A method for promoting gonadal maturation of Crassostrea hongkongensis based on circulating water

Abstract

The present invention relates to a method for promoting the gonadal maturation of Hong Kong oysters based on circulating water, belonging to the technical field of shellfish parent cultivation. The broodstock to be promoted for maturation is placed in a cultivation pond, and the cultivation density of the broodstock to be promoted for maturation in the cultivation pond is 50 - 60 individuals / m². The tail water of a shrimp pond after salinity adjustment and flowing is introduced into the cultivation pond, the salinity of the tail water of the shrimp pond after salinity adjustment is 13 - 15‰, and the temperature of the tail water of the shrimp pond after salinity adjustment in the cultivation pond is 24 - 26°C. The broodstock to be promoted for maturation is cultivated until the gonadal development maturity reaches stage V. By controlling salinity, temperature and cultivating with circulating water, the gonadal maturation time is advanced by 2 months, and seedling cultivation can be carried out in March. By producing early seedlings, the seedling growth is fast, the benefit is high, and the artificial seedling cultivation time cycle is extended, increasing the economic benefit.

Description

Technical Field

[0001] The present invention relates to the technical field of shellfish parent cultivation, and particularly to a method for promoting gonadal maturation of Crassostrea hongkongensis based on recirculating water. Background Art

[0002] For a long time, the source of Crassostrea hongkongensis seedlings mainly relies on natural seeding in the sea area. However, the collection of natural seedlings is affected by many factors such as climate, environment, and germplasm resources. In recent years, the quality and quantity of seeding have been extremely unstable, and it can no longer meet the seedling demand of the Crassostrea hongkongensis aquaculture industry. Due to the shortage of high-quality Crassostrea hongkongensis seedlings, the artificial breeding technology of Crassostrea hongkongensis has developed vigorously, and the supply of seed sources is the key to the success of breeding. Crassostrea hongkongensis belongs to the high-temperature and low-salt type of oyster varieties, and its gonadal development matures relatively late. In late May of each year, the gonadal maturation period for breeding is relatively short, generally 4 months, and the gonadal maturation cycle of Crassostrea hongkongensis in the sea area is extremely unstable. During the rainy season, the gonads of mature oysters are easily emptied, resulting in unstable supply of seed sources for breeding; on the other hand, the quality of gametes naturally matured in the sea area varies, and the overall breeding effect is not good, restricting the large-scale breeding of high-quality Crassostrea hongkongensis seedlings. In view of this, it is necessary to provide a method for promoting gonadal maturation of Crassostrea hongkongensis based on recirculating water to solve the deficiencies of the existing technology. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for promoting gonadal maturation of Crassostrea hongkongensis based on recirculating water in view of the current situation of late gonadal development, unstable supply, and uneven gamete quality of existing seed sources.

[0004] The technical solution of the present invention to solve the above technical problems is as follows: providing a method for promoting gonadal maturation of Crassostrea hongkongensis based on recirculating water, including the following steps:

[0005] Put the broodstock to be promoted for maturation into the cultivation pond, and the cultivation density of the broodstock to be promoted for maturation in the cultivation pond is 50 - 60 individuals / m 2 ; Introduce the flowing tail water of the shrimp pond with adjusted salinity into the cultivation pond, the salinity of the adjusted tail water of the shrimp pond is 13 - 15‰, and the temperature of the adjusted tail water of the shrimp pond in the cultivation pond is 24 - 26°C;

[0006] Cultivate the broodstock to be promoted for maturation until the gonadal development maturity reaches stage V.

[0007] Among them, the gonadal development of oysters has a total of stages I - V, and the gonads of oysters with gonadal development reaching stage V are fully developed and mature. The present invention can be used for promoting gonadal maturation of Crassostrea hongkongensis parents in the coastal areas of South China.

[0008] On the basis of the above technical solution, the present invention can also be improved as follows.

[0009] Further, the salinity of the shrimp pond tail water after salinity adjustment is 15‰, and the temperature of the shrimp pond tail water after salinity adjustment in the cultivation pond is 25°C.

[0010] Further, the time required to cultivate the broodstock to be promoted until the gonad development maturity reaches stage V is 10 - 30 days.

[0011] Further, each of the broodstock to be promoted is a Hong Kong oyster with pure germplasm, a shell height greater than or equal to 10 cm, a wet weight of more than 150 g, a regular shell shape, a strong shell opening and closing force, and plump meat; the gonad of each of the broodstock to be promoted has developed to above stage II. Further, the broodstock to be promoted is knocked into individual individuals, the attachments on its surface are removed, and it is washed clean with sand-filtered seawater.

[0012] Further, the broodstock to be promoted is placed into the cultivation pond through a foam floating frame, so that each foam floating frame containing the broodstock to be promoted floats on the shrimp pond tail water after salinity adjustment in the cultivation pond.

[0013] In order to provide the best feeding environment for each broodstock, the cleaned broodstock to be promoted are arranged in a single layer with the front end and the rear end of the shell of adjacent individuals side by side. At the same time, the buoyancy requirement of each foam floating frame is greater than the total weight of the broodstock to be promoted contained therein, so that the floating frame containing the broodstock floats on the water surface, and the feces of the broodstock to be promoted are discharged to the bottom of the pond.

[0014] Further, the depth of the shrimp pond tail water after salinity adjustment in the cultivation pond is 60 - 80 cm, and the dissolved oxygen in the shrimp pond tail water after salinity adjustment in the cultivation pond is ≥5 mg / L. By continuously aerating the whole pond, the dissolved oxygen in the shrimp pond tail water after salinity adjustment in the cultivation pond is made ≥5 mg / L.

[0015] Further, the cultivation pond includes an inlet and an outlet. At the inlet, the shrimp pond tail water is mixed with fresh water to obtain the shrimp pond tail water after salinity adjustment.

[0016] Among them, the shrimp pond tail water refers to the seawater discharged from the shrimp pond into the earthen pond. Since a large amount of bait is fed during the shrimp farming process, there will be organic matters such as residual bait and shrimp feces, making the seawater highly eutrophic, containing a large number of diversified unicellular algae, bioflocs and organic particles, and being rich in nutrients, which is a good natural bait for oyster fattening and maturation promotion.

[0017] Further, the inlet and the outlet are located on the diagonal line of the cultivation pond.

[0018] Further, it also includes daily management, and the daily management specifically includes the following steps: controlling the light of the cultivation pond through a sunshade net to be 200-500 lux, checking the vitality of the parent oysters to be promoted at least once a day, picking out the dead parent oysters to be promoted, and cleaning the cultivation pond at least once every 3 days.

[0019] Through indoor salt control, temperature control and cultivation with flowing shrimp pond tail water, the present invention solves the problems of late gonadal development of broodstock for large-scale breeding of artificial seedlings of Crassostrea hongkongensis, unstable supply, uneven gamete maturity, etc.; through this method, the gonads of Crassostrea hongkongensis can mature in advance, advancing the artificial seedling breeding time of Crassostrea hongkongensis. It not only extends the breeding season of Crassostrea hongkongensis, but also improves the success rate of artificial seedling breeding, supplies high-quality seedlings for the industry, and moreover, the growth rate of the intermediate culture after the early seedlings are released from the pond is fast, and they can grow into large-scale seedlings in the same year, effectively shortening the culture cycle and reducing the culture risk, thereby ensuring the healthy, efficient and sustainable development of the Crassostrea hongkongensis aquaculture industry.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) Through salt control, temperature control and cultivation with flowing shrimp pond tail water, the present invention advances the gonad maturation time by 2 months, and seedling breeding can be carried out in March; by releasing early seedlings, the seedlings grow fast, with high benefits, and the artificial seedling breeding time cycle is extended, increasing economic benefits.

[0022] (2) The present invention cultivates through circulating shrimp pond tail water, without the need to feed biological baits for cultivation; and through the filtering and feeding action of the parent oysters to be promoted, it can also purify the aquaculture tail water, playing a role in water quality purification, with good ecological benefits.

[0023] (3) Through the inventive method, it is possible to stably provide breeding broodstock as needed, and the gonads of the broodstock have good synchronous maturity, high gamete quality, improving the success rate of seedling breeding and having good seedling breeding effects.

[0024] (4) The operation method of the present invention is simple, with low cost, strong practicability, good ecological and economic benefits, and is suitable for large-scale popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a diagram of oysters before cultivation of the present invention;

[0026] Figure 2 It is a diagram after conventional cultivation of the present invention;

[0027] Figure 3 It is a diagram after cultivation by the method of Example 1 of the present invention;

[0028] Figure 4 It is a diagram of a gonad section (stage II) before cultivation of the present invention;

[0029] Figure 5 Figure of gonad section (Phase III) of Comparative Example 1 of the present invention;

[0030] Figure 6 Figure of gonad section (Phase V) of Example 1 of the present invention;

[0031] Figure 7 Figure of the cultivation site of the present invention. Detailed implementation manners

[0032] The principles and features of the present invention will be described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. For those not specifying specific techniques or conditions in the examples, the techniques or conditions described in the literature in this field or according to the product specifications are followed. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be purchased through regular channels.

[0033] The shrimp pond tail water used below refers to the seawater discharged from the shrimp pond into the earthen pond. Since a large amount of bait is fed during the shrimp farming process, there will be organic matters such as residual bait and shrimp feces, making the seawater highly eutrophic, containing a large number of diversified unicellular algae, bioflocs and organic particles, rich in nutrients, and being a good natural bait for oyster fattening and ripening.

[0034] Example 1

[0035] This example relates to a method for promoting the gonad ripening of Crassostrea hongkongensis based on circulating water (as Figure 7 ), including the following steps:

[0036] Step 1: Select Crassostrea hongkongensis broodstock, break them into single individuals and clean them thoroughly.

[0037] On March 5, 2022, in the sea area of Maowei Sea in Qinzhou City, Guangxi, 300 catties of Crassostrea hongkongensis broodstock with pure germplasm, shell height ≥ 10 cm, wet weight over 150 g, regular shell shape, strong shell opening and closing, and plump meat were selected as the broodstock to be promoted for ripening and transported back to the Crassostrea hongkongensis breeding farm in Beihai, Guangxi. After temporarily raising with seawater prepared according to the sea area salinity of 23‰ for 24 hours, the broodstock were broken into single individuals, the attachments on the shell surface were removed, and they were washed clean with sand-filtered seawater. The gonad tissue section detected that the gonad development reached Phase II (as Figure 1 and 4 ).

[0038] Step 2: Use foam floating frames to pack the broodstock separately

[0039] The 300 catties of cleaned broodstock were arranged side by side with the front end and the rear end of the shell of adjacent individuals and loaded into self-made floating frames, and each floating frame containing the broodstock was suspended on the water surface to facilitate the feeding and defecation of the broodstock. The cultivation density was 60 per m 2 .

[0040] Step 3: Recycling of the shrimp pond tail water

[0041] Pump the shrimp pond tail water that has been sedimented in the earthen pond sedimentation tank into the cultivation pond filled with broodstock in a cyclic manner. The water inlet and outlet of the cultivation pond should be at the two endpoints of the farthest diagonal of the pond. Adjust the pipe diameter length of the water outlet to keep the water depth at 80 cm. Continuously aerate the whole pond during the cultivation period to keep the dissolved oxygen greater than 5 mg / L; the flow rate of the shrimp pond tail water flowing in the cultivation pond is 5 cm / s.

[0042] Among them, for the regulation of the salinity and temperature of the shrimp pond tail water recycling:

[0043] When it is monitored that the salinity of the shrimp pond tail water is 28‰, continuously add fresh water to the cultivation pond. The fresh water inlet and the shrimp pond tail water inlet are placed at the same position. Adjust the water inflow of the tail water and fresh water to control the overall salinity of the cultivation pond at 15‰. The seawater temperature in the cultivation pond is continuously controlled at 25°C through the boiler heating pipe.

[0044] Step 4: Daily management

[0045] In order to better control the temperature, close the cultivation pond workshop, regulate the light to 400 lux through the sunshade net, check the vitality of the broodstock to be promoted to maturity every day, pick out the dead individuals, clean the whole pond once every 3 days, and regularly take samples to open the shells to monitor the gonad development degree. After 20 days of cultivation with the cyclic shrimp pond tail water under salinity and temperature control, open the shells for visual inspection and find that the gonads of the broodstock are fully developed (as Figure 3 ), the gamete development level is high under microscopic examination, and further tissue section detection shows that the gonad development maturity has reached stage V (as Figure 6 ), the synchronous maturity rate is as high as 91.5%, and the broodstock can be used for seedling cultivation.

[0046] Example 2

[0047] Adopt the steps described in Example 1 for cultivation. The difference from Example 1 is that: on March 25, 2022, in this example, 200 catties of broodstock were selected, and seedling production was carried out at the Guangxi Beihai Hong Kong Oyster Breeding Farm. The fertilization rate of gametes was 93.2%, the hatching rate was 75.8%, and a total of 500 million D-shaped larvae were hatched. After 13 days of cultivation, it reached the metamorphosis stage of eyed larvae, and the larvae began to attach. The survival rate of larvae during the planktonic larval stage was 85.7%, and a total of 165,000 strings of attached seedlings were obtained. The seedlings were out of the pond on April 15.

[0048] Comparative Example 1

[0049] Compared with Example 1, the difference is that: in this comparative example, cultivation without temperature control, salinity control, and circulating water feeding was carried out.

[0050] Specifically, it includes the following steps: On March 5, 2022, in the waters of Maoweihai in Qinzhou City, Guangxi, 100 catties of Crassostrea hongkongensis broodstock with pure germplasm, shell height ≥ 10 cm, wet weight over 150 g, regular shell shape, strong shell opening and closing, and plump meat were selected and transported back to the Crassostrea hongkongensis germplasm farm in Beihai, Guangxi. The broodstock were knocked into individual individuals, and the attachments on the shell surface were removed and washed clean with sand-filtered seawater. The gonad tissue section detection showed that the gonad development reached stage II.

[0051] The 100 catties of cleaned broodstock were arranged side by side with the front end and the back end of the adjacent shells and loaded into a self-made floating frame, and each floating frame containing broodstock was suspended on the water surface to facilitate the feeding and defecation of the broodstock. The cultivation density was 60 per m 2 . The salinity of the sea area was measured to be 23‰, and seawater with the same salinity was prepared for ripening cultivation under normal temperature conditions (water temperature 18°C).

[0052] The light was regulated to 400 lux through a sunshade net. Sufficient cultivation biological bait was fed every day, the vitality of the broodstock was checked, the dead individuals were picked out, the whole pool was cleaned once every 3 days, and the gonad development degree was monitored by regular sampling. After 20 days of ripening cultivation by the conventional method, the shell was opened for appearance inspection and tissue section, and it was found that the gonad of the broodstock was not plump (such as Figure 2 ), the gonad development maturity was in stage III (such as Figure 5 ), the synchronous maturity rate was 32.7%, and the broodstock could not be used for seedling cultivation yet.

[0053] Comparative Example 2

[0054] Compared with Comparative Example 1, the difference is that in this comparative example, the seedling cultivation of the broodstock naturally ripened in the sea area was used.

[0055] On May 14, 2022, when a small part of the broodstock in the sea area was just mature, 200 catties of relatively mature broodstock were selected for seedling production in the Crassostrea hongkongensis germplasm farm in Beihai, Guangxi. The fertilization rate of gametes was 68.5%, the hatching rate was 64.3%, and a total of 250 million D-shaped larvae were hatched. After 15 days of cultivation, it reached the metamorphosis stage of eyed larvae, and the larvae began to attach. The survival rate of the larvae during the planktonic larval stage was 36.7%, and a total of 53,000 strings of seedlings were attached. The seedlings were out of the pond on June 7.

[0056] In summary, through the cultivation of indoor salt control, temperature control and circulating water, the present invention solves the problems of late gonad development, unstable supply, and uneven gamete maturity of the artificial seedlings of Crassostrea hongkongensis in large-scale breeding; through this method, the gonad of Crassostrea hongkongensis can mature in advance, the artificial seedling cultivation time of Crassostrea hongkongensis can be advanced, which not only lengthens the seedling cultivation season of Crassostrea hongkongensis, but also improves the success rate of artificial seedling cultivation, supplies high-quality seedlings for the industry, and moreover, the growth rate of the intermediate cultivation after the early seedlings are out of the pond is fast, and they can grow into large-scale seedlings in the same year, effectively shortening the breeding cycle and reducing the breeding risk, thus ensuring the healthy, efficient and sustainable development of the Crassostrea hongkongensis aquaculture industry.

[0057] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for promoting gonadal maturation of Crassostrea hongkongensis based on circulating water, characterized in that, It includes the following steps: Put the parent shellfish to be promoted to maturity into the cultivation pond, and the cultivation density of the parent shellfish to be promoted to maturity in the cultivation pond is 50-60 per m 2 ; Introduce the flowing tail water of the shrimp pond with adjusted salinity into the cultivation pond. The salinity of the tail water of the shrimp pond after salinity adjustment is 13-15‰, and the temperature of the tail water of the shrimp pond after salinity adjustment in the cultivation pond is 24-26°C; Cultivate the broodstock to be promoted for ripening until the gonad development maturity reaches stage V; The time for cultivating the broodstock to be promoted for ripening until the gonad development maturity reaches stage V is 10 - 30 days; Each of the broodstock to be promoted for ripening is Crassostrea hongkongensis with pure germplasm, shell height greater than or equal to 10 cm, wet weight above 150 g, regular shell shape, strong shell opening and closing, and plump meat; the gonad of each of the broodstock to be promoted for ripening has developed to above stage II; The flow rate of the adjusted salinity shrimp pond tail water flowing in the cultivation pond is 4 - 6 cm / s.

2. The method for promoting gonadal maturation of Crassostrea hongkongensis based on circulating water according to claim 1, wherein The salinity of the adjusted salinity shrimp pond tail water is 15‰, and the temperature of the adjusted salinity shrimp pond tail water in the cultivation pond is 25°C.

3. The method for promoting gonadal maturation of Crassostrea hongkongensis based on circulating water according to claim 1, wherein Put the broodstock to be promoted for ripening into the cultivation pond through a foam floating frame, so that each foam floating frame containing the broodstock to be promoted for ripening floats on the adjusted salinity shrimp pond tail water in the cultivation pond.

4. The method for promoting gonadal maturation of Crassostrea hongkongensis based on circulating water according to any one of claims 1 to 3, characterized in that, The depth of the adjusted salinity shrimp pond tail water in the cultivation pond is 60 - 80 cm, and the dissolved oxygen in the adjusted salinity shrimp pond tail water in the cultivation pond is ≥5 mg / L.

5. A method for promoting gonadal maturation of Crassostrea hongkongensis based on circulating water according to any one of claims 1 to 3, characterized in that, The cultivation pond includes a water inlet and a water outlet. At the water inlet, the shrimp pond tail water is mixed with fresh water to obtain the adjusted salinity shrimp pond tail water.

6. The method for promoting gonadal maturation of Crassostrea hongkongensis based on circulating water according to claim 5, wherein The water inlet and the water outlet are located on the diagonal line of the cultivation pond.

7. A method for promoting gonadal maturation of Crassostrea hongkongensis based on circulating water according to any one of claims 1 to 3, characterized in that It also includes daily management, and the daily management specifically includes the following steps: control the light in the cultivation pond at 200 - 500 lux through a sunshade net, check the vitality of the broodstock to be promoted for ripening at least once a day, pick out the dead broodstock to be promoted for ripening, and clean the cultivation pond at least once every 3 days.

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