WO2022164325A1 - System for preventing fouling on cages for aquatic animals in water - Google Patents

System for preventing fouling on cages for aquatic animals in water Download PDF

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Publication number
WO2022164325A1
WO2022164325A1 PCT/NO2022/050024 NO2022050024W WO2022164325A1 WO 2022164325 A1 WO2022164325 A1 WO 2022164325A1 NO 2022050024 W NO2022050024 W NO 2022050024W WO 2022164325 A1 WO2022164325 A1 WO 2022164325A1
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WO
WIPO (PCT)
Prior art keywords
net
transducers
sound
ultrasound
water
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PCT/NO2022/050024
Other languages
French (fr)
Inventor
Petter Birkeli Wiik PETTERSEN
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Cage Ctrl As
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Publication of WO2022164325A1 publication Critical patent/WO2022164325A1/en

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    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01K—ANIMAL HUSBANDRY; AVICULTURE; APICULTURE; PISCICULTURE; FISHING; REARING OR BREEDING ANIMALS, NOT OTHERWISE PROVIDED FOR; NEW BREEDS OF ANIMALS
    • A01K61/00—Culture of aquatic animals
    • A01K61/60—Floating cultivation devices, e.g. rafts or floating fish-farms
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01K—ANIMAL HUSBANDRY; AVICULTURE; APICULTURE; PISCICULTURE; FISHING; REARING OR BREEDING ANIMALS, NOT OTHERWISE PROVIDED FOR; NEW BREEDS OF ANIMALS
    • A01K61/00—Culture of aquatic animals
    • A01K61/10—Culture of aquatic animals of fish
    • A01K61/13—Prevention or treatment of fish diseases
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01K—ANIMAL HUSBANDRY; AVICULTURE; APICULTURE; PISCICULTURE; FISHING; REARING OR BREEDING ANIMALS, NOT OTHERWISE PROVIDED FOR; NEW BREEDS OF ANIMALS
    • A01K63/00—Receptacles for live fish, e.g. aquaria; Terraria
    • A01K63/10—Cleaning bottoms or walls of ponds or receptacles
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
    • Y02A40/80—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in fisheries management
    • Y02A40/81—Aquaculture, e.g. of fish

Definitions

  • the present invention relates a system for preventing fouling on cages for farming aquatic animals in water, and a net to be used in such a system and use of such a system according to the preamble of the independent patent claims.
  • Aquaculture is a major industry, and most of the farmed animals are farmed in fish cages at the sea.
  • a traditional fish cage comprises a floating collar at the surface of the sea, a net surrounding the farmed organisms and fastened to the collar, the net is often referred to as net cage, and weights to keep the cage dilated and stretched and in such a way that the meshes of the net is open.
  • the mesh size of the net should be adjusted in such a way that the farmed organisms are kept inside the cage, yet allowing water to flow through the mesh, in and out of the cage.
  • the floating collars are traditionally round or square and comprises two or three circular tubes of plastic arranged outside of each other and fastened to each other by steel or plastic brackets.
  • the net cage traditionally comprises a net wall and net bottom, the bottom may be flat or shaped as a cone.
  • the weight may be any suitable weight, such as a sinker tube.
  • Another well known type of fish cage in the water is a rigid frame covered by a net of metal or textile, and attached to buoyancy means, either floating collars as mentioned above, floating barges, or similar means.
  • buoyancy means either floating collars as mentioned above, floating barges, or similar means. The net will thus be expanded by the frame, and weights will not be necessary.
  • the floating collar or other buoyancy means must be designed to have sufficient buoyancy to carry the weight of the whole fish cage, including possible rigid frames, weights and other equipment.
  • the buoyancy must be sufficient to keep the net cage at the surface of the water even during strong water current, rough weather and high waves.
  • the design of a traditional floating collar can only give a limited buoyancy without being comprehensively re-designed.
  • the weight of the net cage and equipment should therefore be reduced as much as possible.
  • the fouling will prevent water from flowing through the net, and thus the water inside the fish cage will not be as fresh as desired, which may lead to less growth and reduced fish health.
  • the oxygen level in the fish cage may become reduced when the net is very fouled.
  • fouling and debris will create a hiding place for parasites such as sea lice, irritant hydroids, parasite eggs and larvae, and organisms causing diseases such as amoebic gill disease.
  • cleaning fish such as wrasses or lumpfish, prefer to feed off the fouling rather than the sea lice on the fish.
  • the net may be made of a material preventing fouling, yet withstanding the harsh and corrosive environments at the sea, offering sufficient strength and ensuring the fish welfare. Such materials are however not efficient in preventing fouling over time.
  • Different types of coating have also been used, however, the coating will lose its effect after a short period of time in the sea, and/or it will be washed or torn off.
  • the coatings may comprise poisonous compounds, and further they may dissolve or loosen from the net and leak into the surrounding sea. This may reduce the welfare of the fish in the fish cage, and the environment around the fish cage.
  • the invention relates to a system for preventing fouling on cages for aquatic animals in water.
  • the system comprises a net surrounding the aquatic animals, and having a mesh size allowing water to flow through, wherein the net comprises threads of sound-conductive material interwoven in a net of non-sound-conductive material, and in that at least one transducer configured to emit ultrasound is fastened to the net.
  • the net is a net cage enclosing the aquatic animals. It is preferably closed downwards and separates the animals from the surroundings.
  • the net may be a skirt hanging down from buoyancy means at the surface of the water.
  • the skirt will be open downwards, and is normally arranged around a net cage.
  • the system may comprises both a net cage as described above and a predator net, wherein the predator net is arranged around at least parts of the net cage.
  • Both the predator net and the net cage may be provided with a system according to the invention.
  • the net cages for aquatic animals may both be submerged cages, and cages at the surface of the water, preferably fish cages.
  • the water may be seawater, when the cage is arranged in the sea, or freshwater if the cage is arranged in a lake.
  • the aquatic animals may be any animal suitable for farming, such as crustaceans, shellfish or fish, preferably fish, even more preferred salmonids such as salmon or trout.
  • the system comprises a net surrounding the aquatic animals, and when the net is arranged in water, most parts of the net will be submerged.
  • the mesh size of the net is chosen according to the size of the animals, both to prevent the farmed animals escaping from the net, and to avoid any predators or fish from the environment to enter the net. Further, it is important that water may flow through the net to keep the water inside the net cage fresh and with sufficient concentration of oxygen.
  • the optimal mesh size is an obvious choice for a skilled person.
  • the threads of sound-conductive material may be of any suitable material being able to transmit or conduct ultrasound for a distance of at least 3 m. This means that the ultrasound should be transmitted at least 3 m away from the transducer, along the material.
  • the net cage When the net cage is arranged in water, it will at least partly be below the surface of the water, and thus the material must be solid and not be dissolvable in the water. Further, the material must withstand the environments of the net, including being submerged in seawater and exposed to water current.
  • the threads of sound-conductive material are interwoven in a net of non-sound- conductive material meaning that the threads are included in the material constituting the net.
  • the threads of sound-conductive material may be included along one of the strands of the rope, and twisted with the strand into the rope.
  • the threads of sound-conductive material may be in the centre of a braided rope, or along one of the strands of a braided rope.
  • the thread may be of metal, and have a diameter of at least 0,2 mm.
  • the non-sound-conductive material of the net is preferably a material traditionally used in fish cages, such as plastic or nylon, for instance Dyneema.
  • the material may be used as ropes tied or otherwise connected to each other to constitute a net having a mesh size allowing water to flow through.
  • Net cages are often referred to as “knotted” or “knotless” cages, which are wellknown nettings to a skilled person.
  • the weight of the net will be substantially lower than a net of only sound-conductive material, and the buoyancy of a traditional floating collar will be sufficient. Further the thread will be evenly distributed in the net and more protected from the wear and tear than if it was only added onto the net. As a metal thread is being a part of the net, the strength of the net will also increase, which is beneficial for the fish cage as a whole. The net will also be more resistant towards attacks from predators. Finally, as the thread is interwoven in the net, only the transducers must be fastened before the net is ready to use.
  • At least one transducer is fastened to the ultrasound transmitting / sound-conducting material.
  • the transducer is arranged to transmit ultrasound into the ultrasound transmitting / sound-conducting material of the net which then will scatter the ultrasound throughout the whole net. When the net is exposed to ultrasound, fouling will be reduced or not take place, and thereby the net will be clean.
  • Non-inertial cavitation is the process in which a bubble in a fluid is forced to oscillate in size or shape due to some form of energy input, such as ultrasound. If a biofilm is not created, no other kind of fouling will appear, and thereby the system according to the present invention will disrupt the formation and proliferation of marine colonies and provide an effective means of preventing mussels and barnacle larvae from attaching to net cages in seawater. The above mentioned problems for instance related to fouling, reduced flow of water and need for cleaning will be avoided.
  • the number of transducers needed to cover the whole net or at least parts of the net, and/or the optimal distance between transducers depends on a number of factors, such as the material and size of the sound-conductive threads and the frequency of the ultrasound being transmitted. Water also conducts ultrasound, and the water flow conditions at the location of the cage will thus also influence the number of transducers needed.
  • the transducers may be any regular transducers suitable to be submerged, and may be wired or battery-operated. In a preferred embodiment the transducers emits ultrasound in the frequency range of 15-100 kHz, preferably in the frequency range 20-60 kHz. The transducers may emit ultrasound constantly or at intervals depending on the amount of fouling.
  • the system may further comprise a central unit, wherein all the transducers are connected to the unit.
  • the central unit may be used to control and coordinate the frequency and/or interval of the ultrasound emitted by each of the transducers.
  • the central unit may further be arranged to give a signal if there is a break in any of the cables running to the transducers. A break in a cable may simply imply that there is a break in the wire leading to the transducer or in the transducer, but it may also imply that there is a hole in the net.
  • the system further comprises a system for wireless and remotely control of the transducers.
  • a system for wireless and remotely control of the transducers Such a system will enable remote control and the operator may be in safe environments onshore or in a barge, rather than on the exposed fish cage. Remote control also enables control and adjustment of the system more frequently and in a manner that is independent of the weather conditions.
  • the remote control system is preferably able to switch the transducers on and off, regulate the frequencies, and determine how long the pulses are and often the pulses are emitted (the interval between pulses).
  • the system for remote control preferably further comprises means for transferring data through mobile networks, radio signals, Bluetooth, Wi-Fi and/or underwater modems.
  • the system for wireless and remote control may be arranged to communicate with the central unit which then communicates with the transducers.
  • Reference to an ultrasound transmitting and/or a sound-conductive material may further be to a material that produces a small damping effect on the ultrasound signal as it passes through the material and along the threads forming the net.
  • Some metals will produce a relatively small damping effect on the signal (i.e. will not attenuate the ultrasound to any great degree) and are thus suitable for use as the threads of ultrasound transmitting / sound-conducting material comprised in the net of the fish cage. Aluminium, cobber and/or brass alloys, for example, or some types of steel, such as stainless steel may be suitable choices. These also will not corrode over time, which will obviously be an advantage when the system is used together with a fish cage.
  • the transducers coupled to the net are configured to produce sound waves which propagate into and across the ultrasound transmitting / sound-conductive material. If the sound waves are at ultrasound frequency then the transducers can be referred to as ultrasound transducers.
  • Suitable types of transducers for this purpose may include piezoelectric elements which are caused to vibrate in response to an AC signal to produce the sound waves, or metallic or non-metallic diaphragm transducers. Any type of transducer may, however, be used, provided that the signal emitted is in the ultrasound range and can propagate to and along the ultrasound transmitting/ sound-conducting material of the net.
  • the frequency of the ultrasound produced can be controlled by adjusting characteristics of the driving signal.
  • the frequency of the driving signal for example, can be used to adjust the frequency of the ultrasound signal produced.
  • the driving signal can also be controlled to produce a continuous ultrasound signal of constant or changing intensity, constant or changing frequency, or a pulsed signal with constant or changing frequency and/or intensity.
  • a square wave signal can be used as the driving signal for the transducer in some cases.
  • the control/driving signals may cause the set of transducers to emit ultrasound continuously, and at the same amplitude and frequency.
  • different transducers in the set may be caused to emit ultrasound at different frequencies or intensities. These may depend on the exact distribution of transducers across the net, and may be adjusted. The adjustment may be made in order to account for malfunctioning transducers in some cases.
  • a malfunctioning transducer which no longer produces a signal can be compensated for by adjacent transducers being operated to produce a higher intensity signal, for example.
  • a pulsed signal may be used in place of a continuous signal from one, several, or all of the transducers coupled to the net
  • the transducers may be coupled to the net in such a way that the ultrasound signal produced is transferred directly from the transducer (i.e. the moving elements of the transducer) to the ultrasound transmitting / sound-conductive material of the net. There may be no intervening material between the two, or air or water may be present. In any case, there will be little or no loss of signal between the transducer and the ultrasound transmitting / sound-conductive material at the location of the transducer.
  • the intensity and frequency of the ultrasound signal may be selected based on properties of the environment, and of the ultrasound transmitting / sound-conductive material that has been chosen to form part of the net.
  • a higher intensity signal may be required if attenuation by the ultrasound transmitting / sound-conductive material is higher, for example, to ensure that there is sufficient energy in the ultrasound signal to remove or prevent fouling in regions of the cage which are furthest from the transducers.
  • the attenuation will depend on the frequency of the signal and this may need to be adjusted accordingly.
  • a pulsed signal may also be preferable in some cases in order to reduce power consumption.
  • the transducers may be capable of both receiving and emitting ultrasound. This is simple to achieve with minimal change in transducer configuration. In a detecting mode, movement caused by the received signal (movement of the piezoelectric signals in the transducer, for example) results in an electric signal being produced, rather than the other way around as when the transducer is used to produce a signal.
  • the transducers can therefore also be used to test the performance of the system and/or the condition of the net. In a testing phase, one transducer can be caused to emit an ultrasound signal and the adjacent transducers can be set to detect the signal at their position.
  • the strength of the detected signal at the positions of the surrounding transducers may be used to detect holes in the net, for example, because of the intensity of the signal at an adjacent transducer where a hole in the net is present will be different If the received signal intensities at the adjacent transducers is found to be too low in the testing phase, the driving signal for the transducers can be adjusted to increase the intensity of the emitted ultrasound or to adapt the frequency to improve performance of the system.
  • This type of testing mechanism can be employed for groups of transducers in turn, varying those which acts to emit the ultrasound signal and those which act to detect the signal.
  • Control of the system may be via wireless or wired connection between the control unit and a user device.
  • the user device may be located at a large distance from the control unit, such as on a boat or on land, or may be located above the surface of the water on a structure supporting the fish cage.
  • a control signal can be sent from the user device to the control unit, which causes the desired driving signal to be produced for each of the transducers present in the system. If testing capability is provided, the detected signals at each of the transducers can be sent by the control unit back to the user device for processing, or can be processed at the control unit and a message or alert sent back to allow any necessary adaptions to be made to the system.
  • connection between the separate transducers and the control unit may also be via wireless or wired connection.
  • the transducers may each be equipped with an antenna, which may be fairly compact. Communication signals must obviously be capable of being sent through water.
  • the transducers can be electrically connected together in some cases. Power for the transducers can be provided through this connection or using batteries within the separate units, which will then need to be replaced periodically.
  • the transducers can potentially include energy harvesting capabilities to reduce energy consumption. They could, for example, be configured to harvest light using photovoltaic cells or energy from water currents.
  • the invention in another aspect, relates to a net to be used in a system as described above wherein the net has a mesh size allowing water to flow through and wherein the net comprises a solid, ultrasound transmitting / sound-conducting material interwoven in non-sound-conductive material.
  • the invention in another aspect, relates to a net cage to be used in a system as described above, wherein the net cage have a mesh size allowing water to flow through and wherein in that threads of sound-conductive material is interwoven in a net of non-sound-conductive material.
  • the invention relates to use of a system, net and/or net cage as described above for farming fish in the sea, wherein the net surrounds the fish to be farmed.
  • FIG 1 showing a system according to the invention, arranged on a fish cage
  • Figure 2 showing an enlarged part of the fish cage in Figure 1
  • Figure 3 showing a control unit. Description of preferred embodiments of the invention
  • FIG. 1 shows a system according to the invention, arranged on a traditional fish cage.
  • the fish cage comprises a floating collar 1 at the surface of the sea, and a hand rail 2 above the surface.
  • a net cage having a cylindrical wall 3, and a conical bottom 4, is attached to the floating collar and protruding down into the sea.
  • a number of fish 5 is enclosed by the net cage.
  • the whole net cage is made of threads of Nylon, or polymers such as Polyester, being a non-sound-conductive material, having threads of metal being a sound- conductive material, interwoven into the net.
  • twelve transducers 6 are attached to the net, one row of transducers at the upper part of the net cage, and one row at the bottom of the cylindrical wall. The pattern of the transducers may be adjusted according to the material of the net cage and local conditions.
  • the transducers may be placed spaced apart so that the maximum distance between adjacent transducers is roughly equal to the distance which ultrasound at the frequency used can travel through the ultrasound transmitting / sound-conducting material (or along the threads formed of the ultrasound transmitting material) before it’s intensity or amplitude is reduced to 10% of its initial value.
  • the shown transducers are Piezoelectric transducers.
  • Figure 2 shows an enlarged section of Figure 1.
  • the net 10 is made of threads 11 of ultrasound transmitting / sound-conductive material, interwoven in non-sound- conductive material connected to each other to create a net.
  • transducers 12 are fastened at a distance of 3 m from each other. In this arrangement, ultrasound will be transferred to the whole net, and no fouling will occur.
  • FIG. 3 shows a combined central and control unit to be used with the fish cage shown in Figure or the net shown in Figure 2.
  • the unit comprises ports 13 for power supply and a display 14 for showing system status.
  • an antenna is integrated into the unit, and information is transferred to a monitoring unit through mobile networks, radio signals, Bluetooth, Wi-Fi and/or underwater modems.
  • a monitoring unit may be connected via port 15.
  • the transducers being a part of the system, are connected to the ports 16 of the unit. For clarity only two ports 16 for transducers are shown, but the number will be adjusted according to the specific use.
  • the unit may be designed in any suitable way, and should be adapted to withstand the harsh environments of a fish cage.

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  • Life Sciences & Earth Sciences (AREA)
  • Environmental Sciences (AREA)
  • Marine Sciences & Fisheries (AREA)
  • Zoology (AREA)
  • Animal Husbandry (AREA)
  • Biodiversity & Conservation Biology (AREA)
  • Agricultural Chemicals And Associated Chemicals (AREA)
  • Catching Or Destruction (AREA)

Abstract

System for preventing fouling on cages for aquatic animals in water, wherein thesystem comprises a net for surrounding the aquatic animals, and having a mesh size allowing water to flow through. The net comprises threads of sound-conductive material interwoven in non-sound-conductive material, and in that at least one transducer (6; 12) configured to emit ultrasound is fastened to the net.

Description

System for preventing fouling on cages for aquatic animals in water.
The present invention relates a system for preventing fouling on cages for farming aquatic animals in water, and a net to be used in such a system and use of such a system according to the preamble of the independent patent claims.
Aquaculture is a major industry, and most of the farmed animals are farmed in fish cages at the sea. A traditional fish cage comprises a floating collar at the surface of the sea, a net surrounding the farmed organisms and fastened to the collar, the net is often referred to as net cage, and weights to keep the cage dilated and stretched and in such a way that the meshes of the net is open. The mesh size of the net should be adjusted in such a way that the farmed organisms are kept inside the cage, yet allowing water to flow through the mesh, in and out of the cage.
The floating collars are traditionally round or square and comprises two or three circular tubes of plastic arranged outside of each other and fastened to each other by steel or plastic brackets. The net cage traditionally comprises a net wall and net bottom, the bottom may be flat or shaped as a cone. The weight may be any suitable weight, such as a sinker tube.
Another well known type of fish cage in the water is a rigid frame covered by a net of metal or textile, and attached to buoyancy means, either floating collars as mentioned above, floating barges, or similar means. The net will thus be expanded by the frame, and weights will not be necessary.
The floating collar or other buoyancy means must be designed to have sufficient buoyancy to carry the weight of the whole fish cage, including possible rigid frames, weights and other equipment. The buoyancy must be sufficient to keep the net cage at the surface of the water even during strong water current, rough weather and high waves. The design of a traditional floating collar can only give a limited buoyancy without being comprehensively re-designed. The weight of the net cage and equipment should therefore be reduced as much as possible. There is however a problem with debris and fouling of the net in the fish cages, regardless of how the cage is arranged. Especially during summer and in areas with higher water temperature, algae, barnacles, shells and similar attach to the net and grow. The fouling will prevent water from flowing through the net, and thus the water inside the fish cage will not be as fresh as desired, which may lead to less growth and reduced fish health. The oxygen level in the fish cage may become reduced when the net is very fouled. Further, fouling and debris will create a hiding place for parasites such as sea lice, irritant hydroids, parasite eggs and larvae, and organisms causing diseases such as amoebic gill disease. Yet another problem with fouling is that cleaning fish, such as wrasses or lumpfish, prefer to feed off the fouling rather than the sea lice on the fish.
To avoid the fouling, the net may be made of a material preventing fouling, yet withstanding the harsh and corrosive environments at the sea, offering sufficient strength and ensuring the fish welfare. Such materials are however not efficient in preventing fouling over time. Different types of coating have also been used, however, the coating will lose its effect after a short period of time in the sea, and/or it will be washed or torn off. The coatings may comprise poisonous compounds, and further they may dissolve or loosen from the net and leak into the surrounding sea. This may reduce the welfare of the fish in the fish cage, and the environment around the fish cage.
When fouling appears, the cage has to be cleaned, traditionally by net washing machines or cleaners, which flush the net with water from a number of nozzles, or clean the net with brushes. This wears the net and may reduce the thickness of the material of the net releasing particles of plastic from the net into the net cage and surroundings. If the net is covered by antifouling agent the layer will be reduced or even removed during the cleaning process. Further, most washing procedures needs to be supervised by a human, they are time-consuming and consumes fuel during use. The loosened fouling released into fish cage may also disturb the fish and affect the fish health negatively. Objects of the present invention
Based on the above, there is a main object to develop an improved system for avoiding fouling of the net. Another object is to develop a system for cleaning the net if fouling has developed, without any of the problems mentioned above. Yet another object is that the system should be easy to use and to install on new and existing aquaculture farms. Finally, there is an object to develop a system for avoiding and/or cleaning the net which may be controlled remotely, for instance from ashore.
Summary of the invention
The objects are met with a system and a net cage according to the characterizing parts of the independent claims.
The invention relates to a system for preventing fouling on cages for aquatic animals in water. The system comprises a net surrounding the aquatic animals, and having a mesh size allowing water to flow through, wherein the net comprises threads of sound-conductive material interwoven in a net of non-sound-conductive material, and in that at least one transducer configured to emit ultrasound is fastened to the net.
The net is a net cage enclosing the aquatic animals. It is preferably closed downwards and separates the animals from the surroundings.
In an alternative embodiment, the net may be a skirt hanging down from buoyancy means at the surface of the water. The skirt will be open downwards, and is normally arranged around a net cage.
In another alternative embodiment the system may comprises both a net cage as described above and a predator net, wherein the predator net is arranged around at least parts of the net cage. Both the predator net and the net cage may be provided with a system according to the invention. The net cages for aquatic animals may both be submerged cages, and cages at the surface of the water, preferably fish cages. The water may be seawater, when the cage is arranged in the sea, or freshwater if the cage is arranged in a lake. The aquatic animals may be any animal suitable for farming, such as crustaceans, shellfish or fish, preferably fish, even more preferred salmonids such as salmon or trout.
The system comprises a net surrounding the aquatic animals, and when the net is arranged in water, most parts of the net will be submerged. The mesh size of the net is chosen according to the size of the animals, both to prevent the farmed animals escaping from the net, and to avoid any predators or fish from the environment to enter the net. Further, it is important that water may flow through the net to keep the water inside the net cage fresh and with sufficient concentration of oxygen. The optimal mesh size is an obvious choice for a skilled person.
The threads of sound-conductive material may be of any suitable material being able to transmit or conduct ultrasound for a distance of at least 3 m. This means that the ultrasound should be transmitted at least 3 m away from the transducer, along the material. When the net cage is arranged in water, it will at least partly be below the surface of the water, and thus the material must be solid and not be dissolvable in the water. Further, the material must withstand the environments of the net, including being submerged in seawater and exposed to water current.
The threads of sound-conductive material are interwoven in a net of non-sound- conductive material meaning that the threads are included in the material constituting the net. For instance, when the net is made of rope, the threads of sound-conductive material may be included along one of the strands of the rope, and twisted with the strand into the rope. Alternatively the threads of sound-conductive material may be in the centre of a braided rope, or along one of the strands of a braided rope. The thread may be of metal, and have a diameter of at least 0,2 mm. The non-sound-conductive material of the net is preferably a material traditionally used in fish cages, such as plastic or nylon, for instance Dyneema. The material may be used as ropes tied or otherwise connected to each other to constitute a net having a mesh size allowing water to flow through. Net cages are often referred to as "knotted" or "knotless" cages, which are wellknown nettings to a skilled person.
By having the threads interwoven in the net as described above, the weight of the net will be substantially lower than a net of only sound-conductive material, and the buoyancy of a traditional floating collar will be sufficient. Further the thread will be evenly distributed in the net and more protected from the wear and tear than if it was only added onto the net. As a metal thread is being a part of the net, the strength of the net will also increase, which is beneficial for the fish cage as a whole. The net will also be more resistant towards attacks from predators. Finally, as the thread is interwoven in the net, only the transducers must be fastened before the net is ready to use.
At least one transducer is fastened to the ultrasound transmitting / sound-conducting material. The transducer is arranged to transmit ultrasound into the ultrasound transmitting / sound-conducting material of the net which then will scatter the ultrasound throughout the whole net. When the net is exposed to ultrasound, fouling will be reduced or not take place, and thereby the net will be clean.
When the transducers fastened to the net comprising threads of sound-conductive material, emit ultrasound, non-inertial cavitation will occur along the net and prevent bio-fouling and growth of biofilm on the net. Non-inertial cavitation is the process in which a bubble in a fluid is forced to oscillate in size or shape due to some form of energy input, such as ultrasound. If a biofilm is not created, no other kind of fouling will appear, and thereby the system according to the present invention will disrupt the formation and proliferation of marine colonies and provide an effective means of preventing mussels and barnacle larvae from attaching to net cages in seawater. The above mentioned problems for instance related to fouling, reduced flow of water and need for cleaning will be avoided. The number of transducers needed to cover the whole net or at least parts of the net, and/or the optimal distance between transducers, depends on a number of factors, such as the material and size of the sound-conductive threads and the frequency of the ultrasound being transmitted. Water also conducts ultrasound, and the water flow conditions at the location of the cage will thus also influence the number of transducers needed.
The transducers may be any regular transducers suitable to be submerged, and may be wired or battery-operated. In a preferred embodiment the transducers emits ultrasound in the frequency range of 15-100 kHz, preferably in the frequency range 20-60 kHz. The transducers may emit ultrasound constantly or at intervals depending on the amount of fouling.
The system may further comprise a central unit, wherein all the transducers are connected to the unit. The central unit may be used to control and coordinate the frequency and/or interval of the ultrasound emitted by each of the transducers. The central unit may further be arranged to give a signal if there is a break in any of the cables running to the transducers. A break in a cable may simply imply that there is a break in the wire leading to the transducer or in the transducer, but it may also imply that there is a hole in the net.
In another preferred embodiment, the system further comprises a system for wireless and remotely control of the transducers. Such a system will enable remote control and the operator may be in safe environments onshore or in a barge, rather than on the exposed fish cage. Remote control also enables control and adjustment of the system more frequently and in a manner that is independent of the weather conditions. The remote control system is preferably able to switch the transducers on and off, regulate the frequencies, and determine how long the pulses are and often the pulses are emitted (the interval between pulses). The system for remote control preferably further comprises means for transferring data through mobile networks, radio signals, Bluetooth, Wi-Fi and/or underwater modems. In embodiments wherein the system comprises a central unit, then the system for wireless and remote control may be arranged to communicate with the central unit which then communicates with the transducers.
Reference to an ultrasound transmitting and/or a sound-conductive material may further be to a material that produces a small damping effect on the ultrasound signal as it passes through the material and along the threads forming the net. For example, a material that, in the case of a 20 kHz signal, will allow ultrasound to travel at least 0.5 m, preferably at least 1 m, most preferred at least 3 m away from the transducer, through the material and along the net before the intensity is reduced to a level where non-inertial cavitation is no longer induced.
Some metals will produce a relatively small damping effect on the signal (i.e. will not attenuate the ultrasound to any great degree) and are thus suitable for use as the threads of ultrasound transmitting / sound-conducting material comprised in the net of the fish cage. Aluminium, cobber and/or brass alloys, for example, or some types of steel, such as stainless steel may be suitable choices. These also will not corrode over time, which will obviously be an advantage when the system is used together with a fish cage.
Traditional materials used to form the net of a fish cage may also transmit ultrasound, at least to a degree, but will not allow the ultrasound to propagate to the distances mentioned above and so cannot be considered an ultrasound transmitting/ sound-conducting material in the sense referred to herein. The signal may also propagate through the water surrounding the fish, and potentially the body tissues of the fish themselves, however this should not be an issue provided that the no damage or disturbance is caused to the fish. Lower ultrasound frequencies may be preferred for this reason. The transducers coupled to the net are configured to produce sound waves which propagate into and across the ultrasound transmitting / sound-conductive material. If the sound waves are at ultrasound frequency then the transducers can be referred to as ultrasound transducers. Suitable types of transducers for this purpose may include piezoelectric elements which are caused to vibrate in response to an AC signal to produce the sound waves, or metallic or non-metallic diaphragm transducers. Any type of transducer may, however, be used, provided that the signal emitted is in the ultrasound range and can propagate to and along the ultrasound transmitting/ sound-conducting material of the net.
The frequency of the ultrasound produced can be controlled by adjusting characteristics of the driving signal. The frequency of the driving signal, for example, can be used to adjust the frequency of the ultrasound signal produced. The driving signal can also be controlled to produce a continuous ultrasound signal of constant or changing intensity, constant or changing frequency, or a pulsed signal with constant or changing frequency and/or intensity. A square wave signal can be used as the driving signal for the transducer in some cases.
The control/driving signals may cause the set of transducers to emit ultrasound continuously, and at the same amplitude and frequency. Alternatively, different transducers in the set may be caused to emit ultrasound at different frequencies or intensities. These may depend on the exact distribution of transducers across the net, and may be adjusted. The adjustment may be made in order to account for malfunctioning transducers in some cases. A malfunctioning transducer which no longer produces a signal can be compensated for by adjacent transducers being operated to produce a higher intensity signal, for example. A pulsed signal may be used in place of a continuous signal from one, several, or all of the transducers coupled to the net
The transducers may be coupled to the net in such a way that the ultrasound signal produced is transferred directly from the transducer (i.e. the moving elements of the transducer) to the ultrasound transmitting / sound-conductive material of the net. There may be no intervening material between the two, or air or water may be present. In any case, there will be little or no loss of signal between the transducer and the ultrasound transmitting / sound-conductive material at the location of the transducer.
The intensity and frequency of the ultrasound signal may be selected based on properties of the environment, and of the ultrasound transmitting / sound-conductive material that has been chosen to form part of the net. A higher intensity signal may be required if attenuation by the ultrasound transmitting / sound-conductive material is higher, for example, to ensure that there is sufficient energy in the ultrasound signal to remove or prevent fouling in regions of the cage which are furthest from the transducers. Similarly, the attenuation will depend on the frequency of the signal and this may need to be adjusted accordingly. A pulsed signal may also be preferable in some cases in order to reduce power consumption.
The transducers may be capable of both receiving and emitting ultrasound. This is simple to achieve with minimal change in transducer configuration. In a detecting mode, movement caused by the received signal (movement of the piezoelectric signals in the transducer, for example) results in an electric signal being produced, rather than the other way around as when the transducer is used to produce a signal. The transducers can therefore also be used to test the performance of the system and/or the condition of the net. In a testing phase, one transducer can be caused to emit an ultrasound signal and the adjacent transducers can be set to detect the signal at their position.
The strength of the detected signal at the positions of the surrounding transducers may be used to detect holes in the net, for example, because of the intensity of the signal at an adjacent transducer where a hole in the net is present will be different If the received signal intensities at the adjacent transducers is found to be too low in the testing phase, the driving signal for the transducers can be adjusted to increase the intensity of the emitted ultrasound or to adapt the frequency to improve performance of the system. This type of testing mechanism can be employed for groups of transducers in turn, varying those which acts to emit the ultrasound signal and those which act to detect the signal.
Control of the system may be via wireless or wired connection between the control unit and a user device. The user device may be located at a large distance from the control unit, such as on a boat or on land, or may be located above the surface of the water on a structure supporting the fish cage. A control signal can be sent from the user device to the control unit, which causes the desired driving signal to be produced for each of the transducers present in the system. If testing capability is provided, the detected signals at each of the transducers can be sent by the control unit back to the user device for processing, or can be processed at the control unit and a message or alert sent back to allow any necessary adaptions to be made to the system.
Connection between the separate transducers and the control unit may also be via wireless or wired connection. In the former case, the transducers may each be equipped with an antenna, which may be fairly compact. Communication signals must obviously be capable of being sent through water. The transducers can be electrically connected together in some cases. Power for the transducers can be provided through this connection or using batteries within the separate units, which will then need to be replaced periodically. The transducers can potentially include energy harvesting capabilities to reduce energy consumption. They could, for example, be configured to harvest light using photovoltaic cells or energy from water currents.
In another aspect, the invention relates to a net to be used in a system as described above wherein the net has a mesh size allowing water to flow through and wherein the net comprises a solid, ultrasound transmitting / sound-conducting material interwoven in non-sound-conductive material.
In another aspect, the invention relates to a net cage to be used in a system as described above, wherein the net cage have a mesh size allowing water to flow through and wherein in that threads of sound-conductive material is interwoven in a net of non-sound-conductive material.
In yet another aspect, the invention relates to use of a system, net and/or net cage as described above for farming fish in the sea, wherein the net surrounds the fish to be farmed.
Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
The following description of an exemplary embodiment refers to the figures, and the following detailed description is not meant or intended to limit the invention. Instead, the scope of the invention is defined by the appended claims.
Description of the figures
The invention will now be described with the help of the enclosed figures, showing the principles of a system according to the present invention. The different parts of the figure are not necessarily in scale to each other, as the figure is merely for illustrating the invention.
The invention is illustrated by
Figure 1 showing a system according to the invention, arranged on a fish cage, Figure 2 showing an enlarged part of the fish cage in Figure 1 , and Figure 3 showing a control unit. Description of preferred embodiments of the invention
Figure 1 shows a system according to the invention, arranged on a traditional fish cage. The fish cage comprises a floating collar 1 at the surface of the sea, and a hand rail 2 above the surface. A net cage having a cylindrical wall 3, and a conical bottom 4, is attached to the floating collar and protruding down into the sea. A number of fish 5 is enclosed by the net cage.
The whole net cage is made of threads of Nylon, or polymers such as Polyester, being a non-sound-conductive material, having threads of metal being a sound- conductive material, interwoven into the net. In the shown embodiment, twelve transducers 6 are attached to the net, one row of transducers at the upper part of the net cage, and one row at the bottom of the cylindrical wall. The pattern of the transducers may be adjusted according to the material of the net cage and local conditions. The transducers may be placed spaced apart so that the maximum distance between adjacent transducers is roughly equal to the distance which ultrasound at the frequency used can travel through the ultrasound transmitting / sound-conducting material (or along the threads formed of the ultrasound transmitting material) before it’s intensity or amplitude is reduced to 10% of its initial value. The shown transducers are Piezoelectric transducers.
Figure 2 shows an enlarged section of Figure 1.. The net 10 is made of threads 11 of ultrasound transmitting / sound-conductive material, interwoven in non-sound- conductive material connected to each other to create a net. In the shown section of the net four transducers 12 are fastened at a distance of 3 m from each other. In this arrangement, ultrasound will be transferred to the whole net, and no fouling will occur.
Figure 3 shows a combined central and control unit to be used with the fish cage shown in Figure or the net shown in Figure 2. The unit comprises ports 13 for power supply and a display 14 for showing system status. In some cases an antenna is integrated into the unit, and information is transferred to a monitoring unit through mobile networks, radio signals, Bluetooth, Wi-Fi and/or underwater modems. A monitoring unit may be connected via port 15. The transducers, being a part of the system, are connected to the ports 16 of the unit. For clarity only two ports 16 for transducers are shown, but the number will be adjusted according to the specific use. The unit may be designed in any suitable way, and should be adapted to withstand the harsh environments of a fish cage.
The example above is given to illustrate the invention and should not be used to interpret the following claims limiting. The scope of the invention is not limited by the example given above, but the following claims. Modifications and amendments of the invention, being obvious to a person skilled of the art, should also be included in the scope of the invention.

Claims

Claims
1. System for preventing fouling on cages for aquatic animals in water, wherein the system comprises a net (3) for surrounding the aquatic animals, and having a mesh size allowing water to flow through, characterized in that the net (3) comprises threads of sound-conductive material interwoven in a net of non-sound-conductive material, and in that at least one transducer (6; 12) configured to emit ultrasound is fastened to the net.
2. System according to any one of the preceding claims, characterized in that the transducers are configured to emit ultrasound constantly.
3. System according to any one of the preceding claims, characterized in that the transducers are configured to emit ultrasound in the frequency range of 15-100 kHz, preferably in the frequency range 20-60 kHz.
4. System according to any one of the preceding claims, characterized by comprising a central unit, and in that the transducers are connected to the central unit, which controls the frequency and/or interval of the emitted ultrasound.
5. System according to any one of the preceding claims, characterized in that the system further comprises a system for wireless and remotely control of the transducers.
6. System according to claim 5, characterized that the control system comprises means for transferring data through mobile networks, radio signals, Bluetooth, Wi-Fi and/or submarine modems.
7. A net to be used in a system according to any one of claims 1-6 above, characterized in that the net have a mesh size allowing water to flow through, and comprises threads of sound-conductive material interwoven in a net of non-sound- conductive material.
8. Use of a system according to any one of claims 1-6, and/or a net according to claim 7, for farming fish in the sea, wherein the net surrounds the fish to be farmed.
PCT/NO2022/050024 2021-01-27 2022-01-27 System for preventing fouling on cages for aquatic animals in water WO2022164325A1 (en)

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Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DK149661B (en) * 1979-01-17 1986-09-01 Fritz Hansen Apparatus for indication of damaged spots on a trawl net
JPH08182448A (en) * 1994-12-28 1996-07-16 Honda Electron Co Ltd Ultrasonic fishing net
JP2607089B2 (en) * 1987-07-26 1997-05-07 本多電子株式会社 Ultrasonic fish net
JPH09275882A (en) * 1996-04-19 1997-10-28 Nohmi Bosai Ltd Adhesion-proofing system for organism spoiling underwater equipment or the like
WO2003003823A1 (en) * 2001-07-06 2003-01-16 Larsen Leif Erik Electronically monitored fish farm net and method
WO2009038471A1 (en) * 2007-09-18 2009-03-26 Sfd As A method and device for reducing the influence of unwanted organisms in a marine farming facility
JP2012115631A (en) * 2010-12-02 2012-06-21 Ogi Hiroko Indwelling device
WO2013051725A1 (en) * 2011-10-04 2013-04-11 株式会社Ihi Sanitation management method of farmed fish and device thereof
GB2505992A (en) * 2012-07-12 2014-03-19 Ace Aquatec Ltd Predator deterrent system
JP2019033698A (en) * 2017-08-17 2019-03-07 株式会社Ihi Ultrasonic irradiation apparatus used for sanitary control of culture facility, and ultrasonic irradiation method
WO2020048945A1 (en) * 2018-09-05 2020-03-12 Seasel Solutions As System and method for reducing sea lice exposure in marine fish farming

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9439402B2 (en) * 2008-08-27 2016-09-13 Ecosea Farming S.A. Aquaculture net and flotation structure
GB2479375A (en) * 2010-04-07 2011-10-12 Ian Alistair Ritchie Ultrasonic membrane for inhibiting marine growth
CL2010000933A1 (en) * 2010-09-01 2011-02-18 Prado Lavin Rodrigo Method for the control of marine larvae components of the zooplankton that adheres on submerged marine surfaces that includes the application of ultrasound waves under water.
KR101774922B1 (en) * 2015-11-03 2017-09-19 삼성중공업(주) Anti-fouling apparatus of ship
CH714301A2 (en) * 2017-11-05 2019-05-15 Prokic Livingstone Miodrag New method for preventing the formation of biofilm and algae.

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DK149661B (en) * 1979-01-17 1986-09-01 Fritz Hansen Apparatus for indication of damaged spots on a trawl net
JP2607089B2 (en) * 1987-07-26 1997-05-07 本多電子株式会社 Ultrasonic fish net
JPH08182448A (en) * 1994-12-28 1996-07-16 Honda Electron Co Ltd Ultrasonic fishing net
JPH09275882A (en) * 1996-04-19 1997-10-28 Nohmi Bosai Ltd Adhesion-proofing system for organism spoiling underwater equipment or the like
WO2003003823A1 (en) * 2001-07-06 2003-01-16 Larsen Leif Erik Electronically monitored fish farm net and method
WO2009038471A1 (en) * 2007-09-18 2009-03-26 Sfd As A method and device for reducing the influence of unwanted organisms in a marine farming facility
JP2012115631A (en) * 2010-12-02 2012-06-21 Ogi Hiroko Indwelling device
WO2013051725A1 (en) * 2011-10-04 2013-04-11 株式会社Ihi Sanitation management method of farmed fish and device thereof
GB2505992A (en) * 2012-07-12 2014-03-19 Ace Aquatec Ltd Predator deterrent system
JP2019033698A (en) * 2017-08-17 2019-03-07 株式会社Ihi Ultrasonic irradiation apparatus used for sanitary control of culture facility, and ultrasonic irradiation method
WO2020048945A1 (en) * 2018-09-05 2020-03-12 Seasel Solutions As System and method for reducing sea lice exposure in marine fish farming

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