Aquaculture method

Abstract

The present invention addresses the problem of providing a novel aquaculture method that enables land-based aquaculture of salmonid fish. The present invention further addresses the problem of providing an aquaculture method that makes it possible to improve the survival rate of salmonid fish.　One embodiment of the present invention is an aquaculture method comprising an aquaculture step for growing salmonid fish in an algae solution in which the concentration of algae is not less than 1.0×104 cells / mL.

Description

Aquaculture method

[0001] The present invention relates to an aquaculture method.

[0002] In nature, salmonid fish inhabit environments with good water quality. Therefore, for culturing these fish, sea-cage aquaculture or flow-through systems are often used for the purpose of maintaining water quality above a certain level.

[0003] On the other hand, sea-cage aquaculture has problems such as being limited to coastal areas with sea, and being affected by weather and disasters. Also, the flow-through system has a problem that a large amount of clean water is required.

[0004] In aquaculture, the water quality at the aquaculture site greatly affects the survival rate of fish. In order to improve the survival rate of fish, it is necessary to reduce the organic load such as fish feed residues and excrement, and suppress the deterioration of water quality. Patent Document 1 discloses a method of suppressing the deterioration of water quality at an aquaculture site by feeding a feed containing a cellulose ester to aggregate fish feces.

[0005] Japanese Patent Application Laid-Open No. 2020-150859

[0006] In recent years, the development of land-based aquaculture facilities that enable aquaculture regardless of location has been promoted. However, as described above, since salmonid fish are usually grown in an environment with high transparency and good water quality, a high-cost water purification device has been required.

[0007] The present invention has been made in view of such circumstances, and an object thereof is to provide a novel aquaculture method capable of land-based aquaculture of salmonid fish. Furthermore, an object of the present invention is to provide an aquaculture method capable of improving the survival rate of salmonid fish.

[0008] As a result of intensive studies by the present inventors, it has been found that land-based aquaculture of salmonid fish is possible by using algae. Also, surprisingly, it has been found that the survival rate of salmonid fish is improved by using algae, and the present invention has been completed.

[0009] According to the present invention, the following is provided. [1] The concentration of algae is 1.0×10

[0001] A farming method comprising a farming step of growing salmonid fish in an algal solution of cells / mL or more. [2] The above concentration is 5000 × 10 ４ A method of aquaculture according to [1], wherein the cell density is less than or equal to 3 / mL. [3] A method of aquaculture according to [1] or [2], wherein the algae is at least one species selected from the group consisting of cyanobacteria, grey algae, red algae, green algae, cryptophytes, haptophytes, heterokonts, dinoflagellates, chlorarachnion algae, and Euglena algae. [4] A method of aquaculture according to any one of [1] to [3], wherein the fish is at least one species selected from the group consisting of cherry salmon, amago trout, Taiwanese trout, Biwa trout, rainbow trout, sockeye salmon, kunimasu trout, chinook salmon, salmon, coho salmon, pink salmon, Apache trout, Mexican golden trout, throat trevally, and gira trout. [5] A method of aquaculture according to any one of [1] to [4], further comprising a water purification step. [6] A method of aquaculture according to [5], wherein the water purification step utilizes algal culture, physical filtration, or biological filtration. [7] The aquaculture method according to [5] or [6], wherein the purification step utilizes algal cultivation. [8] The aquaculture method according to any one of [1] to [7], wherein it is a closed-loop system.

[0010] According to the present invention, a novel aquaculture method is available that enables land-based cultivation of salmonid fish. Furthermore, according to the present invention, an aquaculture method is available that can improve the survival rate of salmonid fish.

[0011] Figure 1 is a diagram showing an overview of the aquaculture system according to the first embodiment of the present invention. Figure 2 is a flowchart showing an example of processing in the aquaculture system according to the first embodiment. Figure 3 is a flowchart showing an example of processing in the aquaculture system according to the first embodiment when continuous circulation is in operation. Figure 4 is a diagram showing an overview of the aquaculture system according to the second embodiment of the present invention. Figure 5 is a diagram showing an overview of the aquaculture system according to the third embodiment of the present invention. Figure 6 is a diagram showing an overview of the aquaculture system according to the fourth embodiment of the present invention. Figure 7 is a diagram showing the measurement results of the algae concentration in the algae solutions of Examples 1 to 4. Figure 8 is a diagram showing the survival rate results of Amago trout in Examples 1 to 4 and Comparative Example 1. Figure 9 is a diagram showing the measurement results of the algae concentration in the algae solution of Example 5. Figure 10 is a diagram showing the measurement results of the ammonia concentration in the algae solutions of Example 5 and Comparative Example 2. Figure 11 is a diagram showing the survival rate results of rainbow trout in Example 5 and Comparative Example 2.

[0012] The present invention will now be described in detail. The present invention is not limited to these descriptions. The features of the embodiments shown below can be combined with each other. Furthermore, each feature constitutes an invention independently. In addition, any element of the embodiments below that is not defined in the claims is an optional element and can be omitted. In this specification, any number of zeros may be added to the end of numerical values. For example, one zero may be added after "1.4" to make it "1.40".

[0013] <Explanation of Terms> In this specification, for example, the description "X to Y" means that it is greater than or equal to X and less than or equal to Y.

[0014] 1. Aquaculture Method The aquaculture method according to this embodiment includes an aquaculture step of growing salmonid fish in an algal solution. The aquaculture method according to this embodiment may further include an algal preparation step of preparing an algal solution and a water purification step of purifying water. Furthermore, the aquaculture method according to this embodiment is typically a closed-loop system. Such a system can reduce the environmental burden near the aquaculture farm. Moreover, according to the aquaculture method according to this embodiment, the survival rate of salmonid fish can be improved. In other words, one embodiment of the present invention is a method for improving the survival rate of salmonid fish.

[0015] 1.1 Algae Preparation Process In the algae preparation process according to this embodiment, an algae solution is prepared. In the algae preparation process according to this embodiment, the algae solution may be prepared directly in the cultivation tank used in the cultivation process described later, or it may be prepared by introducing an appropriate amount of algae from an algae tank provided separately from the cultivation tank into the cultivation tank. Furthermore, the algae used may be purchased or collected algae, or they may be obtained by culturing these algae. The solvent (water) for the algae solution according to this embodiment can be appropriately selected depending on the fish being cultivated, and for example, seawater, freshwater (for example, tap water (including water purified by a water purifier)), or brackish water can be used.

[0016] The algae according to this embodiment can be appropriately selected according to the types of fish to be cultured and the types of water (freshwater, seawater, brackish water, etc.). The algae according to this embodiment is preferably at least one selected from the group consisting of cyanobacteria (blue-green algae), glaucophytes, red algae, green algae, cryptophytes, haptophytes, heterokonts, dinoflagellates, Chlorarachniophyta, and Euglena. The algae according to this embodiment is more preferably at least one selected from the group consisting of cyanobacteria (blue-green algae), green algae, heterokonts, Chlorarachniophyta, and Euglena. Examples of the green algae according to this embodiment include Chlorella (Chlorella, Parachlorella, etc., those included in Chlorella), Chlamydomonas, Scenedesmus, etc. Examples of the heterokonts according to this embodiment include Nannochloropsis, etc. Examples of the heterokonts according to this embodiment include diatoms, brown algae, etc. The algae according to this embodiment is even more preferably at least one selected from the group consisting of cyanobacteria (blue-green algae), Chlorella (Chlorella, Parachlorella, etc., those included in Chlorella), Chlamydomonas, Scenedesmus, Nannochloropsis, diatoms, brown algae, and Euglena. When the fish to be cultured is a marine fish, green algae (e.g., Chlorella), haptophytes, heterokonts, Chlorarachniophyta or Euglena is preferable. When the fish to be cultured is a freshwater fish, green algae (e.g., Chlorella), haptophytes, heterokonts or Euglena is preferable.

[0017] The concentration of algae in the algae solution according to this embodiment is 1.0×10 ４ cells / mL or more. Also, the concentration of algae in the algae solution according to this embodiment is preferably, for example, 5000×10 ４ cells / mL or less, more preferably 1000×10 ４ cells / mL or less, and even more preferably 500×10 ４ cells / mL or less. The concentration of algae in the algae solution is, for example, 1.0×10 ４ , 5.0×10 ４ , 10×10 ４ , 20×10 ４ , 30×10 ４ , 40×10 ４ , 50×10４ , 60 x 10 ４ , 100 x 10 ４ , 190 x 10 ４ , 200 x 10 ４ , 210 × 10 ４ , 300 x 10 ４ , 400 x 10 ４ , 470 x 10 ４ , 500 x 10 ４ , 600 x 10 ４ , 700 x 10 ４ , 800 x 10 ４ , 900 x 10 ４ , 1000 x 10 ４ , 2000 x 10 ４ ,3000×10 ４ , 4000 x 10 ４ or 5000 x 10 ４ The value may be cells / mL, or within the range between any two of the values ​​exemplified here. If the algal concentration in the algal solution is above the lower limit, it will have sufficient water purification capabilities, thereby suppressing the deterioration of water quality in aquaculture sites. Furthermore, surprisingly, if the algal concentration in the algal solution is above the lower limit, the survival rate of fish can be improved. If the algal concentration in the algal solution is below the upper limit, the likelihood of algal clogging of fish gills or inability to find sufficient food is reduced, thereby improving the survival rate. The algal concentration can be influenced, for example, by the intensity and amount of light from LEDs, the amount of air supplied by air pumps, and CO2. ２ CO2 emissions from introducing equipment, etc. ２ CO2 can be adjusted by the amount of CO2 added and the amount of culture medium added. The intensity and amount of light and the amount of air added should be such that the concentration of algae can be controlled within the above range. ２ The amount added should be such that algae and fish can survive, the pH is between 6.0 and 8.5, and the algal concentration can be controlled within the above range. Conventional known culture media can be used as long as they allow for control of the algal concentration within the above range.

[0018] Furthermore, the concentration of algae in the algal solution according to this embodiment shall be 100 × 10⁻¹⁰ for at least a certain period (for example, 5 days or more, 10 days or more, 50 days or more) during the cultivation process described later.４ A concentration of cells / mL or higher is preferable. Growing fish at such an algal concentration for a predetermined period of time or longer can improve the survival rate of the fish.

[0019] 1.2 Aquaculture Process In the aquaculture process according to this embodiment, salmonid fish are grown in an algal solution. Specifically, salmonid fish are introduced into the algal solution in the aquaculture tank (introduction step), and growth begins. Salmonid fish normally inhabit environments with good water quality (specifically, with little suspended matter such as algae), but surprisingly, even with the relatively high concentration of algae described above, salmonid fish can be grown for a long period of time. In this embodiment, the salmonid fish is preferably at least one species selected from the group consisting of cherry salmon (Oncorhynchus masou), amago (satsuki trout) (O. m. ishikawae), Taiwanese trout (O. formosanus), Biwa trout (O. m. rhodurus), rainbow trout (O. mykiss), sockeye salmon (O. nerka), kunimasu (O. kawamurae), chinook salmon (O. tschawytscha), chum salmon (O. keta), coho salmon (O. kisutch), pink salmon (O. gorbuscha), Apache trout (O. apache), Mexican golden trout (O. chrysogaster), throat-scarping trout (O. clarkii), and gilae trout (O. gilae gilae).

[0020] The cultivation process according to this embodiment may further include steps for adjusting various parameters of the cultivation tank (temperature adjustment step, dissolved oxygen concentration adjustment step, and pH adjustment step). Specifically, the temperature, dissolved oxygen concentration, and pH of the algae solution can be measured continuously or at regular intervals and adjusted to a predetermined range. The temperature of the algae solution can be, for example, 5 to 35°C, preferably 10 to 25°C. Conventionally known temperature control devices can be used for the temperature adjustment step. The dissolved oxygen concentration of the algae solution can be, for example, 6.0 mg / L or more, preferably 7.0 mg / L or more. The pH of the algae solution can be, for example, 6.0 to 8.5, preferably 6.7 to 7.5. As a pH adjustment step, for example, a method of increasing the pH by adding sodium bicarbonate can be mentioned.

[0021] The aquaculture process according to this embodiment may further include a step of adjusting other parameters of the aquaculture tank. Other parameters include those listed in the "Aquaculture Water Standards, 8th Edition (Japan Fisheries Resources Conservation Association)," such as ammonia concentration, nitrite concentration, nitrate concentration, phosphorus concentration, carbon dioxide concentration, COD value, BOD value, and turbidity of the algal solution. These parameters can be adjusted according to the fish species, and preferably, they can be adjusted to the numerical range of each parameter specified for each fish species in the "Aquaculture Water Standards, 8th Edition (Japan Fisheries Resources Conservation Association)." By adjusting each parameter, fish can be cultivated to a marketable size with good quality.

[0022] 1.3 Purification Process In the purification process according to this embodiment, water purification is performed. The purification process according to this embodiment can utilize algal cultivation, physical filtration, or biological filtration. The purification process according to this embodiment preferably utilizes algal cultivation, and it is even more preferable to use a combination of algal cultivation and physical filtration or biological filtration.

[0023] In the water purification process utilizing algae cultivation, the algae consume nitrogen compounds (specifically ammonia, nitrite, nitrate), phosphorus, etc., derived from excrement (feces, urine) and leftover feed discharged from fish growing in the aquaculture tanks. The aforementioned algae tanks and aquaculture tanks can be used as water purification devices utilizing algae cultivation. In conventional closed-loop land-based aquaculture, a separate water purification tank connected to the aquaculture tank is required as a water purification device in addition to the aquaculture tanks. However, according to the aquaculture method of this embodiment, a separate water purification tank (e.g., a nitrification-denitrification tank) is not required. Furthermore, since the algae cultivated in the water purification process can be used in the aforementioned algae preparation process and aquaculture process, no waste is generated, and costs are reduced.

[0024] In this embodiment, physical filtration can be further utilized as a purification step. Examples of physical filtration include sand filtration using sand and membrane filtration using a filter. The material of the filter is not particularly limited, and examples include metal filters such as metal mesh, chemical fiber filters, and natural fiber filters. The mesh size of the filter in this embodiment can be appropriately set according to the size of the material to be filtered. Examples of material to be filtered include dead fish, scales, fish feces, and leftover feed. When the material to be filtered is fish feces and leftover feed, for example, a commercially available sponge filter can be used. In this embodiment, water purification can be performed more efficiently by combining the purification step using algae cultivation described above with the purification step using physical filtration. In this case, it is preferable that the water purification device using algae cultivation and the water purification device using physical filtration are connected in series.

[0025] In this embodiment, biological filtration can be further utilized as a purification process. For example, nitrifying bacteria (nitrite bacteria, nitrate bacteria) and denitrifying bacteria can be used for biological filtration. Specifically, a filter or porous body on which nitrifying bacteria are attached can be used. The principle of biological filtration in this embodiment is, for example, (1) ammonia derived from excrement (feces, urine) and leftover feed discharged from fish is oxidized to nitrite by nitrite bacteria, (2) nitrite is converted to nitrate by nitrifying bacteria, and (3) nitrate is consumed by denitrifying bacteria. In this embodiment, water purification can be performed more efficiently by combining the system utilizing algae cultivation described above with the system utilizing biological filtration. In this case, the water purification system utilizing algae cultivation and the purification process utilizing biological filtration may be connected in series or in parallel.

[0026] 1.4 Other Steps The aquaculture method according to this embodiment may further include other steps. Other steps include an algae collection step for collecting algae, a UV sterilization step for sterilizing general bacteria, pathogenic bacteria (e.g., E. coli), and viruses. By including a UV sterilization step, the number of pathogenic bacteria and viruses in the aquaculture system (specifically, the aquaculture tank, algae tank, and water tank) can be kept low. This makes it possible to maintain a cleaner environment for the growth of fish and algae, and to maintain the survival rate of fish and algae. Furthermore, even when a UV sterilization step is included, the concentration of algae can be reduced to 1.0 × 10⁻⁶. ４ Cells / mL or more, preferably 1.0 × 10 ４ ~5000 x 10 ４ Because the levels can be controlled down to the cell / mL level, it is possible to suppress pathogens and viruses to a degree that prevents fish from developing disease, while simultaneously allowing fish to grow over a long period of time.

[0027] 2. Aquaculture System The aquaculture system for implementing the aquaculture method according to this embodiment will be described below.

[0028] 2.1 First Embodiment Figure 1 is a diagram showing an overview of the aquaculture system 10 according to this embodiment. As shown in Figure 1, the aquaculture system 10 comprises an aquaculture tank 20, an algae tank 30, and a water tank 60. An algae solution 22 is prepared in the aquaculture tank 20, and fish 24 are grown in the algae solution 22. Algae 32 for input are prepared in the algae tank 30. Water 62 for input is prepared in the water tank 60. The aquaculture tank 20 and the algae tank 30 are connected by an algae introduction pipe 40 and an algae discharge pipe 50. Furthermore, the aquaculture tank 20 and the water tank 60 are connected by a water introduction pipe 70. When tap water is used as the water source, tap water supply piping may be used instead of the water tank 60 and the water introduction pipe 70.

[0029] Algae introduction pump 42 and water introduction pump 72 are provided in the paths of the algae introduction pipe 40 and the water introduction pipe 70, respectively. Furthermore, algae introduction on-off valve 44 and water introduction on-off valve 74 are provided in the paths of the algae introduction pipe 40 and the water introduction pipe 70, respectively. The algae introduction on-off valve 44 and water introduction on-off valve 74 may be manually operated on-off valves, or they may be electric or air-operated automatic on-off valves.

[0030] The aquaculture system 10 according to this embodiment includes aquaculture means for growing salmonid fish 24 in an algal solution. The aquaculture system 10 according to this embodiment may further include algal preparation means for preparing an algal solution 22 and water purification means for purifying water.

[0031] 2.1.1 Algae Preparation Means In the algae preparation means according to this embodiment, an algae solution 22 is prepared. The algae solution 22 according to this embodiment is prepared by introducing algae and water from the algae tank 30 and the water tank 60, respectively. The concentration of algae in the algae solution 22 according to this embodiment is 1.0 × 10⁻⁶ ４ The concentration is 5000 × 10⁻¹⁰ cells / mL or higher. The concentration of algae in the algal solution 22 according to this embodiment is 5000 × 10⁻¹⁰ ４It is preferable that the concentration is less than or equal to cells / mL. In this embodiment, in order to maintain the algae concentration within the above range, the starting and stopping of the algae introduction pump 42 and the water introduction pump 72, as well as the opening and closing of the algae introduction valve 44 and the water introduction valve 74, are performed at predetermined timings. For example, when increasing the algae concentration, the algae introduction valve 44 is opened and the algae introduction pump 42 is started to introduce the algae 32 into the cultivation tank 20. Conversely, when decreasing the algae concentration, the water introduction valve 74 is opened and the water introduction pump 72 is started to introduce the water 62 into the cultivation tank 20.

[0032] The algae tank 30 according to this embodiment includes an LED, an air pump, and CO2. ２ An introduction device can be installed. These devices allow for the control of light intensity and quantity, air input rate, and CO2. ２ By adjusting the amount added, the concentration of algae in the added algae 32, and consequently in the algal solution 22, can be set to an appropriate range.

[0033] 2.1.2 Aquaculture Means The aquaculture system 10 according to this embodiment includes aquaculture means for growing salmonid fish 24 in an algal solution. Although not shown in Figure 1, the aquaculture means according to this embodiment may include means for adjusting various parameters of the aquaculture tank 20 (temperature adjustment means, dissolved oxygen concentration adjustment means, pH adjustment means, nitrogen compound concentration adjustment means, phosphorus concentration adjustment means, carbon dioxide adjustment means, COD adjustment means, BOD adjustment means, turbidity adjustment means, and).

[0034] 2.1.3 Purification Means The aquaculture system 10 according to this embodiment further comprises a purification means for purifying water. In this embodiment, the purification means utilizes algae cultivation. As the purification means, algae present in the aquaculture tank 20 and the algae tank 30 can be used. The algae solution 22 in the aquaculture tank 20 contains nitrogen compounds derived from excrement (feces, urine) and leftover feed discharged from the fish 24. For example, in the aquaculture tank 20, nitrogen compounds and phosphorus derived from excrement (feces, urine) and leftover feed discharged from the fish 24 are consumed by the algae. In addition, a portion of the algae solution 22 is discharged from the aquaculture tank 20 to the algae tank 30 through the discharge pipe 50, and nitrogen compounds are also consumed by the algae in the algae tank 30. Discharge of the algae solution 22 can be performed by overflow by setting the installation position of the discharge pipe 50 on the aquaculture tank 20 side to the upper limit of the water level in the aquaculture tank 20, as shown in Figure 1. Furthermore, a check valve can be optionally installed in the discharge pipe 50, thereby preventing the input algae 32 from flowing back out of the algae tank 30.

[0035] 2.1.4 Other Means The aquaculture system 10 according to this embodiment may further be equipped with other means. Other means include UV sterilization means for killing bacteria and viruses. By providing UV sterilization means, the number of pathogenic bacteria and viruses in the aquaculture system 10 (specifically, the aquaculture tank 20, algae tank 30, and water tank 60) can be kept low.

[0036] 2.1.5 Continuous Circulation In addition, the aquaculture system 10 according to this embodiment may have the algae introduction pump 42 running continuously and continuously introduce the algae 32 into the aquaculture tank 20. In this case, the algae will circulate between the aquaculture tank 20 and the algae tank 30 through the discharge pipe 50 (continuous circulation). In this case, the concentration of algae in the algae solution 22 and the concentration of algae in the introduced algae 32 will be the same. When the aquaculture system 10 according to this embodiment is in continuous circulation mode, the LED, air pump, and CO ２ The introduction device can be installed in the algae tank 30 and / or the aquaculture tank 20. When the aquaculture system 10 according to this embodiment is in a state of continuous circulation, the intensity and amount of light, the amount of air introduced, and CO2 ２By adjusting the amount of CO2 added, algae are continuously cultured and the algae concentration is adjusted to a predetermined range. When these devices are installed in the cultivation tank 20, the intensity and amount of light, the amount of air added, and CO2 are controlled. ２ The amount of the substance added is adjusted to a level that does not affect the survival rate of the fish 24.

[0037] In this embodiment, the amount of water (circulation rate) when algae circulate between the cultivation tank 20 and the algae tank 30 can be adjusted based on the amount of algae solution 22 in the cultivation tank 20, the growth status of the fish 24, the cultivation status of the algae, the concentration of the algae, parameters of the cultivation tank 20 and the algae tank 30 (for example, temperature, dissolved oxygen, pH, ammonia concentration, nitrite concentration, nitrate concentration, phosphorus concentration, carbon dioxide concentration, COD value, BOD value, turbidity), the status of UV sterilization, etc. In this embodiment, the circulation rate can be, for example, 0.1 to 100 L / min when the amount of algae solution 22 held in the cultivation tank 20 is 1000 L. The circulation rate may be, for example, 0.1, 0.3, 0.5, 0.7, 0.8, 0.9, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, or 100 L / min when the algal solution 22 in the cultivation tank 20 is 1000 L, and may also be within the range of any two of the values ​​exemplified here.

[0038] 2.1.6 Processing of the Aquaculture System Figure 2 is a flowchart showing an example of processing in the aquaculture system 10 according to this embodiment. As shown in Figure 2, first, the algae concentration of the algae solution 22 in the aquaculture tank 20 is 1.0 × 10 ４ It is determined whether the concentration is greater than or equal to cells / mL (S10). The concentration of algae may be determined based on an image of the algal solution 22 in the cultivation tank 20 taken with a camera or the amount of light measured by a sensor, or a value measured by the user by taking a sample of the algal solution 22 may be input. If the concentration of algae in the cultivation tank 20 is 1.0 × 10 ４ If the cell / mL is less than (No. in S10), the algae introduction pump 42 is started and the algae introduction valve 44 is opened, and the algae 32 for introduction are introduced into the cultivation tank 20 (S20). The algae concentration in the cultivation tank 20 is 1.0 × 10 ４If the cell count is greater than or equal to cells / mL (Yes in S10), the algae introduction pump 42 is stopped and the algae introduction valve 44 is opened (S30). After the treatment in S30, the algae concentration in the algae solution 22 of the cultivation tank 20 is 5000 × 10 ４ It is determined whether the concentration is less than or equal to cells / mL (S40). The algal concentration is measured in the same way as in S20. The algal concentration in the cultivation tank 20 is 5000 × 10 ４ If the cell / mL exceeds (No. in S40), the water introduction pump 72 is started and the water introduction valve 74 is opened, and the water for introduction 62 is introduced into the aquaculture tank 20 (S50). The algal concentration in the aquaculture tank 20 is 5000 × 10 ４ If the cell / mL is less than or equal to (Yes in S40), the water introduction pump 72 is stopped and the water introduction valve 74 is closed (S60). After the process in S60, it is determined whether the fish 24 in the aquaculture tank 20 are ready for shipment (S70). Whether they are ready for shipment may be determined based on the size of the fish 24 or based on the cultivation period. If the fish 24 are ready for shipment (Yes in S70), the system terminates. If the fish 24 are not ready for shipment, the process returns to S10.

[0039] While the above process is being carried out, the algae present in the cultivation tank 20 purify the water. Also, as a result of the process in S10 or S50 described above, when the input algae 32 or input water 62 is introduced into the cultivation tank 20, the water level rises above a certain level (above the installation position of the discharge pipe 50), and the overflowing algae solution 22 is discharged into the algae tank 30 through the discharge pipe 50. The algae present in the algae tank 30 also purify the water. Thus, according to the configuration of this embodiment, a closed-loop aquaculture system 10 that does not require a separate water purification means can be provided.

[0040] 2.1.6.1 Treatment of the Aquaculture System (In the Case of Continuous Circulation) Figure 3 is a flowchart showing an example of treatment in the case of continuous circulation as described above for the aquaculture system 10 according to this embodiment. As shown in Figure 3, first the concentration of algae in the algal solution 22 of the aquaculture tank 20 is 1.0 × 10 ４It is determined whether the concentration is greater than or equal to cells / mL (S110). The concentration of algae may be determined based on an image of the algal solution 22 in the cultivation tank 20 taken with a camera or the amount of light measured by a sensor, or a value measured by the user by taking a sample of the algal solution 22 may be input. The concentration of algae in the cultivation tank 20 is 1.0 × 10 ４ If the cell / mL is less than (No. S110), the LEDs, air pumps, and CO2 installed in the algae tank 30 and / or the aquaculture tank 20 are turned off. ２ Activate one or all of the introducing equipment, or adjust the operating equipment to control the intensity and amount of light, the amount of air injected, and CO2. ２ Increase any or all of the input amounts (S120). The algae concentration in the cultivation tank 20 is 1.0 × 10 ４ If the cell / mL is greater than or equal to (Yes in S110), the algal concentration in the algal solution 22 of the cultivation tank 20 is 5000 × 10 ４ It is determined whether the concentration is less than or equal to cells / mL (S130). The algal concentration is measured in the same way as in S110. The algal concentration in the cultivation tank 20 is 5000 × 10 ４ If the cell / mL is less than or equal to (Yes in S140), the LEDs, air pumps, and CO2 installed in the algae tank 30 and / or the aquaculture tank 20 are used. ２ The state of the introduction device is maintained (S140). The algae concentration in the cultivation tank 20 is 5000 × 10 ４ If the cell / mL exceeds the limit (No. S130), the LEDs, air pumps, and CO2 installed in the algae tank 30 and / or the aquaculture tank 20 will be turned off. ２ Stop the operation of one or all of the introduced equipment, or adjust the operating equipment to control the intensity and amount of light, the amount of air supplied, and CO2. ２ The amount of input is reduced by one or all of the following (S150). Alternatively, as an alternative to the treatment in S150, the water introduction pump 72 may be started and the water introduction valve 74 may be opened to introduce the input water 62 into the aquaculture tank 20 (S160). After the treatment in S160, the concentration of algae in the algae solution 22 in the aquaculture tank 20 is 5000 × 10 ４ The concentration is re-evaluated to be less than or equal to cells / mL (S170). The concentration of algae in the cultivation tank 20 is 5000 × 10 ４ If the cell / mL exceeds (S170 No.), return to the S170 procedure. If the algal concentration in cultivation tank 20 is 5000 × 10 ４If the cell / mL is less than or equal to (Yes in S170), the water introduction pump 72 is stopped and the water introduction valve 74 is closed (S180). After the processing in S120, S140, S150, or S180, it is determined whether the fish 24 in the aquaculture tank 20 are ready for shipment (S190). Whether they are ready for shipment may be determined based on the size of the fish 24 or based on the cultivation period. If the fish 24 are ready for shipment (Yes in S190), the system terminates. If the fish 24 are not ready for shipment (No in S190), the process returns to S110.

[0041] Next, modifications of the aquaculture system 10 of the above-described embodiment will be explained. However, components identical to those in the above-described embodiment will be denoted by the same reference numerals and their descriptions will be omitted. First, a modification (second embodiment) in which an algae recovery means is provided as an alternative to the algae preparation means for reducing the concentration of algae will be explained. Next, modifications (third to fourth embodiments) in which the tank configuration differs from that of the first embodiment will be explained. A combination of the second embodiment and any one of the third to fourth embodiments is also an embodiment of the present invention.

[0042] 2.2 Figure 4 of the second embodiment shows an overview of the aquaculture system 10 according to this embodiment. The aquaculture system 10 according to this embodiment does not have a water tank 60.

[0043] In the aquaculture system 10 according to this embodiment, an algae recovery means may be provided as an alternative to the algae preparation means for reducing the algae concentration (not shown). When reducing the algae concentration, a portion of the algae can be recovered from the algae solution 22 in the aquaculture tank 20 by the algae recovery means. Known algae recovery methods can be used as the algae recovery means, such as the coagulation separation method, the flotation separation method, the centrifugal separation method, and the membrane filtration method. Examples of membrane filtration methods include recovering the algae from the algae solution 22 in the aquaculture tank 20 using a net or filter, using a cassette-type algae separation membrane, using a mesh with an opening that allows for the recovery of algae, and using a drum filter.

[0044] 2.3 Figure 5 of the third embodiment shows an overview of the aquaculture system 10 according to this embodiment. The aquaculture system 10 according to this embodiment does not have an algae tank 30. Since the algae according to this embodiment can be cultured and grown even in the aquaculture tank 20, the concentration of algae in the algae solution 22 is set to 1.0 × 10 ４ If the cell / mL can be maintained at or above, the algae tank 30 is not essential. In this embodiment, the LED, air pump, and CO2 introduction device can be installed in the aquaculture tank 20.

[0045] 2.4 Fourth Embodiment Figure 6 is a diagram showing an overview of the aquaculture system 10 according to this embodiment. The aquaculture system 10 according to this embodiment further includes a nitrification-denitrification tank 80. The nitrification-denitrification tank 80 includes a nitrification-denitrification filter 82. The nitrification-denitrification tank 80 and the algae tank 30 are connected by a connecting pipe 90. In this embodiment, when the water level rises above a certain level (above the mounting position of the discharge pipe 50), the overflowing algae solution 22 is discharged to the algae tank 30 through the discharge pipe 50. The discharged algae solution 22 and the algae solution in the algae tank 30 move to the nitrification-denitrification tank 80 through the connecting pipe 90. The moved algae solution is biologically filtered by the nitrification-denitrification filter 82. The treated water that has passed through the nitrification-denitrification filter 82 is circulated to the aquaculture tank 20 through the algae introduction pipe 40. Thus, in this embodiment, algae cultivation and biological filtration can also be used in combination as a purification means. In this embodiment, the algae solution 22 moves in the order of cultivation tank 20, nitrification-denitrification tank 80, algae tank 30, and cultivation tank 20. However, an embodiment in which the nitrification-denitrification tank 80 and the algae tank 30 are swapped is also an embodiment of the present invention. Furthermore, an embodiment in which a physical filtration device utilizing physical filtration is added, and an embodiment in which the nitrification-denitrification tank 80 is replaced with a physical filtration device are also embodiments of the present invention. In the embodiment in which a physical filtration device is added, the physical filtration device can be installed, for example, at the inlet of the discharge pipe 50 on the cultivation tank 20 side, in the middle of the discharge pipe 50, or at the outlet of the discharge pipe 50 on the algae tank 30 side. Also, in this embodiment, the algae tank 30 and the nitrification-denitrification tank 80 are connected in series, but an embodiment in which they are connected in parallel is also an embodiment of the present invention.

[0046] The present invention will be described in more detail below based on the following examples. The examples described below are merely representative examples of the present invention and should not be interpreted as narrowing the scope of the invention.

[0047] <Examples 1-3> (Algae preparation process) Tests were conducted using an aquaculture system (specifically, the aquaculture system shown in Figure 4) that includes a cultivation tank and an algae tank.

[0048] First, the algae to be used were prepared. The valve in the piping between the cultivation tank and the algae tank was closed, and the pump for introducing the algae was stopped. The algae were cultured in the algae tank, and 1.0 × 10⁻⁶ ４ Cells / mL or more and 5000 x 10 ４ Algae for input were prepared at a cell / mL or less. The algae and algal concentrations used in each example are as follows. The water used in this experiment was purified tap water using a water purifier. An LED and an air pump were installed in the algae tank, and by operating, adjusting, and / or stopping them respectively, continuous algal cultivation was carried out in the algae preparation process and the cultivation and purification processes described later. Example 1: Green algae (collected in Nagahama City; Chlorella), 91 x 10⁻⁶ ４ Cells / mL Example 2: Green algae (Chlamydomonas), 4 × 10 ４ Cells / mL Example 3: Green algae (collected in Nagahama City), 36 x 10 ４ cells / mL

[0049] Next, the on-off valve located in the piping between the aquaculture tank and the algae tank was opened, and the algae introduction pump was started to introduce the algae into the aquaculture tank. After introduction, the amount of algae solution in the aquaculture tank was 1000 L.

[0050] (Cultivation Process and Purification Process) In this experiment, the on / off valve installed in the piping between the cultivation tank and the algae tank was kept open at all times, the algae introduction pump was kept running at all times, and the algae solution was continuously circulated between the cultivation tank and the algae tank (i.e., the algae concentration was the same in both the cultivation tank and the algae tank). At this time, the circulation rate was approximately 10 to 25 L / min.

[0051] Approximately 100g of amago trout were purchased from a trout farm and eight were placed in each rearing tank to begin rearing. During the rearing period, the temperature of the algal solution was controlled to 15.0-16.0°C, the dissolved oxygen concentration to 7 mg / L or higher, and the pH to 6.7-7.5. In addition, the concentration of algae in the algal solution was measured periodically during the rearing period. Furthermore, the number of surviving amago trout was recorded. The feeding rate (amount of feed (g) relative to total fish weight (g)) was approximately 1-2% by mass.

[0052] <Example 4> In Examples 1 to 3, the surviving amago trout (total of 7 fish; Example 1: 2 fish, Example 2: 2 fish, Example 3: 3 fish) 110 days after the start of cultivation were transferred to the cultivation tank used in Example 2 (type of algae: green algae (Chlamydomonas)), and cultivation was continued. The concentration of algae in the cultivation tank at the start of cultivation in Example 4 was 80 × 10 ４ The cell count was per mL. The set temperature, dissolved oxygen concentration, and pH during the cultivation period were the same as described above. An LED and an air pump were installed in the algae tank, and the algae were continuously cultured by operating, adjusting, and / or stopping them respectively. In addition, the concentration of algae in the algae solution was measured periodically during the cultivation period. Furthermore, the number of surviving amago trout was recorded. On the 116th day after the start of cultivation in Example 4 (226th day after the start of cultivation in Examples 1-3), the evaluation described below (fish body measurement and sensory evaluation) was performed. The feeding rate (amount of feed (g) relative to total fish body weight (g)) was approximately 1-2% by mass.

[0053] <Comparative Example 1> The above-mentioned algae tank was replaced with a biological filtration system tank using MBBR fluidized bed filter material, a conventionally known nitrification-denitrification material, as a carrier. Furthermore, as a physical filtration system, a polyester wool mat was installed at the outlet of the discharge pipe 50 on the algae tank side to remove debris and leftover feed. In this way, the test was conducted with a system that combined physical and biological filtration. No algae were used in this comparative example. In the aquaculture process and purification process, aquaculture and evaluation were carried out under the same conditions as in Examples 1 to 3, except that 45 amago trout were introduced. The feeding rate (amount of feed (g) relative to total fish weight (g)) was approximately 2 to 3 mass%.

[0054] <Evaluation Results> (Algae concentration in algae solution) Figure 7 shows the results of the algae concentration in the algae solution in Examples 1 to 4. In Examples 1 to 4, the algae concentration in the algae solution was 1.0 × 10⁻⁶ during the cultivation period. ４ Cells / mL or more and 5000 x 10 ４ The concentration was maintained at cells / mL or less. In each example, the algal concentration in the cultivation tank during the cultivation period was 42.5 × 10 in Example 1. ４ ~470.0 x 10 ４ Cells / mL, 1.25 × 10 in Example 2 ４ ~62.0 x 10 ４ Cells / mL, 20.8 × 10 in Example 3 ４ ~179.3 x 10 ４ Cells / mL, in Example 4, 41.5 × 10 ４ ~209.0 x 10 ４ The cell count was per mL.

[0055] (Survival Rate) Figure 8 shows the results of the survival rate of Amago trout in Examples 1-4 and Comparative Example 1. From the results of Examples 1-3 and Example 4, the concentration of algae in the algal solution was 1.0 × 10⁻⁶. ４ Under conditions with a cell / mL or higher, we were able to cultivate Amago trout for a long period of 226 days in total from the start of cultivation. Furthermore, surprisingly, in Examples 1 to 4, the survival rate tended to be higher than in Comparative Example 1, which used a conventional nitrification-denitrification tank.

[0056] (Fish Measurement) Five amago trout that survived until day 116 after the start of cultivation in Example 4 (day 226 after the start of cultivation in Examples 1-3) were collected, and their weight, total length, total height, and body fatness were measured. Body fatness was calculated using the following formula. The average values ​​of the five collected amago trout (Example) and the average values ​​of five amago trout sold as adult fish at the trout farm (Reference Example) were calculated. The measurement results are shown in Table 1. From the results in Table 1, it was found that the amago trout in Example were of equal or greater size and body fatness than those in the Reference Example. (Body Fatness) = {(Weight) / (Total Length)} ３} × 10 ５

[0057]

[0058] (Sensory Evaluation) The amago trout that underwent the above-mentioned body measurements were grilled with salt and tasted by nine panelists. They evaluated the taste, aroma, and texture on a five-point scale, and the average values ​​were calculated. The evaluation results are shown in Table 2. From the results in Table 2, the amago trout in the example were comparable to the reference example, especially in terms of aroma and taste.

[0059]

[0060] (Discussion) The survival rate of Amago trout farmed using the aquaculture method (aquaculture system) according to this embodiment tended to be higher than that of Comparative Example 1, which used a conventional nitrification-denitrification tank. This result is thought to be because the water in which the Amago trout grew was sufficiently purified by the algae. In other words, the algae in the algal solution are thought to have a sufficient water purification function. Furthermore, this result shows that salmonid fish can be grown for a long period of time even at relatively high concentrations of algae as in this embodiment.

[0061] Furthermore, the size and plumpness of the amago trout farmed using the farming method (farming system) according to this embodiment were equivalent to or better than those of regular amago trout, and their flavor was also comparable to that of regular amago trout. From these results, it can be considered that the presence of algae in the farming tank had a positive effect on the growth of the amago trout. Specifically, it is thought that the algae moderately restricted visibility, reducing stress such as territorial disputes; the antimicrobial substances produced by the algae suppressed the growth of pathogenic bacteria and viruses; the antioxidants produced by the algae reduced oxidative stress in the amago trout; the amago trout ingested the algae and absorbed functional substances (DHA, EPA, etc.) contained in the algae; and the algae increased the sliminess of the fish's body surface, suppressing parasites.

[0062] <Example 5> (Algae Preparation Process) The experiment was conducted using an aquaculture system (specifically, the aquaculture system shown in Figure 6) that included a cultivation tank, an algae tank, a water tank, and a nitrification / denitrification tank. In this example, seven ZOOX Next Generation Bio Media L size (manufactured by MMC Planning Co., Ltd.; hereinafter also referred to as "ZOOX") were placed inside the microbial nitrification / denitrification tank (biological filtration device). Furthermore, as a physical filtration device, a polyester wool mat was installed at the outlet of the discharge pipe 50 on the algae tank side to remove debris and leftover feed. In this way, algae cultivation, physical filtration, and biological filtration were combined.

[0063] First, the algae to be used were prepared. The on / off valve in the piping between the cultivation tank and the algae tank was closed, and the pump for introducing the algae was stopped. The algae (green algae (collected in Nagahama City; same as in Example 3)) were cultured in the algae tank, and the volume was 197.5 × 10⁻⁶. ４ Algae were prepared for cell / mL input. The water used for this experiment was purified tap water.

[0064] Next, the on-off valve located in the piping between the aquaculture tank and the algae tank was opened, and the algae introduction pump was started to introduce the algae into the aquaculture tank. After introduction, the amount of algae solution in the aquaculture tank was 1000 L.

[0065] (Cultivation Process and Purification Process) In this experiment, the on / off valve installed in the piping between the cultivation tank and the algae tank was kept open at all times, the algae introduction pump was kept running at all times, and the algae solution was continuously circulated between the cultivation tank and the algae tank (i.e., the algae concentration was the same in both the cultivation tank and the algae tank). At this time, the circulation rate was approximately 10 to 25 L / min.

[0066] Forty-five rainbow trout, each with an average weight of 14.1g, purchased from a trout farm, were placed in a rearing tank to begin farming. During the rearing period, the temperature of the algal solution was controlled to 15.0-16.0°C, the dissolved oxygen concentration to 8mg / L or higher, and the pH to 5.2-7.1. The concentration of algae in the algal solution was also measured periodically during the rearing period. Furthermore, the number of surviving rainbow trout was recorded. On the 51st day after the start of farming, all of the ZOOX biological filter material was removed from the biological filtration system. In other words, from the 51st day onward, algal cultivation and physical filtration were combined. On the 52nd day after the start of farming, 11 kg of oyster shells were added to the nitrification-denitrification tank (after the ZOOX had been removed) to adjust the pH. Furthermore, on the 71st day after the start of cultivation, in order to replenish the water evaporated during cultivation, the on / off valve installed in the piping between the cultivation tank and the water tank was opened, and 400L of purified tap water was added. Cultivation continued until the 159th day after the start of cultivation. Feeding was carried out at a frequency of 4 to 5 days out of 7 days. The daily feeding rate (amount of feed (g) relative to total fish weight (g)) was approximately 3.0 mass% from day 1 to day 102, and approximately 2.0 mass% from day 106 to day 159. LEDs and air pumps were installed in the algae tank, and by operating, adjusting, and / or stopping them respectively, algae cultivation was carried out continuously.

[0067] <Comparative Example 2> The same system as in Comparative Example 1 (a system combining physical and biological filtration) was used for the experiment. Algae were not used in this comparative example. 90 rainbow trout with an average weight of 15.7 g, purchased from a trout farm, were placed in a tank to begin cultivation. During the cultivation period, the temperature of the algae solution was controlled to 15.0-16.0°C, the dissolved oxygen concentration to 8 mg / L or higher, and the pH to 5.5-7.7. Cultivation continued until the 199th day after the start of cultivation. Feeding was not performed on the first and second days, and began on the third day, at a frequency of 4-5 days out of 7. The daily feeding rate (amount of feed (g) relative to total fish body weight (g)) was 0.7 mass% on day 3, approximately 2.0 mass% from day 6 to day 38, an average of 2.6 mass% from day 41 to day 42, an average of 3.2 mass% from day 43 to day 170, and an average of 2.0 mass% from day 171 to day 199.

[0068] <Evaluation Results> (Algae concentration in algae solution) Figure 9 shows the results of the algae concentration in the algae solution in Example 5. In Example 5, the algae concentration in the cultivation tank was 145 × 10 during the cultivation period. ４ ~4875 x 10 ４ The cell count was per mL.

[0069] (Ammonia Concentration) Figure 10 shows the results of measuring the ammonia concentration in the aquaculture tanks during the cultivation period in Example 5 and Comparative Example 2. The ammonia concentration in Example 5 was 0.11 to 11.9 mg / L during the cultivation period. The ammonia concentration in Comparative Example 2 was 0.1 to 1.7 mg / L during the cultivation period.

[0070] (Survival Rate) Figure 11 shows the survival rate results for rainbow trout in Example 5 and Comparative Example 2. From the results of Example 5, the algal concentration in the algal solution was 1.0 × 10⁻⁶. ４ Under conditions with a cell / mL or higher, rainbow trout could be grown with a high survival rate for a long period of 159 days from the start of cultivation. Furthermore, surprisingly, in Example 5, the survival rate tended to be higher than in Comparative Example 2, which used a conventional nitrification-denitrification tank.

[0071] (Fish Body Measurement and eFCR Value) All rainbow trout that survived until the end of cultivation in Example 5 and Comparative Example 2 were collected, their body weight was measured, and the average value was calculated. Furthermore, the amount of feed per unit of increased fish body weight (eFCR value) was calculated. The results are shown in Table 3. From the results in Table 3, it was found that the eFCR value of the example was lower than that of the comparative example, indicating that weight gain could be achieved more efficiently.

[0072]

[0073] 10: Aquaculture system, 20: Aquaculture tank, 22: Algae solution, 24: Fish, 30: Algae tank, 32: Algae for input, 40: Algae introduction pipe, 42: Algae introduction pump, 44: Algae introduction on / off valve, 50: Discharge pipe, 60: Water tank, 62: Water for input, 70: Water introduction pipe, 72: Water introduction pump, 74: Water introduction on / off valve, 80: Nitrification / denitrification tank, 82: Nitrification / denitrification filter, 90: Connecting pipe

Claims

1. The concentration of algae is 1.0 × 10 ４ A method of aquaculture, comprising a cultivation step of growing salmonid fish in an algal solution of a concentration of cells / mL or higher.

2. The above concentration is 5000 × 10 ４ The aquaculture method according to claim 1, wherein the amount is less than or equal to the number of cells per mL.

3. The cultivation method according to claim 1, wherein the algae is at least one selected from the group consisting of cyanobacteria, glaucophytes, red algae, green algae, cryptophytes, haptophytes, heterokonts, dinoflagellates, chlorarachnion algae, and Euglena algae.

4. The aquaculture method according to claim 1, wherein the fish is at least one species selected from the group consisting of cherry salmon, amago trout, Taiwanese trout, Biwa trout, rainbow trout, kokanee salmon (sockeye salmon), kunimasu salmon, chinook salmon, salmon, coho salmon, pink salmon, Apache trout, Mexican golden trout, throat-scarlet trout, and gira trout.

5. The aquaculture method according to claim 1, further comprising a purification step for purifying water.

6. The aquaculture method according to claim 5, wherein the purification step utilizes algal cultivation, physical filtration, or biological filtration.

7. The aquaculture method according to claim 5, wherein the purification step utilizes algal cultivation.

8. The aquaculture method according to claim 1, wherein it is a closed-circulation system.

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