Detailed Explanation of Key Technical Points for Cage Culture of River Shrimp

AbstractCulture water area: need to select a water area with a pH value between 7-8.5 and little sludge. Cage construction: generally use polyethylene netting, bamboo floats, etc. to make rectangular cages of suitable specifications, and set up anti-escape nets. Stocking shrimp seed: cage shrimp farming can cultivate 2 batches; the 1st batch can be in March-April, stocking overwintering shrimp seed; the 2nd batch can be in July-August, stocking shrimp seed bred and cultivated in the current year. Feeding management: feed 2 times a day, do well the work of four diligences, four preventions, and removal of wild species.

I. Select a suitable culture water area

For cage shrimp farming, generally a water area with sufficient sunlight, clean water quality, a pH value between 7-8.5, a water depth of more than 2m, little sludge, and flat bottom sediment is selected. Usually these are unpolluted lake branches, river channels, or reservoir bays and other places. The better the environment, the more suitable it is for oriental river prawn growth, and the better the culture results that can be achieved.

II. Material and structure of the cage

1. The netting is generally made of polyethylene netting and bamboo floats; ropes are threaded around the bottom of the cage and tightened and fixed together with bamboo strips and the lower ends of bamboo tips, used to replace sinkers. The cage is suitable to be built into a rectangle with specifications of 10*6.67*1.3m, which can reduce the production cost of the cage, increase water exchange, improve wind resistance, and facilitate selective harvesting. The main factor affecting the water quality inside the cage is the mesh count of the cage netting.

2. On the bamboo frame of the cage, a thick bamboo strip 1.3m long needs to be tied every 2-3m; the lower end of the bamboo strip is tightly tied to the bottom rope of the cage, and the upper end of the bamboo strip is tightly tied to the upper-mouth rope of the anti-escape net. The four corners of the upper mouth of the anti-escape net should also be tied with ropes, then tightened with bamboo tips and fixed to the upper part of the bamboo tips. Close to the four corners of the cage, drive 1 bamboo stake each, with the lower part in the soil and the upper part exposed above the water surface, then tie the top of the bamboo tips fixed on the cage tightly to the bamboo stakes with ropes. Let the cage sink 0.9m below the water surface, leaving 0.4m exposed above the water surface as the anti-escape net. Arrange every 5 cages in a row, with a cage spacing of 4-5m and a row spacing of 5-6m.

3. The four corners of the upper mouth of the anti-escape net are also tied with ropes, tightened with bamboo tips, and bound firmly to the upper ends of the bamboo tips. On the cage bamboo frame, a thick bamboo strip 1.3 meters long is tied every 2-3 meters; the lower end of the bamboo strip is tied to the bottom rope of the cage, and the upper end is tightened with the upper-mouth rope of the anti-escape net and tied firmly. Close to the four corners of the cage, drive 1 bamboo stake each, with the lower end entering the mud and the upper end exposed above the water surface. Then tie the top of the bamboo tips fixed on the cage to the bamboo stakes with rope loops. Let the cage sink 0.9 meters below the water surface, leaving 0.4 meters exposed above the water surface as the anti-escape net. Cage layout: every 5 cages form a row, with a cage spacing of 4-5 meters and a row spacing of 5-6 meters.

III. Stocking shrimp seed

Using cages for shrimp farming, 2 batches can be cultured in 1 year. The 1st batch of shrimp is stocked with overwintering shrimp seed, generally carried out in March-April. The stocking amount is 50,000-60,000 per mu, with shrimp fry specifications of 1000-2000 per kilogram. After harvesting in mid-July, autumn culture is carried out, which is the 2nd batch; usually in late July to August, shrimp seed bred and cultivated in the current year is stocked, with a stocking amount of 80,000-100,000 per mu and shrimp fry specifications of 2000-5000 per kilogram.

Before shrimp seed enters the cage, it must be weighed and counted with water. During the operation, shrimp seed must not be piled or pressed, must not be out of water for more than 5 minutes, and must not be exposed to the scorching sun. The shrimp seed stocked in the same cage must be stocked sufficiently at one time, and the specifications must be uniform. Seed stocking should be carried out in the evening or morning of a sunny or cloudy day; if the shrimp seed has been transported, it needs to be temporarily cultured for 1 day before being put into the cage. When stocking captured natural shrimp seed, dead fry must first be removed.

IV. Feeding method for feed

1. The bait feed fed in cage culture is similar to the bait feed fed in pond culture. However, cage shrimp farming needs to appropriately increase the number of daily feedings; generally feed 2 times a day, 1 time at 8 a.m., with a feeding amount of 1/3 of the day's bait amount, and 1 time after 5 p.m., with a feeding amount of 2/3 of the day's bait amount.

2. Powdered bait is generally placed on aquatic plants, while other bait is broadcast over the whole cage. The daily feed feeding amount is 5%-8% of the weight of shrimp stored in the cage. After feeding the bait, carefully observe the feeding situation of the shrimp; if the fed bait is quickly eaten up, the bait amount can be appropriately increased on that day and the next day. In addition, when the temperature and climate are suitable and the weather is good, the feed feeding amount can also be appropriately increased.

3. Generally, oriental river prawn farming uses compound feed with a feed coefficient between 4.34-5.47, and the protein content of the compound feed fed is required to be above 35%. Powdered feed loses relatively seriously, and the feed coefficient is relatively high. The use of compound pellet feed for oriental river prawn farming should be advocated, as this can both maximize the utilization rate of the feed and also make the oriental river prawn yield higher.

V. Management work of cage shrimp farming

1. Four diligences: diligent inspection, diligent patrolling, diligent brushing of cages, diligent maintenance.

2. Four preventions: prevent human destruction and theft, prevent cage sinking and shrimp escape, prevent strong winds from overturning cages, prevent pesticide pollution.

3. Removal of wild species: remove dangerous wild fish and other enemies.

After shrimp seed is put into cages for culture for 1 month, invasion by dangerous animals such as river crabs, carp, eels, mandarin fish, topmouth gudgeon, and hemiculter fish must be prevented; once discovered, they should be removed immediately. The general method of removing wild fish is to pull up the cage, gather the fish and shrimp in one corner of the cage, and then catch the wild fish or harmful fish out by hand, removing them about once every half a month. Attention should also be paid to killing water rats to avoid water rats eating shrimp; water birds will also cause harm and can be driven away with bird guns.