In winter, when the temperature of the water drops below 10°C, the river crab rarely eats or feeds, crouching in pool ponds or pool bottom caverns, and is dormant or semi-dormant, with little activity. When the temperature of spring rises above 10°C, it will only begin to become active. If crabs are raised from the crab seedlings, or if the crab stocking size is too small, crabs will have to go through winter if they do not meet the market specifications. In winter, due to the bad body of the crabs, the water body is deprived of oxygen, and it is frozen and frozen. If the mismanagement causes an increase in the predators, it will often cause the death of the crabs. To improve the survival rate of crabs in winter. First of all, we should understand the physiochemical and biological characteristics of the wintering waters of crabs and the physiological characteristics of crabs during the wintering period, as well as the internal relations between the two; secondly, analyze the causes of winter crab deaths and strengthen the wintering management of crabs.
1. Overwintering pond requires winter due to drought, all kinds of water areas are in the dry season, the water level drops, and after the ice is sealed, the change of the water level of the non-frozen layer mainly depends on the infiltration loss, and the ice thickness continuously increases with the decrease of the temperature. Therefore, the water level gradually decreases. . In order to maintain a certain level of water, conditional waters should be filled with water 2 to 3 times during the winter period. After water is sealed on the surface of the water, the water temperature is very low, and then affected by the weather and sunlight. Normally, vertical stratification occurs in the water, and the deep layer is generally kept at 4°C. Under normal circumstances, the proportions of several types of gases, such as dissolved oxygen, carbon dioxide, and hydrogen sulfide that are closely related to fish life, are periodically changed during the ice-sealing period. Oxygen gradually decreases or increases, and toxic gases such as carbon dioxide and hydrogen sulfide gradually accumulate (these toxic gases can only accumulate in large quantities during the ice-sealing period). After the ice is closed, the pH of the water gradually decreases from weak alkaline to neutral or slightly acidic. This is due to the gradual increase of carbon dioxide in water. The gas conditions of various water bodies are different. The water bodies with deeper water, less silt, and less organic matter have better gas conditions. The crabs have a good wintering effect. The waters with lighter water and more silt and organic matter have poorer gas conditions and the crabs are wintering. The effect is also poor. The sediment of wintering water has a certain influence on the chemical composition of water, especially after the ice is sealed, the influence of sediment on water quality is even greater. Mainly in the two aspects of the impact on the gas status and pH of water. The decomposition of organic matter in the sediment consumes oxygen, releases carbon dioxide, and also produces hydrogen sulfide, which changes the gas composition in the water and also promotes the decrease of pH. The greater the degree of bottom water siltation, the more carbon dioxide accumulates, and the pH of the water drops faster. The wintering of crabs is more dangerous, and only ponds that have not been silted can be used as a wintering pool for crabs. It can be seen that improving the sediment quality of wintering ponds plays an important role in improving the overwintering effect of crabs. In northern China, where winter is cold, species and numbers of aquatic species are generally reduced. At this time, except for fish and crabs, there are still some aquatic insects in the water; most of the large vascular plants have died; the copepods in zooplankton are still visible; the other species are rare; the phytoplankton thermophilic species, For example, cyanobacteria also die, and some types of adaptation to low temperatures still exist.
The amount of phytoplankton in wintering ponds is usually less than that in summer and autumn, but some ponds have considerable biomass. Common phytoplankton are Chlorella, Chrysophyta, Diatoms and Cryptophyta. These algae except Cryptophyta have strong oxygen production capacity under photosynthesis under ice.
Second, winter management 1. Maintain the water depth. The wintering pool should maintain a water depth of about 1.5 meters. Crabs do not freeze and freeze in deeper waters. It is necessary to constantly check whether there is any leakage in the overwintering pool, and deepen the water level in time according to the drop in water level. Don't let the crab pool dry up for a long time. Otherwise, although hidden in caves or mud, crabs are still exposed to the air, and they will freeze and die. 2. Feed and feed well. Pay close attention to the feeding of crabs before wintering, and appropriately increase animal feed containing high fat and protein, feed them well, and feed them until they stop eating. When the water temperature rises to about 10°C, some cooked corn, corn, etc. are properly fed. 3. Special management. There must be a special person to manage the patrol ponds, where the conditions are different, and the size of the crabs can be maintained in different pools. 4. Maintain water quality. Crabs over the winter pool must be prohibited from washing pesticide contaminants to prevent contamination. Ice ponds should be broken in time to icing, to minimize the risk of boating, fishing, shrimp and other phenomena disturbing crabs, to avoid crabs scurrying around and suffer from freezing and physical exertion.
Metal Basket
Metal Basket
The metal basket including stainless steel basket, galvanized basket, powder coated basket, etc. In general, our baskets be Welded Wire Mesh, weave Stainless Steel Wire Mesh, Perforated Metal sheet and Expanded Metal mesh furthur processing. These wire mesh can be cutting, welded, bending to be basket series.
Using of metal basket : sterilizing of hospital, hotel, family, supermarket, catering, etc.
The advantages of metal basket :
surface smooth
rust-free
corrosion-resistant
non-toxic
sanitary
environmental protection
Metal Basket,Stainless Steel Basket,Drying Basket,Basket Series,Wire Storage Basket
ANPING COUNTY SHANGCHEN WIREMESH PRODUCTS CO.,LTD , https://www.scfiltermesh.com