Parental shrimp mayfly cultivation refers to the female mouth shrimp mayfly that has been mated and the ovaries have matured, or the female mouth shrimp mayfly that the ovaries have developed but not matured, put into the special cultivation pool to make its gonads mature, spawn, hold the eggs and hatch until the pseudoflea-like larvae hatch out of the cultivation process. The cultivation of maturation and egg incubation is carried out in the cultivation pool, which has suitable environmental conditions for mouth shrimp mayflies, and thus promotes good maturation, high egg holding rate and high hatching rate. Parent shrimp mayfly cultivation is to make the mouth shrimp mayfly ovary development is basically synchronized, spawning, larval discharge neat, can get a larger number of pseudoflea-like larvae, the formation of a certain scale of production. There are two kinds of cultivation pools for shrimp mayflies, one is indoor pool and the other is outdoor pool. The indoor pool is usually a concrete pool, and the outdoor pool is a soil pool. Pro shrimp mayfly cultivation should pay special attention to water quality management, bait management and daily management.
1. Water quality management
Water body to maintain dissolved oxygen in 5ml / L or more, daily water change 1/4 ~ 1/3, transparency in 30 ~ 50 cm. Mouth shrimp mayflies belong to variable temperature ferocious crustaceans, its growth and development and life activities are directly affected by the environmental water temperature. The water temperature in its living area is from 6 to 31℃, and the optimal temperature is from 20 to 27℃, which belongs to a wide range of temperatures. Under laboratory conditions, the mouth shrimp mayfly was moved from 17℃ directly into 5℃ seawater, and its body immediately arched, slowly straightened and then fell unconscious. Move it into 33 ℃ seawater, the mouth shrimp mayfly first up and down, then side down on the bottom, only swimming limbs can swing, 3 minutes after the coma. Thus, it is believed that its temperature tolerance range is from 5 to 33℃. If the water temperature changes, the temperature tolerance range will increase. Parental shrimp mayfly cultivation, should pay special attention to the temperature difference, in general, cultivation, water temperature control in 20 ~ 30 ℃. Water temperature is the inhibition of gonadal development of mouth shrimp mayflies, within the appropriate temperature range, the higher the water temperature, the faster the development. If the summer temperature is too high, you can increase the water level to prevent the water temperature is too high and affect the pro shrimp mayfly holding eggs, hatchlings, or even cause death. In the water temperature of 25 ~ 30 ℃, eggs from fertilization to hatchlings, it takes 7 ~ 15 days.
2. bait management
Mouth shrimp mayflies on fish, shrimp, shellfish can be ingested, but to fresh small shellfish is preferred to avoid contamination of water quality. Bait to small pieces of good, to be uniformly scattered cast, in order to ingest, well improve the bait to eat half and reduce the mutual slaughter due to food grabbing. According to the mouth shrimp mayflies day and night characteristics, daily evening baiting can be 1 time, the amount of bait for the pro shrimp mayflies weight 5% to 20%, and with the pro shrimp mayflies holding eggs, water temperature, weather conditions, bait type and quality of the condition of the appropriate increase or decrease. Cultivation of the early stage, can be appropriate to increase the amount of bait for gonadal development of sufficient nutritional requirements. Parent shrimp mayflies hold eggs when drilling, and basically do not feed, so it is estimated that most of the parent shrimp mayflies hold eggs, it is appropriate to reduce the amount of bait. In addition, the pro shrimp mayfly hatchlings, transferred to growth, feeding increased, but also interfere with other egg-holding shrimp mayfly, so it is best to use the cage net and other traps out of the pool.
3. Daily management
Cultivation period, pond patrol is necessary to check the water in and out of the drainage, mouth shrimp mayfly activities and feeding, water quality, especially the discharge of larvae. Once you find that the pro-shrimp mayflies discharged pseudoflea-like larvae, the larvae will be collected into the nursery pond for nursery. The spawning and reproduction of the mouth shrimp mayflies have strict requirements for environmental conditions, especially for the substrate, burrows and light, and without suitable conditions, they will not spawn, or even if they spawn, they will not hatch. Therefore, it is necessary to put soft mud (20-30 cm thick) taken from the intertidal zone at the bottom of a fiberglass round tank (2 m × 1.0 in diameter), lay it flat, add seawater to 30 cm from the surface of the mud, disinfect it by immersing it in sodium hypochlorite for 24 hours, then neutralize it, wash it, and make the seawater in the tank have the same pH as that of the filtered seawater and cover it with a black cloth to keep it in reserve.
Select 16 tails of mature gonads of large, active individuals with complete appendages (gonadal coefficient of 15% or more), and put them into the above incubation tank after formaldehyde disinfection. Mouth shrimp mayflies digging burrow ability is very strong, as long as the substrate and environmental conditions are suitable, sexually mature shrimp mayflies can be completed in a very short period of time to create a "u" shaped burrow, but also a large and a small two mouths, the diameter of the large mouth of 5 to 7 cm, the diameter of the small mouth of about 2 cm. When the water temperature rises to 24 ~ 25 ℃, pro shrimp mayflies began to lay eggs in the hole holding eggs.
The egg mass produced by the mouth shrimp mayflies is yellow in color, with a diameter between 1.5 and 3 centimeters. Mature egg cells are round, diameter of about 410 to 450 microns, a one-time row, and the jaws hold in the mouth and keep turning, as long as the egg mass is not broken or not external stimuli will be held, from a few hours to a few days. If there are external stimuli such as bright light, fast-flowing water, water temperature difference will be quickly thrown off the egg mass. The fertilized eggs of the mouth shrimp mayfly are in the form of surface egg cleavage, and are incubated in running water for about 20 days at a water temperature of 26 to 28°C to grow to the mouth shrimp mayfly pseudo-daphnia larvae (i.e., mouth shrimp mayfly larvae). During this period of time, the water flow should be controlled so as not to make the tank flush mixed, the outgoing water and the incoming water should be equalized, and the water should be changed with a 100-mesh sieve. The dissolved oxygen level in the tank should be greater than 5 mg/l. Spawning, hatching to larvae are completed in the burrow with the mother, when the larvae leave the burrow and the mother, floating in the water, that is, the metamorphosis of the mouth shrimp mayfly larvae. From the mouth shrimp mayfly larvae metamorphosis for young mouth shrimp mayfly need 3 ~ 4 months. At this time, the larvae should be separated from the original cultivation tank. 1. Nursery preparation
Shrimp mayfly in artificial nursery season is determined by the female shrimp mayfly gonad development season. Zhejiang coastal black spot mouth shrimp mayfly male and female mating time in the water temperature down to 15 ℃ in the late fall and water temperature rises to 15 ℃ after the spring and summer; but the female shrimp mayfly ovary development in the water temperature is higher than 15 ℃ in the spring and summer season. Therefore, the breeding period is from April to August (water temperature 20-30℃), and the breeding season is from May to June (water temperature 20-29℃). In addition, the ovarian development of the shrimp mayfly is asynchronous, and thus it can be nursed several times during its breeding season.
Shrimp mayfly artificial nursery facilities can be borrowed from the shrimp nursery plant full set of equipment. However, from the parent shrimp mayfly cultivation effect, indoor cement pool cultivation of parent shrimp mayfly effect is poor, can not keep up with the needs of nursery production; and outdoor pool cultivation of parent shrimp mayfly effect is better, its survival rate, holding the egg rate are more ideal. Therefore, in the nursery facilities, need to be equipped with another temporary, cultivation of shrimp mayfly parent earth pool, the area with the scale of nursery. Earth pool water depth should be more than 1.5 meters, and easy to enter and drain, can be installed to collect young net box.
2. Selection of transportation
Parent shrimp mayflies can choose artificial culture or natural sea area has been mated female shrimp mayflies. Although the body length of 8 cm or more, shrimp mayflies can reproduce, but in order to ensure the quality and improve the number of eggs, it is appropriate to choose the body length of 11 cm or more, weighing more than 30 grams of female shrimp mayflies have been mated. Acquisition of pro shrimp mayflies should pay attention to: shrimp mayflies out of the water time should be short, gonadal development degree is good, strong body, appendages complete, no scars, strong vitality, bright body color.
Parent shrimp mayfly acquisition, should be transported to the nursery as soon as possible, into the parent shrimp mayfly pool temporary cultivation. Parental shrimp mayfly transportation can be used live water boat transportation, nylon bag oxygenated transportation, dry moisturizing transportation, canvas drums and other methods of transportation with water.
(1) live water boat transportation: this method of transport density is high, transport survival rate is also high, suitable for long-distance transportation. Transportation density 40 ~ 60 kg / m? The transportation time is 30 hours, and the survival rate of transportation can reach more than 95%. But need to pay attention to the salinity difference between the sea area and the adverse effects of muddy water area.
(2) nylon bag oxygenated transportation: nylon bag made of thick film (12 silk or more). 50 cm × 50 cm × 25 cm bag to put 3 kg, 24 hours of transportation time, survival rate of more than 95%. But need to pay attention to the density can not be too high, in order to prevent extrusion injury.
(3) dry moisturizing transportation: in the foam box put multi-layer crab seedling box, each layer put 2 kg or so, the transportation time of 12 hours, the survival rate of more than 90%. Need to pay attention to the high and low temperatures and prevent dehydration of the pro-shrimp mayflies.
(4) canvas drums and other water transport: ready to inflatable pump, transport density 30 kg / m? Long-distance transportation, pay attention to changes in water quality, change some fresh seawater at the right time.
3. Parental cultivation
Parental shrimp mayfly cultivation refers to the mated female shrimp mayfly, put into a special cultivation pool to raise, so that its gonadal maturation, spawning, holding eggs hatch; until the cultivation process of the pseudo flea-like larvae hatch out. It is appropriate to promote the maturation of the cultivation and holding eggs hatching in the earth pool. Because the cement pond cultivation pro shrimp mayfly is far less than the earth pool. Although a few of the pro shrimp mayflies in the cement pool can hold eggs, but the pool water is slightly disturbed, the egg bag off; and most of the pro shrimp mayflies not only do not hold eggs, but the gonadal degradation, the cultivation of the survival rate is also low; and the body of the parent body of the poor, no sense of struggle to hold, the surface of the body by the mechanical damage is serious, and even body or appendage rot phenomenon. The earth pool cultivation of shrimp mayflies holding eggs, hatching smoothly, and its hatchlings have a strong phototropism, good quality; at the same time, the parent body is good, a strong sense of struggle; no damage phenomenon, the survival rate is high. This is mainly due to the soil pool has its own suitable environment: water temperature of 20 ~ 30 ℃, mud substrate or mud and sand bottom. As a result, the heat promotion effect is good, high egg holding rate, hatching rate is also high.
Shrimp mayfly ripening cultivation and holding eggs hatching management work is as follows:
(1) water quality management: to maintain dissolved oxygen in 5 mg / liter, daily water change 1/4 to 1/3, transparency in 30 to 50 cm. Water temperature control at 20 ~ 30 ℃, salinity of each sea area is basically suitable. Water temperature is a constraint on the gonadal development of shrimp mayflies, in the 20 ~ 30 ℃ temperature range, the higher the water temperature, the faster the development. If the summer temperature is too high, you can increase the water level to prevent the water temperature is too high, thus affecting the parent shrimp mayfly holding eggs, hatchlings, or even death. In the water temperature of 25 ~ 30 ℃, eggs from fertilization to hatchlings, it takes 7 ~ 15 days. In addition, salinity is also one of the constraints, salinity below 7.7 ‰, will lead to the embryonic development stops and out of the membrane larvae death, especially the salinity of the sudden change, and the magnitude of the change is large, but also cause a large number of deaths of the pro-shrimp mayflies.
(2) bait management: shrimp mayflies on fish, shrimp, shellfish can eat, but to shellfish or sandworms and other bait rich in unsaturated fatty acids is good, which is the shrimp mayfly breeding needs. The bait should be evenly dispersed, so that mayflies ingest, improve the utilization of bait and reduce the scraping and killing. According to the shrimp mayflies day and night characteristics, daily baiting in the evening, the amount of bait for the pro shrimp mayflies 5% to 20% of the total weight, and with the pro shrimp mayflies holding eggs, water temperature, weather conditions, bait type and quality of the condition of the appropriate increase or decrease the amount of bait. Pro shrimp mayflies hold eggs when drilling and basically do not feed, when it is estimated that most of the pro shrimp mayflies hold eggs, it is appropriate to reduce the amount of bait. Because of the pro shrimp mayflies hatch young, turn into growth, feeding greatly increased, but also interfere with other holding eggs shrimp mayflies, so it is best to use the nets and other traps out of the pool.
(3) daily management: during the cultivation period, pond inspection is a must, check the water in and out of the situation, activity, feeding, water quality, especially the discharge of larvae. Once found that the pro-shrimp mayflies discharged pseudoflea-like larvae, that is, the collection of larvae into the nursery pond for nursery. Although it is good to cultivate pro-shrimp mayflies in earthen ponds, it is difficult to collect the larvae. Take the water collection of young method is feasible, but the pool must have the appropriate height difference, and there must be a certain flow rate, the flow rate is too small to release the larvae, the flow rate is too fast, the larvae are easy to be glued to the net. The use of shrimp mayfly pseudoflea-like larvae of phototropism, take the lamp lure method set of young can also be, but we must pay attention to the larvae sticking to the net and the larvae are too dense to cause injuries caused by extrusion.
4. Larval development
Parental shrimp mayflies hatch out of the larvae of the Chinese name for the pseudo-flea-like larvae or pseudo-flea-like larvae. Its larval development has obvious metamorphosis phenomenon, Japanese scholars T. Hamano and other scholars according to the mouth shrimp mayfly pseudo flea-like larvae of the morphological characteristics of the pseudo flea-like larvae, the pseudo flea-like larvae divided into Ⅱ stage. As for the phasing of the larvae of the black-spotted mouth shrimp mayfly, the authors divided its pseudoflea-like larvae into three major phases (called phases and Ⅱ phasing method to show the difference) according to the morphological characteristics, activity status, ecological and nutritional characteristics of its pseudoflea-like larvae, and then combined with the needs of productive nursery. The phases and their characteristics are as follows:
Phase Ⅰ (yolk nutrition stage): body length of 1 to 3 millimeters, living on yolk nutrition, not feeding. The larvae are mainly active at the bottom of the water. The first stage is mainly crawling, with backlighting; the later stage is more active, with obvious phototropism. The compound eye is a stalked eye, and its cephalothoracic armor is subelliptical, with a strong middle spine and only the first and second thoracic limbs. It needs to shed its skin twice.
Phase II (planktonic stage): body length 4 to 11 millimeters, at this time the yolk has been depleted, and open to feed on small zooplankton, planktonic life, phototaxis, soft cephalothoracic armor, no hard spines in the hand. In the early stage, the activity is poor, can only swim flat, and in the later stage, the activity is enhanced, can turn over and upside down. Morphologically, the 5th to 8th abdominal limbs and the 2nd antennal whip appear, the cephalothoracic armor is nearly triangular, and the tail fan begins to appear. It needs to shed its skin 7 to 8 times.
Phase III (benthic stage): the individual body length reaches 12 to 20 millimeters, feeding on large zooplankton, the active water layer is the middle and lower part of the water body, the activity ability is very strong, often in the water to turn over or upside down. Morphologically, the tail fan is obvious and appears to be segmented, the width of the abdomen increases, the cephalothoracic armor and thorns are hard, and there is a sense of pins and needles in the hand, the middle thorns of the cephalothorax gradually recede, and the various thoracic feet are further segmented and perfected. The skin needs to be removed 2 to 3 times.
Shrimp mayflies: individual body length of more than 16 millimeters, cephalothoracic armor on both sides of the thorns disappeared, the abdomen is obviously widened, abdominal width is larger than the width of the cephalothoracic armour, the body is similar to the adult, began to live in the cave.
In the water temperature 23 ~ 30 ℃, black spot mouth shrimp mayfly Ⅰ phase pseudoflea-like larvae need more than 20 days of cultivation, in order to metamorphosis into baby shrimp mayfly, complete the whole larval development process. If the nutritional conditions, ecological conditions and other inappropriate, shrimp mayfly pseudoflea-like larvae have delayed metamorphosis phenomenon.
Larval cultivation
From the Ⅰ phase of the pseudoflea-like larvae into the pool to the baby shrimp mayflies out of the pool of the cultivation process for the larval cultivation.
(1) Juvenile density:
Because of its individual large, so the cultivation density should not be too high. Reasonable density is: Ⅰ phase larvae 100,000 ~ 150,000 tails / m? Around; Ⅱ phase larvae 50,000 ~ 70,000 tails / m? ; Ⅲ phase larvae 10,000 to 20,000 tails / meter?
(2) water temperature regulation:
Shrimp mayfly pseudoflea-like larvae in the water temperature of 20 ~ 30 ℃ can develop normally, but in the temperature range, with the rise in water temperature, larval development has a tendency to accelerate. Therefore, in the entire period of larval cultivation, the water temperature should be controlled at 25 ~ 30 ℃, and the water temperature to gradually improve the best.
(3) salinity regulation:
Shrimp mayfly larvae on salinity adaptability is broader, the sea water of various sea areas can basically adapt. In the nursery salinity to 13 ‰ ~ 33 ‰ is appropriate.
(4) inflatable amount of regulation:
The diffuser stone in the nursery pool to 1 ~ 1.5 / ㎡ for the degree. The inflatable amount Ⅰ phase of the larval stage is a small wave, Ⅱ phase of the larval stage is a wave, Ⅲ phase of the larval stage is a boiling.
(5) light regulation:
Shrimp mayfly's pseudoflea-like larvae have strong phototropism for a certain light intensity (100~1000 le), but for strong light (>1500 le) is shown as a backlight. In high water temperature (28 ~ 30 ℃), the light is too strong, not only cause filamentous mixed algae clumps, but also stimulate the larvae to the bottom of the pool or the pool corner to concentrate, increase the chances of killing each other among the young forest. Thus, it is advisable to take light-shading measures for nursery.
(6) Bait management:
Because the pseudoflea-like larvae are large and have strong predatory feet, they need bait with larger particles. In the phase I and II larval stage, its palatable bait is halophilous unsegmented larvae, staphylinids and branchiostomes, which are preferable to live ones, and can also be supplemented with shrimp powder and cake. In the phase III larval stage, adult brine shrimp and fresh small juvenile shellfish are preferred, supplemented by dried brine shrimp, fresh fish, shrimp and shellfish. Choosing the appropriate larval bait is one of the keys to high yield in nursery.
(7) water quality regulation:
Nursery seawater needs to be precipitated, sand filtering, in order to prevent heavy metal ions are too high, can be added EDTA-Na salt 2 ~ 5 mg / liter. Water exchange is an important measure to ensure good water quality, the amount of water exchange in each period is: Ⅰ phase of the larval period for 30% to 40%, Ⅱ phase of the larval period for 40% to 70%, Ⅲ phase of the larval period for 70% to more than 100%. Suction is also a good measure to improve water quality, daily or every other day the bottom of the pool suction, conducive to the stability of water quality.
(8) Prevent mutual killing:
The larvae's large individual size and strong foot predation are the main reasons for killing, in addition, the bait is insufficient or unsuitable, the cultivation density is too high, and the light is too strong, etc. will also lead to killing. To prevent killing, we can start from the following aspects: feeding and throwing enough suitable bait, cultivation density should not be too large, shading, algae or other substances to adjust the water color, hanging in the pool of the dense mesh, and so on. In addition, phase III larvae have obvious benthic nature, put some mud on the bottom of the pool will improve the metamorphosis rate and survival rate of larvae.
(9) Seedling:
Farmers can accept both baby shrimp mayflies and the late larvae of phase III, but prefer baby shrimp mayflies. As a result, the proportion of baby shrimp mayflies in the nursery pool is more than 50%, then the seedlings can be released. In addition, the salinity acclimatization test on the Ⅲ-phase pseudoflea-like larvae of the blackspot mouth shrimp mayfly and the baby shrimp mayfly showed that its suitable salinity of the culture water body is 8‰～33‰ Thus, before the release of the seedling, it is necessary to adjust the salinity according to the difference between the salinity of the farm and the salinity of the nursery for gradual domestication in order to increase the survival rate of the stocking.
Larvae out of the pool
Shrimp species generally to the baby shrimp change Qi 4 days before the seedling, but for different species of shrimp seedling specifications have different requirements, such as the Chinese shrimp body length of 0.7 centimeters or more, the long-haired shrimp body length should also be in the 0.7 centimeters or more, the knife amount of the new shrimp should be 0.5 centimeters or more, while the spotted prawns should be in the 1.5 centimeters or more. Due to the mass of crabs in the middle of the transient level of differences in the emergence specifications vary greatly. Such as river crab fry specifications generally to big eye larvae become flush 3 to 4 days after the seedling, while the saw edge blue crab to be in the 2nd to 5th period of juvenile crabs to be out of the seedling.