Breeding and culturing method of razor clam (sinonovacula constricta) fry

Abstract

The present application belongs to the technical field of breeding and culturing of shellfish, and relates to a kind of breeding and culturing method of hard clam seedlings, which comprises the following steps: taking local wild hard clams in Tangshan coastal area as seed clams, transporting the seed clams to coastal mudflat ponds or outdoor ponds in Zhejiang or Shandong coastal area for bottom sowing and temporary breeding in early April every year, then placing the seed clams in a breeding workshop in Zhejiang or Shandong coastal area for fattening and maturation in mid-late May, inducing spawning and breeding seedlings after the gonad of the seed clams is matured, then preserving the seedlings in coastal mudflat ponds or open sea area in Zhejiang or Shandong coastal area to obtain large-size hard clam seedlings, and transporting the large-size hard clam seedlings to Tangshan coastal area for bottom sowing and culturing after the preservation of the seedlings is completed. The present application adopts the "relay type" large-size hard clam seedling culturing technology of bottom sowing and temporary breeding, indoor fattening and maturation, indoor seedling breeding and preservation in coastal mudflat ponds or open sea area, which significantly improves the success rate of seedling breeding, seedling preservation and culturing of hard clams.

Description

Technical Field

[0001] This invention belongs to the field of shellfish aquaculture technology, specifically relating to a method for breeding and cultivating blood clam seedlings. Background Technology

[0002] my country is rich in shellfish resources, and shellfish farming of various species and in various forms has become one of the largest aquaculture industries in my country, occupying an important position in my country's fishery production; among them, blood clams, as a common shellfish, have become a major farmed species.

[0003] Currently, most blood clam farming and breeding methods utilize wild blood clam populations to breed under local natural conditions. However, because blood clams are farmed and bred in a single area for a long time, their resistance or adaptability decreases, affecting the reproduction rate of blood clam seedlings. On the other hand, the breeding environment under natural conditions may result in low reproduction rates and slow growth of blood clam seedlings due to factors such as water temperature, salinity, and predation by natural enemies. For example, the coastal mudflats of Tangshan are mostly muddy sea areas. During the blood clam seedling breeding period, the seawater at the inlet is turbid and difficult to settle. The seawater has high salinity and temperature, and there are many wild algae and protozoa in the sediment of the pond, resulting in a very low success rate of blood clam shellfish breeding. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a method for breeding and cultivating blood clam seedlings.

[0005] The specific technical solution is as follows:

[0006] A method for breeding and cultivating blood clam seedlings includes: using wild blood clams native to the coastal areas of Tangshan as seed clams, transporting the seed clams to nearshore tidal flat ponds or outdoor ponds in the coastal areas of Zhejiang or Shandong in early April each year for bottom seeding and temporary rearing, and then placing them in breeding workshops in the coastal areas of Zhejiang or Shandong in mid-to-late May for fattening and maturation. After the gonads of the blood clam seed clams have matured, induction of spawning and seedling breeding are carried out to obtain blood clam seedlings. Subsequently, the blood clam seedlings are protected in nearshore tidal flat ponds or open sea areas in the coastal areas of Zhejiang or Shandong to obtain large-sized blood clam seedlings. After the seedling protection is completed, the large-sized blood clam seedlings are transported to the coastal areas of Tangshan for bottom seeding and cultivation; the size of the large-sized blood clam seedlings is 600-800 seeds / jin.

[0007] Preferably, the blood clam is the Tangshan black-edged blood clam, and the larvae are 2-3 year old blood clams with intact shells and good health.

[0008] Preferably, the blood clam larvae are collected from the nearshore waters of Tangshan by manual digging; manual digging can reduce physical damage to the blood clams.

[0009] Preferably, the breeding workshop is an indoor breeding workshop.

[0010] Specifically, before the fattening and maturation process, the broodstock are temporarily raised in nearshore tidal flats or outdoor ponds along the coast of Zhejiang or Shandong in early April. Once the seawater temperature in these ponds (the natural temperature of the seawater, without external temperature control) rises to 27°C, i.e., in mid-to-late May, they are then transferred to breeding workshops along the coast of Zhejiang or Shandong for fattening and maturation. This process ensures a high survival rate for the blood clams during transportation, temporary rearing, maturation, spawning, and sperm release.

[0011] Furthermore, bottom seeding and temporary rearing were carried out in nearshore mudflats and ponds in the coastal areas of Zhejiang or in outdoor ponds in the coastal areas of Shandong.

[0012] Preferably, during the fattening and maturation process, the density of broodstock is 100–150 bream / m². 2 The gonadal development and maturation of blood clam larvae can be promoted by increasing the amount of single-celled algae feed, feeding marine red yeast and / or feeding cooked egg yolk.

[0013] Furthermore, during the induced spawning process, spawning and sperm release in broodstock can be induced by air-drying and / or raising the water temperature; spawning and sperm release can also be induced by feeding cooked egg yolk and / or spirulina solution. The air-drying time, water temperature, and the amount of cooked egg yolk and spirulina solution fed can be adjusted appropriately according to the spawning and sperm release status of the broodstock; the air-drying time is preferably 5-6 hours; and the water temperature is preferably increased by 2-3°C.

[0014] Furthermore, during the seedling breeding process, when 40% of the larvae have developed eye spots and extended legs, an attachment substrate is introduced to allow the larvae to attach and metamorphose into juvenile shellfish; the attachment substrate is preferably polyethylene netting and / or marine mud, and the polyethylene netting and marine mud are disinfected before use.

[0015] Preferably, seedlings are kept in nearshore tidal flats and ponds along the coast of Zhejiang or in open sea areas along the coast of Shandong. During the pond seedling period, harmful organisms are regularly controlled; during the sea area seedling period, seedlings are regularly transplanted.

[0016] Furthermore, for seedling breeding in the coastal areas of Zhejiang, once the number of blood clam seedlings reaches 300,000 to 500,000 per kilogram, the seedlings are transported to near-shore tidal flats and ponds in the coastal areas of Zhejiang for seedling preservation until the number of seedlings reaches 600 to 800 per kilogram, thus obtaining large-sized blood clam seedlings. For seedling breeding in the coastal areas of Shandong, once the number of blood clam seedlings reaches 3 million to 4 million per kilogram, the seedlings are packed into net bags and transported to open sea areas in the coastal areas of Shandong for hanging rope culture, where the number of seedlings is preserved until the number of seedlings reaches 600 to 800 per kilogram, thus obtaining large-sized blood clam seedlings. In coastal Zhejiang, where seedlings are bred, the low salinity and high temperature of the seawater allow for a cultivation period of approximately 35 days, resulting in 300,000 to 500,000 seedlings per kilogram. During the seedling protection period, the nearshore tidal flats and ponds in Zhejiang have suitable water temperatures (22-24°C) and abundant algae feed, allowing for the production of large-sized seedlings in about 3-4 months. In coastal Shandong, where seedlings are bred, the slightly higher seawater temperature and the proliferation of red tide algae in July allow for a cultivation period of approximately 20 days, resulting in 3 million to 4 million seedlings per kilogram with a shell length of about 1.0 mm. During the seedling protection period, large-sized seedlings can be obtained in about 5-6 months.

[0017] Preferably, during the hanging rope culture process, the blood clam seedlings are separated every 20 to 25 days.

[0018] Preferably, during the transportation to the coastal area of ​​Tangshan, the blood clam seedlings are packed into nylon bags or insulated boxes and transported to the coastal area of ​​Tangshan using refrigerated trucks or iced vans; the temperature of the refrigerated trucks or iced vans is maintained below 10°C and the transportation time is maintained within 30 hours, at which time the blood clam seedlings have good vitality.

[0019] Furthermore, bottom seeding aquaculture is carried out in nearshore shallow tidal flats or nearshore ponds in the coastal areas of Tangshan, where natural populations of blood clam are distributed. Preferably, seeding is carried out in the early morning or evening when the wind and waves are calm to prevent damage to the blood clam seedlings or them from being washed away by the current, thereby improving the burrowing rate and survival rate of the blood clam seedlings. Preferably, harmful organisms are removed regularly before and after seeding.

[0020] Preferably, when conducting bottom seeding aquaculture in the nearshore shallow tidal flats of the Tangshan coastal area, the seeding density is 200-250 catties / mu. After approximately 12-15 months of cultivation, the large-sized blood clam seedlings can grow to marketable size.

[0021] Preferably, when conducting bottom-seeding aquaculture in nearshore ponds along the Tangshan coast, a shellfish-fish polyculture or shellfish-shrimp / crab polyculture model is adopted, with a seeding density of 250-300 catties / mu. In the aforementioned shellfish-fish and shellfish-shrimp / crab polyculture models, a ring ditch is dug in the aquaculture pond for raising fish or shrimp / crabs, while the central part of the pond is isolated with a net for raising blood clams; this model can increase the unit yield and output value of the pond. After approximately 10-12 months of pond culture, large-sized blood clam seedlings can grow to marketable size.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) The coastal mudflats of Tangshan are mostly muddy sea areas. During the seedling stage of blood clam, the seawater at the inlet is turbid and difficult to settle. The seawater has high salinity and temperature, and the sediment in the pond contains a lot of wild algae and protozoa, resulting in a very low success rate of shellfish seedling cultivation. This invention uses wild blood clams from the local coastal areas of Tangshan as seed clams. Before the breeding season, 2-3 year old blood clams with intact shells and good health are selected. Before the temporary holding seawater temperature is low and the blood clams' resistance or adaptability decreases, they are transported to the coastal areas of Zhejiang or Shandong in my country for temporary holding. The process involves breeding and preserving blood clam seedlings, which are then transported back to the coastal areas of Tangshan for bottom seeding aquaculture. Since the sea areas along the coast of Zhejiang and Shandong in my country are mostly composed of muddy and sandy bottoms, the seawater is clear and easy to settle, with few wild algae and protozoa, and the salinity is low (22-25). The seedling temperature does not exceed 32℃. This approach can significantly improve the success rate of blood clam seedling cultivation and significantly reduce the costs of seedling cultivation, preservation, and labor, providing a large number of high-quality blood clam seedlings to the coastal areas of Tangshan in a short period of time.

[0024] (2) This invention employs a "relay" technology for cultivating large-sized blood clam seedlings, involving bottom seeding and temporary rearing, indoor fattening and ripening, indoor seedling propagation, and nearshore tidal flat pond / open sea area seedling protection. This significantly improves the success rate of blood clam seedling cultivation and protection, shortening the seedling cultivation time by 2-3 months. Large-sized blood clam seedlings are transported back to the coastal areas of Tangshan for bottom seeding cultivation. These large-sized seedlings exhibit strong adaptability, rapid growth, and a significantly increased overwintering survival rate. They reach marketable size in approximately 10-15 months. Overall, this invention shortens the blood clam cultivation time by 4-6 months, enabling earlier market access for blood clam products. Detailed Implementation

[0025] The principles and features of the present invention are described below with reference to examples. These examples are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. The first ten days of the month are from the 1st to the 10th; the middle ten days are from the 11th to the 20th; and the last ten days are from the 21st to the last day of the month.

[0026] Example 1

[0027] On April 1, 2023, 200 catties of wild black-edged blood clams were collected manually from the nearshore waters of Heiyanzi Town, Tangshan City. The clams were transported by van to a cooperative shellfish breeding farm in Laizhou, Shandong Province. Two- to three-year-old clams with intact shells and good health were selected as broodstock. After disinfection and cleaning, they were temporarily sown in outdoor ponds on the same day. On May 15, before the seawater temperature in the outdoor ponds rose to 27℃, large clams with well-developed gonads were selected and transferred to an indoor breeding workshop for fattening and maturation. The broodstock density was 100-150 clams / m². 2 The breeding shellfish are primarily fed with golden algae, chaete algae, crescent-shaped algae, and triangular brown finger algae, supplemented with flat algae, spirulina, and marine red yeast powder. The feeding rate is 500,000 to 800,000 cells / ml, divided into 8 feedings per day. The feeding amount is adjusted appropriately based on the feeding and development of the shellfish. The water is changed twice daily, morning and evening, with 50% to 70% of the water replaced each time. If there is a high concentration of feed and feces in the rearing tank, the water is changed by emptying the tank completely. During this period, the development of the breeding shellfish's gonads is continuously observed and recorded, and samples are taken to measure indicators such as the gonad index and condition factor.

[0028] Dissection and microscopic examination revealed that the gonads of the blood clam were mature. Subsequently, induced spawning and seedling propagation were carried out in an indoor breeding workshop. Spawning and sperm release were induced in the blood clam spawning clams by air-drying for 6 hours combined with raising the water temperature by 2°C. Simultaneously, 2 ppm of spirulina solution and two cooked egg yolks were added to the tank. Spawning and sperm release began within one hour of the clams being placed in the water. Furthermore, disturbance was minimized during the spawning process to prevent human interference from interrupting spawning and sperm release. Male blood clams were promptly removed during spawning, and sperm density was controlled by washing the eggs. The density of fertilized eggs was adjusted to 35–40 eggs / mL by separating them into different tanks. During incubation, a small amount of aeration was provided, and the water in the incubation tank was stirred once per hour to prevent the fertilized eggs from sinking and clumping together. After approximately 24 hours of incubation, the fertilized eggs of the blood clam develop into D-shaped larvae. The upper and middle-layer larvae are selected using a siphon method, and the D-shaped larvae are then screened using 300-mesh silk and transferred to a new rearing tank at a density of 8–9 larvae / mL. The initial food for the D-shaped larvae is *Isochrysis galbana*, supplemented with *Chaetoceros muelleri*, with the feeding rate gradually increasing from 10,000 cells / mL to 50,000 cells / mL daily, divided into six feedings per day. Water is changed twice daily, morning and evening, with each water change representing 30%–50% of the volume. After about 7 days of rearing, when the D-shaped larvae reach the apex stage, they are transferred to a new tank at a density of 4–5 larvae / mL, with water changed twice daily, morning and evening, with each water change representing 50%–70% of the volume. The apex larvae are then fed primarily with *Isochrysis galbana* and *Chaetoceros muelleri*, supplemented with *Chlorella vulgaris* and *Platycodon grandiflorus*, with the feeding rate gradually increasing from 50,000 cells / mL to 100,000 cells / mL daily, divided into six feedings per day. After 12–14 days of cultivation, the shell length of the larvae grew to 240–260 μm. Microscopic examination revealed that 40% of the larvae developed eyespots and collapsed into the tank when extending their legs. The tanks were then rearranged at a density of 1.5–2.0 larvae / mL, and sterilized polyethylene netting was added as an attachment substrate. In the initial stage of introducing the attachment substrate, change the water twice a day, morning and evening, with each change involving 70% to 100% of the water volume. The main feed consists of golden algae and chamomile, supplemented with chlorella and flat algae. The feeding amount is gradually increased from 100,000 cells / mL per day to 150,000 cells / mL, and fed 6 times a day. After the larvae have just attached and metamorphosed, change the water twice a day, morning and evening, with each change involving 80% to 100% of the water volume. After 10 days of attachment, change the water 4 times a day, with a daily water volume of 100% to 150%. The main feed consists of golden algae and diatoms, supplemented with chlorella and flat algae. The feeding amount is gradually increased from 150,000 cells / mL per day to 300,000 cells / mL. Feed once every 4 hours before the water is changed and after the water is changed during the water change period. After about 20 days of cultivation, the number of blood clam seedlings reaches 3 to 4 million per kilogram (shell length about 1.0 mm). The blood clam seedlings are brushed off the attachment base, the bottom of the pool, and the pool wall, counted, and then transported to the sea area for seedling preservation.

[0029] On July 10, the blood clam seedlings were packed into net bags and transported to the open sea area of ​​Changdao Island for rope-climbing culture to ensure seedling survival. During the seedling survival period, the seedlings were divided regularly, once every 20 to 25 days. Each time the seedlings were divided, the blood clam seedlings were transferred to net bags with larger mesh for continued cultivation. In December, the blood clam seedlings grew to 600 to 800 grains / catties, and large-sized blood clam seedlings were obtained.

[0030] Large-sized blood clam seedlings were packed into nylon bags or insulated boxes and transported to the coastal area of ​​Tangshan within 30 hours using refrigerated trucks (maintaining a temperature below 10℃). They were then bottom-seeded in near-shore ponds in the Tangshan coastal area. The seedlings were evenly sown in the early morning or late evening when the wind and waves were calm, and predators were removed regularly before and after sowing. A shellfish-fish polyculture model was adopted (shrimp and crabs were raised in ring ditches in the pond, while blood clams were raised in the middle of the pond using a net enclosure). The sowing density was 250-300 catties / mu. The seedlings were observed underwater 3 hours and 24 hours after sowing to monitor their sand burrowing. During the cultivation period, the water was regularly changed, fertilized, and predators were removed. By November 2024, the adult blood clams had grown to 50-60 clams / jin.

[0031] In this embodiment, blood clam larvae were transported to a cooperative hatchery in the coastal area of ​​Shandong Province for temporary rearing before mid-April. The seawater temperature was similar to that of the blood clam collection area, and the blood clam larvae were less damaged by dew stress during transportation. The survival rate of blood clam larvae during temporary rearing was high, and the quality of eggs and fertilization and hatching rate were both very high after sexual maturity. Ultimately, this was reflected in the high rate of attachment and metamorphosis of blood clam larvae, and the high seedling emergence rate and seedling survival rate. The mortality rate of blood clam larvae after induced spawning was less than 10%.

[0032] Comparative Example 1

[0033] On June 9, 2023, 200 jin (approximately 100 catties) of wild black-edged blood clams were collected manually from the nearshore waters of Heiyanzi Town, Tangshan City. The clams were transported by van to a cooperative shellfish breeding farm in Laizhou, Shandong Province. Two- to three-year-old clams with intact shells and good health were selected as breeding stock. After disinfection and cleaning, they were directly placed into the indoor breeding workshop for fattening and maturation on the same day, with a breeding stock density of 100-150 clams / m². 2 The breeding shellfish are primarily fed with golden algae, chaete algae, crescent-shaped algae, and triangular brown finger algae, supplemented with flat algae, spirulina, and marine red yeast powder. The feeding rate is 500,000 to 800,000 cells / ml, divided into 8 feedings per day. The feeding amount is adjusted appropriately based on the feeding and development of the shellfish. The water is changed twice daily, morning and evening, with 50% to 70% of the water replaced each time. If there is a high concentration of feed and feces in the rearing tank, the water is changed by emptying the tank completely. During this period, the development of the breeding shellfish's gonads is continuously observed and recorded, and samples are taken to measure indicators such as the gonad index and condition factor.

[0034] On June 22, dissection and microscopic examination revealed that the gonads of the blood clam spawning oysters were mature. Subsequently, induced spawning and seedling propagation were carried out in the indoor breeding workshop. Spawning and sperm release were induced in the blood clam spawning oysters by air-drying for 6 hours combined with raising the water temperature by 2°C. Simultaneously, 2 ppm of spirulina solution and two cooked egg yolks were added to the tank. Spawning and sperm release began within one hour of the oysters entering the water. Furthermore, disturbance was minimized during the spawning process to prevent human interference from interrupting spawning and sperm release. Male blood clams were promptly removed during spawning, and sperm density was controlled by washing the eggs. The density of fertilized eggs was adjusted to 35–40 eggs / mL by separating them into different tanks. During the incubation period, a small amount of aeration was provided, and the water in the incubation tank was stirred once per hour to prevent the fertilized eggs from sinking and clumping together. After approximately 24 hours of incubation, the fertilized eggs of the blood clam develop into D-shaped larvae. The upper and middle-layer larvae are selected using a siphon method, and the D-shaped larvae are then screened using 300-mesh silk and transferred to a new rearing tank at a density of 8–9 larvae / mL. The initial food for the D-shaped larvae is *Isochrysis galbana*, supplemented with *Chaetoceros muelleri*, with the feeding rate gradually increasing from 10,000 cells / mL to 50,000 cells / mL daily, divided into six feedings per day. Water is changed twice daily, morning and evening, with each water change representing 30%–50% of the volume. After about 7 days of rearing, when the D-shaped larvae reach the apex stage, they are transferred to a new tank at a density of 4–5 larvae / mL, with water changed twice daily, morning and evening, with each water change representing 50%–70% of the volume. The apex larvae are then fed primarily with *Isochrysis galbana* and *Chaetoceros muelleri*, supplemented with *Chlorella vulgaris* and *Platycodon grandiflorus*, with the feeding rate gradually increasing from 50,000 cells / mL to 100,000 cells / mL daily, divided into six feedings per day. After 12–14 days of cultivation, the shell length of the larvae grew to 240–260 μm. Microscopic examination revealed that 40% of the larvae developed eyespots and collapsed into the tank when extending their legs. The tanks were then rearranged at a density of 1.5–2.0 larvae / mL, and sterilized polyethylene netting was added as an attachment substrate. In the initial stage of introducing the attachment substrate, change the water twice a day, morning and evening, with each change involving 70% to 100% of the water volume. The main feed consists of golden algae and chamomile, supplemented with chlorella and flat algae. The feeding amount is gradually increased from 100,000 cells / mL per day to 150,000 cells / mL, and fed 6 times a day. After the larvae have just attached and metamorphosed, change the water twice a day, morning and evening, with each change involving 80% to 100% of the water volume. After 10 days of attachment, change the water 4 times a day, with a daily water volume of 100% to 150%. The main feed consists of golden algae and diatoms, supplemented with chlorella and flat algae. The feeding amount is gradually increased from 150,000 cells / mL per day to 300,000 cells / mL. Feed once every 4 hours before the water is changed and after the water is changed during the water change period. After about 20 days of cultivation, the number of blood clam seedlings reaches 3 to 4 million per kilogram (shell length about 1.0 mm). The blood clam seedlings are brushed off the attachment base, the bottom of the pool, and the pool wall, counted, and then transported to the sea area for seedling preservation.

[0035] On August 5th, the blood clam seedlings were packed into net bags and transported to the open sea area of ​​Changdao Island for rope-climbing culture to ensure seedling survival. During the seedling survival period, the seedlings were divided regularly, once every 20-25 days. Each time the seedlings were divided, the blood clam seedlings were transferred to net bags with larger mesh for continued cultivation. On November 21st, the blood clam seedlings grew to about 3000 seeds / catties. In April of the following year, the blood clam seedlings grew to 600-800 seeds / catties, and large-sized blood clam seedlings were obtained.

[0036] Large-sized blood clam seedlings were packed into nylon bags or insulated boxes and transported to the coastal area of ​​Tangshan within 30 hours using refrigerated trucks (maintaining a temperature below 10℃). They were then bottom-seeded in near-shore ponds in the Tangshan coastal area. The seedlings were evenly sown in the early morning or late evening when the wind and waves were calm, and predators were removed regularly before and after sowing. A shellfish-fish polyculture model was adopted (shrimp and crabs were raised in ring ditches in the pond, while blood clams were raised in the middle of the pond using a net enclosure). The sowing density was 250-300 catties / mu. The seedlings were observed underwater 3 hours and 24 hours after sowing to monitor their sand burrowing. During the cultivation period, the water was regularly changed, fertilized, and predators were removed. On November 7, 2024, the survival rate of blood clams in the ponds was over 70%, and the adult blood clams grew to 50-60 clams / jin.

[0037] Table 1 shows the growth indicators of large-sized seedlings and finished blood clams in this comparative example. According to Table 1, the finished blood clams in this comparative example had a wet weight of approximately 9.86g, a shell length of approximately 27.12mm, a shell width of approximately 21.35mm, and a shell height of approximately 16.27mm. However, because the blood clam spawn was collected in June, a relatively late time, and without any temporary rearing, the mortality rate of the spawn during the fattening and maturation process in the workshop was very high, with over 80% of the spawn dying before spawning.

[0038] Table 1. Growth indicators of large-sized blood cockle seedlings and finished blood cockles in Comparative Example 1.

[0039] Large-sized blood clam seedlings 0.63±0.21 12.97±1.02 7.54±1.65 9.97±1.13 Finished blood cockles 9.86±2.35 27.12±2.83 21.35±1.75 16.27±0.98

[0040] Comparative Example 2

[0041] On June 16, 2023, 200 jin (approximately 100 catties) of wild black-edged blood clams were collected manually from the nearshore waters of Heiyanzi Town, Tangshan City. The clams were transported by van to the Qingjiang Cooperative Shellfish Breeding Farm in Zhejiang Province. Two- to three-year-old clams with intact shells and good health were selected as breeding stock. After disinfection and cleaning, the clams were placed in the indoor breeding workshop on the same day for fattening and maturation, with a stocking density of 100-150 clams / m². 2Due to the prolonged exposure during transportation, the blood clam larvae quickly spawn and release sperm after entering the water. Male blood clams were promptly selected during this period. After washing the eggs, the fertilized eggs were incubated in the spawning pond at a density of 25-30 eggs / mL. The fertilized eggs developed into D-shaped larvae approximately 24 hours after hatching. The upper and middle layers of D-shaped larvae were selected using a siphon method. Finally, the blood clam larvae were cultured according to the blood clam larvae cultivation technique described in Example 1. During the larval cultivation period, the seawater salinity was maintained at 22-24. The larvae could develop normally and at a faster rate when the water temperature exceeded 30℃. After 17 days of cultivation, the blood clam larvae developed eye spots and differentiated legs.

[0042] On August 6, 2023, when 40% of the larvae showed eyespots and extended legs, the eyespot larvae were transferred to a cultivation pond pre-filled with marine mud as an attachment substrate for metamorphosis. The marine mud was collected from nearby coastal mudflats and was used after being dried, disinfected, crushed, sieved, and boiled for disinfection. After the blood clam larvae attached, the pond water was directly changed. The pond water contained bottom mud, benthic diatoms, and trace elements. The pond water used for water change was fertilized, regulated, and treated before use. After about 35 days of cultivation, the blood clam seedlings grew to 300,000 to 500,000 per kilogram and were then packed into nylon bags and transferred to near-shore mudflat ponds in the Qingjiang River for seedling protection.

[0043] On September 10, 2023, blood clam seedlings (300,000-500,000 seedlings / catties) were transferred to near-shore tidal flat ponds for seedling protection, with a seeding density of 20-25 catties / mu. The bottom sediment of the near-shore tidal flat ponds in Qingjiang, Zhejiang Province, is suitable for blood clam seedling protection and cultivation. The area is rich in food organisms, and the water temperature and salinity (22-24) are suitable, allowing blood clam seedlings to grow rapidly. The initial 300,000-500,000 seedlings / catties can reach 600-800 seedlings / catties in 3-4 months. During the seedling protection period, predatory organisms were regularly controlled. On December 7, 5,000 kg of large-sized Tangshan blood clam seedlings (600-800 seedlings / catties) were successfully cultivated. These large-sized seedlings were transported to a cooperative company in the coastal area of ​​Tangshan for bottom-seeding cultivation. The refrigerated truck transport time was 20 hours, and the large-sized seedlings showed good vitality. Nearshore shallow tidal flats with natural distribution of wild blood clam populations, muddy seabeds, and moderate currents were selected for blood clam bottom seeding culture. Blood clam seedlings were evenly sown at a density of 200-250 catties / mu (approximately 133-120 kg / acre), with a seedling size of 600-800 clams / jin (approximately 300-400 clams / catties). The bottom seeding area was located using floats and GPS. Diving was conducted 3 hours and 24 hours after sowing to observe the sand burrowing of the blood clam seedlings and to preliminarily determine the survival rate. Predatory organisms were regularly removed during the culture period. On December 15, 2024, the survival rate of blood clam culture in the area exceeded 60%, and the blood clams grew to 40-60 clams / jin (approximately 20-30 clams / catties).

[0044] Table 2 shows the growth indicators of large-sized seedlings and finished blood clams in this comparative example. According to Table 2, the wet weight of the finished blood clams in this comparative example is approximately 11.26g, the shell length is approximately 36.72mm, the shell width is approximately 28.52mm, and the shell height is approximately 23.23mm. However, because the blood clam spawn was collected in June, a relatively late time, and without any temporary rearing, the mortality rate of the spawn during the fattening and maturation process in the workshop was very high, with nearly 80% of the spawn dying before spawning.

[0045] Table 2. Growth indicators of large-sized blood cockle seedlings and finished blood cockles in Comparative Example 2.

[0046]

[0047]

[0048] Comparative Example 3

[0049] Referring to Example 1, the difference is that blood clam larvae were collected in mid-to-late April for bottom seeding and temporary rearing.

[0050] During the aquaculture process, it was found that the mortality rate of blood clam larvae was nearly 30% during temporary pond rearing, and the mortality rate reached over 70% after spawning.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for breeding and cultivating blood clam seedlings, characterized in that, The method includes: using wild blood clams native to the coastal areas of Tangshan as broodstock, transporting the broodstock to nearshore tidal flats or outdoor ponds in Zhejiang or Shandong coastal areas in early April each year for bottom seeding and temporary rearing; then placing them in breeding workshops in Zhejiang or Shandong coastal areas in mid-to-late May for fattening and maturation; after the gonads of the broodstock mature, inducing spawning and seedling propagation to obtain blood clam seedlings; subsequently, protecting the blood clam seedlings in nearshore tidal flats or open sea areas in Zhejiang or Shandong coastal areas to obtain large-sized blood clam seedlings; after the seedling protection is completed, transporting the large-sized blood clam seedlings to the coastal areas of Tangshan for bottom seeding culture; the size of the large-sized blood clam seedlings is 600-800 seeds / jin (approximately 0.5 catties). The blood clam is the Tangshan black-edged blood clam, and the larvae are 2-3 year old blood clams; Blood clam seedlings are raised in nearshore tidal flats and ponds along the Zhejiang coast or in open sea areas along the Shandong coast for seedling protection. For seedlings bred in the Zhejiang coast, once the number of blood clam seedlings reaches 300,000 to 500,000 per kilogram, the seedlings are transported to nearshore tidal flats and ponds along the Zhejiang coast for seedling protection. For seedlings bred in the Shandong coast, once the number of blood clam seedlings reaches 3 million to 4 million per kilogram, the seedlings are transported to open sea areas along the Shandong coast for seedling protection. The seedling protection method is rope-suspended aquaculture.

2. The method according to claim 1, characterized in that, The blood cockles in question are those with intact shells and in good health.

3. The method according to claim 1, characterized in that, In early April, the broodstock were temporarily cultured in nearshore mudflat ponds in the coastal areas of Zhejiang or in outdoor ponds in the coastal areas of Shandong.

4. The method according to claim 1, characterized in that, Bottom seeding aquaculture is carried out in nearshore shallow beaches or nearshore ponds in the coastal areas of Tangshan.

5. The method according to claim 4, characterized in that, The nearshore shallow mudflats of the Tangshan coastal area have natural populations of blood clams.

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