Aquaculture to prevent invisible killers

There have been many large-scale and sudden dead fish phenomena in cage farmers in Yinan County, Chongqing. According to statistics, from late May to mid-August, in 17 villages in the 3 townships of Tongnan County, there were 262.6 tons of dead fish in more than 1,000 cages of more than 150 farmers, and the direct economic losses amounted to more than 250 million yuan. Seeing the dead fish on the surface of the water and a large area of ​​white flowers, farmers are all grieved. They first suspected that it was caused by pollution, so they took samples of water samples, polled the river for pollution, and found the government to solve the problem. Some farmers who were hit hard still wanted to withdraw from cage fish farming. Dealing with the "dead fish incident" for a short time became a hot issue for the central work of the county and township leaders and the people's discussion. However, the environmental protection department's water sampling test results showed that the water was not significantly polluted, and there was no pollutant discharge in the upper reaches of the dead fish river, basically eliminating the possibility of dead fish being contaminated by water in vitro. What caused the fish to die in the end? After field surveys and data analysis by the meteorological and fishery departments, it was agreed that the severe shortage of dissolved oxygen in water is the main reason for the sudden and large-scale death of cage fishes in Junan County. Why is there a serious shortage of dissolved oxygen in the water? The original weather mutation was the culprit. When the air temperature continues to be significantly higher, the water temperature is therefore kept at a higher level. When the sudden cold air intrusion occurs or the sudden drop in temperature, the surface temperature of the water body decreases, but the hysteresis of the water temperature change makes the bottom layer The water temperature is still high, causing the upper and lower water convection, aerobic water sinking, and oxygen-free water rising, which causes the surface water to lack oxygen. At the same time, before the weather changes, the air pressure is maintained at a relatively low level, and the oxygen in the water continuously overflows to dissolve the water. The decrease in oxygen content has become an "invisible killer" of the dead fish incident. Several sudden dead fish incidents occurred during the abrupt changes in the temperature of the sudden drop in air temperature or pressure, which proved this point. Funan County of Chongqing is the ideal water area for cage fish farming. Because of its unique river system, the county government has been piloting the pilot demonstration of cage fish farming in Qingyun Reservoir since 1993, and by 1997 it has achieved cage culture. In scale, the development of the aquaculture industry not only enriched the food baskets of the urban and rural people, but also became a shortcut for peasant people to make a fortune. The booming aquaculture industry has enabled some farmers to realize their dream of becoming rich. In order to rapidly develop the aquaculture industry and increase the survival rate of fish, farmers have stepped up the management of river grass removal, formula feeding, and plugging of pollution sources. However, the phenomenon of dead fish in cages still occurs from time to time. With the adjustment of the agricultural industrial structure and the rural economic structure, freshwater aquaculture has developed rapidly. To avoid or reduce the losses caused by large-scale deaths of cage fish, we must first establish the awareness of scientific breeding, and strictly follow the average 300 mu water surface in flowing waters. Mu cages, 500 acres of stagnant water, 1 mu cages required to set the density of cages; Second, farmers should increase the awareness of the weather, always pay attention to listen, watch the local weather forecast, so that the network can be timely in the sudden weather The box was pulled away from its original position, and the cage was dispersed and oxygen-enriched powder was thrown into the cage. At the moment, although it has entered the winter, temperatures have dropped and there are fewer dead fish. However, if farmers do not strengthen their learning, strengthen scientific awareness, and improve their protection capabilities, they will be helpless in the face of “invisible killers” next year. Therefore, it is important to increase the oxygen in the water body, and it is more important to increase the oxygen in the meteorological science to your head.

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