Aquarium for raising larvae and larvae raising device

Abstract

To provide an aquarium capable of increasing the number of larval fish raised (production efficiency) while reducing the occurrence of abnormalities (dislocation, deformity, etc.) in the larval fish. [Solution] An aquarium for raising larvae has a flat section extending laterally, a pair of curved sections connected to one and the other horizontal ends of the flat section and bulging out in opposite directions in the horizontal direction and extending upward, and a pair of side sections connected to each of the pair of curved sections and extending upward. When the horizontal distance between the upper ends of the pair of side sections is W (mm) and the height from the flat section to the upper ends of the pair of side sections is H (mm), the relationship 1.12≦W / H≦1.90 is satisfied.

Description

[Technical field]

[0001] The present invention relates to an aquarium for raising larvae and a larvae raising device including the aquarium. [Background technology]

[0002] Conventionally, tanks for raising eel larvae have been proposed. For example, Patent Document 1 proposes a tank with a kamaboko-shaped bottom (length 1800 mm × width 800 mm × height 800 mm). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication WO2015 / 093616 Summary of the Invention [Problem to be solved by the invention]

[0004] In the aquarium of Patent Document 1, the bottom surface is formed of a continuous concave curved surface, and the lowest part of the bottom surface protrudes downward. With such a bottom shape, when feeding the larvae in the aquarium, the food supplied to the aquarium is concentrated in the curved part (lower end part) of the bottom surface of the aquarium. This narrows the feeding area, making it difficult to efficiently feed the many larvae in the aquarium. Therefore, the aquarium of Patent Document 1 has room for improvement in terms of increasing the number of larvae reared, that is, the number of larvae produced per unit volume of water (also known as production efficiency).

[0005] In addition, if the larvae remain near the bottom of the tank after feeding, they may rub their heads against the bottom of the tank, resulting in dislocation of the jaw (dislocation). In order to reduce this phenomenon, it is necessary to drive the larvae remaining near the bottom after feeding away from the bottom by using a water current that flows at an appropriate speed. On the other hand, if the water current is too fast, the larvae are more likely to have deformities, such as broken spines. In order to reduce the occurrence of abnormalities (dislocation, deformities, etc.) in the larvae (when the water current speed (amount of water poured per specified time) into the tank is constant from the viewpoint of facilitating water injection control, it is necessary to appropriately set the shape of the tank so that the water current flows at an appropriate speed along the inner surface (including the bottom surface) of the tank. The shape of the tank in Patent Document 1 is not set with consideration given to reducing the occurrence of abnormalities in the larvae, and there is room for improvement in this respect as well.

[0006] The present invention has been made to solve the above-mentioned problems, and its object is to provide an aquarium for rearing larvae, which can increase the number of larvae reared (production efficiency) while reducing the occurrence of abnormalities in the larvae (dislocation, deformity, etc.) by appropriately setting the shape of the aquarium, and a larvae rearing device equipped with said aquarium. [Means for solving the problem]

[0007] According to one aspect of the present invention, an aquarium for raising larvae has a flat portion extending in a horizontal direction, a pair of curved surface portions connected to one end and the other end of the flat portion in the horizontal direction and extending upward by bulging out in opposite directions in the horizontal direction, and a pair of side surfaces connected to each of the pair of curved surface portions and extending upward, wherein when the distance in the horizontal direction between each upper end of the pair of side surfaces is W (mm) and the height from the flat portion to each upper end of the pair of side surfaces is H (mm), 1.12≦W / H≦1.90 (1) Satisfy.

[0008] According to another aspect of the present invention, a larval fish rearing device comprises the above-mentioned aquarium, a water injection section for injecting water into the aquarium, and a drainage section for draining water that is injected into the aquarium and exceeds a specified capacity of the aquarium.

[0009] According to yet another aspect of the present invention, a larval fish rearing device comprises the above-mentioned aquarium, a water injection section for injecting water into the aquarium, and a drainage section for draining water that has been injected into the aquarium and exceeds a specified capacity of the aquarium, wherein the water injection section has a water injection pipe extending in the longitudinal direction of the aquarium, the water injection pipe having a plurality of water injection ports formed in a row in the longitudinal direction, and the drainage sections are arranged in a row in the longitudinal direction, the number of which is less than the number of the water injection ports. Effect of the Invention

[0010] It is possible to increase the number of larvae reared (production efficiency) while reducing the occurrence of abnormalities (dislocation, deformity, etc.) in the larvae. [Brief description of the drawings]

[0011] [Figure 1] 1 is a perspective view showing a schematic configuration of an apparatus for rearing larvae according to one embodiment of the present invention; [Diagram 2] FIG. 2 is a plan view showing the schematic configuration of a water inlet and drainage section of the aquarium provided in the breeding device. [Diagram 3] 4 is a front view showing the configuration of the drainage section of the water tank. FIG. [Figure 4] 2 is a cross-sectional view of the water tank taken along a plane perpendicular to the longitudinal direction. FIG. [Diagram 5] FIG. 4 is a cross-sectional view showing another configuration of the water tank. [Figure 6] FIG. 11 is a cross-sectional view showing still another configuration of the water tank. [Figure 7] FIG. 11 is a cross-sectional view showing the configuration of a water tank of a comparative example. [Figure 8] 1 is a graph showing a schematic diagram of the degree of growth of larvae by day age when the larvae were reared in half-pipe tanks of different lengths. [Figure 9] 1 is a graph showing a schematic diagram of the degree of growth of larvae by day age when the larvae were reared in Kreisel aquariums of different diameters. [Figure 10]FIG. 2 is an explanatory diagram showing a schematic diagram of water flow distribution in a cross section perpendicular to the longitudinal direction in each water tank of the examples and the comparative examples. [Figure 11] FIG. 10 is an explanatory diagram showing a schematic distribution of water flow in the longitudinal direction in each water tank of the embodiment. [Figure 12] FIG. 10 is an explanatory diagram showing a schematic diagram of the distribution of water flow in the longitudinal direction in each water tank of the examples and the comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The following describes an embodiment of the present invention with reference to the drawings.

[0013] [1. About the breeding equipment] (1-1. Overview of the breeding equipment) Fig. 1 is a perspective view showing the schematic configuration of a larval fish breeding apparatus 100 of this embodiment. The breeding apparatus 100 includes an aquarium 10, a water injection section 20, and a drainage section 30. In this embodiment, eel larvae are considered as an example of the larval fish to be breeded. Note that the breeding apparatus 100 of this embodiment can also be applied to breeding larval fish other than eels.

[0014] The water tank 10 has a generally U-shaped cross section and is elongated in one direction. For the sake of convenience in the following explanation, directions are defined as follows in this specification. First, the direction in which the water tank 10 extends (longitudinal direction, depth direction) is defined as direction A. Two directions perpendicular to each other in a cross section perpendicular to direction A are defined as direction B and direction C, respectively. Direction B is the height direction of water tank 10, i.e., the up-down direction. Direction C is the lateral direction (width direction) of water tank 10.

[0015] The water tank 10 has a wall 10W that is open at the top and concave at the bottom. The wall 10W extends in the A direction and connects the front wall 10F and the rear wall 10B. The front wall 10F and the rear wall 10B are located on opposite sides in the A direction. The water tank 10 is installed in a predetermined position with the wall 10W supported by a plurality of ribs 40. Further details of the water tank 10 will be described later.

[0016] Rearing water is supplied into the aquarium 10 by the water injection unit 20. The rearing water is, for example, seawater. Hereinafter, the rearing water will be simply referred to as "water". Larvae are raised in the aquarium 10 by putting them into the water in the aquarium 10 and feeding them periodically. When feeding, water injection by the water injection unit 20 is stopped, and water injection is resumed after feeding. A predetermined amount of water is stored in the aquarium 10 by injecting water by the water injection unit 20. Water that exceeds the above-mentioned amount due to water injection (overflow water) is drained from the drainage unit 30.

[0017] Thus, the breeding device 100 comprises an aquarium 10 for breeding larvae, a water injection unit 20 that injects water into the aquarium 10, and a drainage unit 30 that drains water that is injected into the aquarium 10 and exceeds a predetermined capacity of the aquarium 10. In this configuration, water injection by the water injection unit 20 and drainage by the drainage unit 30 can be performed simultaneously, thereby generating an appropriate water flow in the aquarium 10. Therefore, in terms of forming a flow field in the aquarium 10 that is favorable for the larvae, it can be said that it is desirable for the breeding device 100 to have the above configuration.

[0018] Feeding is carried out, for example, as follows. A feeding tube is inserted from the top of the aquarium 10 toward the bottom, and food is placed (applied) on the bottom through the feeding tube. When a lighting device placed above the aquarium 10 is turned on, the larvae move (swim) in the opposite direction to the lighting device due to their habit (negative phototaxis). In other words, the larvae move from the top to the bottom inside the aquarium 10. When the larvae reach the food placed on the bottom of the aquarium 10, they ingest the food. Feeding in this manner is carried out, for example, five times a day, every two hours, but the frequency of feeding can be adjusted as appropriate depending on the type of larvae, the breeding season, etc.

[0019] If food remains on the bottom of the aquarium 10, the bottom of the aquarium 10 and the water in the aquarium 10 will become dirty, and bacteria will easily grow in the aquarium 10. Since larvae are weak against bacteria, the aquarium 10 needs to be cleaned periodically. For this reason, for example, two aquariums 10 are provided side by side, and aquarium change is performed periodically (for example, every other day) by transferring the larvae in one aquarium 10 to the other aquarium 10. By such aquarium change, even while one aquarium 10 is being cleaned, the larvae can be continuously raised in the other aquarium 10. Note that the aquarium change can be performed, for example, by connecting the connection ports 10P provided on the front wall portions 10F of the two aquariums 10 with a hose, and using the principle of a siphon, transferring the water in one aquarium 10 to the other aquarium 10 through the hose.

[0020] (1-2. Details of the water injection and drainage sections) 2 is a plan view showing the schematic configuration of water injection section 20 and drainage section 30 of water tank 10. Water injection section 20 injects water into water tank 10. Such water injection section 20 has water injection pipe 21 and connection pipe 22. Water injection pipe 21 is a pipe that extends in direction A, that is, in the longitudinal direction of water tank 10.

[0021] The water injection pipe 21 has a plurality of water injection ports 21a. The water injection ports 21a are formed side by side in the A direction at the lower end of the outer circumferential surface of the water injection pipe 21. In this embodiment, nine water injection ports 21a are provided on each side in the A direction from the center of the water injection pipe 21. That is, the number of water injection ports 21a is 18 in total. Note that the number of water injection ports 21a is not limited to 18, and may be another number.

[0022] Connection pipe 22 is connected to near the center of water injection pipe 21 in direction A. The end of connection pipe 22 opposite water injection pipe 21 is connected to a water supply pump via a connection hose.

[0023] Water supplied from the water supply pump and flowing through the connecting pipe 22 branches off at the connection with the water injection pipe 21 and flows in opposite directions in the A direction. Then, water is supplied (injected) into the water tank 10 from each water injection port 21a aligned in the A direction.

[0024] Two drainage sections 30 are provided side by side at an interval in direction A. The two drainage sections 30 are located on opposite sides of the center of water injection pipe 21 in direction A, and are located equidistant from the center of water injection pipe 21. In other words, the two drainage sections 30 are located symmetrically with respect to the center of water injection pipe 21 in direction A. The number of drainage sections 30 is not limited to the above two, and may be one, or three or more.

[0025] FIG. 3 is a front view showing the configuration of the drainage section 30 and its vicinity of the aquarium 10. The drainage section 30 has a drainage tube section 31 and a main body section 32. The drainage tube section 31 is a tube extending in the B direction. An inlet 31a through which the water in the aquarium 10 flows is located at the lower end of the drainage tube section 31. When the position of the water surface when a predetermined amount of water is stored in the aquarium 10 is set to S0, the drainage tube section 31 is fixed to the aquarium 10 via the main body section 32 so that the inlet 31a is located below the position S0. The water injection pipe 21 of the water injection section 20 described above is also located below the position S0.

[0026] A strainer 31b is attached to the drain tube portion 31. The strainer 31b is a mesh-like member and is provided so as to surround the inlet 31a. The strainer 31b prevents the larvae in the aquarium 10 from entering the inlet 31a.

[0027] The main body 32 extends in the C direction and communicates with the drain tube 31. The main body 32 is provided by penetrating the wall 10W of the aquarium 10. The main body 32 is fixed to the wall 10W of the aquarium 10 so that its lowest portion is located at the same position as or lower than position S0.

[0028] The water in the aquarium 10 passes through the mesh (gaps) of the strainer 31b, enters the inlet 31a, and enters the inside of the drain tube portion 31. When the water injection portion 20 injects more water than a predetermined capacity into the aquarium 10, the water level inside the drain tube portion 31 attempts to rise beyond position S0. Because the drain tube portion 31 is connected to the main body portion 32, the water exceeding position S0 flows into the main body portion 32 and is discharged outside the aquarium 10.

[0029] In this embodiment, the number of drainage sections 30 is two, which is fewer than the number of water inlets 21a of the water injection section 20 (e.g., 18). In this case, the flow of water injected from the water inlet 21a, flowing through the aquarium 10 and toward the drainage section 30 can be spread in the direction A. Therefore, from the viewpoint of forming a flow field in the aquarium 10 that is favorable for the larvae, it is desirable to arrange the drainage sections 30 in a row in the direction A in a number fewer than the number of water inlets 21a.

[0030] In order to reliably form a flow field favorable for larvae in aquarium 10, it is desirable to make the distribution of the flow paths through which water flows in aquarium 10 as symmetrical as possible in direction A. In this regard, it is desirable to arrange water inlet 21a and drainage section 30 symmetrically in direction A with respect to the center in direction A, as shown in FIG.

[0031] [2. Details of the aquarium] Fig. 4 is a cross-sectional view of the above-mentioned water tank 10. Fig. 4 shows a cross-section of water tank 10 cut along a plane perpendicular to direction A. For convenience, Fig. 4 omits illustration of the above-mentioned water injection section 20 and drainage section 30. This method of illustration (method of showing the cross-section) is the same in the following Figs. 5 to 7.

[0032] The water tank 10 has a flat surface portion 11, a curved surface portion 12, and a side surface portion 13. The flat surface portion 11, the curved surface portion 12, and the side surface portion 13 are formed on the inner surface 10S of the wall portion 10W of the water tank 10. In this embodiment, since the water tank 10 is elongated in the A direction as described above, the flat surface portion 11, the curved surface portion 12, and the side surface portion 13 are also elongated in the A direction.

[0033] The flat surface portion 11 is located at the bottom of the inner surface 10S of the water tank 10, spreading out in the C direction. A pair of curved surface portions 12 are provided on both sides of the flat surface portion 11 in the C direction. More specifically, the curved surface portions 12 are connected to one end 11a and the other end 11b in the C direction of the flat surface portion 11, and bulge out in opposite directions in the C direction to extend upward.

[0034] In the following description, when distinguishing between the pair of curved surface portions 12, the curved surface portion 12 connected to one end portion 11a of the flat surface portion 11 in the C direction is referred to as the first curved surface portion 12a. The curved surface portion 12 connected to the other end portion 11b of the flat surface portion 11 in the C direction is referred to as the second curved surface portion 12b. The first curved surface portion 12a and the second curved surface portion 12b are each curved in a shape that protrudes from the inside to the outside of the water tank 10 in the cross section of FIG. 4. Therefore, the distance between the first curved surface portion 12a and the second curved surface portion 12b in the C direction increases from the side connected to the flat surface portion 11 toward the opposite side (upward).

[0035] The curved surface portion 12 (first curved surface portion 12a, second curved surface portion 12b) is formed in an arc shape with a constant radius of curvature R (distance from the center of curvature O) in the cross section of Fig. 4. Note that the curved surface portion 12 may be formed in a curved shape other than an arc shape (for example, a shape in which the radius of curvature R changes midway).

[0036] The side surface portion 13 is connected to each of the pair of curved surface portions 12 and extends upward. Therefore, a pair of side surface portions 13 is provided corresponding to each of the pair of curved surface portions 12. Here, of the pair of side surface portions 13, the side surface portion 13 connected to the first curved surface portion 12a is also referred to as the first side surface portion 13a, and the side surface portion 13 connected to the second curved surface portion 12b is also referred to as the second side surface portion 13b. In this case, it can be said that the first side surface portion 13a is connected to the first curved surface portion 12a and extends upward. Similarly, it can be said that the second side surface portion 13b is connected to the second curved surface portion 12b and extends upward. In this embodiment, the first side surface portion 13a and the second side surface portion 13b are located in parallel. That is, the distance between the first side surface portion 13a and the second side surface portion 13b in the C direction is constant.

[0037] As shown in Fig. 4, the distance in direction C between the upper ends of the pair of side portions 13, i.e., the first side portion 13a and the second side portion 13b, is defined as W (mm). The height from the flat portion 11 to the upper end of each of the pair of side portions 13 is defined as H (mm). In this case, the water tank 10 of this embodiment satisfies the following conditional formula (1). Note that the above W can be rephrased as the width of the water tank 10. Also, the above H can be rephrased as the height of the water tank 10. 1.12≦W / H≦1.90 (1)

[0038] For example, when the width of the flat surface portion 11 in the C direction shown in Fig. 4 is P (mm) and P = 100 mm, and the radius of curvature of the first curved surface portion 12a and the second curved surface portion 12b is R and R = 230 mm, and water tank 10 is designed with W = 460 mm and H = 370 mm, then W / H = 1.24. Therefore, with the above design, it is possible to realize water tank 10 that satisfies conditional formula (1).

[0039] Fig. 5 is a cross-sectional view showing another configuration of aquarium 10. Aquarium 10 in Fig. 5 has a configuration in which P and W of aquarium 10 in Fig. 4 are changed to P = 200 mm and W = 560 mm (R and H are the same as in Fig. 4, and the center of curvature of R is O or O'). In aquarium 10 in Fig. 5, W / H = 1.51. Therefore, aquarium 10 that satisfies conditional formula (1) can be realized by the design in Fig. 5 as well.

[0040] Fig. 6 is a cross-sectional view showing yet another configuration of aquarium 10. Aquarium 10 in Fig. 6 has a configuration in which P and W of aquarium 10 in Fig. 4 are changed to P = 300 mm and W = 660 mm (R and H are the same as in Fig. 4). In aquarium 10 in Fig. 6, W / H = 1.78. Therefore, aquarium 10 that satisfies conditional formula (1) can be realized by the design in Fig. 6 as well.

[0041] In the configuration of the aquarium 10 shown in Figs. 4 to 6, that is, in the configuration of the aquarium 10 in which a pair of curved surface portions 12 (first curved surface portion 12a, second curved surface portion 12b) are connected to both ends of the flat surface portion 11 in the C direction, and each side surface portion 13 (first side surface portion 13a, second side surface portion 13b) is further connected to each curved surface portion 12 and extends upward, the flat surface portion 11 is located on the bottom surface of the aquarium 10. In this case, when feeding the larvae in the aquarium 10, the food can be placed on the flat surface portion 11 to expand the feeding area in the C direction. Therefore, unlike, for example, a conventional aquarium without the flat surface portion 11 (aquarium with a simple concave cross section), the food is not concentrated in a narrow area at the bottom of the bottom surface. As a result, by simply expanding the aquarium 10 slightly in the C direction (without expanding the aquarium 10 more than necessary), many larvae can be efficiently fed, and the number of larvae reared (production efficiency) can be increased.

[0042] In addition, since the value of W / H is within the range satisfying the conditional formula (1), a water flow with an appropriate flow rate can be generated in the aquarium 10. For example, after feeding, water is poured downward from near one side surface portion 13 (for example, the first side surface portion 13a) at a predetermined flow rate, so that a water flow is generated along one curved surface portion 12 (for example, the first curved surface portion 12a) and the flat surface portion 11, and a water flow flowing toward the other curved surface portion 12 (for example, the second curved surface portion 12b) and the other side surface portion 13 (for example, the second side surface portion 13b) can be generated at an appropriate flow rate. As a result, the larvae that remain near the flat surface portion 11 after feeding can be driven away to the other side surface portion 13 (for example, the second side surface portion 13b) side, and can swim appropriately in the aquarium 10. Therefore, the phenomenon in which the larvae rub their heads against the bottom surface (for example, the flat surface portion 11) of the aquarium 10 after feeding, causing jaw dislocation, can be reduced.

[0043] Furthermore, if the flow rate is too fast, abnormalities (deformities) such as broken spines in larval fish are likely to occur. By keeping the W / H value within the range that satisfies conditional formula (1), it is possible to generate an appropriate flow rate in the aquarium 10 when pouring water, thereby reducing the occurrence of such abnormalities.

[0044] In other words, by providing the flat surface 11 on the bottom surface of the aquarium 10 and appropriately setting the cross-sectional shape of the aquarium 10 (the range of the value of W / H) according to conditional formula (1), it is possible to increase the number of larvae raised while reducing the occurrence of abnormalities (dislocation, deformity, etc.) in the larvae.

[0045] From the viewpoint of reliably realizing a flow rate capable of reducing the occurrence of jaw dislocation and deformities in larvae when pouring water into the aquarium 10 after feeding, it is desirable for the aquarium 10 of this embodiment to further satisfy the following conditional formula (1a): The aquarium 10 shown in Figures 4 to 6 further satisfies conditional formula (1a) and is a desirable form. 1.24≦W / H≦1.78 (1a)

[0046] Furthermore, from the standpoint of reliably realizing an aquarium 10 that satisfies conditional formula (1a), it is desirable for aquarium 10 of this embodiment to satisfy the following conditional formula (2a). Aquarium 10 shown in Figures 4 to 6 further satisfies conditional formula (2a) and is a desirable embodiment. 100 mm≦P≦300 mm (2a)

[0047] Incidentally, in the above-mentioned Patent Document 1, since the width of the tank is 800 mm and the height is 800 mm, it can be considered that W / H=800 / 800=1. Also, since there is no flat surface on the bottom surface of the tank, it can be considered that P=0 mm. In this configuration, as described above, the food supplied to the tank is concentrated at the lower end of the bottom surface of the tank, which results in a narrow feeding area, making it difficult to increase the number of larvae. When the length of the tank in the longitudinal direction is constant, it can be said that it is good to set P>0 mm and provide a flat surface (even if it is only a small width) on the bottom surface of the tank from the viewpoint of increasing the number of larvae. In this respect, the lower limit of W / H can be considered to be the median between the conventional W / H value "1" and the lower limit "1.24" of conditional formula (1a), that is, "1.12", as the critical point at which at least the effect of this embodiment can be obtained.

[0048] FIG. 7 is a cross-sectional view showing the structure of the aquarium 10A. The aquarium 10A in FIG. 7 has a structure in which P and W of the aquarium 10 in FIG. 4 are changed to P=400 mm and W=760 mm (R and H are the same as in FIG. 4). In the aquarium 10 in FIG. 7, W / H=2.05. In this design, the value of P indicating the width of the flat portion 11 of the aquarium 10 is large, and it is more effective in expanding the feeding area than the structures in FIG. 4 to FIG. 6. However, in the structure in FIG. 7, the width of the flat portion 11 becomes too wide, and it is known from the results of a simulation described later that it is difficult to achieve a water flow velocity (e.g., 0.045 m / s) that can drive away larvae that remain near the flat portion 11 after feeding at a certain water injection speed. For this reason, the upper limit of W / H can be considered to be the midpoint between the upper limit of "1.78" in conditional formula (1a) and the W / H value of "2.05" in the configuration of FIG. 7, i.e., "1.90", as the critical point at which at least the effects of this embodiment can be obtained.

[0049] The above-mentioned conditional formula (1) prescribes the range (upper limit, lower limit) of W / H based on this idea.

[0050] Similarly, from the viewpoint of expanding the feeding area within the aquarium 10 as much as possible, the lower limit of P can be considered to be the median between the conventional P value of "0 mm" and the lower limit of "100 mm" of conditional formula (2a), i.e., "50 mm", as the critical point at which at least the effect of this embodiment can be obtained.

[0051] Furthermore, from the viewpoint of realizing a water flow velocity capable of driving away larvae that remain near the planar portion 11 after feeding, the upper limit of P can be considered to be the median between the upper limit of conditional formula (2a) of "300 mm" and the value of P in the configuration of Figure 7, "400 mm," i.e., "350 mm," as the critical point at which at least the effect of this embodiment can be obtained.

[0052] From the above, in order to reliably realize an aquarium 10 that satisfies conditional formula (1), it can be said that it is desirable for aquarium 10 of the present embodiment to satisfy the following conditional formula (2). 50mm≦P≦350mm (2)

[0053] In addition, the aquarium 10 of this embodiment is elongated in the A direction as shown in FIG. 1. In other words, the aquarium 10 is elongated in the A direction perpendicular to a cross section defined by including the normal direction (B direction) and the lateral direction (C direction) of the planar portion 11. In this case, the number of larvae raised (absolute number) can be easily increased according to the length of the aquarium 10 in the A direction. For example, by increasing the length of the aquarium 10 in the A direction by n times (n is a positive number greater than 1), the number of larvae raised can also be simply increased by n times. In other words, from the viewpoint of increasing the number of larvae raised, it is desirable for the aquarium 10 to be elongated in the A direction as in this embodiment.

[0054] In addition, it was found from the following consideration that there is no adverse effect on the growth of larvae even if the aquarium 10 is extended to any length in the A direction. FIG. 8 is a graph showing the growth rate of larvae by day age (distribution of total length of larvae) in half-pipe aquariums (three types of capacity: 20 L, 30 L, and 100 L). Here, the half-pipe aquarium is a tank in which a cylinder is placed sideways, cut horizontally on a plane including the central axis, and both ends are extended upward. In the half-pipe aquarium with a capacity of 20 L, the width of the opening is 247 mm, and the length in the A direction is 497 mm. In the half-pipe aquarium with a capacity of 30 L, the width of the opening is 228 mm, and the length in the A direction is 752 mm. In the half-pipe aquarium with a capacity of 100 L, the width of the opening is 230 mm, and the length in the A direction is 2491 mm. That is, in each half-pipe aquarium, the width of the opening is approximately constant, and the length in the A direction is different from each other.

[0055] As described above, the aquarium 10 of this embodiment has a flat surface 11. However, in the considerations shown in FIG. 8, since we only wanted to examine the effect of the length of the aquarium in direction A on the growth rate of the larvae, that is, to eliminate the effect of the flat surface 11, we considered an aquarium that does not have a flat surface on the bottom as the above-mentioned half-pipe aquarium.

[0056] From the figure, it can be seen that the maximum overall length of the larvae increases from 20 days to 40 days of age regardless of whether the half-pipe tank used is 20 L, 30 L, or 100 L. Therefore, it can be said that it is possible to enlarge the aquarium 10 by extending it in the A direction without adversely affecting the growth of the larvae.

[0057] The above-mentioned curved surface portion 12 (first curved surface portion 12a, second curved surface portion 12b) of the water tank 10 is formed in an arc shape in the cross section of FIG. 4 and the like. As described above, the curved surface portion 12 may have a shape that protrudes from the inside to the outside of the water tank 10, and is not limited to the above-mentioned arc shape. However, if the curved surface portion 12 is arc-shaped, the direction of the water flow can be smoothly changed over the entire curved surface portion 12 when water is poured along the inner surface 10S of the water tank 10. This can reduce loss due to a decrease in the flow rate of the water flow. Therefore, it is desirable that the curved surface portion 12 be arc-shaped in that it is easy to achieve a desired flow rate at each position on the inner surface 10S of the water tank 10.

[0058] 4 to 6 exceeds 500 mm, the swimming ability of the larvae is such that it becomes difficult for the larvae to reach from near the water surface in the aquarium 10 to the flat portion 11 (to the food placed on the flat portion 11), making it difficult to properly raise the larvae. For example, the amount of food taken by the larvae decreases, which tends to cause a delay in the growth of the larvae, and ultimately leads to a decrease in the survival rate of the larvae.

[0059] 9 is a graph showing the growth rate of larvae by day (distribution of total length of larvae) in Kreisel tanks (three types of capacity: 20 L, 60 L, and 100 L). The Kreisel tank is a tank in which a cylinder is placed horizontally and cut along a plane parallel to the central axis, and the width of the opening at the cut surface is shorter than the inner diameter of the cylinder, and the wall extends halfway around the circumference.

[0060] For each Kreisel tank, the inner diameter and height of the 20 L tank are both 410 mm. The inner diameter and height of the 60 L tank are both 533 mm. The inner diameter and height of the 100 L tank are both 671 mm.

[0061] As described above, the aquarium 10 of this embodiment has a flat surface 11. However, in the verification shown in FIG. 9, in order to examine only the effect of the inner diameter (= height) of the aquarium on the growth rate of the larvae, that is, to eliminate the effect of the flat surface 11, an aquarium without a flat surface on the bottom was considered as the Kreisel aquarium.

[0062] 9, it can be seen that in the 60 L and 100 L aquariums with heights exceeding 500 mm, the range of total length of the larvae is narrower and the growth rate of the larvae is lower at both 20 and 40 days of age than in the 20 L aquarium with a height of 500 mm or less. Therefore, from the viewpoint of making it easier for the larvae to reach the food on the bottom during feeding and enabling the larvae to be properly raised, it can be said that it is desirable for the height H of the aquarium to be 500 mm or less. In other words, it is desirable for the aquarium 10 of this embodiment to satisfy the following conditional formula (3). H≦500mm (3)

[0063] In particular, from the viewpoint of ensuring that the larvae can easily reach the food on the bottom during feeding and ensure that the larvae are properly raised, it can be seen from Figure 8 that it is desirable for the height H of the aquarium to be 410 mm or less. In other words, it is desirable for the aquarium 10 of this embodiment to further satisfy the following conditional formula (3a). H≦410mm (3a)

[0064] 3. Examples Next, examples of the water tank 10 of this embodiment will be described together with comparative examples. In the following, the water flow distribution in each of the three water tanks 10 shown in Fig. 4 to Fig. 6 and the water tank 10A shown in Fig. 7 (particularly the distribution in the cross section perpendicular to the A direction) was specifically verified by simulation.

[0065] First, as shown in Fig. 4, the width of the flat surface portion 11 in the C direction is P (mm), and the aquarium 10 with P = 100 mm, W = 460 mm, and H = 370 mm was designed as the aquarium of Example 1. When the radius of curvature of the curved surface portion 12 of the aquarium 10 is R, R = 230 mm. The length of the aquarium 10 in the A direction is 1500 mm. The height H (= 370 mm) of the aquarium was set in consideration of the height (500 mm or less) that allows the larvae to swim downward and ingest food during feeding.

[0066] As shown in FIG. 5, P and W of water tank 10 in Example 1 were changed to P=200 mm and W=560 mm, and the other parameters (H, R and L) were kept in common with Example 1 to design water tank 10 in Example 2.

[0067] As shown in FIG. 6, P and W of water tank 10 in Example 1 were changed to P=300 mm and W=660 mm, and the other parameters (H, R, and L) were kept in common with Example 1 to design water tank 10 in Example 3.

[0068] As shown in FIG. 7, P and W of water tank 10 in Example 1 were changed to P=400 mm and W=760 mm, and the other parameters (H, R and L) were kept in common with Example 1 to design water tank 10A in Comparative Example 1.

[0069] As shown in FIG. 2, the water injection pipe of the water injection section 20 that injects water into each water tank (water tank 10 and 10A) in Examples 1 to 3 and Comparative Example 1 was assumed to have nine water injection ports 21a formed at 70 mm intervals on one side and the other side in the A direction from the center in the A direction (the number of water injection ports 21a is 18 in total). The diameter of the water injection ports 21a was set to 3.5 mm. The distance D shown in FIG. 3 when a predetermined amount of water is stored in the water tank by injecting water from each water injection port 21a of the water injection pipe 21 was set to D=78 mm. The distance D refers to the distance in the B direction from the top end of the side surface portion 13 of the water tank to the initial water surface position S0 in the water tank (the water surface position when a predetermined amount of water is stored in the water tank 10). When the distance from the bottom surface (flat portion 11) of water tank 10 to position S0 is defined as height H0 of drainage portion 30 (see FIG. 10), H0=H-D0=370-78=292 mm.

[0070] It was assumed that water was injected into the water tank by positioning water injection pipe 21 near one side of the tank at a position lower than position S0, supplying water to connecting pipe 22 at a rate of 10 L / min, and discharging seawater downward from each water injection port 21a. Here, one side portion, one curved portion, flat portion, other curved portion, and other side portion refer to first side portion 13a, first curved portion 12a, flat portion 11, second curved portion 12b, and second side portion 13b shown in Figures 4 to 7. It was assumed that drainage portions 30 were disposed near water injection pipe 21 and at positions symmetrical to each other with respect to the center of water injection pipe 21 in direction A.

[0071] In each of Examples 1 to 3 and Comparative Example 1, the distribution of water flow (flow velocity, flow rate) was analyzed by multiphase flow analysis using the VOF (Volume of Fluid) method. The VOF method is a type of analysis method for free surface flow among multiphase flow analyses of gas and liquid. FIG. 10 shows a schematic diagram of the water flow distribution in each water tank in Examples 1 to 3 and Comparative Example 1 for 40 seconds from the start of water pouring. Note that FIG. 10 shows the water flow distribution in a cross section perpendicular to the longitudinal direction in each water tank. In FIG. 10, the dashed line indicates the water flow, and the solid line indicates the overall water flow.

[0072] As a result of the analysis, the following was found: First, in Examples 1 to 3, water flows along the inner surface of the water tank (one side surface, one curved surface, flat surface, the other curved surface, the other side surface), and a good water flow field is formed in the water tank.

[0073] Here, it has been found that if the bottom flow velocity (the flow velocity of the water flow near the flat surface) falls below 0.045 m / s, it becomes difficult to drive away the larvae from near the bottom by the water flow, and the larvae tend to rub their heads against the bottom, increasing the incidence of jaw dislocation. In this regard, in Examples 1 to 3, as a result of analysis, a bottom flow velocity of 0.045 m / s to 0.05 m / s is ensured, which is considered to reduce the occurrence of jaw dislocation in the larvae. In addition, after feeding, the larvae swim in the tank on a gentle water current flowing at 0.05 m / s or less, which is considered to reduce the occurrence of deformities such as broken spines in the larvae.

[0074] The above-mentioned bottom flow velocity condition for reducing jaw dislocation of larvae must be considered for the entire flat surface, that is, from one end side (the side connected to one curved surface) to the other end side (the side connected to the other curved surface). However, if a flow velocity of 0.045 m / s or more is satisfied at the downstream end of the flat surface, where the flow velocity is relatively slower than at the upstream end of the flat surface, then the flow velocity of 0.045 m / s or more will be satisfied over the entire flat surface. Therefore, in the example of Figure 10, it is sufficient to satisfy a bottom flow velocity of 0.045 m / s or more at least at the other end side (downstream end) of the flat surface.

[0075] In contrast, in Comparative Example 1, the bottom flow velocity (particularly the flow velocity at the downstream end of the flat portion) was 0.04 m / s, which was lower than the standard of 0.045 m / s. This is thought to be because, in Comparative Example 1, the bottom width of the aquarium was too wide, so that the water that flowed along one side portion did not pass near the bottom portion and reach the other side portion, in other words, the water flowed away from the bottom and the other side portion. In Comparative Example 1, the bottom flow velocity was slow, so that the larvae remained near the bottom even after feeding, and there was a concern that the larvae would be more likely to lose their jaws.

[0076] Furthermore, as mentioned above, if the water flow is too fast, the larvae are more likely to suffer from deformities such as broken spines. In order to form an appropriate water flow in the aquarium, the upper limit of the flow speed of the water flowing along the curved surface upstream of the flat surface is preferably 0.1 m / s or less, and more preferably 0.08 m / s or less.

[0077] The water tanks of Examples 1 to 3 satisfy the respective conditional expressions of this embodiment described above, and are fully expected to provide the effects of this embodiment described above.

[0078] 11 and 12 show schematic diagrams of the water flow distribution in the longitudinal direction (direction A) in each of the water tanks in Examples 1 to 3 and Comparative Example 1. It was found that the water flow distribution in the longitudinal direction was nearly symmetrical with respect to the center of direction A in each of the water tanks.

[0079] [4. Other] In the above embodiment, the height H0 of the drainage section 30 is set to 292 mm for the water tank 10 with H=370 mm. However, the height H0 of the drainage section 30 may be equal to or less than the height H of the water tank 10. In this embodiment, as shown in the above conditional expressions (3) and (3a), H≦500 mm, preferably H≦410 mm, and therefore it can be concluded that the height H0 of the drainage section 30 is also H≦500 mm, preferably H≦410 mm. In this case, the lateral width W of the water tank 10 according to the present invention can be rephrased as the lateral width W of the water surface when a predetermined amount of water is stored in the water tank 10. The height H of the water tank 10 can also be rephrased as the height H from the flat surface 11 to the water surface.

[0080] Moreover, the height H of the aquarium 10 is a parameter that determines the volume of the aquarium 10 (the maximum amount of water that can be stored). On the other hand, if the drainage section 30 is installed below the height H of the aquarium 10, the height H0 of the drainage section 30 also becomes a parameter that determines the maximum amount of water that can be stored in the aquarium 10. In this way, the height H of the aquarium 10 and the height H0 of the drainage section 30 are common in that they are both parameters that determine the maximum amount of water that can be stored in the aquarium 10. Therefore, the above conditional expressions (1) and (1a) can be replaced by the following conditional expressions (A) and (B), respectively. That is, assuming that the height of the drainage section 30 from the flat surface section 11 of the aquarium 10 is H0 (mm), 1.12≦W / H0≦1.90 (A) 1.24≦W / H0≦1.78 (B) It is.

[0081] The water tank 10 of this embodiment satisfies the above-mentioned conditional formula (2), that is, 50mm≦P≦350mm. Here, in the water tank 10 of Example 1, if the width P of the flat portion 11 is changed from 100mm to 50mm, the width W of the water tank 10 decreases by 50mm from 460mm to 410mm. In addition, in the water tank 10 of Example 3, if the width P of the flat portion 11 is changed from 300mm to 350mm, the width W of the water tank 10 increases by 50mm from 660mm to 710mm. Therefore, the possible range of W of the water tank 10 is 410mm≦W≦710mm. Therefore, in terms of the ratio W / P, it can be said that the water tank 10 of this embodiment satisfies the following conditional formula (4). 2.03≦W / P≦8.20 (4)

[0082] Among them, it can be said that a desirable range of W / P is a range that satisfies the following conditional formula (4a) based on the values ​​shown in Examples 1 to 3. 2.20≦W / P≦4.60 (4a)

[0083] In the water tank 10 shown in Fig. 4 etc., the first side portion 13a and the second side portion 13b are preferably positioned parallel to each other as in this embodiment, but they do not have to be positioned parallel to each other. For example, the distance between the first side portion 13a and the second side portion 13b in the C direction may increase slightly toward the top. In this case, the distance W in the C direction is the maximum distance between the first side portion 13a and the second side portion 13b (the distance between the upper ends).

[0084] [5. Notes] The aquarium and breeding device described in this embodiment can be expressed as follows.

[0085] The tank in Appendix (1) is An aquarium for raising larvae, A planar portion extending laterally; a pair of curved surface portions connected to one end and the other end of the planar portion in the lateral direction and extending upward while bulging out in opposite directions in the lateral direction; a pair of side surfaces connected to the pair of curved surfaces and extending upward, The distance between the upper ends of the pair of side portions in the lateral direction is W (mm), When the height from the flat portion to each of the upper ends of the pair of side portions is H (mm), 1.12≦W / H≦1.90 (1) Satisfy.

[0086] The tank of appendix (2) is the tank of appendix (1), 1.24≦W / H≦1.78 (1a) More satisfying.

[0087] The aquarium of appendix (3) is the aquarium of appendix (1), When the width of the planar portion in the lateral direction is P (mm), 50mm≦P≦350mm (2) Satisfy.

[0088] The aquarium of appendix (4) is the aquarium of appendix (2), When the width of the planar portion in the lateral direction is P (mm), 100 mm≦P≦300 mm (2a) Satisfy.

[0089] The aquarium of appendix (5) is an aquarium according to any one of appendix (1) to (4), H≦500mm (3) Satisfy.

[0090] The tank of appendix (6) is the tank of appendix (5), H≦410mm (3a) More satisfying.

[0091] The aquarium of appendix (7) is an aquarium according to any one of appendix (1) to (6), It is elongated in a direction perpendicular to a cross section defined by including a normal direction of the planar portion and the lateral direction.

[0092] The aquarium of appendix (8) is an aquarium according to any one of appendix (1) to (7), The curved surface portion is arc-shaped.

[0093] The larval fish breeding device in Appendix (9) is An aquarium according to any one of appendices (1) to (8); A water injection unit that injects water into the water tank; and a drainage section that drains water that is poured into the water tank and that exceeds a predetermined capacity of the water tank.

[0094] The larval fish breeding apparatus according to claim 10 is the larval fish breeding apparatus according to claim 9, When the height of the drainage portion from the flat portion is H0 (mm), Instead of the above formula (1), 1.12≦W / H0≦1.90 (A) Satisfy.

[0095] The larval fish breeding apparatus of the appendix (10) can be rephrased as follows. That is, the larval fish breeding apparatus described in appendix (10) is Aquarium and A water injection unit that injects water into the water tank; a drainage section that drains water that is poured into the water tank and that exceeds a predetermined capacity of the water tank; The water tank is A planar portion extending laterally; a pair of curved surface portions connected to one end and the other end of the planar portion in the lateral direction and extending upward while bulging out in opposite directions in the lateral direction; a pair of side surfaces connected to the pair of curved surfaces and extending upward, The distance between the upper ends of the pair of side portions in the lateral direction is W (mm), When the height of the drainage portion from the flat portion is H0 (mm), 1.12≦W / H0≦1.90 (A) Satisfy.

[0096] The larval fish rearing device of appendix (10) preferably comprises: 1.24≦W / H0≦1.78 (B) Satisfy.

[0097] The larval fish breeding device of Appendix (11) is A water tank according to appendix (7), A water injection unit that injects water into the water tank; a drainage section that drains water that is poured into the water tank and that exceeds a predetermined capacity of the water tank; The water injection unit has a water injection pipe extending in a longitudinal direction of the water tank, The water injection pipe has a plurality of water injection ports formed side by side in the longitudinal direction, The drainage sections are arranged side by side in the longitudinal direction, the number of which is less than the number of the water inlets.

[0098] The larval fish breeding apparatus according to claim 12 is the breeding apparatus according to claim 11, The water inlet and the drainage section are disposed symmetrically in the longitudinal direction with respect to a central portion in the longitudinal direction.

[0099] Although the embodiment of the present invention has been described above, the scope of the present invention is not limited to this, and the invention can be expanded or modified without departing from the spirit of the invention. [Industrial Applicability]

[0100] The aquarium for raising larvae of the present invention can be used, for example, for raising eel larvae. [Explanation of symbols]

[0101] 10. Aquarium 11 Plane part 11a One end 11b Other end 12 Curved part 12a First curved surface portion (one of a pair of curved surface portions) 12b Second curved surface portion (the other of the pair of curved surface portions) 13 Side part 13a First side portion (one of a pair of side portions) 13b Second side portion (the other of the pair of side portions) 20 Water injection section 21 Water injection pipe 21a Water inlet 30 Drainage section 100 Rearing Equipment A Longitudinal direction B. Horizontal H Height of side part H0 Height of drainage section P width W Spacing

Claims

1. An aquarium for raising larvae, A planar portion extending laterally; a pair of curved surface portions connected to one end and the other end of the planar portion in the lateral direction and extending upward while bulging out in opposite directions in the lateral direction; a pair of side surfaces connected to the pair of curved surfaces and extending upward, The distance between the upper ends of the pair of side portions in the lateral direction is W (mm), When the height from the flat portion to each of the upper ends of the pair of side portions is H (mm), 1.12≦W / H≦1.90 (1) An aquarium that satisfies your needs.

2. 1.24≦W / H≦1.78 (1a) The aquarium of claim 1 further satisfying the above.

3. When the width of the planar portion in the lateral direction is P (mm), 50 mm≦P≦350 mm ... (2) 2. The aquarium according to claim 1, which satisfies the above.

4. When the width of the planar portion in the lateral direction is P (mm), 100mm≦P≦300mm...(2a) 3. The aquarium according to claim 2, which satisfies the following:

5. H≦500 mm ... (3) 2. The aquarium according to claim 1, which satisfies the above.

6. H≦410mm...(3a) The aquarium according to claim 5 , further satisfying the above.

7. The water tank according to claim 1 , which is elongated in a direction perpendicular to a cross section defined by including a normal direction of the planar portion and the lateral direction.

8. The aquarium according to claim 1 , wherein the curved surface portion is arc-shaped.

9. A water tank according to any one of claims 1 to 8, A water injection unit that injects water into the water tank; A drainage section that is poured into the aquarium and drains water that exceeds a specified capacity of the aquarium, thereby providing a larval fish breeding device.

10. The larval fish breeding apparatus according to claim 9, When the height of the drainage portion from the flat portion is H0 (mm), Instead of the formula (1), 1.12≦W / H0≦1.90...(A) A device for raising larval fish that satisfies the above requirements.

11. The water tank according to claim 7 , A water injection unit that injects water into the water tank; a drainage section that drains water that is poured into the water tank and that exceeds a predetermined capacity of the water tank; The water injection unit has a water injection pipe extending in a longitudinal direction of the water tank, The water injection pipe has a plurality of water injection ports formed side by side in the longitudinal direction, The drainage sections are arranged in a line in the longitudinal direction and the number of the drainage sections is less than the number of the water inlets.

12. The larvae rearing device according to claim 11 , wherein the water inlet and the water outlet are arranged symmetrically in the longitudinal direction with respect to a central portion in the longitudinal direction.

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