Method and apparatus for rearing fry

Abstract

To improve a ratio of smolts that can be shipped with respect to bred juvenile fishes as much as possible.SOLUTION: The breeding method of a juvenile fish includes the steps of: suppressing a process of causing catadromous juvenile fishes to become smolts from proceeding by shieling light for a water tank where the juvenile fishes are bred, the process causing the juvenile fishes to express seawater adaptability; and promoting the process of causing catadromous juvenile fishes to become smolts, by irradiating the water tank with the light according to a shipping timing of the smolts grown up from the juvenile fishes.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for rearing fry.

Background Art

[0002] In the cultivation of catadromous fish exemplified by the cherry salmon, seawater acclimation is performed on smolts, which are fry that have acquired the ability to adapt to seawater, and then they are shipped. Also, the acquisition of the ability of fry to adapt to seawater is also referred to as "smoltification" (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Cherry salmon fry often smoltify in the spring in a natural state. On the other hand, the demand for cherry salmon smolts often increases in the autumn. Conventionally, it has been difficult to control the timing of smoltification of fry. Therefore, many of the fry that smoltify in the spring are reared in fresh water until autumn shipment and then shipped in the autumn. However, there are cases where fry lose their ability to adapt to seawater while being reared in fresh water, and the ratio of marketable smolts to the reared fry has been decreasing.

[0005] One aspect of the disclosed technology aims to provide a method and an apparatus for rearing fry that can increase the ratio of marketable smolts to the reared fry as much as possible.

Means for Solving the Problems

[0006] One aspect of the disclosed technology is illustrated by a method for rearing fry as follows. The method for rearing fry includes a step of suppressing smoltification, which causes the fry of anadromous fish to develop seawater adaptability, by shading the aquarium in which the fry are reared, and a step of promoting the smoltification of the fry by irradiating the aquarium with light in accordance with the shipping time of the smoltified fry.

[0007] According to the rearing method, smoltification of the fry can be suppressed by shading the aquarium in which the fry are reared. And smoltification of the fry can be promoted by irradiating the aquarium with light in accordance with the shipping time of the fry. That is, according to the rearing method, smoltification of the fry can be adjusted according to the shipping time of the fry, so that the period of rearing the smoltified fry in fresh water can be shortened. Therefore, it is possible to prevent the smoltified fry from losing their seawater adaptability once they have smoltified, and thus to increase the ratio of marketable smolts among the reared fry as much as possible.

[0008] Here, the step of promoting smoltification may be such that the aquarium is irradiated with light for a predetermined period within a day, and the irradiation of light to the aquarium is stopped for the period other than the predetermined period within the day. And in the step of promoting smoltification, the predetermined period may be between 14 hours and 16 hours. By setting the predetermined period in this way, it is possible to irradiate the aquarium with light assuming the irradiation time of sunlight in midsummer.

[0009] Also, in the step of promoting smoltification, the illuminance of the light irradiated to the aquarium may be 2000 lux or more. By setting the illuminance of the light in this way, it is possible to irradiate the fry to be reared with light of sufficient intensity.

[0010] Also, the step of promoting smoltification may be continuously performed for one month or more. By continuously performing the step of promoting smoltification for one month or more, it is possible to sufficiently secure a period for smoltifying as many fry as possible.

[0011] The disclosed technology can also be grasped from the side of the fry rearing device.

Advantages of the Invention

[0012] According to the disclosed technology, the ratio of smolts that can be shipped with respect to the reared fry can be increased as much as possible.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0014] <Embodiment> The configuration of the following embodiment is an example, and the disclosed technology is not limited to the configuration of the embodiment. FIG. 1 is a diagram showing an example of the rearing device 1 according to the embodiment. The rearing device 1 includes a water tank 10, a fresh water tank 20, a black curtain 31, a surface light source 32, and a control device 60.

[0015] The water tank 10 is a water tank for rearing fry 100 of cherry salmon. Fresh water is stored in the water tank 10. As the fresh water, for example, well water is adopted. The temperature of the fresh water stored in the water tank 10 is, for example, about 16 to 20 degrees Celsius, preferably about 16 degrees Celsius.

[0016] The fry 100 are in a state before expressing the seawater adaptability suitable for seaward migration. The fry 100 may be either yearling fish or one-year-old fish. The number of fry 100 reared in the water tank 10 is appropriately determined according to the size (water storage capacity) of the water tank 10. For example, when the water storage capacity of the water tank 10 is 1 ton, 200 fry 100 can be reared.

[0017] The light-shielding curtain 31 is a curtain having light-shielding properties. The light-shielding curtain 31 is arranged, for example, so as to cover the water tank 10 and the surface light source 32. That is, the light-shielding curtain 31 suppresses the incidence of external light on the water tank 10. In other words, the light-shielding curtain 31 shields the water tank 10 from light. The light-shielding curtain 31 is an example of a "suppression means".

[0018] The surface light source 32 is a surface light source that illuminates the water surface of the water tank 10. The surface light source 32 is preferably a light source that evenly illuminates the entire water surface of the water tank 10. The surface light source 32 illuminates the entire water surface of the water tank 10 with an illuminance of, for example, 2000 lux or more. For example, the surface light source 32 may be formed by arranging a plurality of point light sources vertically and horizontally to form a surface light source. The surface light source 32 may be formed by reflecting light from a point light source with a mirror surface or the like to form a surface light source. Examples of the light source of the surface light source 32 include an incandescent lamp, a fluorescent lamp, a Light Emitting Diode (LED), and the like. By arranging the light-shielding curtain 31 and the surface light source 32 in this way, the irradiation of light on the water tank 10 is controlled by turning on and off the surface light source 32 arranged inside the light-shielding curtain 31. The surface light source 32 is an example of a "light source".

[0019] Fresh water is stored in the fresh water tank 20. As the fresh water stored in the fresh water tank 20, for example, well water can be adopted. A fresh water pipe 23 is connected to the fresh water tank 20. One end of the fresh water pipe 23 is connected to the fresh water tank 20, and the other end is connected to the shower pipe 41. A valve 21 and a flow meter 22 are provided in the fresh water pipe 23 in order from the fresh water tank 20 side. The fresh water tank 20 is equipped with a pump (not shown), and the flow rate of fresh water from the fresh water tank 20 to the fresh water pipe 23 is adjusted according to the opening degree of the valve 21. Also, by closing the valve 21, the inflow of fresh water from the fresh water tank 20 to the fresh water pipe 23 is stopped. Then, the flow rate of fresh water flowing through the fresh water pipe 23 is measured by the flow meter 22.

[0020] The shower pipe 41 is provided above the water tank 10. When viewed from above the water tank 10, the shower pipe 41 is provided so as to cross the water tank 10. A plurality of through holes 411 are provided in the shower pipe 41. Fresh water flowing in the shower pipe 41 is supplied to the water tank 10 so as to blow out from the through holes 411.

[0021] The water tank 10 is provided with a drain pipe 51 that drains water when the stored fresh water exceeds a specified amount. The drain pipe 51 is bent in the middle, and the bending high part 511, which is the highest part in the bent part, is provided at the same height as the water surface height H in the water tank 10 when, for example, a specified amount of water is stored. With such a configuration, even if fresh water in excess of the specified amount is stored in the water tank 10 by the supply of fresh water from the shower pipe 41, the drain pipe 51 can drain fresh water in excess of the specified amount from the water tank 10.

[0022] Each of the above-described valve 21, flow meter 22, and surface light source 32 is connected to the control device 60 by signal lines 61, 62, and 63. FIG. 2 is a diagram showing an example of the hardware configuration of the control device 60. The control device 60 is an information processing device including a Central Processing Unit (CPU) 601, a main storage unit 602, an auxiliary storage unit 603, and a communication unit 604. The CPU 601, the main storage unit 602, the auxiliary storage unit 603, and the communication unit 604 are interconnected by a connection bus. The control device 60 is an example of a "control unit".

[0023] The CPU 601 is also called a microprocessor unit (MPU) or a processor. At least a part of the processes executed by the CPU 601 may be executed by an integrated circuit (IC) or other digital circuits. The CPU 101 may be a combination of a processor and an integrated circuit. The combination is called, for example, a microcontroller unit (MCU), a System-on-a-chip (SoC), a system LSI, a chip set, or the like. In the control device 60, the CPU 601 expands the program stored in the auxiliary storage unit 603 into the work area of the main storage unit 602 and controls peripheral devices through the execution of the program.

[0024] The main memory unit 602 is exemplified as a memory unit directly accessible from the CPU 601. The main memory unit 602 includes a Random Access Memory (RAM) and a Read Only Memory (ROM).

[0025] The auxiliary storage unit 603 reads and writes various programs and various data onto a recording medium in a rewritable manner. The auxiliary storage unit 603 is also called an external storage device. The auxiliary storage unit 603 stores an operating system (OS), various programs, various tables, etc. The auxiliary storage unit 603 is, for example, an Erasable Programmable ROM (EPROM), a Solid State Drive (SSD), a Hard Disk Drive (HDD), or the like.

[0026] The communication unit 604 is, for example, an interface with signal lines 61, 62, 63. The communication unit 604 communicates with external devices such as the valve 21, the flow meter 22, and the surface light source 32 via the signal lines 61, 62, 63.

[0027] Here, the inventors of the breeding device 1 have found that it is possible to suppress the smoltification of the fry 100 by blocking light and breeding them in the dark, and that it is possible to promote the smoltification of the fry 100 by irradiating light on the fry 100 whose smoltification has been suppressed and breeding them for a predetermined smoltification promotion period (for example, about one month). Therefore, in the present embodiment, the fry 100 are bred in the dark to suppress smoltification until the shipment time of the smolts of the fry 100 approaches. Then, when the shipment time of the smolts of the fry 100 approaches, light is irradiated onto the water tank 10 to promote smoltification.

[0028] Here, in order to promote the smoltification of fry, it is preferable that a predetermined period of a day is set as the period during which the water tank 10 is irradiated with light (hereinafter also referred to as the "light period"), and the period excluding the above-mentioned predetermined period of a day is set as the period during which the water tank 10 is not irradiated with light (hereinafter also referred to as the "dark period"). For example, the light period can be, for example, 14 to 16 hours, and the dark period can be 8 to 10 hours.

[0029] A predetermined program is stored in advance in the auxiliary storage unit 603 of the control device 60. The CPU 601 controls the opening and closing of the valve 21 and the lighting and extinguishing of the surface light source 32 according to the program stored in the auxiliary storage unit 603. The control device 60 controls the valve 21 based on the flow rate indicated by the flow meter 22 so that, for example, half of the amount of fresh water stored in the water tank 10 is replaced in one hour, and executes the supply of fresh water to the water tank 10.

[0030] (Rearing method of fry using the rearing device 1) A method for rearing fry 100 of cherry salmon using the above-mentioned rearing device 1 will be described. FIG. 3 is a diagram showing an example of the flow of a method for rearing fry 100 using the rearing device 1 according to the embodiment. Hereinafter, with reference to FIG. 3, the flow of the method for rearing fry 100 using the rearing device 1 will be described.

[0031] In step S1, preparations for rearing fry 100 are made. That is, fresh water is stored in the water tank 10, and the fry 100 to be reared are released into the water tank 10. In this embodiment, it is assumed that 1 ton of fresh water is stored in the water tank 10 and 200 fry 100 are released into the water tank 10. Here, in this embodiment, in the water tank 10 storing 1 ton of fresh water, the height of the water surface is the water surface height H. The temperature of the fresh water stored in the water tank 10 is adjusted to about 16 degrees Celsius, for example. Also, the surface light source 32 is turned off.

[0032] In step S2, the smoltification of the juvenile fish 100 is suppressed until the shipment time of the smolts approaches. The juvenile fish 100 are reared while the surface light source 32 remains turned off. Since the incidence of light from the outside to the water tank 10 is suppressed by the light-shielding curtain 31, in the state of step S2, the juvenile fish 100 are reared in a dark state. By rearing the juvenile fish 100 in the dark, the smoltification of the juvenile fish 100 is suppressed. The process of step S2 is an example of the "step of suppressing smoltification".

[0033] In step S3, the control device 60 determines whether the period until shipment, which is stored in the auxiliary storage unit 603 in advance, is within one month. If the period until shipment is within one month (YES in step S3), the process proceeds to step S4. If the period until shipment is longer than one month (NO in step S3), the process returns to step S2.

[0034] In step S4, the smoltification of the juvenile fish 100 is promoted. The control device 60 turns on the surface light source 3 2. Here, the control device 60, for example, turns on the surface light source 32 for 16 hours a day and turns it off for 8 hours a day. That is, in step S4, the juvenile fish 100 are reared in a bright environment for 16 hours and in a dark environment for 8 hours a day. In the present embodiment, for example, by continuing the rearing according to the process of step S4 for one month or more, the smoltification of the juvenile fish 100 is promoted. The process of step S4 is an example of the "step of promoting smoltification".

[0035] In step S5, the control device 60 determines whether the rearing of the juvenile fish 100 according to step S4 has continued for one month. If it has continued for one month (YES in step S5), the process ends and the shipment preparation of the reared smolts is started. If it is less than one month (NO in step S5), the process proceeds to S4.

[0036] <Operational effects of the embodiment> In this embodiment, as described with reference to steps S2 and S3 in FIG. 3, the fry 100 are reared in the dark until the shipment time of the smoltified fry approaches. By being reared in the dark, the smoltification of the fry 100 is suppressed. Then, when the shipment time of the smoltified fry approaches, as described with reference to steps S4 and S5 in FIG. 3, the smoltification of the fry 100 is promoted. That is, according to this embodiment, the smoltification of the fry 100 can be controlled according to the shipment time. Therefore, since it is suppressed to rear the fry 100 that have smoltified earlier than the shipment time in fresh water, the ratio of smolts that can be shipped for the reared fry 100 can be increased as much as possible.

[0037] In this embodiment, for example, the light period is set to 16 hours and the dark period is set to 8 hours. By setting the light period and the dark period in this way, light irradiation assuming the sunlight irradiation time in midsummer can be performed on the water tank 10.

[0038] In this embodiment, the illuminance of the surface light source 32 that illuminates the water tank 10 is set to 2000 lux or more. By setting the illuminance of the surface light source 32 in this way, light of sufficient intensity can be irradiated on the fry 100 to be reared.

[0039] In this embodiment, the period for promoting the smoltification of the fry 100 exemplified by step S4 in FIG. 3 is ensured for 1 month or more. There are individual differences in the period until the fry 100 complete smoltification. In this embodiment, by ensuring a period of continuously promoting smoltification for 1 month or more, a sufficient period for smoltifying more fry 100 can be ensured.

[0040] In addition, in this embodiment, in the water tank 10, the water exceeding the water surface height H is drained from the drain pipe 51. That is, the water tank 10 is subjected to a pouring flow of fresh water supplied from the shower pipe 41. By adopting such a pouring flow method, the water tank 10 according to this embodiment can omit the purification treatment such as filtration of the water in the water tank 10. That is, since it is not necessary to provide a filtration device in the water tank 10, the configuration of the water tank 10 can be made simple. Note that the water tank 10 may be of a method other than the pouring flow method such as a circulation type as long as the water quality and water temperature can be maintained.

[0041] (Modification example) In the embodiment described above, the light shielding of the water tank 10 was suppressed by the light-shielding curtain 31. However, the light shielding of the water tank 10 may be suppressed by a method other than the light-shielding curtain 31. The light shielding of the water tank 10 may be performed, for example, by arranging the water tank 10 in a dark room.

[0042] In the embodiment described above, the breeding method for the juvenile masu salmon 100 was described. However, the water tank 10 can also be adopted for breeding juveniles of anadromous fish other than masu salmon. Examples of anadromous fish other than masu salmon include pink salmon, rainbow trout, etc. In addition, when breeding juveniles other than masu salmon, a period for promoting smoltification corresponding to the type of fish to be bred may be ensured, and the timing for starting the promotion of smoltification may be determined.

[0043] In the embodiment described above, the supply of fresh water from the shower pipe 41 to the water tank 10, the lighting and extinguishing of the surface light source 32 were controlled by the control device 60. However, the control device 60 may be omitted from the breeding device 1. For example, an operator or the like may open and close the valve 21 based on the flow rate indicated by the flow meter 22, or may turn on and off the surface light source 32.

[0044] Note that the method for raising juvenile cherry salmon 100 using the above-mentioned breeding device 1 can be implemented regardless of the season. Also, the light period and the dark period can be switched regardless of the actual day and night. For example, the light period may be implemented at night and the dark period may be implemented during the day. Further, the periods in steps S3 and S5 in FIG. 3 are not limited to one month and may be appropriately determined according to the period until the completion of smoltification of the juvenile fish 100 or the like.

[0045] The embodiments and modifications disclosed above can be combined with each other.

Explanation of Reference Numerals

[0046] 1... Breeding device 10... Aquarium 20... Freshwater tank 21... Valve 22... Flow meter 23... Freshwater pipe 31... Light-shielding curtain 32... Surface light source 41... Shower pipe 411... Through hole 51... Drain pipe 511... Bent high part 60... Control device 61... Signal line 62... Signal line 63... Signal line 100... Juvenile fish 601... CPU 602... Main memory unit 603... Auxiliary storage unit 604... Communication unit

Claims

1. Suppressing the smoltification that causes the juvenile fish of marine - migrating fish to develop seawater adaptability by shading the aquarium in which the juvenile fish are reared; Promoting the smoltification of the juvenile fish by irradiating light on the aquarium according to the shipping time of the smoltified juvenile fish, comprising: A method for rearing juvenile fish.

2. The step of promoting the smoltification: Irradiating light on the aquarium for a predetermined period within a day, and stopping the irradiation of light on the aquarium for the period other than the predetermined period within the day; The method for rearing juvenile fish according to Claim 1.

3. In the step of promoting the smoltification, the predetermined period is between 14 hours and 16 hours; The method for rearing juvenile fish according to Claim 2.

4. In the step of promoting the smoltification, the illuminance of the light irradiated on the aquarium is 2000 lux or more; The method for rearing juvenile fish according to Claim 1.

5. The step of promoting the smoltification is continuously carried out for one month or more; The method for rearing juvenile fish according to any one of Claims 1 to 4.

6. An aquarium in which fresh water is stored and juvenile fish of marine - migrating fish are reared; A light source for irradiating light on the aquarium; Suppressing means for covering the aquarium and the light source to suppress the incidence of light from the outside to the aquarium; A control unit for controlling the lighting and extinguishing of the light source, wherein: The control unit: Extinguishing the light source to suppress the smoltification that causes the juvenile fish to develop seawater adaptability; Promoting the smoltification of the juvenile fish by lighting the light source according to the shipping time of the smoltified juvenile fish; An apparatus for rearing juvenile fish.

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