Mastering life habits and learning seedling cultivation techniques of large silverfish

Big silverfish

Silverfish is one of the most valuable aquatic products in China, known as the treasures on the table, and has long been well-known at home and abroad, and is a hot spot of aquaculture in recent years. The following is a brief introduction to the techniques of cultivating large silverfish in large water ponds as follows.

I. Life habits

Habitat habits. Silverfish live mostly in the middle and lower layers of the pond and are rarely found in the upper layer except for hypoxia; when disturbed, they drill into the sediment. Juvenile fish have strong phototaxis, which can be induced into groups by light at night, which can be used to check their growth and feeding, but adults have no phototaxis.

Reproductive habits. In ponds, large silverfish can develop to gonadal maturity and lay eggs on their own. The gonadal development and spawning characteristics of large silverfish in pond are basically the same as those of silverfish in natural waters. In the middle and lower reaches of the Yangtze River, the spawning peak is from late December to early January. In hard-bottomed ponds with aquatic plants, spawning is more concentrated, and the fertilization rate can reach 80% to 90%.

Feeding habits. The larvae began to feed on rotifers at 10 days after hatching, and then gradually selected larger and easily available zooplankton as food, in the order of nauplius, copepod larvae, Cladocera and copepod adults. Big silverfish are carnivorous and feed on small fish and shrimp.

II. Pond conditions

The choice of Laokou pond requires fresh water quality, no pollution, shelter from the wind and the sun, and convenient entry and drainage. The area of monoculture pond is 3 mu ~ 4.5 mu, the area of monoculture pond is 4.5 mu ~ 9 mu, the depth of the pond is more than 2 meters, there is an appropriate amount of water and grass around the pond, and the sediment is 0.2 meters thick. Do not mix with carnivorous and omnivorous fish.

III. Preparation for stocking and cultivation of seedlings

Seedling stocking pond. After several times of properly turning the surface sediment in the fertile pond where domestic fish are raised, the water of the pond is poured into the stocking pond after silt removal. Because of the low temperature at the beginning of feeding, the water quality of the pond is difficult to cultivate, especially the low density of rotifers. Using fertile water in domestic fish ponds and inputting resting eggs of rotifers can rapidly increase the bait density in the stocking ponds. This work should be completed two weeks before stocking, and the pool water is 0.6 meters deep before stocking. The source of seedlings. The seedlings needed for the first feeding can be collected from mature parents in natural waters and fertilized eggs can be obtained by artificial fertilization on the spot (fertilized eggs are sold in the fish farm). The fertilized eggs can be hatched in indoor still water. When the water temperature is kept at 4 ℃ ~ 6 ℃, the fertilized eggs will emerge from the membrane in 30 ~ 40 days. The hatching rate is higher and the stocking effect is better. It is of great significance to control the incubation time. When the egg seedlings emerge from the membrane after the end of February, it is easy to get the opening bait, which is beneficial to improve the survival rate of the seedlings.

Stocking methods. The effect of releasing fish eggs in the embryonic stage is better than that of releasing fish fry. One week before hatching, the eggs were put into the pond to hatch, 20,000 fertilized eggs per mu, and 30kg of large silverfish could be caught from September to October. If the amount of stocking is too large, the bait of juvenile fish is insufficient. The water depth of the pool is 1 ~ 1.5 meters.

Cultivate skills. The larvae feed on rotifers and nauplii. After hatching for 10 days, they began to eat, and 3 days after eating, they died without bait. Therefore, the stocking pond should apply enough fertilizer in advance to ensure that there is enough bait when eating. With the application of fully fermented manure and proper application of lime water, after 10 ~ 15 days, the water color became thicker and the rotifer could reach considerable density.

Juvenile fish feed mainly on nauplius, Cladocera, copepod and Chironomus larvae. During this period, fertilizers can be applied frequently, and the amount of fertilizer application can be controlled according to water color and water temperature, so that the transparency of the pool water can reach more than 40 cm and the water depth can be maintained at 2 meters.

IV. Adult fish culture

Provide plenty of bait. During the adult period (more than 40 mm in length), the food intake is large and the growth is significantly speeded up. Frequent fertilization must be applied to maintain the density of plankton, apply rotten fermentative fertilizer, or sprinkle a small amount of soybean milk (250 ~ 500 grams per mu per day). Flexibly according to the water quality.

Pay attention to the conversion of eating habits. The feeding habits of large silverfish have a transformation period, which gradually changes from feeding Cladocera and copepod to carnivorous. When fish and shrimp are found in the intestines of silverfish with a body length of nearly 80 mm, it shows that the feeding habits are transforming, and small fish and shrimp should be introduced in time and maintain a certain density, which can greatly promote the growth rate of large silverfish. An appropriate amount of egg-holding green shrimp was introduced into the Yangtze River basin in May, and the hatched seed shrimp coincided with the feeding period of the big silverfish.

Be on guard against floating heads. The demand for dissolved oxygen of large silverfish is higher than that of ordinary fish, and the floating head is always the first in mixed culture. When the water temperature is 20 ℃, the floating head will appear. If first aid measures are not taken immediately, a large number of deaths will occur. The way to prevent floating head is to reduce the amount of fertilizer so as not to make the bait organisms reproduce excessively. If the water is too fertile, replace the fresh water as soon as possible and use an aerator or oxygenator to increase oxygen if necessary.

V. preventing the harm of high temperature

In the high temperature season, the depth of the pool should be more than 2.5 meters, and shading measures should be adopted if necessary to prevent the harm of high temperature.