How Do Fish Survive the Winter? A Detailed Guide to Fish Overwintering Methods

Fish are divided into many kinds, including wild fish, artificially farmed fish, ornamental fish, and so on, and each kind is raised in a different way, so how do fish survive the winter?

1. How do fish survive the winter?

In regions with a warm climate in the south, fish living in the wild do not need to carry out related overwintering activities, while in the colder regions of the north, because the thermal contraction and cold expansion of water causes the lower water layer to have a higher temperature, fish gather there and only come up to the surface to move about when the weather is clear.

When artificially farmed fish are overwintering, it should be ensured that the non-freezing water layer of the overwintering pond is more than 1-1.5 m, and at the same time the pond bottom is required to be flat, with the silt thickness at about 10 cm, because the silt contains a large amount of humus, which, although it can serve to supply fertilizer, retain fertilizer and regulate water quality, in addition, before overwintering the fish must also be disinfected to avoid causing disease. Among these, still-water overwintering is to place the farmed fish in suitable conditions such as ponds and other still small water bodies to overwinter, and it is generally used in areas lacking flowing water conditions. Flow-through overwintering is to use water of suitable temperature and rich in dissolved oxygen to continuously inject into and discharge from the fish overwintering water body by itself, so that the fish can overwinter safely. Cage overwintering is to choose a reservoir or lake with sufficient dissolved oxygen and suitable water temperature to place cages, so that the fish overwinter in cages sunk under the water. Indoor overwintering is to build a plastic film greenhouse or glass greenhouse over the fish pond to keep warm and use sunlight to raise the temperature, so that the fish can overwinter safely.

When tropical ornamental fish raised indoors are overwintering, first the feeding time should be changed, generally feeding at around ten in the morning, when the difference between water temperature and air temperature is relatively small, and the impact on the ornamental fish is also relatively small; second, attention should be paid to changes in water temperature, and when the water temperature is too low a heating rod should be used in time to heat it, creating a good living environment for the ornamental fish.

2. What are the precautions for fish overwintering?

1. Breaking the ice to add oxygen

After the water surface is sealed by ice, the ice surface should be smashed open every morning and evening, generally 8-9 sq m of ice holes should be smashed open per mu, and at the same time, the smashed ice blocks should be fished out, so as to avoid rapid freezing again.

2. Clearing away accumulated snow

During the winter ice-sealed period, if snowy weather occurs, the accumulated snow on the ice surface of the fish pond should be cleared away in time, so that sunlight shines into the fish pond water and the photosynthesis of green plants in the water proceeds normally.

3. Adding and changing new water

During the fish overwintering period, in addition to maintaining the highest water level to increase oxygen and keep warm, new water should also be injected regularly to improve the fish's living environment and increase dissolved oxygen, generally injecting water once every 15 days. If the pond water quality deteriorates and shows signs of aging, the old water and harmful substances in the pond should be discharged in time, with each water change being 1/4 of the original pond water, and then new water should be injected in time.

4. Appropriate fertilizing

When the fish pond water is clear and lean, a certain amount of inorganic fertilizer can be applied at noon on a sunny day, which can both promote the growth and warmth retention of phytoplankton in the water and increase dissolved oxygen in the water through photosynthesis; the fertilizer must contain the two components nitrogen and phosphorus.