

1) Do a good job of disinfection of the whole pond before stocking and regular removal of silt.

2) Change the water at the right time.

3) Strengthen manual management: do a good job in the selection, stocking and daily feeding and management of crab seedlings to reduce the probability of the occurrence of blue crab disease.

4) Regularly use allicin to be splashed in the breeding pond to kill pathogenic microorganisms in the water body and eliminate the occurrence of bacterial diseases and parasitic diseases.

Breeding of new disease-resistant varieties.

Cultivating new varieties with strong disease resistance is one of the important measures to prevent the occurrence of saw-edged blue crab disease. The breeding of new varieties can improve the germplasm characteristics of crab carcasses and strengthen their disease resistance. The commonly used variety improvement technologies mainly include:

1) Breeding new disease-resistant crab species by distant hybridization technology.

2) Transgenic technology can express the stress resistance genes of crab species and improve disease resistance.

3) Multi-sport breeding technology can improve the survival rate of crab seed breeding and reduce the occurrence of diseases.

Utilization of biologics.

The congenital specific immune mechanism of the blue crab is not sound enough, it is easy to be invaded and pathogenic by some pathogenic microorganisms, and it is easy to produce drug resistance and other shortcomings with traditional drugs (such as oxytetracycline, penicillin, streptomycin, etc.), and cannot effectively develop diseases. The biological agents are inoculated with the crab body to improve the disease resistance, so as to play a preventive and leading role. Commonly used biologics mainly include high immune serum, antitoxin, etc.