How should crab seedlings be selected and scientifically cultivated?
Crabs are delicious and nutritious, and have been a delicacy at feasts since ancient times. Moreover, there is a great variety of crabs, with about 600 or more species in China, and their farming areas are widely distributed. Crab farming has also evolved from the initial resource release-type farming to the current intensive high-density intensive culture, with an output value of more than ten billion yuan. Of course, the key to raising crabs well lies in crab seedlings, so how should crab seedlings be selected? How should they be scientifically cultivated? Let's learn about it below.
How should crab seedlings be selected?
Crab seedlings should generally be selected with a clean underside, strong vitality, and a hepatopancreas clearly marked with small red dots, mainly local seedlings. When selecting seedlings, also pay attention to choosing from the same batch crab seedlings that are relatively uniform in size, with complete appendages, good vitality, and a back that is light yellow with a slight tinge of green. Then randomly take about 10 crab seedlings from the selected seedling pond, place them on a wet towel to keep them moist and keep them overnight, and observe carefully to see whether there is any yellow discharge or foaming, so as to prevent getting crab seedlings suffering from chronic intestinal diseases or infected by pathogens.
How should they be scientifically cultivated?
1. Pond clearing and disinfection
Before releasing the seedlings, drain the pond water, then thoroughly clean and level the pond bottom. If there are still aquatic plants in it, also remove the aquatic plants completely. Some ponds have only recently been planned, and there is not much silt at the bottom, so the silt can be dug up manually and, after being dried, used to reinforce the pond embankment. In addition, disinfection work is essential. The more common pond-clearing drugs include pyrethroids, organophosphates, chlorine preparations, quicklime, and so on.
2. Stocking time and density
The time for releasing seedlings is generally from January to March, and in order to achieve relatively high yields, farmers generally stock at a density of 2000-3000 seedlings/mu (but high-density farming will put great pressure on the water quality environment). If temporary holding is used to stock crab species that have molted 1-2 times (spring stocking), then the stocking amount per mu is about 600. If conditions permit, it is even better to stock after the beginning of spring when the water temperature reaches above 8°C.
3. Water fertilization preparation
Before releasing the seedlings, add part of the new water. Generally fertilize the water once, mainly with EM bacteria, and at the same time the nutrition of the fertilizer should also be comprehensively guaranteed to achieve a good water fertilization effect. Fertilize the water 5-7 days before releasing the seedlings. In the early stage, the temperature is low, and multiple and larger amounts of fertilization are needed to achieve the effect. After releasing the seedlings, additional fertilization is also needed several times to stabilize the water quality.
4. Method of releasing seedlings
Crab seedlings, especially non-local seedlings, decline in physical condition after long-distance transport. Directly putting them into the pond causes great stress, and they are prone to coming ashore and climbing along the edges. If the weather is unstable or it rains when releasing the seedlings, large numbers of deaths often occur. Therefore, when releasing the seedlings, it is recommended to first place them at the pond edge to adapt to the temperature, then use pond water to sprinkle or soak the crab seedlings for 3-5 minutes, repeating 2-3 times, so that they spit out the mud or impurities on their stomachs and gills and adapt to the water quality.
5. Scientific feeding
After releasing the seedlings, feed them in a timely manner. Most crab seedlings are not fed before transport and have a weak constitution, so it is recommended to start feeding on the 5th day after releasing the seedlings, mainly with starter feed and fish paste, to restore their constitution and improve disease resistance.
Before farming crab seedlings, the correct release of crab seedlings is particularly critical. This is also the key to improving the survival rate of crab seedlings, and ultimately it will also affect farming returns, so farmers should pay extra attention. In addition, there are many varieties of crab seedlings, and it is recommended to choose varieties that sell well locally.
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