Gingival Seedling Technology Overview
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English name: Pacific fluke
Common name: tooth chip, partial work, flounder
Scientific name: Paralichthys olivaceus (Temminck et Schlegel)
Facilities conditions
The facilities required for gingival rearing are similar to those for conventional fish seedlings, and 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.
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.
Broodstock selection
In the natural sea area, the sexually mature females of gingiva females are 3-4 years old and males are 2-3 years old. Male and female broodstock that are farmed 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.
The stocking of broodstock
When selecting natural fish or breeding as broodstock, they need to 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 picking eggs
The gums are mature in batches and spawn several times. 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.
incubation
Egg hatching can be done with still 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.