Apparatus and method for acclimating smolts to seawater

Abstract

To increase a success rate of seawater acclimation of smolt.SOLUTION: A seawater acclimation device of smolt includes: an aquarium with fresh water stored therein, and breeding the smolt expressing seawater adaptability; and a supply part for supplying the mixed water of the freshwater and the seawater in the aquarium. The supply part supplies the mixed water so that the seawater concentration in the aquarium may rise at a first rate of climb until the seawater concentration in the aquarium reaches a predetermined concentration, and supplies the mixed water so that the seawater concentration in the aquarium may rise at a second rate of climb that is slower than the first rate of climb after the seawater concentration in the aquarium reaches the predetermined concentration.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus and a method for acclimating smolts to seawater. [Background technology]

[0002] In the aquaculture of sea-run fish, such as cherry salmon, juvenile fish (smolts) that have developed the ability to adapt to seawater are acclimated to seawater (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-039335 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional method of seawater acclimation, the survival rate of smolts was only about 50% to 70%, so the success rate of seawater acclimation was not particularly high. Increasing the success rate of seawater acclimation of smolts was a major challenge in increasing the profit margins of the anadromous fish farming industry.

[0005] One aspect of the disclosed technology aims to provide an apparatus and a method for acclimating smolt to seawater that can increase the success rate of acclimating smolt to seawater. [Means for solving the problem]

[0006] One aspect of the disclosed technology is exemplified by the following seawater acclimation device. The seawater acclimation device for smolts of the disclosed technology includes an aquarium that stores freshwater and raises smolts that have developed seawater adaptability, and a supply unit that supplies a mixture of freshwater and seawater to the aquarium. The supply unit supplies the mixed water so that the seawater concentration in the aquarium increases at a first rate of increase until the seawater concentration in the aquarium reaches a predetermined concentration, and after the seawater concentration in the aquarium reaches the predetermined concentration, supplies the mixed water so that the seawater concentration in the aquarium increases at a second rate of increase that is slower than the first rate of increase.

[0007] The smolts to be acclimated to seawater using this seawater acclimation device may be one-year-old fish or one-year-old fish, as long as they have demonstrated the ability to adapt to seawater. In this seawater acclimation device, freshwater is stored in the tank in which the smolts are reared. After a predetermined concentration is reached, the rate of increase of the seawater concentration in the tank is made slower than before the predetermined concentration is reached. For example, the mixed water may be supplied so that the seawater concentration in the tank increases at a rate of 10% per day until the seawater concentration in the tank reaches 50%, and after the seawater concentration in the tank reaches 50%, the mixed water may be supplied so that the seawater concentration in the tank increases at a rate of 10% per seven days.

[0008] In this way, gradually increasing the seawater concentration in the tank promotes the smolts' adaptation to seawater. With this seawater acclimation device, when the seawater concentration in the tank exceeds a predetermined concentration, the rate of increase of the seawater concentration in the tank is slowed down, thereby reducing stress on the smolts due to changes in their growth environment. Therefore, with this seawater acclimation device, the success rate of smolts' acclimation to seawater can be increased.

[0009] Here, the water tank is provided with a drainage means for draining the water exceeding a predetermined amount among the stored mixed water and fresh water, and the supply unit is configured to drain half of the water stored in the water tank. The mixed water may be supplied so that it is replaced every hour. In this way, by draining the water from the tank as the mixed water is supplied, it is possible to keep the water in the tank clean enough for rearing smolts without installing a filtration device to filter the water in the tank.

[0010] The temperatures of the freshwater stored in the tank and the mixed water supplied by the supply unit are preferably about 10 to 20 degrees Celsius, as this temperature range is suitable for rearing smolts.

[0011] The disclosed technology can also be understood from the aspect of a method for acclimating smolt to seawater using the above-mentioned seawater acclimation device. [Effects of the Invention]

[0012] The disclosed technology can increase the success rate of seawater acclimation of smolts. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram illustrating an example of a seawater acclimation device according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of the control device. [Figure 3] FIG. 3 is a diagram showing an example of the flow of a seawater acclimation method using a seawater acclimation device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] <Embodiment> The configurations of the embodiments described below are merely examples, and the disclosed technology is not limited to the configurations of the embodiments. Fig. 1 is a diagram showing an example of a seawater acclimation device according to an embodiment. The seawater acclimation device 1 includes a water tank 10, a freshwater tank 20, a seawater tank 30, and a control device 60.

[0015] The aquarium 10 is a tank for raising cherry salmon smolts 100. Freshwater is stored in the aquarium 10. For example, well water is used as the freshwater. The smolts 100 are cherry salmon fry that have grown and developed the ability to adapt to seawater, making them suitable for migrating to the sea. The smolts 100 may be either yearlings or one-year-olds. The number of smolts 100 to be raised in the aquarium 10 is determined appropriately depending on the size (amount of water stored) of the aquarium 10. For example, if the amount of water stored in the aquarium 10 is one ton, 200 smolts 100 can be raised.

[0016] Fresh water is stored in the fresh water tank 20. For example, well water can be used as the fresh water stored in the fresh water tank 20. 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 mixed water pipe 41. A first valve 21 and a first flow meter 22 are provided on the fresh water pipe 23, in this order from the fresh water tank 20 side. A pump (not shown) is provided in the fresh water tank 20, and the flow rate of fresh water from the fresh water tank 20 to the fresh water pipe 23 is adjusted by the opening degree of the first valve 21. Furthermore, closing the first valve 21 stops the inflow of fresh water from the fresh water tank 20 to the fresh water pipe 23. The flow rate of fresh water flowing through the fresh water pipe 23 is measured by the first flow meter 22.

[0017] Seawater is stored in the seawater tank 30. A seawater pipe 33 is connected to the seawater tank 30. One end of the seawater pipe 33 is connected to the seawater tank 30, and the other end is connected to the mixed water pipe 41. The seawater pipe 33 is provided with a second valve 31 and a second flow meter 32, in that order from the seawater tank 30 side. The seawater tank 30 is provided with a pump (not shown), and the flow rate of seawater from the seawater tank 30 to the seawater pipe 33 is adjusted by the opening degree of the second valve 31. Furthermore, closing the second valve 31 stops the inflow of seawater from the seawater tank 30 to the seawater pipe 33. The flow rate of seawater flowing through the seawater pipe 33 is measured by the second flow meter 32. The freshwater tank 20 and the seawater tank 30 are an example of a "supply section."

[0018] As described above, one end of the mixed water pipe 41 is connected to the fresh water pipe 23 and the seawater pipe 33. The other end of the mixed water pipe 41 is connected to the shower pipe 42 installed above the aquarium 10. Mixed water, which is a mixture of fresh water supplied from the fresh water tank 20 and seawater supplied from the seawater tank 30, flows through the mixed water pipe 41. The mixed water flowing through the mixed water pipe 41 is supplied to the shower pipe 42. When one of the first valve 21 and the second valve 31 is closed and the other is open, either fresh water or seawater flows through the mixed water pipe 41. In this specification, even when either fresh water or seawater flows through the mixed water pipe 41, it is still referred to as mixed water flowing through the mixed water pipe 41.

[0019] Shower pipe 42 is provided above aquarium 10. Shower pipe 42 is provided so as to cross aquarium 10 when aquarium 10 is viewed from above. Shower pipe 42 is provided with a plurality of through-holes 421. The mixed water flowing through shower pipe 42 is supplied to aquarium 10 so as to spray out from through-holes 421. The concentration of seawater in aquarium 10 to which the mixed water has been supplied is measured, for example, by a salinity meter 43 provided in aquarium 10.

[0020] Aquarium 10 is provided with a drain pipe 51 that drains water such as mixed water or fresh water when the amount of water exceeds a specified level. Drain pipe 51 is bent midway, and bent height 511, which is the highest part of the bent section, is set to be the same height as the water surface height H in aquarium 10 when a specified amount of water is stored in aquarium 10. With this configuration, drain pipe 51 can drain the specified amount of water from aquarium 10 even if the specified amount of water is stored in aquarium 10 due to the supply of mixed water from shower pipe 42.

[0021] The first valve 21, first flow meter 22, second valve 31, second flow meter 32, and salinity meter 43 are connected to the control device 60 by signal lines 61, 62, 63, 64, and 65. Fig. 2 is a diagram showing an example of the hardware configuration of the control device. The control device 60 is an information processing device including a central processing unit (CPU) 601, a main memory unit 602, an auxiliary memory unit 603, and a communication unit 604. The CPU 601, the main memory unit 602, the auxiliary memory unit 603, and the communication unit 604 are connected to each other by a connection bus.

[0022] The CPU 601 is also called a microprocessor unit (MPU) or a processor. At least a portion of the processing performed by the CPU 601 may be performed by an integrated circuit (IC) or other digital circuit. The CPU 601 may be a combination of a processor and an integrated circuit. This combination is called, for example, a microcontroller unit (MCU), a system-on-a-chip (SoC), a system LSI, a chipset, etc. In the control device 60, the CPU 601 loads a program stored in the auxiliary memory unit 603 into a work area of ​​the main memory unit 602 and controls peripheral devices through the execution of the program.

[0023] The main storage unit 602 is exemplified as a storage unit that is directly accessed by the CPU 601. The main storage unit 602 includes a random access memory (RAM) and a read only memory (ROM).

[0024] The auxiliary storage unit 603 stores various programs and various data on a recording medium in a readable and writable 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 may be, for example, an erasable programmable ROM (EPROM), a solid state drive (Solid State Drive), State Drive (SSD), Hard Disk Drive (HDD), etc.

[0025] The communication unit 604 is an interface with, for example, signal lines 61, 62, 63, 64, and 65. The communication unit 604 communicates with external devices such as the first valve 21, the first flow meter 22, the second valve 31, the second flow meter 32, and the salinity meter 43 via the signal lines 61, 62, 63, 64, and 65.

[0026] The control device 60 having the above configuration acquires information from the first flow meter 22, the second flow meter 32, and the salinity meter 43 in accordance with a program stored in the auxiliary memory unit 603, and controls the opening and closing of the first valve 21 and the second valve 31 based on the acquired information.

[0027] (Seawater acclimation method using seawater acclimation device 1) A method for acclimating cherry salmon smolts 100 to seawater using the seawater acclimation device 1 will now be described. Fig. 3 is a diagram showing an example of the flow of the seawater acclimation method using the seawater acclimation device according to the embodiment. Hereinafter, the flow of the seawater acclimation method using the seawater acclimation device 1 will be described with reference to Fig. 3.

[0028] In S1, preparations for seawater acclimation are made. That is, freshwater is stored in the aquarium 10, and the smolts 100 to be reared are released into the aquarium 10. In this embodiment, it is assumed that one ton of freshwater is stored in the aquarium 10, and 200 smolts 100 are released into the aquarium 10. Here, in this embodiment, it is assumed that the height of the water surface in the aquarium 10 storing one ton of freshwater is water surface height H. The temperature of the freshwater stored in the aquarium 10 is adjusted to, for example, about 16 degrees Celsius.

[0029] In S2, the control device 60 opens the first flow meter 22 and the second flow meter 32 and starts supplying mixed water from the shower pipe 42 to the aquarium 10. Here, the control device 60 monitors the seawater concentration in the aquarium 10 detected by the salinity meter 43, and controls the opening and closing of the first flow meter 22 and the second flow meter 32 so that the rate of increase of the seawater concentration in the aquarium 10 becomes a first rate of increase. The first rate of increase is, for example, a rate of increase such that the seawater concentration in the aquarium 10 increases by about 10% per day.

[0030] To prevent dirt and the like from accumulating in water tub 10, control device 60 determines the amount of mixed water supplied from shower pipe 42 so that half of the water in water tub 10 is replaced per hour (half of the water in water tub 10 is drained) by supplying mixed water from shower pipe 42 and draining water from water tub 10 via drain pipe 51. The temperature of the mixed water supplied to water tub 10 from shower pipe 42 is adjusted to, for example, about 16 degrees Celsius.

[0031] In S3, the control device 60 determines whether the seawater concentration in the aquarium 10 has reached 50%. If it has reached 50% (YES in S3), the control device 60 executes the process of S4. If it has not reached 50% (NO in S3), the control device 60 executes the process of S2. A seawater concentration of 50% is an example of a "predetermined concentration."

[0032] In S4, the control device 60 monitors the seawater concentration in the aquarium 10 detected by the salinity meter 43, and controls the opening and closing of the first flow meter 22 and the second flow meter 32 so that the rate of increase of the seawater concentration in the aquarium 10 becomes a second rate of increase that is slower than the first rate of increase. The second rate of increase is, for example, a rate of increase such that the seawater concentration in the aquarium 10 increases by 10% every seven days. The amount of mixed water to be supplied is determined in the same manner as in S2.

[0033] In S5, the control device 60 determines whether the seawater concentration of the water stored in the water tank 10 has reached 100%. If it has reached 100% (YES in S5), the control device 60 ends the process. If it has not reached 100% (NO in S5), the control device 60 executes the process of S4.

[0034] In this embodiment, as described above, the seawater acclimation method illustrated in FIG. 3 is carried out over a period of about one to two months in order to gradually increase the seawater concentration in the aquarium 10.

[0035] When the seawater acclimation method using the seawater acclimation device 1 was carried out on 200 cherry salmon smolts (one-year-old fish), the survival rate one month after the seawater concentration reached 100% was 95.5%. Furthermore, when the seawater acclimation method using the seawater acclimation device 1 was carried out on 200 cherry salmon smolts (one-year-old fish), the survival rate one month after the seawater concentration reached 100% was 99%. Since the survival rate with conventional seawater acclimation methods is around 50% to 70%, it can be said that the seawater acclimation method according to this embodiment is effective.

[0036] In this embodiment, water exceeding the water surface height H in the aquarium 10 is drained through the drain pipe 51. In other words, the aquarium 10 is provided with a continuous flow of mixed water supplied from the shower pipe 42. By adopting this continuous flow system, the aquarium 10 according to this embodiment can omit purification processes such as filtration of the water in the aquarium 10. In other words, since a filtration device is not required in the aquarium 10, the structure of the aquarium 10 can be simplified.

[0037] (Variation) The above explanation describes a method for acclimating cherry salmon smolts to seawater. However, the aquarium 10 can also be used for acclimating smolts other than cherry salmon to seawater. Examples of smolts other than cherry salmon include sockeye salmon and rainbow trout. Note that, because rainbow trout can be acclimated to seawater in a shorter period of time than cherry salmon, the seawater concentration may be increased in a shorter period of time than in the seawater acclimation method shown in FIG. 3.

[0038] In the above description, the supply of mixed water from the shower pipe 42 to the water tank 10 is controlled by the control device 60. However, the control device 60 may be omitted from the seawater acclimation device 1. That is, an operator may manually open or close the first valve 21 and the second valve 31 based on the seawater concentration indicated by the salinity meter 43 and the flow rates indicated by the first flow meter 22 and the second flow meter 32.

[0039] 3, the salinity meter 43 is used to determine the seawater concentration in the mixed water, but the salinity meter 43 may be omitted. In this case, the seawater concentration in the mixed water may be determined based on, for example, the amount of fresh water stored in the aquarium 10, the amount of water drained from the drain pipe 51 in response to the supply of mixed water, etc.

[0040] The embodiments and modifications disclosed above can be combined with each other. [Explanation of symbols]

[0041] 1...Seawater acclimatization device 10. Aquarium 20··Freshwater tank 21 First valve 22...1st flow meter 23. Freshwater Pipe 30 Seawater tank 31 Second valve 32...Second flow meter 33 Seawater Pipe 41. Mixing water pipe 42··Shower pipe 421 Through hole 43 Salt concentration meter 51 Drainage pipe 511··Bent High Section 60 Control device 61, 62, 63, 64, 65 Signal lines 601 CPU 602 Main memory 603...Auxiliary storage section 604··Communications Department 100 smolts H: Water surface height

Claims

1. A tank filled with freshwater to raise smolts that have developed the ability to adapt to seawater; a supply unit that supplies a mixture of fresh water and seawater to the water tank, The supply unit includes: supplying the mixed water so that the seawater concentration in the tank increases at a rate of 10% per day until the seawater concentration in the tank reaches 50%; After the seawater concentration in the tank reaches 50%, the mixed water is supplied so that the seawater concentration in the tank increases at a rate of 10% per 7 days. Seawater acclimation equipment for smolts.

2. The water tank is provided with a drainage means for draining the water that exceeds a predetermined amount among the stored water including the mixed water and the fresh water, The supply unit supplies the mixed water so that half of the water stored in the water tank is replaced every hour. The seawater acclimation device for smolts according to claim 1.

3. The temperature of the fresh water stored in the water tank and the mixed water supplied by the supply unit is in the range of 10 to 20 degrees Celsius. The apparatus for acclimating smolts to seawater according to claim 1 or 2.

4. The smolt is a cherry salmon smolt. The apparatus for acclimating smolt to seawater according to any one of claims 1 to 3.

5. Freshwater is stored in the tanks where smolts that have developed the ability to adapt to seawater are raised. supplying a mixture of freshwater and seawater so that the seawater concentration in the tank increases at a rate of 10% per day until the seawater concentration in the tank reaches 50%; After the seawater concentration in the tank reaches 50%, the mixed water is supplied so that the seawater concentration in the tank increases at a rate of 10% per 7 days. How to acclimate smolts to seawater.

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