At present, there are two types of artificial seedlings, indoor cement pool and cement ditch circulating water. The main techniques and methods for the various aspects of artificial nursery are briefly described as follows:
First, artificial oxytocin
Selectively matured cockroaches are used for oxytocin production under conditions of cold stimulation, dryness or dehydration. General water stimulation is performed at night and spawning can take place within a few hours. The flow rate is close to the speed of ebbing in the sea area. In artificial oxytocin production, it should be noted that the salinity of seawater in inbreeding areas should be close to that of urine production. When the intimacy begins to spawn, continue to flow.
Second, hatching of fertilized eggs
The hatching of fertilized eggs requires certain ecological conditions. The optimal ecological conditions are temperature 20°C~25°C, pH 7.0-8.5, and the salt suitable range varies with the source of the relatives. The lowest salinity of the fertilized eggs from the low-salt zone is 8 to 12; in the high-salt zone, the minimum salinity is 15 to 30, but the temperature can affect the salinity range.
Third, the plankton larvae culture
• The planktonic larval stage refers to the various stages from the development of the D-type faceplate larvae to the pupa larvae, where they all live in planktonic life. The training conditions for this stage are as follows:
1. The bait for bait plankton larvae includes seaweed, kestrel, trichophyton, trichophyton, green algae, phycoplana, and algal yeasts. In the larval stage, it is preferable to use a size of 5 μm to 7 μm. The density of single-celled algae was 50,000/ml to 100,000/ml. It is generally better to feed mixed bait than single bait.
2. Temperature larvae cultivation temperature range between 17 °C ~ 32 °C, of ​​which the best 25 °C ~ 27 °C. Above 25°C, the larvae grow slowly as the water temperature rises, and the larvae have a very low rate of living above 35°C. The larvae die at about 40°C. When the water temperature is within 25°C, the growth of larvae increases as the water temperature rises, but when the water temperature is below 15°C, the larvae are difficult to grow or metamorphose.
3. Salinity larvae The salt range is very wide, from 4.5 to 30.2 can be cultivated to adhere to metamorphosis, salinity of 12 to 20 is the most suitable. The salinity of the pupa larvae is related to the salinity of the sea in which the larvae grow. The upper limit of suitable salt for the larvae of the indigestible larvae from the high salt sea area is higher, and the larvae of the larvae from the lower salt areas have stronger adaptability to low salt.
4. Dissolved Oxygen Seawater The dissolved oxygen content of more than 3 ml/l is a safe level for larval rearing. If it drops below 3 ml/l, you have to increase the oxygen content using methods such as inflating and changing water.
5. Acidity and alkalinity The adaptation range of larvae to pH is from 6.7 to 8.7, of which 7.6 to 8.5 are more suitable. If the pH is above 9 the seedling cannot be grown.
6. The use of compounds to treat natural seawater to improve the hydration environment has become one of the important means in the nursery process. Experiments show that the use of 1.010-6 EDTA in the growth of larvae has a positive effect on the growth and development of larvae. If it exceeds 1.010-6, although the growth of larvae is promoted, the mortality rate is extremely high and should not be used.
7. Antibiotics In nursery ponds, bacteria and protozoa are multiplying due to larvae's excretion and the deposition and decay of biological carcasses. In order to improve the larval life rate, the bacteria can be mixed with 27,000 units of streptomycin per liter of water and 50,000 units of penicillin G potassium per liter of water in order to inhibit bacterial growth; the ciliates of protozoa are often used as 12510- 6 PVPE liquids.
8. Ultraviolet Disinfection and Filtration Seawater production uses 20-W ultraviolet lamp to sterilize seawater for 20 minutes, or to condense ultraviolet light strings into illuminators. Filtration water flows from one end of the plastic tube and is irradiated by several UV lamps. Outflow from the other end can achieve the purpose of sterilization.
Fourth, juveniles attached to the cultivation Due to benthic camp life, their breeding conditions and plankton larvae have different.
1. Under the conditions of indoor temperature, the optimum temperature range of juveniles is 10°C to 35°C, and the optimum temperature varies with the salinity. If the optimum salinity is 12.4 to 16.3, the optimum water temperature is 27°C to 30°C; if the juveniles are at the optimal salinity, the optimum water temperature is about 22°C. Juveniles have a strong tolerance for low temperatures. The maximum lethal temperature for juveniles is about 40°C. It can be seen that the optimum temperature for juvenile juveniles is constrained by salinity.
2. Salinity juveniles are adapted to a salinity range of 4.5 to 28.3 and an optimal salinity of 12.4 to 16.3. Juveniles have strong tolerance to salinity of 1.8 or less at 25°C, and varying degrees of tolerance to high salinity of 23.5 to 40.0. From the temperature and salt binding experiment, the temperature of 27°C and the salinity of 12.4 are the best levels of binding. In the temperature below 22°C and the optimal salinity range, the correlation between temperature and salinity is less obvious; and above 27°C and the upper and lower limits of the salinity range, the correlation is significant, and their corresponding salinities range. Obviously narrowed. This is very different from the larvae of planktonic larvae. In other words, the larval larvae are more sensitive to temperature, and the bait period is more closely related to salinity.
3. The stomach contents of juveniles that live in natural sea areas and earthen ponds are mainly small benthic diatoms and easily sinking planktonic diatoms. Experiments of bait cultured indoors showed that the use of Trichospialum oxylinum plus calciated Chaetoceros calcinalis or Forkweed Chrysophyta plus Calcarera forensica had the best effect, showing a daily average increase in shell length up to 82 microns. It is much faster than the earthen pond and the sea area, and the survival rate of the juveniles is also high. Feeding bait density increases as juveniles grow. In general, early juveniles cast 25,000 animals per ml to 50,000 animals per milliliter per day. The amount of bait is gradually increased after one week and can be increased to more than 200,000 per milliliter after 9 days. However, it must be pointed out that light intensity illumination is one of the factors that can not be ignored in juvenile breeding. Especially when high-density feeding is performed, attention should be paid to the light factor. Experiments have shown that juveniles are cultured under dark conditions. If high-density bait is used, juveniles grow slowly and have a high mortality rate; while juveniles are cultured at an illumination of about 3200 lx, even if the bait density is as high as 500 000/ml, juveniles grow and grow. The survival rate is high.
4. Substrate attachment The juveniles have strong selectivity to the substrate. Laboratory experiments showed that hard sand shells are suitable for temporary attachment of juveniles; softer sand mud is suitable for burrowing and digging. Therefore, using sand, argillaceous sand or argillaceous sand to crush shells can be used as the attachment base for juveniles. However, argillaceous sand or sandy mud is an ideal bottom material considering juveniles suitable for attachment and facilitating burrowing. It can be seen that different developmental stages of juveniles require different substrates. With the growth and development of juveniles, its habitat is gradually turned from sandy to argillaceous.
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