Method for rearing shellfish

Abstract

The present invention addresses the problem of providing a rearing method that is capable of maintaining and, further, increasing the meat content of adult shellfish. The present invention further addresses the problem of providing a rearing method that is capable of improving heating yield of adult shellfish. The present invention further addresses the problem of providing a rearing method that is capable of improving the appearance, taste, and flavor of adult shellfish.　One embodiment of the present invention is a method for rearing shellfish, said rearing method comprising: an algae preparation step for preparing an algae solution that has an algae concentration of 0.3×106 cells / mL or more; and a shellfish immersion step for immersing the shellfish in the algae solution. Furthermore, in the rearing method, the shellfish is adult shellfish.

Description

Methods for raising shellfish

[0001] The present invention relates to a method for raising shellfish.

[0002] In order to grow collected shellfish to a marketable size, they need to be cultivated over a long period of time. Long-term cultivation is costly, and there is a need for methods to grow shellfish in a shorter period of time. Patent Document 1 discloses a method for cultivating juvenile abalone that promotes the growth of juvenile abalone, making them marketable in a short period of time.

[0003] Japanese Patent Publication No. 2007-190014

[0004] In recent years, there has been a growing demand for high-value shellfish with more meat than usual as export products. However, cultivating such shellfish requires a longer period of time and is costly. Furthermore, conventional sea and river aquaculture has been hampered by the fact that, due to global warming and ocean purification, it is sometimes impossible to obtain shellfish with good meat content even with the time and cost invested. In addition, with sea-farmed shellfish, it is necessary to remove pathogens and viruses from the shellfish after harvesting and to adjust the time until shipment, but during this time, the shellfish may lose meat, die, or their taste may deteriorate.

[0005] This invention has been made in view of these circumstances, and its first objective is to provide a rearing method that can maintain and even increase the amount of meat in adult oysters.

[0006] Furthermore, one of the evaluation criteria for aquatic products is the heat yield. The second objective of this invention is to provide a rearing method that can improve the heat yield of adult shellfish.

[0007] A third objective of this invention is to provide a rearing method that can improve or enhance the appearance, taste, and aroma of adult shellfish.

[0008] After diligent research by the inventors, they discovered that the above problems could be solved by using algae, and thus completed the present invention.

[0009] The present invention provides the following: [1] A method for raising shellfish, wherein the algal concentration is 0.3 × 10 ６A method for raising shellfish, comprising: an algae preparation step of preparing an algae solution of cells / mL or more; and a shellfish immersion step of immersing the shellfish in the algae solution, wherein the shellfish are adult shellfish. [2] The method for raising shellfish further comprises an algae addition step after the shellfish immersion step, wherein the algae addition step, after the start of shellfish immersion, brings the algae concentration of the algae solution to 0.3 × 10 ６ If the value is less than cells / mL, then 0.3 × 10 ６ The rearing method described in [1], which is a step of adding algae so that the cell / mL is greater than or equal to [3] The rearing method further comprises a shellfish preparation step before the shellfish immersion step, wherein the shellfish preparation step involves preparing the shellfish so that the algae concentration is 1.0 × 10 ４ A rearing method according to [1] or [2], wherein the step is to collect from an environment with a cell / mL or less. [4] A rearing method according to any one of [1] to [3], wherein the rearing method further comprises a shellfish preparation step before the shellfish immersion step, wherein the shellfish preparation step is a step of obtaining natural shellfish that have been growing in the sea, tidal flats, estuaries or rivers, or farmed shellfish that have been growing in a farm. [5] A rearing method according to any one of [1] to [4], wherein the rearing method further comprises a shellfish retrieval step after the shellfish immersion step, wherein the shellfish retrieval step is a step of retrieving the shellfish from 1 day to 10 days after the start of shellfish immersion. [6] A rearing method according to any one of [1] to [4], wherein the rearing method further comprises a shellfish retrieval step after the shellfish immersion step, wherein the algae concentration from the start of shellfish immersion to shellfish retrieval is 0.3 × 10 ６ The rearing method according to any one of [1] to [5], wherein the time during which the cell / mL is less than 4 days continuously. [7] The rearing method according to any one of [1] to [6], wherein the algae culture tank for culturing the algae used in the algae solution and the immersion tank for immersing the shellfish in the algae solution in the shellfish immersion step are separate tanks. [8] The rearing method according to any one of [1] to [7], wherein the shellfish are oysters.

[0010] According to the present invention, it is possible to provide a rearing method that can maintain and even increase the amount of meat in adult oysters. According to the present invention, it is possible to provide a rearing method that can improve the heating yield of adult oysters. According to the present invention, it is possible to provide a rearing method that can improve the appearance, taste, and aroma of adult oysters.

[0011] Figure 1 is a diagram showing an overview of the rearing system according to the first embodiment of the present invention. Figure 2 is a diagram showing an overview of the rearing system according to the second embodiment of the present invention. Figure 3 is a diagram showing the measurement results of oyster meat content and algae concentration in Example 1. Figure 4 is a diagram showing the measurement results of oyster meat content and algae concentration in Example 2. Figure 5 is a diagram showing the measurement results of oyster meat content and algae concentration in Example 3. Figure 6 is a diagram showing the measurement results of oyster meat content and algae concentration in Example 4. Figure 7 is a diagram showing the measurement results of oyster meat content and algae concentration in Example 5.

[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 phrase "X to Y" means that it is greater than or equal to X and less than or equal to Y. In this specification, for example, the phrase "within the range between any two of the given numerical values" means that, if the given numerical values ​​are A and B (A < B), it is greater than or equal to A and less than or equal to B.

[0014] 1. Rearing Method The rearing method for shellfish according to this embodiment comprises an algae preparation step and a shellfish immersion step. Furthermore, it may also include a shellfish preparation step, an algae addition step, a sterilization step, a shellfish purification step, a water purification step, and an evaluation step. In addition, the rearing method according to this embodiment is typically a closed-loop system.

[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 directly adjusted in the immersion tank used in the subsequent shellfish immersion process, or may be adjusted by introducing an appropriate amount of algae from an algae culture tank provided separately from the immersion tank into the immersion tank. Furthermore, the algae to be used may be purchased or collected algae, or may be obtained by culturing these algae. Note that the solvent (water) of the algae solution according to this embodiment can be appropriately selected according to the shellfish to be reared. For example, seawater, fresh water, or brackish water can be used, and typically seawater can be used.

[0016] The algae according to this embodiment can be appropriately selected according to the shellfish to be reared. The algae according to this embodiment is preferably at least one selected from green algae, diatoms, brown algae, dinoflagellates, haptophytes, Chlorarachniophytes, red algae, conjugating algae, Euglena algae, and cyanobacteria. The type of algae can be algae that the target shellfish can eat and / or algae that can grow at a temperature at which the shellfish can grow.

[0017] The algae concentration in the algae solution according to this embodiment is, for example, 0.2×10 ６ cells / mL or more, 0.3×10 ６ cells / mL or more, 0.5×10 ６ cells / mL or more, 0.8×10 ６ cells / mL or more, 0.8×10 ６ cells / mL more than, 0.9×10 ６ cells / mL or more, 1.0×10 ６ cells / mL or more, 1.3×10 ６ cells / mL or more, 1.4×10 ６ cells / mL or more, or 1.5×10 ６ cells / mL or more. Also, the algae concentration of the algae solution is preferably 0.3×10 ６ cells / mL or more, more preferably 0.5×10 ６ cells / mL or more, still more preferably 0.8×10 ６ cells / mL or more or 0.8×10 ６ cells / mL more than, and even more preferably 0.9×10 ６It is particularly preferable that the cell / mL is greater than 1.0 × 10 ６ It is most preferable that the concentration be 1.0 × 10⁻¹⁶ cells / mL or higher. Furthermore, the upper limit of the algal concentration in the algal solution according to this embodiment is not particularly limited, but for example, 1.0 × 10⁻¹⁶ ９ The concentration can be expressed as cells / mL. The algal concentration in the algal solution is, for example, 0.2 × 10⁻⁶. ６ , 0.3 × 10 ６ , 0.5 × 10 ６ , 0.6 × 10 ６ , 0.8 × 10 ６ , 1.0 × 10 ６ , 1.2 × 10 ６ , 1.4 × 10 ６ , 1.5 × 10 ６ , 2.0 × 10 ６ , 1.0 × 10 ７ , 5.0 × 10 ７ , 1.0 × 10 ８ or 1.0 × 10 ９ The concentration may be cells / mL, or within the range between any two of the values ​​exemplified here. When the algal concentration in the algal solution is above the lower limit, the amount of meat in the shellfish can be maintained or increased, the heating yield can be improved, and the appearance, taste, and aroma of the mature shellfish can be improved.

[0018] 1.2 Shellfish Preparation Process In the shellfish preparation process according to this embodiment, shellfish to be cultivated are collected. Examples of shellfish according to this embodiment include bivalves such as oysters, scallops, clams, cockles, freshwater clams, and pearl oysters, and gastropods such as turban shells, abalone, and whelks. Preferably, the shellfish according to this embodiment is one species selected from the group consisting of oysters, scallops, clams, cockles, freshwater clams, and pearl oysters, and more preferably one species selected from the group consisting of oysters, scallops, and pearl oysters.

[0019] The shellfish according to this embodiment are mature shellfish. In this specification, "mature shellfish" means shellfish that have reached a state suitable for consumption. The mature shellfish according to this embodiment may be wild shellfish that have grown in the sea, tidal flats, estuaries or rivers, or they may be farmed shellfish that have grown in marine or land-based aquaculture farms.

[0020] In this embodiment, the shellfish can be wild shellfish or farmed shellfish (sea surface farming or land-based farming (especially flow-through land-based farming)). In other words, the shellfish preparation step in this embodiment can be a step of obtaining wild shellfish that have been growing in the sea, tidal flats, estuaries or rivers, etc., or farmed shellfish that have been growing in aquaculture farms, etc. The shellfish in this embodiment are preferably collected from natural shellfish growing environments or normal aquaculture environments, specifically, with an algae concentration of 1.0 × 10⁻⁶ ４ It is preferable that the shellfish be collected from an environment with a cell / mL or less concentration. Furthermore, it is preferable that the shellfish have been grown in a natural shellfish growing environment or a normal aquaculture environment for at least three days, preferably one week or more, before the start of the shellfish immersion process described later. Specifically, it is preferable that the algae concentration be 1.0 × 10⁻⁶ for at least three days, preferably one week or more, before the start of the shellfish immersion process described later. ４ It is preferable that the shellfish have been grown in an environment with a cell / mL or less concentration.

[0021] 1.3 Shellfish Immersion Process In the shellfish immersion process according to this embodiment, shellfish are immersed in an algal solution. The immersion of shellfish may be carried out by replacing the rearing water in the immersion tank in which the shellfish are grown with the algal solution, or by putting the shellfish into the algal solution prepared in the immersion tank. In the shellfish immersion process according to this embodiment, the amount of algal solution per individual shellfish is, for example, 30 L or less, preferably 10 L or less, more preferably 7.0 L or less, even more preferably 5.0 L or less, particularly preferably 1.0 L or less, and most preferably 0.5 L or less. In the shellfish immersion process according to this embodiment, the amount of algae solution per individual shellfish may be, for example, 0.1, 0.2, 0.3, 0.5, 0.7, 0.8, 1.0, 1.2, 1.5, 1.7, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 8.0, 9.0, 10, 20, or 30 L, and may be within the range of any two of the values ​​exemplified here. Furthermore, in the shellfish immersion process according to this embodiment, the algae content per individual shellfish is 1.0 × 10 ９ Preferably, the size is larger than 1 cell, 5.0 × 10 ９It is more preferable that the size be greater than 1 cell, 7.0 × 10 ９ It is even more preferable that the organisms be larger than cells. The rearing method according to this embodiment is characterized by immersing shellfish in an algal solution with a higher concentration than the environment in which they normally grow. This makes it possible to increase the amount of meat in the shellfish in a very short period of time.

[0022] Furthermore, the shellfish immersion process according to this embodiment is carried out under natural shellfish growing conditions or normal aquaculture conditions (specifically, when the algae concentration is 1.0 × 10⁻⁶). ４ For shellfish that have been grown in rearing water with a concentration of less than 0.2 cells / mL, the process may be initiated by changing the rearing water in the immersion tank to an algal solution of a predetermined concentration or higher. That is, the shellfish immersion process may be initiated by changing the algal concentration to, for example, 0.2 × 10⁻⁶. ６ Cells / mL or more, 0.3 x 10 ６ Cells / mL or more, 0.5 x 10 ６ Cells / mL or more, 0.6 x 10 ６ Cells / mL or more, 0.7 x 10 ６ Cells / mL or more, 0.8 x 10 ６ Cells / mL or more, 0.9 x 10 ６ Cells / mL or more, 1.0 x 10 ６ Cells / mL or more, 1.1 x 10 ６ Cells / mL or more, 1.2 x 10 ６ Cells / mL or more, 1.3 x 10 ６ Cells / mL or more, 1.4 x 10 ６ Cells / mL or more, or 1.5 × 10⁶ ６ The process may also involve immersion in an algal solution of cells / mL or more. By adjusting the start time of the shellfish immersion process by working backward from the shipping date, the shellfish can be in optimal condition (especially in terms of meat content) at the time of shipping.

[0023] 1.4 Algae Addition Process In the algae addition process according to this embodiment, algae are added after the start of shellfish immersion. The addition of algae may be carried out by directly adding algae (or additional algae solution) to the algae solution in which the shellfish are immersed, or by replacing the algae solution in which the shellfish are immersed with a new algae solution. In the algae addition process according to this embodiment, after a certain period of time has elapsed since the start of shellfish immersion, the algae concentration in the algae solution is, for example, 0.02 × 10⁻⁶. ６Cells / mL < 0.05 × 10 ６ Cells / mL < 0.1 × 10⁻⁶ ６ Cells / mL < 0.2 × 10⁻⁶ ６ Cells / mL < 0.3 × 10 ６ Cells / mL < 0.4 × 10 ６ Cells / mL < 0.5 × 10 ６ Cells / mL < 0.6 × 10 ６ Cells / mL < 0.7 × 10 ６ Cells / mL < 0.8 × 10 ６ Cells / mL < 0.9 × 10 ６ Cells / mL < 1.0 × 10 ６ Cells / mL < 1.5 × 10 ６ Cells / mL < 2.0 × 10 ６ Cells / mL < 3.0 × 10 ６ Cells / mL < 4.0 × 10 ６ Cells / mL less than 5.0 × 10 ６ This can be performed when the cell / mL is less than 1.0 × 10⁻¹⁶. The algae addition step according to this embodiment is preferably 1.0 × 10⁻¹⁶. ６ Less than cells / mL, more preferably 0.8 × 10⁶ ６ Less than cells / mL, more preferably 0.5 × 10⁻⁶ ６ Less than cells / mL, particularly preferably 0.3 × 10⁶ ６ Less than cells / mL, most preferably 0.2 × 10⁻⁶ ６ This can be done when the number of cells / mL is less than 1 / mL.

[0024] The measurement of algal concentration to determine whether to add algae can be performed after a predetermined period has elapsed since the shellfish were immersed. Specifically, it can be performed at 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 1 day, 2 days, 3 days, 4 days, 5 days, 6 days, 7 days, 8 days, 9 days, or 10 days after the start of shellfish immersion, or within the time between any two of the examples given here. The algae addition step according to this embodiment can be performed at 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 12 hours, 1 day, 2 days, 3 days, 4 days, 5 days, 6 days, 7 days, 8 days, 9 days, or 10 days after the start of shellfish immersion, and may also be performed within any two of the times exemplified herein. The algae addition step according to this embodiment is preferably performed between 1 day and 9 days after the start of shellfish immersion, more preferably between 1 day and 3 days, and even more preferably between 1 day and 2 days. In one embodiment, the addition of algae may be performed multiple times or continuously. Specifically, the algae concentration can be measured at regular intervals or continuously. For example, algae may be added every hour starting 4 hours after the start of shellfish immersion, or algae may be added continuously starting 4 hours after the start of immersion.

[0025] The algal concentration in the algal solution after addition is 0.3 × 10⁻⁶. ６ It is preferable that the cell-to-mL ratio be 0.5 × 10⁻⁶ or higher. ６ Cells / mL or more, 0.8 x 10 ６ Cells / mL or more, 0.8 x 10 ６ Cells / mL exceeding 0.9 × 10 ６ Cells / mL or more, 1.0 x 10 ６ Cells / mL or more, 1.3 x 10 ６ Cells / mL or more, 1.4 x 10 ６ Cells / mL or more, or 1.5 × 10⁶ ６ The concentration can be higher than cells / mL. Furthermore, the algal concentration in the algal solution after addition should be 0.5 × 10⁻⁶. ６More preferably, it is at least [X] cells / mL, and 0.8×10 ６ cells / mL or more, or more preferably more than 0.8×10 ６ cells / mL, particularly preferably at least 0.9×10 ６ cells / mL, and most preferably at least 1.0×10 ６ cells / mL. By additionally adding algae after a predetermined period has elapsed since the start of the shellfish immersion, the fullness of the shellfish maintained without weight loss or the increased fullness of the shellfish can be maintained over a longer period. Furthermore, the heating yield is improved, and it becomes possible to improve and enhance the appearance, taste, and aroma of the mature shellfish.

[0026] Also, as another embodiment of the algae addition step, after the start of the shellfish immersion, algae may be appropriately added so as to maintain the algae concentration in the algae solution at a predetermined concentration or higher. The algae concentration in the algae solution is, for example, 0.02×10 ６ cells / mL or more, 0.05×10 ６ cells / mL or more, 0.1×10 ６ cells / mL or more, 0.2×10 ６ cells / mL or more, 0.3×10 ６ cells / mL or more, 0.4×10 ６ cells / mL or more, 0.5×10 ６ cells / mL or more, 0.6×10 ６ cells / mL or more, 0.7×10 ６ cells / mL or more, 0.8×10 ６ cells / mL or more, 0.9×10 ６ cells / mL or more, 1.0×10 ６ cells / mL or more, 1.1×10 ６ cells / mL or more, 1.2×10 ６ cells / mL or more, 1.3×10 ６ cells / mL or more, 1.4×10 ６ cells / mL or more, or 1.5×10 ６The algal concentration can be maintained at a level of cells / mL or higher. Furthermore, even if the algal concentration temporarily falls below a predetermined value, the amount of shellfish meat can be maintained for a longer period by raising the algal concentration to above that predetermined value before a predetermined time has elapsed since the concentration fell below the predetermined value. Therefore, from the start of shellfish immersion to the shellfish recovery process described later, the algal concentration in the algal solution can be maintained at, for example, 0.02 × 10⁻⁶. ６ Cells / mL < 0.05 × 10 ６ Cells / mL < 0.1 × 10⁻⁶ ６ Cells / mL < 0.2 × 10⁻⁶ ６ Cells / mL < 0.3 × 10 ６ Cells / mL < 0.4 × 10 ６ Cells / mL < 0.5 × 10 ６ Cells / mL < 0.6 × 10 ６ Cells / mL < 0.7 × 10 ６ Cells / mL < 0.8 × 10 ６ Cells / mL < 0.9 × 10 ６ Cells / mL or 1.0 × 10 ６ The time during which the cell / mL ratio is less than 4 days can be continuous for less than 3 days, preferably less than 2 days, more preferably less than 1 day, even more preferably less than 12 hours, and particularly preferably less than 6 hours.

[0027] 1.5 Shellfish Recovery Process In the shellfish recovery process according to this embodiment, the shellfish are recovered after one day has elapsed since the start of shellfish immersion. The timing of the shellfish recovery process according to this embodiment is preferably between one day and ten days after the start of shellfish immersion, more preferably between one day and six days, even more preferably between one day and three days, and most preferably between one day and two days. By recovering the shellfish at such timings, it is possible to recover shellfish with increased meat content. Specifically, it is possible to recover shellfish with increased meat content, for example, by 5% by mass or more, preferably 10% by mass or more, and even more preferably 14% by mass or more, compared to the amount at the start of shellfish immersion (100% by mass). In this specification, "meat content of shellfish" refers to the mass of the edible portion of the shellfish, excluding the shell. Furthermore, one embodiment of the present invention includes a sterilization process described later, but normally the shellfish may lose meat during the sterilization process. However, according to this embodiment, the amount of meat in the shellfish can be maintained for at least 10 days from the start of immersion. Therefore, one aspect of the present invention is a method for manufacturing shellfish, or a method for producing shellfish.

[0028] 1.6 Sterilization Process and Shellfish Purification Process In the sterilization process according to this embodiment, the used algae solution used in the immersion tank is sterilized in a sterilization tank or sterilization device. Examples of sterilization according to this embodiment include UV sterilization, ozone sterilization, and chemical sterilization, and UV sterilization is preferred because the installation of the device is simple and post-treatment such as neutralization is unnecessary. The sterilization process according to this embodiment can be carried out by taking out a portion of the algae solution in the immersion tank and sterilizing it. The used algae solution contains excrement such as feces and pseudofeces discharged by shellfish. It may also contain general bacteria, pathogenic bacteria (food poisoning bacteria such as E. coli and Vibrio parahaemolyticus) and viruses (norovirus, etc.) that were present in the individual shellfish.

[0029] Furthermore, in the sterilization process according to this embodiment, algae with bactericidal effects or algae that secrete substances with bactericidal effects can also be used. For example, the microalga Coccomyxa KJ has a virus-bactericidal effect. This is because monogalactosyldiacylglycerol (MGDG), a component contained in the chloroplasts of Coccomyxa KJ, has a bactericidal effect against viruses. In addition, algae such as Spirulina, Chlorella, and Ulva are also said to have a bactericidal effect or a growth inhibitory effect against viruses, either in the algae themselves or in the substances they secrete. Therefore, algae such as Coccomyxa KJ, Spirulina, Chlorella, and Ulva can also be used in this sterilization process. When using these algae, the immersion tank may also serve as the sterilization tank. That is, by using these algae as the algal solution used in the shellfish immersion process and the algae addition process, the sterilization process (and furthermore, the shellfish purification process described later) can be performed in the immersion tank.

[0030] By using the algal solution treated in the sterilization step according to this embodiment again as the algal solution in which shellfish are immersed, the number of pathogenic bacteria in the system is reduced, the amount of pathogenic bacteria and viruses contained in the excrement discharged by the shellfish and within the individual shellfish can be reduced, and consequently the shellfish can be purified (shellfish purification step). As a result, the shellfish collected in the shellfish collection step described later can be safely eaten raw or cooked. In the shellfish purification step, the algal solution may be circulated between the immersion tank and the sterilization tank or sterilization device, or the algal solution in the sterilization tank or the algal solution sterilized by the sterilization device may be added to the immersion tank in a batch manner.

[0031] 1.7 Water Purification Process In the water purification process according to this embodiment, the algal solution in the immersion tank or the used algal solution used in the immersion tank is purified by algae present in the water. The algal solution in the immersion tank and the used algal solution used in the immersion tank contain excrement discharged by shellfish, and as shellfish excrement, nitrogen compounds such as ammonia may be included. In this embodiment, nitrogen compounds are digested during the growth process of the algae. In conventional closed-circulation farming methods, it is necessary to provide a separate water purification tank connected to the immersion tank in addition to the immersion tank as a water purification device, but according to the farming method according to this embodiment, it is not necessary to use a separate water purification tank (for example, a nitrification-denitrification device). Furthermore, since the algae cultured in the water purification process can be used in the above-mentioned algal preparation process, shellfish immersion process and algae addition process, no waste is generated and costs are reduced. In addition, in order to create a cleaner state, water purification devices such as known denitrification-nitrification tanks and filters, and ammonia decomposition devices using electrolysis can also be used in combination.

[0032] 1.8 Evaluation Process In the evaluation process according to this embodiment, the shellfish after collection are evaluated. Conventional methods can be used for evaluation, and specifically, the quality of the shellfish can be confirmed by sensory evaluation by tasting or by measuring the heating yield. Sensory evaluation may be performed either raw or after heating. When measuring the heating yield, the heating method is not particularly limited and can be steamed, grilled, fried, boiled, or heated in a microwave oven, but steaming or heating in a microwave oven is preferred. When steaming, the shellfish can be placed in a steamer that has been brought to a boil and steamed for a predetermined time (for example, 3 minutes). When removing the meat from the shell and heating it in a microwave oven, 10 pieces can be placed in a circle on a plate with even spacing, covered with plastic wrap or the like, and heated at a predetermined wattage for a predetermined time (for example, 1 minute 30 seconds at 600W). When heating shellfish in a microwave oven, a method can be used in which five shellfish with shells are heated at a predetermined wattage for a predetermined time (for example, 5-6 minutes at 500W or 4-5 minutes at 600W). The heating yield for each shellfish can be calculated using the following formula, and the average value of the values ​​between the first and third quartiles from multiple calculation results (for example, n=40) can be used. Formula: {(Mass after heating) / (Mass before heating)} × 100 [Unit: %]

[0033] 2. Rearing System The rearing system for implementing the rearing method according to this embodiment will be described below.

[0034] 2.1 First Embodiment The rearing system 10 according to this embodiment is typically a closed-circulation system. Figure 1 is a diagram showing an overview of the rearing system 10 according to this embodiment. As shown in Figure 1, the rearing system 10 comprises an immersion tank 20 and an algae culture tank 30. An algae solution 22 is prepared in the immersion tank 20, and shellfish 24 are immersed in the algae solution 22. Algae for input 32 are prepared in the algae culture tank 30. The immersion tank 20 and the algae culture tank 30 are connected by an algae introduction pipe 40 and an discharge pipe 50. As shown in Figure 1, it is preferable that the algae culture tank 30 for cultivating the algae for input 32 used in the algae solution 22 and the immersion tank 20 for immersing shellfish 24 in the algae solution 22 in the shellfish immersion process are separate tanks. This makes it possible to prepare an algae solution 22 with a sufficient algae concentration. Furthermore, as in this embodiment, it is preferable to allow water to be circulated between the immersion tank 20 and the algae culture tank 30.

[0035] The algae introduction pipe 40 is equipped with an algae introduction pump 42 and an algae introduction on-off valve 44. The algae introduction on-off valve 44 may be a manually operated on-off valve or an electrically operated on-off valve.

[0036] 2.1.1 Algae Preparation Process In the algae preparation process, an algae solution 22 is prepared. A portion of the algae 32 cultured in the algae culture tank 30 is introduced into the immersion tank 20 by opening the algae introduction valve 44 and starting the algae introduction pump 42. When the algae solution 22 reaches a predetermined algae concentration, the algae introduction valve 44 is closed and the algae introduction pump 42 is stopped.

[0037] 2.1.2 Shellfish Immersion Process Next, the shellfish 24 are immersed in the algal solution 22 in the immersion tank 20. After immersion begins, the temperature, ammonia concentration, and pH of the algal solution 22 can be appropriately set according to the type of shellfish 24. The temperature of the algal solution 22 can be, for example, 10 to 30°C, preferably 15 to 25°C, and more preferably 15 to 20°C. The ammonia concentration of the algal solution 22 can be any range in which the shellfish 24 can grow, preferably 7 ppm or less, more preferably 5 ppm or less, even more preferably 3 ppm or less, and particularly preferably 2 ppm or less. The pH of the algal solution 22 can be any range in which the shellfish 24 can grow, preferably 6.0 to 9.0, and more preferably 7.0 to 8.5. In the case of shellfish 24 that grow in seawater in nature, it is preferable to have a pH similar to that of seawater (for example, 7.3 to 8.2). Furthermore, parameters such as temperature, ammonia concentration, and pH may be controlled to return to the above-mentioned ranges if they deviate from them.

[0038] 2.1.3 Algae Addition Process and Water Purification Process Next, one day after the start of shellfish immersion, a portion of the algae 32 to be added is introduced into the immersion tank 20 by opening the algae introduction valve 44 again and starting the algae introduction pump 42. When the algae solution 22 reaches a predetermined algae concentration, the algae introduction valve 44 is closed and the algae introduction pump 42 is stopped. Alternatively, the algae addition process may be carried out by discharging the algae solution 22 in the immersion tank 20 from the system and then introducing the algae 32 to be added into the immersion tank 20.

[0039] During the algae addition process, a portion of the algae solution 22 may be discharged from the immersion tank 20 through the discharge pipe 50 into the algae culture tank 30. The nitrogen compounds in the discharged used algae solution are digested in the algae culture tank 30 during the algae growth process (water purification process). As shown in Figure 1, the discharge of the algae solution 22 can be performed by overflow by setting the installation position of the discharge pipe 50 on the immersion tank 20 side to the upper limit of the water level in the immersion tank 20. In addition, a check valve can be optionally installed in the discharge pipe 50 to prevent the backflow of the algae 32 to be added from the algae culture tank 30. In addition to overflow, an algae solution discharge pump and an on / off valve for the algae solution discharge may be provided (not shown) to discharge the algae solution 22 at any desired timing.

[0040] 2.1.4 At the end of the shellfish recovery process, shellfish 24 are recovered from the algae solution 22. By recovering the shellfish 24 between 1 and 3 days after the start of shellfish immersion, it is possible to obtain shellfish 24 with increased meat content. Furthermore, by recovering the shellfish 24 at least 6 days after the start of shellfish immersion, it is possible to obtain shellfish 24 with maintained meat content.

[0041] Next, a modified example of the breeding 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.

[0042] 2.2 Second Embodiment (Sterilization Process and Shellfish Purification Process) Figure 2 is a diagram showing an overview of the rearing system 10 according to this embodiment. In the rearing system 10 according to this embodiment, a sterilization tank 60 is provided between the immersion tank 20 and the algae culture tank 30. The sterilization tank 60 can be, for example, a UV sterilization device. The immersion tank 20 and the sterilization tank 60 are connected by a discharge pipe 50. The sterilization tank 60 and the algae culture tank 30 are connected by a connecting pipe 70. In this embodiment, a portion of the algae solution 22 is first introduced into the sterilization tank 60 through the discharge pipe 50. In the sterilization tank 60, general bacteria, pathogenic bacteria (E. coli, Vibrio parahaemolyticus, etc.), and viruses (norovirus, etc.) that may be contained in the introduced used algae solution are sterilized. Subsequently, the sterilized algae solution is introduced into the algae culture tank 30 through the connecting pipe 70. In this embodiment, while cultivating shellfish 24, pathogenic bacteria in the system are reduced, and consequently the shellfish 24 can be purified (shellfish purification process). Alternatively, a sterilization device without a tank may be used as the sterilization tank 60. For example, a sterilization device without a tank may be installed between the discharge pipe 50 and the connecting pipe 70 to sterilize the used algae solution passing through, and the sterilized algae solution may be introduced into the algae culture tank 30. The sterilization device may also be installed in the immersion tank 20 and / or the algae culture tank 30. In this case, the immersion tank 20 and / or the algae culture tank 30 also serve as the sterilization tank 60. When the sterilization device is installed in the immersion tank 20, the algae solution 22 in the immersion tank 20 can be sterilized while the shellfish immersion process is being carried out. When the sterilization device is installed in the algae culture tank 30, the algae 32 for input can be sterilized while algae cultivation is being carried out in the algae culture tank 30.

[0043] 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.

[0044] The following examples were tested using a rearing system (specifically, the rearing system shown in Figure 1) that includes an immersion tank and an algae culture tank. Furthermore, all shellfish were tested at an algae concentration of 1.0 × 10⁻⁶. ４The shellfish used were those grown or cultivated for more than six months in an environment with a cell / mL or less. All of these shellfish were grown or cultivated on the sea surface for more than six months. Generally, in sea surface aquaculture environments, the algal concentration is 1.0 × 10⁻⁶. ４ The cell / mL ratio is less than 1 / mL. Furthermore, all algae were obtained from the Fisheries Research and Education Agency's Fisheries Organism Genetic Resources Conservation Project.

[0045] <Meal Content Test> (Example 1) First, algae were cultured in an algae culture tank. Diatoms (Chaetoceros calcitrans) were used as the algae, and 400 L of artificial seawater (sodium chloride concentration 3.0% by mass) with 45 mg / L of sodium metasilicate nonahydrate added was used as the culture water. At this time, the temperature of the culture water was set to 25°C. The algae concentration was 1.3 × 10⁻⁶ ６ The algae were cultured until the cell count reached 1 / mL, and the entire volume of the algal solution in the culture tank was transferred to the immersion tank. Seventy purchased adult oysters (triploid, origin: Hiroshima Prefecture) were placed in the immersion tank, and immersion was started. The temperature of the algal solution during immersion was maintained at 15-25°C. Ten oysters were harvested every day from the start of immersion, and the average amount of meat inside was measured. The algal concentration was also measured every day from the start of immersion. The results of the measurements of oyster meat inside and algal concentration at this time are shown in Table 1 and Figure 3.

[0046]

[0047] The results in Table 1 and Figure 3 show that the amount of meat in the shellfish increased from 1 day to 3 days after the start of immersion, and in particular, at 1 day and 2 days after immersion, the amount increased by more than 10% by mass compared to the initial immersion level (100% by mass). Furthermore, the amount of meat in the shellfish was maintained up to 6 days after the start of immersion. In addition, when oysters collected from 1 day to 6 days after immersion were tasted raw, no bitterness characteristic of algae was detected, and they were delicious compared to oysters before immersion.

[0048] (Example 2) First, algae were cultured in an algae culture tank. Haptic algae (Isochrysis sp. (Tahiti Isolate)) were used as the algae, and artificial seawater (sodium chloride concentration 3.0% by mass; 400 L) was used as the culture water. At this time, the temperature of the culture water was set to 25°C. The algae concentration was 2.1 × 10⁻⁶ ６ The algae were cultured until the cell count reached 1 / mL, and the entire volume of the algal solution in the algal culture tank was transferred to the immersion tank. Forty purchased adult oysters (triploid, origin: Hiroshima Prefecture) were added to the immersion tank, and immersion was started. The temperature of the algal solution during immersion was maintained at 15-25°C. At 1 day and 2 days after the start of immersion, 1.0 × 10¹⁶ haptophytes were measured. ７ An additional 10 L of algal solution at a rate of cells / mL was added. Ten oysters were harvested every day from the start of immersion, and the average amount of meat inside was measured. The algal concentration was also measured every day from the start of immersion. The results of the oyster meat content and algal concentration measurements are shown in Table 2 and Figure 4.

[0049]

[0050] The results in Table 2 and Figure 4 show that the amount of meat in the shellfish increased from one day to three days after the start of immersion, and in particular, after two days, the amount had increased by more than 10% by mass compared to the initial amount (100% by mass). Furthermore, when the oysters collected from one to three days later were tasted raw, no bitterness characteristic of algae was detected, and they were tastier than the oysters before immersion.

[0051] (Example 3) First, algae were cultured in an algae culture tank. Haptic algae (Isochrysis sp. (Tahiti Isolate)) were used as the algae, and artificial seawater (sodium chloride concentration 3.0% by mass; 320 L) was used as the culture water. At this time, the temperature of the culture water was set to 25°C. The algae concentration was 0.88 × 10⁻⁶. ６The algae were cultured until the cell count reached 1 / mL, and the entire volume of the algae solution in the culture tank was transferred to the immersion tank. 45 purchased adult oysters (triploid, origin: Hiroshima Prefecture) were added to the immersion tank, and immersion was started. The temperature of the algae solution during immersion was maintained at 15-25°C. After one day from the start of immersion, it was visually confirmed that almost no algae remained in the algae solution in the immersion tank. Therefore, after one day from the start of immersion, the entire volume of the algae solution in the immersion tank was drained, and the algae concentration was 0.88 × 10⁶. ６ The algal solution was replaced by introducing 320 L of fresh algal solution with a cell / mL concentration. Fifteen oysters were harvested daily from the start of immersion, and the average amount of meat was measured. The algal concentration was also measured daily from the start of immersion. The results of the oyster meat content and algal concentration measurements are shown in Table 3 and Figure 5 (the values ​​in parentheses for algal concentration are the results of visual evaluation).

[0052]

[0053] Table 3 and Figure 5 show that the amount of meat in the shellfish increased from one day to three days after the start of immersion, and in particular, at one and two days after immersion, the amount increased by more than 10% by mass compared to the initial amount (100% by mass). Furthermore, when oysters collected from one to three days after immersion were tasted raw, no bitterness characteristic of algae was detected, and they were tastier than oysters before immersion.

[0054] (Example 4) Using haptophytes (Pavlova sp.) as the algae, the algal concentration at the start of immersion and when replacing the algal solution one day after the start of immersion was 0.89 × 10⁻⁶. ６ The test was carried out in the same manner as in Example 3, except that the cell / mL ratio was used. The results of measuring the oyster meat content and algae concentration at this time are shown in Table 4 and Figure 6 (the values ​​in parentheses for algae concentration are the results of visual evaluation).

[0055]

[0056] Table 4 and Figure 6 show that the amount of meat in the shellfish increased from one day to three days after the start of immersion, and in all cases, it increased by more than 10% by mass compared to the start of immersion (100% by mass). Furthermore, when the oysters collected from one to three days after immersion were tasted raw, no bitterness characteristic of algae was detected, and they were tastier than the oysters before immersion.

[0057] (Example 5) Diatoms (Chaetoceros calcitrans) were used as the algae, and the rearing water was artificial seawater (sodium chloride concentration 3.0% by mass) with 45 mg / L of sodium metasilicate nonahydrate added. The algal concentration at the start of immersion and when replacing the algal solution after 1 day from the start of immersion was 0.97 × 10⁻⁶. ６ The test was carried out in the same manner as in Example 3, except that the cell / mL ratio was used. The results of measuring the oyster meat content and algae concentration at this time are shown in Table 5 and Figure 7 (the values ​​in parentheses for algae concentration are the results of visual evaluation).

[0058]

[0059] The results in Table 5 and Figure 7 show that the amount of meat in the shellfish increased from one day to three days after the start of immersion, and especially at two and three days, the amount increased by more than 10% by mass compared to the initial immersion level (100% by mass). Furthermore, when oysters collected from one to three days later were tasted raw, no bitterness characteristic of algae was detected, and they were tastier than the oysters before immersion.

[0060] <Heating Yield Test> (Example 6) First, algae were cultured in an algae culture tank. Haptic algae (Isochrysis sp. (Tahiti Isolate)) were used as the algae, and artificial seawater (sodium chloride concentration 3.0% by mass; 320 L) was used as the culture water. At this time, the temperature of the culture water was set to 25°C. The algae concentration was 3.55 × 10⁻⁶ ６The algae were cultured until the cell count reached 5.0 × 10⁻¹⁰. The entire volume of the algal solution in the culture tank was transferred to the immersion tank, and the temperature of the algal solution was adjusted to 15-20°C using a chiller. 120 purchased adult oysters (triploid, origin: Hiroshima Prefecture) were placed in the immersion tank, and the immersion process began. The temperature of the algal solution in the immersion tank was controlled to 15-20°C using the chiller while the oysters were immersed. Four hours after the start of immersion, 5.0 × 10⁻¹⁰ ６ A fresh algal solution at a rate of 6 L / hour was continuously added at a rate of 6 cells / mL. The algal solution was drained via overflow to maintain a constant level of solution in the immersion tank. Two days after the start of immersion, all oysters were collected. At this time, the algal concentration in the immersion tank from the start of immersion until collection was 1.0 × 10⁻⁶. ６ The cell-to-mL ratio never fell below a certain level.

[0061] (Comparative Example 1) Artificial seawater (sodium chloride concentration 3.0% by mass; 320 L) was introduced into an immersion tank, and 120 purchased adult oysters (triploid, origin: Hiroshima Prefecture) were added to start the immersion process. After two days from the start of immersion, all of the oysters were collected.

[0062] (Reference Example 1) 120 adult oysters (triploid, origin: Hiroshima Prefecture) were purchased and immersed in artificial seawater (sodium chloride concentration 3.0% by mass; 320 L) for about 1 hour, and the entire quantity was recovered.

[0063] (Measurement of heating yield) For each of the oysters collected in Example 6, Comparative Example 1, and Reference Example 1, 40 oysters were randomly selected, the meat was removed, and the moisture adhering to the surface was wiped off with a paper towel. The amount of meat inside the oysters after wiping off the moisture (mass before heating) was measured and recorded. Ten of the oysters after the mass measurement were arranged in a circle on a plate with even spacing, covered with plastic wrap, and heated in a microwave oven (600W, 1 minute 30 seconds). The oysters after heating were collected, the moisture adhering to the surface was wiped off with a paper towel, and the mass (mass after heating) was measured and recorded.

[0064] The heating yield of each oyster was calculated using the following formula: {(mass after heating) / (mass before heating)} × 100 [unit: %]. The average value of the values ​​between the first and third quartiles among the calculation results (n=40) for Example 6, Comparative Example 1, and Reference Example 1 was taken as the heating yield. Specifically, for the calculation results for Example 6, Comparative Example 1, and Reference Example 1, the bottom 25% (10 oysters) and top 25% (10 oysters) of the heating yield calculation results were excluded as outliers, and the average value of the remaining 50% (20 oysters) was taken as the heating yield for each example. As a result, the heating yields for Example 6, Comparative Example 1, and Reference Example 1 were 77.3%, 68.1%, and 73.9%, respectively. From these results, it was found that oysters immersed in the algae solution for a predetermined period showed improved heating yield.

[0065] <Sensory Test> (Example 7) First, algae were cultured in an algae culture tank. Haptic algae (Isochrysis sp. (Tahiti Isolate)) were used as the algae, and artificial seawater (sodium chloride concentration 3.0% by mass; 320 L) was used as the culture water. At this time, the temperature of the culture water was set to 25°C. The algae concentration was 2.85 × 10⁻⁶ ６ The algae were cultured until the cell count reached 1 / mL, and the entire volume of the algal solution in the culture tank was transferred to the immersion tank. The temperature of the algal solution was adjusted to 15-20°C using a chiller. 120 purchased adult oysters (triploid, origin: Hiroshima Prefecture) were placed in the immersion tank, and the immersion process began. The temperature of the algal solution in the immersion tank was controlled to 15-20°C using the chiller while the oysters were immersed. Four hours after the start of immersion, the readings were 2.73 × 10⁻⁶. ６ A fresh algal solution at a rate of 6 L / hour was added, with a cell / mL concentration. The algal solution was drained via overflow to maintain a constant level of solution in the immersion tank. After two days from the start of immersion, all oysters were collected. At this point, the algal concentration in the solution in the immersion tank from the start of immersion until collection was 1.0 × 10⁻⁶. ６ The cell-to-mL ratio never fell below a certain level.

[0066] (Comparative Example 2) Artificial seawater (sodium chloride concentration 3.0% by mass; 320 L) was introduced into an immersion tank, and 120 purchased adult oysters (triploid, origin: Hiroshima Prefecture) were added to start the immersion process. After two days from the start of immersion, all of the oysters were collected.

[0067] (Sensory Evaluation (Raw Oysters)) For the oysters collected in Example 7 and Comparative Example 2, the meat was removed and the moisture adhering to the surface was wiped off with a paper towel. For each oyster, five panelists familiar with oyster production evaluated the following items. The evaluation was conducted as a blind test. ・Appearance The appearance of the oysters was evaluated on a two-point scale of 0 or 1 for three items: "large," "plump," and "looks delicious." The sum of the evaluation results from each panelist was calculated. The evaluation results are shown in Table 6. ・Tasting The oysters were tasted and evaluated on a five-point scale of 0 to 4 for three items: "umami," "saltiness," and "aroma." The average of the evaluation results from each panelist was calculated. The evaluation results are shown in Table 6.

[0068]

[0069] The results in Table 6 show that oysters immersed in the algal solution for a specified period had improved appearance compared to oysters grown in seawater. Furthermore, oysters immersed in the algal solution for a specified period had less saltiness and improved umami and aroma compared to oysters grown in seawater.

[0070] (Sensory Evaluation (Heated Oysters)) For the oysters collected in Example 7 and Comparative Example 2, the meat was removed and any moisture adhering to the surface was wiped off with a paper towel. Next, each oyster was arranged on aluminum foil so that they did not overlap, with an opening at the top of the aluminum foil so that steam could directly reach it. The aluminum foil with the oysters was placed on a steaming plate in a boiling steamer, the lid was closed, and it was heated on a gas stove for 3 minutes. For each oyster, eight panelists familiar with oyster production evaluated the following items. The evaluation was conducted in a blind test. ・Appearance The appearance of the oysters was evaluated on a two-point scale of 0 or 1 for three items: "large," "plump," and "looks delicious." The total score of each panelist's evaluation was calculated. The evaluation results are shown in Table 7.

[0071]

[0072] The results in Table 7 show that oysters immersed in the algal solution for a predetermined period exhibited improved appearance even after heating compared to oysters grown in seawater.

[0073] <Component Analysis Test> (Example 8) First, algae were cultured in an algae culture tank. Haptic algae (Isochrysis sp. (Tahiti Isolate)) were used as the algae, and artificial seawater (conductivity 2.6%; 500 L) was used as the culture water. At this time, the temperature of the culture water was set to 25°C. The algae concentration was 1.32 × 10⁻⁶ ６ The algae were cultured until the cell count reached 1 / mL, and the entire volume of the algal solution in the culture tank was transferred to the immersion tank. The temperature of the algal solution was then adjusted to 15-20°C using a chiller. 400 purchased adult oysters (triploid, origin: Hyogo Prefecture) were placed in the immersion tank, and the immersion process began. The temperature of the algal solution in the immersion tank was controlled to 15-20°C using the chiller while the oysters were immersed.

[0074] At 1 day, 3 days, 7 days, and 9 days after the start of immersion, the entire amount of algae solution in the immersion tank was drained, and a new algae solution was reintroduced to replace the old one. In addition, 70 oysters were harvested every two days from the start of immersion. Furthermore, the algae concentration was measured at predetermined intervals from the start of immersion (including before and after replacement of the algae solution if it was replaced). The results of the algae concentration measurements are shown in Table 8.

[0075]

[0076] (Comparative Example 3) Artificial seawater (sodium chloride concentration 3.0% by mass; 700 L) was introduced into an immersion tank, and 400 purchased adult oysters (triploid, origin: Hyogo Prefecture) were added to start the immersion process. At 1 day, 3 days, 7 days, and 9 days after the start of immersion, the entire amount of artificial seawater in the immersion tank was drained, and fresh artificial seawater was reintroduced to replace the artificial seawater. The amount of artificial seawater added at this time was 530 L at 1 day, 530 L at 3 days, 400 L at 7 days, and 400 L at 9 days. In addition, 70 oysters were harvested at the start of immersion and every two days thereafter.

[0077] (Component Analysis) For Example 8 and Comparative Example 3, component analysis of taste-related components was performed on oysters at the start of immersion, 2 days after the start of immersion, and 10 days after the start of immersion. The measurement results are shown in Table 9.

[0078]

[0079] The results in Table 9 show that oysters immersed in artificial seawater for a predetermined period (Comparative Example 3) tended to maintain or decrease in the content of taste-related components compared to the start of immersion. On the other hand, oysters immersed in an algal solution for two days (Example 8) showed increased content of carbohydrates, lipids, glycogen, free taurine, total leucine, total isoleucine, total valine, and octadecatetraenoic acid compared to Comparative Example 3. Furthermore, oysters immersed in an algal solution for ten days (Example 8) showed increased content of carbohydrates, lipids, glycogen, total valine, total serine, free glutamic acid, and octadecatetraenoic acid compared to Comparative Example 3. Therefore, oysters immersed in an algal solution tended to have increased content of taste-related components.

[0080] 10 Rearing system 20 Immersion tank 22 Algae solution 24 Shellfish 30 Algae culture tank 32 Algae for input 40 Algae introduction pipe 42 Algae introduction pump 44 Algae introduction on / off valve 50 Discharge pipe 60 Sterilization tank 70 Connecting pipe

Claims

1. A method for raising shellfish, wherein the algal concentration is 0.3 × 10 ６ A method for raising shellfish, comprising: an algal preparation step of preparing an algal solution of cells / mL or more; and a shellfish immersion step of immersing the shellfish in the algal solution, wherein the shellfish are adult shellfish.

2. The above rearing method further includes an algae addition step after the shellfish immersion step, wherein the algae addition step occurs after the start of shellfish immersion when the algae concentration of the algae solution is 0.3 × 10 ６ If the value is less than cells / mL, then 0.3 × 10 ６ The method of rearing according to claim 1, comprising the step of adding algae so that the cell / mL ratio is greater than or equal to 1.

3. The above rearing method further includes a shellfish preparation step before the shellfish immersion step, wherein the shellfish preparation step involves preparing the shellfish in an algae concentration of 1.0 × 10⁻⁶ ４ The rearing method according to claim 1, which includes the step of collecting cells from an environment with a cell / mL or less.

4. The method of raising shellfish according to claim 1, wherein the method of raising shellfish further comprises a shellfish preparation step before the shellfish immersion step, and the shellfish preparation step is a step of obtaining wild shellfish that have been growing in the sea, tidal flats, estuaries or rivers, or farmed shellfish that have been growing in a farm.

5. The method of rearing shellfish according to claim 1, wherein the rearing method further comprises a shellfish retrieval step after the shellfish immersion step, and the shellfish retrieval step is a step of retrieving the shellfish between 1 day and 10 days after the start of shellfish immersion.

6. The above rearing method further includes a shellfish retrieval step after the shellfish immersion step, and the algae concentration from the start of shellfish immersion to shellfish retrieval is 0.3 × 10 ６ The rearing method according to claim 1, wherein the time during which the cell / mL ratio is less than 4 days continuously.

7. The rearing method according to claim 1, wherein the algae culture tank for cultivating the algae to be used in the algae solution and the immersion tank for immersing the shellfish in the algae solution in the shellfish immersion step are each different tanks.

8. The method of rearing according to claim 1, wherein the shellfish is an oyster.

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