Moderator: Farmers, friends, classmates: How are you! I am the host ***. Welcome to the program of “Ministry of Agriculture's Focus on the Promotion of 50 Agricultural Technology Series Broadcasting Seminars†hosted by me. Today, the topic of our lecture is "Thai Shellfish Breeding Technology." For this purpose, we invited Professor Zhang Guofan, a Chinese aquaculture expert from the Institute of Oceanology, Chinese Academy of Sciences. Professor Zhang Hello!
Professor Zhang: Hello host!
Moderator: China has more than 10,000 kilometers of shoreline, a vast coastal beach, and the resources of the shellfish and shellfish are also very rich. Can you give us an introduction to the following conditions in China's tidal shellfish culture?
Professor Zhang: OK. Tidal flat shellfish refers to sand argillaceous or muddy sandy bivalves and gastropods that are buried or buried within 20 meters of the intertidal, low-tide and subtidal zones. Tidal flatfish farming has a long history in China. The vast majority of the tidal flatfish shellfish cultured in China are bivalves, mainly including: mud louse, edgy burrow, burrowing cricket, common oyster, large bamboo cricket, long bamboo cricket, cricket, reticulata, barley, horned oyster, philippines, variegated oysters. There are only a few species of gastropods, such as mud snails, red snails, and snails. In recent years, the aquaculture development of the shellfish shellfish has been relatively rapid, the aquaculture area has been continuously expanding, and the farming species are gradually increasing. The aquaculture production is also increasing year by year. At present, shellfish shellfish farming has become a growing point in China's mariculture industry.
Moderator: What are the main ways that China currently farms shellfish shellfish?
Prof. Zhang: At present, China's tidal shellfish breeding is mainly carried out through beach stocking, nursing, enclosure, polyculture of shrimp and ponds, and salt field stocking.
Moderator: How are the shellfish seedlings grown in China cultivated?
Prof. Zhang: At present, the tidal shellfish species cultivated in China are mainly obtained from several ways:
1. Harvesting natural seedlings During the breeding and spawning season of shellfish, the natural seedlings that naturally adhere to the mudflats in the sea area are collected and temporarily raised for cultivation or transported to other tidal flats for stocking. Since the mudflat attached to the seedlings has not been artificially altered, the seedling density is not high and the yield is not high. Such as the grazing of the clams.
2. Semi-artificial seedlings in the sea area In the sea areas where shellfish are naturally breeding, seedlings are selected by artificial selection and construction of seedling plantation sites and “flat forecasting†according to their reproduction and seedling habits. This method is more advanced and superior than the collection of natural seedlings. Under normal conditions, a large number of seedlings can be successfully obtained. Such as the harvest of the seedlings.
3, outdoor earthen pond artificial breeding (semi-artificial nursery) This is to obtain a large number of mature eggs by pro-beta production, and the combination of insemination and development of planktonic larvae and then put it into open-air earthen pond, after careful management and artificial cultivation to Childhood. Due to its large area, it is difficult to wash eggs and remove predators. Therefore, the degree of manual control is poor. However, this method is simple and low-cost. It is a popular method of raising seedlings, and is also called semi-artificial breeding. Such as mud louse, clams, oysters, mud snails, etc. can be obtained through this method a large number of seedlings.
4. Indoor Artificial Seedling (Industrialized Artificial Seedling) It refers to the cultivation of seedlings from the selection of pro-shellfish, promotion of stocking, inducing emission of sperm and eggs, insemination, larval rearing, and seedling collection both indoors and under artificial control. method. Artificial seedlings can provide a certain number of shellfish seedlings, it has many advantages: pure seeds, high quality, basically the same size; early nursery, early picking seedlings, extending the growing period; can prevent predators, improve the survival rate; Can introduce and cultivate new varieties. At present, China has carried out indoor artificial seedlings for mudflats, clams, clams and mud snails.
In the long run, in the acquisition of these four kinds of seedlings, the two methods of semi-artificial breeding and industrialized artificial seedlings should be vigorously promoted.
Moderator: What are the main aspects of factory-based artificial nursery of shellfish shellfish?
Prof. Zhang: In recent years, China has successively carried out and tried some types of indoor artificial nursery in the production of shellfish shellfish culture, such as loach, four-cornered quail, clams, barley, cockroach, Xishi tongue, mud snail and so on. The artificial breeding of shellfish is a very technical production process. It includes site selection, scale design and equipment preparation prior to nursery production, selection of pro-shellworms in production, conservation, gonad ripening and oxytocinization, and artificial insemination. Many aspects such as egg washing and larval breeding, especially the cultivation of larvae, must be emphasized.
Moderator: Professor Zhang, how to build a nursery?
Professor Zhang: To build a nursery, we must first select the nursery site. The selection of nursery sites should be based on the overall planning requirements for the development of local aquaculture, adapting to local conditions, comprehensive analysis, and technical and economic feasibility studies, should choose: a sea area with good water quality, no pollution, high transparency and good salinity, At the same time, we must also pay attention to the convenience of transportation and the availability of fresh water. Secondly, the design scale of nursery sites should also be noted. The nursery nursery is divided into large, medium, and small nursery ponds based on the total effective water volume (m3) of nursery ponds. In general, 500 to 1000 m3 is a small field, 1000 to 2000 m3 is a medium field, and 2000 m3 or more is a large field. The size of the field should be set according to its own capabilities, and must not be blindly expanded. A good nursery should also have: nursery room, algae species room, bait room, pro-Bay temporary pool, boiler room, fan room, transformer room, pump room, sedimentation tank, sand filter, reservoir and other supporting facilities facility.
Moderator: In the artificial nursery, how to choose and hold pro-shellfish, how to mature pro-shelled gonads?
Professor Zhang: The quality of pro-being is one of the key factors for the success of nursery. Therefore, we must be careful about the choice of pro-shellfish. Individuals with large individuals, no injuries, good vigor, and mature gonads should be selected as pro-shellfish. Parents should be raised to a suitable density, adequate nutrition, and good water quality. Pro-shellfish before oxytocin, generally to promote gonads. For the bivalves, the pro-scallops can be kept in the pool for about one month before their spawning season, and the scallops' fullness and maturity can be promoted by changing the water and feeding the food organisms; Gastropods, because of their long breeding season, and most species can lay eggs multiple times, they can put pro-scallops into holding pools one week prior to their spawning, and promote pros by changing water and artificial feeding. The gonads are full and mature.
Moderator: How to artificially stimulate production of pro-shellfish?
Professor Zhang: Shellfish artificial oxytocin is mainly used in bivalves, and most of the gastropods do not require artificial oxytocin production. At present, there are three methods for inducing production in indoor artificial seedlings: physical, chemical and physical and chemical combinations.
(1) The physical method is commonly used variable temperature method: Through 3 ~ 4 °C temperature and repeated stimulation, promote its emission of eggs, such as burrowing, loach and so on.
Dry trunk water stimulation method: The gonad maturation of the parent bees is dried for a period of time, and then stimulated with running water, it can discharge sperm and eggs. This method has achieved good results in the production of oysters such as oyster clams, scallops, smuts, oysters, and szechuan tongues.
Dry, warming up and down the stimulation method: This method stimulates the intensity, can promote the large scale emission of eggs and oysters.
(2) Chemical method The gonads of pro-shellfish were injected with 0.2 to 0.5% of 0.2% ammonium seawater, and sperms and eggs were released within 20 minutes. Muddy production often used this method.
(3) physicochemical factor binding method for pro-shellfish injection of ammonium water, combined with cooling, running water can promote the emission of sperm and eggs in most individuals.
Moderator: How is artificial insemination and egg washing?
Prof. Zhang: When the pro-scallops remove the eggs, remove the pro-scallops, dilute the semen, and put the semen into the egg-filled pool in a certain amount. Stir well. This process is artificial insemination. Egg washing is the process of repeatedly washing the egg and fertilized eggs with seawater through a sieve and constantly changing the seawater. Egg washing is one of the very important steps in artificial shellfish breeding. The egg before fertilization and the fertilized egg after fertilization are washed repeatedly with seawater and continuously replaced with seawater. The egg washing after fertilization is more important. Through repeated washing and constantly changing seawater. Because shellfish emits fecal matter and mucus during the discharge of eggs. Therefore, eggs are sieved before fertilization. Washing eggs after fertilization is even more important. The reason is that by repeatedly washing and constantly changing seawater, excess sperm, immature eggs and egg water can be removed, which is beneficial to the development of embryos and can exclude the metabolites of fertilized eggs. Fertilized eggs remain in suspension and can effectively increase hatchability.
Moderator: What should be noted in larval rearing?
Professor Zhang: The larvae cultivation is the most critical link in the artificial breeding of shellfish, and it is also the link that determines the success of artificial breeding. Therefore, larval culture should be given enough attention. The larvae culture should mainly consider from the density of larvae culture, suitable bait types and bait concentrations, water temperature, salinity, light, dissolved oxygen and pH in seawater, protozoa infestation and bacterial diseases.
Whether the culture density of plankton larvae is appropriate or not will also directly affect the success or failure of artificial breeding. For bivalves, the individual larvae are small and, therefore, the culture density is generally high and may contain several waters per milliliter of water. However, for gastropods, the larval individuals are generally large, and the newly hatched larvae often have 200-300 microns. Therefore, the culture density cannot be high, and generally only a few zero points per milliliter of water can be.
The size, quality and quantity of bait in the shellfish artificial nursery are directly related to the success of nursery. Because the plankton larvae of shellfish are relatively small, they can only eat unicellular algae. Therefore, the choice of algae is very important. Generally, single-cell algae with small individuals, easy digestion, no toxicity, high nutritional value, rapid reproduction, and easy mass culture are selected. Usually golden algae, flat algae, and tiny diatoms are all good foods for the culture of shellfish larvae. Commonly used Zhanjiang fork algae, ball isochrysis, green Pavlova, green micrococcus, Qingdao large flat algae, Asia heart-shaped flat algae, new moon diamond-shaped algae heterophaga and so on. Many experiments have shown that in the culture of shellfish plankton larvae, mixed feeding with several kinds of algae is better than feeding with single algae. It is important to remember not to use already aged algae baits during nursery. Although the feed quality is good, if the amount of bait is not enough during the larval culture, it will also affect the survival and growth of the larvae. Therefore, in the production of shellfish nursery, the cultivation of large quantities of high-quality bait is very important work.
The ecological factors such as temperature, salinity, light, dissolved oxygen in seawater, and pH are also important for artificial shellfish breeding.
In general, the shellfish shell larvae also have a wide range of suitable temperature and salinity, as long as it is not a sudden change in environmental conditions, generally can be a good survival, growth and development.
Among the environmental factors, light is the most easily overlooked. However, in the artificial breeding process of shellfish, light is also an important factor affecting the larvae and juveniles and completing the morphological structure. Because both the trochophore larvae and the early stage larvae have obvious phototaxis, the metamorphosis stage faceplate larvae and juveniles show significant backlighting. In view of this, the lighting in the nursery should strive to be even; when the attachment is abnormal, the shadow of the attachments should be increased as much as possible; the cultivation of the juvenile period can appropriately increase the hours of illumination.
In the artificial breeding of shellfish, the dissolved oxygen in water is generally maintained at more than 4mg/l, and the allowable range of PH is generally 7.5~8.4.
The emergence of protozoa in nursery water indicates that the water quality of the nursery has begun to deteriorate. Not only does it invade the larvae, but the secretions can cause water spoilage, causing larvae to die. The use of inverted pool filtration, drug killing, and combination of prevention and control are commonly used for protozoa. For the prevention and control of bacterial diseases, UV radiation sterilization, ozone sterilization, antibiotic control, and chlorination or potassium permanganate disinfection are mainly used.
Moderator: Prof. Zhang, what are the different technical points for shellfish outdoor artificial nursery and indoor artificial nursery?
Professor Zhang: Outdoor artificial seedlings, also known as artificial seedlings in earthen ponds, are carried out in outdoor earthen ponds. Compared with indoor artificial seedlings, the first step in artificial seedlings in earthen ponds is to attach great importance to the construction of outdoor earthen ponds. The earthen ponds should be selected in the inner bay beach that is not threatened by typhoon flooding, pollution, sand and mud (80% sand, 20% mud), and large and small tides. The area of ​​earthen ponds should be adapted to the local conditions, and it is generally appropriate to use about 5 mu. The shore of the earthen pond is best made of stones, and the water level in the earthen ponds is determined according to the kind of species raised, and should generally be more than 1 meter. It is very important to set up a gate with a fine mesh screen mesh bag on the side of the earth pool. The gates can be used for seawater ingress, excavation, and for water production. Net bags can prevent pests and large plankton from entering the earthen ponds. At the same time, the net bags can prevent the larvae from floating out. The use of discarded shrimp ponds as shellfish nursery ponds is also an ideal place. For larger shrimp ponds, it can be divided into several plots.
In addition, in the earthen pond nursery, the pro-bezoar production method mainly adopts the dry-drying and water-supply stimulation method. The technical point is: generally during the tide, the pro-bei shellfish will be dried first, and the shellfish will be dry in different time. If it is dry, it needs to dry for 6~8 hours. The oysters need to be dry for 15 to 18 hours, and the long bamboo culm is about 5 hours. Then the water can be discharged after stimulating for 2 to 3 hours.
Third, unlike indoor artificial seedlings, the sedimentary sludge in the original earthen ponds should be removed before the earthen ponds are raised and then the sand should be loosened and flattened to prepare for the attachment of the larvae. Ten days prior to nursery, the enemy’s organisms in the pond are removed with drugs. In earthen pond breeding, during the cultivation of planktonic larvae, water quality can be controlled by gradually adding new seawater every day. When the larvae have become metamorphosed, they can be replaced by water and water to maintain the freshness of the water. Similarly, the quality and quantity of bait is also the key to the survival and growth of larvae and juveniles in the earth pond. In order to make the density of phytoplankton in the earthen pond suitable, it can be controlled by a small amount of regular fertilization. In addition, in order to supplement the type and quantity of food organisms suitable for the larvae, “oil sludge†may be scraped off the surface of the mudflat or artificially cultivated into some earthworms.
Moderator: What special attention should be paid to the development of shellfish shellfish?
Professor Zhang: The development of tidal flat shellfish should be considered from the following aspects:
1, choose the breeding site and finishing generally choose calm, smooth tide beach. The beach should be flat, wide and slightly inclined, and both the large and small tides can be submerged and dried. Shrimp ponds, tidal creeks, and other places with muddy sediments can be used as a breeding ground. Tidal flats of shellfish cultivation sites are dominated by sand and mud, and the content of sand should be above 60%. Of course, the sand content should also be determined depending on the type of farming. In order to ensure that the seedlings have a good habitat, shrimp ponds, paddies, oysters, and shoals should be loosened before they are sown to facilitate the seedlings to infiltrate into the surface. If there is a depression, it should be leveled to prevent the temperature of the falling tide from rising in summer. High causes seedlings to die. In addition, it is also very important to remove predators such as jade snails, snakes, sea lice and crabs before they are broadcast.
2. There are two kinds of seeding methods for sowing shellfish seedlings. One is water sowing. When the seawater rises at high tide, the seedlings are evenly thrown into the water with shovels. The survival rate of seedling seedlings is relatively high. The disadvantage is that the seeds are not easily spread evenly due to the influence of tides or winds; the other method is dry seeding, that is, when the beach surface is exposed, the seeds are spread evenly on the beach surface. Generally, the tidewater is generally selected at low tide in the morning and in the evening. This should be done, but it should be noted that the time that the seeds are dried on the beach is not too long. The amount and density of sowing must take into account the texture of the water species and the texture of the beach and other shellfish resources. It should also be based on seed size and stocking area. Under normal circumstances, the food in the water is rich in organisms, and the texture can be loose and the seedlings can be appropriately broadcasted; otherwise, the seedlings can be sown. Large-size seeds can be sown; small-sized seeds can be sown. The density of sows in the low tide area may be greater, while that in the middle and high tide areas is less.
3. After the cultivated seedlings have been planted, whether they can achieve bumper harvests and the management is also very important. Many experiences have shown that a good maritime safety order is an important part of the good economic benefits of shellfish and aquaculture. Therefore, during the fertility-enhancing process of shellfish shellfish, a beach care team that can work hard and have a strong sense of responsibility is a guarantee for the success of the breeding and aquaculture operations. In addition to maintaining the tidal flat order, this team must also engage in daily technical aspects. Management, including regular measurement of temperature, salinity, regular sampling observation and measurement shell shell length, shell height, shell width, weight, production records, frequent inspection of the breeding area, pay attention to the leakage of the dam, cofferdam, and seine, Precautionary organisms in the breeding area are regularly controlled and abnormal conditions are found and reported and handled in a timely manner.
Moderator: Prof. Zhang, what suggestions do you have for China's tidal shellfish breeding?
Prof. Zhang: Tidal flatfish shellfish generally have high-protein, low-fat, delicious taste, and easy-to-harvest properties. They are widely loved by the public and their demand has been increasing in recent years. In order to achieve the sustainable use of resources, it is necessary to protect the resources while actively promoting the production of shellfish shellfish. This needs to work from the following aspects:
1. Strengthen the management of seedlings;
2, the provisions of the capture specifications;
3. Delimit the no-catch area;
4, the provisions of the arrest period;
5. Establish nursing areas;
6, control the catch;
7. Adding seedlings to the sea area in due course;
8, open up new seedlings and cultivated areas.
Professor Zhang: Hello host!
Moderator: China has more than 10,000 kilometers of shoreline, a vast coastal beach, and the resources of the shellfish and shellfish are also very rich. Can you give us an introduction to the following conditions in China's tidal shellfish culture?
Professor Zhang: OK. Tidal flat shellfish refers to sand argillaceous or muddy sandy bivalves and gastropods that are buried or buried within 20 meters of the intertidal, low-tide and subtidal zones. Tidal flatfish farming has a long history in China. The vast majority of the tidal flatfish shellfish cultured in China are bivalves, mainly including: mud louse, edgy burrow, burrowing cricket, common oyster, large bamboo cricket, long bamboo cricket, cricket, reticulata, barley, horned oyster, philippines, variegated oysters. There are only a few species of gastropods, such as mud snails, red snails, and snails. In recent years, the aquaculture development of the shellfish shellfish has been relatively rapid, the aquaculture area has been continuously expanding, and the farming species are gradually increasing. The aquaculture production is also increasing year by year. At present, shellfish shellfish farming has become a growing point in China's mariculture industry.
Moderator: What are the main ways that China currently farms shellfish shellfish?
Prof. Zhang: At present, China's tidal shellfish breeding is mainly carried out through beach stocking, nursing, enclosure, polyculture of shrimp and ponds, and salt field stocking.
Moderator: How are the shellfish seedlings grown in China cultivated?
Prof. Zhang: At present, the tidal shellfish species cultivated in China are mainly obtained from several ways:
1. Harvesting natural seedlings During the breeding and spawning season of shellfish, the natural seedlings that naturally adhere to the mudflats in the sea area are collected and temporarily raised for cultivation or transported to other tidal flats for stocking. Since the mudflat attached to the seedlings has not been artificially altered, the seedling density is not high and the yield is not high. Such as the grazing of the clams.
2. Semi-artificial seedlings in the sea area In the sea areas where shellfish are naturally breeding, seedlings are selected by artificial selection and construction of seedling plantation sites and “flat forecasting†according to their reproduction and seedling habits. This method is more advanced and superior than the collection of natural seedlings. Under normal conditions, a large number of seedlings can be successfully obtained. Such as the harvest of the seedlings.
3, outdoor earthen pond artificial breeding (semi-artificial nursery) This is to obtain a large number of mature eggs by pro-beta production, and the combination of insemination and development of planktonic larvae and then put it into open-air earthen pond, after careful management and artificial cultivation to Childhood. Due to its large area, it is difficult to wash eggs and remove predators. Therefore, the degree of manual control is poor. However, this method is simple and low-cost. It is a popular method of raising seedlings, and is also called semi-artificial breeding. Such as mud louse, clams, oysters, mud snails, etc. can be obtained through this method a large number of seedlings.
4. Indoor Artificial Seedling (Industrialized Artificial Seedling) It refers to the cultivation of seedlings from the selection of pro-shellfish, promotion of stocking, inducing emission of sperm and eggs, insemination, larval rearing, and seedling collection both indoors and under artificial control. method. Artificial seedlings can provide a certain number of shellfish seedlings, it has many advantages: pure seeds, high quality, basically the same size; early nursery, early picking seedlings, extending the growing period; can prevent predators, improve the survival rate; Can introduce and cultivate new varieties. At present, China has carried out indoor artificial seedlings for mudflats, clams, clams and mud snails.
In the long run, in the acquisition of these four kinds of seedlings, the two methods of semi-artificial breeding and industrialized artificial seedlings should be vigorously promoted.
Moderator: What are the main aspects of factory-based artificial nursery of shellfish shellfish?
Prof. Zhang: In recent years, China has successively carried out and tried some types of indoor artificial nursery in the production of shellfish shellfish culture, such as loach, four-cornered quail, clams, barley, cockroach, Xishi tongue, mud snail and so on. The artificial breeding of shellfish is a very technical production process. It includes site selection, scale design and equipment preparation prior to nursery production, selection of pro-shellworms in production, conservation, gonad ripening and oxytocinization, and artificial insemination. Many aspects such as egg washing and larval breeding, especially the cultivation of larvae, must be emphasized.
Moderator: Professor Zhang, how to build a nursery?
Professor Zhang: To build a nursery, we must first select the nursery site. The selection of nursery sites should be based on the overall planning requirements for the development of local aquaculture, adapting to local conditions, comprehensive analysis, and technical and economic feasibility studies, should choose: a sea area with good water quality, no pollution, high transparency and good salinity, At the same time, we must also pay attention to the convenience of transportation and the availability of fresh water. Secondly, the design scale of nursery sites should also be noted. The nursery nursery is divided into large, medium, and small nursery ponds based on the total effective water volume (m3) of nursery ponds. In general, 500 to 1000 m3 is a small field, 1000 to 2000 m3 is a medium field, and 2000 m3 or more is a large field. The size of the field should be set according to its own capabilities, and must not be blindly expanded. A good nursery should also have: nursery room, algae species room, bait room, pro-Bay temporary pool, boiler room, fan room, transformer room, pump room, sedimentation tank, sand filter, reservoir and other supporting facilities facility.
Moderator: In the artificial nursery, how to choose and hold pro-shellfish, how to mature pro-shelled gonads?
Professor Zhang: The quality of pro-being is one of the key factors for the success of nursery. Therefore, we must be careful about the choice of pro-shellfish. Individuals with large individuals, no injuries, good vigor, and mature gonads should be selected as pro-shellfish. Parents should be raised to a suitable density, adequate nutrition, and good water quality. Pro-shellfish before oxytocin, generally to promote gonads. For the bivalves, the pro-scallops can be kept in the pool for about one month before their spawning season, and the scallops' fullness and maturity can be promoted by changing the water and feeding the food organisms; Gastropods, because of their long breeding season, and most species can lay eggs multiple times, they can put pro-scallops into holding pools one week prior to their spawning, and promote pros by changing water and artificial feeding. The gonads are full and mature.
Moderator: How to artificially stimulate production of pro-shellfish?
Professor Zhang: Shellfish artificial oxytocin is mainly used in bivalves, and most of the gastropods do not require artificial oxytocin production. At present, there are three methods for inducing production in indoor artificial seedlings: physical, chemical and physical and chemical combinations.
(1) The physical method is commonly used variable temperature method: Through 3 ~ 4 °C temperature and repeated stimulation, promote its emission of eggs, such as burrowing, loach and so on.
Dry trunk water stimulation method: The gonad maturation of the parent bees is dried for a period of time, and then stimulated with running water, it can discharge sperm and eggs. This method has achieved good results in the production of oysters such as oyster clams, scallops, smuts, oysters, and szechuan tongues.
Dry, warming up and down the stimulation method: This method stimulates the intensity, can promote the large scale emission of eggs and oysters.
(2) Chemical method The gonads of pro-shellfish were injected with 0.2 to 0.5% of 0.2% ammonium seawater, and sperms and eggs were released within 20 minutes. Muddy production often used this method.
(3) physicochemical factor binding method for pro-shellfish injection of ammonium water, combined with cooling, running water can promote the emission of sperm and eggs in most individuals.
Moderator: How is artificial insemination and egg washing?
Prof. Zhang: When the pro-scallops remove the eggs, remove the pro-scallops, dilute the semen, and put the semen into the egg-filled pool in a certain amount. Stir well. This process is artificial insemination. Egg washing is the process of repeatedly washing the egg and fertilized eggs with seawater through a sieve and constantly changing the seawater. Egg washing is one of the very important steps in artificial shellfish breeding. The egg before fertilization and the fertilized egg after fertilization are washed repeatedly with seawater and continuously replaced with seawater. The egg washing after fertilization is more important. Through repeated washing and constantly changing seawater. Because shellfish emits fecal matter and mucus during the discharge of eggs. Therefore, eggs are sieved before fertilization. Washing eggs after fertilization is even more important. The reason is that by repeatedly washing and constantly changing seawater, excess sperm, immature eggs and egg water can be removed, which is beneficial to the development of embryos and can exclude the metabolites of fertilized eggs. Fertilized eggs remain in suspension and can effectively increase hatchability.
Moderator: What should be noted in larval rearing?
Professor Zhang: The larvae cultivation is the most critical link in the artificial breeding of shellfish, and it is also the link that determines the success of artificial breeding. Therefore, larval culture should be given enough attention. The larvae culture should mainly consider from the density of larvae culture, suitable bait types and bait concentrations, water temperature, salinity, light, dissolved oxygen and pH in seawater, protozoa infestation and bacterial diseases.
Whether the culture density of plankton larvae is appropriate or not will also directly affect the success or failure of artificial breeding. For bivalves, the individual larvae are small and, therefore, the culture density is generally high and may contain several waters per milliliter of water. However, for gastropods, the larval individuals are generally large, and the newly hatched larvae often have 200-300 microns. Therefore, the culture density cannot be high, and generally only a few zero points per milliliter of water can be.
The size, quality and quantity of bait in the shellfish artificial nursery are directly related to the success of nursery. Because the plankton larvae of shellfish are relatively small, they can only eat unicellular algae. Therefore, the choice of algae is very important. Generally, single-cell algae with small individuals, easy digestion, no toxicity, high nutritional value, rapid reproduction, and easy mass culture are selected. Usually golden algae, flat algae, and tiny diatoms are all good foods for the culture of shellfish larvae. Commonly used Zhanjiang fork algae, ball isochrysis, green Pavlova, green micrococcus, Qingdao large flat algae, Asia heart-shaped flat algae, new moon diamond-shaped algae heterophaga and so on. Many experiments have shown that in the culture of shellfish plankton larvae, mixed feeding with several kinds of algae is better than feeding with single algae. It is important to remember not to use already aged algae baits during nursery. Although the feed quality is good, if the amount of bait is not enough during the larval culture, it will also affect the survival and growth of the larvae. Therefore, in the production of shellfish nursery, the cultivation of large quantities of high-quality bait is very important work.
The ecological factors such as temperature, salinity, light, dissolved oxygen in seawater, and pH are also important for artificial shellfish breeding.
In general, the shellfish shell larvae also have a wide range of suitable temperature and salinity, as long as it is not a sudden change in environmental conditions, generally can be a good survival, growth and development.
Among the environmental factors, light is the most easily overlooked. However, in the artificial breeding process of shellfish, light is also an important factor affecting the larvae and juveniles and completing the morphological structure. Because both the trochophore larvae and the early stage larvae have obvious phototaxis, the metamorphosis stage faceplate larvae and juveniles show significant backlighting. In view of this, the lighting in the nursery should strive to be even; when the attachment is abnormal, the shadow of the attachments should be increased as much as possible; the cultivation of the juvenile period can appropriately increase the hours of illumination.
In the artificial breeding of shellfish, the dissolved oxygen in water is generally maintained at more than 4mg/l, and the allowable range of PH is generally 7.5~8.4.
The emergence of protozoa in nursery water indicates that the water quality of the nursery has begun to deteriorate. Not only does it invade the larvae, but the secretions can cause water spoilage, causing larvae to die. The use of inverted pool filtration, drug killing, and combination of prevention and control are commonly used for protozoa. For the prevention and control of bacterial diseases, UV radiation sterilization, ozone sterilization, antibiotic control, and chlorination or potassium permanganate disinfection are mainly used.
Moderator: Prof. Zhang, what are the different technical points for shellfish outdoor artificial nursery and indoor artificial nursery?
Professor Zhang: Outdoor artificial seedlings, also known as artificial seedlings in earthen ponds, are carried out in outdoor earthen ponds. Compared with indoor artificial seedlings, the first step in artificial seedlings in earthen ponds is to attach great importance to the construction of outdoor earthen ponds. The earthen ponds should be selected in the inner bay beach that is not threatened by typhoon flooding, pollution, sand and mud (80% sand, 20% mud), and large and small tides. The area of ​​earthen ponds should be adapted to the local conditions, and it is generally appropriate to use about 5 mu. The shore of the earthen pond is best made of stones, and the water level in the earthen ponds is determined according to the kind of species raised, and should generally be more than 1 meter. It is very important to set up a gate with a fine mesh screen mesh bag on the side of the earth pool. The gates can be used for seawater ingress, excavation, and for water production. Net bags can prevent pests and large plankton from entering the earthen ponds. At the same time, the net bags can prevent the larvae from floating out. The use of discarded shrimp ponds as shellfish nursery ponds is also an ideal place. For larger shrimp ponds, it can be divided into several plots.
In addition, in the earthen pond nursery, the pro-bezoar production method mainly adopts the dry-drying and water-supply stimulation method. The technical point is: generally during the tide, the pro-bei shellfish will be dried first, and the shellfish will be dry in different time. If it is dry, it needs to dry for 6~8 hours. The oysters need to be dry for 15 to 18 hours, and the long bamboo culm is about 5 hours. Then the water can be discharged after stimulating for 2 to 3 hours.
Third, unlike indoor artificial seedlings, the sedimentary sludge in the original earthen ponds should be removed before the earthen ponds are raised and then the sand should be loosened and flattened to prepare for the attachment of the larvae. Ten days prior to nursery, the enemy’s organisms in the pond are removed with drugs. In earthen pond breeding, during the cultivation of planktonic larvae, water quality can be controlled by gradually adding new seawater every day. When the larvae have become metamorphosed, they can be replaced by water and water to maintain the freshness of the water. Similarly, the quality and quantity of bait is also the key to the survival and growth of larvae and juveniles in the earth pond. In order to make the density of phytoplankton in the earthen pond suitable, it can be controlled by a small amount of regular fertilization. In addition, in order to supplement the type and quantity of food organisms suitable for the larvae, “oil sludge†may be scraped off the surface of the mudflat or artificially cultivated into some earthworms.
Moderator: What special attention should be paid to the development of shellfish shellfish?
Professor Zhang: The development of tidal flat shellfish should be considered from the following aspects:
1, choose the breeding site and finishing generally choose calm, smooth tide beach. The beach should be flat, wide and slightly inclined, and both the large and small tides can be submerged and dried. Shrimp ponds, tidal creeks, and other places with muddy sediments can be used as a breeding ground. Tidal flats of shellfish cultivation sites are dominated by sand and mud, and the content of sand should be above 60%. Of course, the sand content should also be determined depending on the type of farming. In order to ensure that the seedlings have a good habitat, shrimp ponds, paddies, oysters, and shoals should be loosened before they are sown to facilitate the seedlings to infiltrate into the surface. If there is a depression, it should be leveled to prevent the temperature of the falling tide from rising in summer. High causes seedlings to die. In addition, it is also very important to remove predators such as jade snails, snakes, sea lice and crabs before they are broadcast.
2. There are two kinds of seeding methods for sowing shellfish seedlings. One is water sowing. When the seawater rises at high tide, the seedlings are evenly thrown into the water with shovels. The survival rate of seedling seedlings is relatively high. The disadvantage is that the seeds are not easily spread evenly due to the influence of tides or winds; the other method is dry seeding, that is, when the beach surface is exposed, the seeds are spread evenly on the beach surface. Generally, the tidewater is generally selected at low tide in the morning and in the evening. This should be done, but it should be noted that the time that the seeds are dried on the beach is not too long. The amount and density of sowing must take into account the texture of the water species and the texture of the beach and other shellfish resources. It should also be based on seed size and stocking area. Under normal circumstances, the food in the water is rich in organisms, and the texture can be loose and the seedlings can be appropriately broadcasted; otherwise, the seedlings can be sown. Large-size seeds can be sown; small-sized seeds can be sown. The density of sows in the low tide area may be greater, while that in the middle and high tide areas is less.
3. After the cultivated seedlings have been planted, whether they can achieve bumper harvests and the management is also very important. Many experiences have shown that a good maritime safety order is an important part of the good economic benefits of shellfish and aquaculture. Therefore, during the fertility-enhancing process of shellfish shellfish, a beach care team that can work hard and have a strong sense of responsibility is a guarantee for the success of the breeding and aquaculture operations. In addition to maintaining the tidal flat order, this team must also engage in daily technical aspects. Management, including regular measurement of temperature, salinity, regular sampling observation and measurement shell shell length, shell height, shell width, weight, production records, frequent inspection of the breeding area, pay attention to the leakage of the dam, cofferdam, and seine, Precautionary organisms in the breeding area are regularly controlled and abnormal conditions are found and reported and handled in a timely manner.
Moderator: Prof. Zhang, what suggestions do you have for China's tidal shellfish breeding?
Prof. Zhang: Tidal flatfish shellfish generally have high-protein, low-fat, delicious taste, and easy-to-harvest properties. They are widely loved by the public and their demand has been increasing in recent years. In order to achieve the sustainable use of resources, it is necessary to protect the resources while actively promoting the production of shellfish shellfish. This needs to work from the following aspects:
1. Strengthen the management of seedlings;
2, the provisions of the capture specifications;
3. Delimit the no-catch area;
4, the provisions of the arrest period;
5. Establish nursing areas;
6, control the catch;
7. Adding seedlings to the sea area in due course;
8, open up new seedlings and cultivated areas.
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