Pearl culture refers to the cultivation of pearlsPearl oysterIt can secrete nacreous substance to form pearls, implant cell fragments or pearl nucleus plus cell fragments in the body of pearl shellfish, and cultivate pearls after a certain period of time.
Chinese name
Pearl culture
Pearl
An ancient organic gem
Mainly produced in
In pearl molluscs and pearl mother molluscs
Substantive
Mineral (aragonite) beads containing calcium carbonate
Causes
Endocrine function
Composition
It is composed of a large number of tiny aragonite crystals
1. Selection of mother oysters: choose pearl oysters with intact shells, no damage, plump soft parts inside the shells, no disease and other healthy ones as mother oysters for pearl cultivation.
2. Surgical nuclear implantation: The cell fragments and bead nuclei are implanted into the pearl mother shell by minimally invasive surgery.Then put the pearl oyster back into the water for recuperation.
3. Culture and pearl cultivation: put pearl oysters in net cages, and then hang them in the water with ropes for cultivation.
4. Peeling pearls from seashells: After one to two years of pearl cultivation, pearls can be harvested from seashells.It usually takes 4-5 years to harvest the seedless pearls.
origin
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The artificial cultivation of pearls originated in China.Pang Yuanying of the Song Dynasty recorded in his "Miscellaneous Records of Wenchang" that "there was a method of raising pearls, taking a slightly large clam, soaking it in clean water, waiting for it to open its mouth, and rushing to use pearls to throw it... to exchange clean water frequently, and it will become a pearl in autumn!" In the Ming Dynasty, China also invented a method of cultivating special pearls, which successfully raised world-famous pearls“Buddha pearl”。
principle
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The soft part of the pearl shell itself has lesions, or it is unable to expel the invading external foreign bodies (such as sand grains) from the body. Due to its own physiological function, it will secrete nacreous substance to wrap the lesion or foreign bodies, and after a certain period of time, it will form crystals, which are called natural pearls.
According to the physiological function that pearl shells can secrete nacre to form pearls, cell fragments (or: pearl nucleus+cell fragments) are implanted into the body of pearl shells. Pearls cultivated after a certain period of time are called cultured pearls.
present situation
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The output of Chinese freshwater pearls has ranked first in the world, but the quality is not ideal.Nearly 10 billion young clams are cultivated every year in China, and 500 million to 800 million pearl oysters are produced.If not for the large number of deaths caused by mussel disease, the annual production of commercial pearl mussels and pearls would be more than twice as high.Therefore, it is urgent to improve the quality of pearls and limit the output.
1. Technological progress
The rapid increase of China's pearl production benefits fromHookworm larvaThe breakthrough of manual collection technology and the continuous progress of the cultivation technology of young clams and clams.Although the artificial insemination and artificial incubation technology of river clams have not been solved yet, the artificial reproduction of river clams has not been realized in real sense in production.However, in production, it has been possible to start large-scale cultivation of young clams from the collection of hookworm larvae, thus providing a fundamental guarantee for the source of surgical clams.The popularization of this technology has made farmers in both the north and the south grasp it quickly, and has fully achieved large-scale production.
Secondly, a team of women workers specializing in surgical operations has been formed.In Hunan Hanshou, Anhui Guichi, Wuhu and other places, this township has become the origin of surgical operators, and the number of surgical operators in each township can reach tens of thousands.The pearl cultivation operation has become an important way for local labor export. Through the development of master apprentice, the surgical operator team has been stable, expanded, and continued, so that the manpower in the surgical operation has been guaranteed.
Third, the clam disease control technology has broken through, and the pearl oyster breeding technology has improved to a certain extent.The technology of cultivating plankton and culturing pearl mussels with fertilized water is based on the pond culture technology model of "fertilizing fish".In terms of production management, it is mainly to change the hole hanging mode to the cage mode of "net bag, net clip".In large-scale production, the reform and progress of cage cultivation of surgical clams made it possible to breed seedlings and pearls in the same year, and shortened the pearl breeding cycle.
2. Existing problems
The popularization and development of oyster pearl cultivation technology has also brought many problems.Pearl production is no longer a project with huge profits. The era of huge profits has passed.However, the high profitability of pearl cultivation for many years has made practitioners ignore the role of science and technology in production and blind production continues.
(1) China's pearl industry association is not perfect. Some places have become semi official organizations, lacking industry coordination and self-discipline. The production of pearls is completely disordered, and there is a long way to go to limit production and improve quality.
⑵ Due to the continuous increase of pearl production, the requirements of the whole market for pearl quality are also constantly improving.Although the pearl deep processing technology is also improving, and the use of pearl products is more extensive, low-grade pearls will still face surplus.The standard connotation of "big, bright, round and gorgeous" is also changing.Therefore, in mass production, it is a way to adapt to the market to increase the proportion of high-quality pearls by extending the breeding cycle, which also objectively limits the annual output.However, the pearl industry has not yet actively and consciously limited the production of pearls.
⑶ Collect by mature oystersHookworm larvaThe method of cultivating young clams has been used for many years, resulting inHyriopsis cumingiiGermplasm degradation is becoming more and more serious.The production performance and disease resistance of pearl clam are declining.
⑷ The operation operators lack formal training, and new technologies and processes are difficult to be popularized and applied.There is no way to talk about the management of labor and employment of the operator team.The seasonal operation of the pearl cultivation operation keeps the operator team "migratory" mobility, which is another concentrated manifestation of the backward production mode of the pearl cultivation industry.
(5) In aquaculture production, not only ordinary farmers and small and medium-sized farms, but also large companies, backward production management is still very common.Pearl enterprises, like most clam farmers, lack scientific and technological awareness, and the dominant ideology of pearl production management is still "planting widely and yielding to fate".The formulation and promotion of technical standards for the pearl cultivation industry of clams have just begun, and the work is still quite arduous.
3. Ways to solve problems
Freshwater pearl production has not entered the "era of meager profits", but we should also take precautions to make the industry sustainable. ①The breeding of mussel species should be strengthened from germplasm resources. ②Starting from the management of the operator team, actively promote the new surgical process and systematic disinfection technology. ③Promote and train through government, industry association and other channels to improve the scientific and technological awareness of the owners of oyster pearl cultivation.Popularize scientific theory and knowledge of clam culture and pearl cultivation technology. ④Popularize the group control technology to improve the overall survival rate of the clam pearl industry. ⑤Strengthen the construction of industry associations, play the role of associations, consciously limit the annual output of pearls, and strive to improve the quality of pearls. ⑥Further research on the application of large diameter round fresh water nucleated pearls. ⑦Further develop and utilize low-grade pearls to broaden their use.
Process technology
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(I)MusselArtificial seedling raising technology based on gis
The main shellfish used to cultivate light pearls in China areHyriopsis cumingii。
1. For most clam farmers, pearl clam breeding is generally not carried out.From the perspective of industrial development, there is no need for professional companies to complete the three production links of "artificial breeding - surgical clam cultivation - pearl cultivation".Generally, farmers only engage in oyster breeding.From the perspective of production status, most people buy young mussels, cultivate their own surgical mussels, and then hire others to operate.So briefly introduce the breeding process of clams.
When the breeding period of the mussel comes, the female mussel with eggs is usually selected directly from the mature pearl mussel, and the fertilized eggs will develop toHookworm larvaCollect (send seedlings) with Pelteobagrus fulvidraco in a timely manner.
Each square meter of running water nursery pool can be used to place parasiticHookworm larva20 to 30 small fish.The nursery pool should master a certain amount of water flow, but the flow should not be too fast.Feed the larvae with bait every day to let them grow normally. When the water temperature is above 30 ℃, the hookworm larvae can mature in 4-7 days, and 25-30 ℃ takes 7-9 days.The hookworm larvae parasitized on the fish begin to live freely after falling off, called juvenile mussels, and this process is called shedding.The young clams (1-2 mm) are cultivated in the shallow pool of the nursery shed with running water until the young clams reach about 1 cm.The production process is as follows: female oyster with eggs → hookworm larvae → yellow catfish to send seedlings → young clam cultivation → young clam.
2. There are many methods from young clam cultivation to surgical clam cultivation, but Zhejiang clam farmers widely use the method of cultivating surgical clam in large water surface and small cages in production, and the effect is quite obvious.Cultivate the 1cm young clam directly to the 8cm surgical clam, and the time is shortened to about 3 months.This reform made it possible to breed seedlings and surgically cultivate pearls that year.
The general specification of this small wooden crate is (40-45) cm × (40-60) cm × 10 cm, and it is nailed with Chinese fir (or bamboo) strips, which are generally (1.5-2) cm × (3-4) cm in size.After the wooden frame is nailed, it is closed with 2cm mesh, and the upper part is left with seam.The bottom of the cage is padded with plastic film to place fertilizer mud.It is advisable to put 150 to 200 young clams in each net phase, so that more than 60% of the young clams are expected to be bred into surgical clams in the autumn of that year.
The cultivated water area should be more than 10 mu, and the water level should be 1.5-2.5 meters.Three to five days before the young clams are put into the tank, the base fertilizer should be applied first to improve the water quality according to the water environment (new or old ponds) and the fish stocking amount (50-200 fish/mu of flowers and silver carp in a certain proportion).Make the water color light brown or yellow green, and the transparency is 30-40 cm.The water quality of the young clam should not be too fat before 3cm, or the ammoniaNitrite ionConcentration will inhibit its growth.
During the cultivation process, timely top dressing should be carried out according to the transparency and water color changes. Generally, once every 10-15 days, 150-250kg/mu wet pig manure each time. The fertilizer must be fully fermented and decomposed.It is better not to use chicken and duck manure, and it is recommended to use professional compound fertilizer (the amount can be according to the instructions), which is safe and efficient.
When the young clam grows to 3-5 cm, the amount of fertilizer can be appropriately increased to improve the water body fertility (transparency 30 cm).In addition, quicklime shall be applied every 10-15 days (10 kg/mu).During the whole cultivation period, when the water color becomes light and the transparency increases, fertilizer should be applied in time.But do not let blue-green algae flourish or the transparency drop below 25 cm.
If scientific management can be carried out as required, 60% of the young clams in less than 3 months can meet the surgical specifications.
（2） Operation technique of fresh water seedless pearl
The method of culturing pearls by transplanting the epithelial tissue of shellfish mantle into the pearl raising shellfish has always been the basic surgical technology of artificial cultivation of pearls.After years of efforts, we have scientifically combined the film tearing process and systematic disinfection technology to form a new set of surgical operation processes, processes, and quality management measures for surgical operation.The training of operation operators and the practice of breeding production show that this technology and its management measures not only greatly improve the rate of "big, bright, round and gorgeous" high-quality pearl, but also make the survival rate of pearl clams reach more than 95% after operation, and can effectively prevent the occurrence of clam diseases.
New process
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(1) Process: ① Cut off the front and rear adductor muscles to open the double shell → ② Use a scalpel to cut a knife at the edge of the mantle → ③ Cut a second knife (heavier) at the muscle mark → ④ Use tweezers to tear off the inner epidermis of the marginal membrane from the front of the shell → ⑤ Repeat the steps ② - ④ on the other half → ⑥ Take the glass plate out of the disinfectant → ⑦ Place the prepared tissue band of the mantle on the glass plate,The inside face is downward → ⑧ Wipe off mucus and dirt with cotton → ⑨ Cut the wound of tissue band with a slicing knife to make its width consistent, and slice → ⑩ Add drops of tablet solution → 11 Send to the transplant worker
(2) Technical key points
① The first knife should be in the color line, flat, even and decisive, and the depth should reach the connective tissue layer in the middle of the mantle.The second knife (which can also be omitted) should be at the muscle mark of the mantle or near the center as far as possible to make a wider tissue band.
② Tearing the film should start from the front of the outer coat film, so as to make full use of the small holes near the water outlet.
③ There are tweezers to clip cotton wool, sort out tissue pieces, and wipe mucus.
④ After the tissue band is placed on the glass plate, the two rough surfaces shall be flattened and the width shall be uniform.The cut pieces shall be 4mm × 5mm, and shall be square after shrinking.Slicing shall be decisive, crisp and smooth.
⑤ After slicing, special drops shall be added in time for maintenance.
⑥ The glass plate disinfectant, cotton soaking solution and drop solution should be prepared on the same day, and used on the same day.
⑦ The tissue piece shall not contact other things, and pollution shall be strictly prevented.
⑧ The production process is completed by one person in a row, which is required to be completed within 2 minutes, and used for vaccination in a timely manner. It cannot be stored for too long.The production process is very important, which is related to the quality of pearls, and management should be strengthened.
2. Graft technology
(1) The process shall select the pearl oyster and mark the date and operator code on the shell.
① Open with a shell opener, add a mouth opener, and insert a plug → ② Wipe the dirt in the coat cavity, and make the axe foot side to side → ③ Push the small piece of letter with a film feeding needle, and pick up the small piece with the help of the opening needle → ④ Hook the mouth with an opening needle starting from the right under the edge film → ⑤ Send the small piece 0.5 cm deep into the wound → ⑥ Press the wound with an opening needle, and pull out the film feeding needle → ⑦ Pull, press, squeeze, and squeeze the small piece of letter with an opening needlePush the whole circle → ⑧ From top to bottom, from right to left, repeat ③ - ⑦ until completion → ⑨ Pull out the plug and put the pearl clam into the Chinese medicine soaking solution → ⑩ Hang the pearl clam for cultivation
(2) Technical points
① The implant tool should be suitable for the specification of the surgical clam, and the opening size should be suitable for the size of the small piece.
② Arrangement: 6 in the first row, 5 (6) in the second row, and 5 (4) in the third row, in a plum shaped layout.The spacing between rows and columns is moderate, and the overall shape is intact.The total number of explants for the first clam is 32.
③ "Push, pull, press and squeeze" shall be strictly rounded.
④ Edge and mouth bead are in place.The source position of the patch and the position of the graft should be consistent as far as possible.
⑤ The opening plug shall not be too large. Try to use a mouthpiece.
⑥ Strictly select the surgical clams, and select the production clams and pearl raising clams for temporary breeding as required.
⑦ The sponge used to clean the tablet delivery needle shall be cleaned and disinfected in time.
⑧ The operation time of each mussel graft is required to be 5 minutes.
3. Systematic disinfection technology for surgical operation (patent applied)
Environmental disinfection (disinfectant I)↘ Drop tablet medicine
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Environmental disinfection (disinfectant II) → film making operation → small piece of mantle tissue → implant operation
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Environmental disinfection (disinfectant III)↗ Cultivated pearl mussel ← Cultivated pearl mussel
↓
Drug immersion (disinfectant IV)
(2) Technical key points
① Disinfection of operating rooms and appliances: operating rooms, operating tables, boxes, barrels, utensils and towels should be washed or soaked with chlorine containing disinfectant I before and after work every day.
② Disinfection of glass plate: for the glass plate used for production, first clean the dirt and debris on the plate with clean water, then transfer it to the disinfectant II containing antibiotics for soaking. The production operator takes out the glass plate from it every time, and then conduct production.
③ Use of disinfectant cotton: use antibiotics and other drugs to prepare isotonic disinfectant III to soak the cotton (small cotton balls).During the production operation, only one production clam is used to hold the medicine with tweezers, and no repetition is allowed.The method of using medicated cotton to assist in the production is better than using sponge. It reduces the friction and damage between the rough surface of sponge and tissue, and avoids mutual infection.At the same time, the disinfection cotton wool method is also most suitable to be used together with the "film tearing method", so that tissue fragments can completely avoid contact with hands, tabletops, towels and other objects, and meet higher epidemic prevention requirements.
④ Tablet dropping solution: since the mid-1990s, the multifunctional compound tablet dropping drug "Di Pianbao" with isotonic, anti infective, wound healing and other functions has been popularized, and the effect is very obvious.
⑤ Medicine bath for pearl raising clam: The pearl raising clam just after the implant is placed in pure Chinese medicine disinfectant IV to soak for more than 20 minutes in time, so that the medicine can fully contact the wound through the coat cavity.
The discarded clams after production should be transported away in time for treatment.
4. Operation management
The new process of disinfection cotton method and film tearing method are adopted. The operators are divided into three groups, and one person is responsible for making a film for two people. On average, every three groups need three auxiliary workers (including two female workers washing clam shells).For the operation in large-scale production, someone should be specially responsible for the management of disinfection, coordination and inspection.
The three person combination mode can achieve clear responsibilities, which is conducive to assessment;The division of production and planting operations is conducive to the specialization and excellence of operation technology.However, the combination of "one person producing independently, implant" or "two person producing, three person implant" is not suitable.
3、 Culture technology of pearl oyster
Due to the continuous improvement of the requirements for pearl quality, the cultivation period of pearl mussels needs 4-5 years, and the production management is significantly different from that of general aquaculture projects.
1. Water area selection
The water area with guaranteed water source all the year round, no pollution, convenient water inlet and drainage, fertile water quality, aquatic higher plants on the surface, less sediment and about 2m in hydrology shall be selected.If there is micro water, the area can be from less than 1 hectare to more than 10 hectares.If there is no micro flow water all the year round, it is generally appropriate to build a water surface of 3-5 hectares manually.In terms of water area type, if the water level of mountain ponds and small reservoirs fluctuates slightly, they can also be used as pearl farms.Pearl mussels can also be cultivated in the outer marsh of water quality and fertilizer, lakes, and large and medium-sized reservoirs with longer age.In a word, as long as there are abundant bait organisms and inland waters with certain water flow or wind movement, they can be used as places for raising clams and pearls.
The content of calcium in water should be more than 50 mg of calcium carbonate per milliliter of water. The pH of water should be neutral and slightly alkaline (pH 6.8-8.5).
The annual average water temperature of the pearl oyster breeding farm is 17-20 ℃. The daily maximum temperature of the surface water is not more than 38 ℃, the minimum temperature is not less than 2 ℃, and the optimal temperature is 23-30 ℃.Generally, the Pearl River area should be sunny and ventilated, which is conducive to heat transmission and constant water temperature.
2. Hoisting method
The purpose of culturing pearl clams in the water layer with high plankton is to provide them with sufficient food and dissolved oxygen.Therefore, the measures for fixing and lifting are always improving, but floats and ropes are the most basic.What has changed most is the apparatus for placing oysters, and the most common ones are net bags and net clips.
Before stocking, the banks near both banks must be selected in the water area, and bamboo or tree stumps must be used to make fixed frames or directly pile on both banks.Then pull ropes along the water surface every 1-2 meters, and tie floats on each polyethylene rope at a certain distance.Floats are used to suspend pearl oysters in the water layer evenly. Plastic floating balls and empty plastic bottles with certain buoyancy can be used as floats.
The mesh bag and mesh clip are generally made of polyethylene.An elastic ring made of bamboo strips is propped in the round mesh bag to ensure the fixed shape of the mesh bag.Each net bag can only contain 1-2 oysters.We also use this net bag method to temporarily raise clams during fattening operation, with 5 young clams in each bag.Therefore, it is better to hang two pearl mussels with their water outlets facing outward and their ventral edges facing downward in bamboo net bags.
The mesh clip is long, with large mesh and smooth water flow, but the clam shell is easy to be trapped by the mesh cable, causing depression, or even damaging the outer membrane.Each net clip should contain 3-4 oysters.
Except in winter and hot summer, most of the time they are raised in the layer water within 0.4 meters.
3. Recovery after operation
If systematic disinfection can be carried out according to the requirements during the operation, and Dipian Bao Dipian can be strictly used, the surgical clams generally come from the young clam breeding pool, and are hoisted back to the original pond after inoculation, all of them can recover normally and grow rapidly.After the operation, if it needs to be transferred to the pool for hanging (i.e. from the young clam breeding pool to the pearl breeding pool), the pool needs to be cleaned and disinfected, and then sufficient fertilizer (250-500kg/mu of pig manure) should be applied in advance to improve the water quality (light brown or yellow green).
No fertilizer should be applied to the clams within one week after they are raised.If the water color fails to meet the requirements, it can be fed with soybean milk, generally 1kg soybean/mu per day, and sprinkled in 2-3 times after pulping for 3-5 consecutive days.One week later, it is recommended to use dedicatedCompound fertilizer。If organic fertilizer is used, it can be topdressed according to the change of water color, but the organic fertilizer must be fully fermented, decomposed thoroughly, and mixed with quicklime for disinfection before use.The dosage is 150 kg/mu (pig manure) each time, and chicken and duck manure should not be used as much as possible within 3 months.
4. Reasonable fertilization and control of plankton
Nitrogen, phosphorus, potassium, calcium and so on are the basic nutrients in the water body for mussel culture.There are many moreMineral elementAnd trace elements are also very important in the production waters for raising clams and pearls.This is somewhat different from the general aquaculture waters.
Organic fertilizer or chemical fertilizer can be used for water body.Among all kinds of organic fertilizers, poultry fertilizer has better fertilizer effect, but it is also easy to be excessive, and unfermented poultry fertilizer is easy to cause clam disease.Generally, farmyard manure is not as good as pig manure and cow manure from large-scale farms, which mainly depends on whether livestock are fed with full price feed.Organic fertilizer must be fermented and decomposed. It is better to mix it with lime when using.
As top dressing, the amount of organic fertilizer should be used several times in a small amount according to the specific water color, transparency, season, weather conditions, etc. of the water body where the mussel is raised.It is not allowed to fix the dosage each time or copy books mechanically or by others' introduction.The dosage is determined according to the type of organic fertilizer, dry and wet conditions. Generally, the topdressing is 150-250kg/mu per time, depending on the water color. The growth season from May to October is once every half month, and the interval between November and April of the next year can be longer.
The proportion of nitrogen, phosphorus and potassium should be mastered in the use of chemical fertilizers. It is better to use compound fertilizers or combine them with organic fertilizers.Otherwise, there will be too many blue and green algae.
The role of fertilization is to cultivate plankton (algae and zooplankton) in the water body. Phytoplankton (algae) and organic debris are the food for the oyster.During the whole pearl oyster culture period, the special purpose should be used in high temperature season every yearCompound fertilizer。
Different algae have different nutrition and digestibility to oyster.In production, it is necessary to adjust water quality through fertilization, flushing, trace elements, lime, biological agents and other methods, so as to make the structural proportion of algae as beneficial to the growth of pearl mussels and the cultivation of pearls as possible.The most favorable algae for pearl oysters are diatoms, chrysophyta, xanthophyta, and some unicellular species in Euglenophyta.Judging from the water color, it should generally be yellowish brown and yellowish green.Dark green and dark green water is generally dominated by blue and green algae, which will further develop into "water blooms" and can be controlled by drugs such as Qinglichen.If there are too many zooplankton, pesticides can be used to kill them.
A certain number of silver carp, bighead carp (200/mu) and a certain amount of grass, crucian carp and Xenocypris japonicus are stocked in the pearl clam culture water body, which plays a certain role in preventing excessive blue and green algae.
5. Lime application and water quality control
Quicklime is often used to raise clams, which is an important measure to regulate water quality.For ordinary fresh water bodies, it is better to use about 10kg/mu each time.The growth season is once every half month, and once a month in spring and after autumn.
In the process of pearl oyster culture, according to the different characteristics of the water area, the major elements, trace elements andMicrobial preparationCan promote the growth of pearls.With the continuous deepening of research on the physiology and pearl of pearl oysters, as well as the technological progress of artificial control measures for water environment, the use of physical, chemical and biological methods to control water quality has become more and more popular.
4、 Control technology of clam disease
（1） Causes of clam disease
1. External environmental factors
If the water temperature is too high or the temperature difference changes too violently, the metabolism of the breeding pearl clam will be out of balance.The season with the most clam diseases is the season with the most diurnal temperature changes.
If the pH is too low or too high, the pearl oyster cannot adapt.In the state of low dissolved oxygen, the organic matter in the water body cannot be completely oxidized and decomposed. As a result, the accumulation of organic acids increases, leading to the decline of the pH value of the water body and the deterioration of the physical and chemical indicators of the water body.
Once foreign poisons enter the water body, they will cause greater harm to the clam body.
2. Unscientific management
ExcessiveOrganic fertilizer, or improper fertilization leading to clam disease is the most common phenomenon in production.
Excessive stocking of fish will easily lead to hypoxia in the water body, and long-term hypoxia will indirectly affect the health of the clam body, thus causing clam disease.Once a small number of dead clams appear in production, if the dead clams are not removed in time, they may spread rapidly and increase mortality.
The operation was carried out when the young clams were not cultivated scientifically or were weak, and the sudden death after operation was also quite common.
The clam body is damaged due to improper operations such as long-distance transportation, bad transportation conditions, temporary accumulation, long water leaving time, etc.
3. Invasion of pathogenic organisms
The pathogens that can cause pearl clams to get sick include viruses, bacteria, fungi, protozoa and other parasitic worms.Parasites and bacteria are the most harmful in production.
Factors of clam body
Multi generation inbreeding and no breeding are the basic reasons for poor disease resistance and easy infection of pathogens.
（2） Epidemic law of mussel disease
1. All kinds of clam diseases can be found almost all year round, especially diseases such as red rot foot can be seen in the cold season from December to next March, but the peak of clam disease is in April June and September October.The peak period of mussel disease is also the most active period of parasites, so the relationship between mussel disease and parasites is very close.
2. During the whole clam raising period from the operation to the pearl harvest, there are several obvious high disease incidence areas: 1-2 months, 8-13 months, 19-22 months after the operation.The canker and perforation of the mantle is mostly in the first section, the second section is the high incidence period of all kinds of diseases, and the third section is also typical of the ulcer of the mantle tentacles in addition to other diseases.
3. In general, the health of surgical clams is poor in high temperature season, especially those that are not strictly disinfected in operation are most likely to get sick, and the mortality rate is 50% - 60%.The mortality rate is more than 80% in some waters with poor aquaculture conditions.The clam disease is generally "subacute" or "chronic", which is similar to the generalConditional pathogenThe characteristics are consistent.
4. The water environment is also related to the occurrence of clam disease.Too shallow water level, too large temperature difference, too large or stagnant water flow, high turbidity, low pH value, high ammonia nitrogen content, and low dissolved oxygen are easy to cause clam disease.
5. Excessive fertilization, especially poultry fertilizer, is closely related to the morbidity.
First of all, pay attention to the shell length, shell height, the thickness of the clam body between the two shells, the density of the growth line of the growth ring, and the number of soft edges at the belly edge. Observe the composition characteristics of the attached biological community outside the shell to judge the growth, health level, and water environment characteristics of the pearl clam.
1. Collection and submission of diseased clam samples
⑴ Collection method Generally, the diseased clams have the following manifestations: the diseased clams put forward that the water surface is weak or even does not spray water.The double shell opens slightly, and the shell closes slowly and weakly after leaving the water, and the reaction is slow.The abdominal edge drips mucus.
The distance between two shells of poor or diseased clams is narrow, and the soft edge of the shell belly is not obvious.It can also collect seriously ill and dying oysters.
(2) The collected diseased clam samples should be submitted for inspection in time. If they cannot be submitted for inspection in time, they should be kept in clean water temporarily, but the time should not be too long (especially in high temperature season). The samples submitted from different breeding ponds should not be put together.
It is better to open the container on the way of inspection, not to put it in a sealed plastic bag, but also to avoid excessive drying, high temperature and other conditions.
2. Microscopic examination of pathogenic organisms
⑴ Observe in vivo the gills, lips and other organs in close contact with the external water body, as well as the mucus in the mantle cavity, and use a 100-400 times microscope for direct inspection.49% of bacterial mussel diseases are affected by parasites to varying degrees.
⑵ Bacterial contact smear observation For liver, gill, intestine (stomach), mucus and ulceration lesions, carry out contact smear according to aseptic operation, and Gram staining, and then observe with oil microscope.
The density of parasites and bacteria in microscopic examination can be expressed as+,++,+++. During operation, contamination between organs should be prevented to avoid affecting the results.
Clam disease control
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1. Prevention of clam disease
(1) Sterilization and epidemic prevention shall be well controlled. Both parent clams, young clams and surgical clams shall be collectively raised temporarily before stocking, and the temporary breeding pool shall be fully disinfected.Systematic disinfection procedure of surgical operation is an important link in the prevention and treatment of clam disease and should be applied.
(2) Thorough pond cleaning Before stocking oysters, the aquaculture water body and the whole environment should be thoroughly disinfected. This measure is called "pond cleaning".The method is to drain the water, use 80kg/mu quicklime to dissolve the slurry, and then evenly sprinkle it, and then mix it with the sludge.If there is water that cannot be pumped dry, more lime can also be used to achieve the purpose. If there is a water level of 1 meter or more, the amount of lime is 150 kg/mu.
⑶ Control the introduction of the water source into the external water source of the Pearl River water body, and use polyethylene mesh for filtering to prevent small miscellaneous fish, crabs, other harmful insects and other animals from entering, not to mention the introduction of water from the upstream epidemic areas where mussel disease occurs. ⑷Fertilizer disinfection Organic fertilizer must be fully fermented and decomposed, mixed with quicklime before use, and then sprinkled comprehensively, with a small amount for many times.
(5) For drug prevention, disinfectant shall be used once every half month in the season of clam disease prevalence, and it shall be used in time when the water is muddy after heavy rainWater quality improverOr quicklime to control water quality.When the water temperature is 15-25 ℃ (especially at the turn of spring and summer), insecticide should be used every half month.
2. Treatment of clam disease
According to my 10 years' experience in diagnosis and treatment of mussel diseases, typical viral mussel diseases and fungal mussel diseases are rarely found.But variousBacterial diseaseAnd parasitic diseases.According to the actual production, the common clam diseases and their control methods are briefly introduced as follows:
⑴ Burnt gills, general gill soft drive and grayness are the symptoms of bacterial gill disease.Microscopic examination found that bacterial branchial disease commonly occurred in the shedding of gill epithelium, sometimes small, sometimes all scattered single cells.
Prevention and control: use water improver once.Use dichloride disinfectant for three times, and then sprinkle soymilk with "Bengkang II" for 5-7 days.
⑵ There are visible wound lesions in the foot of rotten axe, which are yellowish.
Prevention and control: use water quality improver once.Use iodine containing disinfectant twice, and then sprinkle soymilk and "Bengkang II" for 5-7 days.
⑶ The focus of red rot foot ulceration is pink.
Prevention and control: use water quality improver once.Use iodine containing disinfectant twice, and then sprinkle soymilk with "Bengkang II" bait for 5-7 days.
⑷ The liver color of gastroenteritis generally fades and stops eating. With the development of the disease, the crystal rod first becomes soft, easy to break, and then gradually disappears.
(5) Outer membrane (marginal membrane) Ulcer marginal membrane will shrink due to ulceration, and appear intermittently.If the sterilization is not strict during the graft operation, the outer membrane will fester and perforate.
Prevention and control: use water quality improver once.Use quaternary ammonium salt disinfectant for three times.
(6) Obvious inflammatory lesions can be seen in the adductor muscle, sometimes pink.
