The super cold wave, known as the "super cold wave" or even the "overlord cold wave", hit Guangdong, bringing snowfall that has not been seen in south China for many years, and its cold level is similar to the super cold wave in 1991 and 2008. It is reported that before and after the Spring Festival this year, there were four low-temperature rainy weather processes: January 21-26 (cold wave), February 6-8 (weak), February 16-19 (moderately weak), February 26-March 1 (moderately weak).
The cold wave has led to a sharp drop in water temperatures, and some farmers' tilapia and mud carp have even begun to die, because warm water fish are not tolerant of low temperatures. The cold-tolerant Oni tilapia has a low temperature tolerance limit of 8 °C-9 °C, the Gflo tilapia has a low temperature tolerance limit of 11 °C-12 °C, and the low temperature tolerance limit of mud carp is 7 °C. According to the monitoring of the Panyu Seagull Island Breeding Base of Haida Group at 12:00 noon on January 26, the surface water temperature of the pond has dropped to 9 °C, and the bottom water temperature is only 9.5-10 °C (2 m). Then, the cold wave is coming, the water temperature is close to the limit temperature of tilapia, mud carp, etc., in addition to being frozen to death, what will be the way for warm water fish to die?
1. Frozen death. For example, when the water temperature drops to the lower limit of the survival temperature of tilapia, for many consecutive days (5-7 days) low temperature freezing below 7-8 ° C and it is rainy weather, and the sun is not seen all day, a large number of frozen tilapia will be frozen.
2. Death from hypoxia. Mainly because the organic matter at the bottom of the pond consumes more oxygen, coupled with the sharp cooling caused by the pan-bottom, resulting in the lack of oxygen floating heads of fish, and finally died of hypoxia or freezing.
3. Death from illness. When the water temperature drops to the lower limit of the limit temperature (2-5 days), the tilapia will not freeze to death immediately, but its activity is slow, the tilapia due to frostbite, insufficient nutrients, etc. causes a decrease in immunity, susceptible to insect infestation and disease and death, the most common is water mold, and often occurs in the heating process after cooling.
Therefore, when the cold wave strikes, corresponding preventive and treatment measures need to be taken for the above situations:
1. Increase the water temperature. Build a winter shed, stand the windshield wall, pump deep well water (pay attention not to flush the bottom), while paying attention to the cultivation of algae to warm up, winter fertilizer water is recommended to use Hailianke 105 + algae cultivation paste.
2. Change the bottom to increase oxygenation. Use Hailianke 202 or Dipecon to modify the bottom, prophylactically 1-2 times a month; use Hailianke 202 or granular oxygen for oxygenation on the night before or in the evening.
3. Disinfection and sterilization. Fish are prone to water mold disease after frostbite, and it is recommended to use HJCC chlorine dioxide or povidone iodine for water disinfection after each cold wave, and use thiosefloxacin, salicylic acid or pentaskinete for fungal disease prevention.
Finally, pay attention to the cautious opening of the aerator in winter. In particular, during the cooling process, the opening of the oxygenator accelerates the decrease in the water temperature of the bottom layer, and at the same time, the stirring of the bottom will lead to an increase in oxygen consumption. The aerator can only be turned on continuously when the water temperature is similar to the temperature, and the aerator can be turned on in an emergency when the fish lacks oxygen floating head.