When the fish species is raised to the late autumn and early winter, the water temperature drops to about 10°C, and the fish have little food intake. The fish should be fed in time so that the fish species can relieve the damage caused by the stress before the icing period and adapt to the new environment in the wintering waters. It is very beneficial to increase the survival rate of overwintering. It is also possible to comprehensively understand the production status of fingerlings in the year and sum up the experience through the fish ponds and to provide reliable and accurate data for the development of fish fingerlings for sale and stocking in the coming spring. Fish ponds and pond work should pay attention to the following points.
1. Clearing ponds and disinfection in wintering ponds
The overwintering pool should have the following conditions. The depth of water should be more than 1.5 meters above sea level. The bottom of the pool should be flat and there should be less silt, and the water should be thinner and thinner. The wintering pond should be adjacent to the water source to provide water for the wintering pond if necessary. There is generally no strict requirement for the area of ​​wintering ponds, as long as fishery operations are convenient.
Before the wintering ponds are stocked, clear ponds must be disinfected. This is one of the measures to increase the survival rate of winter fish species. Should be given enough attention. Clear pond disinfection can be carried out by conventional methods. However, in the busy autumn season, the time is very tight, according to the regular disinfection of the clear pond until the disappearance of fish release at least seven days, in this case, you can use dry pond promptly back to the water when the water level reaches submergence After the bottom of the pool, use bleaching powder (including more than 25% of available chlorine) to disinfect, so that the water is 20~25ppm, the chemical properties of bleaching powder disappear quickly, and after two days, the water can be added and fish can be added. However, it must be remembered that the water block must be set to prevent wild fish and enemy creatures from entering. The water in the wintering pond can use the old water of the original pond when the water source is insufficient, and it is better to use 1/3 of the original pond old water and add 2/3 of the new water.
If the density of fingerlings is not large, when the pond is used for overwintering, water should be used to adjust the water quality with quicklime of 10-15 kg/mu or bleaching powder of 1-1.2 ppm after 3-5 days of feeding. After 1~2 days, the trichlorfon should be spilled once more. . Make up the pool water before closing the ice. You can turn into winter management of fish species.
2. Tongtang time
When the water temperature drops to 8~10°C, the fish species and the wintering work of the pond can begin. According to the climatic conditions in my area, the general fish species and pond time can be started in October or early November. The time of the pond should not be too early, the water temperature is too high earlier, the fish activity ability is high, the oxygen consumption is large, and the fish body is easily injured during the operation. If the pond is too late and the water temperature is too low, especially when the temperature drops to around 0°C, during the operation, it will easily cause frostbite. The skin of the frostbite is necrotic or shedding, and it is easy to infect the hydromycosis after entering the pool, causing fish diseases. It is reported that squid in water below 4°C can cause paralysis, rigidity and imbalance. In the environment of long-term low temperature (below 1°C), the end of the cocoon of the eel swells, causing tissue necrosis. It can be seen that the suitable water temperature for fingerlings and ponds is 4~10°C, and should be selected on sunny days. This will not only reduce the chance of injury to fish but also facilitate the operation.
For tropical fish that are not tolerant to low temperatures, such as tilapia and whitefish, the water temperature should be above 15°C. The water temperature is low and the survival rate of the fish species behind the pond will be greatly reduced.
3. Stocking density of wintering fingerlings
The stocking densities of wintering ponds are related to the effective water depth, leakage, water supply conditions, water quality and management level of ponds. In fact, the size of the stocking density depends on the amount of oxygen produced by phytoplankton in the water and the actual oxygen consumption of the fish pond during the winter. In still water ponds, the source of dissolved oxygen in the water after freezing is mainly dependent on photosynthesis of phytoplankton. The intensity of photosynthesis in phytoplankton is related to the daily production of dissolved oxygen and the composition and quantity of phytoplankton and the light transmittance of ice. Therefore, it is necessary to reasonably determine the stocking density based on the conditions of wintering ponds. The ice-sealing period in our region is about four months or so. In a well-conditioned fish pond, 0.3 to 0.4 kg of fish can be stocked per cubic meter. If the condition of wintering pond is poor, and the management level during wintering is not high, the stocking density is still slightly smaller. We use adult fish ponds with an area of ​​20-30 mu in Baodi County and Tangshan Junyi Farm. The water depth under ice is 1.5-1.8 meters, and the stocking amount of wintering earthworms, oysters, oysters, oysters, and oysters is controlled at about 0.35 kg per cubic meter. For more than a decade, there have been no fatal winter deaths. The average survival rate for wintering was 75.2 to 81.4%.
4. Fish species classification, counting, disinfection, transportation and stocking
The over-wintering of species can provide convenience for the next spring, but it is common to separate winter fish from eating fish. When categorizing, different types and different specifications of fish can be separated by various methods such as rake, sieve, and pick.
The fish species can be counted after being classified. The method is to randomly select 20 fish species from each species and size, and determine the length and weight to determine the length and weight range of the species and their average value; Weigh a certain number of fish species to find their mantissa, and then calculate the tail count for each species and each species based on the total weight of species and species. Then calculate the survival rate of fish species.
Fish must be disinfected before stocking. Fish sterilization before stocking can be used medicinal bath method, a single drug: salt, malachite green, bleach, potassium permanganate and so on. It is recommended that you use the malachite green, furazolidone and Trichlorfon triads introduced to you in March this year. The concentrations are: malachite green 4~5PPM, furazolidone 10~15PPM, trichlorfon 10~15PPM. Medication time 10 to 20 minutes. The method of disinfection of fingerlings can be controlled flexibly. After the number of fish species is over, a separate medicinal bath is provided. If the fish is used for short-distance transportation, the medicine can also be put into the fish gill and the medical bath is disinfected during the transportation operation.
The method of short-distance transport of fish species can be carried out by using a plastic box, or can be carried by using a fishing rod and water. The number of fingerlings shipped may be based on the conditions at the time of stocking. When fish species are stocked, their activities are normal and there is no coma. The transportation water can use well water or pool water, preferably containing high dissolved oxygen and less organic matter. In short, the transportation of fish species should be selected according to the species, water temperature, transportation distance and the conditions of the site. Before fish ponds and ponds, we must plan well and ponder and summarize experience in a timely manner to continuously improve operations.
In addition, fish ponds and ponds should be selected for sunny weather. Do not move the nets or dry ponds during high winds and snow days. In the process of pulling nets, transportation and stocking operations, the movements should be quick, light and steady, and the chance of injury to the fish should be minimized during the entire process of checking the weight, shipping and stocking of the fish species. At the same time, pool water should be added before freezing. To ensure the safety of fish overwintering.
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