Why Crab Farming Fails and How to Improve the Survival Rate

It's crab season right now, and crab prices have stayed high, which shows that crab farming is still quite profitable. However, many people's farmed crabs either die, produce no yield, or fail to reach size. The key to farming crabs is having the right techniques and professional guidance. So what are the reasons for crab farming failure? How do you farm them so they won't die?

1. What are the reasons for crab farming failure?

If you want to raise crabs well, you need to know which factors cause crab deaths, poor size, and low yield. Here is a specific analysis from the following aspects:

1. Seedstock: Seedling selection is crucial for crabs. You must choose high-quality crab seedlings, preferably pond-raised seedlings from the original pond. Those with dirty shells or no vitality should not be used, and seedlings treated with chemicals should definitely not be used. When buying crab seedlings, it is best to visit large-scale farms in person to inspect the conditions.

2. Weather: Sometimes severe weather can also affect yield, so you should pay close attention to weather conditions regularly. Continuous rainy weather during crab molting and the second molt, as well as prolonged high temperatures later on, can all affect size and yield. Preventive measures should be taken at these times.

3. Chemical residues: Many farmers now like to use trichlorfon and pyrethroid drugs to clear ponds. Although the pond-clearing effect is good, the problem of chemical residues is serious and affects crab molting and growth.

4. Water quality and aquatic plants: Crabs go through 5 molts. From after the second molt, you need to pay attention to water quality and aquatic plants. At least two or more types of aquatic plants should be grown in the pond, not just a single type. In the middle and later stages of farming, some heat-tolerant aquatic plants must be planted, such as hydrilla (Hydrilla verticillata), tape grass (Vallisneria), and others.

5. Other factors: Burst anti-escape nets causing crabs to escape, human theft, and so on, can all have an impact, but these are not the major ones. Just pay more attention and observe regularly.

2. How do you farm crabs so they won't die?

If you want your farmed crabs not to die, the most critical thing is to master the techniques and have professional guidance. Here is what to do specifically from the following aspects:

1. Pond conditions: Convenient transportation, easy water intake and drainage, abundant water supply, good water quality with no pollution, and a level pond bottom.

2. Crab seedling selection: Choose high-quality crab seedlings. Generally, select seedlings that are uniform in size, free of disease and injury, strong in constitution, and active in crawling.

3. Planting aquatic plants in the pond: The level of crab yield mainly depends on the amount of aquatic plants and bait organisms. Aquatic plants are one of the natural baits that crabs love to eat, and they also purify water quality. They are also a place for crabs to rest and hide from predators. The planted area should account for more than 70% of the pond area. The main varieties include hydrilla (Hydrilla verticillata), tape grass (Vallisneria), elodea (Elodea), duckweed, mosquito fern (Azolla), water hyacinth, water lettuce, and others.

4. Pond sterilization and disinfection: Pond clearing and disinfection work must be done well. It mainly kills wild miscellaneous crabs, harmful organisms, and various pathogenic bacteria in the crab pond. Every winter, excess mud in the crab pond should be removed in time so that the bottom mud does not exceed 10 cm. 10 to 15 days before releasing crab seedlings, carry out one chemical pond-clearing treatment. Depending on the water source conditions, you can choose the dry method of pond clearing, broadcasting quicklime at 75 kg per mu or bleaching powder at 4 to 5 kg over the whole pond; or the water-retained method of pond clearing, broadcasting quicklime at 25 to 30 mg/kg or bleaching powder (containing more than 25% available chlorine) at 1 mg/kg over the whole pond.

5. Anti-escape facilities: Anti-escape facilities should be set up according to the type of farming. For pond crab farming, anti-escape facilities include anti-escape ditches and anti-escape walls; for lake enclosure farming, bamboo screens, walls, bottom cages, and others are used.

6. Releasing seedlings: When releasing seedlings, pay attention to temperature differences. Purchased seedlings cannot be placed directly into the pond. They should first be soaked in water for 2—3 minutes, taken out and left for 10 minutes, and this should be repeated 2—3 times. This can improve the survival rate.

7. Pond water quality control: Water quality is also crucial for farming crabs. The most suitable pH for crab pond water is between 7.5—8.5. The dissolved oxygen in the pond water should be kept above 5MG/1; below 2MG/1, crab deaths will occur. Therefore, quicklime should be used regularly to adjust and improve water quality. Be sure to change the water frequently, maintaining a water level of 0.6-0.8 m, and adjust it to 1-1.2 m in high-temperature seasons. Generally, change the water once every 7-10 days, and once every 3 days during high temperatures, adding 10-20 cm of water each day.

8. Feeding in the pond: Crabs are omnivorous animals. Before releasing crab seedlings, put in 300-500 kg of snails per mu to cultivate the basic bait for crabs. In terms of feeding, feed once each in the morning and evening. In the early stage of stocking, focus mainly on animal-based bait, then gradually increase the feeding of plant-based concentrated feed. In the later stage of farming, if you want the crabs to meet size standards, you should increase plant-based concentrated feed and animal-based bait. The feeding method for crabs is mainly based on season, weather, water quality, and crab activity, feeding at fixed times, fixed locations, with fixed quality, and fixed amounts.

9. Crab diseases: At present, many crab diseases can cause large numbers of deaths, and the affected area is large. The disease season has no regular pattern and runs through the entire farming process. Prevention of crab diseases is more important than treatment. The main diseases include edema disease, rotten limb disease, ciliate disease, trembling disease, black gill disease, and others. Preventive measures should be taken according to different situations.

10. Crab harvesting: Generally, starting in October, harvest and bring to market at the right time according to temperature and market conditions.

Conclusion: This is a brief introduction to crab farming. I hope it is helpful to everyone. Crab farming must be done with intensive methods. It is best to go to professional farming locations to learn the relevant technical knowledge and manage scientifically, so that you can ensure your farmed crabs will not die and cause low yield.