CATDOLL : CATDOLL: How do grouper fry survive the winter?

1. About 30 days before the fish stop eating, conduct a comprehensive inspection of the fish that are planned to overwinter, and improve the fish's resistance to cold and disease through intensive cultivation before overwintering. The bait should be comprehensive and rich in nutrition, with a higher energy-protein ratio than during the feeding period, and vitamin C should be appropriately increased. It is also necessary to add appropriate amounts of betaine, choline chloride, etc. to the bait, which can promote fat metabolism in the fish liver and have a significant effect on preventing the formation of fatty liver.

2. Lack of oxygen in the water is also a major cause of winter death of pond fish. It is necessary to keep the number of phytoplankton and dissolved oxygen in the water of the wintering pond relatively stable, increase the light in the water layer, control the phytoplankton, prevent excessive organic matter, and increase the dissolved oxygen content.

3. Low temperature in the water of the wintering pond is a major cause of large-scale fish deaths during the wintering period. Because farmed fish cannot survive in water temperatures below 0.5℃ for a long time, and fish introduced from warm areas and raised at high density are even less resistant to low temperatures, so in the wintering management of fish, we should try to control and reduce the occurrence of low temperatures as much as possible, especially to prevent mechanical stirring of water from causing a sharp drop in water temperature, and do not let the bottom water temperature drop below 2℃.

4. Intensive ponds generally adopt a high-yield, high-density production method, with a large amount of feed, relatively insufficient water sources, and many ponds have excessive organic matter. Treating the pond water before ice closure can effectively reduce the content of organic matter in the pond water, reduce organic oxygen consumption, and eliminate the dangers of pathogenic bacteria and toxic and harmful substances. After the fish stop eating, according to the local climate, the pond water can be treated before ice closure about a week before ice closure, such as using chlorine-containing disinfectants to spray the entire pond.

5. Fish do not eat for a long time during the winter and their physique is very weak. After the ice melts, as the water temperature rises, various pathogens or their spores, eggs, and larvae in the water gradually develop and multiply in large numbers, making the fish vulnerable to pathogens. Vertical scale disease, Saprolegniasis, and White Cloud disease are very likely to spread, causing a large number of fish deaths. In order to reduce losses, active measures should be taken after the ice melts to prevent the occurrence and spread of fish diseases.