System and method for estimating fish numbers

Abstract

The transducer group 10 forms a vertical detection plane in the water of the fish pen by arranging multiple ultrasonic transducers. A reciprocating control unit 101 causes the transducer group's vertical detection plane to rotate forward from a first position in the fish pen to a second position in the fish pen, and then rotate backward from the second position to the first position. A detection control unit 102 detects the number of fish in the fish pen as a detection count based on the transducer group's vertical detection plane for each of the forward rotation and the reverse rotation. A determination control unit 103 determines whether the fish in the fish pen are migratory fish based on the number of forward rotation detections during the forward rotation and the number of reverse rotation detections during the reverse rotation. A first estimation control unit 104 estimates the number of fish in the fish pen if the fish in the fish pen are not migratory fish. If the fish in the fish pen are migratory fish, the calculation control unit 105 calculates the swimming speed of the fish in the fish pen. The second estimation control unit 106 estimates the number of fish in the fish pen.

Description

[Technical Field]

[0001] The present invention relates to a system and a method for estimating the number of fish. [Background technology]

[0002] Conventionally, there are technologies for estimating the number of fish in a fish pen. For example, Japanese Patent Laid-Open Publication No. 7-128446 (Patent Document 1) discloses a method for counting the number of fish by emitting ultrasonic waves into a predetermined area (hereinafter referred to as a fishway) through which fish pass, such as in a fish farm or river, and receiving the waves reflected from the fish. In this method, the reflected waves received from the cross section of the fishway are periodically accumulated to create an ultrasonic fish shadow image showing the progression of fish shadows, and the number of fish is counted by performing image processing on the ultrasonic fish shadow image to identify each fish shadow. This is said to reduce errors caused by turbidity and debris in the water, enabling continuous automatic measurement over a long period of time.

[0003] Furthermore, Japanese Patent Application Laid-Open Publication No. 2021-045102 (Patent Document 2) discloses a fish counting device equipped with a multi-transmission / reception sonar, a fish number calculation unit, a swimming speed calculation unit, and a fish number calculation unit. The multi-transmission / reception sonar has multiple ultrasonic transmission / reception channels arranged with multiple ultrasonic transmitters and receivers. The fish number calculation unit calculates the number of fish passing through the acoustic curtain formed by the multiple ultrasonic transmitters and receivers of the multi-transmission / reception sonar per unit time, and the swimming speed calculation unit calculates the swimming speed of the fish. The fish number calculation unit calculates the total number of fish from the number of fish calculated by the fish number calculation unit and the swimming speed calculated by the swimming speed calculation unit. In addition, a ghost removal process is performed to remove ghosts from the received signal of the multi-transmission / reception sonar. This makes it possible to automatically and accurately count the total number of fish in the fish pen.

[0004] Furthermore, Japanese Patent Application Laid-Open Publication No. 2023-035995 (Patent Document 3) discloses a fish detection device comprising an underwater camera system, an underwater ultrasonic system, a first fish counting unit, and a second fish counting unit. The underwater camera system acquires images of fish swimming underwater, and the underwater ultrasonic system acquires echo data of the fish. The first fish counting unit detects and counts fish in the images, and the second fish counting unit detects and counts fish in occlusion areas where the detected fish are occluded by the echo data. This makes it possible to detect and count fish swimming underwater with high accuracy while suppressing increases in costs.

[0005] Furthermore, Japanese Patent Application Laid-Open Publication No. 2023-035996 (Patent Document 4) discloses a fish detection device comprising an underwater camera system, a fish size calculation unit, an ultrasonic transmitter / receiver, a fish counting unit, and a fish biomass calculation unit. The underwater camera system acquires images of fish swimming underwater, and the fish size calculation unit detects fish in the images and calculates the size of the detected fish based on the images containing the detected fish. The ultrasonic transmitter / receiver transmits a transmission wave toward the fish, receives a reflection of the transmission wave reflected by the fish, and generates a reception signal of the reflection wave. The fish counting unit detects and counts the fish based on the reception signal. The fish biomass calculation unit calculates the fish biomass based on the fish size and the number of fish counted. This allows for accurate calculation of the fish biomass.

[0006] Furthermore, International Publication No. 2019 / 035346 (Patent Document 5) discloses a fish counting device comprising an ultrasonic transmitter / receiver and a processing device. The ultrasonic transmitter / receiver transmits an ultrasonic beam into the water in a first fish pen that can be connected to a second fish pen via a path, has a transmitting / receiving element configured with a single channel, and is positioned so that the ultrasonic beam does not intersect with the path. The processing device outputs a transmission signal to the ultrasonic transmitter / receiver to drive the ultrasonic transmitter / receiver, and obtains the number of fish that pass through the ultrasonic beam and move from the path to the first fish pen based on an echo signal input from the ultrasonic transmitter / receiver that receives the reflected wave. This is said to enable fish counting to be performed easily and at low cost.

[0007] Furthermore, Japanese Patent Laid-Open Publication No. 2015-087160 (Patent Document 6) discloses a searchlight sonar including a transducer, a drive source, a drive control unit, a detection image forming unit, a display control unit, and a measurement unit. The transducer transmits ultrasonic waves underwater and can receive the reflected waves. The drive source operates the transducer to change the direction of transmission of the ultrasonic waves from the transducer, and the drive control unit controls the drive of the drive source to transmit ultrasonic waves to a set transmission area. The detection image forming unit forms a detection image of the transmission area based on a reception signal generated when the transducer receives reflected waves of the ultrasonic waves transmitted from the transducer. The display control unit displays the detection image formed by the detection image forming unit on a display unit. The measurement unit measures the water depth based on a reception signal generated when the transducer receives reflected waves of the ultrasonic waves transmitted directly below from the transducer. In addition, after the transducer has completed transmitting and receiving ultrasonic waves to the transmission area, the drive control unit controls the drive source so that the direction of ultrasonic waves transmitted by the transducer is directly downward, at least while the transducer is rotating from the position where the transmission and reception of ultrasonic waves was completed to the initial position. This allows the detection results of multiple ultrasonic transmission areas to be displayed clearly on the display unit.

[0008] Furthermore, Japanese Patent Laid-Open Publication No. 2017-227564 (Patent Document 7) discloses an underwater detection system including a transducer, a transmission circuit, a reception circuit, a first control unit, a first image generation unit, a second control unit, and a second image generation unit. The transducer has a plurality of transducer elements, and the transmission circuit drives the plurality of transducer elements to transmit a first transmission wave and a second transmission wave having a wider beam width in the vertical direction than the first transmission wave. The reception circuit generates a first reception signal based on a reflected wave of the first transmission wave and a second reception signal based on a reflected wave of the second transmission wave. The first control unit causes the transmission circuit to generate a first drive signal that is the basis of the first transmission wave, and the first image generation unit generates a first image based on the first reception signal output from the reception circuit. The second control unit causes the transmission circuit unit to generate a second drive signal that is the basis of the second transmission wave, and the second image generation unit generates a second image based on the second reception signal output from the reception circuit unit. This makes it possible to reduce the overall system cost while providing a highly convenient underwater detection system for users.

[0009] Furthermore, Japanese Patent Laid-Open Publication No. 2020-134241 (Patent Document 8) discloses a method for monitoring objects moving on water, which includes a scanning sonar, an installation process, a wave transmission and reception process, a generation process, and a recognition process. The scanning sonar includes a wave transmission and reception unit and a rotation unit. The wave transmission and reception unit has a wave transmission unit that transmits a fan-shaped acoustic beam that spreads more in the vertical direction than in the horizontal direction, and a wave reception unit that receives the reflected waves of the acoustic beam, and the rotation unit rotates the wave transmission and reception unit around a vertical axis. The installation process involves installing the scanning sonar underwater, and the wave transmission and reception process involves, with the wave reception unit rotating, the wave transmission unit transmits an acoustic beam toward the water surface, and the wave reception unit receives the reflected waves of the acoustic beam. The generation process continuously generates echo images based on data on the acoustic beams transmitted and received by the transmitter and receiver and the reflected waves of the acoustic beams, and the recognition process recognizes, from the echo images, objects moving on the water that are within the reach of the acoustic beams transmitted from the transmitter. This allows for accurate monitoring of objects moving on the water even in water areas with many obstacles on the water or high water turbidity.

[0010] Furthermore, Japanese Patent Laid-Open Publication No. 2024-77727 (Patent Document 9) discloses a method for counting fish numbers. In this method, multiple measurement areas are formed using a transmitter that transmits multiple ultrasonic waves to an underwater passage frame and multiple receivers that receive the echoes from the transmitters. Next, non-measurement areas are arranged adjacent to the measurement areas in the passage frame, and the number of fish passing through the measurement areas is calculated. Then, the number of fish passing through the entire area, including the non-measurement areas, is predicted from the calculated number of fish passing through the measurement areas. This makes it possible to count the number of passing fish with high accuracy using a simple configuration. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 7-128446 [Patent Document 2] Patent Publication No. 2021-045102 [Patent Document 3] Japanese Patent Publication No. 2023-035995 [Patent Document 4] Japanese Patent Publication No. 2023-035996 [Patent Document 5] International Publication No. 2019 / 035346 [Patent Document 6] Japanese Patent Application Laid-Open No. 2015-087160 [Patent Document 7] Japanese Patent Application Publication No. 2017-227564 [Patent Document 8] Japanese Patent Publication No. 2020-134241 [Patent Document 9] Japanese Patent Application Publication No. 2024-77727 Summary of the Invention [Problem to be solved by the invention]

[0012] As described above, in marine and land-based fish farming, the number of fish in a fish pen is estimated using ultrasound, underwater cameras, scanning sonar, and the like. There are two types of fish: non-migratory fish, such as red sea bream, which move randomly or barely move at all, and migratory fish, such as striped jack and mackerel, which do not stay in one place but move by rotating around a predetermined position. Therefore, even if the number of fish is counted using the same method for both non-migratory and migratory fish, the counted number varies greatly depending on the type of fish. Therefore, unless the method for counting fish is changed depending on the type of fish, the correct number of fish cannot be counted.

[0013] The technology described in Patent Document 1 counts the number of fish in a fishway, so it cannot be applied to counting the number of fish in a fish pen. The technology described in Patent Document 2 estimates the number of migratory fish in a fish pen by calculating the number of fish passing through an acoustic curtain formed by a transducer per unit time and the swimming speed of the fish. However, the number cannot be estimated if the transducer and the fish's migration center are misaligned or if the fish are non-migratory. The technologies described in Patent Documents 3 and 4 use underwater cameras, but they cannot be used when the water in the fish pen is turbid or the fish are densely packed. The technology described in Patent Document 5 estimates the number of fish moving between two fish pens connected by a predetermined route, but cannot estimate the number of fish in a single fish pen. The technologies described in Patent Documents 6 to 8 detect fish in the water by scanning ultrasound, but cannot estimate the number of fish. Furthermore, the method using multi-beam sonar does not have sufficient resolution to count the number of fish of all species. Furthermore, the technology described in Patent Document 9 calculates the total number of fish by determining the number of fish in non-measurement areas from the number of fish in measurement areas, but it is not possible to calculate the number according to the type of fish.

[0014] Therefore, the present invention has been made to solve the above-mentioned problems, and aims to provide a fish number estimation system and method that can use an ultrasonic transmitter / receiver to accurately estimate the number of fish in a fish pen, whether the fish in the pen are non-migratory or migratory. [Means for solving the problem]

[0015] The fish number estimation system according to the present invention comprises a group of ultrasonic transmitters and receivers, a reciprocating control unit, a detection control unit, a determination control unit, a first estimation control unit, a calculation control unit, and a second estimation control unit. The group of ultrasonic transmitters and receivers is rotatably installed in the fish pen about a predetermined rotation axis by arranging the plurality of ultrasonic transmitters and receivers so that the detection areas of the ultrasonic waves irradiated from the plurality of ultrasonic transmitters and receivers form a vertical plane with respect to the water surface of the fish pen. The reciprocating control unit executes a reciprocating motion of the vertical detection plane of the group of ultrasonic transmitters and receivers between a forward rotation from a first position in the fish pen to a second position in the fish pen and a reverse rotation from the second position to the first position. The detection control unit detects the number of fish in the fish pen as a detection count based on the vertical detection plane of the group of ultrasonic transmitters and receivers for each of the forward rotation and the reverse rotation. The determination control unit determines whether the fish in the fish pen are migratory fish based on the number of forward rotation detections during the forward rotation and the number of reverse rotation detections during the reverse rotation. If the determination result shows that the fish in the fish pen are not migratory fish, the first estimation control unit estimates the number of fish in the fish pen based on the number of forward rotation detections and the number of reverse rotation detections. If the determination result shows that the fish in the fish pen are migratory fish, the calculation control unit calculates the swimming speed of the fish in the fish pen using speed calculation means including the number of forward rotation detections, the number of reverse rotation detections, and a predetermined swimming speed table. The second estimation control unit estimates the number of fish in the fish pen based on the calculated swimming speed of the fish and a predetermined fish number table.

[0016] The method for estimating the number of fish according to the present invention is a method for estimating the number of fish in a fish count estimation system equipped with a group of transducers, and comprises a reciprocating control step, a detection control step, a judgment control step, a first estimation control step, a calculation control step, and a second estimation control step. Each control step of the method for estimating the number of fish according to the present invention corresponds to each control unit of the fish count estimation system according to the present invention. [Effects of the Invention]

[0017] According to the present invention, it is possible to use an ultrasonic transmitter / receiver to estimate with high accuracy the number of fish in a fish pen, whether the fish in the pen are non-migratory or migratory. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a functional block diagram illustrating an example of a tail number estimation system according to an embodiment of the present invention. [Figure 2] 2A is a diagram showing an example of a case where multiple ultrasonic transmitters and receivers are arranged in a fan shape, and FIG. 2B is a diagram showing an example of the vertical detection plane of the group of transmitters and receivers in that case. [Figure 3] 3A is a diagram showing an example of a case where multiple ultrasonic transmitters and receivers are arranged in a line, and FIG. 3B is a diagram showing an example of the vertical detection plane of the group of transmitters and receivers in that case. [Figure 4] 1 is a flowchart illustrating an example of a method for estimating the number of tails according to an embodiment of the present invention. [Figure 5] FIG. 5A shows an example of a group of transducers installed in the center of a fish pen, and FIG. 5B shows an example of a group of transducers rotated forward and backward. [Figure 6] FIG. 6A shows an example of a case where the fish in the fish tank are non-migratory and the transducer group is rotated in the forward direction, and FIG. 6B shows an example of the number of detections for each divided area during forward rotation. [Figure 7] FIG. 7A shows an example of a case where the fish in the fish tank are non-migratory and the transducer group is rotated in reverse, and FIG. 7B shows an example of the number of detections per divided area when the transducer group is rotated in reverse. [Figure 8] FIG. 8A shows an example of a case where the fish in the fish tank are migratory fish and the transducer group is rotated in the forward direction, and FIG. 8B shows an example of the number of detections for each divided area during forward rotation. [Figure 9] 9A shows an example of a case where the fish in the fish tank are migratory fish and the transducer group is rotated in reverse, and FIG. 9B shows an example of the number of detections for each divided area when the transducer group is rotated in reverse. [Figure 10] 10A is a diagram showing an example of a swimming speed table and a graph, and FIG. 10B is a diagram showing an example of a fish number table and a graph. [Figure 11]FIG. 11A shows an example of a case where a group of transducers is installed at one end of a fish pen, and FIG. 11B shows an example of a case where the group of transducers is rotated forward and backward. [Figure 12] 12A is a diagram showing an example of a case where a group of transducers is rotated forward, and FIG. 12B is a diagram showing an example of the number of detections for each divided area during forward rotation. [Figure 13] 13A is a diagram showing an example of a case where a group of transducers is rotated in the reverse direction, and FIG. 13B is a diagram showing an example of the number of detections for each divided area during the reverse rotation. [Figure 14] Figure 14A shows an example of dividing the area into two regions, one proximal and one distal to the migration center of the migratory fish from the group of transducers, and Figure 14B shows an example of dividing the area into four regions, one proximal to the right side, one proximal to the migration center of the migratory fish from the group of transducers, one proximal to the left side, one distal to the right side, and one distal to the left side from the group of transducers. [Figure 15] FIG. 15A shows an example of a graph of a swimming speed table divided into two divided regions, and FIG. 15B shows an example of a graph of a fish count table divided into two divided regions. [Figure 16] FIG. 16A shows an example of a fish number estimation system according to an embodiment of the present invention when applied to marine aquaculture, and FIG. 16B shows an example of a system when applied to land-based aquaculture. [Figure 17] 17A is a diagram showing an example of a simulation of non-migratory fish in Example 1, and FIG. 17B is a diagram showing an example of a simulation of migratory fish in Example 1. FIG. [Figure 18] 18A shows an example of a graph of a swimming speed table and a graph of a fish count table in Example 1, and FIG. 18B shows an example of moving the position of the rotation center of the vertical detection plane to the position of the rotation center of a migratory fish. [Figure 19] 19A is a diagram showing an example of a simulation of migratory fish in Example 2, and FIG. 19B is a diagram showing an example of a graph of a swimming speed table and a graph of a fish number table in Example 2. FIG. [Figure 20]FIG. 20A shows an example of a case where the position of the center of rotation of the vertical detection surface is converted in a simulation of migratory fish in Example 2, and FIG. 20B shows an example of the number of detections for each divided area in forward and reverse rotation before and after converting the position of the center of rotation of the vertical detection surface. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings to help understand the present invention. Note that the following embodiment is an example of the present invention, and is not intended to limit the technical scope of the present invention.

[0020] 1, a fish population estimation system 1 according to an embodiment of the present invention comprises a transmitter / receiver group 10, a rotating unit 20, and a control unit 30. First, the transmitter / receiver group 10 comprises a plurality of ultrasonic transmitters / receivers 10a, and by arranging the plurality of ultrasonic transmitters / receivers 10a so that the detection areas of the ultrasonic waves irradiated from the plurality of ultrasonic transmitters / receivers 10a form a vertical plane with respect to the water surface of the fish pen B, a vertical detection plane A is formed in the water of the fish pen B.

[0021] Here, there is no particular limitation on the arrangement of the ultrasonic transmitter / receivers 10a, but for example, as shown in Fig. 3A, multiple ultrasonic transmitter / receivers 10a can be arranged in a 90-degree fan shape at predetermined intervals from below to the horizontal plane. Here, a fan-shaped frame 10b is prepared in advance, and multiple ultrasonic transmitters / receivers 10a are attached one by one to the arc portions of the fan-shaped frame 10b.

[0022] The group of transducers 10 is rotatably installed on a predetermined rotation axis 20a in the fish pen B. The rotation axis 20a of the rotating unit 20 is disposed perpendicular to the horizontal direction of the group of transducers 10 and along a direction extending downward from the center of the fan-shaped group of transducers 10. The group of transducers 10 can be rotated horizontally by the rotating unit 20 rotating the rotation axis 20a.

[0023] Here, the ultrasonic transmitter / receivers 10a may be arranged in a single row, or may be arranged alternately in two rows depending on the size of the ultrasonic transmitter / receivers 10a, as shown in Fig. 3A, which makes it possible to widen the ultrasonic wave detection area.

[0024] 3B, the multiple ultrasonic transmitters / receivers 10a arranged in a fan shape transmit ultrasonic waves at different arrangement angles α relative to the horizontal direction of the transmitter / receiver group 10. As a result, the detection areas of the multiple ultrasonic waves as a whole form a detection plane A perpendicular to the horizontal direction of the transmitter / receiver group 10. Furthermore, since the ultrasonic waves of the ultrasonic transmitter / receiver 10a have a predetermined directivity angle β, the arrangement angle α of the ultrasonic transmitter / receiver 10a is appropriately set taking into account the directivity angle β of the ultrasonic waves. Furthermore, the ultrasonic transmitter / receiver 10a detects the distance R from the ultrasonic transmitter / receiver 10a to the target based on the reflection time of the transmitted ultrasonic waves.

[0025] Furthermore, regarding the arrangement of the ultrasonic transmitter / receivers 10a, for example, multiple ultrasonic transmitter / receivers 10a can be arranged linearly from top to bottom at a predetermined interval, as shown in Fig. 4A. Here, a linear frame 10b is prepared in advance, and the linear frame 10b is composed of a first long rod and a second long rod, and multiple ultrasonic transmitter / receivers 10a are attached one by one between the first long rod and the second long rod.

[0026] Furthermore, the rotation axis 20a of the rotating unit 20 is arranged along the longitudinal direction of the first long rod, and by rotating the rotation axis 20a of the rotating unit 20, the group of transducers 10 can be rotated horizontally.

[0027] 4B, the ultrasonic transmitters and receivers 10a arranged in a line are spaced apart at a predetermined interval d10a in a direction perpendicular to the horizontal direction of the transmitter and receiver group 10, and each transmits ultrasonic waves along the horizontal direction of the transmitter and receiver group 10. As a result, the detection areas of the multiple ultrasonic waves as a whole form a detection plane A perpendicular to the horizontal direction of the transmitter and receiver group 10. As described above, the ultrasonic waves of the ultrasonic transmitter and receiver 10a have a predetermined directivity angle β, and therefore the mutual interval d10a between the ultrasonic transmitters and receivers 10a is set appropriately in consideration of the directivity angle β of the ultrasonic waves.

[0028] Here, the configuration of the ultrasonic transmitter / receiver 10a is not particularly limited, and examples thereof include ultrasonic vibrators using piezoelectric ceramics. Furthermore, the configuration of the rotating unit 20 is not particularly limited, and examples thereof include a rotary motor. The rotating unit 20 is installed on the upper surface of the transducer group 10, and the rotation axis 20a of the rotating unit 20 is attached along a vertical direction relative to the upper surface of the transducer group 10. By installing the multiple ultrasonic transmitters / receivers 10a of the transducer group 10 in the water of the fish pen B and arranging the vertical detection plane A formed by the transducer group 10 vertically relative to the water surface of the fish pen, the vertical detection plane A can be rotated horizontally relative to the water surface of the fish pen B.

[0029] Furthermore, the control unit 30 is configured, for example, with a CPU (GPU), a dedicated circuit, etc., and has a built-in CPU, ROM, RAM, etc. (not shown), and the CPU uses, for example, the RAM as a work area to execute programs stored in the ROM, etc. Furthermore, for each control unit described later, the CPU executes a program to realize the function of that control unit.

[0030] Next, the configuration and execution procedure according to an embodiment of the present invention will be described with reference to Fig. 1 and Fig. 4 to Fig. 10. First, a case will be described in which the transducer group 10 and the rotating unit 20 are installed in the center of the fish pen B. The user carries the fish number estimation system 1 to the fish pen B where the number of fish is to be counted, and installs the transducer group 10 in the center Ba of the fish pen B so that the vertical detection plane A of the transducer group 10 faces the water surface of the fish pen B, as shown in Fig. 5A, for example.

[0031] Here, there is no particular limitation on the installation position of the transducer group 10, but for example, if the fish pen B is cylindrical, the central part Ba of the fish pen B will be at or near the center of the cylinder. Then, the user installs the rotation axis 20a of the rotating part 20 of the transducer group 10 along the vertical direction of the central part Ba of the fish pen B, so that the vertical detection plane A of the transducer group 10 is flush with the water surface of the fish pen B.

[0032] Once the user has completed the installation of the transducer group 10, the user then activates the control unit 30 of the fish population estimation system 1 and sends a command to start measurement to the control unit 30. The reciprocating control unit 101 of the control unit 30 then receives the command to start measurement and performs a reciprocating movement of the vertical detection plane A of the transducer group 10 between a forward rotation from a first position P1 of the fish pen B to a second position P2 of the fish pen B and a reverse rotation from the second position P2 to the first position P1.

[0033] Here, there is no particular limitation on the execution method of the reciprocation control unit 101. For example, as shown in FIG. 5B, if the fish cage B has a cylindrical shape, a position along the left side of the center Ba of the fish cage B is set as a first position P1, and the same position is set as a second position P2. Here, the position of the fish cage B means a position that forms one plane in a direction perpendicular to the water surface of the fish cage B. Then, after placing the vertical detection plane A at the first position P1, the rotation unit 20 controls the rotation unit 20 to rotate the transducer group 10. Then, as shown in FIG. 5B, the reciprocation control unit 101 rotates the vertical detection plane A of the transducer group 10 counterclockwise when viewed from above the fish cage B from the first position P1 to the second position P2. This is referred to as forward rotation. Next, the reciprocation control unit 101 rotates the vertical detection plane A of the transducer group 10 clockwise when viewed from above the fish cage B from the second position P2 to the first position P1. This is referred to as reverse rotation.

[0034] The rotation angle θ of the transducer group 10 controlled by the reciprocating control unit 101 is 360 degrees from the first position P1 for forward rotation and 360 degrees from the second position P2 for reverse rotation, each of which corresponds to one rotation. There is no particular limitation on the rotation speed of the transducer group 10 controlled by the reciprocating control unit 101, but it is set appropriately taking into consideration the swimming speed of the fish in the fish tank B, and specifically, it can be set within the range of 0.5 rpm to 3.0 rpm.

[0035] Furthermore, while the reciprocating control unit 101 is performing forward and reverse rotations, the detection control unit 102 of the control unit 30 emits ultrasonic waves from the multiple ultrasonic transmitters and receivers 10a of the transmitter and receiver group 10 to form a vertical detection plane A, and detects the number of fish in the fish tank B as the detection count based on the vertical detection plane A of the transmitter and receiver group 10 for each of the forward and reverse rotations.

[0036] Here, there is no particular limitation on the number of pings when the detection control unit 102 transmits ultrasonic waves from the ultrasonic transmitter / receiver 10a. Here, the number of pings refers to the number of times that it takes for the ultrasonic waves transmitted from the ultrasonic transmitter / receiver 10a to be reflected by the target (fish) and return. In the present invention, since the transmitter / receiver group 10 is rotated, the number of pings is appropriately set taking into consideration the rotation speed of the transmitter / receiver group 10, and specifically, can be set within a range of 10 to 50 pings per second. Note that, in the following description, the number of detections detected by one ultrasonic transmitter / receiver 10a of the transmitter / receiver group 10 located immediately below the water surface of the fish preserve B will be explained as an example.

[0037] Specifically, the reciprocating control unit 101 rotates the vertical detection plane A of the transducer group 10 in the forward direction via the rotation unit 20 (FIG. 4: S101). At the same time, the detection control unit 102 radiates ultrasonic waves from each ultrasonic transmitter / receiver 10a of the transducer group 10 to form the vertical detection plane A (FIG. 4: S102). While the reciprocating control unit 101 rotates the transducer group 10 in the forward direction, the detection control unit 102 detects the number of fish passing through the vertical detection plane A as the forward rotation detection number Na (FIG. 4: S103).

[0038] 6A, the detection control unit 102 increases the rotation angle θ (degrees) of the transducer group 10 from the first position P1 from 0 degrees, and defines the region where the rotation angle θ is 0 to 90 degrees as divided region S1, the region where the rotation angle θ is 90 to 180 degrees as divided region S2, the region where the rotation angle θ is 180 to 270 degrees as divided region S3, and the region where the rotation angle θ is 270 to 360 degrees as divided region S4. Then, the detection control unit 102 detects the number of detections for each of the divided regions S1 to S4 divided by the rotation angle θ in the forward rotations Na1 to Na4.

[0039] 6B, the detection control unit 102 can detect the number of detections N in the forward rotation Na1 to Na4, with the vertical axis representing the number of detections N and the horizontal axis representing the distance R at each detection interval Rd. Here, if the fish in the fish pen B are non-migratory fish, the number of detections N for each divided area S1-S4 in the forward rotation Na1 to Na4 will be roughly the same. Therefore, the detection control unit 102 adds up all of the number of detections N for each divided area S1-S4 in the forward rotation Na1 to Na4 and detects this as the forward rotation detection number Na.

[0040] Now, when the detection control unit 102 detects the forward rotation detection number Na, the reciprocating control unit 101 then reversely rotates the vertical detection plane A of the transducer group 10 via the rotation unit 20 (FIG. 4: S104). At the same time, the detection control unit 102 configures the vertical detection plane A of the transducer group 10 in the same manner as described above (FIG. 4: S105), and detects the number of fish detected passing through the vertical detection plane A as the reverse rotation detection number Nb (FIG. 4: S106).

[0041] 7A, the detection control unit 102 reduces the rotation angle θ of the transducer group 10 from the first position P1 from 360 degrees, and defines the region where the rotation angle θ is 360 degrees to 270 degrees as divided region S4, the region where the rotation angle θ is 270 degrees to 180 degrees as divided region S3, the region where the rotation angle θ is 180 degrees to 90 degrees as divided region S2, and the region where the rotation angle θ is 90 degrees to 0 as divided region S1. Then, the detection control unit 102 detects the number of detections for each of the divided regions S1-S4 divided by the rotation angle θ in the reverse rotations Nb1 to Nb4.

[0042] 7B, the detection control unit 102 can detect the number of detections N in the reverse rotation Nb1 to Nb4, as described above, with the vertical axis representing the number of detections N and the horizontal axis representing the distance R at each detection interval Rd. Here, if the fish in the fish pen B are non-migratory fish, the number of detections N for each divided area S1-S4 in the reverse rotation Nb1 to Nb4 will be roughly the same as the number of detections N for each divided area S1-S4 in the forward rotation Na1 to Na4. Therefore, the detection control unit 102 adds up all of the number of detections N for each divided area S1-S4 in the reverse rotation Nb1 to Nb4 and detects this sum as the reverse rotation detection number Nb.

[0043] Now, if the fish in the fish tank B are migratory fish, for example, as shown in Figure 8A, if the migratory fish migrate counterclockwise around the center Ba of the fish tank B when viewed from above, the detection control unit 102 detects the number of detections N for each divided area S1-S4 in the forward rotation Na1 to Na4.

[0044] 8B, the number of detections N for each divided area S1-S4 in the forward rotation Na1-Na4 changes with the detection interval Rd of the divided area S1-S4. For example, the number of detections N for the first detection interval Rd for each divided area S1-S4 is close to zero. This is because there are almost no migratory fish in the center of their migration. Furthermore, if the forward rotation is in the opposite direction to the migratory direction of the migratory fish, the number of detections N for the other detection intervals Rd for each divided area S1-S4 increases significantly. This is because the forward rotation of the transducer group 10 rotates the vertical detection plane A of the transducer group 10 in the direction in which it collides with the migratory fish, thereby increasing the overall number of detections N.

[0045] On the other hand, in the case of reverse rotation, as shown in FIG. 9A, when the detection control unit 102 detects the number of detections N for each of the divided regions S1-S4 in the reverse rotation Nb1-Nb4, the number of detections N in the first detection interval Rd for each of the divided regions S1-S4 approaches zero, as shown in FIG. 9B, as described above. Furthermore, when the reverse rotation is in the same direction as the migratory direction of the migratory fish, the number of detections N in the other detection intervals Rd for each of the divided regions S1-S4 in the reverse rotation Nb1-Nb4 is significantly reduced compared to the number of detections N in the forward rotation Na1-Na4. This is because the reverse rotation of the transducer group 10 rotates the vertical detection plane A of the transducer group 10 in a direction that pursues the migratory fish, thereby reducing the overall number of detections N. The present invention utilizes this difference in the number of detections between non-migratory and migratory fish to distinguish between non-migratory and migratory fish and accurately estimate the number of fish.

[0046] Now, in S106, when the detection control unit 102 detects the number of forward rotation detections Na and the number of reverse rotation detections Nb, the judgment control unit 103 of the control unit 30 then determines whether the fish in the fish tank B are migratory fish or not based on the number of forward rotation detections Na and the number of reverse rotation detections Nb (Figure 2: S107).

[0047] Here, the determination control unit 103 is not particularly limited in its determination method, but for example, the determination control unit 103 calculates a determination ratio by dividing a first detection number N1, which is a larger detection number out of the forward rotation detection number Na and the reverse rotation detection number Nb, by a second detection number N2, which is a smaller detection number (N1 / N2). Next, the determination control unit 103 determines whether the calculated determination ratio is within a predetermined migration range including 1.0.

[0048] Here, the migration range is not particularly limited, but can be, for example, a range of 0.9 to 1.1. Furthermore, when the determination ratio is 1.0, it means that the forward rotation detection number Na and the reverse rotation detection number Nb are the same, which means that the fish is a non-migratory fish, as described above. Furthermore, even if the fish is a non-migratory fish, the forward rotation detection number Na and the reverse rotation detection number Nb may fluctuate slightly due to various factors, so by specifying a predetermined migration range that includes 1.0, it is possible to accurately determine that the fish is a non-migratory fish.

[0049] If the judgment result shows that the judgment ratio is within the migratory range, the judgment control unit 103 judges that the fish in the fish tank B are not migratory fish (Figure 2: S107: NO), and the first estimation control unit 104 of the control unit 30 estimates the number of fish in the fish tank B based on the number of forward rotation detections Na and the number of reverse rotation detections Nb (Figure 2: S108).

[0050] Here, there are no particular limitations on the estimation method used by the first estimation control unit 104, but as described above, if the fish are non-migratory, the forward rotation detection count Na and the reverse rotation detection count Nb will be approximately the same, so the first estimation control unit 104 may, for example, calculate and estimate the average value {(Na+Nb) / 2} of the forward rotation detection count Na and the reverse rotation detection count Nb as the number of fish tails. This makes it possible to easily estimate the number of fish tails if the fish are non-migratory.

[0051] On the other hand, in S107, if the judgment result shows that the judgment ratio is not within the migration range, that is, if the judgment ratio is outside the migration range, the judgment control unit 103 judges that the fish in the fish pen B are migratory fish (Figure 2: S107: YES), and the calculation control unit 105 of the control unit 30 calculates the swimming speed Vf of the fish in the fish pen B using a speed calculation means including the forward rotation detection number Na, the reverse rotation detection number Nb, and a predetermined swimming speed table (Figure 2: S201).

[0052] Here, the calculation method of the calculation control unit 105 is not particularly limited. For example, the calculation control unit 105 refers to a swimming speed table 40 stored in advance in a predetermined memory. Here, as shown in FIG. 10A , the swimming speed table 40 stores a determination ratio N1 / N2 (41) and a fish swimming speed Vf (m / s) (42) in association with each other. The calculation control unit 105 compares the determination ratio N1 / N2 calculated from the forward rotation detection number Na and the reverse rotation detection number Nb with the determination ratio N1 / N2 (41) in the swimming speed table 40, and obtains the fish swimming speed Vf (42) associated with the compared determination ratio N1 / N2 (41), thereby calculating the swimming speed Vf of the fish in the cage B. This makes it possible to easily calculate the swimming speed Vf of the fish in the cage B.

[0053] 10A, the swimming speed table 40 may be a graph with the vertical axis representing the swimming speed Vf of the fish and the horizontal axis representing the judgment ratio N1 / N2. As will be described later, it has been found through simulation software that the judgment ratio N1 / N2 and the swimming speed Vf of the fish are in a nearly inversely proportional decreasing relationship. Therefore, the swimming speed table 40 may be configured as a graph showing the inversely proportional decreasing relationship between the judgment ratio N1 / N2 and the swimming speed Vf of the fish. The calculation control unit 105 may then calculate the swimming speed Vf of the fish from the swimming speed table 40 graph by substituting the calculated judgment ratio N1 / N2 into the swimming speed table 40 graph.

[0054] As described above, the speed calculation means is not limited to the swimming speed table 40, but may also be, for example, an underwater camera or the transducer group 10. For example, an underwater camera may be installed in advance in the fish pen B as the speed calculation means, and the calculation control unit 105 may use the underwater camera to take images of the fish in the fish pen B and analyze the taken images to calculate the swimming speed Vf of the fish. Alternatively, the transducer group 10 may be used as the speed calculation means, and the calculation control unit 105 may calculate the swimming speed Vf of the fish based on the number of pings detected by the ultrasonic transducer 10a of the transducer group 10.

[0055] Now, once the calculation control unit 105 calculates the fish swimming speed Vf, the second estimation control unit 106 of the control unit 30 estimates the number of fish in the fish pen B based on the calculated fish swimming speed Vf and a predetermined fish number table (Figure 2: S202).

[0056] Here, the estimation method of the second estimation control unit 106 is not particularly limited, but the second estimation control unit 106 refers to a fish number table 50 stored in advance in a predetermined memory. Here, as shown in FIG. 10B , the fish number table 50 stores the fish swimming speed Vf (m / s) (51) and a division value Nt / (N1 / N2) (52) obtained by dividing the total number of fish Nt by the determination ratio N1 / N2, in association with each other. The second estimation control unit 106 then compares the calculated fish swimming speed Vf (m / s) with the fish swimming speed Vf (m / s) (51) in the fish number table 50, and obtains the division value Nt / (N1 / N2) (52) associated with the compared fish swimming speed Vf (m / s) (51). Then, the second estimation control unit 106 multiplies the obtained Nt / (N1 / N2) (52) by the previously calculated determination ratio N1 / N2 to obtain the multiplied value Nt, and estimates it as the number of fish in the fish pen B. This makes it possible to easily calculate the number of fish Nt in the fish pen B.

[0057] Furthermore, the form of the fish number table 50 is not particularly limited. For example, as shown in FIG. 11B, the fish number table 50 may be a graph in which the vertical axis represents the division value Nt / (N1 / N2) and the horizontal axis represents the fish swimming speed Vf. Here, as will be described later, it has been found using predetermined simulation software that there is a predetermined increasing relationship between the fish swimming speed Vf and the division value Nt / (N1 / N2). Therefore, the fish number table 50 may be configured as a graph showing the increasing relationship between the fish swimming speed Vf and the division value Nt / (N1 / N2), and the second estimation control unit 106 may calculate the division value Nt / (N1 / N2) from the fish number table 50 graph by substituting the calculated fish swimming speed Vf into the fish number table 50 graph.

[0058] As described above, the present invention makes it possible to use ultrasonic transmitters to accurately estimate the number of fish in cage B, regardless of whether the fish in the cage are non-migratory or migratory. In the above description, the number of detections N for one ultrasonic transmitter / receiver 10a of the transmitter / receiver group 10 is the number of detections N in two dimensions in the horizontal direction of cage B. However, this is not limited to this, and the same applies to the number of detections N for each ultrasonic transmitter / receiver 10a of the transmitter / receiver group 10. Therefore, the number of detections N in two dimensions in the horizontal direction and one dimension in the depth direction of cage B can be detected using the number of detections N in the depth direction of cage B, and the total number of detections N in three dimensions of cage B can be detected. Thus, the total number of fish in cage B can be estimated by adding up the number of detections N for each ultrasonic transmitter / receiver 10a.

[0059] In the above description, the case where the transducer group 10 and the rotating unit 20 are installed in the center of the cage B has been described, but there are also cases where the transducer group 10 and the rotating unit 20 cannot be installed in the center of the cage B. In such cases, the present invention can accurately estimate the number of fish in the cage B even if the transducer group 10 and the rotating unit 20 are installed at one end of the cage B.

[0060] First, the user installs the group of transducers 10 at one end Bb of the cage B so that the vertical detection plane A of the group of transducers 10 faces the water surface of the cage B, as shown in FIG. 11A.

[0061] Here, there is no particular limitation on the installation position of the transducer group 10, but for example, if the fish cage B is cylindrical, one end Bb of the fish cage B will be on or near the inner surface of the cylinder. Then, the user installs the rotation axis 20a of the rotating unit 20 of the transducer group 10 along the vertical direction of one end Bb of the fish cage B, so that the vertical detection surface A of the transducer group 10 is flush with the water surface of the fish cage B.

[0062] Next, when the user sends an instruction to start measurement to the control unit 30, the reciprocating control unit 101 of the control unit 30 performs a forward rotation from a first position P1 of the fish tank B to a second position P2 of the fish tank B, and a reverse rotation from the second position P2 to the first position P1, relative to the vertical detection plane A of the transducer group 10.

[0063] 11B, for example, a position to the upper right from one end Bb of the cage B is set as a first position P1, and a position to the upper left from one end Bb of the cage B is set as a second position P2. The reciprocating control unit 101 also rotates the vertical detection surface A of the transducer group 10 counterclockwise when viewed from above the cage B from the first position P1 to the second position P2. This is called forward rotation. The reciprocating control unit 101 also rotates the vertical detection surface A of the transducer group 10 clockwise when viewed from above the cage B from the second position P2 to the first position P1. This is called reverse rotation.

[0064] Here, the rotation angle θ of the transducer group 10 by the reciprocating control unit 101 is, as shown in FIG. 11B, approximately 120 degrees for forward rotation from the first position P1 to the second position P2, and approximately 120 degrees for reverse rotation from the second position P2 to the first position P1. However, when the transducer group 10 is installed at one end Bb of the fish pen B, it is preferable to set the rotation angle θ within the range of, for example, 100 degrees to 180 degrees, depending on the shape and size of the fish pen B, so that the entire fish pen B can be measured as much as possible.

[0065] Specifically, the reciprocating control unit 101 rotates the vertical detection plane A of the transducer group 10 in the forward direction via the rotation unit 20 (FIG. 4: S101). At the same time, the detection control unit 102 configures the vertical detection plane A of the transducer group 10 (FIG. 4: S102), and the detection control unit 102 detects the number of fish passing through the vertical detection plane A as the forward rotation detection number Na (FIG. 4: S103).

[0066] 12A, for example, the detection control unit 102 increases the rotation angle θ of the transducer group 10 from the first position P1 from 0 degrees, and defines a region of forward rotation Na1 where the rotation angle θ is 0 to 30 degrees as divided region S1, a region of forward rotation Na2 where the rotation angle θ is 30 to 60 degrees as divided region S2, a region of forward rotation Na3 where the rotation angle θ is 60 to 90 degrees as divided region S3, and a region of forward rotation Na4 where the rotation angle θ is 90 to 120 degrees as divided region S4. Then, the detection control unit 102 detects the number of detections at each detection interval Rd for each of the divided regions S1 to S4 in the forward rotation Na1 to Na4.

[0067] 12B, the detection control unit 102 can detect the number of detections for each of the divided regions S11-S14, S21-S24, S31-S34, and S41-S44, which are divided by the rotation angle θ and the detection interval Rd during forward rotation Na1-Na4. If the fish in the fish preserve B are migratory fish, the number of detections N for a specific divided region (e.g., S33) among the number of detections N for each of the divided regions S11-S14, S21-S24, S31-S34, and S41-S44 will be close to zero, corresponding to the center of migration of the migratory fish. Furthermore, because the direction of the reverse rotations Nb4-Nb1 is close to the opposite direction to the migration direction of the migratory fish, the overall number of detections N will generally be high.

[0068] Now, when the detection control unit 102 detects the forward rotation detection number Na, the reciprocating control unit 101 then reversely rotates the vertical detection plane A of the transducer group 10 via the rotation unit 20 (FIG. 4: S104). At the same time, the detection control unit 102 configures the vertical detection plane A of the transducer group 10 in the same manner as described above (FIG. 4: S105), and detects the number of fish detected passing through the vertical detection plane A as the reverse rotation detection number Nb (FIG. 4: S106).

[0069] 13A, the detection control unit 102 reduces the rotation angle θ of the transducer group 10 from the first position P1 from 120 degrees, and defines the region of reverse rotation Nb4 where the rotation angle θ is 120 degrees to 90 degrees as divided region S4, the region of reverse rotation Nb3 where the rotation angle θ is 90 degrees to 60 degrees as divided region S3, the region of reverse rotation Nb2 where the rotation angle θ is 60 degrees to 30 degrees as divided region S2, and the region of reverse rotation Nb1 where the rotation angle θ is 30 degrees to 0 as divided region S1. Then, the detection control unit 102 detects the number of detections at each detection interval Rd for each of the divided regions S1 to S4 in the reverse rotation Nb4 to Nb1.

[0070] 13B, the detection control unit 102 can detect the number of detections N for each of the divided regions S11-S14, S21-S24, S31-S34, and S41-S44, which are divided by the rotation angle θ and the detection interval Rd, in the reverse rotation Nb4-Nb1. If the fish in the fish preserve B are migratory fish, the number of detections N for a given divided region (e.g., S21, S31) among the number of detections N for each of the divided regions S11-S14, S21-S24, S31-S34, and S41-S44 will be close to zero, corresponding to the center of migration of the migratory fish. Furthermore, because the direction of the reverse rotation Nb4-Nb1 is close to the same direction as the migratory direction of the migratory fish, the overall number of detections N will be generally smaller than that for the forward rotation Na1-Na4.

[0071] Now, when the detection control unit 102 detects the number of forward rotation detections Na and the number of reverse rotation detections Nb, the judgment control unit 103 judges whether the fish in the fish tank B are migratory fish or not based on the number of forward rotation detections Na and the number of reverse rotation detections Nb (Figure 2: S107).

[0072] Here, as described above, the determination control unit 103 may calculate the determination ratio N1 / N2 by setting the sum of the detection numbers N for each of the divided areas S11-S14, S21-S24, S31-S34, and S41-S44 in the forward rotation Na1-Na4 as the forward rotation detection number Na, and the sum of the detection numbers N for each of the divided areas S11-S14, S21-S24, S31-S34, and S41-S44 in the reverse rotation Nb1-Nb4 as the reverse rotation detection number Nb, and determine whether the fish in the cage B are migratory fish or not. Here, if the transducer group 10 and the rotating unit 20 are installed at one end of the cage B, the detection number N for each of the divided areas S11-S14, S21-S24, S31-S34, and S41-S44 will vary depending on the migration center of the migratory fish, as described above.

[0073] 14A , the determination control unit 103 estimates that the divided area where the number of detections N is close to zero (around S23 and S33) is the center of rotation C of the migratory fish, and calculates, in forward rotation Na1-Na4, the sum of all the numbers of detections N for each of the divided areas S11-S14, S21-S23, S31-S33, and S14-S44 in the proximal area from the transducer group 10 to the center of rotation C of the migratory fish as the proximal number of detections Naa, and calculates, in forward rotation Na1-Na4, the sum of all the numbers of detections N for each of the divided areas S24 and S34 in the distal area from the center of rotation C of the migratory fish to the far side as the distal number of detections Nba.

[0074] Next, the determination control unit 103 calculates the proximal reverse rotation detection number Nba by adding up all of the detection numbers N for each of the proximal divided regions S11-S14, S21-S23, S31-S33, and S14-S44 in the reverse rotation Nb1-Nb4, and calculates the distal reverse rotation detection number Nbb by adding up all of the detection numbers N for each of the distal divided regions S24 and S34 in the reverse rotation Nb1-Nb4. The determination control unit 103 then calculates a first determination ratio N1 / N2 based on the proximal forward rotation detection number Naa and the proximal reverse rotation detection number Nba, and a second determination ratio N1 / N2 based on the distal forward rotation detection number Nba and the distal reverse rotation detection number Nbb, and uses each determination ratio N1 / N2 to determine whether the fish in the fish preserve B are migratory fish. Here, the first judgment ratio N1 / N2 and the second judgment ratio N1 / N2 are judgment ratios that take into account the center of rotation C of the migratory fish, so if either the first judgment ratio N1 / N2 or the second judgment ratio N1 / N2 is outside the migration range, the judgment control unit 103 can judge that the fish in the fish tank B are migratory fish.

[0075] Furthermore, the determination control unit 103 divides the divided area into four when calculating the number of forward rotation detections Na and the number of reverse rotation detections Nb, thereby determining with high accuracy whether the fish in the cage B are migratory fish or not. For example, as shown in FIG. 14B, the judgment control unit 103 calculates the proximal right positive rotation detection number Naar by adding up all the detection numbers N for each of the divided areas S31-S33 and S41-S44 on the proximal side and on the right side of the transducer group 10 during forward rotation Na1-Na4, calculates the proximal left positive rotation detection number Naal by adding up all the detection numbers N for each of the divided areas S11-S14 and S21-S23 on the proximal side and on the left side of the transducer group 10 during forward rotation Na1-Na4, calculates the distal right positive rotation detection number Nabr by adding up all the detection numbers N for each of the divided areas S34 on the distal side during forward rotation Na1-Na4, and calculates the distal left positive rotation detection number Nabl by adding up all the detection numbers N for each of the divided areas S24 on the distal side during forward rotation Na1-Na4. Similarly, the judgment control unit 103 calculates the proximal right reverse rotation detection number Nbar by adding up the total number of detections N on the proximal side and for each of the right-side divided areas S31-S33 and S41-S44 in the reverse rotation Nb1-Nb4, calculates the proximal left reverse rotation detection number Nbal by adding up the total number of detections N on the proximal side and for each of the divided areas S11-S14 and S21-S23 on the left side of the transducer group 10 in the reverse rotation Nb1-Nb4, calculates the distal right reverse rotation detection number Nbbr by adding up the total number of detections N on the distal side and for each of the right-side divided areas S34 in the reverse rotation Nb1-Nb4, and calculates the distal left forward rotation detection number Nbbl by adding up the total number of detections N on the distal side and for each of the left-side divided areas S24 in the reverse rotation Nb1-Nb4.The determination control unit 103 then calculates a first determination ratio N1 / N2 based on the number of detected proximal right-side forward rotations Naar and the number of detected proximal right-side reverse rotations Nbar, a second determination ratio N1 / N2 based on the number of detected proximal left-side forward rotations Naal and the number of detected proximal left-side reverse rotations Nbal, a third determination ratio N1 / N2 based on the number of detected distal right-side forward rotations Nbar and the number of detected distal right-side reverse rotations Nbbr, and a fourth determination ratio N1 / N2 based on the number of detected distal left-side forward rotations Nbal and the number of detected distal left-side reverse rotations Nbbl, and uses each determination ratio N1 / N2 to determine whether the fish in the cage B are migratory fish. Here again, if any of the first to fourth determination ratios N1 / N2 is outside the migration range, the determination control unit 103 can determine that the fish in the cage B are migratory fish. In this way, the judgment control unit 103 determines whether the fish in the fish tank B are migratory fish or not based on the number of forward rotation detections for each divided area in the forward rotation Na1-Na4 and the number of reverse rotation detections for each of the same divided areas (corresponding to the divided areas in the forward rotation Na1-Na4) in the reverse rotation Nb1-Nb4, thereby making it possible to accurately determine whether the fish in the fish tank B are migratory fish or not regardless of where the transducer group 10 is installed in the fish tank B.

[0076] Then, if the judgment control unit 103 determines that the fish in the fish tank B are not migratory fish (Figure 2: S107: NO), the first estimation control unit 104 estimates the number of fish in the fish tank B based on the number of forward rotation detections Na and the number of reverse rotation detections Nb (Figure 2: S108).

[0077] On the other hand, if the judgment control unit 103 determines that the fish in the fish tank B are migratory fish (Figure 2: S107: YES), the calculation control unit 105 calculates the swimming speed Vf of the fish in the fish tank B using a speed calculation means including the number of forward rotation detections Na, the number of reverse rotation detections Nb, and a predetermined swimming speed table (Figure 2: S201).

[0078] Here, when the transducer group 10 and the rotating unit 20 are installed at one end of the fish pen B, the swimming speed table 40 may be the relationship between the judgment ratio N1 / N2 calculated from the overall number of forward rotation detections Na and the number of reverse rotation detections Nb and the swimming speed Vf (m / s) of the fish, or may be the relationship between the judgment ratio N1 / N2 calculated for each divided area and the swimming speed Vf (m / s) of the fish. For example, if the division region for calculating the number of forward rotation detections Na and the number of reverse rotation detections Nb is divided into two regions, a proximal region and a distal region, and swimming speed table 40 is plotted as a graph with the vertical axis representing the swimming speed Vf of the fish and the horizontal axis representing the judgment ratio N1 / N2, as shown in Fig. 15A, the overall judgment ratio N1 / N2 and the swimming speed Vf (m / s) of the fish will have a sharp decreasing relationship, the judgment ratio N1 / N2 in the distal region will have a gradual decreasing relationship and the judgment ratio N1 / N2 in the proximal region will have a gradual increasing relationship. Utilizing this, the swimming speed Vf of the fish for each division region can be calculated from the judgment ratio N1 / N2 for each division region.

[0079] Then, the second estimation control unit 106 estimates the number of fish in the fish pen B based on the calculated swimming speed Vf of the fish and a predetermined fish number table (FIG. 2: S202).

[0080] Here, when the transducer group 10 and the rotating unit 20 are installed at one end of the fish pen B, the fish number table 50 may show the relationship between the fish swimming speed Vf calculated from the overall determination ratio N1 / N2 and the division value Nt / (N1 / N2), or the fish swimming speed Vf calculated from the determination ratio N1 / N2 for each divided area and the division value Nt / (N1 / N2). For example, when the divided areas for calculating the number of forward rotation detections Na and the number of reverse rotation detections Nb are divided into two areas, a proximal area and a distal area, as described above, if the fish number table 50 is plotted as a graph with the division value Nt / (N1 / N2) on the vertical axis and the fish swimming speed Vf on the horizontal axis as shown in FIG. 15B, the fish swimming speed Vf calculated from the overall determination ratio N1 / N2 and the division value Nt / (N1 / N2) will have a gradually decreasing relationship, and the fish swimming speed Vf calculated from the determination ratio N1 / N2 in the distal area will have a gradually decreasing relationship. There is a rapid decrease in the fish swimming speed Vf calculated from the N1 / N2 determination ratio and the division value Nt / (N1 / N2), whereas there is a gradual increase in the fish swimming speed Vf calculated from the N1 / N2 determination ratio in the proximal region and the division value Nt / (N1 / N2). Utilizing this, the division value Nt / (N1 / N2) for each divided region can be calculated from the fish swimming speed Vf calculated from the N1 / N2 determination ratio for each divided region, and the number of fish in each divided region can be estimated. Furthermore, by appropriately selecting the swimming speed table 40 and the fish number table 50 according to the installation position of the transducer group 10 and the target divided region, the total number of fish Nt can be calculated with high accuracy.

[0081] In the tail number estimation system 1 of the present invention, depending on the arrangement of the multiple ultrasonic transmitters / receivers 10a in the transmitter / receiver group 10, the ultrasonic detection areas of the ultrasonic transmitters / receivers 10a may not overlap with each other, resulting in non-detection areas where targets cannot be detected by ultrasonic waves. Therefore, the detection control unit 102 may predict the number of detections in the non-detection areas, for example, using the number of detections in the ultrasonic detection areas on the vertical detection plane A of the transmitter / receiver group 10. Here, there are no particular limitations on the prediction method, and the detection control unit 102 may, for example, predict the number of detections in the non-detection areas by multiplying the ratio of the area of ​​the ultrasonic detection areas to the area of ​​the non-detection areas by the number of detections in the ultrasonic detection areas.

[0082] On the other hand, depending on the arrangement of the ultrasonic transmitter / receivers 10a in the transmitter / receiver group 10, the ultrasonic detection areas of the ultrasonic transmitter / receivers 10a may overlap, causing the ultrasonic transmitter / receivers 10a to detect the same object as a different object. Therefore, the detection control unit 102 may, for example, subtract the number of overlapping detections by the ultrasonic transmitter / receivers 10a from the number of detections in the ultrasonic detection areas on the vertical detection plane A of the transmitter / receiver group 10, and calculate the subtracted value as the true number of detections, or the detection control unit 102 may remove detections of objects that are considered to have been detected overlappingly by the ultrasonic transmitter / receivers 10a.

[0083] Furthermore, in the above description, the number of detections detected by one ultrasonic transmitter / receiver 10a of the transmitter / receiver group 10 located directly below the water surface of the fish tank B was used as an example, but since the number of detections is detected for each ultrasonic transmitter / receiver 10a of the transmitter / receiver group 10, in reality, the number of detections is detected for each divided area in three-dimensional space divided based on, for example, the rotation angle θ, the detection interval Rd, and the type of ultrasonic transmitter / receiver 10a.However, even in this case, the effects of the present invention can be obtained by processing similar to that described above.

[0084] Furthermore, there is no particular limitation on the type of cage B to which the fish number estimation system 1 according to the present invention is applied, but for example, as shown in Figure 16A, it can be applied to a rectangular cage B used in marine aquaculture or a cylindrical cage B. Also, as shown in Figure 16B, it can be applied to a rectangular cage B used in land-based aquaculture. Here, there is no particular limitation on the shape of the cage B, but examples include a cylinder, a rectangular parallelepiped, and a truncated square pyramid.

[0085] 1, the tail count estimation system 1 according to the embodiment of the present invention is configured such that the control unit 30 includes all of the round trip control unit 101, the detection control unit 102, the determination control unit 103, the first estimation control unit 104, the calculation control unit 105, and the second estimation control unit 106. However, this is not limiting, and the configuration may be divided into, for example, a first control unit related to the detection process (e.g., the round trip control unit 101 and the detection control unit 102) and a second control unit related to the determination process (analysis process) (e.g., the determination control unit 103, the first estimation control unit 104, the calculation control unit 105, and the second estimation control unit 106). Specifically, the first control unit is installed at the site, and the second control unit is installed at another location on a server capable of wireless communication with the first control unit. The first control unit acquires data on the number of detections required for the determination process at the site and uploads the data to the server, whereupon the second control unit uses the uploaded data to execute the determination process. This allows on-site staff to concentrate on collecting data, while detailed analysis can be carried out on a server with high processing power, enabling highly accurate estimation of the number of fish. [Example]

[0086] Examples and comparative examples of the present invention will be specifically described below, but the application of the present invention is not limited to these examples.

[0087] First, a simulation was performed as Example 1 for the case where a transducer group was installed in the center of a fish pen, and a swimming speed table showing the relationship between the judgment ratio N1 / N2 and the swimming speed Vf of the fish was created. Specifically, as shown in FIG. 17A , a two-dimensional square fish pen B was created, and a predetermined number Nt of fish were randomly allowed to swim in the fish pen B at a predetermined swimming speed Vf. Next, a vertical detection surface A of the transducer group 10 was virtually installed, extending from the center Ba of the fish pen B to a first position P1 (e.g., a position to the right). The vertical detection surface A was rotated counterclockwise from the first position P1, thereby rotating the vertical detection surface A forward, and the number of fish detected during the forward rotation was detected. Next, the vertical detection surface A was rotated clockwise from the first position P1 (second position P2), thereby rotating the vertical detection surface A backward, and the number of fish detected during the reverse rotation was detected. As a result, the number of forward rotation detections Na and the number of reverse rotation detections Nb became values ​​corresponding to the above-mentioned predetermined number Nt. This shows that it is possible to estimate the number of non-migratory fish based on the number of forward rotation detections Na and the number of reverse rotation detections Nb.

[0088] Next, as shown in FIG. 17B, a predetermined number Nt of fish were allowed to swim in a two-dimensional square fish pen B, rotating at a predetermined swimming speed Vf around the center Ba of the fish pen B. Next, a vertical detection surface A of the transducer group 10 was virtually installed, extending from the center Ba of the fish pen B to a first position P1 (rightward position), and the vertical detection surface A was rotated counterclockwise from the first position P1 to rotate the vertical detection surface A forward, thereby detecting the number of fish detected during the forward rotation. Next, the vertical detection surface A was rotated clockwise from the first position P1 (second position P2), thereby rotating the vertical detection surface A reversely, thereby detecting the number of fish detected during the reverse rotation. As a result, the number of detections during forward rotation Na and the number of detections during reverse rotation Nb were different from each other, and therefore the above-mentioned judgment ratio N1 / N2 was calculated. Then, each time the swimming speed Vf of the fish was changed, the judgment ratio N1 / N2 was calculated, and a graph with the swimming speed Vf of the fish on the vertical axis and the judgment ratio N1 / N2 on the horizontal axis was created as swimming speed table 40. As a result, as shown in Fig. 18A, it was possible to create graph 40 in which the swimming speed Vf of the fish decreases in inverse proportion to the judgment ratio N1 / N2.

[0089] Next, the judgment ratio N1 / N2 was calculated each time the predetermined number Nt and the fish swimming speed Vf were varied, and a graph was created as a fish number table 50, with the vertical axis representing the division value Nt / (N1 / N2) obtained by dividing the total number of fish Nt by the judgment ratio N1 / N2, and the horizontal axis representing the fish swimming speed Vf. As a result, as shown in Figure 18A, it was possible to create graph 50 in which the division value Nt / (N1 / N2) gradually increases with the fish swimming speed Vf. This demonstrated that the total number of fish Nt can be estimated by utilizing the swimming speed table and the fish number table.

[0090] Next, in the fish pen B, a predetermined number Nt of fish were made to swim at a predetermined swimming speed Vf around a position Ba1, which was a predetermined distance above the center Ba of the fish pen B. Then, as described above, a vertical detection surface A of the transducer group 10 was virtually installed, extending from the center Ba of the fish pen B to a first position P1, and the vertical detection surface A was rotated once counterclockwise from the first position P1 to rotate the vertical detection surface A forward, thereby detecting the number of fish detected during the forward rotation. Furthermore, the vertical detection surface A was rotated once clockwise from the first position P1 (second position P2), thereby rotating the vertical detection surface A backward, thereby detecting the number of fish detected during the reverse rotation. As a result, the number of detections Na in forward rotation and the number of detections Nb in reverse rotation were significantly different.

[0091] As described above, the number of forward rotation detections Na and the number of reverse rotation detections Nb can be expressed as the number of detections for each divided area divided by the rotation angle θ from the first position P1 with respect to the center Ba of the fish pen B and the detection interval defined by the distance R in the direction of ultrasonic irradiation from the ultrasonic transmitter / receiver 10a. Therefore, the number of detections for each divided area was converted using the distance traveled and the rotation speed of the vertical detection plane A so that the position of the rotation center of the vertical detection plane A of the transducer group 10 (the center Ba of the fish pen B) was moved to the position Ba1 of the rotation center of the migratory fish. As a result, the number of forward rotation detections Na and the number of reverse rotation detections Nb were expressed in the same manner as described above. Based on these, the determination ratio N1 / N2 was calculated, and swimming speed table 40 and fish number table 50 were created. As shown in FIG. 18A, similar results to those of swimming speed table 40 and fish number table 50 were obtained. As a result, it was found that by converting the position of the center of rotation of the vertical detection plane A (the installation position of the transducer group) in the detection number obtained for each divided area into the position of the center of rotation of the migratory fish, it is possible to estimate the total number of fish Nt, as described above.

[0092] Next, a simulation was performed as Example 2 for the case where a transducer group was installed at one end of a fish pen, and a swimming speed table and a fish number table were created in the same manner as described above. Specifically, as shown in Fig. 19A, a predetermined number Nt of fish were placed in a two-dimensional square fish pen B, and the fish were allowed to swim at a predetermined swimming speed Vf around a predetermined migration center, centered at a position Ba1, which was a predetermined distance upward from the center Ba of the fish pen B. A vertical detection surface A of the transducer group 10 was installed, extending from one end Bb of the fish pen B (e.g., the lower central end of the fish pen B) to a first position P1 (e.g., a position in the upper right direction), and the vertical detection surface A was rotated counterclockwise from the first position P1 to a second position P2 (e.g., a position in the upper left direction) by a predetermined rotation angle θ, thereby rotating the vertical detection surface A in the forward direction, and the number of fish detected during the forward rotation was counted. Next, the vertical detection surface A was rotated clockwise by a predetermined rotation angle θ from the first position P1 to the second position P2, thereby rotating the vertical detection surface A in the reverse direction and detecting the number of fish detected during the reverse rotation. Then, the determination ratio N1 / N2 was calculated based on the number of detections Na in the forward rotation in the entire area and the number of detections Nb in the reverse rotation in the entire area, and a swimming speed table 40 and a fish number table 50 were created. As shown in Fig. 19B, it was possible to create a graph 40 in which the fish swimming speed Vf rapidly decreases with the determination ratio N1 / N2, and a graph 50 in which the division value Nt / (N1 / N2) gradually decreases with the fish swimming speed Vf.

[0093] Furthermore, when calculating the judgment ratio N1 / N2, the number of detections was divided into the overall area, the number of detections in the proximal area (the area from one end of the fish pen to the fish migration center), and the number of detections in the distal area (the area from the fish migration center to the far side), and the judgment ratio N1 / N2 was calculated to investigate the relationship with the fish swimming speed Vf. As a result, as shown in Figure 19B, for the number of detections in the distal area, the fish swimming speed Vf was graphed as a gradual decrease in relation to the judgment ratio N1 / N2, while for the number of detections in the proximal area, the fish swimming speed Vf was graphed as a rapid increase in relation to the judgment ratio N1 / N2. Furthermore, for the number of detections in the distal area, the graph showed a rapid decrease in relation to the fish swimming speed Vf, while for the number of detections in the proximal area, the graph showed a gradual increase in relation to the fish swimming speed Vf. This shows that even if the number of detections per divided area is used, the total number of fish Nt can be estimated by utilizing the swimming speed table 40 and the number of fish table 50.

[0094] In addition, in the second embodiment, as described above, the number of forward rotation detections Na and the number of reverse rotation detections Nb can be expressed as the number of detections for each divided area divided by the rotation angle θ from the first position P1 with respect to one end Bb of the cage B and the detection interval defined by the distance R in the direction of ultrasonic irradiation from the ultrasonic transmitter / receiver 10a. Therefore, as shown in Fig. 20A, the number of forward rotation detections Na and the number of reverse rotation detections Nb were converted using the moving distance and the rotation speed of the vertical detection plane A so that the position of the rotation center of the vertical detection plane A of the transducer group 10 (one end Bb of the cage B) is moved to the position Ba1 of the rotation center of the migratory fish. 20B, for the forward rotation detection number Na and the reverse rotation detection number Nb, the detection number for each detection interval in each divided area is expressed as the detection number as in Example 1, and when swimming speed table 40 and tail number table 50 are created based on these forward rotation detection number Na and reverse rotation detection number Nb, it is possible to create swimming speed table 40 and tail number table 50 similar to Example 1, as shown in Figure 18A. As a result, it was found that by appropriately converting the detection number for each divided area, it is possible to estimate the total number of tails Nt by utilizing the swimming speed table 40 and tail number table 50 described above. [Industrial Applicability]

[0095] As described above, the fish number estimation system and method according to the present invention are extremely useful in the fields of fish farming, marine science, and fishing, and are effective as a fish number estimation system and method that can use an ultrasonic transmitter / receiver to accurately estimate the number of fish in a fish pen, regardless of whether the fish in the pen are non-migratory or migratory. [Explanation of symbols]

[0096] 1. Fish population estimation system 10 Transducer / receiver group 101 Reciprocating control section 102 Detection control unit 103 Judgment control unit 104 First estimation control unit 105 Calculation control unit 106 Second estimation control unit

Claims

1. a group of ultrasonic transducers rotatably installed on a predetermined axis of rotation in the fish pen, the group of ultrasonic transducers being arranged so that the detection areas of the ultrasonic waves irradiated from the ultrasonic transducers form a plane perpendicular to the water surface of the fish pen, thereby forming a vertical detection plane in the water of the fish pen; a reciprocation control unit that executes a forward rotation from a first position of the fish cage to a second position of the fish cage and a reverse rotation from the second position to the first position with respect to the vertical detection surface of the group of transducers; a detection control unit that detects the number of fish in the fish tank as a detection number based on the vertical detection plane of the group of transducers for each of the forward rotation and the reverse rotation; a determination control unit that determines whether the fish in the fish tank are migratory fish based on the number of forward rotation detections during the forward rotation and the number of reverse rotation detections during the reverse rotation; a first estimation control unit that estimates the number of fish in the fish tank based on the number of forward rotation detections and the number of reverse rotation detections when the result of the determination indicates that the fish in the fish tank are not migratory fish; a calculation control unit that calculates the swimming speed of the fish in the fish pen using a speed calculation means including the number of forward rotation detections, the number of reverse rotation detections, and a predetermined swimming speed table when the result of the determination is that the fish in the fish pen are migratory fish; a second estimation control unit that estimates the number of fish in the fish pen based on the calculated swimming speed of the fish and a predetermined fish number table; A fish population estimation system equipped with the system.

2. the determination control unit calculates a determination ratio by dividing a first detection number, which is a larger number of detections out of the forward rotation detection number and the reverse rotation detection number, by a second detection number, which is a smaller number of detections, and determines whether the calculated determination ratio is within a predetermined migration range including 1.0, thereby determining whether the fish in the fish tank are migratory fish. The system for estimating the number of fish according to claim 1.

3. the detection control unit detects, for each of the forward rotation and the reverse rotation, the number of detections for each divided area divided by a rotation angle from the first position and a detection interval defined by a distance from the ultrasonic transmitter / receiver in an ultrasonic wave irradiation direction; the determination control unit determines whether the fish in the fish pen are migratory fish based on the number of forward rotation detections for each divided area during the forward rotation and the number of reverse rotation detections for the same divided area during the reverse rotation. The system for estimating the number of fish according to claim 1.

4. A method for estimating the number of fish in a fish population estimation system, comprising: a group of ultrasonic transmitters and receivers rotatably installed in the fish pen around a predetermined rotation axis; and a detection area of ​​ultrasonic waves irradiated from the plurality of ultrasonic transmitters and receivers is arranged to form a vertical detection plane in the water of the fish pen by arranging the plurality of ultrasonic transmitters and receivers so that the detection area of ​​ultrasonic waves irradiated from the plurality of ultrasonic transmitters and receivers forms a vertical plane with respect to the water surface of the fish pen; a reciprocating control step of rotating the vertical detection surface of the transducer group back and forth between a forward rotation from a first position of the fish cage to a second position of the fish cage and a reverse rotation from the second position to the first position; a detection control step of detecting the number of fish in the fish pen as a detection number based on the vertical detection plane of the group of transducers for each of the forward rotation and the reverse rotation; a determination control step of determining whether or not the fish in the fish tank are migratory fish based on the number of forward rotation detections during the forward rotation and the number of reverse rotation detections during the reverse rotation; a first estimation control step of estimating the number of fish in the fish pen based on the number of forward rotation detections and the number of reverse rotation detections when the result of the determination indicates that the fish in the fish pen are not migratory fish; a calculation control step of calculating the swimming speed of the fish in the fish pen using a speed calculation means including the number of forward rotation detections, the number of reverse rotation detections, and a predetermined swimming speed table when the result of the determination is that the fish in the fish pen are migratory fish; a second estimation control step of estimating the number of fish in the fish pen based on the calculated swimming speed of the fish and a predetermined fish number table; A method for estimating the number of fish.

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