Crayfish pen culture technology

Crayfish pen culture technology

Fence culture of crayfish is a kind of ecological culture of crayfish using large water surfaces, similar to river crab pen culture.

1. Conditions of aquaculture waters

(1) Generally speaking, fence culture is carried out on the large water surface, the water quality of the large water surface is relatively excellent, and the crayfish fence culture requires fresh and excellent water quality, and the transparency is above 50 cm.

(2) Aquaculture waters are generally selected in flat prototype nutrient-rich lakes, with a water depth of between 1 and 4 meters. The water depth of the water used for pen culture of crayfish is preferably within 1-2 meters, because the crayfish are crawling in the water, the water is too deep, and the water pressure is large, which will adversely affect the growth of crayfish.

(3) Although aquatic grass is not so important for crayfish in river crab farming, the importance of aquatic grass for crayfish farming is also obvious, most of the roots, stems, leaves and fruits of aquatic grass can be directly used by crayfish, supplement the lack of bait, increase the intake of vitamins, and can also become a refuge for crayfish to inhabit and avoid predators, and the safety of crayfish molting in aquatic grass is much higher than that in the area of anhydrous grass. Therefore, it is required that aquatic grasses grow luxuriantly and have complete varieties, and the general growing season aquatic weeds are sufficiently supplied, and the coverage rate is more than 40%. However, aquatic weeds should not grow continuously, and there should be enough space between aquatic weeds for crayfish to move freely.

(4) The water source is sufficient, the water level is stable, and there is no major change in the water level due to seasonal changes, and there is no impact of flash floods and large flood impacts. No sewage or runoff water from farmland enters.

(5) The surrounding environment of breeding is quiet, and no large noise is equal to disturbing production, affecting the shell of crayfish.

(6) The substrate is preferably loam or sandy loam, and there is less silt. Generally, the thickness of the silt is within 30 cm.

(7) Convenient transportation, away from national highways, provincial highways, high-speed rail and other traffic arteries with many vehicles, away from the main channel, reduce the impact of vehicle and ship noise on crayfish.

(8) Fence breeding generally adopts the form of aquaculture is ecological breeding, and exogenous bait is fed less, or even not cast, so it is required that the supply of self-sourced bait is sufficient.

Crayfish pen culture on the water requirements are not as high as the river crab pen culture requirements, breeding waters can choose to be close to the nearshore, even tidal flats, swamps can be, in general, the better the water conditions, the better the breeding effect.

Second, the preparation of breeding conditions

1． Netting preparation

Determine the size of the net according to the size of the selected water area, and calculate the number of nets purchased, the number of bamboo poles, and the number of cobblestone mesh bags for the foot press.

2． Identification of aquaculture waters

The aquaculture waters are determined according to the conditions of the aquaculture waters.

3． Erect a barrier net

The erection of the net is generally based on bamboo pole erection, which is cheaper than other materials, convenient to transport, rich in resources, and can be reused. The fence is made of polyethylene mesh cloth, 50 cm above the water surface, and the upper edge is inlaid with 20 to 30 cm of polyethylene plastic film to prevent crayfish from escaping from the top of the fence; the mesh is fixed with bamboo poles, and the lower edge of the mesh adopts two fixing methods: one is to directly insert the mesh into the bottom mud, this way If you encounter strong winds, the mesh inserted into the bottom mud will be lifted, which is easy to cause the escape of the crayfish, so this method is only suitable for waters without strong winds or secluded lakes Another way is to pack the pebbles or stones into a special pillow-shaped mesh bag and then arrange it horizontally to fix it on the lower edge of the mesh. When erecting the net, experienced breeders should be invited to erect, pay attention to the sealing of the bottom, prevent the bottom from hanging, and check one by one after erection, and must not leave any hidden dangers. The treatment of the net foot adopts pebble bagging to press the bottom as well, so that when the wind pulls the bottom net, it can be quickly restored, which can effectively prevent the escape of the crayfish. In some places, anchoring the bottom net with an iron anchor is also a good idea, which is feasible for less windy and wavey waters. However, for larger waters, the wind and waves will directly pull up the iron anchor, so that the bottom net is suspended, giving the crayfish a chance to escape.

4． Netting fence form

Generally require 2-3 layers of purse seine, first with a large mesh of the net to enclose the selected waters, the formation of a safety net, about 5 meters from the safety net to erect the first fence, the fence I erection standard in accordance with the normal fence breeding net enclosure; in the erected purse seine, divided into several small purse seines, each purse area in the range of 30 to 100 acres, in the small purse seine set up a 3-5 acres of temporary purse net. Temporary purse seines must choose waters that have been overgrown with aquatic grass in early spring, and after the crayfish species are transported back, they can be put into the temporary purse seine first, and then loosen the purse seine after the aquatic grass in the water is eaten. Stocking can also be made in the waters between the second and smaller seines.

5． Cleaning of wild trash fish

Conditional can clean up wild trash fish, wild trash fish are mostly omnivorous or prey on small aquatic animals, like to find food under the water or between aquatic plants, not only compete with crayfish, but also cause harm to crayfish when they molt. For large wild trash fish, such as blackfish, the damage to crayfish is greater, and can be removed by hook fishing; for small wild trash fish, net fishing methods or other methods can be used to minimize the number of wild trash fish, and mandarin fish can also be used to kill wild trash fish. Mandarin fish is less harmful to crayfish than other fish, and although it is a ferocious fish, its feeding method is to hide in the grass and make a surprise attack on the fish when it passes in front of it. Crayfish, on the other hand, cannot swim and only crawl underwater or between aquatic weeds, so mandarin fish generally do not harm crayfish.

6． Cultivation of aquatic weeds

Some waters with rare water leather can be planted with aquatic weeds. The planting of aquatic weeds depends on the water depth to determine what aquatic weeds to plant and what methods to take. You can refer to the previous aquatic weed planting method.

7． Implantation of bait organisms

Mainly the input of snails, generally speaking, the number of snails that grow naturally in the aquaculture waters cannot meet the needs of artificial stocking of crayfish for snail farming, and need to be stocked by artificial stocking. Snail stocking is best before March, which not only adapts the snail to its growth environment, but also improves the reproduction rate of snails, which not only increases the number of snails, but also provides a good biological live bait for crayfish, especially small snails.

8． Arrangement of artificial shrimp holes

If the fence is placed near the shore, some artificial shrimp holes can be made on one side of the shore, and it is better if there are small mounds in the fence. If you are far offshore, you should put some tiles, bamboo tubes or cut-out beverage bottles wrapped in black cloth in water.

9． Delivery

Stocking of crayfish is recommended in spring fry stocking mode or autumn female shrimp stocking mode. Spring shrimp fry size 2-3 cm, stocking quantity of 5000 ~ 1000 / mu; autumn female shrimp stocking 8-10, kg / mu. Fish should be selected according to the specific conditions of the water and the number of pairs should be determined. If the water quality is relatively fat, the silver carp and silver carp can be combined more; there are more wild miscellaneous fish, the mandarin fish can be matched more; and some fine scaled oblique-jawed mandarin fish can be used to clean up the solid algae on the mesh to prevent mesh blockage. The general collocation stocking ratio is: 30 carp / mu, specifications 400 ~ 500. Gram/tail; 10 silver carp/mu, size 300~400 g/tail; 50 slender-scaled oblique-jawed carp,100~200 g/tail; mandarin carp 10~15/mu, size 8~10 cm/tail.

10． Other necessary tools

3. Breeding management

1． Feeding and feeding

(1) Aquatic grass planting The breeding waters require 40% of the coverage of aquatic grass, if there is no aquatic grass, you can plant according to the water grass planting method introduced earlier, and the selection of varieties should be based on Elek algae, followed by goldfish algae, rotifer black algae and so on. At the same time as planting aquatic weeds, 200 kg/mu of snails are put in, and 50 kg/mu is added in August.

(2) Exogenous bait feeding If feeding bait, feed with plant bait 2% to 5%, animal bait 2% -3%, the water temperature at feeding should be above 12 ° C.

(3) Feeding method Can be cast or spotted. Throwing is the form of the entire water retreat, but it must also be focused, generally speaking, near the fence, near the water weeds should be sprinkled more, and other locations should be less scattered. Point casting is feeding in a relatively fixed position, and the advantage is that you can observe the eating of crayfish. However, this feeding method is more troublesome, and it is necessary to determine the feeding location with certain references, such as the characteristic water rate. Because crayfish have a more ferocious temperament and often fight with each other for food, they should try to feed as much as possible.

(4) Feeding principle Generally speaking, two heads of fine, medium coarse. When the crayfish just entered the breeding waters, after a winter of hibernation, the physical exertion is relatively large, and after a long-distance transportation bump also consumes a lot of energy, the physique is weak, need to strengthen nutrition, supplement physical fitness, which can improve the survival rate and growth rate of the crayfish; in the summer, the water temperature is higher, the appetite of the crayfish is reduced, the interest in high-protein food is not large, then it should be fed plant-based bait; after the summer, the water temperature begins to decline, the appetite of the crayfish is strengthened, and the refined feed can be the mainstay. It can also promote the growth of crayfish, especially before and after the growth of shells and shells, the most important nutrients, before the shell can be fertilized, improve the growth rate, after the shell, strengthen the feeding of refined feed, can improve the quality of crayfish. However, when the water temperature drops below 12 ° C, the appetite of the crayfish also decreases, and there is no need to feed refined feed, only some plant-based bait. In the whole feeding process, the feeding ratio of the feed has been introduced in the previous table, but these proportions are not set in stone, it is a relative proportion, and in the actual work, it is adjusted according to the specific situation, mainly according to the recent eating situation of crayfish, weather conditions, water temperature, seasonal conditions, and increase and decrease as appropriate.

2． Day-to-day management

(1) Escape prevention is the most important work of fence breeding, if the escape prevention work is not done well, it will make a year of hard work in vain. Crayfish is a very strong sense of escape of the breeding species, in the pen culture, especially the crayfish just entered the pen for the first week, they are always looking for opportunities to escape, after 1 week, the crayfish adapted to the fence environment, relatively speaking, it is better, so in the first week to strengthen the patrol to prevent the crayfish from escaping. In addition, in the aquaculture waters with relatively few aquatic plants, crayfish mainly move around the purse seine, and if there is any damage or a gap in the bottom of the net, the crayfish will achieve a "great escape" through these places, sometimes even all of them. In addition to strict inspection, the solution to escape can also be set up with multi-layered garden nets to prevent crayfish from escaping into the outer waters, and the escape of crayfish can be monitored by placing duck cages in the peripheral waters near the fence.

(2) Clean up debris, residual bait Debris in the fence will not only affect the water quality, but also have an impact on the fence, which should be cleaned up in time. Residual bait has a greater impact on water quality, if there is a residual bait, it should be cleaned up in time to prevent the residual bait from deteriorating and affecting the water quality. Identification of residual bait: The remaining bait after 3-5 hours of feeding can be regarded as residual bait.

(3) Pay attention to the change of water level The change of water level is a problem that should be paid attention to in fence culture, especially the rise of the water level, which will not only trigger the escape of crayfish, but also cause changes in water quality due to the death of some aquatic plants due to the rise of the water level. The problem of water level being too shallow is relatively small, if the place where the purse seine is generally selected has dried up, then it is a drought that has not been encountered for many years, and there is no way to solve it, and the water level that generally drops by tens of centimeters will not have a big impact on crayfish farming.

(4) Maintain good water quality, clean up harmful aquatic weeds in general, the waters for fenced aquaculture are large water surfaces, the water quality is better, but it can not be paralyzed, the more open the water, the more difficult the water quality management, in the daily management, often pay attention to water quality changes, to prevent water quality changes due to industrial wastewater, farmland runoff and domestic wastewater and waters themselves ecological changes. For harmful or dead aquatic weeds, it is necessary to clean up in time to prevent the water quality from deteriorating as a result. If there is a shortage of aquatic plants, some aquatic peanuts can be transplanted to ensure the aquatic grass coverage of the waters.

(5) Maintain the breeding environment, prevent interference The security of the breeding waters is the guarantee of the normal progress of aquaculture production, not only to prevent theft, theft, robbery, but also to prevent noise interference, the impact of noise on crayfish farming is stronger than that of the general breeding object, especially when the crayfish vermicule shell, it will cause the molting shell to stop, causing the death of the crayfish.

(6) The bait of "four certainties" and "four looks" of crayfish should follow the principle of "four certainties" and "four looks" like other aquaculture species, and "four certainties" are timing, quantification, qualitative and fixed points. That is: the feeding time is relatively fixed, so that the crayfish form a conditioned reflex, then automatically to the eating place to eat; the quantitative is in accordance with the previously introduced feeding amount of feeding, in addition, but also according to the crayfish eating characteristics of the adjustment, in general, in the early breeding of crayfish, the use of early and late feeding methods, because the crayfish timid and frightened, like to eat at night, so only 30% of the total amount of a day in the morning, feeding 70% at night; quality refers to ensuring the quality of feed, Do not put spoiled and moldy bait, clean up the residual bait in time; the fixed point is to have a fixed baiting location to ensure that the crayfish can find food in the shortest possible time. "Four looks" is a method of flexibly adjusting the amount of bait and the composition of bait according to the eating conditions, weather conditions, water temperature conditions and seasons of crayfish. Generally speaking, the nutritional requirements and feeding amount of crayfish vary throughout the year, and can be adjusted according to the proportions and bait requirements in the previous table when actually feeding. Under normal circumstances, the amount of food crayfish eats is slightly increased every day, but the physical condition is different every day, especially after illness, it may stop eating, so it should be adjusted according to the situation mastered in daily inspections. Weather changes will also have an impact on the feeding of crayfish, - generally speaking, sunny days have strong feeding power, should be more cast, cloudy days less cast, rainy days do not cast; water temperature is also a factor that determines the amount of bait, low water temperature, less cast, high water temperature should also be less cast, the water temperature is moderate and more thrown, the best bait for crayfish The water temperature is 22-26 ° C.

(7) Diligent pond patrol pond patrol is the daily work in pond aquaculture, its role is to grasp the activities of crayfish, equipment, etc. through inspection, so as to facilitate the timely adjustment of work procedures by breeding managers, which is conducive to crayfish farming.

(8) Disease prevention and treatment The disease prevention and treatment of crayfish should be based on prevention, supplemented by treatment, and combined with prevention and control. In pen culture, the ability to treat is limited, and the diseased crayfish cannot be treated because it has stopped eating, and feeding bait is the only way to treat shrimp surface culture disease. Therefore, in general, in fence culture, special attention should be paid to the germplasm quality and physique of crayfish, as well as the treatment before stocking, and try to select shrimp species with good quality, strong physique and proper treatment for breeding, so as to achieve the purpose of preventing shrimp diseases.

3． Chrysalis period management

The management of molting can be said to be the key to determining the survival rate of crayfish, and the survival rate of crayfish determines the success or failure of crayfish farming, so molting management is the top priority of crayfish farming. In order to do a good job in molting shell management, we should start from the following aspects:

(1) It is forbidden to salvage aquatic weeds during the molting period, because during the moulting period, the puncture of aquatic grasses or other attachments 10 to 30 cm from the water surface is during the moulting period. If you salvage aquatic weeds at this time, you are undoubtedly killing crayfish.

(2) Prohibition of noise The effect of noise on crayfish is well known, and high-intensity noise can make crayfish stop molting and cause death.

(3) Birds are prohibited from entering Due to the good water quality and high transparency of the waters where crayfish are farmed, the vepal shells of crayfish in the water are easily found by birds and become food for birds.

(4) Strengthen nutrition before and after the shell The process of crayfish's shell consumes huge energy, and if the nutrient supplement is not in place after the shell, it will also cause the death of the crayfish.

(5) Sprinkling quicklime water (when the water body is relatively stationary) The sprinkling of quicklime water has two advantages, B is to effectively kill the pathogenic bacteria in the water, to prevent the disease infection of the crayfish in the molting stage; the second is to increase the calcium in the water, which can accelerate the hardening of the crayfish shell and ensure the survival rate of the crayfish.

(6) When the aquatic weed coverage rate is less than 20%, there are too few aquatic weeds such as water peanuts, and the hidden places where crayfish are used to conceal their molting shells are less, which also affects the survival rate of crayfish, in this case, water peanuts, water hyacinths, etc. can be transplanted to increase the coverage of aquatic plants, providing more moulting places for crayfish.

4. Fishing

In the case of autumn female shrimp stocking, individuals that reach market size can be harvested in March-April of the following year, and in May-June if spring shrimp fry stocking is used. Fence culture is harvested in the same way and the principles of fishing are the same as other forms of crayfish culture.

V. Precautions

(1) Germplasm quality High-quality crayfish seed is the basis for obtaining good benefits.

(2) Preparation before stocking Fully prepared, operate in accordance with the operating procedures, prevent the limbs of the crayfish from breaking, and do a good job of disinfection.

(3) Selection of breeding forms Choose breeding and matching forms suitable for local conditions. According to the actual situation, choose spring shrimp fry stocking or autumn female shrimp stocking. Spring shrimp fry stocking generally refers to the large winter wind and waves on the surface of the water surface, and the breeding time is from March to October of each year. In the waters where the wind and waves are not large and do not freeze in winter, you can choose the autumn wall shrimp stocking mode, and you can carry out cross-annual continuous breeding.

(4) Site selection Choose waters with many aquatic plants, abundant bait and no pollution. ，

(5) Water quality management Pay attention to water quality changes in the breeding process.

(6) Aquatic plant planting to ensure the coverage of aquatic weeds.

(7) Release of bait organisms According to the requirements of the release of bait organisms, the release should be sufficient.

(8) Feeding of exogenous bait There are many varieties of exogenous bait supply and sufficient supply. However, it is only a supplement to endogenous bait, and the feeding of exogenous bait should be carried out in accordance with the scientific feeding method to avoid the bait affecting the water quality.

(9) Cochle Shell management The cochle shell management is an important means to ensure the survival rate of crayfish, if the molt problem cannot be solved, there is no good survival rate.

(lo) anti-escape and anti-theft Crayfish have a strong sense of escape, in the pen farming, the important activity area of crayfish is around the purse seine, if there is a place damage, it will trigger a large-scale escape. In addition, anti-theft is also one of the important work, crayfish fishing is simple and convenient, take the cage fishing, the operation time is short, the collection time is shorter, in the fishing season must be taken precautions to prevent the occurrence of poaching.