Scapharcd subcrenata (Lischke) belongs to the mollusk, semipalatology, order, family, and genus of the genus, mainly distributed on the coasts of China, North Korea, and Japan, with the Bohai Sea and the East China Sea more offshore. In the past, all the seedlings required for the breeding of magpies depended on natural collection and the sources of seedlings were not stable. In order to explore the technique of artificial breeding of miracidia, the author conducted a productive nursery experiment on a 500 cubic meter indoor nursery pond and achieved success. The test is now reported as follows:
First, materials and methods
1. Intimate sources and holdings are from the natural sea area in the northern part of the Yellow Sea. On July 4th, 150kg of mature pro-shellfish were harvested and the shell length was 5cm to 6cm. The shell surface was fresh, intact and intact, and the gonads were full, shiny, and free of wrinkles. After being washed into the pool, raise the stocking density to 50/m3, and change the water thoroughly once in the morning and evening during the holding period. The bait-feeding organisms are mainly Chlorella, with a small amount of cyanobacteria, daily feeding amount. 250,000 cells/mL to 300,000 cells/mL. The water temperature varies from 23°C to 30°C, and the salinity varies from 22 ‰ to 25 。.
2. Fertilization Using egg-dried water induced method to obtain eggs. After prolonged incubation for 12 days, followed by 6 hours of dryness and 3 hours of induced flow, large amounts of sperm and eggs were released at 7:30 pm on July 16 and the majority of innocuous emissions of sperms and eggs ended at 9:00 pm. More than 90%. When intimacy is discharged, the double shells open slightly, males emit white smoke-like semen, and females emit red eggs. In order to reduce the number of spermatozoa, it can be removed immediately when the spermatorrhea is found. After the spawning is completed, the female beetle is quickly removed, and the fertilized egg is diluted in time. After filling the water for 1 hour, the upper 1â„2 of the pool water is sucked, and the egg is repeatedly washed 2 times.
3. Incubation and selection of young hatching density of 30 grains / mL to 50 grains / mL, during the incubation period of micro-inflated, until the larvae have not yet floated, insisted on every half an hour to stir the water with a raft, once after 24 hours to 26 hours to reach D Shaped larvae. After entering the D-shaped larvae, they need to be bred immediately by dragging and concentrating.
4. The larva rearing D-shaped larvae cultivating density of 8 / mL to 10 / mL, bait organisms fork algae, Chlorella, and Pyramidala. During the D-shaped larval stage, the daily feeding amount was 10,000 cells/mL to 30,000 cells/mL, and the feeding was mainly forked algae; the top of the shell was attached to the metamorphosis, and the daily feeding amount was 30,000 cells/mL to 80,000. Cells/mL were mainly fed with Chlorella, with a small amount of cyanobacteria. The water changing work starts from the third day after the larvae are selected. Each morning and evening, the water changes 1 time, and the water changing amount is 1/3 of the total amount in the previous period, 1/2 in the middle period, and 2/3 in the later period. During the incubation period, the pool was poured 2 times, 7 days apart, and micro-inflated.
5. Dispensing attachments On August 5th, the larvae with a shell length of 270 to 300 μm were poured into a cultivating pool with a brown cord attachment base, so that the larvae were metamorphosed and the attachment density was about 2 per mL. The attached base of the brown rope is placed at an extension of 450m per cubic meter of water, and the size of the cord attachment base is 12m0.5m per curtain. The treatment and delivery methods of the cord attachments are similar to those of scallop seedlings. At this point, about 35% of larvae have eye spots.
6. Cultivation of juveniles On the 10th of August, the larval deposition metamorphosis was basically completed, and the amount of daily feeding after the attachment was increased to 100,000 cells/mL to 120,000 cells/mL. The water changing mode was changed to circulation water, and each water flow 4 Hours, 2 times a day, daily flow guaranteed 2 full or more. It is worth noting that: the incubating water for insemination and seedlings is sand filter water, intermittently adding 1 mg/L to 2 mg/L antibiotic, and EDTA disodium is always maintained at 2 mg/L to 3 mg/L.
7. Use shrimp ponds for mid-parent breeding. On August 25th, the pool of juveniles was suspended in cages for intermediate breeding. The shrimp pond area is 36 mu, length is 350m, width is 70m, water depth is 2m, and the pool slope is protected with plastic cloth. The size of the 60 mesh net bag is 47cm29cm. Each bag is loaded with 1 curtain attachment base, and a total of 37500 bags are installed. Rope tied 9 bags, divided into 3 layers, net bag spacing 20cm, pendant hanging rope at the bottom of the stone, the bottom of the net bag from the bottom of the pool 30cm, floating stem spacing of 3m, sling spacing 1m.
On September 11, the 60-mesh bag was replaced with a 26-mesh bag and counted again. The juveniles on the attachment base were all brushed off and reloaded with 2000 bags. A total of 75,000 bags were loaded. The slings are bundled in 12 bags and divided into 3 layers. 26 mesh bags add 50g ~ 100g net clothes. The bred pool was filled with water 15 days before the jujube bagging, and the amount of fertilizer applied was 1 mg/L of nitrogen and 0.1 mg/L of phosphorus. After entering the end of September, the water should be top-dressed as the color changes. After the juveniles went to the pool, they did not need to brush their bags for the first 7 days. After that, they insisted on brushing the bags once every 1 day to 2 days. Changing the water to use the water pump to use the high tide to pump water would make the exchange volume in the flood season about 150%.
In early November, the juvenile net bags bred in the middle of the shrimp ponds were brushed and hung into the room for winter. During the wintering period, the daily exchange volume of water exchange is 30%, the water temperature changes from 1°C to 5°C, and the salinity changes from 26°C to 28°F. The average mesh bag is washed and inverted once a month. In March of the following year, as water temperature rises, daily water exchange capacity should increase from 50% to 100%.
Second, the test results
1. The survival rate of relatives was 150kg on July 4th, and on the 16th of July was used for oxytocin 85kg. The survival rate of pro-breeding was 56%.
2. The fertilized eggs that have more than 90% of the fertilized eggs emit sperm and eggs. The fertilized eggs are about 6 billion eggs and the egg diameter of the fertilized eggs is 58 μm.
3. Hatching rate From 7 pm to 10 pm on July 17th, D-shaped larvae were developed after 24 to 26 hours. A total of 5 billion D-shaped larvae were obtained, and the hatching rate was 83%. The initial D-shaped larval shell length is 85 μm and the shell height is 68 μm.
4. Survival rate of D-shaped larvae to the top of the shell On August 5, the survival of the larvae at the end of the shell was 1.25 billion, the survival rate was 28%, the shell length of the larvae was 270 μm to 300 μm, and the shell height was 180 μm to 201 μm.
5. Emergence of juvenile juveniles in ponds On August 25th, juveniles were randomly sampled before bagging out of the pool and measured an average of 620,000 seedlings per cubic meter of water. A total of 310 million seedlings emerged, and the metamorphosis rate of parasitized larvae was 31%. The length of the juvenile shell is 1.2mm to 0.82mm, and the shell height is 0.8mm to 0.55mm.
6. After the wintering, the juveniles finally emerged in early April. In early April, a total of 1,650 kg of shellfish were sold, with an average size of 54,600 pieces/kg, totaling 90 million pieces. The juveniles were bred and survived in winter for 29%.
Third, discuss
1. Whether the intimacy is induced by inducing production, inducing production, or not, depends on whether the intimal gonads are mature or not. After the mature pro-scorpion enters the pool, the sperm and eggs can be smoothly excreted after being induced by the dripping water. The survival rate of the pro-sputum and the hatching rate of the fertilized eggs are all Guaranteed. Immature intimacy requires intensified ripening. Because of the proneness to problems in the process of ripening, such as high water temperatures, diseases, etc., the survival rate of inbreeding and the hatching rate of fertilized eggs are often not guaranteed. On July 4, the intimacy of entering the pool, the gonads are mature, but due to catching up with the high temperature, the water temperature reached 29 °C ~ 30 °C, the result of the intimacy of the gonads has undergone severe degradation and a large number of deaths, since the spawning pro? With 85 kg remaining, the survival rate is only 55.6%. Therefore, it is very important to take timely and mature pro-taste to avoid raising the water temperature. The author believes that the best time for intimacy should be collected from the end of June to the beginning of July, and the incubation temperature should not exceed 27.5°C. After the mature pro-aesculia is broken, the appearance of gonads should be full, cover the entire bulging surface, and be lusterless. No wrinkle, clear microscopic examination, round or oval, sperm swims lively.
2. Larval cultivation From the results of larval rearing, the 28% survival rate of the larvae during the planktonic stage and the 31% of the metamorphosis rate of the larvae were unsatisfactory. The main reason for the analysis was the dietary quality problem. The larvae were predominantly golden algae in the early stage of cultivation, and mainly chlorella in the middle period. A small amount of cyanobacteria was found in the larvae. It can be seen that the fed biological composition was irrational and the variety was single. Should increase feeding diatoms, chlorella does not feed or less feeding; In addition, water quality sand filter effect is not good, the water is not a clean cause is also a reason.
3. Intermediate breeding and overwintering juveniles using net bags to hang bred and overwintering can effectively prevent harm to predator organisms, increase survival rate, and be easy to catch. There is no missing trapping loss. The shortage is the density of juveniles in bags. If it is too large, the mesh is easy to be blocked, water exchange and juvenile feeding are affected, and operations such as brushing the net bag are easy to cause damage to the juveniles. These conditions greatly affect the survival rate and growth rate of the juveniles, especially at 60 mesh. In the cultivation of bags, the impact was particularly obvious. In only 15 days to 20 days, the survival rate was only 48.3%. Therefore, strengthen and improve the cultivation and management at this stage, such as changing bags and seedlings in a timely manner, controlling reasonable cultivation densities, strengthening the exchange of water quality, avoiding excessive water quality, and avoiding friction and squeezing by operations such as bagging, transportation, hanging, and brushing. It is important.
First, materials and methods
1. Intimate sources and holdings are from the natural sea area in the northern part of the Yellow Sea. On July 4th, 150kg of mature pro-shellfish were harvested and the shell length was 5cm to 6cm. The shell surface was fresh, intact and intact, and the gonads were full, shiny, and free of wrinkles. After being washed into the pool, raise the stocking density to 50/m3, and change the water thoroughly once in the morning and evening during the holding period. The bait-feeding organisms are mainly Chlorella, with a small amount of cyanobacteria, daily feeding amount. 250,000 cells/mL to 300,000 cells/mL. The water temperature varies from 23°C to 30°C, and the salinity varies from 22 ‰ to 25 。.
2. Fertilization Using egg-dried water induced method to obtain eggs. After prolonged incubation for 12 days, followed by 6 hours of dryness and 3 hours of induced flow, large amounts of sperm and eggs were released at 7:30 pm on July 16 and the majority of innocuous emissions of sperms and eggs ended at 9:00 pm. More than 90%. When intimacy is discharged, the double shells open slightly, males emit white smoke-like semen, and females emit red eggs. In order to reduce the number of spermatozoa, it can be removed immediately when the spermatorrhea is found. After the spawning is completed, the female beetle is quickly removed, and the fertilized egg is diluted in time. After filling the water for 1 hour, the upper 1â„2 of the pool water is sucked, and the egg is repeatedly washed 2 times.
3. Incubation and selection of young hatching density of 30 grains / mL to 50 grains / mL, during the incubation period of micro-inflated, until the larvae have not yet floated, insisted on every half an hour to stir the water with a raft, once after 24 hours to 26 hours to reach D Shaped larvae. After entering the D-shaped larvae, they need to be bred immediately by dragging and concentrating.
4. The larva rearing D-shaped larvae cultivating density of 8 / mL to 10 / mL, bait organisms fork algae, Chlorella, and Pyramidala. During the D-shaped larval stage, the daily feeding amount was 10,000 cells/mL to 30,000 cells/mL, and the feeding was mainly forked algae; the top of the shell was attached to the metamorphosis, and the daily feeding amount was 30,000 cells/mL to 80,000. Cells/mL were mainly fed with Chlorella, with a small amount of cyanobacteria. The water changing work starts from the third day after the larvae are selected. Each morning and evening, the water changes 1 time, and the water changing amount is 1/3 of the total amount in the previous period, 1/2 in the middle period, and 2/3 in the later period. During the incubation period, the pool was poured 2 times, 7 days apart, and micro-inflated.
5. Dispensing attachments On August 5th, the larvae with a shell length of 270 to 300 μm were poured into a cultivating pool with a brown cord attachment base, so that the larvae were metamorphosed and the attachment density was about 2 per mL. The attached base of the brown rope is placed at an extension of 450m per cubic meter of water, and the size of the cord attachment base is 12m0.5m per curtain. The treatment and delivery methods of the cord attachments are similar to those of scallop seedlings. At this point, about 35% of larvae have eye spots.
6. Cultivation of juveniles On the 10th of August, the larval deposition metamorphosis was basically completed, and the amount of daily feeding after the attachment was increased to 100,000 cells/mL to 120,000 cells/mL. The water changing mode was changed to circulation water, and each water flow 4 Hours, 2 times a day, daily flow guaranteed 2 full or more. It is worth noting that: the incubating water for insemination and seedlings is sand filter water, intermittently adding 1 mg/L to 2 mg/L antibiotic, and EDTA disodium is always maintained at 2 mg/L to 3 mg/L.
7. Use shrimp ponds for mid-parent breeding. On August 25th, the pool of juveniles was suspended in cages for intermediate breeding. The shrimp pond area is 36 mu, length is 350m, width is 70m, water depth is 2m, and the pool slope is protected with plastic cloth. The size of the 60 mesh net bag is 47cm29cm. Each bag is loaded with 1 curtain attachment base, and a total of 37500 bags are installed. Rope tied 9 bags, divided into 3 layers, net bag spacing 20cm, pendant hanging rope at the bottom of the stone, the bottom of the net bag from the bottom of the pool 30cm, floating stem spacing of 3m, sling spacing 1m.
On September 11, the 60-mesh bag was replaced with a 26-mesh bag and counted again. The juveniles on the attachment base were all brushed off and reloaded with 2000 bags. A total of 75,000 bags were loaded. The slings are bundled in 12 bags and divided into 3 layers. 26 mesh bags add 50g ~ 100g net clothes. The bred pool was filled with water 15 days before the jujube bagging, and the amount of fertilizer applied was 1 mg/L of nitrogen and 0.1 mg/L of phosphorus. After entering the end of September, the water should be top-dressed as the color changes. After the juveniles went to the pool, they did not need to brush their bags for the first 7 days. After that, they insisted on brushing the bags once every 1 day to 2 days. Changing the water to use the water pump to use the high tide to pump water would make the exchange volume in the flood season about 150%.
In early November, the juvenile net bags bred in the middle of the shrimp ponds were brushed and hung into the room for winter. During the wintering period, the daily exchange volume of water exchange is 30%, the water temperature changes from 1°C to 5°C, and the salinity changes from 26°C to 28°F. The average mesh bag is washed and inverted once a month. In March of the following year, as water temperature rises, daily water exchange capacity should increase from 50% to 100%.
Second, the test results
1. The survival rate of relatives was 150kg on July 4th, and on the 16th of July was used for oxytocin 85kg. The survival rate of pro-breeding was 56%.
2. The fertilized eggs that have more than 90% of the fertilized eggs emit sperm and eggs. The fertilized eggs are about 6 billion eggs and the egg diameter of the fertilized eggs is 58 μm.
3. Hatching rate From 7 pm to 10 pm on July 17th, D-shaped larvae were developed after 24 to 26 hours. A total of 5 billion D-shaped larvae were obtained, and the hatching rate was 83%. The initial D-shaped larval shell length is 85 μm and the shell height is 68 μm.
4. Survival rate of D-shaped larvae to the top of the shell On August 5, the survival of the larvae at the end of the shell was 1.25 billion, the survival rate was 28%, the shell length of the larvae was 270 μm to 300 μm, and the shell height was 180 μm to 201 μm.
5. Emergence of juvenile juveniles in ponds On August 25th, juveniles were randomly sampled before bagging out of the pool and measured an average of 620,000 seedlings per cubic meter of water. A total of 310 million seedlings emerged, and the metamorphosis rate of parasitized larvae was 31%. The length of the juvenile shell is 1.2mm to 0.82mm, and the shell height is 0.8mm to 0.55mm.
6. After the wintering, the juveniles finally emerged in early April. In early April, a total of 1,650 kg of shellfish were sold, with an average size of 54,600 pieces/kg, totaling 90 million pieces. The juveniles were bred and survived in winter for 29%.
Third, discuss
1. Whether the intimacy is induced by inducing production, inducing production, or not, depends on whether the intimal gonads are mature or not. After the mature pro-scorpion enters the pool, the sperm and eggs can be smoothly excreted after being induced by the dripping water. The survival rate of the pro-sputum and the hatching rate of the fertilized eggs are all Guaranteed. Immature intimacy requires intensified ripening. Because of the proneness to problems in the process of ripening, such as high water temperatures, diseases, etc., the survival rate of inbreeding and the hatching rate of fertilized eggs are often not guaranteed. On July 4, the intimacy of entering the pool, the gonads are mature, but due to catching up with the high temperature, the water temperature reached 29 °C ~ 30 °C, the result of the intimacy of the gonads has undergone severe degradation and a large number of deaths, since the spawning pro? With 85 kg remaining, the survival rate is only 55.6%. Therefore, it is very important to take timely and mature pro-taste to avoid raising the water temperature. The author believes that the best time for intimacy should be collected from the end of June to the beginning of July, and the incubation temperature should not exceed 27.5°C. After the mature pro-aesculia is broken, the appearance of gonads should be full, cover the entire bulging surface, and be lusterless. No wrinkle, clear microscopic examination, round or oval, sperm swims lively.
2. Larval cultivation From the results of larval rearing, the 28% survival rate of the larvae during the planktonic stage and the 31% of the metamorphosis rate of the larvae were unsatisfactory. The main reason for the analysis was the dietary quality problem. The larvae were predominantly golden algae in the early stage of cultivation, and mainly chlorella in the middle period. A small amount of cyanobacteria was found in the larvae. It can be seen that the fed biological composition was irrational and the variety was single. Should increase feeding diatoms, chlorella does not feed or less feeding; In addition, water quality sand filter effect is not good, the water is not a clean cause is also a reason.
3. Intermediate breeding and overwintering juveniles using net bags to hang bred and overwintering can effectively prevent harm to predator organisms, increase survival rate, and be easy to catch. There is no missing trapping loss. The shortage is the density of juveniles in bags. If it is too large, the mesh is easy to be blocked, water exchange and juvenile feeding are affected, and operations such as brushing the net bag are easy to cause damage to the juveniles. These conditions greatly affect the survival rate and growth rate of the juveniles, especially at 60 mesh. In the cultivation of bags, the impact was particularly obvious. In only 15 days to 20 days, the survival rate was only 48.3%. Therefore, strengthen and improve the cultivation and management at this stage, such as changing bags and seedlings in a timely manner, controlling reasonable cultivation densities, strengthening the exchange of water quality, avoiding excessive water quality, and avoiding friction and squeezing by operations such as bagging, transportation, hanging, and brushing. It is important.
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