Techniques for large-scale rearing of bream summer fry, suitable for triangular bream and blunt snout bream

Bream (triangular bream, blunt snout bream) are high-quality freshwater fish. They are not only excellent species for pond culture but also suitable for stocking in large water bodies, where their tendency to readily form natural populations can be used to achieve resource protection and enhancement. The techniques for large-scale rearing of bream summer fry are described below:

1. Conditions of the summer fry rearing pond

The summer fry rearing pond requires an abundant water source, unpolluted water quality, and convenient filling and drainage. The area should not be too large, generally 1-3 mu, with a water depth of 1-1.2 m being suitable. The pond must not leak, and the pond bottom should be relatively flat with an appropriate amount of silt.

2. Preparation before stocking

1. Pond clearing and disinfection: Before stocking, drain the water, remove excess silt or weeds, and repair and reinforce the pond embankments to plug leaks. 7-10 days before stocking the fry, fill with water to 5-10 cm, and apply 50-80 kg of quicklime per mu diluted in water and splashed over the pond, while turning the bottom mud so that it mixes evenly with the lime slurry; alternatively, 6-10 kg of bleaching powder can be dissolved in water and splashed over the entire pond to kill wild fish and pathogens.

2. Appropriate fertilization: 4-5 days before the fry are released into the pond, fill the pond with water to 50-60 cm, and the incoming water should preferably be filtered through fine silk gauze to prevent wild fish and other harmful organisms from entering the pond. At the same time, apply 100-150 kg of decomposed human and livestock manure per mu plus an appropriate amount of chemical fertilizer as base fertilizer to cultivate plankton, so that suitable food is available as soon as the fry enter the pond.

3. Water testing and seine netting: One day before releasing the fry, carry out "water testing" to check whether the toxicity of the pond-clearing chemicals in the rearing pond has disappeared. At the same time, use a fine-mesh net to pull through the pond 1-2 times to remove the few frog eggs, small wild fish and harmful organisms that may be present in the pond.

3. Fry stocking

Because bream yolk-sac fry are very delicate, both the transport of the fry and the stocking operation should be done with care. If the fry are purchased from elsewhere, first place the nylon bags containing the fry into the pond water and soak them for 20-30 minutes, and only release the fry when the water temperature inside and outside the bags is basically the same. The stocking density is generally 100,000-150,000 fry per mu, and each pond should be stocked with fry from the same batch. The time of stocking is generally chosen on a sunny morning; if the weather is windy, the fry should be released at the windward side of the pond.

4. Feeding and management

1. Feeding and fertilizing: After the fry are released into the pond, begin splashing soybean milk. First soak soybeans in water for 5-6 hours, then use a grinder to grind 1 kg of dry soybeans into 15-20 kg of soybean milk, and the ground soybean milk should be splashed promptly. Use 2-3 kg of dry soybeans per mu of water surface per day, splashed in two applications, morning and afternoon. The soybean milk should be splashed evenly around the pond edges in a mist-like form into the water, and at the same time, according to the pond water quality, apply fermented human and livestock manure once every 3-5 days. In the later stage of rearing, when the bream fry reach 2 cm in size, gradually reduce the amount of soybean milk fed and increase the feeding of concentrated feed (such as wheat middlings, fine rice bran, etc.), generally feeding concentrated feed twice a day at 1-1.5 kg per mu, to ensure the fry have sufficient nutritional requirements, promote their rapid growth and strengthen their constitution. However, whether feeding or fertilizing, the amounts should be flexibly increased or decreased according to weather conditions, that is, on cloudy and rainy days or in muggy weather, the feeding amount should be appropriately reduced.

2. Regulating water quality: When the fry have just been released into the pond, the water level is controlled at 50-60 cm. As the fry grow, continuously raise the water level, generally filling with water once every 3-5 days. The amount of water added mainly depends on the fertility of the water, that is, when the water is lean, fertilize more and add less water; if the water is relatively fertile, add more water, gradually raising the water level to the maximum, and always maintain moderate fertility in the pond water, with transparency of about 25-30 cm, ensuring the water quality is "fertile, lively and refreshing".

3. Strengthening disease prevention: Persist in inspecting the pond twice a day, morning and evening, carefully observing the activities of the fry and changes in water quality, to avoid the occurrence of floating head and oxygen deficiency. By controlling the amount of fertilizer and feed and regulating water quality, prevent deterioration of water quality caused by sudden weather changes or excessive fertilization, and prevent the occurrence of common diseases such as gas bubble disease and running horse disease. In the later stage of rearing, if the water quality becomes aged, in addition to timely water addition, quicklime can also be splashed to improve water quality. In addition, during the daily pond inspections, if harmful organisms such as frog eggs and water snakes and foreign matter are found on the water surface, they should be removed promptly.

5. Seine netting exercise

After 25-30 days of rearing, bream fry generally reach a size of 3 cm, and at this time they should be taken out of the pond promptly. Because bream summer fry are good at jumping, are excitable and easily stick to the net, a slight carelessness in the pond removal operation often causes injury and affects the survival rate of pond removal. Therefore, in addition to paying attention to feeding sufficient feed in the later stage of rearing to strengthen the constitution of the bream summer fry, it is also necessary to carry out essential seine netting exercise before pond removal. The seine netting exercise should be carried out on a sunny morning, once a day or every other day. On the first seine netting, gather the fry slightly and then release them back to the original place, or use an adult fish net with wide mesh to pull back and forth in the pond twice. From the second seine netting exercise onward, the bream summer fry can be gathered in the seine net or moved into a long net cage to be crowded, and the length of crowding time depends on the tolerance of the fish, but the seine netting operation must be done very carefully, trying not to let the fish stick to the net or leave the water. After 3-4 seine netting exercises in this way, the fry's ability to resist oxygen deficiency and tolerate crowding is strengthened. If long-distance transport is intended, it is best to also move the summer fry into a net cage in clear water for 3-5 hours of "hanging cage" to discharge feces and excess mucus, thereby increasing the survival rate of pond removal and transport.