Prevent Fish from Catching Cold When Stocking Fish in Autumn

Autumn is the golden season for stocking large numbers of silver carp, grass carp, black carp, bighead carp and other fish species into reservoirs. But many @#@233@#@ farmers have found that, often within 2 to 7 days after stocking, sick and dead fish are seen swimming on the reservoir surface. These sick fish lose their skin luster, their body surface mucus increases, and in severe cases they become paralyzed, rigid and die.

The above symptoms are typical of a "cold," mainly caused by drastic changes in water temperature, in which the nerve endings in the fish skin are strongly stimulated and the internal organs' activities become disordered, with a mortality rate as high as 20% to 60%. Fish species are transported from the fish pond to the reservoir edge and then directly released into the reservoir. Because the water temperature difference between the two places is large, even if the fish appear normal to the naked eye during stocking, after entering the reservoir they will still catch a "cold," fall ill and die. So how can this be controlled?

First, adjust the temperature difference properly. Install net cages in advance in the reservoir bay. When the water temperature of the fish pond differs from the reservoir water temperature by more than 3°C, gradually adjust the temperature difference first, and release the fish into the reservoir after they have adapted. The method is: gradually add reservoir water to the tank transporting the fish. When the water temperature in the transport tank approaches the reservoir water temperature, keep it that way for 10 to 30 minutes, then slowly pour the fish and water together into the net cage, thereby adjusting the water temperature and letting the fish adapt to the new water quality environment. After 2 hours of holding in the net cage, the fish can be allowed to swim freely into the reservoir.

Second, drug prevention. Since reservoir water temperature is often lower than fish pond water temperature, garlic combined with urea can be used to prevent fish from catching a "cold." The effect is very good, and it has no side effects on the fish at all. In every 500 kg of water used to transport fish, add 1.3 kg of garlic pulp. After loading the fish into the tank, wrap 2.5 kg of urea in cotton cloth and sink it to the bottom of the fish tank. As the urea slowly dissolves, it absorbs heat from the water, causing the temporary holding water temperature for the fish to slowly decrease. Once the water temperature approaches the reservoir water temperature, release the fish.