CATDOLL : CATDOLL: How to improve the benefits of river crab farming

1. How to improve the benefits of river crab farming

In recent years, the scale of river crab farming has continued to expand and the output has continued to increase, resulting in oversupply in the market, causing crab prices to fall, and seriously affecting fishermen's enthusiasm for crab farming. In order to make full use of resources, tap production potential, and improve farming efficiency, crab farmers should focus on the following aspects:

1. Planting composite aquatic plants

Elodea is planted around the pond, Hydrilla verticillata, Vallisneria, Water spinach, Duckweed, etc. are planted in deep water areas, and Artemisia and reeds are planted in shallow water areas. The coverage rate of aquatic plants should reach more than 50%.

2. Apply basal fertilizer at the right time

7-10 days before stocking the seedlings, add about 50cm of water and add 200-300kg/667㎡ of fermented and disinfected livestock and poultry manure to cultivate plankton and provide biological bait for the crabs that are about to enter the pond.

3. Reasonable placement of snails

The snails were released three times instead of twice. The first time was before the Qingming Festival, with a quantity of 200-300 kg/667 m2. At this time, the temperature was suitable, allowing them to naturally reproduce young snails in the pond, providing a continuous supply of suitable bait for young crabs; the second time was released in June, with a quantity of about 100 kg/667 m2; the third time was released in August, with a quantity of 150-200 kg/667 m2.

4. Control moss growth

In the early stage of moss germination, use biological moss killer (main ingredients: compound active agent, biological inhibitor, etc.), the dosage is 20-30ml/667㎡ (1m water depth), the method is to dilute it 2000 times with water and then sprinkle it on the moss concentration area, and the machine should be turned on for oxygenation. Smaller ponds can be removed manually.

5. Scientific feeding of bait

Feeding should adhere to the "five fixed" principles, namely: fixed time, fixed location, fixed quality, fixed quantity, and fixed person. From March to May, feed mainly with compound feed with a protein content of 36%-40%, supplemented by some fresh frozen fish; from June to August, feed mainly with compound feed with a protein content of 28%-30%, supplemented by some corn, wheat and other grains; from September to October, feed mainly with frozen fish, supplemented by granular feed with a protein content of 38%-40%. Feed twice a day, once in the morning and once in the afternoon, with the afternoon feeding as the main feeding, accounting for 60%-70% of the daily feeding. The feeding amount should be eaten within 2 hours of feeding.

6. Regulate water quality

Add water once every 5-7 days, adding 15-20cm each time to keep the water fresh; change the water once every 15-20 days, replacing 20%-30% of the old water each time to keep the water tender and refreshing; use quicklime once every 10-15 days, with a dosage of 10-15kg/667㎡, to adjust the pH value between 7.5-8.5; use EM bacteria (compound biological agent) once every 20-30 days, with a dosage of 1-1.5kg/667㎡ to improve water quality and bottom quality; turn on the aerator at the right time to keep the dissolved oxygen in the pool water above 5mg/l.

7. Strengthen the management of the molting period

Change the water once 5-7 days before the river crab molts, and feed it with bait mixed with molting agent, vitamin C, Sanhuang powder, etc. to promote smooth molting and accelerate development and growth.

8. Strengthen disease prevention and control management

Use bromine chloramine powder (manufacturer: Wuxi Zhongyi Biotechnology Co., Ltd.) once every 15 days or so, the dosage is 200g/667㎡ (1m water depth), dilute it 1000 times with water and evenly sprinkle it in the whole pond to prevent gill rot and enteritis; from April to May, use special concentrated filamentous insect net (main ingredients: 1% doramectin, nano zinc, insecticide synergist) once, the dosage is 20-25ml/667㎡ (1m water depth), dilute it with water and evenly sprinkle it in the whole pond to kill various ciliates parasitic on the gills and body surface; from July to September, feed once every 20-30 days with 0.1% fresh garlic juice or 1% dysentery net mixed bait to enhance the disease resistance of river crabs. In addition, we must also prevent water rats, frogs, water birds and some ferocious carnivorous fish from harming river crabs.

2. How to raise river crabs in Heilongjiang?

River crab farming is carried out in almost all of Heilongjiang Province. For many years, Liaoning Erli River Crab Seedling Farming Base has cooperated in farming river crabs in a vast area of ​​Heilongjiang from Longjiang County, Qiqihar City in the west to Fuyuan County, Qitaihe, and Luobei in the east, Nenjiang, Wudalianchi, Heihe, and Sunke in the north, and Tailai County, Zhaoyuan, and Zhaozhou in the south. Heilongjiang Province is rich in water resources, and river crabs have abundant natural bait. The water, fertilizer, and grass are lush, and there are plenty of fish, shrimps, and snails. In many places, large crabs can grow without almost any feeding. As long as you choose high-quality crab seedlings, reasonably match the ratio of male and female crab seedlings, plant the seedlings at the right time, and catch the adult crabs in time, you can raise them to a certain yield, to a certain size, and to make a high profit. For more information about crab farming in Heilongjiang, please refer to the website of River Crab Farming.

It’s too cold. The largest river crab breeding base in the north is in Panjin, Liaoning. I haven’t heard that Heilongjiang also breeds river crabs.

River crab farming requires both fresh water and salt water (it doesn't have to be sea water, saltwater lakes can also be used to produce lead). It seems that Heilongjiang does not have these conditions.

Panjin, Liaoning

It’s too cold!

3. What are the factors that affect the successful breeding of river crabs?

The influencing factors are:

1. Seedling quality

1. Deterioration of parent quality;

2. The crab farming technology is backward, the water exchange conditions are poor and the pond aging problem has not been solved. Only the output is focused and the quality is ignored;

3. Nutritional deficiency. In order to prevent the premature maturation of seedlings and the number of old crabs, choose low-protein feed and feed in insufficient quantities.

2. Over-reliance on aquatic plants

During the breeding process, most of the energy was spent on aquatic plants, while the growth of river crabs was ignored. For example, in the early stage, the water level was lowered in order to grow grass, and the average water depth could only be about 50 cm, or even lower. This would lead to large changes in water temperature, turbid water, moss growth, and even severe ammonia nitrogen and nitrite exceeding the standard, affecting the growth of river crabs. The middle and late stages of breeding are at high temperatures, and there is a situation in which there is little or no grass in the late stage. Instead of paying attention to oxygenation and stabilizing water, blindly dealing with problems such as blue algae and dinoflagellates caused by the lack of grass, resulting in severe hypoxia and a large number of crabs dying.

3. General lack of dissolved oxygen

Hypoxia is a common problem in river crab farming. On the one hand, because the model of growing crabs with grass is an oxygen-deficient model, the oxygen utilization rate of aquatic plants is low, and most of it goes into the air and consumes a lot of oxygen. On the other hand, there are few aerators installed. Most ponds do not have aerators. Only when there is a lack of oxygen do they rely on some water pumps to increase oxygen. In a few areas, aerators are installed more vigorously, and the farming benefits are very optimistic.

4. Nutritional Deficiency

River crabs are fed once a day, and the phenomenon of being hungry for one meal and full for the other is prominent, and the feed utilization rate is low. From the perspective of feed selection: the quality of fresh frozen fish is difficult to guarantee; the granular feed of Sophora japonica cannot be made too good, otherwise the price will be too high and farmers will not accept it. River crabs are omnivorous animals, and there are many types of feeds to feed them. The feed coefficient is difficult to calculate, and it is difficult to measure the quality of the feed.

5. Improper approach to problem solving

In the year-round breeding, there are many problems in each stage, such as the difficulty in fertilizing the water, excessive ammonia nitrogen and nitrite, failed molting, moss, massive reproduction of zooplankton, etc. in the early stage; turbid water, dirty grass, no growth of aquatic plants, crabs caught in the grass, etc. in the middle stage; hypoxia, enteritis, disease, etc. in the late stage.

6. Blindly invest in costs

Although the overall benefits of domestic river crab farming are not high, the profit margin of river crab farming is large, with the highest profit per mu reaching tens of thousands, and the amount of profit is directly proportional to the specifications and output. In pursuit of high profits, people blindly increase feeding and release snails to increase output and specifications. This will be counterproductive when water quality and dissolved oxygen cannot be guaranteed. This not only wastes costs but also increases the risk of farming.

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