How to carry out the management of three-ported crabs?
1, water quality management. The polyculture crab pool is mainly composed of added water in the early stage, and a small amount of water is changed after the full-scale pond is added. In the middle and later periods, the amount of water is appropriately increased depending on the water quality. Single-nut ponds must constantly change the water to keep the water in the pond fresh. In daily management, it is necessary to pay attention to weather changes and water quality in the pond at any time and adjust the water level accordingly. The water quality standard requires that the transparency of the pool water be maintained at about 30 cm, the salinity should be 8 ‰ 27 ‰ (the optimum salinity for growth of the crab is 10 ‰ 20 ‰), the pH is 7.68.4, and the dissolved oxygen (DO) is 4.5--5.5 mg/L. In the early stage of flooding, 20 mesh sieve nets should be used to avoid large-scale enemy invasion. 2, bait and feeding Feeding time: Because the crabs usually have little activity during the day and come out to feed at night, they should try their best to spend less in the evening and night during the day. Feeding method: Feeding methods currently have two kinds, one is to set the bait station, fixed feed, and the second is to spray the sun over the pool. Regarding the bait station, I thought that it was inappropriate to set up a large number of stations. The purpose was merely to check the feeding situation. Some fields include some experience that the establishment of bait stations is better, at least residual baits can be removed at any time, reducing the chance of water quality deterioration. But the effect is exactly the opposite. The habit of the crab is different from that of other fishes and shrimps, and it has a strong residual food, including its kind, as long as it has space and time. Space refers to the distance between each other or the density of swimming crabs in the environment. Time refers to the time of starvation. If the crabs do not move or move less, there will be a certain gap between them. Under normal circumstances, it will be impossible to pose a threat to their peers. In particular, it is the best way for the crabs that are in the shelling period to allow them to feed locally. And guarantee the supply. So I think that when feeding bait, they should be fed evenly throughout the pool to reduce the killing of the crabs. Feeding quantity: Until now, it is reasonable to say that total feeding, daily feeding, and second feeding are not certain. The bait coefficient of each place is 5, and some 12 are very different. However, I think that we have to deal with two kinds of relationships here. First, we must satisfy the basic growth needs of the crabs and consider their own input costs. Pay attention to the feeding method, time, type of bait, nutrient elements and feeding effect are also effective ways to reduce the bait coefficient and even the production cost. Polyculture of crab ponds, because of its "non-staple food, so the bait coefficient is relatively low. In my estimation, the bait coefficient is best controlled within 8%. Food quality and types: The city’s small scads and shrimps are rich in resources, and they can also meet the growing needs of the crab. However, due to the customary “feed levelâ€, many farming units do not pay attention during the procurement, storage, transportation, stacking, and feeding process. Even degenerate small trash fish are not removed, leaving only one form or process. . Not only is the nutritional value poor, but it is very likely to be brought into the source. This reminds you to pay attention to the fact that the quality and hygiene management of bait is the main component of aquaculture management. Only by paying attention to quality can we meet the nutritional needs of the growth of the crab, thereby enhancing the physical fitness, improving disease prevention and disease resistance, and eliminating disease at the same time. Infection routes. 3, daily management During the incubation period, the pool is regularly patrolled daily to observe changes in water quality, check whether the activity of the swimming crab, clam shells, feeding, etc. are normal, whether or not diseases occur, and whether the facilities are normal. Regular determination of the growth rate of the crab, mainly weight-based, in order to facilitate timely control, adjust the amount of bait and change the variety of bait strain measures. 4, disease prevention In general, no large-scale infectious diseases have yet been found in the culture of portuguese crabs, but they have also occurred from time to time. Especially in aquaculture ponds that have deteriorated at the bottom of the pond, due to biological parasites, various pathological conditions such as abnormal black spots and perforations on the shells (resulting from mutual infections after eating) occur in the shells, the ventral limbs, and even in the ankles. There is no good treatment, mainly prevention, such as by improving the environmental conditions of the aquaculture pond.
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