NO20211066A1

NO20211066A1 - A guiding device, system and method for sorting fish

Info

Publication number: NO20211066A1
Application number: NO20211066A
Authority: NO
Inventors: Ben-Tommy Eriksen
Original assignee: Nornet As
Priority date: 2021-09-06
Filing date: 2021-09-06
Publication date: 2023-03-07

Description

Field of the invention

[0001] The invention relates to a sorting system for wet-sorting and un-stressed guiding of living fish in water.

Background of the invention

[0002] In aquaculture there is a need to separate and sort fish based on their size or condition during the entire lifespan for farmed fish, either for sorting out mature fish for processing, fish ready for different pens or sorting for treatment and the like.

[0003] Hitherto one has mainly known systems of sorting of living fish, wherein one often has manual or automatically forced, or guided, the fish down or to, often in big continuous quantities, to an apparatus of sorting, where the fish often become stressed or damaged by being in contact with moving parts or being forcefully moved along guides. Damage to fish, such as wounds or loss of mucous layer has been proved to be extremely important to the fish' resistance to sea lice and pathogens.

[0004] Document NO20200294 A1 discloses a system for sorting fish, wherein the system comprises a channel for transporting fish with a crosswise gully 6, wherein smaller fish falls down the gully and into an receiving section 8 while larger fish passes over the gully 6 an into an second receiving section. The solution disclosed in NO20200294 A1 requires all fish to be transferred from their storage tanks and forcefully conveyed along a channel that touches the fish, which is not desirable as it may lead to damage. The sorting arrangement is fixed to a size criterion decided on by the size of the gully, and the drop down into the gully and receiving section may be harmful and stressful for the fish.

[0005] Document WO9406281A1 discloses a system for sorting fish based on size and weight wherein a gate system opens and closes to guide the fish into different areas.

[0006] A device for recording of number and size of fish is known from Norwegian patent NO 168151 B wherein an optical registration unit is known.

[0007] As the type of handling the fish is exposed to has a great impact on the quality of the fish and economical gain of the farmer, some systems and devices have therefor been developed to try and guide and sort the fish in a non-physical manner.

[0008] Document WO 9311664 A1 discloses a device for sorting and guiding swimming fish using electric or magnetic fields activated after registering the size of the fish thereby guiding a specified size or kind of fish in between a pair of beams of magnetic field and consequently in a predetermined direction. The solution disclosed in WO 9311664 A1 has the downside that electronic conductors are subjected to water and might malfunction and subject the fish to harm.

[0009] Document NO 314481 B1 discloses a device and method for sorting fish by illuminate and consequently darken two separate channels 1A, 1B, wherein the fish is intended to swim towards the darkened channel. A manual or automated indicator 3 indicated the size of a passing fish and consequently lights one of the lights 2A, 2B for a prolonged period of time. The solution disclosed in NO 314481 B1 has the disadvantage that it may not be accurate as fish does not always swim towards a darker area.

[0010] A disadvantage with the known methods for sorting live swimming fish is that it requires the fish to be transported, cached or physically guided into a channel which stresses the fish. A further disadvantage of known systems is that it requires movable parts that may hit or pinch the fish, which may cause damage to the fish.

[0011] The purpose of the invention is to provide a system and method which in an efficient and careful way can sort out individual fish.

[0012] It is an aim of the present invention to obtain a wet sorting of the single fish without that it must be touched, physically guided or exposed to movable gates or parts and therefore stressed and/or damaged.

[0013] It is further an aim of the present invention to provide a systema and method that enables the fish sort itself over time. It is further an aim of the present invention to overcome the shortcomings of the disclosed prior art and to provide an alternative to the prior art.

Summary of the invention

[0014] The invention is set forth and characterized in the main claims, while the dependent claims describe other characteristics of the invention.

Brief description of the figures

[0015] These and other characteristics of the invention will become clear from the following description of a preferential form of embodiment, given as a non-restrictive example, with reference to the attached schematic drawings.

Fig. 1 shows a fish pen from above with two sorting systems and one common divider.

Fig. 2.1 and 2.2 shows one and two fish from above producing pressure waves by swimming.

Fig. 3.1, 3.2 and 3.3 shows two neighboring fish from above and their swimming paths.

Fig. 4.1 and 4.2 shows a guiding and sorting system seen from above.

Fig. 5.1 and 5.2 shows a guiding and sorting device seen from above.

Fig. 6 shows an array of pressure sensors.

Fig. 7.1 and 7.2 shows a guiding and sorting system seen from above.

Fig. 8.1 and 8.2 shows a guiding and sorting system seen from above.

Detailed description of the invention

[0016] The following description will use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, ”upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader’s convenience only and shall not be limiting. Like numerals on different drawings describe the same feature. Numerals with apostrophe represents an additional feature represented by the same numeral, for instance the number 210 will represent one or the first of multiple or all of the multiples, and the numeral 210’ represents an additional of the same feature, like a second or multiple of the same feature.

[0017] Figure 1 illustrates an overview of a fish pen 10 or storage tank of fish 50, 60 of different sizes. A divider 90 separates the fish pen into two areas, a left and a right area, wherein the invention may be utilized to sort and guide the smaller fish 50 into the left side area, or a first side, of the pen 10 and the larger fish 60 into right side area, or second side, through two sorting devices 30, 30’ in a system in accordance with an embodiment of the invention. As a smaller fish 50 is to be sorted into the left side, the upper sorting device 30 is adapted to guide larger fish 60 from the left side, through the upper sorting system 30 and into the right-side area. Smaller fish 50 will thusly be guided via path pat 20, while larger fish are guided via path 40. The lower sorting device 30’ is adapted to guide smaller fish 50 from the right-side area of the fish pen 10 and into the left side area though the path 80 while the larger fish 60 is guided back to the right-side area vi path 70 if the fish 60 swims through the lower sorting device 30’. After a certain time, all small fish 50 will have sorted itself, by swimming, to the left side area, and all larger fish 60 will have sorted itself to the right-side area. In this embodiment of use, each sorting system will function as oneway valve for the different sized swimming fish, wherein the fish freely sorts itself to the different sides to the divide without being pushed or forcefully moved.

[0018] The term smaller and larger fish 50, 60 is used herein to illustrated an divide in a group of fish of different sizes wherein smaller fish 50 may be any fish under a predetermined size, and larger fish 60 may be all fish above or equal to said predetermined size. This size may be different for different usage of the invention as there are multiple reasons for sorting fish according to their size.

[0019] Figure 2.1 illustrates a fish 110 emitting a signal 100 while swimming. The signal 100 are pressure waves created by the swimming motion of the fish, and the frequency of the pressure waves are equal to the frequency of the oscillating motion of the fish. All fish with a propulsion comprised of wavelike movements of the fish's body and tail will produce a pressure wave that may be regarded as a signal or should be understood as a signal herein. This signal 100 is detected by neighboring fish 130 if two fishes 110, 130 are close to each other. Most species of fish have what is called a lateral line system, also called lateralis system, a system of tactile sense organs, that serves to detect movements and pressure changes in the surrounding water. It is comprised of a series of organs along the lateral line arranged in an interconnected network along the head and body of the fish. This organ is used to detect the direction of water movement and pressure change along the body of the fish. When fish swim in shoals they use this system to detect adjacent fish and prevent two neighboring fish to collide. Figure 2.2 illustrates a first swimming fish 110 producing, by swimming, a pressure signal 100 and a neighboring fish 130 producing, by swimming, a second pressure signal 140. The first fish 110 will detect the pressure waves 140 as they get within a certain distance of each other, and the pressure waves 140 will impact the first fish 120 along its side 120, and vice versa. This information us used to adjust the distance between the two fish 110, 130. If they detect that they are too close, one or both will take evasive action and turn away from the path they are on.

[0020] As smaller fish normally has a higher frequency of the oscillating motion of the body and tail compared to a larger fish, while swimming at the same velocity, two fish can detach the size of each other by the frequency of the pressure signal detected. In figure 3.1 a first fish 110 and a neighboring fish 130 detects each other’s presence and reciprocal distance and continues on their path without moving further away or closer, as their reciprocal distance is adequate. In figure 3.2, the neighboring fish 130 detects the pressure wave 140 from the first fish 110 and decides that they are too close and increases their reciprocal distance by changing path to a new path (stippled line). The reason while only one of the fish changes swimming path may be that the first fish 110 is larger than the neighboring fish 130, which they can detect, and the smaller fish takes evasive action. In figure 3.3, both fish 110, 130 takes evasive action from their initial path (solid line) to a new path (stippled line), to increase their reciprocal distance. The invention disclosed herein utilizes this effect to manipulate the swimming direction, or path, of a fish, by emitting a signal that can be felt by the lateral line system of the fish, to manipulate the fish into feeling an adjacent object too close. For the invention, a signal source or device 150, 151 is used to replicate a pressure wave or flow that will interact with the fish and be detected as a flowing current or a fluctuating pressure. The fish that receives such a signal from one side will feel it as a close neighboring fish or objected and take evasive action. When the fish is faced with a limited options for a new path, such a signal source or device 150, 151 may be used to direct the fish in a desired directing, such as to a first or to a second side of a divider 90. As the frequency of the signal can be interpreted by the receiving fish as a smaller or larger fish that itself, in one embodiment of the invention, the frequency of the emitted signal 100, 101 is the same or lower than the oscillating swimming frequency of the fish, thereby increasing the likelihood that the fish changes path. This may be achieved with a biomass measurement device 170 that is capable of measuring the oscillating swimming frequency either based on the speed of travel and the size of the fish, or by directly measuring the frequency by audio or video capture.

[0021] Figure 4.1 illustrates an embodiment of the invention wherein a sorting system for sorting fish 50, 60, 110 in a body of water of swimming fish. The system comprises a divider 90, dividing at least part of a body of water into a first side and a second side of the divider 90. A first signal source 150 and second signal source 151 are situated on respective first and second side of the divider 90, a predetermined distance from the divider 90, wherein the first signal source 150 is arranged to emit a signal 100 that guides a fish 110 in a direction away from the first signal source 150 to the opposite side of the divider 90 in relation to the first signal source 150, as seen on figure 4.1. The second signal source 151 is arranged to emit a second signal 101 that guides a fish in a direction away from the second signal source 151 to the opposite side of the divider 90 in relation to the second signal source 151, as seen in figure 4.2. The system may be used to sort the fish by its size or weight to either the first or a second side of the divider 90. To measure and register the size or weight of the fish 110, the system may comprise a biomass measurement device 170, arranged to measure the size of the fish 50, 60, 110 passing the biomass measurement device 170. In figure 4.1 and 4.2 the biomass measurement device 170 is arranged a predetermined distance, down the swimming direction of the fish 110, against the sorting direction, from the first and second signal sources 150, 151. The first and second signal sources 150, 151 may be connected to a processing device and the processing device is further connected to the biomass measurement device 170, thereby allowing for the first and second signal sources 150, 151 to receive command signals from the processing device which provide information on which of the first or second signal source 150, 151 to emit a signal, and the physical properties of the signal, thereby guiding the fish 50, 60, 110 to either the first or second side of the divider 90. In an embodiment of the invention, for a fish to be sorted and guided in a non-intrusive and non-touching manner, the fish 110 swims along the sorting direction, i.e. the swimming direction is the sorting direction, and into the system 30, whereby the fish passes the biomass measurement device 170. The biomass measurement device 170 records one or multiple images and/or audio recording of the passing fish 110, as the fish passes a recording area. This information is sent to the processing device that might comprise a memory and computational means, to determine if the fish 110 is smaller or larger than a predetermined size. Said size may be the length, heigh or mass of the fish. Based on the comparison between the recorded size and the predetermined sorting size, the processing device may activate either the first 150 or the second 151 signal device to emit a signal to manipulate the swimming fish 110 into swimming either to the first or second side of the divider 90, thereby sorting the fish without forcefully touching or moving the fish as it swims in the desired direction under its own propulsion. In an embodiment of the invention the biomass measurement device 170 comprises an imaging device adapted to image a recording area and identify at least the size of a fish within the recording area. In another embodiment of the inventio the biomass measurement device 170 comprises an acoustic device comprising an array of microphones or hydrophones 210, 210’, arranged along a distance opposite the sorting direction, adapted to record audio from an recording area and identify at least the size of a fish within the recording area. In figure 6 an array of hydrophones is illustrated with six hydrophones 210, 210’ arrange in two rows of three hydrophones 210, 210’, wherein the hydrophones 210, 210’ is adapted to detect the difference in time a wave signal 100 from a swimming fish reaches the hydrophones 210, 210’. By triangulating time difference from the wave signal 100 the distance to the fish, the size of the fish and velocity of the fish can be determined by a processing device with memory and processing capabilities. The hydrophones 210, 210’ may also be pressure detectors.

[0022] The invention as disclosed herein may also be used to sort fish 110 based on their condition, such as health condition, wherein such conditions may be number of sea lice on the fish 110, number or size of wounds or thickness to length ration, so that the weaker of infected fish may be sorted out for treatment. To achieve this the biomass measurement device 170 may further be adapted to record images of the fish from whereby wounds or sea lice is counted, either manually or by a processor device, or the height/length or width/length ratio is determined from the recordings, and wherein a predetermined value for the conditions is set to determine if the fish 110 is to be sorted to a first side or a second side of a divider 90.

[0023] There are multiple layouts for guiding fish into and out of the sorting system 30. In one embodiment of the invention, the system may be utilized to sort swimming fish in a fish pen 10 as illustrated in figure 1. In said embodiment, a layout as illustrated in figures 4.1 and 4.2 may be utilized, wherein the divider 90 is a water permeable or non-permeable net, sheet or wall between two sides of the tank 10, and between a bottom of the tank 10 and at least the water surface or an upper boundary, thereby dividing said tank 10 into a first and second side. The tank 10 holds a body of water of swimming fish, and wherein the divider 90 comprises an opening arranged for fish to enter from the first side of the divider 90 to a second side of the divider. In figure 4.2 the divider 90 as seen from above is parted by the opening, the divider 90 comprises a first part 90a and a second part 90b divided by the opening. The opening may have a heigh that is equal to or less than the height of the divider. The second part 90b comprises an inclined section 220 at an angle to a substantially in-line arranged first part and second part of the divider 90a, 90b, wherein the opening are arranged between an end of the inclined section 220 and an end part of the first part of the divider 90a, and wherein the second signal source 151 is situated on the end of the inclined section 220. In this embodiment the first and second signal source 150, 151 is situated in line with the end of the first part 90a and equal distance apart from the end of the first part 90a. Furthermore, an guide structure 130 is arranged at least between the first signal source 150 and the biomass measurement device 170 to arrange for a channel structure defined by the guide structure 230, the inclined section 220 and/or the second part of the divider 90b. In this embodiment the fish will swim into the guided area between the second part of the divider 90b and the guide structure 230 on the first side of the divider 90, passed the biomass measurement device 170. The guide structure may be comprised on the same material as the divider 90. If the fish 110 is to be sorted back to the first side of the divider 90, the second signal source will emit a signal 101, manipulating the fish 110 into swimming away from the second signal source 151, and out through an opening defined by the end of the first part 90a and the guide structure 230, i.e. the same side the fish 110 came from. If the fish 110 is to be sorted to the second side of the divider 90, the first signal source 150 will emit a signal 100, manipulating the fish 110 into swimming away from the first signal source 150, and out through the opening defined by the end of the first part 90a and end of the inclined section 220, i.e. to the other side from which the fish 110 came from.

[0024] I another embodiment of the invention, the system may be used in a lay out wherein the fish 110 swims though a canal, duct or tube and wherein it is to be sorted into one of two further canals, ducts or tubes. Figure 7.1 and 7.2 illustrates said layout wherein a sorting section having an inlet port 240 arranged in an end and a first and second outlet ports 250, 251 arranged in an opposite end of the sorting section along a sorting direction, wherein the divider 90 at least partly separates the first and second outlet ports 250, 251. In this embodiment the fish 110 may be stored in a first tank comprising a body of water of swimming fish in fluid communication to the inlet port 240, and wherein a second and third fluid tank is in fluid communication with the first and second outlet ports 250, 251, respectively, wherein the fish in the first tank is to be sorted by the invention into one of the second or third fluid thanks. The biomass measurement device 170 is arranged a predetermined distance along opposite the sorting direction from the first and second signal sources 150, 151. In this embodiment of the invention the divider 90 may the walls of two adjacent tubes or ducts or the wall between two adjacent tubes or ducts as illustrated in figure 7.2 or a divider between to separated sections of a body of water as illustrated in figure 7.1.

[0025] Figure 8.1 illustrates the sorting device wherein a fish 110 is in the sorting section has passed the measurement device 170 and wherein the second signal source 151 emits a signal to manipulate the fish 110 to swim to the first outlet port 250 (illustrated with the arrow). Figure 8.2 illustrates the sorting device wherein a fish 110 is in the sorting section has passed the measurement device 170 and wherein the first signal source 150 emits a signal to manipulate the fish 110 to swim to the second outlet port 251 (illustrated with the arrow).

[0026] In an embodiment of the invention, the first and second signal source 150, 151 comprises pressure generating means and/or a flow generating means to produce and transmit the pressure signal or flow signal that is to manipulate the fish 110. The first and second signal source may be a hydrodynamic signal source in an embodiment of the invention, wherein a hydrodynamic signal source is at least a device capable of inducing hydrodynamic waves, both longitudinal waves and traverse waves, and currents, such as flown in the fluid. The term signal is used herein to disclose a time dependent change in the pressure felt by an object, such as the fish, and to emphasize that it it’s not the brute force of the wave or current flow that forces the object off path, but a signal that manipulates the object to move to a determined destination based on the direction of the signal. Furthermore, the term signal is used to allow for the wave or current flow to be emitted with a frequency, wavelength, velocity, period, amplitude, and/or a variation in pressure. The first and second signals 100, 101 may thus be a hydrodynamic pressure wave signals and/or hydrodynamic flow signals generated by the signal sources 150, 151. A pressure wave should be understood an oscillation in the water wherein the water partials oscillates back and forth or remains somewhat stationary while a wave of pressure is moving in the fluid, while a flow signal is characterized by the movement of the water particles along a flow path. The terms flow and current are sometimes differentiated in that flow is the movement of a fluid while current is the part of a fluid that moves continuously in a certain direction, however both terms are used herein as interchangeable terms and should be understood as meaning the same. When said flow impacts an object, such as a fish, pressure is introduced on the surface of said object. To generate said signals the pressure generating means may be an underwater speaker or a moving membrane to generate pressure signal in the fluid. The flow generating means may be a water jet device adapted for introducing a fluid flow into the water, or a moving flap to generate a flow signal in the fluid. Both the flow and the pressure waves may be emitted or introduced from the signal sources 150, 151 with a predetermined frequency adapted to be equal to the swimming frequency of the fish 110 than is to be sorted. In situations where it might not be necessary to mimic the swimming frequency of the swimming 110, the invention may be used with a single impulse signal, a longer frequency reliant signal or a steady continuous signal. In one embodiment of the invention the first and second signal source 150, 151 may comprise light emitting means to emit light as a signal.

[0027] In an embodiment, the invention relates to a guiding device for sorting fish 50, 60, 110 in a body of water of swimming fish, where the sorting and guiding device comprising a signal source 150, 151, 190, wherein the signal source 150, 151, 190 is arranged to emit a signal 100, 101, 180 that guides a fish in a predetermined direction. The signal source 150, 151, 190 may be a hydrodynamic signal source adapted to emit a hydrodynamic signal, such as a wave or flow in the form of an impulse or time dependent change in pressure or flow. The at least one signal source 150, 151, 190 comprises pressure generating means and/or a flow generating means, and wherein the signal 100, 101, 200 generated by the generating means are a hydrodynamic pressure wave signal and/or hydrodynamic flow signals generated by the signal source 150, 151, 190. The pressure generating means may be an underwater speaker and/or a moving membrane adapted to generate pressure and/or pressure fluctuations as a signal in the fluid. The flow generating device may be a water jet device, propeller, impeller, a moving membrane and/or a moving flap adapted to generate a flow and/or flow fluctuations as a signal in the fluid. A biomass measurement device 170 may be located downs stream, or opposite the sorting direction, from the guiding device, adapted to determine characteristics of the fish swimming within a recording area and conveying instruction information to the guiding device 190.

[0028] Figure 5.1 and 5.2 illustrates the use of a device as disclosed wherein the guiding device comprises a rotatable flap 190 hinged in one end. The rotatable flap 190 is adapted to be in a first position wherein the flap 190 is in line with the divider 90, and to emit a first flow signal 200 by moving (rotating around its hinge) in a first direction 180, thereby manipulating the fish 110 to swim away along path 160 to the side of the flow signal 200 and to the second side of the divider 90, as illustrated in figure 5.1. In figure 5.2 the rotatable flap 190 is moved (rotating around its hinge) in a second direction, opposite the first direction, to emit a second flow signal 200 thereby manipulating the fish 110 to swim in a direction along path 160 to the side of the flow signal 200 and to the first side of the divider 90. In this embodiment the signal is emitted towards fish 110 in skewed direction from the front ow the fish 110. The signal 200 will travel from the tip of the flap 190 and downstream across to the side the flap moves to, thereby impacting the fish 110 mainly on one side of the fish 110, thereby manipulating the fish to the opposite side. The flap 190 is not touching or in contract with the fish 110 nor does it block the entire undesired path of the fish, as the length of the flap 190 is shorter than the distance to any surrounding elements or adjacent guiding structure. Thus, the flap does not pose any danger for the fish nor does the fish risk being entrapped between the flap 190 and the surroundings. The flap may be rotatable by an actuator. In a non-illustrated embodiment, a multi directional signal source 150, 151, 190 adapted to emit a hydrodynamic signal that a fish 110, is arranged on the end of a divider adapted to emit a hydrodynamic signal to multiple different directions at different times, such as to a first side and a second side from one single origin, such as two water jets adjoined, or two underwater speaker means adjoined, facing opposite or different directions.

[0029] It is also provided a method for guiding fish using a device as disclosed herein and a method for guiding and sorting fish using a system as disclosed herein.

[0030] Having described preferred embodiments of the invention it will be apparent to those skilled in the art that other embodiments incorporating the invention may be used. These and other examples of the invention illustrated above are intended by way of example only and the actual scope of the invention is to be determined from the following claims.

Reference numerals

10 Fish pen, fish tank

20 Path of smaller fish not getting though

30, 30’ Sorting system

40 Path of larger fish getting though

50 small fish

60 large fish

70 Path of large fish not getting though

80 Path of small fish getting though

90 Divider

90a, 90b First and second part of the divider

100 Signals from the first signal device; Sound waves, pressure waves,

vibrations that make fish change sides

101 Signals from the second signal device; Sound waves, pressure waves, vibrations that make fish stay on the same side

110 Fish

120 Pressure wave hits neighboring fish

130 Neighboring or adjacent fish

140 Sound waves from neighboring fish

150 First signal device, speaker, pressure wave generator, flow generator 151 Second signal device, speaker, pressure wave generator, flow generator 160 Swimming direction on fish if changing side. Fish that are on the wrong side.

161 Swimming direction on fish remaining on side. Fish that are on the right side.

170 Biomass measurement device

180 Moving direction of flap

190 Flap

200 Flow signal from flap

210, 210’ Hydrophone or pressure sensor

220 Inclined section of divider

230 Guide structure

240 Inlet port

250 First outlet port

251 Second outlet port

Claims

1. A guiding device for sorting fish (50, 60, 110) in a body of water of swimming fish, comprising at least one signal source (150, 151, 190), wherein the at least one signal source (150, 151, 190) is arranged to emit a signal (100, 101, 180) that guides a fish in a predetermined direction.

2. The device according to claim 1, wherein the at least one signal source (150, 151, 190) is a hydrodynamic signal source adapted to emit a hydrodynamic signal.

3. The device according to claim 1 or 2, wherein the at least one signal source (150, 151, 190) comprises pressure generating means and/or a flow generating means, and wherein the signal (100, 101, 200) generated by the generating means are a hydrodynamic pressure wave signal and/or hydrodynamic flow signals generated by the signal sources (150, 151, 190).

4. The device according to claim 3, wherein the pressure generating means is at an underwater speaker and/or a moving membrane adapted to generate pressure signal in the fluid.

5. The device according to claim 3 or 4, wherein the flow generating device is at least one of a water jet device, propeller, impeller, a moving membrane or a moving flap adapted to generate a flow signal in the fluid.

6. A guiding system (30) for sorting fish (50, 60, 110) in a body of water of swimming fish, comprising:

- a divider (90), dividing at least part of the body of water into a first side and a second side of the divider (90),

- a first signal source (150) and second signal source (151) on respective first and second side of the divider (90),

wherein the first signal source (150) is arranged to emit a signal (100) that guides a fish in a direction away from the first signal source (150) to the opposite side of the divider (90) in relation to the first signal source (150), wherein the second signal source (151) is arranged to emit a second signal (101) that guides a fish in a direction away from the second signal source (151) to the opposite side of the divider (90) in relation to the second signal source (151).

7. The system according to claim 6, wherein the system further comprises a measurement device (170), arranged to measure the size or the or condition of the fish (50, 60, 110) passing the biomass measurement device (170), wherein the first and second signal sources (150, 151) are connected to a processing device and the processing device is further connected to the biomass measurement device (170), the first and second signal sources (150, 151) being adapted to receive signals from the processing device which provide information on which of the first or second signal source (150, 151) to emit a signal, thereby guiding the fish (50, 60, 110) to either the first or second side of the divider (90).

8. The system according to claim 7, wherein the biomass measurement device (170) is arranged a predetermined distance along a directing opposite sorting direction from the first and second signal sources (150, 151).

9. The system according to any one of the claims 6-8, wherein the first and second signal source (150, 151) comprises pressure generating means and/or a flow generating means, and wherein the first and second signals (100, 101) are a hydrodynamic pressure wave signals and/or hydrodynamic flow signals generated by the signal sources (150, 151).

10. The system according to claim 9, wherein the pressure generating means is an underwater speaker and/or a moving membrane adapted to generate pressure signal in the fluid.

11. The system according to claims 9 or 10, wherein the flow generating device is at least one of the of a water jet device, propeller, impeller a moving membrane or a moving flap adapted to generate a flow signal in the fluid.

12. The system according to any one of the claims 6-11, wherein the first and second signal source (150, 151) each comprises a light emitting device adapted to emit light signals that guides a fish in a direction away from the signal source.

13. The system according to any one of the claims 6-12, wherein the signal emitted has a predetermined frequency.

14. The system according to any one of the claims 6-13, wherein the divider (90) is a water permeable net or non-permeable wall or sheet between two sides of a tank (10) holding the body of water of swimming fish, and between a bottom of the tank (10) and at least the water surface or an upper boundary, thereby dividing said tank (10) into a first and second side, and wherein the divider (90) comprises an opening arranged for fish to enter from the first side of the divider (90) to a second side of the divider.

15. The system according to claim 14 wherein the divider (90) comprises a first part (90a) and a second part (90b), wherein the second part (90b) comprises an inclined section (220) at an angle to a substantially in-line arranged first part and second part of the divider (90a, 90b), wherein the opening is arranged between an end of the inclined section (220) and an end of the first part of the divider (90a), and wherein the second signal source (151) is situated on the end of the inclined section (220).

16. The system according to any one of the claim 7-13, wherein a guide structure (230) is arranged at least between the first signal source (150) and the measurement device (170) to arrange for a channel structure defined by the guide structure and the inclined section (220) and/or the second part of the divider (90b).

17. The system according to any one of the claims 6-16, wherein the system comprises a sorting section having an inlet port (240) arranged in an end and a first and second outlet ports (250, 251) arranged in an opposite end of the sorting section along a sorting direction, wherein the divider (90) separates the first and second outlet ports (250, 251).

18. The system according to any one of the claims 6-17, wherein the measurement device (170) comprises an imaging device adapted to image a recording area and identify at least the size of a fish within the recording area.

19. The system according to any one of the claims 6-19, wherein the measurement device (170) comprises an acoustic device comprising an array of microphones or hydrophones, arranged along a distance along an opposite direction than the sorting direction, adapted to record audio from an recording area and identify at least the size of a fish within the recording area.

20. A method for sorting fish in a body of water of swimming fish, wherein the fish is guided by a guiding device according to any one of the claims 1-5.

21. A method for sorting fish in a body of water of swimming fish, wherein the fish is guided and sorted by a guiding system according to any one of the claims 6-19.