Crayfish Stocking Time and Stocking Methods: Master Six Points to Achieve High Yield and High Income
Crayfish, also known as red swamp crayfish, red claw crayfish and freshwater crayfish, has become an important economic aquaculture species in China in recent years. So when should it be stocked? How should it be stocked? Here we introduce them one by one. Master these six points to achieve high yield and high income. Crayfish farmers, be sure to read carefully!
1. Pond management before stocking
1. Clear wild fish. When farming crayfish, thoroughly removing the natural enemies of crayfish from the pond is a step that must be done before stocking shrimp fry. Many wild trash fish in crayfish ponds not only greatly consume the limited oxygen in the water body, but also may take in more than half of the feed that is given, which will greatly affect the normal food intake of crayfish, causing crayfish not to grow in size and reducing yield. In addition, wild trash fish have very strong survival ability, and if you are not careful when clearing them, they may soon reproduce in large numbers. Therefore, effectively eliminating wild trash fish in the pond can not only improve feed utilization, but also indirectly increase crayfish yield. Thus, in the process of farming crayfish, whether the wild trash fish in the pond can be thoroughly removed is a detail for farmers to increase crayfish production. After the first shrimp farming season ends, drain the water to remove trash fish. It is best to drain the flat pond area dry (or maintain a water depth of 20 cm to 30 cm); clearing trash in the ring ditch has a more ideal effect.
Control the water source: when filling the crayfish pond with water, use fine gauze silk to make a net sleeve, and put it over the water outlet of the submersible pump hose when water enters. This can effectively trap wild trash fish and fish eggs brought in when pumping water.
Kill fish eggs: March to June each year is the golden time for crayfish growth, and it is also the breeding season for crucian carp and wild trash fish. Only by controlling the normal hatching of fish eggs can crayfish yield be effectively increased. Therefore, farmers can take the following related measures: 1) If fish eggs are found at the pond edge, immediately use drugs (bleaching powder, etc.) and splash them around the pond edge to kill them; 2) Clean up debris on the water surface and weeds at the pond edge; 3) Hang grass bundles on bamboo poles and insert them around the pond for one circle every evening. The grass bundles should be about 1 m from the pond edge and about 30 cm below the water surface line. Take out the grass bundles the next morning to dry and kill the fish eggs attached to them.
Kill with medicated bait: you can mix medicine with loach extruded feed, and after the medicated bait dries, feed it into the crayfish farming pond. This can kill wild trash fish; kill once more after 10 days.
2. Disinfect and dry the pond
After the first season of shrimp-rice co-cropping ends, there are two modes for the second shrimp farming season: one is to keep the original Elodea and continue farming (this mode does not require drying the pond); the other is to drain the water on the flat pond area, disinfect and dry the pond, plant aquatic plants, and then begin farming.
Disinfection and pond drying method for the second mode: 1) After draining the water on the flat area, disinfect with lime; 2) After disinfection, dry the pond, generally for 15 days to 20 days, until the pond cracks.
3. Planting aquatic plants (water lantern-bubble grass)
What is mainly discussed here is the step of replanting water lantern-bubble grass after drying the pond. The part about continuing to maintain the original Elodea for farming will not be elaborated much.
After drying the pond, add new water to about 20 cm to 30 cm (the water level should not be too deep at first, as it will affect the rooting of water lantern-bubble grass), and use organic acids for detoxification (at this time the water lantern-bubble grass is mainly transplanted from other ponds).
Planting methods and precautions for water lantern-bubble grass: 1) The planting method is the same as planting Elodea. Plant 15 jin to 20 jin of water lantern-bubble grass per mu at 4 m × 4 m. The planted aquatic plants should be pressed firmly with mud to prevent them from floating and making rooting difficult. 2) 3 days to 5 days after planting the aquatic plants, promptly use long-grass fertilizer to supplement nutrients and promote rooting and growth. Remember not to apply chemical fertilizer in the middle stage of farming. Applying chemical fertilizer easily causes ammonia nitrogen and nitrite in the pond water to rise, affecting the growth of farmed animals. 3) After planting the aquatic plants, observe the growth of the aquatic plants frequently. Water lantern-bubble grass is easily eaten by insects. Once grass insects are found, promptly do a good job of pest control. 4) As the water lantern-bubble grass grows, slowly add new water, keeping the grass 20 cm below the water surface to prevent high-temperature scorching from affecting the growth of the grass.
2. Stocking time
Wait until the planted water lantern-bubble grass has stably rooted and is growing vigorously (about 20 days to 25 days) before stocking fry. Once the aquatic plants have not stably rooted and their growth is not obvious, if stocking begins, the aquatic plants will gradually wither and even die under the trampling of the shrimp fry. In the high-temperature period, once the second farming season has no aquatic plants, the failure rate of farming is very high.
According to survey statistics, most farmers begin large-scale stocking in mid-June, and in better cases the survival rate is only about 20%. During this period, shrimp fry from intensive ponds begin to be listed in large quantities, so shrimp fry prices fall. When farmers see such a good price situation, they begin to buy fry. June is the peak period for lobster disease, so the survival rate of stocked fry is not high, and even dead shrimp fry can affect the original large-size lobsters in the ring ditch and cause disease, resulting in serious losses for farmers.
The correct stocking time should be chosen after July. After July, the disease period of lobsters has passed. Although shrimp fry prices rise, the survival rate is relatively high.
Lobster fry stocking requires uniform size, complete appendages, no disease or injury, and sufficient stocking at one time. Before stocking, bathe them in 5% salt water for 5 minutes to 10 minutes to kill parasites and pathogenic bacteria. For purchased shrimp seed, because it has been transported long-distance out of water, before entering the pond the seed should be soaked in pond water for 1 minute, lifted and left for 2 minutes to 3 minutes, then soaked again for 1 minute, repeating this 2 times to 3 times, so that the body surface and gill cavity of the seed absorb enough water before stocking, which can increase the survival rate. For stocking broodstock in autumn, around September, stock 500 artificially selected lobster broodstock per mu, with a male-to-female ratio of 3:1.
3. Management during high-temperature period and water quality control
1. The high-temperature period has characteristics such as high temperature, muggy heat, and sudden weather changes. According to these climate characteristics, crayfish farming management should be adjusted accordingly compared with earlier farming. Whether a pond farms 1 season or 2 seasons of crayfish throughout the year, or rice-field shrimp farming, water quality management, stress management and feeding management during the high-temperature farming period are important links in the high-temperature crayfish farming period.
2. Water quality regulation
Deepen the water level in a timely manner to lower the water temperature. Adding water in a timely manner is not only to improve water quality, but also to lower pond water temperature. As the saying goes, “deep water raises big fish.” For crayfish, appropriate water depth can prevent water temperature from rising quickly, and at the same time is beneficial and harmless to the growth of aquatic plants. Usually, during the high-temperature farming period, the water level of the ring ditch in crayfish farming ponds is preferably 1.2 m-1.8 m. When adding water, add a small amount many times, with each addition of 3 cm to 5 cm, preferably not higher than the crayfish burrow entrance.
Control water quality turning black. During the high-temperature period, crayfish farming ponds may have black water quality due to Elodea rot, and may also have black water quality after drugs used to control moss cause the moss to die. After crayfish farming water quality turns black, it can cause crayfish to climb onto grass or shore. Therefore, regular bottom improvement and water fertilization work are very important.
Control water quality becoming thick green. In crayfish farming ponds where aquatic plants do not grow vigorously or have weak vitality, during the high-temperature period organic pollutants often accumulate and cause algae to reproduce excessively, leading to thick green water quality and, in severe cases, outbreaks of blue-green algae. During the high-temperature period, bacterial preparations are the best choice for water regulation. Frequently supplementing bacterial preparations to the pond can not only decompose organic impurities in the water body for algae to absorb, but also decompose aging algae in the water and prevent algae aging.
Prevent bottom mud from turning black. Black bottom mud and acidified bottom substrate are common phenomena in high-temperature crayfish farming. This is related to the accumulation of organic pollutants such as excessive feeding, crayfish excrement, and rotten aquatic plant residues in the bottom mud of the farming water body. To prevent bottom mud from turning black, the recommended measure is to use 8 times to 10 times of “Pond Bottom Peace + Clear Water Detoxification Peace” for three-dimensional bottom improvement and water regulation.