Water for raising larvae, a method for raising larvae using the water, a larval fish farming apparatus, a method for producing water for raising larvae, and a manufacturing apparatus.

Abstract

To solve a problem that larval fishes are captured by the surface tension of water in a stage that the larval fishes are floated on a water level, and perished because the larval fishes cannot return into the water once again, thus causing the lowering of a yield of the larval fishes, that is, the largest problem for deciding whether or not feeding becomes successful in the breeding of the larval fishes.SOLUTION: By adding ultrafine bubbles of hydrogen, oxygen or air into water which is raised in a dissolved oxygen concentration, and feeding ten-days old or younger larval fishes by using feeding water which is lowered in surface tension, a floating extinction rate of the larval fishes is reduced, and a survival rate and a fish bladder opening rate can be raised, thus improving a yield of the breeding.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a surface tension-reducing culture water for the production of fish and shellfish seedlings and the stable production of fry, a culture method, a culture apparatus, a method for producing the culture water, and a production apparatus therefor.

Background Art

[0002] In applications related to the culture of fry and juveniles, there are many applications related to feed and culture tanks, but there are few radical improvement applications related to the properties of the water in the culture tank. There were about two applications related to preventing fry from being trapped by the surface tension of water, which is closely related to the present application. Other applications were for the sea surface aeration culture method.

[0003] Patent Document 1 aims to provide a method capable of raising fry without causing deterioration of the water quality in the breeding tank and without inhibiting the normal growth of the fry. The solution is characterized by comprising a wave generating device for forming waves on the water surface of the tank. The principle is to prevent the so-called "floating death" in which fry are trapped on the water surface by surface tension and become unable to swim and die due to the generation of waves. In this application, the up-and-down vibration by small waves promotes the release of fry into the water, but it does not reduce the surface tension of the water.

[0004] Patent Document 2 aims to provide a method for improving the survival rate of fry and juveniles by providing an appropriate turbulent flow intensity in the culture water without damaging the fish body of the fry. The solution is to generate turbulent flow in the culture water containing fry and feed such that the turbulent energy dissipation rate is in the range of 1.0×10 -8 ~1.0×10 -7 m 2 s -3 to prevent fry trapped by surface tension with turbulent energy. In this application, by adjusting the turbulent flow intensity to affect the surface tension, the release of fry into the water is promoted, but it does not reduce the surface tension itself.

[0005] Patent Document 3 describes a sea surface aeration aquaculture method characterized by blowing air into seawater from an air supply pipe installed directly below the location of the cultivated organisms on the sea surface where fish, shellfish, seaweed, etc. are being cultivated, and is not the method combining ultrafine bubbles and aeration described in this application. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2006-325527 [Patent Document 2] Japanese Patent Publication No. 2006-325458 [Patent Document 3] Japanese Patent Application Publication No. 02-200132 [Patent Document 4] Patent No. 6040345 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Fish farming is usually understood as raising fish from fertilized eggs to adulthood. However, the causes of death in the larval stage (from immediately after hatching to about one month later, when they are less than 2 cm in size) are completely different from those in the stage after they reach 2 cm in size. This is because larvae belong to the plankton family, are transparent in appearance, and are so fragile that they die from mere contact with something. However, once all fish species complete metamorphosis and become juveniles, they take on the same form as adults, making them easily identifiable and easier to transport and raise. Therefore, the aquaculture industry is divided into seedling producers and aquaculture businesses that purchase and raise seedlings, and for those in the industry, farming larvae and juveniles is considered to be completely different types of aquaculture.

[0008] In larval fish farming, the biggest challenge determining success is that when larvae surface, they are trapped by surface tension and unable to return to the water, leading to death. Alternatively, they may die due to failure to open their swim bladder properly, resulting in bone deformation and death. This reduces the larval yield. These challenges are not a concern for fish beyond the juvenile stage.

[0009] Ultrafine bubbles of high density hydrogen and oxygen have the function of lowering surface tension, and are expected to eliminate causes of death that occur as larvae grow, such as being caught at the water surface or failing to open their swim bladder. However, ultrafine bubbles (nanobubbles) containing hydrogen and oxygen, with a size of several hundred nanometers, displace dissolved oxygen in the water, creating an oxygen-depleted state, making it impossible for larvae and young fish to breathe and survive. However, although ultrafine bubbles float in the water for a long time after being generated and lower surface tension, they do not displace newly injected dissolved oxygen.

[0010] Furthermore, for larvae that are less than 2 cm in size up to 20 days after hatching, fine bubbles (microbubbles) measuring several hundred micrometers may interfere with the larvae's dive into the water and could even lead to them rising to the surface and dying. [Means for solving the problem]

[0011] This invention is intended to solve the above-mentioned problems and involves cultivating larval fish in rearing water with sufficient dissolved oxygen and reduced surface tension.

[0012] First, the rearing water for larvae according to the present invention is at least water raw It is characterized by having ultrafine bubbles and a dissolved oxygen concentration of 1.0 mg / L or higher.

[0013] Furthermore, the method for cultivating larvae according to the present invention is characterized by cultivating larvae using the above-mentioned larval rearing water.

[0014] Furthermore, the larval fish farming apparatus according to the present invention is A water tank, to the water tank at least water raw a fine bubble generating part that supplies ultra-fine bubbles, characterized by having an oxygen supply part that supplies oxygen into the water tank.

[0015] Also, a method for producing breeding water for fry according to the present invention is in water at least water raw a step of including ultra-fine bubbles, characterized by having a step of supplying oxygen to the water.

[0016] Also, a production device for breeding water for fry according to the present invention is a water tank, water supply means for supplying water to the water tank, to the water tank at least water raw a fine bubble generating part that supplies ultra-fine bubbles, an oxygen supply part that supplies oxygen into the water tank, characterized by having a breeding water water supply part that can discharge the water in the water tank.

Effect of the Invention

[0017] The present invention can generate ultra-fine bubbles (hereinafter also referred to as "UFB") of hydrogen, oxygen or air with a size less than a micron in water with a dissolved oxygen concentration of a certain level or more, and can generate breeding water for fry that has a high concentration of dissolved oxygen while being low surface tension water.

[0018] That is, the breeding water according to the present invention has a smaller surface tension than ordinary water and a sufficient dissolved oxygen concentration. Therefore, even if the fry come to the water surface, they can return to the water without being captured by the surface tension of the water surface, and the failure of swim bladder inflation can also be avoided. It is possible to achieve breeding with a high survival rate without the fry dying at the fry stage in aquaculture. As a result, the seedling production and aquaculture of fry are stabilized.

[0019] Furthermore, it was found that UFB (Ultra-Fish Bait) stimulates the feeding behavior of larval fish. This is thought to be due to the increased metabolism of the larvae. In other words, with UFB, metabolism is activated, so the larvae heal and become healthier, improving their feeding rate and survival rate. As a result, this leads to improved production efficiency. [Brief explanation of the drawing]

[0020] [Figure 1] This graph shows the effects of air, hydrogen, and oxygen ultrafine bubble water on the number of rotifers consumed by larval fish. [Figure 2] This graph shows the effects of air, hydrogen, and oxygen ultrafine bubble water on the growth of larval fish. [Figure 3] This graph shows the effects of air, hydrogen, and oxygen ultrafine bubble water on the mortality rate of floating creatures. [Figure 4] This graph shows the effects of air, hydrogen, and oxygen ultrafine bubble water on survival rates. [Figure 5] This graph shows the effect of high-density oxygen ultrafine bubble water on the number of rotifers consumed by larval fish. [Figure 6] This graph shows the effect of high-density oxygen ultrafine bubble water on the growth of larval fish. [Figure 7] This graph shows the effect of high-density oxygen ultrafine bubble water on the swim bladder opening rate of larval fish. [Figure 8] This diagram shows the configuration of a fish larval aquaculture apparatus. [Figure 9] This diagram shows the configuration of a water production system for feeding larvae. [Modes for carrying out the invention]

[0021] The following describes the larval rearing water, the method and apparatus for cultivating larvae using the same, and the method and apparatus for producing the larval rearing water according to the present invention, with reference to drawings and examples. The following description illustrates one embodiment and one example, and the present invention is not limited to the following description. The following description may be modified without departing from the spirit of the present invention.

[0022] In this invention, the rearing water for larvae is water used primarily for cultivating the larvae of fish and shellfish, and may be freshwater or seawater. The larvae should be younger than 15 days old, more preferably 13 days old, and most preferably 10 days old or younger. This is because, as they grow and become juveniles, metamorphosis is complete, the number of vertebrae becomes constant, the swim bladder opens, and their body weight becomes more than 1000 times greater than before, allowing them to return to the water on their own without being trapped by the surface tension of the water.

[0023] In this invention, ultrafine bubbles (UFBs) of hydrogen, oxygen, or air refer to bubbles made of hydrogen, oxygen, or air, preferably with a diameter of 1 nm or more and less than 1 μm. When hydrogen, oxygen, or air UFBs of this size are present in water, the surface tension of the water (usually about 72 mN / m) can be reduced.

[0024] The surface tension of the rearing water for larvae should be less than 72 mN / m, preferably 65 mN / m or less, and most preferably 55 mN / m or less. Surface tension can be measured using the plate method.

[0025] The density of UFBs (Ultraviolet Fibers) of hydrogen, oxygen, or air in the rearing water for larval fish is preferably between 7 million and 2 billion per milliliter, more preferably between 50 million and 2 billion. Within this density range, water with a surface tension of 50 mN / m or less, lower than that of normal water, can be obtained. The density of UFBs can be measured using known measuring devices. Specifically, particle trajectory analysis, dynamic light scattering, laser analysis and scattering, electrical detection band method, resonant mass spectrometry, and dynamic image analysis methods can be used.

[0026] In this specification, the "NanoSight LM10V-HS / CMOS camera" manufactured by Malvern was used as the measuring device (measurements were performed by Izumitec Co., Ltd.). Therefore, if any doubt arises regarding the density of UFB in hydrogen, oxygen, or air, it is advisable to measure it directly using this device or by using a converted value from a device whose correlation with this device has been clearly established.

[0027] In this invention, the rearing water for larvae must not only contain hydrogen, oxygen, or air UFB, but also have a dissolved oxygen concentration sufficient for rearing larvae. Normally, if the concentration is less than 1 mg / L, half of the larvae will die. Therefore, it is desirable that the rearing water for larvae has a dissolved oxygen concentration of 1 mg / L or more, preferably 3 mg / L or more, and most preferably 6 mg / L or more. It should be noted that the dissolved oxygen concentration in water is considered to saturate at 8-9 mg / L, so there is no particular need to set an upper limit on the range of dissolved oxygen concentration. It should be noted that oxygen UFB and dissolved oxygen concentration are different indicators, and an increase in oxygen UFB density does not necessarily mean an increase in dissolved oxygen concentration.

[0028] The method for maintaining dissolved oxygen at the above values ​​is not particularly limited, but an aeration device can be suitably used.

[0029] While it is preferable to add hydrogen, oxygen, or air UFB first, and then increase the dissolved oxygen concentration, in practice, the addition of hydrogen, oxygen, or air UFB and the increase in dissolved oxygen are carried out while circulating the water in the tank. Therefore, the addition of hydrogen, oxygen, or air UFB and the increase in dissolved oxygen can be done simultaneously or in reverse order.

[0030] Figure 8 shows a larval fish farming apparatus 1 according to the present invention. The farming apparatus 1 consists of a farming tank 10, a microbubble generating unit 12, and an oxygen supply unit 14. The farming tank 10 is a container in which eggs or larvae to be farmed are placed and farmed for a predetermined number of days. A lid is not required. The microbubble generating unit 12 consists of a hydrogen, oxygen, or air supply source 12b and a bubble water generating unit 12a. It is connected to the farming tank 10 by a suction pipe 12c and a discharge pipe 12d.

[0031] The hydrogen, oxygen, or air supply source 12b supplies either hydrogen, oxygen, or air. Of course, it may be possible to supply hydrogen, oxygen, and air together, or to supply only one of them (hydrogen, oxygen, or air) by switching.

[0032] The microbubble generating unit 12 draws in the rearing water from the aquaculture tank 10 through the suction pipe 12c, mixes hydrogen gas, oxygen gas, or air from the hydrogen, oxygen, or air supply source 12b into the rearing water as ultrafine bubbles, and returns it to the aquaculture tank 10 through the discharge pipe 12d.

[0033] The bubble water generation unit 12a is the part that mixes hydrogen, oxygen, or air as ultrafine bubbles into the feed water drawn in from the suction tube 12c, and known methods such as the ejector method, cavitation method, and resonance foaming method can be used. The apparatus described in Patent Document 4 can be suitably used as the bubble water generation unit 12a. The microbubble generation unit 12 may also be called a UFB generator (hydrogen UFB generator, oxygen UFB generator, air UFB generator) or a UFB generating device (hydrogen UFB generator, oxygen UFB generator, air UFB generator).

[0034] The oxygen supply unit 14 consists of a blower 14a and a diffuser pipe 14c. The blower 14a sends air to the diffuser pipe 14c placed in the aquaculture tank 10, supplying oxygen to the rearing water in the aquaculture tank 10 by aeration. The air sent from the blower 14a to the diffuser pipe 14c may also contain oxygen from the oxygen supply source 14b.

[0035] Figure 9 shows the larval fish rearing water production device 5 according to the present invention. The rearing water production device 5 can be composed of almost the same elements as the aquaculture device 1. That is, the aquaculture tank 10, the microbubble generation unit 12, and the oxygen supply unit 14 can be the same as in the case of the aquaculture device 1 in Figure 8. The rearing water production device 5 is provided with a water supply means 20 and a rearing water delivery unit 22.

[0036] The water supply means 20 consists of a supply source 20a and a water supply pipe 20b. The supply source 20a may be either seawater or freshwater, as long as it can be used as aquaculture water. It may also be aquaculture water that has been returned from a tank to which rearing water was supplied. A mechanism for adding water pressure to flow the water into the water supply pipe 20b may be included in the supply source 20a. The rearing water supply unit 22 consists of a pump 22a and a water supply pipe 22b located in the aquaculture tank 10.

[0037] The rearing water production device 5 adds hydrogen, oxygen, or air UFB to the rearing water supplied from the water supply means 20 to the rearing tank 10, and further increases the dissolved oxygen concentration to modify it into rearing water for larvae according to the present invention, which has a predetermined hydrogen, oxygen, or air UFB density and dissolved oxygen concentration, and is supplied to the rearing tank or the like from the water supply pipe 22b. [Examples]

[0038] The rearing water for larvae according to the present invention used in the following examples contains hydrogen UFB, oxygen UFB, or air UFB, and has a surface tension of 50 mN / m. The particle size distribution of the UFB all had the maximum frequency around 100 nm, and no UFB larger than 400 nm were present.

[0039] Furthermore, the dissolved oxygen concentration was adjusted using an aeration device placed in the tank so that it was approximately 6.6 mg / L in both the rearing water of the control group and the rearing water for larvae in the case of the present invention.

[0040] Furthermore, the following examples demonstrate that the presence of UFB increases the number of rotifers consumed (the number of rotifers ingested per fish; sometimes called the feeding rate) and the survival rate. This can be interpreted as the metabolism becoming more active in the presence of UFB, leading to improved health, increased food intake, and higher survival rates. This is called the "healing effect" of UFB on larvae. In the case of oxygen UFB, this effect is particularly pronounced and leads to an increase in the swim bladder opening rate. However, high metabolism leads to reduced growth. But ultimately, it improves production efficiency. Connect.

[0041] (Example 1) This study investigated the effects of air, oxygen, and hydrogen UFB water on the number of rotifers consumed by larval fish, focusing on the therapeutic effects of UFB water filled with various gases to promote larval activity. Specifically, the number of larval fish consumed was compared to the activity of fish in control water, air UFB water, oxygen UFB water, and hydrogen UFB water. Note that air UFB water, oxygen UFB water, and hydrogen UFB water are also simply referred to as air UFB water, oxygen UFB water, and hydrogen UFB water.

[0042] Test method At each day of growth of the larvae, the rearing water of the control group was compared with air-UFB water, oxygen-UFB water, and hydrogen-UFB water, which were created by adding air, oxygen, and hydrogen UFB to the control group's rearing water. Air-UFB water, oxygen-UFB water, and hydrogen-UFB water were all produced using the same rearing water (the same water used in the control group). The groups of tanks using air-UFB water, oxygen-UFB water, and hydrogen-UFB water were designated as the air-UFB water group, the oxygen-UFB water group, and the hydrogen-UFB water group, respectively (the same applies to the following examples). Each group consisted of 3 to 4 tanks.

[0043] (1) The day before the start of the experiment, 34 psu (Practical Salinity Unit) seawater filtered using a cartridge in a 200L tank was set to 23-24°C. The rearing water used had been prepared to have a dissolved oxygen concentration of 6.4 mg / L. (2) On the first day of the experiment, seawater from the air UFB water section, oxygen UFB water section, and hydrogen UFB water section was circulated once through the UFB generator to increase the bubble density. The particle density was 42 million particles per ml in the air UFB water section, 22 million particles in the hydrogen UFB water section, and 26 million particles in the oxygen UFB water section, and there were no significant differences in the distribution of bubble diameter between the sections. (3) Day 0: Air UFB water, oxygen UFB water, and hydrogen UFB water were prepared by circulating the UFB generator through the water during water changes, and 30L / tank water was changed each time. (4) 1-10 days old: Air UFB water, oxygen UFB water, and hydrogen UFB water were prepared in the same way as above during daily water changes, and 15L / tank was changed for each tank in each section. The number of rotifers consumed was measured by counting the number of rotifers in the intestinal tract of 5 larvae in each tank and taking the average.

[0044] Figure 1 shows the results of a study on the therapeutic effect of promoting larval activity by measuring the number of foods consumed. Referring to Figure 1, the horizontal axis shows the four tanks for each test group, and the vertical axis shows the number of foods consumed (individuals / tail). On the horizontal axis, the "group" is omitted and simply indicated as "hydrogen UFB," "oxygen UFB," etc. The untreated group is the group that did not contain UFB.

[0045] Feeding of the larvae was started at 2 days of age. Figure 1 shows the number of rotifers in the intestinal tract of 2-day-old larvae 3 hours after feeding. In both the oxygen-UFB water group and the hydrogen-UFB water group, the number of rotifers consumed increased compared to the untreated group.

[0046] Following the food intake of 2-day-old larvae shown in Figure 1, the effects of air-UFB water, oxygen-UFB water, and hydrogen-UFB water on subsequent larval growth were investigated. Figure 2 shows the growth (body length (mm)) of 10-day-old larvae. Referring to Figure 2, the horizontal axis is the same as in Figure 1, and the vertical axis is body length (mm).

[0047] Referring to Figure 2, the air-UFB water and hydrogen-UFB water groups showed higher levels than the untreated group. In the oxygen-UFB water group, feeding increased, but this was thought to be due to increased metabolism and did not have an effect on growth. However, the larvae were more resilient to stress and healthier, and it is thought that productivity will ultimately improve. On the other hand, air-UFB water and hydrogen-UFB water were thought to be effective in both feeding and growth of the larvae.

[0048] (Example 2) The effects of air-UFB water, oxygen-UFB water, and hydrogen-UFB water on the spawning mortality rate of larval fish were investigated. The test method was the same as in Example 1.

[0049] When larval fish rise to the water surface due to surface tension, they become trapped at the surface and are unable to return to the water, resulting in death by surfacing. This study investigated the extent to which surfacing deaths could be reduced by the surface tension-reducing effects of air-UFB water, oxygen-UFB water, and hydrogen-UFB water compared to the untreated group. After measuring the number of fish consumed, Figure 3 shows the test results regarding the surfacing death rate of larval fish due to the soothing effect. The horizontal axis of Figure 3 shows the tanks for the untreated group, air-UFB water group, hydrogen-UFB water group, and oxygen-UFB water group. The vertical axis shows the surfacing death rate (%) of 10-day-old larval fish.

[0050] Referring to Figure 3, the air UFB (Ultraviolet Fiberflow) treatment group, the oxygen UFB treatment group, and the hydrogen UFB treatment group all showed lower surface tension than the untreated group. It was concluded that using air, oxygen, or hydrogen in the UFB reduces surface tension and effectively prevents larval fish from floating to the surface and dying.

[0051] After measuring the mortality rate upon surfacing in Figure 3, the test results regarding the survival rate of larvae due to the therapeutic effect are shown in Figure 4. Referring to Figure 4, the horizontal axis represents the tanks for the untreated group, the air UFB group, the hydrogen UFB group, and the oxygen UFB group. The vertical axis represents the survival rate (%) of 10-day-old larvae.

[0052] Referring to Figure 4, the air UFB water group, oxygen UFB water group, and hydrogen UFB water group all showed higher performance than the untreated group. In particular, the hydrogen UFB group showed statistically low variability and was judged to be the highest. Air UFB water, oxygen UFB water, and hydrogen UFB water were thought to be effective in three aspects of larval feeding, mortality at the surface, and survival. Among these, hydrogen UFB water, which contains hydrogen UFB and is thought to have a calming effect, was confirmed to be the most superior in increasing feeding and growth. Furthermore, it was newly suggested that although growth may be inferior in oxygen UFB water due to increased feeding and increased metabolism, health may be superior.

[0053] (Example 3) Next, we investigated the effects of oxygen UFB density on swim bladder opening rate, number of prey consumed, and growth.

[0054] Test method (1) On the day before the experiment, 34 psu seawater filtered using a cartridge in a 200 L tank was set to 23-24°C. The culture water used had been prepared to have a dissolved oxygen concentration of approximately 6.8 mg / L. (2) On the day before and two days before the start of the experiment, the seawater in the external tank was stopped, and the UFB generator was circulated for 6 hours or 24 hours, respectively, and then the water was pumped into the rearing tank to create oxygenated UFB water with different UFB densities. When the UFB density per 1 ml was measured, it was found to be 7 million particles in the low-density oxygenated UFB water section and 51 million particles in the high-density oxygenated UFB water section. (3) 0-10 days old: The animals were kept for 10 days without water changes.

[0055] Figure 5 shows the results of the effect of oxygen UFB density on the number of organisms feeding. Referring to Figure 5, the horizontal axis represents the untreated group, the low-density oxygen UFB group, and the high-density oxygen UFB group. Each group consisted of three tanks. The vertical axis represents the number of organisms feeding (individuals / tail) at 10 days of age.

[0056] Referring to Figure 5, the number of baits consumed increased significantly to about twice that of the untreated group in the high-density oxygen-UFB water group. Since the results are clearer than in Example 1 (Figure 1), it was found that the effect of oxygen-UFB water is pronounced at high densities. On the other hand, the effect in the low-density oxygen-UFB water group was almost negligible, indicating that a particle density higher than 7 million particles is necessary. The reproducibility of Example 1 was confirmed, and it was verified that the effect depends on the density of the oxygen-UFB.

[0057] After measuring the number of fish fed as shown in Figure 5, the results of the study on the growth of larvae due to the therapeutic effect were investigated and are shown in Figure 6. Referring to Figure 6, the horizontal axis represents the untreated group, the low-density oxygen UFB water group, and the high-density oxygen UFB water group. Each group consisted of three tanks. The vertical axis represents body length (mm).

[0058] Referring to Figure 6, growth decreased in the high-density oxygen UFB water treatment area. Similar to Example 1, feeding increased in the high-density oxygen UFB water, but growth decreased, likely due to increased metabolism. However, the larvae were energetic, resistant to stress, and healthy, which is expected to lead to improved production efficiency in the end. On the other hand, the low-density oxygen UFB water had almost no effect on growth, similar to feeding, confirming that a particle density higher than 7 million particles is necessary.

[0059] (Example 4) We investigated the effect of high-density oxygenated UFB water on the swim bladder opening rate of larval fish. Larvae of many fish species, including high-value fish such as bluefin tuna, grouper, and yellowtail, come to the surface after starting to feed and swallow air to form a swim bladder (swim bladder opening). Failure to do so results in spinal deformities in most fish species, making it an extremely important indicator. Therefore, we conducted a study to investigate the prevention of larval deformities through the healing effect of measuring swim bladder opening rate.

[0060] Test method (1) On the day before the experiment, 34 psu seawater filtered using a cartridge in a 200 L tank was set to 23-24°C. The culture water used had been prepared to have a dissolved oxygen concentration of 6.4 mg / L. (2) On the day before and two days before the start of the experiment, seawater was stopped in the external tank, and the UFB generator was circulated for 6 hours or 24 hours, respectively, and then the water was pumped into the rearing tank to create oxygenated UFB water of different densities. When the UFB density per 1 ml was measured, it was found to be 7 million particles in the low-density oxygenated UFB water section and 51 million particles in the high-density oxygenated UFB water section. (3) 0-10 days old: They were kept in captivity for 10 days without water changes.

[0061] Figure 7 shows the results for swim bladder opening percentage. The horizontal axis represents the untreated group, the low-density oxygen UFB water group, and the high-density oxygen UFB water group. Each group consisted of three tanks. The vertical axis represents swim bladder opening percentage (%).

[0062] The addition of high-density oxygen-rich UFB water resulted in extremely high swim bladder opening rates of 90% to 100%, a significant difference from the untreated group's rate of around 70%. It was thought that high-density oxygen-rich UFB water activated metabolism and promoted swim bladder opening behavior. On the other hand, low-density oxygen-rich UFB water had almost no effect, indicating that, similar to feed intake and growth, a particle density higher than 7 million particles is necessary for swim bladder opening rates.

[0063] Aquaculture is expanding as a global protein supply business, and with strong demand from Japanese cuisine, it is expected to grow even more in the future. However, the bottleneck is the stable production of larval fish during the seedling stage. Since larval fish are very fragile, developing technology that allows for mass production of healthy fish without deformities is extremely important.

[0064] This technology focuses on reducing water surface tension and promoting metabolism, which are problematic areas, to improve the yield of larval fish and establish a foundation for aquaculture. In particular, by changing the type of hydrogen or oxygen gas used, it can be used to improve feeding, growth, survival rate, and swim bladder opening rate, as well as to prevent death at the surface and deformities.

[0065] For example, in the case of groupers such as the longtooth grouper, where deformities are a serious problem, oxygenated UFB water is considered good for increasing the opening of the swim bladder cavity, while hydrogenated UFB water is considered good for tuna, where both survival rate and growth should be accelerated. Furthermore, since the swim bladder cavity is fully opened in groupers by about 6 days after hatching and in tuna by about 3 days after hatching, using oxygenated UFB water until then and then switching to hydrogenated UFB water can be used to prevent deformities and promote growth.

[0066] Because the degree of problems such as feeding, growth, survival rate, death at the surface, and deformities differs depending on the fish species and developmental stage, a wide range of applications using oxygenated or hydrogen-rich UFB water are possible, making it extremely valuable for industrial use. [Industrial applicability]

[0067] This invention can be suitably used in the cultivation of larval fish using freshwater and seawater. [Explanation of Symbols]

[0068] 1 Aquaculture equipment 5 Breeding water production equipment 10 Aquaculture tank 12. Microbubble generation section 12a Bubble water generation section 12b Hydrogen, oxygen, or air supply source 12c suction tube 12d discharge pipe 14. Oxygen supply unit 14a Blower 14b Oxygen supply 14c air diffuser 20 Water supply means 20a Source 20b Water pipe 22 Breeding water supply section 22a Pump 22b Water pipe

Claims

1. Rearing water for larvae, characterized by having at least hydrogen ultrafine bubbles and a dissolved oxygen concentration of 1.0 mg / L or more.

2. The aforementioned ultrafine bubbles are characterized by having a density of more than 7 million but no more than 2 billion bubbles per milliliter, as described in claim 1.

3. A method for cultivating larvae, characterized by cultivating larvae using the rearing water for larvae according to claim 1 or 2.

4. A fish tank and A microbubble generating unit that supplies at least hydrogen ultrafine bubbles to the water tank, A larval fish farming apparatus characterized by having an oxygen supply unit that supplies oxygen to the tank.

5. A process of adding at least hydrogen ultrafine bubbles to water, A method for producing rearing water for larvae, characterized by comprising the step of supplying oxygen to the water.

6. A fish tank and A water supply means for supplying water to the aforementioned tank, A microbubble generating unit that supplies at least hydrogen ultrafine bubbles to the water tank, The oxygen supply unit that supplies oxygen into the water tank, A apparatus for producing rearing water for larvae, characterized by having a rearing water supply unit that can discharge the water in the tank.

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