Ascending and descending flow system for artificial breeding of branchiostoma belcheri and breeding method of branchiostoma belcheri

Abstract

The invention discloses an ascending and descending flow system for artificial breeding of branchiostoma belcheri and a breeding method of the branchiostoma belcheri, and belongs to the technical field of breeding of the branchiostoma belcheri. The lifting flow system comprises a cultivation pool, a water inlet pipe, a rotating shaft and a water outlet. According to the system, sewage at the bottom of the pond is discharged through downflow, sewage in water is discharged through upflow, a sand layer is loosened through rotation of the rotating shaft, and formation of algal membranes on the surface of the sand layer is prevented. By adopting the system to breed the branchiostoma, residual feed and excreta at the bottom of the pond and in the sand layer can be effectively removed, the water permeability of the sand layer can be effectively improved through the upward flow reverse osmosis effect, algal membranes on the surface of the sand layer are prevented from being formed, the ammonia nitrogen content in the water body is reduced, the dissolved oxygen content is increased, and a suitable environment is provided for the growth of the branchiostoma; the growth speed and the survival rate of the branchiostoma belcheri are improved

Description

Technical Field

[0001] The present invention belongs to the technical field of amphioxus cultivation, and particularly relates to an up-down flow system for artificial cultivation of amphioxus and a cultivation method for amphioxus. Background Art

[0002] Amphioxus belongs to the phylum Chordata, subphylum Cephalochordata, class Cephalochorda, and family Branchiostomidae. Amphioxus is a transitional group between invertebrates and vertebrates, known as a living fossil, and is an important model for studying the origin and evolution of vertebrates. Amphioxus lives by burrowing into sand, and has relatively high requirements for the ecological environment. There must be a bottom substrate environment and biological bait suitable for its life activities, as well as clean environmental conditions. During the artificial cultivation of amphioxus, a layer of fine sand is usually laid to meet its living requirements. However, residual bait and excrement are easily enriched on the surface of the sand layer, forming an algal film that causes the sand layer to harden. At the same time, harmful substances such as ammonia nitrogen in the water body will also increase, resulting in a decrease in the survival rate and growth rate of amphioxus. If the sand layer is frequently replaced, it is easy to cause damage to the amphioxus body and increase the risk of death. Summary of the Invention

[0003] Aiming at the problem that residual bait and excrement are easily enriched on the surface of the sand layer in the prior art, an up-down flow system for artificial cultivation of amphioxus and a cultivation method for amphioxus are provided.

[0004] An up-down flow system for artificial cultivation of amphioxus includes a cultivation pool and a water inlet pipe. Wherein, the support is located at the bottom of the cultivation pool. A layer of hollow bricks is arranged on the support, a layer of screen cloth is covered above the hollow brick layer, and a sand layer is further laid above the screen cloth layer. The water inlet pipe is provided with an upper water inlet and a lower water inlet that are respectively connected to the upper and lower parts of the cultivation pool. The cultivation pool is also provided with an upper drain port and a lower drain port.

[0005] Wherein, the up-down flow system for artificial cultivation of amphioxus further includes a rotating shaft, the rotating shaft is rotatably arranged in the cultivation pool, the rotating shaft is buried in the sand layer, the rotating shaft is driven to rotate by a motor arranged outside the cultivation pool, and a plurality of protrusions are arranged on the rotating shaft.

[0006] Wherein, for the up-down flow system for artificial cultivation of amphioxus, a sealing block is sleeved on the rotating shaft and fixedly installed on the cultivation pool through bolts. A first sealing strip is arranged between the sealing block and the cultivation pool, a second sealing strip is arranged between the sealing block and the rotating shaft, a bearing seat is installed on the cultivation pool, and the motor is installed on the bearing seat.

[0007] Wherein, for the up-down flow system for artificial cultivation of amphioxus, an annular groove is opened at the end face position of the sealing block for installing the first sealing strip.

[0008] Among them, in the upwelling and downwelling flow system for artificial cultivation of amphioxus, a V-shaped groove is opened in the inner hole of the sealing block for installing the second sealing strip.

[0009] A cultivation method of amphioxus is carried out using the above-mentioned upwelling and downwelling flow system for artificial cultivation of amphioxus. The specific steps are as follows: S1. Lay a layer of hollow bricks, a layer of screen cloth, and a layer of sand in sequence in the cultivation pool of the upwelling and downwelling flow system; and inject filtered fresh seawater. S2. Put the hatched and opened amphioxus larvae into the cultivation pool of the upwelling and downwelling flow system for cultivation. The stocking density is 100 - 160 tails / L; feed golden algae twice a day; change water once a day. The specific operation is: between two bait feedings, open the upper water inlet (21) and the lower water outlet (32), with a water change speed of 1 - 3 cm / s, the water inlet speed being the same as the water outlet speed, and start the rotation of the rotating shaft (4). The rotation speed of the rotating shaft (4) is 5 - 10 r / min; carry out the water change operation for 10 - 15 min. S3. When it starts to be observed that the amphioxus larvae begin to burrow into the sand, change water once a day. The specific operation is: between two bait feedings, open the upper water inlet (21) and the lower water outlet (32), with a water change speed of 1 - 3 cm / s, the water inlet speed being the same as the water outlet speed, carry out the water change operation for 10 - 20 min, and do not start the rotation of the rotating shaft 4. S4. After the amphioxus has completed burrowing into the sand, feed a mixed bait of golden algae and Chaetoceros twice a day; change water twice a day. The specific operation is: for the first water change, between two bait feedings, open the lower water inlet (22) and the upper water outlet (31), with a water change speed of 2 - 5 cm / s, the water inlet speed being the same as the water outlet speed, and start the rotation of the rotating shaft (4). The rotation speed of the rotating shaft (4) is 5 - 15 r / min; carry out the water change operation for 10 - 30 min; for the second water change, 6 h after the second bait feeding, open the upper water inlet (21) and the lower water outlet (32), with a water change speed of 1 - 3 cm / s, the water inlet speed being the same as the water outlet speed, and carry out the water change operation for 10 - 30 min.

[0010] Based on the above solution, the stocking density of amphioxus larvae in step S1 is 140 tails / L.

[0011] Based on the above solution, the water change speed in step S3 is 2 cm / s, and the water change duration is 15 min.

[0012] Based on the above solution, for the first water change in step S4, the water change speed is 4 cm / s, and the water change duration is 15 min; for the second water change, the water change speed is 2 cm / s, and the water change duration is 30 min.

[0013] Based on the above solution, the rotation speed of the rotating shaft in step S4 is 10 r / min.

[0014] Advantages of the present invention: The present invention provides an up-down flow system for artificial cultivation of amphioxus. The system discharges the dirt at the bottom of the pool through the down-flow, discharges the dirt in the water body through the up-flow, and loosens the sand layer by rotating the rotating shaft to prevent the formation of algal films on the surface of the sand layer.

[0015] Using the system of the present invention for amphioxus cultivation can effectively remove the residual bait and excrement at the bottom of the pool and in the sand layer. Through the reverse osmosis effect of the up-flow, the water permeability of the sand layer can be effectively increased, the formation of algal films on the surface of the sand layer can be prevented, the ammonia nitrogen content in the water body can be reduced, and the dissolved oxygen content can be increased, providing a suitable environment for the growth of amphioxus and improving the growth rate and survival rate of amphioxus.

[0016] The present invention also provides a method for cultivating amphioxus using the up-down flow system. The method is simple to operate, does not require frequent replacement of the sand layer, and reduces the risk of death caused by injury to amphioxus. The combination of the up-flow and down-flow in the up-down flow system can effectively prevent the formation of algal films on the surface of the sand layer, increase the permeability of the sand layer, and at the same time remove the excrement at the bottom of the pool and in the sand layer. By setting the flow rate of the water during water change and the rotation speed of the rotating shaft, the stress response of amphioxus can be reduced on the basis of reducing the content of harmful substances such as ammonia nitrogen in the water body; ensuring the survival rate and growth rate of amphioxus. It has an important application prospect in amphioxus cultivation. Description of the drawings

[0017] Figure 1 It is the structural schematic diagram of the embodiment of the present invention; Figure 2 It is Figure 1 The enlarged view of part A in Detailed implementation manners

[0018] To make the technical problems solved by the present invention, the technical solutions adopted and the achieved technical effects clearer, the technical solutions of the present invention will be further described below with reference to the drawings and through specific implementation manners. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only the parts related to the present invention are shown in the drawings rather than all of them.

[0019] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "clockwise" and "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. Embodiment

[0020] An up - down flow system for artificial cultivation of amphioxus (see Figure 1 - Figure 2 ), which includes a cultivation pond 1, a water inlet pipe 2, and a rotating shaft 4. Among them, a bracket 11 is located at the bottom of the cultivation pond 1. A hollow brick layer 12 is arranged on the bracket 11. Above the hollow brick layer 12, there is a layer of screen cloth layer 13. Above the screen cloth layer 13, a sand layer 14 is laid again. The rotating shaft 4 is rotatably arranged in the cultivation pond 1 and is buried in the sand layer 14. The rotating shaft 4 is driven to rotate by a motor 5 arranged outside the cultivation pond 1. A number of protrusions 41 are arranged on the rotating shaft 4.

[0021] The water inlet pipe 2 is provided with an upper water inlet 21 and a lower water inlet 22 that are respectively connected to the upper and lower parts of the cultivation pond 1. The cultivation pond 1 is also provided with an upper drain port 31 and a lower drain port 32. Water valves are arranged on the above - mentioned upper and lower water inlet and drain ports.

[0022] As Figure 2 shown, a sealing block 6 is sleeved on the rotating shaft 4 and is fixedly installed on the cultivation pond 1 through bolts. A first sealing strip 61 is arranged between the sealing block 4 and the cultivation pond 1. A second sealing strip 62 is arranged between the sealing block 4 and the rotating shaft 4. A bearing seat 42 is installed on the cultivation pond 1, and the motor 5 is installed on the bearing seat 42.

[0023] An annular groove is opened at the end face position of the sealing block 6 for installing the first sealing strip 61.

[0024] A V - shaped groove is opened in the inner hole of the sealing block 6 for installing the second sealing strip 62.

[0025] Through the sealing block 6, the first sealing strip 61 and the second sealing strip 62, a sealing effect can be achieved to prevent water leakage.

[0026] At the other end of the rotating shaft 4, a sealing block, a sealing strip, and a bearing seat are also provided, as Figure 1 shown.

[0027] Generally, artificial cultivation of amphioxus usually adopts sand - laying cultivation. The disadvantage of this method is that as the cultivation time increases, the amount of residual bait and excrement in the bottom of the pond and the sand layer increases, resulting in a continuous increase in the content of bacteria, ammonia nitrogen, nitrite, etc., threatening the growth and survival of amphioxus; on the other hand, the accumulation of residual bait will also cause an algal film to form on the surface of the sand layer, which is not conducive to the water permeability of the sand layer and affects the growth and survival of amphioxus.

[0028] The present invention discharges the residual bait and excrement in the sand layer through an up - flow. The specific method is as Figure 1As shown, the upper water inlet 21 is closed, the lower water inlet 22 is opened for water supply, the lower drain outlet 32 is closed, and the upper drain outlet 31 is opened for drainage. Thus, water sequentially passes through the hollow brick layer 12, the screen cloth layer 13, and the sand layer 14 from bottom to top and is discharged from the upper drain outlet 31. During the infiltration process, the residual bait and excrement in the sand layer are discharged together.

[0029] The residual bait and excrement on the surface of the sand layer are likely to form a surface algal film, and it is not sufficient to destroy it only by the scouring of water flow, which will cause the problem of incomplete discharge. Therefore, during the upflow discharge process, the rotating shaft 4 rotates, and the protrusion 41 slightly stirs the sand layer. During the loosening process of the sand layer, the algal film formed on the surface of the sand layer can be well destroyed, which is more conducive to discharge.

[0030] The present invention removes the dirt at the bottom of the pool through the downflow. The specific method is as Figure 1 shown, the upper water inlet is opened, the lower water inlet 22 is closed, the upper drain outlet 31 is closed, and the lower drain outlet 32 is opened. Water flows in from above, sequentially passes through the sand layer, the screen cloth layer, and the hollow brick layer, and finally is discharged from the lower drain outlet 32, discharging the dirt at the bottom of the pool. Embodiment

[0031] A method for cultivating amphioxus using a lift-flow system comprises the following steps: S1. Lay the hollow brick layer, the screen cloth layer, and the sand layer in sequence in the cultivation pool of the lift-flow system in Embodiment 1; and inject filtered fresh seawater. Among them, the height of the hollow brick layer is 5 - 10 cm, the pore size of the screen cloth layer is 200 - 300 meshes, the sand particle size of the sand layer is 0.1 - 0.5 mm; the thickness of the sand layer is 5 - 10 cm.

[0032] S2. Put the amphioxus larvae after hatching and opening their mouths into the cultivation pool of the above lift-flow system for cultivation, and the stocking density is 100 - 160 tails / L; feed the chrysophyceae twice a day (at 6:00 in the morning and 18:00 in the afternoon). Change the water once a day. The specific operation is: between the two bait feedings, open the upper water inlet 21 and the lower water outlet 32, the water change speed is 1 - 3 cm / s, the water inlet speed is the same as the water outlet speed, and start the rotating shaft 4 to rotate slowly, and the rotation speed of the rotating shaft 4 is 5 - 10 r / min; carry out the water change operation for 10 - 15 min.

[0033] S3. When it starts to be observed that the amphioxus larvae begin to burrow into the sand, change the water once a day. The specific operation is: between the two bait feedings, open the upper water inlet 21 and the lower water outlet 32, the water change speed is 1 - 3 cm / s, the water inlet speed is the same as the water outlet speed, carry out the water change operation for 10 - 20 min, and do not start the rotating shaft 4 to rotate.

[0034] S4. After the lancelets have finished burrowing, feed them a mixture of golden algae and horn algae twice a day (6:00 am and 18:00 pm). Change the water twice a day. The specific operation is: the first water change is between the two feedings (12:00 noon), open the lower water inlet 22 and the upper water outlet 31, the water change speed is 2-5cm / s, the water inlet speed is the same as the water outlet speed, and start the shaft 4 to rotate slowly, the speed of the shaft 4 is 5-15r / min, and the water change operation is carried out for 10-30min. The second water change is 6h after the second feeding (22:00 in the evening), open the upper water inlet 21 and the lower water outlet 32, the water change speed is 1-3cm / s, the water inlet speed is the same as the water outlet speed, and the water change operation is carried out for 10-30min. After the lancelets grow to the appropriate size, they will be released for reproduction. Example

[0035] The method of using the up-down flow system to cultivate lancelets, the steps are as follows: S1. In the cultivation pool of the ascending and descending flow system of Example 1, a hollow brick layer, a silk sieve cloth layer and a sand layer are laid in sequence; and filtered fresh seawater is injected. The height of the hollow brick layer is 8 cm, the aperture of the silk sieve cloth layer is 250 mesh, the sand particle size of the sand layer is 0.1-0.5 mm, and the thickness of the sand layer is 8 cm.

[0036] S2. The hatched lancelets are placed in the cultivation pond of the above-mentioned ascending and descending flow system for cultivation, with a stocking density of 140 larvae / L; golden algae are fed twice a day (6:00 a.m. and 18:00 p.m.). The water is changed once a day, and the specific operation is: between the two feedings, the upper water inlet 21 and the lower water outlet 32 ​​are opened, the water change speed is 2 cm / s, the water inlet speed is the same as the water outlet speed, and the shaft 4 is started to rotate slowly, and the speed of the shaft 4 is 5 r / min; the water change operation is performed for 10 minutes.

[0037] S3. When the lancelet larvae are observed to begin to burrow into the sand, the water is changed once a day. The specific operation is as follows: between two feedings, the upper water inlet 21 and the lower water outlet 32 ​​are opened, the water change speed is 2 cm / s, the water inlet speed is the same as the water outlet speed, the water change operation is performed for 15 minutes, and the rotation of the shaft 4 is not started.

[0038] S4. After the lancelets have finished burrowing, feed them a mixture of golden algae and horn algae twice a day (6:00 am and 18:00 pm). Change the water twice a day. The specific operation is: the first water change is between the two feedings (12:00 noon), open the lower water inlet 22 and the upper water outlet 31, the water change speed is 4cm / s, the water inlet speed is the same as the water outlet speed, and start the shaft 4 to rotate slowly, the speed of the shaft 4 is 10r / min, and the water change operation is carried out for 15min. The second water change is 6h after the second feeding (22:00 in the evening), open the upper water inlet 21 and the lower water outlet 32, the water change speed is 2cm / s, the water inlet speed is the same as the water outlet speed, and the water change operation is carried out for 30min. After the lancelets grow to the appropriate size, they will be released for reproduction.

[0039] On the basis of Example 3, the stocking density of step S2 was set to 100 tails / L, 120 tails / L, 140 tails / L, and 160 tails / L respectively; the other conditions remained unchanged, and the ammonia nitrogen (NH3-N) content and dissolved oxygen (DO) content of the aquaculture water body of the pre-sand larvae were detected by Nessler's reagent spectrophotometry and iodine titration (Winkler method) before feeding the feed every day. Each group was tested 3 times for 3 consecutive days, and the average value was calculated. The results are shown in Table 1.

[0040] Table 1 Effect of stocking density of lancelet fry on water quality

[0041] As shown in Table 1, the stocking density of lancelet seedlings has a certain effect on the ammonia nitrogen content and dissolved oxygen content of the aquaculture water. With the increase of stocking density, the ammonia nitrogen content gradually increases, and the dissolved oxygen content gradually decreases. The requirements of lancelet on water quality are very high, especially for larvae. Therefore, in order to ensure the quality of aquaculture water, the stocking density of lancelet should not exceed 140 / L.

[0042] On the basis of Example 3, the water change speed of the lancelet burrowing in the sand in step S3 was set to 1 cm / s, 2 cm / s, and 3 cm / s respectively; three water change durations of 10 min, 15 min, and 20 min were set for each water change speed; and the group with a water change speed of 2 cm / s, a duration of 15 min, and the rotation of the shaft 4 (5 r / min) was set as the control group. The survival rate of the lancelet larvae was counted, and the results are shown in Table 2.

[0043] Table 2 Effects of water exchange methods on the survival rate of larvae of amphioxus during burrowing

[0044] As can be seen from Table 2, when the water change speed is 1 cm / s, the survival rate of the buried sand seedlings increases with the increase of the water change time. At this time, the water change speed is relatively slow, and the stress on the larvae of amphioxus is not significant. With the increase of the water change duration, the ammonia nitrogen content in the water body will decrease significantly, which is beneficial to the survival of amphioxus. When the water change speed is 2 cm / s, the survival rate of the buried sand seedlings is relatively high. At this time, the water change speed is relatively gentle, and the short-term water change has little impact on the survival rate of amphioxus. When the water change duration is 20 min, the survival rate of amphioxus decreases slightly. When the water change speed is 3 cm / s, the water flow speed is relatively large, and the stress on the buried sand larvae of amphioxus is also relatively large. The survival rate of amphioxus decreases significantly and decreases with the increase of the water change duration. When the water change speed is 2 cm / s, the water change duration is 15 min, and the rotating shaft 4 is started to rotate during the water change. At this time, the survival rate of amphioxus decreases significantly, only 31.72%. This is because the rotation of the rotating shaft interferes with the sand burial of amphioxus, causing relatively large stress on amphioxus, so the survival rate decreases significantly.

[0045] On the basis of Example 3, the following methods are respectively adopted for water change in step S4: ① Change water once a day. The specific operation is as follows: The water change is carried out between two bait feedings (at 12:00 noon). Open the 22nd water inlet and the 31st water outlet. The water change speed is 4 cm / s, the water inlet speed is the same as the water outlet speed, and start the slow rotation of the rotating shaft 4. The rotation speed of the rotating shaft 4 is 10 r / min; Carry out the water change operation for 15 min.

[0046] ② Change water once a day. The specific operation is as follows: The water change is carried out 6 h after the second bait feeding (at 22:00 at night). Open the 21st upper water inlet and the 32nd lower water outlet. The water change speed is 2 cm / s, the water inlet speed is the same as the water outlet speed, and carry out the water change operation for 30 min.

[0047] ③ When changing water for the first time, the rotation speed of the rotating shaft 4 is 5 r / min; The rest is the same as in Example 3.

[0048] ④ When changing water for the first time, the rotation speed of the rotating shaft 4 is 15 r / min; The rest is the same as in Example 3.

[0049] The ammonia nitrogen (NH3-N) content and dissolved oxygen (DO) content of the aquaculture water body before bait feeding every day of the amphioxus after sand burial cultured by the above ①-④ and the water change methods in Example 3 are detected by the Nessler reagent spectrophotometry and the iodometric method (Winkler method). Each group is detected 3 times for 3 consecutive days, and the average value is obtained, and the survival rate of the adult amphioxus is counted. The results are shown in Table 3.

[0050] Table 3 Influence of water change methods on the aquaculture water quality of amphioxus after sand burial

[0051] As can be seen from Table 3, different water-changing methods have a certain impact on the ammonia nitrogen content and dissolved oxygen content in the amphioxus culture water body. When the water is changed only once a day, the ammonia nitrogen content in the water body is significantly higher than that in the water body with water changed twice, and the dissolved oxygen content is significantly lower than that in the water body with water changed twice. During water change, the rotation speed of the rotating shaft has little impact on water quality, but has a certain impact on the survival rate of adults; when the rotation speed of the rotating shaft is low (5 r / min), the pollutants in the sand layer are not completely removed, which has a certain impact on the survival rate of amphioxus adults. When the rotation speed of the rotating shaft is high (15 r / min), the pollutants in the sand layer are removed more thoroughly, but the excessive rotation speed has a greater stress response on amphioxus and also causes a certain decrease in the survival rate. Therefore, the water-changing method of Example 3 is the most suitable.

[0052] The above embodiments only illustrate the basic principles and characteristics of the present invention. The present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, there are various changes and modifications to the present invention, and these changes and modifications all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. An ascending and descending flow system for artificial cultivation of lancelets, characterized in that: It comprises a cultivation pool (1), a water inlet pipe (2), The support (11) is located at the bottom of the cultivation pool (1), a hollow brick layer (12) is arranged on the support (11), a silk sieve cloth layer (13) is arranged above the hollow brick layer (12), and a sand layer (14) is laid above the silk sieve cloth layer (13). The water inlet pipe (2) is provided with an upper water inlet (21) and a lower water inlet (22) respectively connected to the upper part and the lower part of the cultivation pool (1), and the cultivation pool (1) is also provided with an upper drainage outlet (31) and a lower drainage outlet (32).

2. The ascending and descending flow system for artificial cultivation of lancelet according to claim 1, characterized in that: The invention also comprises a rotating shaft (4), which is rotatably arranged in the cultivation pool (1), the rotating shaft (4) being buried in the sand layer (14), the rotating shaft (4) being driven to rotate by a motor (5) arranged outside the cultivation pool (1), and a plurality of protrusions (41) being arranged on the rotating shaft (4).

3. The ascending and descending flow system for artificial cultivation of lancelets according to claim 2, characterized in that: The sealing block (6) is sleeved on the rotating shaft (4) and fixedly mounted on the cultivation tank (1) by means of bolts; the first sealing strip (61) is arranged between the sealing block (6) and the cultivation tank (1); the second sealing strip (62) is arranged between the sealing block (4) and the rotating shaft (4); the bearing seat (42) is mounted on the cultivation tank (1); and the motor (5) is mounted on the bearing seat (42).

4. The ascending and descending flow system for artificial cultivation of lancelet according to claim 3, characterized in that: An annular groove is provided at the end surface of the sealing block (6) for mounting a first sealing strip (61).

5. The ascending and descending flow system for artificial cultivation of lancelet according to claim 3, characterized in that: A V-shaped groove is provided in the inner hole of the sealing block (6) for mounting a second sealing strip (62).

6. A method for cultivating lancelet, characterized in that: The method is carried out using the ascending and descending flow system for artificial cultivation of lancelets according to any one of claims 1 to 5, wherein the specific steps are as follows: S1. Lay a hollow brick layer, a silk screen layer and a sand layer in the cultivation pool of the up-down flow system in sequence; and inject filtered fresh seawater; S2. The hatched lancelet larvae are placed in a cultivation pond of an ascending and descending flow system for cultivation at a density of 100-160 larvae / L; golden algae are fed twice a day; and the water is changed once a day. Specifically, between two feedings, the upper water inlet (21) and the lower water outlet (32) are opened, the water change speed is 1-3 cm / s, the water inlet speed is the same as the water outlet speed, and the shaft (4) is started to rotate, and the rotation speed of the shaft (4) is 5-10 r / min; the water change operation is performed for 10-15 minutes; S3. When the lancelet larvae are observed to begin to burrow into the sand, the water is changed once a day. The specific operation is as follows: between two feedings, open the upper water inlet (21) and the lower water outlet (32), and change the water at a speed of 1-3 cm / s. The water inlet speed is the same as the water outlet speed. The water change operation is performed for 10-20 minutes without starting the rotation of the shaft 4. S4. After the lancelets have finished burrowing, they are fed a mixed diet of golden algae and horn algae twice a day. The water is changed twice a day. The specific operation is as follows: the first water change is between the two feedings. The lower water inlet (22) and the upper water outlet (31) are opened. The water change speed is 2-5 cm / s. The water inlet speed is the same as the water outlet speed. The shaft (4) is started to rotate. The speed of the shaft (4) is 5-15 r / min. The water change operation is performed for 10-30 minutes. The second water change is 6 hours after the second feeding. The upper water inlet (21) and the lower water outlet (32) are opened. The water change speed is 1-3 cm / s. The water inlet speed is the same as the water outlet speed. The water change operation is performed for 10-30 minutes.

7. The method for cultivating lancelet according to claim 6, characterized in that: In the step S1, the stocking density of juvenile Chinese otter is 140 larvae / L.

8. The method for cultivating lancelet according to claim 6, characterized in that: The water changing speed in step S3 is 2 cm / s, and the water changing time is 15 min.

9. The method for cultivating lancelet according to claim 6, characterized in that: The first water changing speed of step S4 is 4 cm / s, and the water changing time is 15 min; the second water changing speed is 2 cm / s, and the water changing time is 30 min.

10. The method for cultivating lancelets according to any one of claims 6 to 9, characterized in that: In step S4, the rotating shaft speed is 10 r / min.

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