1. The selection of pro-picklings for raising seedlings is to select progenitors for mothers with age, shell integrity, obvious radiation, vigorous growth, no disease, and full gonads. Parents should be selected in advance, male and female by a ratio of 2:1 for breeding, stocking density should be small, management must be serious, so that the mother bell is robust.
2. Examination of sperm and egg maturity The appearance of the gonads of the female shells is bright yellow or light yellow, and the plump surface of the gonads is relatively smooth. The appearance of male gonads is milky white. The surface of gonads is rough and granular. When the gonads mature, eggs that overflow and mature around the genital hole are easily pressed and dispersed in water. Under the microscope, mature eggs are round and uniform in size. It is 50-60 microns. The spermatozoa are milky, and the mature sperm is very active under a microscope under a certain concentration of ammonia seawater.
3, artificial insemination artificial insemination There are two kinds of anatomy and induction. At present, nursery uses more anatomy, the specific operation is as follows:
(1) Absorb sperm and eggs and wash the appearance of the pre-selected pro shells. Cut the adductor muscles with a scalpel and remove the right shell (but not the visceral mass). Cut off the full-filament, mantle, and condyle to expose the gonads. . The body fluid and seawater are wiped off with a sterilized cotton wool, and then the sperm cells are sucked with a pipette. The eggs are placed in a beaker with filtered seawater. (2) The fertilized tank is filled with 2000 ml of filtered seawater before being fertilized. , with a certain concentration of ammonia seawater, and then down the egg fertilization tank (the general volume of the fertilization cylinder is 6000-10000 ml) over 5-10 minutes and then down the male and female 2:1 ratio of semen, fully stirred, so that the egg In combination with fertilization. When the eggs are poured, they are sieved to remove impurities
4, wash eggs
10-15 minutes after the inspection of fertilization effect. When the water temperature is 27-29 degrees Celsius and the specific gravity is 1.017-1.019, the first polar body appears 15-18 minutes after fertilization; 30 minutes after fertilization, the fertilized egg has fallen to the bottom of the cylinder. At this time, it is necessary to change the eggs in time to remove the excess sperm, ammonia, mucus and other wastes, the first change of water in the case of no loss of fertilized eggs, try to drain the water, and then quickly fill the water. Change the water every 30-50 minutes after fertilization, generally change the water and wash eggs 2-3 times. Change the water method: Use the siphon to suck the upper semen of the fertilized cylinder. When the second water change is started, use a sieve to cover the siphon nozzle to prevent the loss of fertilized eggs. Water change is about 2/3.
5. After the larvae are collected and raised, change the water and allow it to stand still. At a temperature of 27-28 degrees Celsius (1.017-1.020), 4-4.5 hours after fertilization, the embryo develops to the original intestine and begins to float on a large scale. When the larvae reach a certain degree, the floating larvae are sucked out with a siphon tube and concentrated in a water tank for raising. For each collection, fresh seawater should be added, and then wait for the second batch of larvae to float and collect them in the holding tank. Acquire faster movements when collecting and prevent shocks. The holding time is usually around the hour, and some are directly cultivated in the nursery pond. Density should be 60-100 per milliliter of water body, and often check the development of larvae
6. Cultivation of Seed Management (1) The stocking in the lower pool of the seedlings shall be maintained for more than ten hours. When the larvae develop to D-shaped larvae, the number of larvae shall be counted and the seedlings shall be cultivated in the lower pool. The cultivating pool must enter about 1/3 of the filtered seawater in advance, and then raise the seedlings to lower the pool according to the stocking density of 1.5-2 per ml.
(2) Add water and change water. When the larvae go into the pool, they must gradually add fresh seawater. The next day, fill the water and fill the water for the third day. Change the water method is to enter or drain the water at the same time, or you can drain the water first. . The time for changing the water should be ended before the morning, and the amount of water changes gradually increases with the development of the larvae, changing 1/3 at the initial stage, changing to 1/2 at the middle and late stage of the shell, and changing more than 3/4 of the stage of metamorphosis. You can use precipitated seawater instead
(3) Feeding When the larvae develop to the D-shaped phase, feeding is started. The amount of feed should be appropriate and must be small and precise. With the growth and development, the amount of bait is gradually increased. The types of bait are Hymenoptera subcordiformis, Zhanjiang fork algae, diatoms, and chlorella. The specific amount of bait is shown in the table. Feed 2 times a day, 8 o'clock in the morning, and one in the afternoon. Surround the siphon mouth during larval rearing to prevent loss of fertilized eggs. The water change amount is about 2/3. Pre-feeding a small amount of yeast liquid can help digestion and promote growth.
(4) During hot oxygenation, the weather is hot, the dissolved oxygen in the water is low, and the larvae have a clustering phenomenon in the still water, which can easily cause partial oxygen deprivation, especially the most vulnerable to hypoxia during the second half of the night and before the dawn. It should be noted that air should be used. The compressor is flushed with oxygen or agitated, and the oxygen is flushed once every half hour or 1 hour for 10-20 minutes each time. This will not only increase the oxygen content of the water, but also the flow of water, larvae, baits in the pool evenly, is conducive to larvae feeding growth.
(5) Other management work should pay attention to changes in water temperature and specific gravity. When the difference is too large, measures must be taken in time to ensure that it is relatively stable. Regularly inspect the larvae's development, growth status, water quality, and predator conditions.
7, there are many types of seedlings with seedlings and seedlings, the use of plastic plates, brown rope, tiles, rubber cloth, plastic string and so on. Regardless of which seedlings are used, the seedlings that are easy to harvest should be immersed, washed, and then sterilized before they are used, and then put into a pool in a string.
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