Microplastic collection device that does not entangle small fish

Abstract

To provide a microplastics recovery device capable of protecting aquatic organisms such as small fishes and not entangling the small fishes. [Solution] There is a tank 1 in which small fish can swim, and inside the tank 1 there is a net 3 that can catch microplastics 2, seawater is sucked into the tank 1 using a pump 5 and the seawater that passes through the net 3 is discharged, the pump 5 is attached downstream of the net 3, and a speaker 7 is attached to the underside of the lid 6 of the tank 1, and the speaker 7 is positioned higher than the water level H inside the tank 1, the pump 5 is stopped periodically at predetermined times, and when the pump 5 is stopped, a deterrent sound is made from the speaker 7, so that small fish that have entered the tank 1 are allowed to escape into the sea through a passage 8 that sucks in seawater.

Description

[Technical field]

[0001] This invention relates to a microplastic collection device that does not entangle small fish. [Background technology]

[0002] Microplastics floating in the ocean are having serious effects on marine life and human health. Microplastics are very small pieces of plastic, generally less than 5mm in size. In recent years, the adverse effects of microplastics that have flowed into the ocean on the environment have become more serious, and research into the issue is also progressing. Microplastics are broadly divided into two categories: "primary microplastics" and "secondary microplastics." Primary microplastics are tiny plastics such as the scrubbing agents found in facial cleansers and toothpastes that flow into the ocean through household wastewater and sewage treatment. Once in the ocean, it is nearly impossible to recover them, and it is said to be extremely difficult to take measures after they are used in products. Secondary microplastics are plastic products such as plastic bags, PET bottles, and cigarette nets that flow into the ocean via gutters and rivers, where they are degraded and broken down into microscopic pieces by ultraviolet rays and waves. There are large amounts of microplastics in the oceans today, and their tiny size makes them extremely difficult to collect, which poses a major challenge. The problem is particularly serious in the ocean, where small fish and other aquatic creatures mistake microplastics for food and eat them, thus starting a food chain. I became interested in how people around the world collect microplastics, so I looked online and found that there was little information available and that no concrete collection method had yet been established anywhere in the world. After further research, I found out that in Japan, there is a device called "Sea Bin" that collects microplastics at Kanazawa Hakkeijima Sea Paradise, and a device called "Jellyfish Bot" that cleans up marine debris, the only one of its kind in Japan, so I immediately went to see them. It was December 23, 2022. When I saw them in person, I got the impression that they were quite large-scale devices. According to the staff, each Sea Bin costs about 700,000 yen. Each Jellyfish Bot is apparently expensive, costing several million yen. Because the device is fixed to a pier and installation locations are limited, it may be susceptible to the effects of waves and currents depending on the location and shape of the pier, which could result in a decrease in the efficiency of microplastic collection. I also wondered whether typical microplastic collection devices are sufficiently designed to prevent small fish from getting caught in them. From around this time, I wanted to create a device that could collect microplastics more easily and efficiently, while protecting small fish and other aquatic organisms. Patent documents 1 to 3 describe large-scale devices and systems for collecting microplastics. When it comes to protecting small fish and other aquatic creatures, I noticed that there are certain sounds that fish dislike. Ever since I was in elementary school, I used to enjoy doing sound tests like, "If you can hear a mosquito sound at XX Hz, you're young! If you can't hear XX Hz, you're not young!" Also, when I went to visit the graves, there were places where they would make mosquito noises to keep cats away, and I always found that noise unpleasant, which was one of the things that sparked my interest in sound. We wondered whether, just as there are sounds that humans find unpleasant, there might also be sounds that small fish find unpleasant. After doing some research on the Internet, I found information that said fish dislike certain high and low frequency sounds, and I initially hypothesized that sounds around 5000 Hz might be the ones that fish dislike the most. In addition, Patent Documents 4 to 7 also describe the use of sound for fish. When I told a professor at Hosei University about my idea, he agreed to help us try an experiment first, and we conducted the experiment in the sea off Nojima in Yokohama City, Kanagawa Prefecture on September 15, 2024. The experiment method was as follows: first, the professor caught small fish and shrimp with a special net, and then placed seawater and the creatures in a boat-shaped bucket (a plastic container similar to a baby bath) on the spot. When I tried to play a 5000Hz sound from a speaker using Bluetooth (registered trademark) on my smartphone, it had no effect on any of the creatures and no change was observed. I realized that my initial prediction was wrong. Later, my teacher told me that there was no evidence that small fish disliked 5000 Hz, and advised me to read relevant papers and literature. After reading a lot of literature, I found out that the sounds that small fish dislike most are 100Hz and 110dB to 160dB. I also learned that small fish dislike the sound of a bird diving its head into the water. However, since 110dB is an alarm level noise, I couldn't test it at home because it would be a nuisance to my neighbors. I decided not to pursue the volume and to continue the experiment with the loudest sound that wouldn't disturb my neighbors. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-66030 [Patent Document 2] Patent Publication No. 2022-108255 [Patent Document 3] JP 2024-42846 A [Patent Document 4] JP 2014-171411 A [Patent Document 5] JP 2016-111943 A [Patent Document 6] JP 2024-20706 A [Patent Document 7] Japanese Patent Application Publication No. 62-239935 Summary of the Invention [Problem to be solved by the invention]

[0004] I wanted to create a device that could easily, efficiently, and energy-efficiently collect microplastics floating in the ocean, improve the marine environment, and protect aquatic life such as small fish. Recent research has shown that microplastics have been detected in fish, and that they can also affect humans who eat those fish. We thought that by mitigating the effects of microplastics on the food chain of aquatic organisms, we could also solve the problem for humans.

[0005] Therefore, the present invention aims to propose a microplastic collection device that can protect aquatic organisms such as small fish. [Means for solving the problem]

[0006] The microplastics recovery device of the present invention, which does not entangle small fish, as described in claim 1, has a tank 1 in which small fish can swim, and inside the tank 1 is a net 3 that can catch microplastics 2, seawater is sucked into the tank 1 by a pump 5 and the seawater that has passed through the net 3 is discharged, the pump 5 is attached downstream of the net 3, a speaker 7 is attached to the underside of the lid 6 of the tank 1 and the speaker 7 is positioned higher than the water level H in the tank 1, the pump 5 is stopped periodically at a predetermined timing, and when the pump 5 is stopped, a repelling sound is made from the speaker 7, thereby allowing the small fish that have entered the tank 1 to escape into the sea through a passage 8 that sucks in the seawater. The present invention described in claim 2 is characterized in that, in the microplastic collection device described in claim 1 that does not entangle small fish, the repellent sound is the sound of water splashing generated by hitting the water surface H about 3 to 8 times per second, and the sound of water splashing has a frequency between 773 Hz and 13,544 Hz and includes irregular frequencies from 1,000 Hz to 11,000 Hz. The present invention described in claim 3 is characterized in that, in the microplastic collection device described in claim 1 that does not entangle small fish, an LED light 10 is installed in the tank 1 along with the speaker 7, and the LED light 10 is made to flash when the pump 5 is stopped. The present invention described in claim 4 is characterized in that, in the microplastic collection device described in claim 1 that does not involve small fish, aeration is performed when the pump 5 is stopped. Effect of the Invention

[0007] According to the microplastic collection device of the present invention, which does not entangle small fish, when the pump is stopped, there is no flow toward the tank in the passage that draws in seawater, and by emitting a repelling sound from the speaker, the small fish will take evasive action and try to escape from the tank, so they can be released into the ocean through the passage that draws in seawater. [Brief description of the drawings]

[0008] [Figure 1] A diagram showing the microplastics collection device of the present invention that does not entangle small fish. [Diagram 2] A diagram showing the operation of this microplastic collection device [Diagram 3] A diagram showing the results of an experiment conducted with two marine fish, clownfish and four blue-green damselfish. [Figure 4] A photo showing the behavior of a clownfish and a blue-green damselfish when testing the sound of splashing water (water splashing). [Figure 5(a)] Photo of the sound of water splashing [Figure 5(b)] Photo of the sound of water splashing [Figure 5(c)] Photo of the sound of water splashing [Figure 6(a)] A photo of the frequency change of a 10-second recorded sound [Figure 6(b)] A photo of the frequency change of a 10-second recorded sound [Figure 6(c)]A photo of the frequency change of a 10-second recorded sound [Figure 7] A diagram showing the results of an experiment conducted on rockfish (10-12 cm), a bottom-swimming fish. [Figure 8] A photo of the movement of a rockfish when trying out the sound of splashing water (water splashing). [Figure 9] A diagram showing the results of an experiment using a horse mackerel (21 cm) swimming through the air. [Figure 10] Figure showing the results of an experiment conducted on Japanese dace [Figure 11] Similar to Figure 4, this is a photo of the behavior of a clownfish and a blue-green damselfish when the sound of splashing water (water splashing) was tested. [Figure 12] A photo of the deterrent sound produced by the recovery device we developed. [Figure 13] A photo of the additional experiment [Figure 14] A diagram showing the results of an experiment on the effects of light on horse mackerel (21 cm). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The microplastic collection device of the first embodiment of the present invention, which does not involve small fish, has a tank in which small fish can swim, and inside the tank is a net that can catch microplastics. Seawater is drawn into the tank using a pump and the seawater that passes through the net is discharged. The pump is installed downstream of the net, and a speaker is attached to the underside of the tank's lid, which is positioned higher than the water level in the tank. The pump is stopped periodically at predetermined times, and when the pump is stopped, a deterrent sound is emitted from the speaker, causing small fish that have entered the tank to escape into the sea through the passage that draws in seawater. In this way, by having a tank in which small fish can swim, small fish that mistake microplastics for food and enter the tank, or small fish that are accidentally sucked into the tank by the suction force of the pump, can swim in the tank for a while. The pump is installed downstream from the net so that small fish are not sucked into the pump and injured. The pump is periodically stopped at a predetermined timing. When the pump is stopped, there is no flow toward the tank through the seawater intake passage, and by emitting a repelling sound from the speaker, the small fish will take evasive action and try to escape from the tank, allowing them to escape into the sea through the seawater intake passage. In the experiment, playing the sound from above the water surface was more effective than playing the sound underwater, so the speaker was placed above the water surface in the tank. By not installing the speaker underwater, I think it will be able to withstand long-term use. Also, I think the acoustic effect will be improved by playing the sound from the tank lid downwards.

[0010] In a second embodiment of the present invention, in a microplastics collection device according to the first embodiment that does not entangle small fish, the repelling sound is the sound of water splashing generated by hitting the water surface approximately 3 to 8 times per second, and the sound of water splashing has a frequency between 773 Hz and 13,544 Hz and includes irregular frequencies from 1,000 Hz to 11,000 Hz. The sound of splashing water is similar to the sound made when a bird dips its head into the water to eat a fish swimming near the surface, or the sound of a fish struggling desperately after being caught, and I think it is the sound that small fish make to sense that their life is in danger.

[0011] The third embodiment of the present invention is a microplastics recovery device according to the first embodiment that does not entangle small fish, in which an LED light is installed in the tank along with a speaker, and the LED light is made to flash when the pump is stopped. In this way, by flashing the light together with the repelling sound, the small fish will swim more actively, which I believe will increase the effectiveness of releasing the small fish back into the sea.

[0012] The fourth embodiment of the present invention is a microplastic collection device according to the first embodiment that does not involve small fish, in which aeration is performed when the pump is stopped. In this way, aeration combined with the deterrent sound increases the effectiveness of encouraging small fish to escape back into the sea. EXAMPLES

[0013] Figure 1 shows the microplastic collection device of the present invention, which does not entangle small fish. This microplastic collection device has a cylindrical tank 1 in which small fish can swim. By having Tank 1 in which small fish can swim, small fish that mistake microplastics 2 for food and enter Tank 1 can swim in Tank 1 for a while.

[0014] Inside tank 1 is net 3 that can catch microplastics 2. A cylindrical inner tank 4 is placed inside tank 1, and net 3 is attached to this inner tank 4. By attaching net 3 to inner tank 4 in this way, the area of ​​net 3 can be increased, preventing clogging with microplastics 2 and allowing for long-term use. Seawater is sucked into tank 1 by pump 5, and the seawater that passes through net 3 is discharged. By installing multiple pumps 5, more microplastics 2 can be collected. Pump 5 is installed downstream of net 3. By installing pump 5 downstream of net 3 in this way, small fish will not be sucked into pump 5 and injured.

[0015] A speaker 7 is attached to the underside of the lid 6 of the tank 1. The speaker 7 is positioned higher than the water surface H in the tank 1. In the experiment, playing the sound from above the water surface H was more effective than playing the sound underwater, so speaker 7 is placed above the water surface H in tank 1. By not installing speaker 7 underwater, it can withstand long-term use. Also, playing the sound downward from lid 6 of tank 1 improves the acoustic effect. Tank 1 is connected to the outside (underwater) through passage 8 that takes in seawater and passage 9 that discharges seawater. It is best for passage 8 that takes in seawater to be close to the water surface H in order to collect microplastics 2. Passage 9 that discharges seawater is placed at a lower position than passage 8 that takes in seawater. Pump 5 is attached to passage 9 that discharges seawater. An LED light 10 is installed inside the tank 1 together with a speaker 7. The LED light 10 is also installed on the underside of the lid 6 of the tank 1 together with the speaker 7.

[0016] Although not shown in the drawing, the microplastics collection device is equipped with a battery that supplies electricity to the pump 5, speaker 7, and LED light 10, and a control device that turns on and off the pump 5, speaker 7, and LED light 10. The speaker 7 and LED light 10 do not have to be separate, but it is also possible to use a speaker 7 with an LED light 10 that is linked to sound and lighting. The small fish in question here are those large enough to fit into Tank 1, and are considered to be small fish that can enter through Passage 8, which draws in seawater.

[0017] Figure 2 shows the operation of this microplastics collection device. Figure 2(a) shows the operation of the pump, and Figure 2(b) shows the operation of the pump at rest. As shown in Figure 2(a), microplastics 2 are collected while pump 5 is operating. As shown in Figure 2(b), while pump 5 is stopped, small fish that have entered tank 1 are released into the sea through passage 8, which draws in seawater. The pump 5 is stopped periodically at a predetermined timing. When the pump 5 is stopped, a repelling sound is emitted from the speaker 7. When the pump 5 is stopped, the LED light 10 is made to blink. When pump 5 is stopped, there is no flow toward tank 1 in passage 8 that draws in seawater, and by emitting a repelling sound from speaker 7, the small fish will take evasive action and try to escape from tank 1, so they can be released into the sea through passage 8 that draws in seawater. In addition, the LED light 10 flashes along with the repelling sound, encouraging small fish to swim more actively, which increases the effectiveness of luring the small fish back into the sea.

[0018] Below we explain the experiment on the effects of sound on small fish. Figure 3 shows the results of an experiment conducted using two marine fish, clownfish and four blue-green damselfish. Six small fish were placed in a deep seawater tank (40cm wide x 30cm high x 12cm deep), and 20 types of loud sounds were played from Speaker 7 using Bluetooth (registered trademark), and the fish's reaction to each sound was observed. Each experiment was performed three times to confirm reproducibility.

[0019] First, I tried the "100Hz of Hope" that I read about in a reference. The results showed no particular change between the first and third times, but the second time, it seemed to react a little better than before the sound was played. Next, I tried 500Hz. The first time, the fish came to speaker 7. The second time, there was no particular change. The third time, the fish disliked it and moved away from speaker 7. Next I tried 1000hz. The first time, the fish hated it and moved away from speaker 7. The second and third times, there was no noticeable change. I tried the 5000Hz frequency again, which I had first tested in the ocean. But just like the last time, there was no change in the results. Next, I tried 7500Hz. The first time, the fish were put off by it and moved away from speaker 7. The second time, the fish came closer to speaker 7. The third time, there was no particular change. Next I tried 10kHz. The first and second times it leaned towards speaker 7. The third time there was no particular change.

[0020] Next, we tried the sound of splashing water (splashing water sounds). The reason was that there was literature that said fish dislike the sound of diving their heads into the water to eat other fish (their fellows), so we thought that the sound of splashing water might also be annoying to fish. For the sound of splashing water, we filled a washbasin with water at home and recorded ourselves tapping it with our hands. We also made the sound of a fish dipping its head into the water, but this experiment had no effect on the fish, so we tried the sound of splashing water and it worked well. The result was that in all three instances, the small fish clearly moved away from Speaker 7 and showed signs of dislike. I thought this was the most effective sound, so I decided to try it with more other fish.

[0021] Next, we tried the sounds of seagulls, which surprisingly didn't change at all three times. Then I tried the alarm sound. There was no particular change the first and third time. The second time, a small fish was attracted to speaker 7. Next, we tried a male voice. Again, no changes were observed three times. We also tried a female voice (child). As with the male voice, there was no change in the results. I also tried a female voice (adult), and just like the male voice, there was no change in any of the three times I tried it. Next, we tried the sound of a humpback whale. The first time, the small fish clearly moved away from Speaker 7, showing signs of dislike. The second and third times, they still reacted, although not as much as the first time. One of the blue-green damselfish in particular went into its octopus pot when we played the sound of a humpback whale, and did not come out for a while. The clownfish also backed away from Speaker 7.

[0022] Next I tried the mechanical sounds. Again, no change occurred all three times. I tried the school bell sound. Again, no change at all three times. Interestingly, all three times the man snored, fish were attracted to speaker 7. Next, I tried the sound of a motorcycle. The first time I tried the motorcycle sound, small fish were attracted to speaker 7. The second and third times, there was no particular change. We also tried a knocking sound on the door. All three times, it clearly attracted small fish to speaker 7.

[0023] Next, we tried the sound of a mosquito flying. The first time, there was a clear change. The small fish hated the sound and moved away from Speaker 7. The second and third times, there was still a reaction, although not as much as the first time. Finally, we tried a high-pitched bird call, which on all three occasions elicited a reaction from the small fish, causing them to move away from Speaker 7.

[0024] Before the experiment, I thought that a 5000Hz sound would be effective, but when I actually tested it with small fish, I unexpectedly found that the fish reacted best to the sound of splashing water (the sound of water splashing in a washbowl) played from Speaker 7, rather than to a specific frequency sound, and disliked it. I imagined this sound as a series of movements, including the sound of a bird dipping its head into the water to eat a fish swimming near the surface, and the sound of a fish struggling desperately after being caught. This is a sound source that makes fish sense a threat to their life. Conversely, this experiment also found that some types of small fish prefer certain sounds to Speaker 7. For example, the sound of a door being knocked or a man snoring. We have also confirmed the reproducibility of this sound.

[0025] In addition, the experiments with 100Hz, 500Hz, etc. were performed by playing the sound once, stopping it, and then trying the next Hz. In addition, I also tried playing sounds from 100Hz to 10KHz once automatically (gradually increasing the number) to see at what point the fish reacted, but the results were almost the same in both cases. The reproducibility of a single Hz did not result in a definite reaction.

[0026] Figure 4 shows the behavior of a clownfish and a blue-green damselfish when we tried the sound of splashing water. The photos were edited from a video. Speaker 7 is at the position indicated by the arrow. The reference lines from speaker 7 are L1 and L2. L1 is the reference line closest to speaker 7. By playing the sound of splashing water from Speaker 7, one clownfish retreats while facing Speaker 7, then turns around and swims away from Speaker 7. The blue-green damselfish also swims away from Speaker 7.

[0027] Figures 5(a) to 5(c) are photos taken when the sound of splashing water was generated. The photos were edited from a video. Photo (1) is the start, photo (2) is taken 0.05 seconds after photo (1), and photo (3) is taken 0.05 seconds after photo (2). Photo (21) is taken 1 second after photo (1). As shown in the picture, we filled a basin with water and created a sound by hitting the water surface with the palm of our hand. With fingers spaced about 2 cm apart, the palm of the hand was struck forcefully vertically from a height of about 2-4 cm against the water surface H. To maximize sound production, the hand movement was made as quickly as possible and the height was not allowed to exceed 10 cm. (Any more than this would require the hand to move a large distance, making it difficult to produce small sounds.)

[0028] In the experiment, the effectiveness of hitting the water about 3 to 8 times per second was confirmed, with hitting the water 8 times per second being the most effective. The speed was super fast to mimic the way a fish thrashes about. The recording environment was in the bathroom of my house, with a basin filled with water and recorded in the open air. I recorded in the bathroom because the sound echoed in the bath. To prevent noise during recording, I kept the sound silent and left the bathroom door open to prevent sound echoing. The sounds were recorded in the air using a smartphone microphone placed approximately 8 cm above the water surface.

[0029] I then investigated the frequency of the sounds recorded in this way. Figures 6(a) to 6(c) show the frequency change over a 10 second period. Each photo was taken at the point when the frequency changed. In other words, photo (1) shows the starting frequency of 10970Hz, and photo (2) shows the point when the frequency changed from 10970Hz to 1401Hz. Minor changes have been omitted.

[0030] As can be seen from Figure 6, the frequency of the sound of splashing water ranged from a minimum of 773 Hz to a maximum of 13,544 Hz, with small ups and downs occurring mainly between around 1,000 Hz and around 11,000 Hz (11 KHz). When checking the video of the experiment, the sound in the part where the fish was moving away from speaker 7 was a repeated up-and-down sound from about 1000Hz to about 11000Hz (11KHz). It seems that this difference in pitch stimulates the small fish.

[0031] When I shared my findings with Professor Yamada of Tokai University, he advised me to try experimenting with other kinds of small fish, in addition to clownfish (3-4cm) and blue-green damselfish (2.0-2.5cm). However, there were limited ways to obtain other saltwater fish, so I was at a dead end. So I decided to go to the Honmoku Sea Fishing Facility in Yokohama and conduct an experiment on fish I caught in the sea. The experiment was conducted by filling a polystyrene foam container (W42cm x H30cm x D25cm) with seawater immediately after catching the fish. In this experiment, we tested and compared rockfish (10-12 cm), a bottom-swimming fish, and horse mackerel (21 cm), a bottom-swimming fish.

[0032] Figure 7 shows the results of an experiment conducted on rockfish (10-12 cm), a bottom-swimming fish that swims in the lower layers. One thing to note about this experiment is that because rockfish are low-swimming fish, they experience a significant change in water pressure when caught, and even if they are placed in a styrofoam container filled with seawater and allowed to swim, they will flip over. Water pressure is high at depths, and when found near the surface the water pressure drops suddenly, which can cause the swim bladder inside the rockfish's body to expand. Normally, it is not a good idea to conduct experiments on an upside-down fish like this, but when we tried it, we got some very interesting results, so we decided to record the results.

[0033] Figure 8 shows a photograph of the behavior of a rockfish when it was tested with the sound of splashing water (water splashing). The photograph was edited from a video. When the sound of splashing water was played from Speaker 7 to the flipped over rockfish, it got up and started swimming forward desperately. It ended up swimming to a range of 41cm to 144cm. Then, when the sound stopped, it flipped over again. I thought this was proof that the rockfish felt the sound of splashing water was a threat to its life and was instinctively fleeing. I also confirmed the reproducibility. What is interesting is that when speaker 7 was playing 100Hz, a sound that many fish generally dislike, the rockfish repeatedly approached speaker 7 on its own, or simply sank under speaker 7. This means that 100Hz is a sound that rockfish like. After the 100Hz sound from speaker 7 disappeared, the rockfish would start to swim away, and sometimes would move away from speaker 7, but would quickly return to being under speaker 7 on its own.

[0034] Figure 9 shows the results of an experiment conducted on a horse mackerel (21 cm) swimming in the air. When we conducted experiments under similar conditions with horse mackerel (21 cm), they responded to both the sound of splashing water and a 100 Hz sound. In the experiment, because the horse mackerel were large compared to the size of the styrofoam, we were able to see that they reacted to specific sounds and moved faster, but it was not clear whether they disliked the sounds or liked them. It is true that when splashing water or 100Hz sounds were played, the fish swam more actively than when the sounds were not played. Also, when the sounds were stopped, the fish swam more slowly and even took rests.

[0035] Figure 10 shows the results of an experiment conducted on Japanese dace. Some species of ugui, a fish of the carp family, migrate down to the sea and have been confirmed to live in brackish water and saltwater. When the school of dace was exposed to the sound of splashing water just like the other fish, they also showed aversion to it.

[0036] As a result of these experiments, many fish reacted to the sound of splashing water (the sound of water splashing, the sound of a fish fleeing from being eaten) and the voice of a humpback whale (a predator in the sea), and showed repulsive behavior. They also showed a similar reaction to the sound of a mosquito flying. Conversely, it was also discovered that there are sounds that attract fish. Humpback whales are not predators that attack other animals, but rather obtain energy by efficiently ingesting small organisms in the sea, but they are predators in the food chain. They eat krill, capelin, mackerel, salmon, etc., and it is said that they eat 3% to 5% of their body weight, about 1 to 1.5 tons, a day. It seemed that the small fish were scared of the sound of this humpback whale. The frequency of humpback whale vocalizations ranged from a minimum of 10 Hz to a maximum of 1,426 Hz, with small ups and downs occurring mainly in the ranges of 10 Hz to 300 Hz and 100 Hz to 900 Hz. It appears that these sound fluctuations in the 300Hz to 800Hz range had an effect on the small fish. Although monotonous sounds of 100Hz or 1000Hz produced a poor response, experiments confirmed that sounds with small frequency fluctuations were effective.

[0037] Based on the results of this experiment, we thought that playing a specific sound that sounds like a living creature moving, but not monotonous, with a different rhythm from speaker 7 might be effective in keeping small fish away from the device. For example, what if we suddenly played a pattern where the sound changed from a quiet sound that is natural to fish to the sound of splashing water, or if we played the sound of splashing water or the voice of a humpback whale randomly in a loop? If the same sound is repeated many times, the fish will get used to it, so we thought it would be effective to play sounds with a rhythm and pattern that the fish would not get used to.

[0038] The mackerel I mentioned earlier is a fish that swims on the surface of the ocean and is targeted by birds from the sky as prey, and is also targeted by humpback whales. This is true not only for mackerel, but also for horse mackerel and sardines. Humpback whales come near the surface when feeding or breathing. Large whales like humpback whales need to come to the surface periodically to breathe, and they also stay near the surface when catching small fish and krill through "bubble net feeding." Humpback whales can also be seen swimming near the surface in search of food in the waters off Japan. As such, underwater creatures such as small fish such as horse mackerel, mackerel, sardines, and saury are targeted by humpback whales at the surface and are sometimes at risk of being preyed upon by birds from the sky, so we believe that the sounds of splashing water and the cries of humpback whales act as a deterrent for these underwater creatures.

[0039] When we experimented with splashing water sound + light or 100Hz sound + light, we found that the horse mackerel were significantly more active than when there was no light. I thought that horse mackerel, which swim in the middle to surface layers, must be picking up different environmental sounds than bottom fish, and are quite sensitive to external sounds such as birds coming from above.

[0040] At the time, I honestly didn't know whether the horse mackerel was active in response to the sound, or in response to the white light and sound. However, after I conducted three experiments with the horse mackerel - sound only, sound + white light, and light only - I found that although the horse mackerel reacted to sound only and light only, it reacted most actively to the combination of the sound of splashing water + white light.

[0041] Figure 11, like Figure 4, is a photograph showing the movements of a clownfish and a blue-green damselfish when the sound of splashing water (splashing water sounds) was tested. However, while in the experiment in Figure 4, speaker 7 was placed above the water surface H, in the experiment in Figure 11, speaker 7 was submerged in the water. In Figure 11, speaker 7 is located at the position indicated by the arrow. The reference line from speaker 7 is L3. In the water, one clownfish reacted occasionally, but overall the reaction was slow, and it even showed signs of approaching Speaker 7. As the clownfish sometimes reacted underwater, I think they reacted to the sound itself, so I think they just don't like the splashing sound. However, compared to the experiment in air, the effect seemed clearly less.

[0042] Figure 12 is a photograph taken when we confirmed the effectiveness of the deterrent sound produced by the recovery device we developed. A cylindrical plastic container was used as the tank 1. A passage 8 was attached to the side of the container. A speaker 7 was also attached to the lid of the container. A single blue-green damselfish was placed in the container. The blue-green damselfish is located at the position circled in red in Figure 12(a). Figure 12(b) shows the container with the lid closed, and in this state, the sound of water splashing was played from speaker 7 as a repellent sound. In Figure 12(c), the blue-green damselfish is still in the container. In Figure 12(d), the blue-green damselfish has swum to the exit of passage 8, and in Figure 12(e), the blue-green damselfish has safely escaped from the container. The fish succeeded in escaping 10 seconds after the repellent sound started being played from Speaker 7. After trying this several times, we thought it would take about 20 seconds to escape. Therefore, we thought it would be a good idea to operate Pump 5 to collect Microplastics 2 for 3 minutes and stop Pump 5 for 20 seconds and repeat the process.

[0043] Figure 13 shows a photograph of an experiment in which aeration and induction lights were further added. We tried adding aeration to the container used in Figure 12. As shown in Figure 12(a), we placed an air stone in the container and pumped air into it using an aeration pump. We also tried shining a light (guiding light) on passage 8, which is the escape route, as shown in Figure 12(b). When air was sent from the aeration pump to the air stone, the sound from Speaker 7 became louder, and in the dark, the blue-green damselfish quickly escaped without any light guidance. One blue-green damselfish escaped in as little as seven seconds. I tried to reproduce this, and sometimes it took 29 seconds to escape, but it escaped without fail. Furthermore, we discovered that by sending air from the aeration pump while playing sound from Speaker 7, darkening the room, and shining a light on the escape route, we were able to escape in as little as three seconds. As a result, escape took 10 seconds in bright light, and even in the dark, the fastest escape time was 7 seconds by making the sound from Speaker 7 louder by sending air from the aeration pump, and by shining light on the escape route, they were able to escape in just 3 seconds, even in the dark. Furthermore, when aeration was performed alone, without sound being played from Speaker 7, the blue-ringed damselfish remained in the container without escaping. However, when sound and an induction light were added to the aeration, the damselfish immediately escaped. Based on this, we believe that the increase in air (or air bubbles) in the water caused by aeration may have had some effect on how sound was transmitted to the fish, and that the increase in oxygen in the water may have made the fish more energetic and active, and that in this condition, the synergistic effect of the combination of sound and guiding lights may have encouraged the fish to escape. The red circle in Figure 13(b) shows the blue-green damselfish that safely escaped.

[0044] Figure 14 shows the results of an experiment on the swimming speed of a horse mackerel (21 cm) when exposed to light. Figures 14(a-1) to 14(a-5) are taken with light shining on them, while Figures 14(b-1) to 14(b-5) are taken without light shining on them. Each photograph was edited from a video. Figure 14(a-2) is taken one second after Figure 14(a-1), Figure 14(a-3) is taken one second after Figure 14(a-2), and Figure 14(a-5) is taken four seconds after Figure 14(a-1). Figures 14(b-1) to 14(b-5) are also taken at one-second intervals. When light was applied, as shown in Figures 14(a-1) to 14(a-5), the horse mackerel swam more than one lap, but when light was not applied, as shown in Figures 14(b-1) to 14(b-5), the horse mackerel only swam about half a lap.

[0045] Next, I will explain a comparative experiment I conducted on the swimming speed of horse mackerel influenced by sound and light. the purpose The purpose of this experiment is to investigate how sound and light stimuli affect the swimming speed of fish. Specifically, we will compare how fast fish swim with and without sound and light, and to clarify the extent to which sound and light stimuli affect fish movement.

[0046] method To numerically prove the effect of sound and light on fish swimming, we calculate the time it takes for the fish to complete one lap under each condition and analyze the difference. The fish used in the experiment were live horse mackerel. In the dark at night, the horse mackerel was placed in a polystyrene foam (30 cm long x 42 cm wide, 25 cm deep) and its swimming speed was measured under the following three conditions. The experiment began around 6 p.m. on September 22, 2024, when it was getting dark.

[0047] conditions Condition 1 (no sound or light; before sound is released): Observe how the fish swims calmly in the dark, with no sound or light, and quantify how fast it is swimming. Condition 2 (with sound and light): When a specific sound or light is emitted from Speaker 7, the swimming speed is quantified. Condition 3 (no sound or light, state after sound is played): Observe how the fish swims calmly in the dark, without sound or light, and quantify how fast it is swimming. For each condition, we measured how many times the fish swam around the tank within 31, 25, and 26 seconds, and from those results we calculated the average swimming speed of the fish (how many seconds per lap) and compared the effect of the sound. We thought that by deliberately conducting experiments before and after the application of sound and light stimuli (before and after), we would be able to prove the experimental results in a more understandable way.

[0048] result The following results were obtained: In condition 1 (no sound or light, before sound was turned on), the robot completed 4.2 laps in 31 seconds (time per lap = 31 seconds ÷ 4.2 laps = 7.38 seconds). In condition 2 (with sound and light), the participants completed 5.5 laps in 25 seconds (time per lap = 25 seconds ÷ 5.5 laps = 4.55 seconds). In condition 3 (no sound or light, after sound was turned on), the robot completed 3.5 laps in 26 seconds (time per lap = 26 seconds ÷ 3.5 laps = 7.43 seconds). The shorter the time per lap, the faster the horse mackerel is swimming. What we found from the results is that without sound and light, the horse mackerel completed one lap in an average of 7.405 seconds (average of 7.38 and 7.43 seconds). On the other hand, with sound and light, the horse mackerel swam 4.55 seconds per lap, which is (7.405-4.55)÷7.405×100=approximately 38.6% faster. This difference is thought to be due to the fact that sound and light were a clear stimulus to the fish, improving their swimming speed.

[0049] conclusion This experiment demonstrated that horse mackerel swam faster in response to sound and light stimuli. Sound and light stimuli may affect fish behavior and contribute to increasing their underwater movement speed.

[0050] Around the same time, I came across a flyer announcing that researchers at Kitasato University had used green light-emitting diodes (LEDs) to increase the growth rate of flounder and flatfish by 1.6 times, and I thought, "This is it!" I then immediately found and read a number of papers on the color vision of fish, and learned that although there are various theories, green, blue, and red are probably the colors that fish see best. Rockfish (bottom fish) are sensitive to blue and green, but less sensitive to red and yellow. Small surface fish are also sensitive to blue, green, and yellow, and also react to ultraviolet light. The horse mackerel I experimented with: When exposed to white light, it swam fast, and when the light was turned off, it slowed down and even stopped to rest. In this way, we can see that color vision has evolved to suit each individual's habitat. In other words, we found that surface-swimming underwater creatures react more actively and become more wary when illuminated with green, blue, or white LED lights10. However, as mentioned earlier about sound, it is possible that the fish will become accustomed to the sound and no longer be wary.

[0051] From the above, I thought that it might be effective to keep underwater creatures away by flashing a green LED light 10 → white → blue → white → green..., which small fish dislike, followed by white to stimulate them, then flashing it again to a color they dislike, and then white → green → white → blue... in a loop, preventing them from getting used to the light. So, my answer is to keep underwater creatures away in the style shown below, which combines sound technology with light technology. The double effect of randomly looping the sounds of splashing water and the cries of humpback whales, and flashing green LED lights in a loop of 10→white→blue→white→green... to dislike small fish, is to repel aquatic creatures. Also, sound alone is OK, light alone is OK, or sound + light is OK, so that it is not all monotonous, but there is variation so that the underwater creatures do not get used to it. Sound speaker 7 can also be played from a smartphone using Bluetooth (registered trademark). In addition, the LED light 10 may be one that lights up simultaneously with the speaker 7 in conjunction with the speaker 7, or it may be a separate light.

[0052] Through this experiment, it was shown that by using sound and light to scare away small fish, it is possible to efficiently collect microplastics2 while protecting underwater life. The sounds of splashing water, the voices of humpback whales, and green, blue, and white (yellow) LED lights10 were particularly effective, and in the future, we plan to verify this effect for even more types of fish. This device will be a promising means of reducing plastic pollution in the ocean in a sustainable way. [Industrial Applicability]

[0053] In addition to the microplastic collection device, the following uses are possible: (Use near sewage treatment plants) By preventing fish from coming into contact with polluted waters discharged from wastewater treatment plants, we prevent them from ingesting contaminants, thereby protecting the health of the fish and the food chain. (Prevention of radioactive material leakage and environmental protection measures in the event of a disaster) If radioactive or harmful substances flow into the sea or rivers, preventing fish from approaching the area will prevent impacts on the food chain and reduce the risk of contaminants reaching humans through fish. It is also useful as an environmental protection measure in the event of disasters such as tsunamis and earthquakes. (Application in fishing) By introducing this technology to a fishing rod, you can keep small fish away and selectively catch the large fish you are targeting. This is extremely useful for individual fishing activities. (Application to aquaculture and fishing) This technology can be used to prevent certain fish species from negatively impacting the industry at seaweed, oyster, and sea urchin farms, and is also effective as a means of protecting spawning grounds and natural ecosystems. (Harbor and Ship Protection Systems) Sound technology can be used to prevent schools of fish from congregating too close to ports and ships, to improve ship navigation and equipment protection, and to improve the efficiency of port and ship bottom cleaning operations. (Disease prevention in aquariums and aquaculture facilities) This technology can be applied in aquariums and aquaculture facilities to reduce contact between fish using sound and light and prevent the spread of infectious diseases. (Fish school control in diving and tourist areas) By temporarily directing fish to different areas during tourist season, we can reduce stress on the fish caused by tourists and protect the fish ecosystem. (Improvement of fishing efficiency and selective fishing) By incorporating sound and light into fishing nets and traps, it is possible to improve selective fishing techniques that keep small fish away and capture only large fish, which is expected to improve the efficiency of fishing and prevent overfishing. (protection of undersea cables and pipelines) Preventing fish from congregating around cables and pipelines installed on the seabed helps protect infrastructure by preventing damage and corrosion. (Support technology for marine biology research) By guiding schools of fish with sound and light, making it easier for researchers to observe their behavior, it is an effective research tool for controlling fish movements without capturing them. (Fishway guidance in rivers and dams) This will enable efficient guidance of fishways in rivers and dams, optimizing dam operation while protecting ecosystems. (In conjunction with water quality monitoring equipment) By controlling fish behavior using sound and light technology and linking it to water quality monitoring equipment, it is possible to develop new environmental monitoring systems that link the detection of pollution levels with fish behavior. [Explanation of symbols]

[0054] 1 Tank 2. Microplastics 3. Internet 4 Inner Tank 5. Pump 6 Lid 7 Speakers 8 Inhalation passage 9 Discharge passage 10 LED lights H water surface

Claims

1. There is a tank where small fish can swim, Inside the tank is a net that can catch microplastics. A pump draws seawater into the tank and expels the seawater that passes through the net. The pump is installed downstream of the net, A speaker is attached to the underside of the tank lid, The speaker is positioned above the water level in the tank. The pump is periodically stopped at a predetermined timing. When the pump is stopped, a repelling sound is emitted from the speaker, causing the small fish that have entered the tank to escape through the passage that sucks in seawater and into the sea. A microplastic collection device that does not entangle small fish.

2. The repellent sound is the sound of splashing water generated by hitting the water surface about 3 to 8 times per second, and the frequency of the splashing water is between 773 Hz and 13,544 Hz, including irregular frequencies between 1,000 Hz and 11,000 Hz. A microplastics recovery device that does not entangle small fish as described in claim 1.

3. Along with the speaker, an LED light was installed inside the tank. When the pump is stopped, the LED light will blink. A microplastics recovery device that does not entangle small fish as described in claim 1.

4. Aeration is performed when the pump is stopped. A microplastics recovery device that does not entangle small fish as described in claim 1.

Images