A system configured to protect aquaculture installations from marine biological threats

Abstract

The present invention concerns an electromagnetic deterrent system (10) being configured for at least one net cage (20) configured for breeding of farmed fish and comprising a plurality of electrodes (13) arranged in groups.

Description

[0001] A system configured to protect aquaculture installations from marine biological threats

[0002] TECHNICAL FIELD

[0003] The present invention relates to a system for a net cage provided with means to keep sharks or other marine predators and / or parasites away from a side wall and bottom or lower portions of net(s) in the net cage so that the sharks will not make holes in the side wall or bottom portions of the net(s) in the net cage in order to enter into the net cage that is configured for breeding of farmed fish. More specifically, the present invention relates to constituting an electromagnetic field around at least a lower or bottom part of the net cage. The generated electromagnetic field can be time dependent, such as e.g. intermittent or periodic. The generated electromagnetic field affects the shark's or predator’s ability to orient, in particular by e.g. affecting the shark's electroreceptors so that the shark is either startled, experiences discomfort, loses orientation or is scared away in the vicinity of the net cage.

[0004] BACKGROUND OF THE INVENTION

[0005] A net cage or net pen configured for breeding of e.g. salmon or other farmed fish in seawater can be shaped in different ways, e.g. a net cage comprising a frame with a vertical side wall and in a conical bottom enclosed by nets. The nets of the net cage form an enclosure for farmed fish in the net cage. The net cage can also be equipped with a floatation ring or frame on which the net can be arranged. In addition, the frame and the net of the net cage can continue up to a certain height above the water surface in order to constitute a frame-and-net fence encircling the net cage and to prevent the farmed fish from escaping from the net cage by jumping over the net cage.

[0006] It is important to keep the net intact as the farmed fish in the net cage will find holes and openings that can occur in the net and will escape from the net cage through such holes and openings in the net. It is known that farmed salmon in seawater can be attacked by external parasites, such as salmon lice (Lepeophtheirus salmonis). It is also known that so-called cleaning fish are used in net cages in order to reduce the number of salmon lice.

[0007] Dead salmon or farmed fish in the net cage will sink to the bottom of the net cage. Dead cleaning fish in the net cage will also sink to the bottom thereof. Such dead fish are attractive to marine organisms or predators that can feed on dead fish.

[0008] Spiny dogfish or grayfish (Squalus acanthias) is a small species of shark that can grow up to 1 ,2 m in length and can weigh up to 9 kg. Dogfishes or grayfishes can act in (substantial) shoals. Dogfishes or grayfishes can eat carcass or carrion (such as e.g. dead fish). It is therefore a problem that dogfishes or grayfishes attack a side wall and / or a lower or bottom portion of the net cage in order to get to the dead fish inside the net cage. Dogfishes or grayfishes, like other shark species, have sharp teeth and can bite through threads of the net of the net cage. Such an attack by dogfishes or grayfishes can cause holes in the net and damage to the net cage, and farmed fish inside the net cage can escape.

[0009] Sharks have very sensitive sensory structure or sense organs in their skin that can register small electromagnetic signals from e.g. a prey. These electroreceptors are called Lorenzini's ampulla I ampullae of Lorenzini. These electroreceptors enable sharks to sense an electromagnetic field generated by e.g. a prey's muscle movements). It is also known that many fish species, including shark species, show an avoidance response to electromagnetic fields above certain threshold values. It is also well known that fish species, including sharks can be kept out of an area by means of a pulsating electromagnetic field. It is believed that a strong enough electromagnetic field causes unpleasant stimuli on the skin of the fish. With a field of sufficient strength, unvoluntary muscle movements can be induced on fish. Three phenomena are observed with increasing electromagnetic field strength:

[0010] 1 ) Fright reaction - the fish reacts as startled.

[0011] 2) Electro taxis - the fish has no control over its swimming direction and tends towards the positive electrode. 3) Electronarcosis - at higher electromagnetic field strengths fish loose complete control over their muscles resulting in the fish remaining motionless until the field is removed.

[0012] The electro taxis reaction or response is used effectively in fresh water to catch fish and to create barriers to keep target fish species out of certain areas (e.g. electric fish screens). Such installations commonly aim to induce the fright reaction response.

[0013] From published research it is known that several shark species react to pulsed electromagnetic fields in the manner described above. From the published results it is both known the effectiveness of pulse shape and duration, frequency, and necessary field strength to achieve both the fright and electro taxis reaction I response as function of size (length) of the shark. There is very limited experience with the use of strong electromagnetic fields to keep spiny dogfish (Squalus acanthias) away from bait / dead fish in both line fishing and specifically in aquaculture operations.

[0014] In aquaculture operations, such as net cages used for breeding farmed fish, various methods and technologies can be employed in order to protect the farmed fish from marine biological threats, such as for example marine organisms and / or predators, including sharks, parasites, such as for example fish lice, etc. Some common approaches configured to deter and keep predators away from the net cages comprise:

[0015] Anti-predator netting can be used for aquaculture and can be designed with anti-predator features, such as stronger and thicker net materials, to deter larger predators such as e.g. sharks. These nets are more difficult for predators to breach.

[0016] Bird netting can be used to prevent seabirds or fish-eating birds and other avian predators from diving into the net cages to catch fish. This type of netting is usually placed above the water surface.

[0017] Sonic deterrents can be used. Acoustic deterrent devices can emit underwater sounds or vibrations that are unpleasant or frightening to marine predators. These devices can help deter sharks and other predators from approaching the net cages. Seal or sea lion deterrents can be used in areas with seal or sea lion predators, wherein physical barriers, such as e.g. anti-predator grids or platforms, can be used to prevent these animals from accessing the net cages.

[0018] Floating enclosures or barriers can be incorporated in some aquaculture systems in order to create a physical separation between the farmed fish and any potential predators.

[0019] Floating buoy lines with attached nets or barriers can be used as a secondary defense against predators such as e.g. sharks, etc. The buoy lines can create a physical barrier around the net cages, making it more difficult for predators to approach.

[0020] Monitoring and surveillance of the net cages and the surrounding waters on a regular basis can be helpful to identify and respond to potential predator threats in real time.

[0021] It's important to note that the specific methods used can vary depending on the type of farmed fish, the location of the aquaculture operation, and the types of predators that pose a threat. Additionally, the effectiveness of predator deterrents can depend on various factors, and continuous research and development of anti-predator technologies are ongoing in the aquaculture industry in order to ensure the safety of farmed fish and the sustainability of aquaculture practices.

[0022] Recently, electromagnetic or magnetic fields have been explored as a potential means of deterring sharks and other marine predators from approaching the net cages in aquaculture operations. The concept is based on the sensitivity of sharks and some other marine animals to electromagnetic fields, as they possess the previously mentioned electroreceptors that can be detecting electrical signals.

[0023] Several companies and researchers have developed and tested devices that generate electromagnetic fields around the net cages to deter sharks or other predators. These devices typically work as follows:

[0024] Electric fields, where some systems can create electric fields around the net cages. Sharks may sense these fields and avoid the area, as they can perceive them as uncomfortable or even painful. Magnetic fields, where magnetic field-generating devices can be another approach. These devices emit strong, oscillating magnetic field(s) that can interfere with a shark's ability to detect prey or navigate effectively. The oscillating magnetic field(s) can thus create a corresponding oscillating electric field in seawater.

[0025] While the use of electromagnetic fields is an intriguing concept, it's important to note that their effectiveness as a shark deterrent in aquaculture operations is still a subject of ongoing research and development. Some key considerations and challenges include:

[0026] Species-specific sensitivity should be considered. The effectiveness of electromagnetic fields can vary depending on the species of sharks and other marine predators present in the area.

[0027] Environmental factors and conditions as well as water depth can affect the propagation of electromagnetic fields and their ability to deter predators.

[0028] Safety and compliance should be considered as the use of electromagnetic fields in aquaculture should in many cases be complied with different environmental regulations and safety standards. There is a need to ensure that these magnetic fields do not harm non-target species or the surrounding ecosystem(s).

[0029] Cost and practicality of implementing electromagnetic field systems in aquaculture operations should be considered. It may not be feasible for all aquaculture facilities.

[0030] Research and field testing are ongoing in order to improve the design and effectiveness of electromagnetic deterrent systems for aquaculture. While promising, these systems are not yet widely adopted but could become a valuable tool for protecting farmed fish from predators like sharks.

[0031] Different tests have shown that a drawback of the known technique, using electromagnetic fields, is that some of the components in the known electromagnetic deterrent systems do not last long (cannot last more than 2-3 months, and they usually last just about 2 weeks) and must be changed quite frequently.

[0032] SUMMARY OF THE INVENTION It is an object of the present invention to provide a system configured to be used in an aquaculture installation with at least one net cage and to keep marine biological threats and / or hazards, such as, but not limited to, for example sharks and / or other predators and / or parasites, from compromising a net in a net cage and / or from getting into the net cage with farmed fish.

[0033] Another object of the invention is to remedy or reduce at least one of the disadvantages of the known techniques, or at least to provide a useful alternative to the known techniques.

[0034] Yet another object of the invention is to provide an electromagnetic deterrent system for a net cage, which system is maintenance-free for at least 6 months and preferably for at least one life cycle of the farmed fish, which for farmed salmon is from about 10 to about 15 months.

[0035] Yet another object of the invention is to provide an electromagnetic deterrent system for a net cage causing a fright reaction or response with sharks or other predators and / or parasites when approaching a net in the net cage.

[0036] Yet another object of the invention is to provide an electromagnetic deterrent system for a net cage causing an electro taxis reaction or response with sharks or other predators and / or parasites when approaching a net in the net cage.

[0037] According to a first aspect of the invention this is achieved with the features indicated in the description below and in the subsequent patent claims.

[0038] The present invention teaches an electromagnetic deterrent system configured for at least one net cage configured for breeding of farmed fish. The system comprises a mesh constituted of vertical and / or horizontal wires on which at least two groups of electrodes are arranged at respective nodes on the mesh. The nodes are arranged with a predetermined distance from each other. The mesh of the electromagnetic deterrent system is arranged to an upper ring or frame or between the upper ring or frame and an optional lower ring or frame, and the mesh is fixed to the ring(s) or frame(s). Each electrode has a predetermined length based on an electromagnetic field effect that is to be achieved. The electrodes in each group are arranged in parallel by means of electrical connection layout of the mesh wires. Each electrode is made of or comprises one of the following materials: carbon black, graphene, graphite, titanium, conductive polymer and / or other metal with suitable coating. The system further comprises a power supply circuit comprising at least one power supply. The power supply circuit is configured to provide an electromagnetic field which is controlled, regulated and / or varied by controlling, regulating and / or varying current, voltage, pulse length I duration and / or pulse frequency of the power supply circuit, so that under a first pulse length a first group of the groups of electrodes is serving as a cathode and a second group of the groups of the electrodes is serving as an anode, and under the next pulse length the first group of the groups of electrodes is serving as an anode and the second group of the groups of the electrodes is serving as a cathode.

[0039] The predetermined distance between the nodes can be from about 50 cm to about 150 cm.

[0040] The length of each electrode can be from about 5 cm to about 100 cm. The length of each electrode can preferably be from about 10 cm to about 30 cm, and more preferably the length of each electrode can be about 15 cm.

[0041] Each electrode can be formed as a single fiber or strand, or as a bundle of fibers or strands.

[0042] A least a part of the electrode, which is near the node, can be insulated by a sleeve made of electrically non-conducting material.

[0043] The electromagnetic deterrent system is separated from the net cage, wherein at least two helping ropes or wires, attached to the system, are used to get the system placed over at least a lower or bottom part of the net cage. The electromagnetic deterrent system is alternatively configured to be integrated with the net cage.

[0044] The electrodes on the mesh are arranged to be hanging mainly vertically downwards and outside with respect to the net cage, so that the created electromagnetic field will not be directed into the net cage but will be directed outside of the net cage.

[0045] Each of the electrodes is constituted of an electrically conductive carbon fiber filament or an electrically conductive carbon fiber yarn configured as multiple parallel strands into a single electrode.

[0046] Alternatively, each of the electrodes is constituted of a titanium wire configured as multiple parallel strands into a single electrode.

[0047] Alternatively, each of the electrodes is constituted of a platinum coated metal wire configured as multiple parallel strands into a single electrode.

[0048] The pulse voltage, current, shape, duration I length and frequency are set to induce a fright response on one of: approaching shark(s), such as for example of Squalus Atlanticus species, and / or other predator or parasite species.

[0049] Alternatively, the pulse voltage, current, shape, duration I length and frequency are adapted to induce an electro taxis response on one of: approaching shark(s), such as for example of Squalus Atlanticus species, and / or other predator or parasite species.

[0050] Furthermore, the pulse voltage, current, shape, duration I length and frequency are adapted and varied to maintain the effectiveness as a deterrent over time, and countering learning and / or adaptive behavior of sharks and / or other predator or parasite species to the system over time.

[0051] The main features of the present invention are given in the independent patent claims. Additional features of the invention are given in the dependent patent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] These and other aspects of the invention are apparent from and will be further elucidated, by way of example(s), with reference to the drawings, wherein: Fig. 1 shows an electromagnetic deterrent system for a net cage according to the present invention.

[0053] Fig. 2 shows one embodiment of an electromagnetic deterrent system prepared to be placed over at least a lower or bottom part of a net cage.

[0054] Fig. 3 illustrates the electromagnetic deterrent system of fig. 2 being arranged over the lower or bottom part of the net cage.

[0055] Fig. 4 illustrates a part of the electromagnetic deterrent system according to the invention.

[0056] Fig. 5 shows another embodiment of an electromagnetic deterrent system integrated in the net cage.

[0057] Figs. 6A-6C show preparation of a node consisting of an assembly patch with an electrode of the electromagnetic deterrent system integrated in the net of the net cage.

[0058] Figs. 7-12 illustrate different feasible power supply circuits of the electromagnetic deterrent system for a net cage according to the invention.

[0059] Fig. 13 shows another embodiment of the electromagnetic deterrent system according to the invention.

[0060] Fig. 14 shows yet another embodiment of the electromagnetic deterrent system according to the invention.

[0061] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0062] Figure 1 shows, seen from above, one embodiment of an electromagnetic deterrent system 10 configured for a net cage 20 configured for breeding of farmed fish, such as but not limited only to e.g. salmon.

[0063] The electromagnetic deterrent system 10 comprises a mesh 11 , 12 constituted of parallel electrically conductive wires onto which a plurality of electrodes 13 are arranged and connected, each of these electrodes 13 being arranged at a respective node on the mesh 11 , 12 with a distance from each other of the nodes being in a preferable range from about 500 mm (50 cm) to about 1500 mm (150 cm / 1 ,5 m).

[0064] The mesh 11 , 12 of the electromagnetic deterrent system 10 can be made or constituted of vertical 12 and / or horizontal 11 threads or wires. The mesh 11 , 12 of the electromagnetic deterrent system 10 can be arranged to an upper ring or frame 16 or between the upper ring or frame 16 and an optional lower ring or frame 17 and fixed thereto. The frame can be (formed or shaped as) a ring, but it can also have a different shape I form (e.g. square, pentagonal, hexagonal, etc.) depending on the form I shape of the net cage 20. The upper ring or frame 16 is used to connect at least one suitable power supply I power supply unit (PSU) to the electrodes 13 via cables or wires 18, shown on figure 4. The optional lower ring or frame 17 can be used as a (lower or bottom) weight in order to stretch the mesh 11 , 12 of the system 10 and / or to achieve a desired shape of the mesh 11 , 12.

[0065] The length of each electrode 13 can be in a preferred range from about 50 mm (5 cm) to about 1000 mm (100 cm 1 1 m), but shorter or longer lengths are not excluded Optionally and / or additionally, at least a part of the electrode, closest to the fish cage 20 (and being near the node), can be electrically insulated. For example, if we have an electrode 13 having a total length from about 65-70 cm to about 1 m, a certain part of the electrode 13, which is near the node of the mesh 11 , 12 and with a length of about 50 cm, can be electrically insulated with a suitable non-conducting material, e.g. being in the form of a sleeve.

[0066] Preferably the length of each electrode 13 can be from about 10 cm / 100 mm to about 30 cm 1300 mm, and most preferably the length of each electrode 13 can be about 15 cm / 150 mm, but longer electrode length may be used to create more variation in the spatial distribution of the electromagnetic field.

[0067] Each electrode 13 can be formed as a single fiber or strand, or as a bundle of fibers or strands (e.g. like a mare's tail or twisted as a rope). It is commonly known to use metal materials for production of electrodes. Such electrodes will however participate in the electro chemical reactions occurring in the seawater when current is led through a pair of electrodes. With sufficient electrical potential, chloride ions will be released therebetween, and after time chloride ions will recombine so that finally chlorine gas will be released. Most metals are susceptible to corrosion attack of chloride ions in a seawater environment, resulting in the electrodes dissolving after some time (corrosion process of the electrodes). Other ions of the seawater participating in the electrochemical reactions can result in the build-up of scaling / surface layers on the electrodes reducing their effectiveness to generate electromagnetic fields of sufficient strength over time when maintaining the same electrical power input (such as cations like Ca2+and Mg2+, that will form hydroxide and deposit on the cathode, both blocking and corroding the surface).

[0068] In order to reduce and minimize degradation, primarily corrosion and scaling of the electrodes in seawater, each electrode 13 must be made of or comprise one of the following materials: carbon black, graphene, graphite, titanium or conductive polymer. Many materials have been tested but only the above-mentioned materials have proven good or satisfactory anticorrosive results. The electrical resistance and other properties of these materials should also be considered. Other more corrosion prone metals with suitable surface coating can also be considered, such as e.g. platinum, carbon, silicon oxide, conductive polymer, organic coatings or other coatings providing sufficient electrical and anti-corrosion / anti-scaling properties.

[0069] The plurality of electrodes 13 can be arranged in at least two groups of electrodes.

[0070] It is desired to achieve, in seawater, an electromagnetic field with a strength of at least about 8 V / m (preferably about 10 V / m) in order to induce a sufficient deterrence effect against spiny dogfish or grayfish. In order to achieve such results power supply circuits producing high voltage and current are required. At least one power supply (can also be a battery) can be used in the power supply circuit in the electromagnetic deterrent system 10. The system 10 including the power supply circuits is secured against earth faults and voltage variations at several levels. The system 10 can be regulated manually by use of for example but not limited to a touch screen interface and / or automatically by use of for example but not limited to Al (artificial intelligence) and / or a combination of suitable software (e.g. programs or applications) and hardware (e.g. a computer, a cell phone, a microcontroller or even an analog switchgear). The system 10 can be controlled and operated on site or remotely. The power supply circuits are made in such a manner that the electromagnetic field can be controlled, regulated and / or varied. Furthermore, the current, voltage, pulse length or duration (i.e. pulse length = pulse duration) and pulse frequency can be controlled, regulated and / or varied.

[0071] Under each of the pulse lengths I durations one of the group of electrodes 13 is serving as a cathode and the other group of the electrodes 13 is serving as an anode. Then, under a next or subsequent pulse length I duration, the first group of electrodes 13 will be serving as an anode and the other group of the electrodes 13 will be serving as a cathode. This will be repeated. In this manner the electrodes 13 will demonstrate less wear over time and wear in a more evenly.

[0072] In each group of electrodes 13, the electrodes 13 in the mesh 11 , 12 of the system 10 are connected in parallel by a desired coupling manner of the mesh 11 , 12, i.e. the electrodes 13 in each group are arranged in parallel by means of electrical connection layout of the mesh wires 11 , 12.

[0073] Several conducted tests have shown that in order to achieve a desired peak pulse field strength effect of from about 8 V / m to about 15 V / m, preferably about 10 V / m, in the electrodes 13 of the system 10 the power supply to be delivered is dependent on electrode distance and should be about 8 A and 500 W for one meter electrode distance. For multiple electrode pairs, the necessary current is roughly half the current of a single pair multiplied with the actual number of electrode pairs.

[0074] The total number of electrodes 13 in the system 10 can be from 2 to 500 (i.e. from 1 to 250 electrodes 13 in each group of the system 10). And the groups in the system 10 can be from 2 to 250. This is limited by the available instantaneous current for the power supply system. However, other configurations and / or numbers could also be possible. Electromagnetic fields in seawater decay exponentially with radial distance. The electrodes 13 on the mesh 11 , 12 of the system 10 should be arranged in such a manner (e.g. hanging mainly vertically downwards and outside) so that the created electromagnetic field(s) will not be directed into the net cage 20 but will be directed outside of the net cage 20 so that the farmed fish will not be affected by the generated electromagnetic field(s). With such a configuration of the electrodes 13 there will be no noticeable residual electromagnetic field inside the net cage 20. Thus, by having the electrodes hanging outside the net cage 20 with sufficient distance, the resulting field strength inside the net cage 20 becomes negligible.

[0075] According to a first embodiment of the invention shown on figures 2 and 3, the electromagnetic deterrent system 10 can be separated from the net cage 20. The net 21 of the net cage 20 can be arranged to a floatation ring or frame 30 on the water surface 40.

[0076] At least two helping ropes or wires 14, 15 attached to the system 10 (e.g. the upper ring or frame 16 thereof) can be used in order to get the prepared electromagnetic deterrent system 10 (shown on fig. 2) to be placed over at least a lower or bottom part of the net cage 20 (fig. 3). This can be done manually by operator or personnel standing at the water surface 40 or by a remotely operated vehicle (ROV) operated by said personnel or operator.

[0077] Figure 4 shows a part of the electromagnetic deterrent system 10 according to the present invention, where the mesh is constituted of vertical parallel wires 12 connected to the upper ring or frame 16. There can be two groups of electrodes 13, where each group of electrodes 13 is alternating arranged in the circumference of the upper ring or frame 16. The groups of electrodes 13 in the electrical connection layout of the mesh wires 12 are further connected to a suitable power supply circuit by means of conductive wires or cables 18 arranged inside and passing through the upper ring or frame 16. Alternatively, according to a second embodiment of the invention shown on figures 5 and 6A-6C, the electromagnetic deterrent system 10 can be integrated with the net cage 20 without any significant intervention to the construction of the net cage 20.

[0078] This design of the second embodiment is unique in that there is no need to intervene in the construction of the net cage 20. A patch 19 is mended or sewed onto the net (or net wall) 21 of the net cage 20 (fig. 6A). Then the electrodes 13 and the connecting mesh wires 12 of the system 10 are arranged and fixed to the patch 19 by means of a rubber cup 22 in two parts (fig. 6B), a bottom part and a lid part. A sleeve 23 made of non-conducting material can be used to electrically insulate the electrodes 13 and the connecting mesh wires 12 of the system 10 from the net 21 of the net cage 20 (fig. 6C). The coupling protection here consists of said PVC or heavy-duty nylon patch 19 fixed to the net 21 of the net cage 20 by e.g. mending or sewing, wherein said rubber cup 22 is hardened to said patch 19.

[0079] This connection, design and configuration will provide a versatile installation of the system 10 directly at least in the bottom part of the net 21 of the net cage 20. In fig. 5 an alternative construction is shown where the system 10 is integrated in the entire area of the net 21 of the net cage 20.

[0080] In an embodiment, each of the electrodes 13 can be constituted of an electrically conductive carbon fiber filament or an electrically conductive carbon fiber yarn configured as multiple parallel strands into a single electrode. Thus, the active surface area towards the seawater is increased and the electrical surface resistance is reduced.

[0081] In another embodiment, each of the electrodes 13 can be constituted of a titanium wire configured as multiple parallel strands into a single electrode. Thus, the active surface area towards the seawater is increased and the electrical surface resistance is reduced.

[0082] In yet another embodiment, each of the electrodes 13 can be constituted of a platinum coated metal wire configured as multiple parallel strands into a single electrode (or other suitable coating). Thus, the active surface area towards the seawater is increased and the electrical surface resistance is reduced.

[0083] Figures 7-12 illustrate different power supply circuits 50 (power supply and electronics) of the electromagnetic deterrent system 10 for a net cage 20 according to the present invention.

[0084] Figure 7 shows a power supply circuit 50 comprising one power supply unit PSU, four relays R1 , R2, R3, R4 and one capacitor C1 . A cathode (a first electrode from a first group of electrodes 13) is connected to one side of the power supply unit PSU with relays R1 and R3 coupled or arranged in series. An anode (a second electrode from a second group of electrodes 13) is connected to the other side of the power supply unit PSU with relays R2 and R4 coupled or arranged in series. The capacitor C1 is arranged in parallel, as shown on the figure, between the two sides of the power supply unit PSU and after relays R1 and R2 (the directional reference (regarding “after” and / or “before”) starting from the PSU). In a cycle normally all four relays R1 , R2, R3, R4 are in open positions. At first, relays R1 and R2 are closed, keeping relays R3 and R4 open, effectively charging the capacitor C1 with an electric charge. Subsequently, relays R1 and R2 are put in the open positions after which relays R3 and R4 are closed for the duration or length of the desired pulse to achieve the discharge of the capacitor C1 through the now closed circuit containing the capacitor C1 , the electrodes (the cathode and anode) 13 and the seawater. The power supply circuit 50 is then connected to said two groups of electrodes 13, arranged under the water surface 40, by means of conductive wires 11 , 12, 18 that are electrically insulated from other components of the system 10 and the net cage 20. The electromagnetic field is accomplished through the discharge of the capacitively stored electrical energy in the capacitor C1 through the electrodes 13 and the seawater.

[0085] Figure 8 shows another power supply circuit 50 comprising one power supply unit PSU, four relays R1 , R2, R3, R4 and one coil or inductor L1 instead of the capacitor C1 , where all components are arranged in the same manner as on figure 7. This alternative configuration of the circuit 50 in figure 8 uses the inductor L1 , instead of the capacitor C1 , for storage and release of electrical energy. For this circuit 50, the electrical energy is stored in the magnetic field of the induction coil L1 by closing relays R1 and R2 while relays R3 and R4 are open, and subsequently the stored electrical energy is released when relays R3 and R4 are closed simultaneously.

[0086] Figure 9 illustrates yet another power supply circuit 50 comprising one power supply unit PSU, four relays R1 , R2, R3, R4, one capacitor C1 and one coil or inductor L1 . The topography of the circuit 50 is the same as the one shown on figure 7, wherein one coil L1 is arranged just before the fourth relay R4 (i.e. after the second relay R2 and one side of the capacitor C1 ), where the directional reference (regarding “before” and / or “after”) is starting from the PSU. In this case, electrical energy is both stored and released capacitively and inductively. The use of an inductive circuit allows for higher energy densities of the stored energy and the possibility of achieving higher field strengths.

[0087] One of the advantages of using a circuit 50 with capacitive and / or inductive energy storage allows for lower power rating of the PSU.

[0088] Figure 10 illustrates yet another power supply circuit 50 comprising one power supply unit PSU, one output transformer T1 and two relays R3, R4 arranged between the transformer T1 and the electrodes 13, where coil side A of the transformer T1 is connected to the PSU and coil side B of the transformer T1 is connected to said two relays R3, R4. The transformer comprises also a core C around which the coils A and B are wound. In this case relays R3 and R4 are from normally open position closed for the duration or length of the pulse, with the transformer T1 changing the voltage and current from the PSU to the electrodes 13 to achieve higher field strengths. The electrical field strength in seawater is a strong function of the electric current and the output transformer T1 can be used to increase the current amplitude of the pulse to the electrodes 13.

[0089] Figure 11 illustrates a different feasible power supply circuit 50 comprising one power supply unit PSU, four relays R1 , R2, R3, R4, one capacitor C1 , one coil or inductor L1 and one transformer T2. This circuit 50 combines all the elements of figures 9 and 10 allowing for capacitive and inductive energy storage / discharge and transforming voltage and current amplitude of the pulse to the electrodes 13.

[0090] Figure 12 illustrates a circuit configuration 50 where alternatingly one of the electrodes 13, E1 , E2 is connected by relay R4, to an electrical potential lying between the positive and negative output (intermediate level) of two PSUs, P1 and P2, which are connected in series, while relays R3 and R5 connect the other one of the electrodes 13, E1 , E2 to both the other positive and negative sides of the power supplies P1 , P2. Thus, relays R3, R4 and R5 (which can be switching relays) are used to alternatingly connect the electrodes E1 and E2 to the intermediate voltage level of the serial connected PSUs, P1 , P2, and the other positive / negative terminals or sides of the power supplies, P1 , P2. Relays R1 and R2 (which can be solid state relays) regulate the generation of the pulse and are normally in open position. The relays R1 and R2 are alternatingly closed for the desired duration or length of the pulse, sending alternatingly a pulse with a voltage amplitude, corresponding to the positive terminal and the negative terminal, to alternatingly electrode E1 and E2. This has the advantage that chloride formation at the electrodes 13, E1 , E2 is periodically reversed and positive effects on electrode wear can be achieved. A further improvement of this can be to have an extra relay (not shown) between relay R4 and the power supplies P1 , P2, being closed only during a pulse (synchronized with relay(s) R1 I R2). An example of a possible resulting pulse sequence at the electrodes 13, E1 , E2 is shown in the voltage amplitude / time diagram. This configuration together with using a microcontroller to time the opening and closing of the relays R1 and R2 and the switching relays R3, R4, R5. This provides the needed flexibility to design appropriate pulse sequences for optimizing functionality, energy consumption and / or electrode live. It is one specific intention to vary pulse sequences and to randomize pulse intervals to counter learning and / or accommodation of sharks to the system 10. In this example relays R3, R4, R5 are first switched in one direction coupling electrode E1 to the positive / negative terminals of the serial connected power supplies P1 , P2 and electrode E2 to the intermediate level terminal or side. At first a pulse is generated towards the voltage on the positive side of the power supplies P1 , P2 by closing electrode E1 for the duration of the pulse while keeping electrode E2 open. Then electrode E1 is opened while electrode E2 is closed for the duration of the pulse in the direction of voltage of the negative side of the power supplies P1 , P2. Then relays R3, R4, R5 are switched in the other position and the same cycle with opening / closing electrodes E1 and E2 are repeated, effecting a positive and negative pulse on the other electrode (E2 and E1 ) respectively.

[0091] Figure 13 illustrates (seen “from above”) another embodiment of the electromagnetic deterrent system 10 according to the present invention.

[0092] Here it is shown that the electromagnetic deterrent system 10 can protect an aquaculture installation with several net cages 20 having for example floatation rings 30. In this example there can be four net cages 20.

[0093] The electromagnetic deterrent system 10 is arranged on two sides along the farming facility with the four net cages 20 in order to protect against marine biological threats that come drifting with the current 60, such as for example the tide. The two sides of the electromagnetic deterrent system 10 are perpendicular to the direction of the current 60. At most farming locations the tidal current 60 mainly comes in and out the aquaculture installation in two directions. The two arrows 60 in the drawing illustrate the direction of the current. As evident from the drawing in some cases it will not be necessary for the system 10 to surround the entire aquaculture installation with said at least one net cage 20. On the drawing some mooring(s), pontoon(s), ropes, (electrical) couplings and / or cables I wires, and / or other components of the system 10 and / or the aquaculture installation can also be seen.

[0094] Figure 14 illustrates yet another embodiment of the system 10 according to the invention, where each electrode 13 in the system 10 can be supplied with a microcircuit card I board 55. Each circuit board I card 55 can be encapsulated and / or watertight.

[0095] The drawing shows the system 10 according to the invention and configured for generating electric and electromagnetic fields in the marine environment. The system comprises a main cable that distributes power from a power supply 50 to several secondary vertical (in this embodiment) cables / wires 12 placed at regular intervals. Each secondary cable 12 is equipped with a set of electrodes 13, where each electrode 13 has an integrated microcircuit board 55 for power management.

[0096] The system 10 operates by sending short electrical pulses in a sequential anodecathode configuration. The pulse length on each electrode 13 is very short, and the sequence is programmed so that only a limited number of electrodes 13 are active at the same time. This creates an electric / electromagnetic field over the area with minimal energy consumption, made possible by the integrated power management mechanism in each microcircuit board 55. Here the energy consumption is even less than in the previous embodiments.

[0097] The system 10 consists of an X meter main cable that supplies Y number of connected secondary vertical cables 12, each with a length of Z meters. On each secondary cable 12, N number of electrodes 13 are mounted, placed at regular intervals along the length of the cable 12.

[0098] At the connection point with the cable 12 each electrode 13 is equipped with an integrated microcircuit board 55 that controls the power supply to the electrode 13. The microcircuit board 55 enables sequential activation of the electrodes 13 with very short power pulses.

[0099] The electrodes 13 send pulses with a duration of M milliseconds. The pulses are programmed to be generated in an anode-cathode sequence to create a dynamic and nearly constant electric / electromagnetic field in the saltwater.

[0100] Through programming, the electrodes 12 are activated in a specific order as previously explained. This ensures that only a limited number of electrodes 13 are active at the same time, resulting in significant energy savings.

[0101] The microcircuit boards 55 on each electrode 13 function as switches to turn the power on and off quickly, optimizing the energy consumption and reducing the demands on the power supply and electronics 50 of the system 10. The result is a nearly continuous electric / electromagnetic field over the entire area despite the sequential activation. This field can be adjusted based on the system's programmed sequence and the need for energy savings. Some additional advantages in addition to the previous advantages of the previous embodiments can be that the power consumption can be reduced by minimizing the number of active electrodes 13 at any given time, and thus the load on the main power supply and electronics 50 will be reduced. And finally, the sequence can be dynamically adjusted on order to achieve optimal effect in different applications of the system 10.

[0102] Additional modifications, alterations and adaptations of the present invention will suggest themselves to those skilled in the art without departing from the scope of the invention as defined in the following patent claims.

Claims

C L A I M S1 . An electromagnetic deterrent system (10) configured for at least one net cage (20) configured for breeding of farmed fish, the system (10) comprising a mesh (11 ,12) of vertical (12) and / or horizontal (11 ) wires on which at least two groups of electrodes (13) are arranged at respective nodes on the mesh (11 , 12), the nodes being arranged with a predetermined distance from each other, wherein the mesh (11 , 12) of the electromagnetic deterrent system (10) is arranged to an upper ring or frame (16) or between the upper ring or frame (16) and an optional lower ring or frame (17), and the mesh (11 , 12) is further fixed to the ring(s) or frame(s) (16, 17), wherein each electrode (13) has a predetermined length based on an electromagnetic field effect that is to be achieved, and wherein the electrodes (13) in each group are arranged in parallel by means of electrical connection layout of the mesh wires (11 , 12), and wherein each electrode (13) is made of or comprises one of the following materials: carbon black, graphene, graphite, titanium, conductive polymer and / or other metal with a suitable coating, and wherein the system (10) further comprises a power supply circuit (50) comprising at least one power supply (PSU, P1 , P2), the power supply circuit (50) being configured to provide an electromagnetic field which is controlled, regulated and / or varied by controlling, regulating and / or varying current, voltage, pulse length I duration and / or pulse frequency of the power supply circuit (50) so that under a first pulse length a first group of the groups of electrodes (13) is serving as a cathode and a second group of the groups of the electrodes (13) is serving as an anode, and under the next pulse length the first group of the groups of electrodes (13) is serving as an anode and the second group of the groups of the electrodes (13) is serving as a cathode.

2. The electromagnetic deterrent system (10) according to claim 1 , wherein the predetermined distance between the nodes is from about 50 cm to about 150 cm.

3. The electromagnetic deterrent system (10) according to claim 1 or claim 2, wherein the length of each electrode (13) is from about 5 cm to about 100 cm.

4. The electromagnetic deterrent system (10) according to any one of claims 1 -3, wherein the length of each electrode (13) is from about 10 cm to about 30 cm, and preferably the length of each electrode (13) is about 15 cm.

5. The electromagnetic deterrent system (10) according to any one of claims 1 -4, wherein each electrode (13) is formed as a single fiber or strand, or as a bundle of fibers or strands.

6. The electromagnetic deterrent system (10) according to any one of claims 1 -5, wherein at least a part of the electrode which is near the node is insulated by a sleeve made of electrically non-conducting material.

7. The electromagnetic deterrent system (10) according to any one of claims 1 -6, wherein the system (10) is separated from the net cage (20), wherein at least two helping ropes or wires (14, 15) attached to the system (10) are used to get the system (10) placed over at least a lower or bottom part of the net cage (20).

8. The electromagnetic deterrent system (10) according to any one of claims 1 -7, wherein the system (10) is configured to be integrated with the net cage (20).

9. The electromagnetic deterrent system (10) according to any one of claims 1 -8, wherein the electrodes (13) on the mesh (11 , 12) are arranged to be hanging mainly vertically downwards and outside with respect to the net cage (20) so that the created electromagnetic field will not be directed into the net cage (20) but will be directed outside of the net cage (20).

10. The electromagnetic deterrent system (10) according to any one of claims 1 -9, wherein each of the electrodes (13) is constituted of an electrically conductive carbon fiber filament or an electrically conductive carbon fiber yarn configured as multiple parallel strands into a single electrode.11 . The electromagnetic deterrent system (10) according to any one of claims 1 -9, wherein each of the electrodes (13) is constituted of a titanium wire configured as multiple parallel strands into a single electrode.

12. The electromagnetic deterrent system (10) according to any one of claims 1 -9, wherein each of the electrodes (13) is constituted of a platinum coated metal wire configured as multiple parallel strands into a single electrode.

13. The electromagnetic deterrent system (10) according to any one of claims 1- 12, wherein pulse voltage, current, shape, duration and frequency are set to induce a fright response on one of: approaching shark(s), such as for example of Squalus Atlanticus species, and / or other predator species.

14. The electromagnetic deterrent system (10) according to any one of claims 1- 12, wherein pulse voltage, current, shape, duration and frequency are adapted to induce an electro taxis response on one of: approaching shark(s), such as for example of Squalus Atlanticus species, and / or other predator species.

15. The electromagnetic deterrent system (10) according to any one of claims 1- 12, wherein pulse voltage, current, shape, duration and frequency are adapted and varied to maintain the effectiveness as a deterrent over time, and countering learning and / or adaptive behavior of sharks to the system (10) over time.

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