Shellfish culture device, shellfish culture set, and culture method for shellfish

Abstract

To provide a shellfish culture device in which oxygen is easily distributed to each shellfish evenly even if a lot of shellfishes are cultured.SOLUTION: A shellfish culture device comprises: a diffusion cell 10 for being arranged near a bottom part in a culture water tank 100 installed on land; a culture cell 20 connected to an upper side of the diffusion cell 10, and for culturing shellfishes S thereinside; a seawater supply pipe 30 for supplying seawater taken from the outside of the culture water tank 100, into the diffusion cell 10; and oxygen amount increasing means 40 for increasing an amount of dissolved oxygen in the seawater in the seawater supply pipe 30. While a side surface part 10a and a bottom surface part 10b of the diffusion cell 10 and a side surface part 20a of the culture cell 20 are made water-impermeable, a connection portion between the diffusion cell 10 and the culture cell 20 is made water-permeable. High-oxygen seawater increased in the amount of dissolved oxygen by the oxygen amount increasing means 40 can be supplied to the shellfishes S in the culture cell 20 after being diffused in the diffusion cell 10.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a shellfish farming apparatus for farming shellfish. The present invention also relates to a shellfish farming set using this shellfish farming apparatus and a method for farming shellfish using the shellfish farming set.

Background Art

[0002] In recent years, mass mortality of farmed shellfish has become a major problem. Mass mortality mainly occurs in summer, and it is considered that one of the causes is the increase in seawater temperature due to global warming and the accompanying decrease in the dissolved oxygen content of seawater (hypoxia).

[0003] In view of such a situation, for example, in FIG. 1 of Patent Document 1, a suspended culture system 100 equipped with an oxygen supply device for supplying oxygen to shellfish is described. As shown in the figure, this suspended culture system 100 includes an on-water solar cell unit 10 having a solar cell module 11 and a float 12, a culture suspension 20 suspended from the on-water solar cell unit 10, and an oxygen supply device 30 for supplying oxygen to the shellfish held by the culture suspension 20. Paragraphs 0015 to 0016 and FIG. 2 of the same document describe that microbubbles 34 containing oxygen are ejected from the ejection nozzle 33 of the oxygen supply device 30 by the power supplied from the solar cell module 11, and dissolved oxygen is supplied to a plurality of shellfish held by the culture suspension 20.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the suspended aquaculture system 100 described in Patent Document 1, there was a risk that sufficient oxygen might not be supplied to some of the shellfish held in the aquaculture suspension body 20. That is, as shown in FIG. 1 of the same document, although a large number of shellfish are held in the aquaculture suspension body 20, microbubbles are likely to be supplied to the shellfish held near the ejection nozzle 33, while it is difficult for microbubbles to be supplied to the shellfish held at locations far from the ejection nozzle 33. For this reason, the shellfish held at locations where microbubbles are difficult to be supplied may still fall into an oxygen-deficient state and there is a risk of death. In other words, when attempting to perform aquaculture with few mortalities using the suspended aquaculture system 100 described in Patent Document 1, it is only possible to hold shellfish within the range where the microbubbles ejected from the ejection nozzle 33 can easily reach, and it is difficult to cultivate a large number of shellfish at one time.

[0006] The present invention has been made to solve the above problems, and provides a shellfish aquaculture apparatus capable of cultivating shellfish in a state where it is difficult for the shellfish to die by evenly supplying oxygen to each shellfish even when cultivating a large number of shellfish. Another object of the present invention is to provide a method for cultivating shellfish using this shellfish aquaculture apparatus.

Means for Solving the Problems

[0007] The above problems are solved by a shellfish aquaculture apparatus that can be used together with an aquaculture water tank installed on land, and that has a diffusion cell for arranging near the bottom inside the aquaculture water tank, an aquaculture cell connected above the diffusion cell for cultivating shellfish inside it, a seawater supply pipe for supplying seawater taken from outside the aquaculture water tank into the diffusion cell, and an oxygen amount increasing means for increasing the dissolved oxygen amount of the seawater in the seawater supply pipe and is provided with while the side surfaces and bottom surface of the diffusion cell, and the side surfaces of the aquaculture cell are made water-impermeable, The connection part between the diffusion cell and the cultivation cell is made water-permeable, so that highly oxygenated seawater with an increased dissolved oxygen content by the oxygen amount increasing means can be diffused in the diffusion cell and then supplied to the shellfish in the cultivation cell. Shellfish cultivation device is solved by providing the same.

[0008] Here, "shellfish" shall mean mollusks having shells. Also, "highly oxygenated seawater" is seawater whose dissolved oxygen content has been increased from seawater taken from outside the aquaculture tank, and the specific numerical value of its dissolved oxygen content is not limited. Depending on the dissolved oxygen content of the taken seawater, the dissolved oxygen content of "highly oxygenated seawater" may be lower than that of general seawater. The same shall apply hereinafter.

[0009] In this shellfish cultivation device, highly oxygenated seawater with an increased dissolved oxygen content by the oxygen amount increasing means is diffused in the diffusion cell and then supplied into the cultivation cell. Thereby, even when cultivating a large number of shellfish in the cultivation cell, it is possible to easily supply oxygen evenly to those shellfish. Therefore, even if the seawater outside the cultivation cell has fallen into a hypoxic state, it is possible to prevent the shellfish in the cultivation cell from suffering from oxygen deficiency, and effectively prevent a large number of mortalities of the shellfish during cultivation. In addition, since shellfish tend to have a deteriorated taste when in an oxygen-deficient state, by using the shellfish cultivation device according to the present invention, it is also possible to grow shellfish with a good taste.

[0010] In the shellfish cultivation device according to the present invention, it is preferable that the cultivation cell is formed by stacking a plurality of growing boxes in the vertical direction, where the side surfaces are water-impermeable and the bottom surface is mesh-shaped. Thereby, shellfish can be arranged in multiple stages within the cultivation cell, and more shellfish can be cultivated in a state where oxygen is evenly distributed. However, in this case, since the height of the growing box in the vertical direction tends to be small, there is a risk that the shellfish will be pushed up by the flow of seawater rising from the diffusion cell and jump out of the growing box. Therefore, it is preferable to further provide shellfish holding means for covering the shellfish with a mesh fabric and holding them inside the growing box. Thereby, while ensuring water permeability around the shellfish, it is possible to prevent the shellfish from jumping out of the growing box.

[0011] In the shellfish cultivation device according to the present invention, the oxygen amount increasing means includes an inner pipe communicated with the seawater supply pipe and having a large number of fine ventilation holes on its peripheral wall, an outer pipe covering the outside of the inner pipe, and gas supply means for supplying an oxygen-containing gas to the gap between the inner pipe and the outer pipe. It is preferable that the oxygen-containing gas supplied to the gap between the inner pipe and the outer pipe is supplied to the seawater inside the inner pipe in the form of fine bubbles through the ventilation holes of the inner pipe. By configuring the oxygen amount increasing means as described above, it is possible to increase the dissolved oxygen amount of the seawater (seawater in the seawater supply pipe) inside the inner pipe with high efficiency while being simple and low-cost. Also, the oxygen amount increasing means can be made compact.

[0012] In the shellfish farming apparatus according to the present invention, usually, a seawater supply pipe crosses the inside and outside of the aquaculture water tank, and seawater taken from the outside of the aquaculture water tank is supplied into the diffusion cell. The seawater supply pipe can also cross the inside and outside of the aquaculture water tank by being inserted into a hole formed in the side wall of the aquaculture water tank, for example. However, in this case, there is a risk of water leakage from the hole. In addition, if a hole is made in the aquaculture water tank, it may be difficult to use the aquaculture water tank for another purpose, for example, when the shellfish farming apparatus is not in use. For this reason, in the shellfish farming apparatus according to the present invention, it is preferable that the seawater supply pipe has an upward passing portion for passing above the side wall of the aquaculture water tank. Thereby, the seawater supply pipe can cross the inside and outside of the aquaculture water tank without making a hole in the aquaculture water tank.

[0013] The shellfish farming apparatus according to the present invention can be used as a shellfish farming set including the shellfish farming apparatus, a diffusion cell of the shellfish farming apparatus, and an aquaculture water tank capable of accommodating the diffusion cell and the aquaculture cell of the shellfish farming apparatus inside. This shellfish farming set can be used in a shellfish farming method for farming shellfish using this. In the shellfish farming apparatus according to the present invention, the shellfish farmed using the shellfish farming apparatus according to the present invention is not particularly limited in terms of its growth condition or type. The shellfish farming apparatus according to the present invention can be used for farming adult shellfish or for farming juvenile shellfish.

Advantages of the Invention

[0014] As described above, according to the present invention, it is possible to provide a shellfish farming apparatus capable of culturing shellfish in a state where it is difficult to kill the shellfish by making oxygen evenly accessible to each shellfish even when a large number of shellfish are cultured. It is also possible to provide a method for culturing shellfish using this shellfish farming apparatus.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0016] Preferred embodiments of the present invention will be described more specifically with reference to the drawings. In the following, for convenience of explanation, the direction that becomes upward when the shellfish cultivation apparatus is attached to the cultivation water tank may be expressed as "up", the direction that becomes substantially horizontal as "sideways", and the direction that becomes downward as "down".

[0017] 1. First Embodiment 1.1 Outline FIG. 1 is a photograph of the shellfish cultivation apparatus of the first embodiment. FIG. 2 is a schematic cross-sectional view of the shellfish cultivation apparatus of the first embodiment. In FIG. 2, a part of the shellfish cultivation apparatus and the cultivation water tank 100 is omitted and shown.

[0018] As shown in FIGS. 1 and 2, the shellfish farming apparatus of the first embodiment can be used as a shellfish farming set together with a farming water tank 100 installed on land, so that shellfish S such as oysters can be farmed on land. This shellfish farming apparatus includes a diffusion cell 10 arranged near the bottom inside the farming water tank 100, a farming cell 20 connected above the diffusion cell 10 for farming shellfish S therein, a seawater supply pipe 30 for supplying seawater taken from outside the farming water tank 100 into the diffusion cell 10, and an oxygen amount increasing means 40 for increasing the dissolved oxygen amount of the seawater in the seawater supply pipe 30 (hereinafter, seawater with the dissolved oxygen amount increased by the oxygen amount increasing means may be expressed as "high-oxygen seawater"). The side surface portion 10a and the bottom surface portion 10b of the diffusion cell 10, and the side surface portion 20a of the farming cell 20 are non-water-permeable. On the other hand, the connection portion between the diffusion cell 10 and the farming cell 20 is water-permeable as shown by the arrow F in FIG. 2. 2 As shown.

[0019] An intermediate portion (meaning a portion other than the upstream end portion and the downstream end portion in the seawater supply pipe 30, and not necessarily in the middle between the upstream end portion and the downstream end portion. The same applies hereinafter) or the upstream end portion of the seawater supply pipe 30 is provided with a seawater pump (not shown) for sending seawater taken from outside the farming water tank 100 into the seawater supply pipe 30. An oxygen amount increasing means 40 capable of increasing the dissolved oxygen amount of the seawater is provided in the intermediate portion of the seawater supply pipe 30. As a result, among the seawater in the seawater supply pipe 30, the seawater downstream of the location where the oxygen amount increasing means 40 is provided has a higher dissolved oxygen amount and becomes high-oxygen seawater. This high-oxygen seawater (artificially added oxygen) is supplied into the diffusion cell 10 by the seawater supply pipe 30 as shown by the arrow F in FIG. 2, diffused in the diffusion cell 10, and then as shown by the arrow F in FIG. 2. 1 As shown, it is supplied into the diffusion cell 10 by the seawater supply pipe 30, diffused in the diffusion cell 10, and then as shown by the arrow F in FIG. 2. 2As shown in , it is supplied to the shellfish S in the cultivation cell 20. Therefore, oxygen (hyperoxic seawater) can be evenly supplied to the shellfish in the cultivation cell 20, and even when a large number of shellfish are cultivated in the cultivation cell 20, regardless of the location where they are held in the cultivation cell 20, it is possible to make it difficult for the shellfish S to die. The seawater that has overflowed from the upper end of the cultivation cell 20 fills the cultivation water tank 100 and is then discharged to the outside of the cultivation water tank 100 by seawater discharge means (not shown).

[0020] The seawater supplied into the diffusion cell 10 through the seawater supply pipe 30 often contains shellfish feed such as plankton and artificial feed (for example, plankton originally contained in the seawater taken in, artificial feed artificially introduced into the seawater after intake, etc.). In this regard, in the shellfish cultivation apparatus of the present embodiment, not only oxygen but also shellfish feed is diffused in the diffusion cell 10 and then supplied to the cultivation cell 20. Therefore, not only oxygen but also shellfish feed can be evenly supplied to the shellfish in the cultivation cell 20.

[0021] In this way, when the shellfish cultivation apparatus of the present embodiment is used, even when a large number of shellfish are cultivated, oxygen and feed can be evenly and efficiently supplied to each shellfish. Therefore, it is possible to efficiently perform cultivation while preventing mass death of shellfish. In addition, since shellfish tend to lose their flavor when the hypoxic state continues, by using the shellfish cultivation apparatus of the present embodiment, it is also possible to raise shellfish with a good flavor.

[0022] The aquaculture water tank 100 is not particularly limited in terms of its material or size. In this embodiment, a so-called 1t resin water tank is adopted as the aquaculture water tank 100. The diffusion cells 10 and the aquaculture cells 20 included in one shellfish aquaculture device (put into one aquaculture water tank 100) may be only one each, or may be plural. In the shellfish aquaculture device of the first embodiment, as shown in FIG. 2, one aquaculture cell 20 is connected (loaded) to one diffusion cell 10, and as shown in FIG. 1, two sets of combinations of the diffusion cell 10 and the aquaculture cell 20 are provided. As shown in FIG. 2, the seawater supply pipe 30 branches inside the aquaculture water tank 100, and each of the branched branches is connected to each of the plurality of diffusion cells 10. Three or more sets of combinations of the diffusion cell 10 and the aquaculture cell 20 may be provided.

[0023] The seawater taken from outside the aquaculture water tank 100 and supplied to the diffusion cell 10 through the seawater supply pipe 30 may be taken from any location in the sea. As the seawater, for example, deep seawater taken from a relatively deep location in the sea, spring seawater, etc. can be used. Since deep seawater, spring seawater, etc. usually have a lower water temperature than the seawater near the sea surface, especially in seasons with high air temperatures, by using this, it becomes easier to keep the seawater temperature in the aquaculture water tank 100 at a water temperature suitable for the cultivation of the shellfish S without using a separate cooling device, etc. It is preferable to take deep seawater from a depth of 6m or more and 20m or less, and more preferably from a depth of 10m or more and 20m or less. It is also preferable to take deep seawater from a location where the distance to the seabed is within 1m.

[0024] The seawater pump (not shown) that creates the water flow in the seawater supply pipe 30 may be driven intermittently, but it is preferably driven continuously. Thereby, the flow of seawater passing from the diffusion cell 10 through the aquaculture cell 20 from bottom to top (arrow F 1 and arrow F 2It is possible to continuously generate the flow shown by (), and it is also possible to easily and firmly supply oxygen and shellfish feed to the shellfish S held in the upper part of the cultivation cell 20. Further, by continuously generating the water flow, it is possible to make it difficult for sessile organisms such as barnacles to adhere to the diffusion cell 10, the cultivation cell 20, the shellfish S in the cultivation cell 20, etc.

[0025] As shown in FIGS. 1 and 2, the shellfish cultivation apparatus according to the first embodiment further includes far-infrared radiation means 50 in an intermediate portion of the seawater supply pipe 30. This far-infrared radiation means 50 is for modifying seawater (more specifically, reducing the water clusters in seawater) by radiating far-infrared rays to the seawater in the seawater supply pipe 30. As shown in FIG. 2, this far-infrared radiation means 50 has a water pipe portion 51 for communicating with the seawater supply pipe 30, a far-infrared radiation layer 52 wound around the outside of the water pipe portion 51, and a protective layer 53 covering and protecting the outside of the far-infrared radiation portion 52. The material of the far-infrared radiation layer 52 is not particularly limited as long as it is a material that radiates far-infrared rays. In the present embodiment, as the material of the far-infrared radiation layer 52, a material in which powdered ceramics are held in foamed polyethylene is adopted.

[0026] In the shellfish cultivation apparatus according to the first embodiment, as shown in FIGS. 1 and 2, the seawater supply pipe 30 has an upward passing portion 31 for passing above the side wall of the cultivation water tank 100. When attaching the shellfish cultivation apparatus to the cultivation water tank 100, as shown in FIG. 1, the upward passing portion 31 is made to straddle the upper side of the side wall of the cultivation water tank 100. Thereby, the shellfish cultivation apparatus can be attached to the cultivation water tank 100 without making holes or the like in the cultivation water tank 100, and it is possible to prevent seawater from leaking from the holes or the like. Further, since there is no need to process the cultivation water tank 100, when the shellfish cultivation apparatus is not in use, the cultivation water tank 100 can be used for other purposes.

[0027] 1.2 Diffusion cell In the diffusion cell 10 of the shellfish farming device according to the first embodiment, as shown in FIG. 2, it is formed in a box shape with an open upper part. Both the side surface part 10a and the bottom surface part 10b of the diffusion cell 10 are non-water-permeable wall shapes. Substantially the entire upper surface part of the diffusion cell 10 serves as a culture cell connection opening 10c for connecting the culture cell 20. The material of the diffusion cell 10 is not particularly limited, but it is usually made of resin.

[0028] 1.3 Culture cell FIG. 4 is a perspective view of the growth box 21 used in the shellfish farming device according to the first embodiment (FIG. 4(a)), and a perspective view showing a state in which the growth box 21 is held by the growth box holding frame 23 (FIG. 4(b)). The culture cell 20 is detachably connected to the diffusion cell 10 by being loaded on the culture cell connection opening 10c of the diffusion cell 10. The bottom surface of the culture cell 20 is usually formed in a net shape and is in a state where water can pass through between the diffusion cell 10. The culture cell 20 may be configured to accommodate only the shellfish S at its bottom, but in this case, it may be difficult to culture a large number of shellfish S.

[0029] Therefore, in the shellfish farming device according to the first embodiment, as shown in FIG. 2, the culture cell 20 is formed by stacking a plurality of growth boxes 21 in the vertical direction. The side surface part 21a (FIG. 4(a)) of the growth box 21 is non-water-permeable. On the other hand, the bottom surface part 21b of the growth box 21 is in a mesh shape and is water-permeable. By putting the shellfish S in this growth box 21 and stacking them in multiple stages, more shellfish S can be held in the culture cell 20.

[0030] The number of stages of the cultivation box 21 forming the cultivation cells 20 for aquaculture is not limited. However, if the number of stages of the cultivation box 21 is too small, the number of shellfish S that can be cultured will decrease. If the number of stages of the cultivation box 21 is too large, there is a risk that the upper cultivation box 21 will protrude from the sea surface in the aquaculture water tank 100. For this reason, the number of stages of the cultivation box 21 forming the cultivation cells 20 for aquaculture is preferably 2 or more and 6 or less, and more preferably 3 or more and 5 or less. In the present embodiment, it is 4 stages.

[0031] The shellfish S may be directly placed in the cultivation box 21. However, when the cultivation boxes 21 are stacked to form the cultivation cells 20 for aquaculture, since the height of each cultivation box 21 has to be reduced, for example, when trying to culture small and light shellfish S, there is a risk that the shellfish S will come out of the cultivation box 21 due to the flow of seawater flowing from the bottom to the top in the cultivation cell 20. In this regard, in the present embodiment, shellfish holding means for covering the shellfish S with a mesh fabric and holding it in the cultivation box 21 is further provided. More specifically, as shown in Fig. 4(a), the shellfish S is placed in a shellfish holding bag 22 (shellfish holding means) formed of a mesh fabric, and the shellfish S together with the shellfish holding bag 22 is placed in the cultivation box 21. Thereby, it is possible to prevent the shellfish S from coming out of the cultivation box 21.

[0032] As shown in Fig. 4(a), the shellfish holding bag 22 is formed in a closed bag shape by sewing a mesh fabric into a box shape. A fastener 22a for taking the shellfish S in and out of the shellfish holding bag 22 is provided on the upper surface portion of the shellfish holding bag 22. As the fastener 22a, for example, a hook-and-loop fastener, a wire fastener (e.g., a zipper, etc.), a dot fastener (e.g., a snap button, etc.) can be adopted.

[0033] The material of the mesh fabric forming the shellfish holding bag 22 is usually a resin. In the present embodiment, the shellfish holding bag 22 is formed of a heat-sealed mesh woven fabric in which overlapping filaments are heat-sealed by heat-treating a woven fabric of heat-sealing resin filaments. Thereby, it is possible to make it difficult for the mesh size of the shellfish holding bag 22 to change. The mesh size of the shellfish holding bag 22 varies depending on the size of the shellfish S to be cultured and is not limited, but is preferably 0.5 mm or more and 5 mm or less, and more preferably 0.9 mm or more and 3 mm or less.

[0034] The material of the growing box 21 is not particularly limited, but is usually made of resin. The mesh size of the bottom surface portion 21b of the growing box 21 formed in a mesh shape is not particularly limited. However, if the mesh size of the bottom surface portion 21b is too small, there is a risk that the bottom surface portion 21b is likely to be clogged. For this reason, the mesh size of the bottom surface portion 21b is preferably 0.5 cm or more and 5 cm or less, and more preferably 1 cm or more and 3 cm or less. The mesh size of the bottom surface portion 21b in the present embodiment is about 2.4 cm.

[0035] The growing boxes 21 each containing the shellfish holding bag 22 (shellfish S) may be stacked one by one on the culture cell connection opening 10c of the diffusion cell 10. However, in this case, it may be time-consuming. Further, the culture water tank 100 usually has a certain depth (about several tens of cm to 1 m). When the growing boxes 21 are stacked one by one on the diffusion cell 10, in order to put the lower growing box 21 into and take out of the culture water tank 100, the operator has to bend the body and stretch the hand greatly into the culture water tank 100, which may cause too much physical burden on the operator. For this reason, in the first embodiment, as shown in FIG. 4(b), the stacked growing boxes 21 are loaded (connected) to the culture cell connection opening 10c of the diffusion cell 10 while being held by the growing box holding frame 23.

[0036] This cultivation box holding frame 23 has a support portion 23a for supporting the lowermost cultivation box 21 among a plurality of stacked cultivation boxes 21, a gripping portion 23b configured to be arranged near the upper end of the side wall of the aquaculture tank, and a connecting portion 23c connecting the support portion 23a and the gripping portion 23b. As shown in FIG. 4(b), with the cultivation boxes 21 stacked in multiple stages supported by the support portion 23a of the cultivation box holding frame 23, by gripping the gripping portion 23b and lifting the cultivation box holding frame 23, a plurality of cultivation boxes 21 can be handled collectively, saving labor. Also, a plurality of cultivation boxes 21 can be put into or taken out of the aquaculture tank 100 without the operator having to reach deeply into the aquaculture tank 100.

[0037] FIG. 5 is a diagram for explaining another aspect of the shellfish holding means. In the first embodiment, a closed - bag - shaped shellfish holding bag 22 (FIG. 4(a)) was adopted as the shellfish holding means. In other embodiments, as shown in FIG. 5(a), the shellfish holding means can be provided with a lower sheet 24a formed of a mesh fabric, an upper sheet 24b formed of a mesh fabric and overlapped on the upper side of the lower sheet 24a, and a pressing tool 24c for annularly pressing the overlapped lower sheet 24a and upper sheet 24b.

[0038] When holding the shellfish S in this shellfish holding means, as shown in FIG. 5(b), first, the lower sheet 24a is laid on the bottom surface portion 21b of the cultivation box 21, the shellfish S is placed thereon, and the upper sheet 24b is overlapped. The periphery of the bottom surface portion 21b in the overlapped lower sheet 24a and upper sheet 24b is annularly pressed by a pressing tool 24c formed in a square - frame shape along the shape of the bottom surface portion 21b. Thereby, the shellfish S can be confined between the lower sheet 24a and the upper sheet 24b so that the shellfish S does not come out of the cultivation box 21.

[0039] The shellfish holding means shown in Fig. 5 can be preferably adopted particularly when the shellfish S is a small juvenile shellfish about 1 to 2 mm in size. This is because the lower sheet 24a and the upper sheet 24b are simple sheet-like without seams or the like, so even if the mesh size is reduced, clogging is less likely to occur, and even if clogging occurs, it can be easily cleaned. The mesh size of the lower sheet 24a is not limited, but is preferably 0.4 mm or more and 1.5 mm or less, and more preferably 0.6 mm or more and 1 mm or less. The mesh size of the upper sheet 24b is also not limited, but is preferably 0.4 mm or more and 1.5 mm or less, and more preferably 0.6 mm or more and 1 mm or less. In the embodiment shown in Fig. 5, the mesh sizes of the lower sheet 24a and the upper sheet 24b are both about 0.8 mm.

[0040] 1.4 Oxygen amount increasing means Fig. 3 is an enlarged view of the periphery of the oxygen amount increasing means 40 in Fig. 2. The specific configuration of the oxygen amount increasing means 40 is not particularly limited as long as it can increase the dissolved oxygen amount of the seawater taken from the outside of the aquaculture water tank. In the present embodiment, the oxygen amount increasing means 40 is attached to the upper passage portion 31 in the seawater supply pipe 30 as shown in Fig. 1, but the position where the oxygen amount increasing means 40 is provided is not limited to this. The oxygen amount increasing means 40 can also be provided, for example, upstream of the far-infrared radiation means 50.

[0041] In the first embodiment, as shown in FIG. 3, the oxygen amount increasing means 40 has a double-tube structure including an inner tube 41 and an outer tube 42 covering the outside of the inner tube 41. Between the upstream end of the inner tube 41 and the upstream end of the outer tube 42, and between the downstream end of the inner tube 41 and the downstream end of the outer tube 42, they are respectively blocked by a blocking wall 43. A gas supply means 44 for supplying an oxygen-containing gas is connected to the outer tube 42, and as shown by the broken-line arrow in FIG. 3, the oxygen-containing gas can be supplied to the gap between the inner tube 41 and the outer tube 42. The inner tube 41 communicates with the seawater supply pipe 30, and the seawater flowing through the seawater supply pipe 30 passes through the inside of the inner tube 41. A large number of fine ventilation holes 41a (holes penetrating the peripheral wall of the inner tube 41) are provided on the peripheral wall of the inner tube 41. The oxygen-containing gas supplied to the gap between the inner tube 41 and the outer tube 42 by the gas supply means 44 becomes fine bubbles by passing through the ventilation holes 41a of the inner tube 41 and is supplied to the seawater inside the inner tube 41. Thereby, the dissolved oxygen amount of the seawater inside the inner tube 41 can be efficiently increased.

[0042] The size of the ventilation holes 41a is not particularly limited, but if it is too large, the bubbles of the oxygen-containing gas may become too large, making it difficult for the oxygen-containing gas to dissolve in the seawater. Also, there is a possibility that the seawater inside the inner tube 41 may easily leak into the gap between the inner tube 41 and the outer tube 42. For this reason, the diameter of the ventilation holes 41a is preferably 1 mm or less, and more preferably 0.7 mm or less. However, if the ventilation holes 41a are too small, the amount of the oxygen-containing gas passing through the ventilation holes 41a per unit time may be too small, making it difficult to efficiently increase the dissolved oxygen amount of the seawater inside the inner tube 41. For this reason, the diameter of the ventilation holes 41a is preferably 0.1 mm or more, and more preferably 0.3 mm or more. The number of the ventilation holes 41a provided in the inner tube 41 is not particularly limited either, but usually, it is 100 or more, preferably 300 or more, and more preferably 400 or more. The upper limit of the number of the ventilation holes 41a provided in the inner tube 41 is not limited either, but usually it is 10,000 or less.

[0043] The dimensions of the inner pipe 41 are not particularly limited. However, if the inner pipe 41 is too small, there is a risk that it will be difficult to efficiently increase the amount of dissolved oxygen in the seawater inside the inner pipe 41. On the other hand, if the inner pipe 41 is too large, the oxygen amount increasing means 40 may become bulky and obstructive. For this reason, the inner diameter (inside diameter) of the inner pipe 41 is preferably 20 mm or more and 80 mm or less, and more preferably 30 mm or more and 50 mm or less. Also, the length of the inner pipe 41 (the length along the water flow direction) is preferably 5 cm or more and 30 cm or less, and more preferably 10 cm or more and 20 cm or less. The inner pipe 41 in the present embodiment has an inner diameter of about 40 mm and a length of about 12 cm.

[0044] The width W of the gap between the inner pipe 41 and the outer pipe 42 1 (the difference between the outer radius of the inner pipe 41 and the inner radius of the outer pipe 42) is also not particularly limited. However, if the width W 1 is too large, there is a risk that it will be difficult to efficiently increase the amount of dissolved oxygen in the seawater inside the inner pipe 41. For this reason, the width W 1 is preferably 2 cm or less, and more preferably 1 cm or less. The lower limit of the width W 1 is not limited, but is usually 0.2 cm or more.

[0045] The oxygen-containing gas supplied by the gas supply means 44 is not particularly limited in its composition as long as it is a gas containing oxygen. As the oxygen-containing gas, for example, normal pressure air, normal pressure oxygen, high pressure air, concentrated oxygen (high pressure oxygen), etc. can be used. In the present embodiment, an air pump is employed as the gas supply means 44, and normal pressure air is employed as the oxygen-containing gas. The air supply rate of the air pump is not limited, but is preferably about 80 L / min to 200 L / min, and more preferably 100 L / min to 150 L / min. In the present embodiment, the air supply rate of the air pump is about 120 L / min.

[0046] In other embodiments, as the oxygen amount increasing means 40, for example, an ultrafine bubble generator (not shown) capable of generating ultrafine bubbles may be employed. In this case, the ultrafine bubble generator may directly generate ultrafine bubbles in the seawater in the seawater supply pipe 30 or the seawater in the diffusion cell 10. However, in this case, there may be insufficient space for arranging the ultrafine bubble generator. For this reason, it is preferable to pre-produce bubble water containing a large amount of ultrafine bubbles by the ultrafine bubble generator and supply this bubble water into the seawater supply pipe 30 or the diffusion cell 10.

[0047] The type of the ultrafine bubble generator is not particularly limited. As the ultrafine bubble generator, for example, an ultrafine bubble generator adopting a mode such as a static mixer type, a swirling liquid flow type, a pressure dissolution type, etc. can be used. More specifically, for example, "Aqua Silk" (registered trademark) manufactured by Hokkaido Nichimou Co., Ltd., which is a static mixer type ultrafine bubble generator, can be adopted.

[0048] In still other embodiments, by adopting an airlift pump as a seawater pump (not shown) for generating a water flow in the seawater supply pipe 30, the airlift pump (seawater pump) can also function as the oxygen amount increasing means 40. The airlift pump is a pump that transports water using the buoyancy of bubbles. When an airlift pump is used as the seawater pump, the dissolved oxygen amount of the seawater can be increased while transporting the seawater. Therefore, it is not necessary to separately provide the seawater pump and the oxygen amount increasing means 40, and the cost can be suppressed.

[0049] 1.5 Applications The shellfish farming device of the first embodiment can be suitably used for cultivating adult and juvenile oysters. The shellfish S (oysters) used for cultivation may be those collected by the single-seed method or those removed from the seed collector after being collected using a seed collector (e.g., scallop shells, etc.). A plurality of types of mesh fabrics with different mesh sizes are prepared for the shellfish holding means, and an appropriate one is used according to the size (shell height) of the shellfish S (oysters) to be cultivated.

[0050] The shellfish farming device of the first embodiment can also be used for cultivating adult oysters therein for a long period (for the purpose of growing or fattening oysters). However, as the oysters grow, it may become difficult to put all the oysters being cultivated into the cultivation cell 20. However, if we try to prepare a sufficient number of shellfish farming devices to accommodate all the oysters during cultivation, the cost may increase.

[0051] Therefore, a method of replacing the oysters cultivated in the shellfish farming device at regular intervals (hereinafter sometimes referred to as the "alternate cultivation method") can be considered. That is, all the oysters being cultivated are divided into a plurality of groups (two or more than three are also acceptable). While one group is being cultivated in the shellfish farming device, the remaining groups are cultivated in the sea outside the shellfish farming device (hereinafter sometimes simply expressed as the "outer sea"). After a certain period has passed, one group is moved from the shellfish farming device to the outer sea, and one of the other groups being cultivated in the outer sea is put into the shellfish farming device. Since shellfish have a higher tolerance to oxygen-deficient states compared to other marine organisms, they can withstand oxygen-deficient seawater for several days to about a week without dying. By this alternate cultivation method, more oysters than the capacity of the shellfish farming device can be cultivated in a state where they are less likely to die. In other words, a large number of oysters can be cultivated in a state where they are less likely to die with a small number of shellfish farming devices (at a low cost).

[0052] This replacement aquaculture method can be suitably used for the purpose of "preventing a large number of oysters that have grown to a certain size from dying en masse". That is, the mass death of oysters is likely to occur mainly in summer (from July to October). By culturing oysters that have already grown to a certain size (oysters scheduled to be shipped from the following autumn to winter) only in summer using the replacement aquaculture method, it is possible to prevent the oysters that have been painstakingly raised from dying en masse in summer just before shipment. When autumn arrives and the seawater temperature drops, the oysters can be transferred to the outer sea rich in shellfish feed, fattened up, and then shipped.

[0053] 2. Second Embodiment FIG. 6 is a schematic cross-sectional view of the shellfish aquaculture apparatus of the second embodiment. In the shellfish aquaculture apparatus of the first embodiment, two diffusion cells 10 and two culture cells 20 were provided respectively, and one culture cell 20 was connected on top of one diffusion cell 10. That is, substantially the entire upper surface of each diffusion cell 10 was used as a culture cell connection opening 10c for connecting the culture cell 20.

[0054] In contrast, in the shellfish aquaculture apparatus of the second embodiment, a plurality of culture cells 20 are connected on top of one diffusion cell 10. That is, as shown in FIG. 6, the diffusion cell 10 has an upper surface portion 10d that is non-water-permeable and plate-shaped or sheet-shaped, and a plurality of culture cell connection openings 10c are provided in the upper surface portion 10d. The plurality of culture cells 20 are respectively connected (loaded) on top of the plurality of culture cell connection openings 10c. For parts not described above, in the second embodiment, the same configurations as those described in the first embodiment can be adopted.

[0055] 3. Others The shellfish aquaculture apparatus according to the present invention is not particularly limited to the type of shellfish cultured using this apparatus. The shellfish aquaculture apparatus according to the present invention can be used for culturing, for example, bivalves (such as oysters, scallops, clams, abalones, whelks, ark clams, blood clams, cockles, etc.), gastropods (such as turban shells, conch shells, etc.), and sea urchins (such as sea urchins, etc.).

[0056] In the first and second embodiments, the shellfish were accommodated in the cultivation tank 21 while being held by the shellfish holding means. However, for example, when culturing burrowing shellfish (e.g., razor clams, littleneck clams, surf clams, Japanese littleneck clams, ark clams, blood ark clams, cockles, etc.), it is preferable to spread a sandy material in the cultivation tank 21 and culture those shellfish in the sandy material. In this case, the aperture of the bottom surface portion 21b of the cultivation tank 21 is preferably 1 mm or less. The sandy material preferably has a particle size of about 1 to 4 mm, more preferably about 2 to 3 mm. As the sandy material, for example, anthracite, natural sand, artificial sand, vermiculite, or a mixture of two or more of these can be used, and among them, it is preferable to use anthracite.

Explanation of Reference Numerals

[0057] 10 Diffusion cell 10a Side surface portion 10b Bottom surface portion 10c Opening for connecting the cultivation cell 10d Upper surface portion 20 Cultivation cell 20a Side surface portion 21 Cultivation tank 21a Side surface portion 21b Bottom surface portion 22 Shellfish holding bag (shellfish holding means) 22a Fastener 23 Cultivation tank holding frame 23a Support portion 23b Gripping portion 23c Connecting portion 24a Lower sheet 24b Upper sheet 24c Pressing tool 30 Seawater supply pipe 31 Upper passing portion 40 Oxygen amount increasing means 41 Inner pipe 41a Vent hole 42 Outer pipe 43 Blocking wall 44 Gas supply means 50 Far-infrared radiation means 51 Water pipe part 52 Far-infrared radiation layer 53 Protective layer 100 Aquaculture water tank S Shellfish

Claims

1. A shellfish farming apparatus that can be used together with an aquaculture water tank installed on land for farming shellfish, comprising: a diffusion cell for arranging near the bottom inside the aquaculture water tank; a farming cell connected to the upper side of the diffusion cell for farming shellfish inside thereof; a seawater supply pipe for supplying seawater taken from outside the aquaculture water tank into the diffusion cell; an oxygen content increasing means for increasing the dissolved oxygen content of the seawater in the seawater supply pipe; and; while the side surfaces and the bottom surface of the diffusion cell, and the side surfaces of the farming cell are made non-water-permeable, the connection part between the diffusion cell and the farming cell is made water-permeable, such that highly oxygenated seawater with an increased dissolved oxygen content by the oxygen content increasing means can be diffused in the diffusion cell and then supplied to the shellfish in the farming cell. Shellfish farming apparatus.

2. The shellfish farming apparatus according to claim 1, wherein the farming cell is formed by stacking a plurality of growing boxes in the vertical direction, the side surfaces of which are non-water-permeable and the bottom surfaces of which are mesh-shaped.

3. The shellfish farming apparatus according to claim 2, further comprising shellfish holding means for covering the shellfish with a mesh cloth and holding them inside the growing box.

4. The oxygen content increasing means is: an inner pipe communicated with the seawater supply pipe and having a large number of fine ventilation holes on its peripheral wall; an outer pipe covering the outside of the inner pipe; and gas supply means for supplying an oxygen-containing gas into the gap between the inner pipe and the outer pipe. It is configured to have, such that the oxygen-containing gas supplied into the gap between the inner pipe and the outer pipe is supplied into the seawater inside the inner pipe in the form of fine bubbles through the ventilation holes of the inner pipe. The shellfish farming apparatus according to claim 1.

5. The shellfish farming apparatus according to claim 1, wherein the seawater supply pipe has an upward passing portion for passing above the side wall of the aquaculture water tank.

6. A shellfish farming set comprising the shellfish farming apparatus according to any one of claims 1 to 5, and an aquaculture water tank capable of accommodating the diffusion cell and the farming cell of the shellfish farming apparatus inside thereof. Shellfish farming set.

7. A method for farming shellfish using the shellfish farming set according to claim 6.

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