The river crab has a long history of breeding in China, and it is also known as "Shuipin, soup and delicacies". Compared with other freshwater aquaculture species, the market is good and the profit margin is large, so the aquaculture area is also increasing year by year. But the proportion of real money making every year is very small, so the risk is also high. What are the factors that limit the success rate of crab breeding?
First, the quality of seedlings
It is well known that the quality of river crab seedlings is getting worse in recent years, resulting in uncontrollable seedling density and low survival rate. The poor quality of river crab seedlings mainly manifests as follows: 1. The quality of the parents is degraded; 2. The technique of lagging crab farming is backward, the water exchange conditions are poor, and the aging problem of ponds is not solved; only the yield is emphasized, and the quality is neglected; 3. The lack of nutrition is due to the prevention of premature puberty. (More old man crabs), low protein feed selection and insufficient quantities. It is suggested that everybody should choose self-breeding as much as possible, "your own children, bring their own."
Second, over-reliance on aquatic plants
Since crab farming has always been based on the quality of aquatic plants to determine the success of the culture, so most of the energy spent on the entire farming process was used on aquatic plants, ignoring the growth of crabs. For example, in order to reduce the water level in the early stages of long grass, the average water depth is only about 50 cm or even lower. This will lead to large changes in water temperature, waterlogging, long moss, and even serious ammonia nitrogen and nitrite exceeding the standard. Crabs grow. In the mid-aquaculture period, the ponds around the ditch were planted in paddy fields for paddy grass and black-green algae in Putian. It was not until the end of June or even July that the nets were removed and the crabs were put on the fields, so that crabs lived more than half of their time in the breeding process. In the ditch that occupies one-third of the entire pond area, the ditch is narrow, and the water body is poor in fluidity, which can easily lead to hypoxia. So every year from January to May and June, the phenomenon of blisters, turfgrasses, and dark anoxic performances are reflected most vividly. However, most farmers’ friends do not realize that the above problems are the result of oxygen deficiency in the ditch, but believe that insects are Wild fish chuddles or believes that snails have been reduced, and mistakes have been made by selecting insecticides, killing fish, and putting a large number of snails on them, resulting in a more prominent phenomenon of lack of oxygen, blisters, grasses, and crabs. stimulate.
During the middle and late breeding period, when the temperature is high, it is the time when the aquatic plants are needed most. However, there are many breeding friends who have not grown up due to the early management of the grass or have suffered from oxygen rot during the high-temperature period, resulting in the situation that there is little or no grass in the later period. At this time, some of the breeding friends feel that the aquatic plants are gone, the crabs are difficult to raise, and they do not focus on increasing oxygen and stabilizing water. Instead, they blindly deal with problems caused by lack of grasses, such as blue-green algae and dinoflagellates. , Crabs suffered a large number of deaths. In fact, in the past few years, there have been many cases where no crabs have been raised in grass. Through these examples, we have found that aquatic plants are not essential for crab farming as long as they address the issue of hypoxia.
Here is a case study for you: In 2015, there were a boss and two ponds in Zhujiabang District, Qinshui District. Among them, there was an 8-mu small pond that had no grass in July, and the whole pond was cyanobacteria. Wang boss did not kill cyanobacteria and did not give up. Instead, he often chose to change the bottom, detoxify, and transfer water. Results When the crabs were on the market, the output was 200 kilos/mu and the specifications were not small. A few days ago, he saw the boss Wang. He also said: "I knew there were more crabs, or the water quality would not be so difficult to manage."
The cultivation of aquatic grasses certainly helps a lot in the cultivation of crabs. However, due to pond conditions and water pollution, the conservation of aquatic plants becomes more and more difficult. Therefore, we cannot excessively manage the growth of crabs in order to grow grass. Even though water grass is very important for crabs, it is not the only factor that determines the success of crabs. Therefore, we should rationally view aquatic plants and rationally select grass species and planting methods according to pond conditions.
Third, the general lack of dissolved oxygen
Hypoxia is a common problem in river crab farming. On the one hand, the mode of raising grass and crabs is an oxygen-deficient mode, and the oxygen production efficiency of aquatic plants is low. Most of them go into the air and consume a great deal of oxygen. On the other hand, there are few installations of aerators, most ponds do not have aerators, and only when there is an oxygen deficiency, they rely on some pumps to increase oxygen. In a few areas, aeration machines are installed with a high degree of strength, and the aquaculture efficiency is very optimistic. The reason why crab aquaculture does not pay attention to the installation of aerators is that the earth ponds are cultured and the ponds are large. The factors that limit the pond conditions are relatively large. For example, ponds with good water sources and better water exchange conditions or less silt in the bottom of the pond are relatively less likely to suffer from oxygen deficiency. However, in the past few years, the source of water and ponds have been getting worse, and the hazard of oxygen deficiency has become higher and higher, so the success rate of breeding has become lower and lower. There are also some aquaculture friends who have installed aerators and feel little, which is mainly due to insufficient power. Of course, aerators are not a panacea, even if there are other methods of aerators to keep up with, such as the choice of seed, feed feed and water grass management and so on.
Fourth, nutritional deficiency
The crabs were fed once a day, hunger meal, full meal, and feed utilization rate was low. From the perspective of feed selection, it is difficult to guarantee the quality of chilled fish; grain materials can't be done too well. Otherwise, the price is too high for farmers to accept it. Because crabs are omnivorous animals, there are many kinds of feeds and feed coefficients are difficult to calculate. It is difficult to measure the quality of the feed. From the aquaculture process: First of all, there is a lack of nutrients in the crab-seedling stage, which has been analyzed above. Second, in the stage of decapitating crabs, many people do not feed or just feed some low-protein feeds due to the low temperature. When the temperature rises, the first time the oyster shells begin to gradually begin. In the case of no food intake and insufficient nutrient accumulation for several months, the first time clam shells are prone to clam shells; Many ponds suffer from severe hypoxia, unstable water quality, and the incidence of crabs is relatively high. As a result, farmers are afraid to feed or feed; they end up in the stage of “pressure yellowingâ€, and ponds with poor water quality are more afraid to feed, otherwise they are prone to emerge. death. Due to the above reasons, the lack of nutrition in the crabs causes the crab disease to increase, and the quality of the crabs is not good ("yellow" or "paste" dissatisfaction).
V. Inappropriate ways to deal with problems
Throughout the year's farming, there are many problems at each stage, such as early flooding, excessive levels of ammonia-nitrogen nitrite, unremovable clam shells, large amounts of moss, zooplankton, etc.; medium-sized blisters, dirty grass, Herbs are not long, crab grass, etc.; late hypoxia, enteritis, disease and so on. Many farmers simply saw the problem and did not see the root cause of the problem. For example, we have the most common problem with moss every year. Many people see the moss killing, killing it, and then killing it. As a result, the entire 2/3 stages of farming are turning around the moss rather than analyzing why the moss grows. How to prevent it? A lot of moss grows. Some people also know that controlling moss through fertilizers and waters, but due to improper selection of fertilizers (farm fertilizers, chemical fertilizers, etc.), not only water is not fat, but also contributes to a lot of moss, and even causes ammonia nitrogen and nitrite to be seriously exceeded. There are problems every year, but also on those few, why do we not deal with it? The reason is that we only see the surface of the problem without considering the root cause of the problem. If this problem has been dealt with for a long time, the benefits of crab farming will certainly not be good.
VI. Blind investment costs
Although the overall efficiency of domestic crab breeding is not high, there is a large profit margin for crab breeding, and the maximum profit per mu can be tens of thousands. The amount of profit is directly proportional to the specifications and output, so many breeding friends increase blindly in order to pursue high profits. Feeding and putting on snails to increase output and specifications, they do not know that if water quality and dissolved oxygen are not guaranteed, they will be counterproductive. This will not only waste the cost but also increase the risk of breeding. Many factors in aquaculture are not controllable, and it is not much to invest in and harvest more. The key lies in improving comprehensive management capabilities.
Making money is the ultimate goal of aquaculture friends. Faced with the above limitations of crab farming, the overall situation is artificially controlled. Choose self-breeding to increase the survival rate of seedlings; reasonably select aquatic plants according to the water source and seedling density; rationally layout; avoid the situation of less grass and no grass at the later stage; install aerator to improve the stability of water body, prevent hypoxia and increase oxygen The purpose of increasing production, rational and reasonable feeding, can not only ensure adequate nutrition, but also prevent the pollution of the quality of water quality; breeding problems are mostly prevention, treatment problems and more, and find the most fundamental reason, the correct use of drugs; reasonable A rational approach to aquaculture requires the right amount of effort to avoid blind investment and unnecessary losses.
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