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The shape of the gingiva nursery pond is the best. When the definitive is the round cement pond with a volume of 20-60m3 and a depth of about 1m, it has the advantages of circulating water, easy management and large amount of seedlings. However, in practice, based on considerations such as construction costs, people often build pools into square, octagonal, or elliptical pools with a small footprint. In addition, in order to reduce investment, make full use of the existing facilities, such as the true oysters and other swimming fish or shrimp breeding ponds and other slightly modified can also be used for gingival seed production. In general, the existing fish and shrimp breeding ponds are relatively deep, more than 1.5m, which is not conducive to the direct cultivation of the juvenile juveniles, but can be solved by the method of hanging cages in the pool.
For broodstock, the sexual maturation age of gingiva females in the natural sea area is 3-4 years, and that of males is 2-3 years. Male and female broodstock cultured by artificial breeding can reach sexual maturity one year in advance. Taking into account the broodstock oviposition and egg quality and other factors, the male and female broodstock are more than 3 years old, body length natural fish 47-80cm, cultured fish 30-68cm, weight natural fish 1.6-7.0kg, cultured fish 0.9-5.1kg as well .
When selecting natural fish as broodstock, fish caught with fishing gear such as bottom trawls, hooks, and gillnets are not suitable because they are more likely to be damaged, while fish caught with set nets have less damage and are more appropriate. Avoid fish that breaks the skin when picking.
Gnats are not difficult to identify males and females during spawning. In the spawning period, it can be identified by squeezing the abdomen and observing the genital hole. The gonads are red and round are female, slender but not red are male. When broodstock are selected for natural fish or cultured as broodstock, they must be stocked and intensively cultivated to promote gonad maturation. Storage is generally carried out in indoor circular concrete pools, and the bottom area is preferably 30-50 m2, which is convenient for operation and management. The pool is 1.5m deep and the water depth is 1-1.2m. The pool is covered with a black net to prevent the fish from jumping out of the pool and to control the light, prevent the algae from multiplying and keep the fish quiet.
The broodstock has a stocking density of 1-2 and a body weight of 5-15 kg/m2. During the period of stocking, bait species such as sardines, squid, and eel, etc. are mainly used, and the daily feeding amount is controlled at 1-3% of the fish's body weight, and it is fed twice daily. When feeding, small fish can be fed whole, large ones should be cut into small pieces or crushed and fed. Natural fish are difficult to adapt to when they first enter the pool, and some fish do not even feed on them and become hungry until they die. Therefore, it is necessary to take running water so that the bait can slowly move or the artificial bait swings, etc., to induce food to feed as soon as possible.
Sand filter seawater is used during storage. The water change rate is preferably 5-12 times per day. Feeding water temperature is preferably 8-25 °C.
Spawning and egg harvesting are batch mature and spawning fish. The breeding season is from mid-May to mid-June. And with different water temperature and slightly different. The spawning water temperature is 10°C, and the water temperature during the peak period is 14-16°C. The spawning period in Shandong Jiaozhou Bay is from early May to mid-May.
The amount of spawning of brood female broodstock was larger, and the greater the weight was, the more the amount of spawning was. The average number of spawning of 3-9 instar broodstock was 2.2 million. Gnats spawn more often at night. After spawning, it was found that in the evening, a small sink was placed outside the overflow port of the broodstock pool, a sieve basket was built in the sink, and the pond was continuously filled with water. The resulting eggs overflowed the water and flowed into the sieve baskets. Collect eggs. 5-7 days after spawning is the fertile period with high fertilization rate and hatching rate.
The fertilized egg is floating in normal seawater. The collected eggs can be left in a small water tank for 10 minutes to remove the bad egg from the bottom and can be used for hatching. The number of zygote eggs in the gums ranged from 1,300 to 1,600. When the amount of spawning broodstock is insufficient, the sexually mature broodstock can be directly caught at sea during the breeding season, and artificially inseminated and artificially fertilized to obtain fertilized eggs. When picking eggs and brooding fish at sea, special attention must be paid to the females. The abdomen is enlarged and uplifted and soft, and the extruded eggs are spherical and separated from each other. The crystal clear and transparent feeling is good. Artificial insemination can be performed with dry or warm insemination. Timings should be avoided in direct sunlight. Before harvesting eggs, collect the excess water on the progeny and gently dry the egg and semen into a clean container. Then add the semen to the egg container and mix it with sea water (dry method). ) Or add seawater and then eggs, semen mix (wet). Seawater should be added to the egg until it can float evenly. After standing for 10 minutes, the eggs were poured into a sieve basket. The clean selenium was used to rinse the excess semen and the mucus brought by the eggs, and the fish could be weighed for transportation and incubation.
The transport of fertilized eggs can be transported in a plastic bag with oxygen. Add 60-70% of seawater (about 15 liters) into a 5070cm plastic bag, and lay 200,000 to 300,000 eggs, then seal with oxygen and transport.
The transport water temperature is preferably 10-17°C, avoid direct sunlight. The eggs collected on the day were transported for 15-20 hours and had no significant impact on the hatching rate. Hatching eggs can be hatched using static water hatching. The oviposition density was 10,000 FO/FONT> 50,000 granules/m3, and the highest was 150,000 granules/m3. In order to regulate water quality and sunlight, Chlorella vulgaris liquid may be added to the pool so that the water concentration in the hatchery reaches 20?/FONT> 50 000/ml. During the incubation period, it should be inflated. When the dead eggs and dirt are regularly removed every day, the gas should be stopped to allow the dirt and dead eggs to sink so that they can be removed.
The egg hatching water temperature is 7-27 °C, more suitable water temperature 13-19 °C, the most suitable for the 14-17 °C, more than 22 °C or lower than 11 °C, the hatching rate is low, hatching larvae more deformed.
Fry cultivation 1 fry rearing. Refers to the cultivation and management of the newly hatched larvae to the bottoming stage. The average time is about 1 month. The pre-fish fry cultivation density should not exceed 70,000 - 90,000/m3, and the water depth should be about 1m. The newly hatched larvae are usually 4-5 days old and they start feeding, so they start feeding on the 5th day. The larvae of the larvae of the larvae are the best for the larvae of the larvae. With the growth and development, the rotifers are gradually lacking. Only rotifers and Artemia nauplii bait can also be cultivated to metamorphosis.
In the early stage of nursery, the water can be cultivated by static water micro-breathing. Every day, the sewage is regularly sucked and fresh seawater is added. In the first 10 days, the water can be changed by 30% to 100% per day. In the later stage, microfluidic water can be used for cultivation. The daily exchange is 100-300%. The high density cultivation At the same time, water should be transferred early and the amount of water changed should be increased. How much water flow should be taken into account the fry's swimming ability, loss of feed, water temperature and water quality conditions to determine the control of water temperature at 18-20 °C, PH in 7.8-8.4, dissolved oxygen in the 5ml / l or more.
Early water should pay attention to avoid rushing larvae to the drainage network. Inflatable early control of micro-inflating, with the growth of larvae, can increase the amount of aeration. Gingiva larvae require a certain amount of light for feeding and growth metamorphosis. The minimum light intensity that can be eaten is 18-25 lux, and it is usually controlled at 500-2000 lux during the day. In addition to the addition of Chlorella vulgaris at the time of hatching, the Chlorella vulgaris liquid is often added within the first 20 days of cultivation to maintain the Chlorella vulgaris density at 20-50 million cells/ml to improve the survival rate and growth. Has a catalytic effect. The pre-cultivation survival rate is 50-70%.
2 late seedlings cultivation. Refers to the cultivation from the bottom to the full length of 50mm. In the later period, it is advisable to develop a circular or rectangular concrete pool with a depth of 50m3 and a depth of 1m. There are two kinds of cultivation methods: one is to let the metamorphosed juvenile fish sink directly to the bottom of the pool for cultivation, which is called “direct cultivation methodâ€; the other is to transfer juvenile fish that are metamorphic to the bottom of the tank and make it metamorphose. At the end of the net, the method of cultivation is called "cage breeding method." Both methods have their own advantages and disadvantages. The former is easy to accumulate and it takes time to go out of the tank, but it avoids shocks and surprises to the fry in the process of moving into the cage. The latter residual bait is easy to remove, and the yield and survival rate per unit area are high, but it is necessary to change the net and wash the net frequently.
The stocking density is approximately 10,000/m2 at the end of the grounding, and the density should be gradually reduced with the growth. When the stocking density is 30mm, it can be 1000-8000 tails/m2. The late cultivation of bait is mainly Artemia nauplii Artemia and minced meat. The late incubation water temperature is controlled at 18-25 °C. Daily change of water can be controlled at 300-400%. When the water pollution and residual bait are too much, the residual bait should be promptly removed and the amount of water should be increased. In the later cultivation, due to the difference in size between individuals, especially the full length is 20-50mm. At the same time, the phenomenon of mutual susceptibility to food was apt to occur. Therefore, in order to increase the survival rate, sorting should be carried out in a timely manner. The first method of sorting was to observe the selection by naked eyes one by one, and the second was to use a suitable mesh net box for sorting. Specifications kept in separate ponds. At the same time, high-density cultivation should be avoided, and the amount and frequency of feeding should be increased appropriately. Gingival fry fish rearing 30 days, 60 days after hatching, the full length of 19.0-47.9mm, an average of 30mm, when the emergence density of 1100-7500 tail / m2, an average of 4000 / m2. The survival rate in the later period is about 50%. After 50 days of incubation, 80 days after hatching, the total length of the fry is 50mm, which can be used for growing.
Disease and control of seedling stage 1 Pathogen of white turbidity in the intestine: According to Japanese data, it is caused by solitary bacteria. Illness: The larvae are opaque in the intestine and do not feed. Cluster on one side or pool corner of nursery pond. Swimming is not lively. With the development of the disease, the fish’s intestines have shrunk and the abdomen has finally sunk.
Epidemiology: This disease is seen in the period of gingival gingival, first reported by Japan. In May 1983, when the Yellow Sea conducted indoor gingival rearing in Jiaonan County, the disease was also seen in artificially hatched gingival fish fry for 18 days. Preventive measures: Keep the cultivated water environment clean, control the reasonable density to prevent the disease, and feed high quality food. In Japan, the rotifers cultured by lipid yeast and chlorella are used to feed fry.
2 abdominal distension disease The disease symptoms and preventive measures see real breeding seedlings bloating disease.
3 Edward's disease The disease symptoms and control measures see true Edwards disease.
4 Etiology of albinism: The body color and markings of gingiva are formed by a combination of melanocytes, red pigment cells, or yellow and white pigment cells. The normal body color development occurs in the process of metamorphosis. The ocular side skin and pigment cells begin to differentiate first, and when the metamorphosis ends, the body color appears rapidly, but the differentiation of the pigment cells of the non-ocular side is inhibited and there is no change. However, in the metaphase of the metamorphosis, white pigmentation occurs due to the inhibition of differentiation of pigment cells on the side of the eye due to the effects of some other factors.
Prevention:
1) A large amount of natural plankton is fed to the larvae at the full length of 7-10mm, which is an effective method to control albinism;
2) The selection of excellent Artemia fed can reduce the rate of bleaching.
5 etiology of atrial thrombosis: thrombosis accounts for most of the atrial chamber, visible in its internal hemolymph soluble phase, severe fiber visible precipitation, causing atrial thrombus caused by myocardial degeneration and necrosis. In addition, systemic blood stasis and anemia caused by blood clots are visible to the naked eye.
Symptoms: Ascites fish has ascites, retention, abdominal swelling, anal anaemia, anal expansion red, visceral anatomy visible liver congestion and intestinal redness. There is currently no effective treatment for the disease.
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Gingival Seedling Technology
Facility Conditions The facilities required for the development of gums are similar to those for conventional fish seedlings, where the required facility conditions and water quality requirements are particularly important. The nursery's water supply system consists of pumps, pipes, storage tanks, and quick sand filters or sand filters. Due to the large amount of water used for nursery and aquaculture, many domestic manufacturers currently directly use the “day-valve filter tank†that is commonly used in tap water plants that have a large filtering function to automatically recoil, and filter and culture water.