Analysis of Causes of Overwintering Death in Fingerlings and Overwintering Management Measures
After the Start of Winter, temperatures drop sharply, which is also a test for fish farmers. Fingerlings need to be moved into ponds at the right time for overwintering management to improve their overwintering survival rate. Below is a summary of the causes of overwintering death in fingerlings and management measures, in the hope of helping friends in need. Let's take a look.
I. Causes of Overwintering Death in Fingerlings
1. Hypoxia in the water body
If the pond has not been cleared of silt for many years, excessive silt accumulates on the pond bottom, causing deterioration of pond water quality and increased oxygen consumption, resulting in oxygen deficiency for the fingerlings. If the pond water is too lean, with few plants and weak photosynthesis, the oxygen produced cannot meet the consumption of aquatic organisms, and if fertilizing measures cannot keep up, this also causes oxygen deficiency for the fingerlings. If the pond leaks and new water is not replenished in time, the water level becomes too shallow, leading to oxygen deficiency for the fingerlings. After freezing in winter, if the ice layer is too thick or snow accumulates too much, sunlight cannot penetrate the pond water and photosynthesis cannot occur, thus causing oxygen deficiency for the fingerlings.
2. Harmful substances exceeding standards
After the organic matter deposited on the pond bottom decomposes, it produces ammonia nitrogen, nitrite, hydrogen sulfide and other harmful substances that seriously exceed standards, causing poisoning and death of the fingerlings.
3. Fingerlings of small size
The physique of the fingerlings also affects the overwintering survival rate. Fingerlings with poor physique and little body fat cannot meet the nutritional needs of the overwintering period, which also causes death.
4. Improper handling
In winter, fingerlings have a relatively poor physique. If injuries during netting and pond transfer lead to infection and an increase in disease incidence, this will ultimately cause the death of the fingerlings.
II. Isolation Measures
1. Pond selection
For a pond used for overwintering fingerlings, be sure to choose one close to a water source, sheltered from the wind and facing the sun, with a quiet environment, good water retention, relatively little silt, and a flat bottom.
2. Preparation before stocking
For ponds with a lot of silt, especially old ponds, before stocking, be sure to remove excess silt from the pond bottom, leaving only about 10 cm of silt. After treatment, the pond also needs to be thoroughly cleared with quicklime. Dissolve the lime in water and splash it over the whole pond while hot.
3. Stocking
When stocking, be sure to note that the size should be large rather than small. Under normal circumstances, the stocking size of overwintering fingerlings should reach more than 10 cm. The stocking density should be determined according to pond conditions, fingerling size, and water source and water quality conditions. The stocking time should not be too early. If too early, the water temperature is too high, the fingerlings are relatively active, and they are very easily injured. In addition, before stocking, they need to be soaked in salt water for about 5 minutes to kill pathogenic bacteria and parasites.
4. Feed feeding
During the overwintering period, fingerlings can still feed on clear days, so an appropriate amount of soybean cake should be fed during overwintering. When feeding, try to feed toward deeper water to meet the feeding needs of overwintering fingerlings.
5. Water quality regulation
Generally, water should be added once a week and changed once a month. The added water depth should be 10-20 cm, and the water change volume should be 20%. At the same time, quicklime should be used regularly to regulate water quality and keep the pH value between 7.0-8.5. Turn on aeration equipment in a timely manner to ensure sufficient oxygen supply.
The above is an introduction to the causes of overwintering death in fingerlings and management measures. We hope it can help you. To learn more related knowledge, please follow us.