Artificial multiplication technique of large silverfish in Hongshan Reservoir

Hongshan Reservoir is located in the lower reaches of the Laoha River in the northeast of Chifeng City. it is a large plain reservoir integrating flood control, irrigation and aquaculture, with a rain collection area of 24500 square kilometers and a total storage capacity of 2.56 billion cubic meters. the reservoir covers an area of 80, 000 mu ~ 130000 mu in dry season-high water season. The fertilized eggs of large silverfish were introduced into the reservoir in 1995, and the fishing yield reached 2.5kg/ mu in 1998, and the yield decreased in the following two years, but in recent years, due to the adoption of more perfect proliferation management measures, the resources have been gradually restored.

I. strict enforcement of the fishing ban system

According to the law of growth and reproduction of large silverfish, the fishing ban system was formulated, and the reservoir administration bureau supervised the implementation of the breeding company. The growth and weight gain period from June to September, the breeding and hatching period from December to February of the following year were taken as the fishing ban period, and the natural spawning and high hatching rate area of the silverfish with gravel 3km substrate in the main dam of the reservoir area was set to permanently forbid fishermen to use net gear and shrimp foil with mesh less than 3cm as fishing gear.

Second, conscientiously do a good job in reproductive monitoring of large silverfish

The spawning period of large silverfish is closely related to the abundance and shortage of food, climatic conditions and water quality every year. At the beginning of December every year, Gill nets are used to catch parent fish in different areas every day to test the maturity rate, and large-scale fishing for artificial fertilization begins when the maturity rate is about 25%. The peak spawning period of large silverfish in Hongshan Reservoir is generally between 10 days and 15 days from December 5 to January 10 next year. The data such as the maturity of parent fish of large silverfish in Hongshan Reservoir were tested on December 13, 2004. the details are shown in the table below. It can be seen from the table that the parent fish of Hongshan reservoir is large, the number of eggs is high, and the egg diameter is moderate. The spawning peak is in the middle of December.

III. Fishing and conservation of parent fish

Mature parents are operated on the ice and captured by a single-layer bottom Gill net. In operation, you must comply with:

1. Set the net in the designated area and control the number of the net, so as to protect the natural spawning area and control the number of parent fish on the Internet.

two。 The mesh should be small, not big, and the time should be short rather than long. In order to ensure that the parent fish are hung on the head rather than the chest and abdomen and remain alive, the maximum mesh size should not exceed 1.5cm and the net time should not exceed 1.5 hours.

3. When setting up the net, the net fish is quickly put into the incubator and transported by motorcycle to the egg collection room, pick one piece when picking the fish, and keep the rest in the incubator with ice at a low temperature.

IV. Artificial insemination

In the case of sufficient parent fish, the selection of parent fish should basically be done when there is food in the intestines, the body is white and hard, and the female-to-male ratio is less than 1 ∶ 2. What we have done over the years is to dry the selected parent fish with dry towels or toilet paper, take the female head over the tail, squeeze the mature eggs into the plastic bag, gently squeeze the eggs in the male hip alignment bag with both hands to make the semen hang the anal fin cloacal hole, stir the sperm and eggs with the male buttocks and put the male fish in the bag. Gently shake the water filtered by 20mL~30mL, then add the filtered water around the 250mL after 2 minutes, tie up the mouth of the bag and move it into the temporary incubator for rinsing and temporary hatching.

5. Temporary hatching of fertilized eggs

Over the years, the temporary hatching tools of fertilized eggs have chosen hard plastic bathtubs with small size, smooth inner wall, easy to move and easy to operate. The fertilized eggs after washing, floating and impurity removal were incubated in the bath according to the order of fertilization time. The temporary hatching density was 2 million eggs per square meter, the indoor temperature was controlled at 3 ℃ ±0.25℃, the water was changed once a day and the basin water was stirred twice to remove impurities, whitening and moldy eggs in time. Pay attention to check the fertilization rate after changing the water every day. Stirring basin water every day during temporary hatching is beneficial for the eggs that stop development to float to the surface and be cleared in time, otherwise it will affect the development of fertilized eggs. Through the detection of fertilization rate, it was found that the fertilization rate of stirred eggs on time was much higher than that of unstirred eggs. A comparative experiment was conducted in December 2004. under the same conditions, the fertilization rate of agitated eggs was 68.4%, while that of unstirred eggs was only 19.2% under the same conditions.

VI. Release of fertilized eggs

According to the water temperature of the reservoir, the water temperature of the temporary incubator should be adjusted to the same level as the reservoir water the day before the fertilized eggs are released. After testing the fertilization rate, the fertilized eggs were packed in plastic bags and transported with ice in an incubator. The spawning site chooses the reservoir bay at the southern end of the dam, where the geology is hard, the water depth is about 3m, no passing motor vehicles, sunny leeward and plankton are rich. The ice hole 50cm is square, and the distance between the ice eyes is not less than 50m. After adjusting the temperature, the release density is 1 million eggs per ice hole, which ensures the playback of 200 million effective eggs every year. In the process of release, the settling speed of eggs is slow, it is necessary to prevent eggs from sticking to the ice wall, and plastic film can be used to protect the ice wall, so the stocking effect is very ideal.