System and method for trawling with a boat by using one or more steerable underwater drones

Abstract

The method comprises: - providing at sea (12) a boat (6) having a trawl net (8), a control unit (14) and at least one underwater drone (4) that is steerable by using the control unit (14), - bringing the trawl net (8) under the surface of the sea (12) by using the least one underwater drone (4), - controlling the position and velocity of the at least one underwater drone (4) while the at least one underwater drone (4) is connected to the trawl net (8). A system for carrying out the method is also configured.

Description

[0001] System and Method for Trawling with a Boat by using one or more Steerable Underwater Drones

[0002] Field of invention

[0003] The present invention relates to a method for trawling with a boat, having a trawl net, a control unit and at least one underwater drone that is steerable by using the control unit. The invention also relates to a system for carrying out the method.

[0004] Prior art

[0005] The concept of using steerable underwater drones to assist in trawling with a boat has been described in the prior art. This approach aims to improve control, efficiency, and precision in fishing operations. There exist several prior art methods that involve using underwater drones for trawling.

[0006] Traditional trawling nets, when towed behind boats, can be difficult to control and position precisely, especially in complex underwater terrains. This often results in missed catches or unintended impact on the seafloor. Accordingly, underwater drones are deployed to control the depth, orientation, and spread of the trawling nets. By attaching steerable drones to different parts of the net, operators can fine-tune its position, optimizing the net's performance and reducing environmental impact. Real-time adjustments allow for better targeting of specific fish schools and avoid damaging sensitive seafloor habitats.

[0007] During traditional trawling, the time used to empty the trawl net(s) is significant since the trawl net(s) must be emptied onboard. Accordingly, when a boat needs to collect several catches from the trawl net, the trawl net needs to be pulled up for being emptied and be inserted into the sea again to hereafter be pulled up for being emptied again. This procedure is time consuming and affects the quality of the catch.Trawling systems in which a trawl net is manoeuvred or positioned by means of underwater propulsion units are known. For example, WO2017222390A1 describes the use of underwater drones or powered pods attached to a trawl net to control the position and movement of the net relative to a fishing vessel. Such known systems allow the trawl net to be guided laterally or longitudinally during fishing operations, and some systems further disclose transferring a catch from the trawl net to the vessel using pumping arrangements.

[0008] However, WO2017222390A1 does not disclose a method in which the trawl net is first brought to a position behind the vessel and then moved to a second position in front of or beside the vessel by means of underwater drones for the purpose of pumping the catch onboard through a hose connected to the net. Moreover, the prior art does not teach attaching a rear end line to the hose and bringing the hose onboard the vessel by towing this rear end line.

[0009] GB695641A discloses a fish-catching device in which a trawl net is provided with a ring that must be attached to a frame positioned below the water surface and forming an integral part of the mother ship's structure. In order to enable transfer of the catch, the net must be hauled all the way to the ship, after which the ring is engaged with the frame so that the fish can be pumped into the vessel. This procedure, however, is associated with significant disadvantages. It is both timeconsuming and energy-intensive to haul a heavy, filled trawl net all the way to the mother ship before the fish can be transferred. Accordingly, there is a need for an improved solution which enables a faster transfer of the catch into the vessel and, at the same time, reduces the overall energy consumption compared with the technique disclosed in GB695641A.

[0010] It is an object to provide a method and system that is faster than theprior art solutions.

[0011] It is an object to provide a method that makes it faster to move fish from the trawl net on board the boat.

[0012] It is a further object to provide a method that increases catch efficiency.

[0013] Summary of the invention

[0014] The object of the present invention can be achieved by a method as defined in claim 1 and a system as defined in claim 8. Preferred embodiments are defined in the dependent subclaims, explained in the following description and illustrated in the accompanying drawings.

[0015] The method according to the invention is a method for trawling with a boat, said method comprising:

[0016] - providing at sea a boat having a trawl net, a control unit and at least one underwater drone that is steerable by using the control unit,

[0017] - bringing the trawl net under the surface of the sea by using the least one underwater drone,

[0018] - controlling the position and velocity of the at least one underwater drone while the at least one underwater drone is connected to the trawl net,

[0019] wherein the method comprising:

[0020] - bringing the trawl net to a first position behind the boat by using the least one underwater drone,

[0021] - hereafter bringing the trawl net to a second position in front of or next to the boat by using the least one underwater drone,

[0022] - in the second position pumping, by using a pump a catch caught by using the trawl net on board the boat by using a hose that is connected to the trawl net,

[0023] wherein a rear end line is attached to the hose,wherein the method comprising bringing the hose on board the boat (6) by towing the rear end line.

[0024] Hereby, it is possible to provide a method that is faster than the prior art solutions. The method makes it faster to move fish from the trawl net on board the boat. Moreover, the method can increase the catch efficiency.

[0025] The method comprising:

[0026] - providing at sea a boat having a trawl net, a control unit and at least one underwater drone that is steerable by using the control unit.

[0027] In an embodiment, the boat has a single a trawl net. In an embodiment, the boat has several trawl nets.

[0028] The method comprising:

[0029] - bringing the trawl net(s) under the surface of the sea by using the least one underwater drone,

[0030] - controlling the position and velocity of the at least one underwater drone while the at least one underwater drone is connected to the trawl net.

[0031] In an embodiment, the method comprising:

[0032] - bringing the trawl net(s) under the surface of the sea by using a single one underwater drone,

[0033] - controlling the position and velocity of the underwater drone while the at least one underwater drone is connected to the trawl net.

[0034] In an embodiment, the method comprising:

[0035] - bringing the trawl net(s) under the surface of the sea by using two underwater drones,

[0036] - controlling the position and velocity of the underwater drones whilethe two underwater drones are connected to the trawl net.

[0037] In an embodiment, the method comprising:

[0038] - bringing the trawl net(s) under the surface of the sea by using two or more underwater drones,

[0039] - controlling the position and velocity of the underwater drones while the two or more underwater drone are connected to the trawl net.

[0040] The method comprising:

[0041] - bringing the trawl net(s) to a first position behind the boat by using the least one underwater drone,

[0042] - hereafter bringing the trawl net to a second position in front of or next to the boat by using the least one underwater drone,

[0043] - in the second position pumping, by using a pump a catch caught by using the trawl net on board the boat by using a hose that is connected to the trawl net.

[0044] In an embodiment, the hose is attached to the trawl net. In an embodiment, the hose is integrated into the trawl net.

[0045] In an embodiment, the hose is attached to or integrated into a bag of the trawl net.

[0046] In an embodiment, the hose is attached to a rear portion of the trawl net.

[0047] In an embodiment, the method comprising:

[0048] - bringing the hose on board the boat by towing a rear end line (a wire) that is attached to the hose.

[0049] In an embodiment, the rear end line (the wire) is attached to a distalend of the hose.

[0050] In an embodiment, the method comprising:

[0051] - by using the least one underwater drone that is connected to the trawl net by a towing wire, providing and maintaining a towing force F large enough to prevent generations of knots in the towing wire(s).

[0052] In an embodiment, the method comprising:

[0053] - in the second position, by using the least one underwater drone securing that a rear portion of the trawl net is maintained in a position no longer than 1000 m from the boat.

[0054] In an embodiment, the method comprising:

[0055] - in the second position, by using the least one underwater drone securing that a rear portion of the trawl net is maintained in a position no longer than 500 m from the boat.

[0056] In an embodiment, the method comprising:

[0057] - in the second position, by using the least one underwater drone securing that a rear portion of the trawl net is maintained in a position no longer than 300 m from the boat.

[0058] In an embodiment, the method comprising:

[0059] - in the second position, by using the least one underwater drone securing that a rear portion of the trawl net is maintained in a position no longer than 200 m from the boat.

[0060] In an embodiment, the method comprising:

[0061] - in the second position, by using the least one underwater drone securing that a rear portion of the trawl net is maintained in a position no longer than 100 m from the boat.In an embodiment, the method comprising:

[0062] - in the second position, by using the least one underwater drone securing that a rear portion of the trawl net is maintained in a position no longer than 50 m from the boat.

[0063] In an embodiment, the method comprising using two underwater drones for each trawl net, wherein each underwater drone is steerable by using the control unit. In an embodiment, the underwater drones are identical.

[0064] In an embodiment, the method comprising:

[0065] - using a first and a second trawl net to trawl with the boat;

[0066] - bringing each of the trawl nets to a first position behind the boat by using the least one underwater drone,

[0067] - hereafter bringing the first trawl net to a second position in front and at the left side of the boat by using two underwater drones and bringing the second trawl net to a second position in front and at the right side of the boat by using two underwater drones,

[0068] - in the second positions pumping, by using a first pump a catch caught by using the first trawl net on board the boat by using a first hose and by using a second pump a catch caught by using the second trawl net on board the boat by using a second hose.

[0069] The pump may be a fish pumps to efficiently transfer fish from nets to the boat.

[0070] The pump may be a centrifugal pump. A centrifugal pump creates suction to move water and fish without causing significant damage. A centrifugal pump may be used in combination with a dewatering system.

[0071] The pump may be a vacuum pump configured to create a vacuum tosuck water and fish onboard. Vacuum pumps are considered to be gentle on fish, making them ideal for high-value catches.

[0072] The pump may be a hydraulic pump operated via hydraulic power. A hydraulic pump is typically used for pumping water mixed with fish, particularly in larger operations.

[0073] The pump may be a peristaltic pump. Peristaltic pumps use a rotating mechanism to move fish and water. Peristaltic pumps are gentle and minimize fish stress or damage.

[0074] In an embodiment, the pump is an ejector.

[0075] The pump may be a submersible pump. A submersible pump is configured to be placed in the water and directly lift fish onboard. Submersible pumps are robust and reliable for continuous use.

[0076] The type of pump is typically chosen based on factors like fish species, boat size, and processing requirements.

[0077] In an embodiment, the method comprising:

[0078] - providing at least one of the at least one underwater drone with an echo sonar with an echo sonar field arranged and configured to communicate with the control unit by using a communication module (on the boat via a cable), said communication module being configured to send information to the control unit,

[0079] - detecting information including the position of the one or more underwater drones by using the one or more underwater drones and - sending the detecting information to the boat and

[0080] - by using the control unit steering the at least one underwater drone in dependency of the detecting information.The system according to the invention is a system configured to carry out the method according to the invention, the system comprising:

[0081] -a boat,

[0082] - at least one trawl net,

[0083] - a control unit,

[0084] - at least one underwater drone that is steerable by using the control unit,

[0085] wherein the system is configured to:

[0086] - bring the at least one trawl net under the surface of the sea by using the least one underwater drone,

[0087] - control the position and velocity of the at least one underwater drone while the at least one underwater drone is connected to the trawl net. wherein the system is configured to:

[0088] - bring the at least one trawl net to a first position behind the boat by using the least one underwater drone,

[0089] - hereafter bringing the trawl net to a second position in front of or next to the boat by using the least one underwater drone,

[0090] - in the second position pumping, by using a pump a catch caught by using the trawl net on board the boat by using a hose that is connected to the trawl net,

[0091] wherein a rear end line is attached to the hose,

[0092] wherein the system is configured to bring the hose on board the boat by towing the rear end line.

[0093] Hereby, it is possible to provide a system that is faster than the prior art solutions. The system makes it faster to move fish from the trawl net on board the boat. Moreover, the system can increase the catch efficiency.

[0094] In an embodiment, the control unit is arranged onboard. The control unit may be placed in a cabin or at another location providing safe conditions for the control unit.The hose is arranged and configured to guide the catch from the net to the boat.

[0095] In an embodiment, the hose is attached to the trawl net.

[0096] In an embodiment, the hose is attached to a rear portion of the trawl net.

[0097] In an embodiment, the at least one underwater drone comprises an echo sonar with an echo sonar field arranged and configured to communicate with the control unit by using a communication module, said communication module being configured to send information to the control unit,

[0098] wherein the system is configured to:

[0099] detect information including the position of the one or more underwater drones by using the one or more underwater drones and

[0100] - send the detecting information to the boat and

[0101] - by using the control unit steer the at least one underwater drone in dependency of the detecting information.

[0102] In an embodiment, the boat comprises an echo sonar with an echo sonar field, wherein the echo sonar is arranged and configured to detect a position of the at least one underwater drone relative to the boat.

[0103] In an embodiment, the system comprises one or more surface drones arranged and configured to indicate the position of the trawl net. In an embodiment, at least one surface drone is equipped with a digital positional awareness system (e.g. Automatic Identification System, AIS).

[0104] In an embodiment, the at least one underwater drone is powered via acable.

[0105] In an embodiment, the at least one underwater drone is powered via a battery.

[0106] In an embodiment, the at least one underwater drone is powered via a hydraulic hose.

[0107] Each underwater drone may be designed to monitor and / or optimize and / or assist in controlling fishing activities. Hereby the underwater drone(s) can help fishermen increase their catch efficiency, reduce bycatch, and lower fuel consumption. In an embodiment, the underwater drone(s) are configured to provide real-time visual and / or sensor feedback on net conditions and / or fish behaviour.

[0108] In an embodiment, the underwater drone(s) are built to withstand underwater pressure and minimize drag, allowing it to move easily with or against currents. This may be achieved by suing durable materials including high-strength materials like aluminium, stainless steel, or reinforced plastics to withstand deep-sea conditions, corrosion, and impact with trawl nets or debris.

[0109] In an embodiment, the underwater drone(s) are equipped with a propulsion system. In an embodiment, the underwater drone(s) are equipped with multiple thrusters (usually three or more) for manoeuvring in different directions, helping the drone position itself around the trawl net as needed.

[0110] In an embodiment, the underwater drone(s) are equipped with variable speed control equipment configured to allows the underwater drone(s) to follow the trawl net at varying speeds and to stay positioned relative to moving trawls or shoals of fish.In an embodiment, the underwater drone(s) are equipped with a depth control unit designed to help maintaining a constant depth, particularly useful if the trawl net is moving at a specific depth layer.

[0111] In an embodiment, the underwater drone(s) are equipped with a power system comprising a battery pack including rechargeable, high-capacity batteries to sustain periods (preferably one or more hours) of continuous underwater operation. In an embodiment, the batteries are designed to handle cold temperatures underwater.

[0112] In an embodiment, the underwater drone(s) are electrically powered through an electrical power connection electrically connected to a power supply of the boat.

[0113] In an embodiment, the underwater drone(s) are tethered to the boat for continuous power and data transfer.

[0114] In an embodiment, the underwater drone(s) are equipped with one or more onboard batteries for untethered operations.

[0115] In an embodiment, the underwater drone(s) are equipped with one or more camera. In an embodiment, the underwater drone(s) are equipped with one or more high-resolution cameras suitable for realtime visual monitoring. This enables fishermen to see fish behaviour and trawl net conditions.

[0116] In an embodiment, the underwater drone(s) are equipped with one or more low-light or infrared cameras configured to be used for deeper waters where sunlight is minimal. Hereby, the camera(s) allow for better visibility of fish and trawl net surroundings.In an embodiment, the underwater drone(s) are equipped with one or more camera having a 360-degree view or pan / tilt functionality. Hereby, it is possible to provide a comprehensive monitoring of the trawl net and surrounding fish schools.

[0117] In an embodiment, the method comprising providing at least one underwater drone with an echo sonar with an echo sonar field arranged and configured to communicate with the control unit by using a communication module, said communication module being configured to send information to the control unit.

[0118] In an embodiment, the method comprising providing each of the at least one underwater drone with an echo sonar with an echo sonar field arranged and configured to communicate with the control unit by using a communication module, said communication module being configured to send information to the control unit.

[0119] In an embodiment, the echo sonar with an echo sonar field is a sonar system that includes both forward-looking and downward-facing sonar configured to detect fish schools and monitor trawl net positioning relative to the seabed and / or the boat.

[0120] In an embodiment, the underwater drone(s) are equipped with one or more depth sensors configured to detect the depth of the underwater drone(s).

[0121] In an embodiment, the underwater drone(s) are equipped with one or more pressure sensors configured to detect the pressure. The pressure may be used to determine the depth of the underwater drone(s).

[0122] Using depth sensors and / or pressure sensors enables the underwater drone(s) to maintain specific depths and withstand pressure in deepwater.

[0123] In an embodiment, the underwater drone(s) are equipped with one or more sensors arranged and configured to measures water parameters including one or more of the following: temperature, salinity, oxygen levels, and currents. These water parameters can influence fish behaviour and net effectiveness.

[0124] In an embodiment, the communication module is a real-time data link.

[0125] In an embodiment, the underwater drone(s) are tethered underwater drone(s) equipped with fiber optics or specialized cables for high-speed data transfer, wherein the communication module is configured to provide real-time visuals and / or sensor data to the control unit.

[0126] In an embodiment, the underwater drone(s) are tethered underwater drone(s) equipped with a wireless (e.g. acoustic) communication unit. Untethered underwater drones might use acoustic modems to transmit data, though this is generally slower and may not support real-time video at great depths.

[0127] In an embodiment, the underwater drone(s) are equipped with a control and navigation system. In an embodiment, the control and navigation system is an autonomous navigation system that includes a preprogrammed path or adaptive tracking that allows the underwater drone to stay near the trawl net or return to the surface.

[0128] In an embodiment, the underwater drone(s) are equipped with a remote controller that allow operators on the boat to control the underwater drone's position and functions manually.

[0129] In an embodiment, the underwater drone(s) are equipped with amodule that applies Artificial Intelligence to recognize fish species and / or track fish schools and / or adjust positioning of the underwater drone(s) based on fish behaviour.

[0130] The underwater drone may be connected to the trawl net by using any structure suitable for connecting the underwater drone to the trawl net.

[0131] In an embodiment, the underwater drone is be connected to the trawl net by using a rope.

[0132] In an embodiment, the underwater drone is be connected to the trawl net by using a cord.

[0133] In an embodiment, the underwater drone is be connected to the trawl net by using a cable.

[0134] In an embodiment, the underwater drone is be connected to the trawl net by using a chain.

[0135] In an embodiment, one or more of the underwater drones are equipped with one or more cameras. The one or more cameras can be used to identify to and assess water conditions and / or map the seafloor before or during trawling. Accordingly, the underwater drones can navigate complex areas and provide real-time data to the trawler crew, guiding the boat along the most productive paths while avoiding obstacles. Using mapping underwater drones enable fishermen to avoid areas where trawling could damage equipment or harm the environment. This leads to improved resource targeting and minimizes time wasted on non-viable areas.

[0136] In an embodiment, the underwater drone is connected to the boat by at least one guiding line.In an embodiment, the method comprising using two or more underwater drones.

[0137] In an embodiment, the method comprising using three or more underwater drones.

[0138] In an embodiment, the method comprising using four or more underwater drones.

[0139] In one embodiment, the boat comprises an echo sonar with an echo sonar field, wherein the echo sonar is arranged and configured to detect a position of the at least one underwater drone relative to the boat. In this embodiment, the method comprises the step of detect a position of the at least one underwater drone relative to the boat by using the echo sonar of the boat.

[0140] In one embodiment, at least one of the at least one underwater drone is equipped with a digital positional awareness system.

[0141] In one embodiment, at least one of the at least one surfce drone is equipped with a radar reflector.

[0142] In an embodiment, the digital positional awareness system is the so-called AIS (Automatic Identification System). The AIS is the mariner's most significant development in navigation safety since the introduction of radar. This is a digital positional awareness system operating in the very high frequency maritime band. Its purpose is to help identify ships, assist in target tracking, assist in search and rescue operation, simplify information exchange and provide additional information to assist situational awareness.In an embodiment, the method comprising applying one or more underwater drone that is powered via a cable that is connected to the boat.

[0143] In an embodiment, the method comprising applying one or more underwater drone that is powered via one or more batteries.

[0144] In an embodiment, the method comprising applying one or more underwater drone that is powered via a hydraulic hose that is connected to the boat.

[0145] In an embodiment, the method comprising:

[0146] - applying the at least one underwater drone to pull the trawl net to a position behind the boat while using an echo sonar of the boat to assist during fishing.

[0147] In an embodiment, the method comprising:

[0148] - after emptying the trawl net, bringing the trawl net into a position behind the boat.

[0149] In an embodiment, the method comprising:

[0150] - detecting positions in which fish are present by using the echo sonar, - positioning the trawl net in an area where fish are detected by the echo sonar.

[0151] Hereby, the method increases catch efficiency by positioning the net in areas where fish are detected.

[0152] Description of the Drawings

[0153] The invention will become more fully understood from the detailed description given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative of thepresent invention. In the accompanying drawings:

[0154] Fig. 1A shows a side view of a system comprising a boat and a trawl net being moved by using one or more steerable underwater drones;

[0155] Fig. IB shows a top view of the system shown in Fig. 1A;

[0156] Fig. 1C shows a side view of the system shown in Fig. 1A in a situation, in which the trawl net is being moved forward relative to the boat by using the one or more steerable underwater drones;

[0157] Fig. 2A shows a top view of the system shown in Fig. 1C;

[0158] Fig. 2B shows a side view of the system shown in Fig. 2A, in a situation, in which the trawl net has been moved in front of the boat and close to the surface by using the one or more steerable underwater drones;

[0159] Fig. 2C shows a top view of a system that is almost in the same configuration as shown in Fig. 2B;

[0160] Fig. 3A shows a side view of a system, in a situation, in which the trawl net has been moved in front of the boat and close to the surface by using the one or more steerable underwater drones, wherein two surface drones are used to indicate the position of the trawl net;

[0161] Fig. 3B shows a top view of the boat shown in Fig. 3A;

[0162] Fig. 4A shows a side view of a system, in a situation, in which the trawl net has been moved in front of the boat and close to the surface by using the one or more steerable underwater drones, wherein a single surface drone is used to indicate the position of the trawl;

[0163] Fig. 4B shows a top view of the system shown in Fig. 4A;

[0164] Fig. 5A shows a side view of a system according to the invention; Fig. 5B shows a top view of the system shown in Fig. 5A;

[0165] Fig. 6 shows a side view of a boat pumping the catch from a trawlnet on board the boat.

[0166] Detailed description of the invention

[0167] Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, a system 2 of the present invention is illustrated in Fig. 1A.

[0168] Fig. 1A illustrates a side view of a system 2 comprising a boat 6 and a trawl net 8 being moved by using one or more steerable underwater drones 4. Each of the one or more drones 4 is connected to the boat 6 by a guiding line 10. In an embodiment, the guiding line 10 is a wire. The wire may be a metal wire. In an embodiment, the wire is a steel wire. A hose 9 is connected to the rear end of the trawl net 8. A rear end line 11 is attached to the hose 9. The rear end line 11 will typically be attached to the distal end of the hose 9. The rear end line 11 is arranged and configured to enable that the hose 9 can be pulled on board of the boat 6. The boat typically comprises a winch or winding gear configured for puling or lifting heavy loads, making it ideal for bringing objects on board the boat 6. Such winch or winding gear can be used for pulling the hose 9 on board the boat 6. The winch or winding gear can be manually operated with a crank or powered by an electric or hydraulic motor.

[0169] The boat 6 is provided at sea 12. The boat 6 has a trawl net 8 that has been brought under the surface of the sea 12 by using the least one underwater drone 4.

[0170] A control unit 14 is provided at the boat 6 and the at least one underwater drone 4 is steerable by using the control unit 14. Accordingly, the speed and travelling direction of the at least one underwater drone 4 can be controlled by using the control unit 14.The system 2 is configured to control the position and velocity of the at least one underwater drone 4 while the at least one underwater drone 4 is connected to the trawl net 8. Each underwater drone 4 will typically be connected to the trawl net 8 by using a towing wire 15. The towing wire 15 is typically made of steel. However, other materials may be applicable.

[0171] By using the least one underwater drone 4 that is connected to the trawl net 8 by the towing wire 15 it is possible to provide and maintain a towing force F large enough to prevent generations of knots in the towing wire 15.

[0172] The trawl net 8 has been brought into a first position behind the boat 6 by using the least one underwater drone 4. In an embodiment, at the rear end of the trawl net 8, the rear end line 11 extends in extension of the hose 9.

[0173] Fig. IB illustrates a top view of the system shown in Fig. 1A. It can be seen that the trawl net 8 is being towed by a first underwater drone 4 and by a second underwater drone 4. Each underwater drone 4 is attached to a towing wire 15 fixed to or integrated into the trawl net 8. Each underwater drone 4 provides a towing force F large enough to prevent generations of knots in the towing wires 15. At the rear end of the trawl net 8, a rear end line 11 is fixed to the hose 9.

[0174] Each of the one or more drones 4 is connected to the boat 6 by a guiding line 10. In Fig. IB, the boat 6 and the underwater drones 4 are moved in the same direction.

[0175] Fig. 1C illustrates a side view of the system shown in Fig. 1A in a situation, in which the trawl net 8 is being moved forward relative to the boat 6 by using steerable underwater drones 4. A control unit 14 is provided at the boat 6 and the underwater drones 4 are steerable byusing the control unit 14.

[0176] At the rear end of the trawl net 8, a rear end line 11 is fixed to the hose 9. In order to move the line 11 closer to the boat 6, the trawl net 8 is moved forward relative to the boat 6 by using the towing underwater drones 4. When it is time to empty the trawl net 8, the hose 9 is pulled on board of the boat 6 by using the rear end line 11. The towing underwater drones 4 are used to position the trawl net 8 in an ideal position allowing the catch to be pumped on bord the boat 6 via the hose 9. This will typically be done by using a winch or winding gear configured for puling or lifting objects and bringing these objects on board the boat 6. Since the trawl net 8 remains under water while the catch is pumped on board, the emptying process is much faster than by using prior art solutions. Accordingly, is possible to bring the catch much faster to the land. Therefore, a higher quality of fish can be provided.

[0177] Each underwater drone 4 is providing a towing force F large enough to prevent generations of knots in the corresponding towing wire 15 extending between the underwater drone 4 and the trawl net 8.

[0178] Fig. 2A illustrates a top view of the system shown in Fig. 1C. It can be seen that underwater drones 4 are arranged in front of and at each side of the boat 6. In an embodiment, the underwater drones 4 are moved symmetrically relative to the longitudinal axis of the boat 6. In an embodiment, the trawl net 8 is moved under the boat while being moved symmetrically relative to the longitudinal axis of the boat 6.

[0179] Fig. 2B illustrates a side view of the system shown in and explained with reference to Fig. 2A, in a situation, in which the trawl net 8 has been moved in front of the boat 6 and close to the surface of the sea 12 by using the one or more steerable underwater drones 4.In this position, the rear end line 11 and the hose 9 it is attached to has been brought on board. Accordingly, the hose 9 can be connected to a pump (as shown and explained with reference to Fig. 6) to allow the entire catch or part of it to be pumped onboard via the hose 9.

[0180] Fig. 2C illustrates a top view of a system that is almost in the same configuration as shown in Fig. 2B. It can be seen that the trawl net 8 is positioned in front of and to the right of the boat 6. The skilled person would know that the trawl net 8 may positioned in a different position (e.g. in front of and to the left of the boat 6 by way of example).

[0181] The system and method according to the invention makes it possible to empty the trawl net 8 faster than by using prior art solutions. Accordingly, trawling with the boat 6 can be done much faster and thus it is possible to bring the catch much faster to the land. Therefore, a higher quality of fish can be provided.

[0182] Fig. 3A illustrates a side view of a system according to the invention, in a situation, in which the trawl net 8 has been moved in front of the boat 6 and close to the surface of the sea 12 by using the one or more steerable underwater drones 4. Two surface drones 40 are used to indicate the position of the trawl net 8. The system basically corresponds to the one shown in and explained with reference to Fig.

[0183] 2B. The system, however, comprises two surface drones 40 configured to indicate the position of the trawl net 8. Hereby, it is possible for other boats to visually detect the present of a trawl net 8 that is positioned under the surface of the sea 12. In an embodiment, each surface drones 40 is configured to float on the surface of the sea 12.

[0184] Fig. 3B illustrates a top view of the system shown in Fig. 3A. The two surface drones 40, 40' configured to indicate the position of the trawl net 8 are provided in front of the boat 6. Hereby, it is possible for otherboats to visually detect the present of a trawl net 8 that is positioned under the surface of the sea 12. The first surface drone 40 is attached to a first guiding wire 42, while the second surface drone 40' is attached to a guiding wire 42'. Each surface drone 40, 40' is steerable by using the control unit 14 (see Fig. 3A). In an embodiment, the surface drones 40, 40' are configured to identify fish. In an embodiment, the surface drones 40, 40' are configured to identify the location of the seabed.

[0185] It can be seen that the distance D between two of the surface drones 40, 40' is larger than the largest width W of the trawl net 8.

[0186] Fig. 4A illustrates a side view of a system comprising a boat 6 and a trawl net 8 that has been moved in front of the boat 6 and close to the surface of the sea 12 by using two steerable underwater drones 4. A single surface drone 40 is used to indicate the position of the trawl net 8. Fig. 4B illustrates a top view of the system shown in Fig. 4A. The system basically corresponds to the system shown in and explained with reference to Fig. 3A and Fig. 3B. The system, however, comprises a single surface drone 40 instead of two surface drones 40 as in Fig. 3A and Fig. 3B.

[0187] The single surface drone 40 is provided in front the two steerable underwater drones 4. The single surface drone 40 is provided basically along the longitudinal axis of the boat 6. The single surface drone 40 is provided at basically equal distance from the two steerable underwater drones 4.

[0188] Fig. 5A illustrates a side view of a system according to the invention. The system comprises a boat 6 provided at sea 13. To trawl nets 8 are attached to the boat 6. Each trawl net 8 is attached to the boat via a rear end line 11 that is attached to a hose 9 connected to the rear end of the trawl net 8. Each trawl net 8 is towed by two steerableunderwater drones 4. Each underwater drone 4 is attached to the trawl net 8 via a towing wire 15. Since the drones 4 are moved and thus are towing the trawl nets 8, each towing wire is 15 transferring a non-zero towing force. Accordingly, each towing wire 15 is basically straight.

[0189] Each underwater drone 4 is attached to the boat 6 via a guiding line 10. In an embodiment, each guiding line 10 comprises a metal wire. In an embodiment, the guiding line 10 is at least partly made of steel.

[0190] The boat 6 comprises a control unit 14, wherein the underwater drones 4 are steerable by using the control unit 14. The control unit 14 is configured for controlling the position and velocity of the underwater drones 4. Since there is a wired connection between the underwater drones 4 and the control unit 14, control signals may be sent to the underwater drones 4 from the control unit 14 via the guiding line 10. Likewise, information from the underwater drones 4 may be sent to the control unit 14 via the guiding line 10. In an embodiment, information from the underwater drones 4 is sent to the control unit 14 via a communication line (not shown) attached to and extending along the guiding line 10. In an embodiment, information from the underwater drones 4 is sent to the control unit 14 via a communication line that is integrated in the guiding line 10. Said information may include the position, speed and direction of the underwater drones 4.

[0191] A first surface drone 40 and a second surface drone 40' are used to indicate the position of the frontmost part of the trawl nets 8. The two surface drones 40, 40' are designed to indicate the position of the trawl net 8 for other boats. Hereby, it is possible for other boats to visually detect the present of a trawl net 8 that is positioned under the surface of the sea 12.

[0192] The first surface drone 40 is attached to a first guiding wire 42, whilethe second surface drone 40' is attached to a guiding wire 42'.

[0193] Fig. 5B illustrates a top view of the system shown in Fig. 5A. The system comprises a first surface drone 40 that is attached to the boat 6 via a first guiding wire 42. The system comprises a second surface drone 40 that is attached to the boat 6 via a second guiding wire 42'. The first surface drone 40 indicates the position of the leftmost and frontmost underwater drone 4. The second surface drone 40' indicates the position of the rightmost and frontmost underwater drone 4.

[0194] It can be seen that the rear end line 11 is attached to a hose 9. The hose 9 designed to allow the catch to be pump from the end portion of the trawl net 8 via the hose 9 on board the boat 6. The rear end line 11 would typically be so long that the trawl net 8 can be positioned in a large distance from the boat. At the same time, the rear end line 11 can be used to pull the hose closer to the boat 6 to allow the hose 9 to be connected to a pump on the boat 6 for pumping the catch on board the boat 6.

[0195] In an embodiment, the boat 6 comprises an echo sonar with an echo sonar field, wherein the echo sonar is arranged and configured to detect a position of the underwater drones 4 relative to the boat 6.

[0196] In an embodiment, each underwater drone 4 comprises a communication module and an echo sonar with an echo sonar field arranged and configured to communicate with the control unit 14 of the boat 6 by using the communication module. The communication module would typically be configured to send information to the control unit 14.

[0197] In an embodiment, the system is configured to:

[0198] - detect information including the position of the underwater drones 4 by using the underwater drones 4 and- send the detecting information to the control unit 14 of the boat 6 and - by using the control unit 14 steer the underwater drones 4 in dependency of the detecting information.

[0199] Since the trawl nets 8 are driven by underwater drones 4, the trawl nets 8 can (at least to some extent) be moved independently of the speed and position of the boat 6. Each pair of underwater drones 4 are attached to the two front end portions of the corresponding trawl net 8.

[0200] Fig. 6 illustrates a side view of a boat 6 pumping the catch from a trawl net 8 on board the boat 6. The boat 6 comprises a control unit 14 and one or more underwater drones (not shown) that are connected to a trawl net 8. The one or more underwater drones are steerable by using the control unit 14. The control unit 14 is configured to bring the trawl nets 8 under the surface of the sea 12 by controlling the position and velocity of the underwater drones while each underwater drone is connected to a corresponding trawl net 8.

[0201] It can be seen that the rear end line 11 is connected to a hose 9. The hose 9 is connected to the rear end of the trawl net 8 and configured to allow the catch to be pumped from the trawl net 8 to the boat 6 via the hose 9. This can be done by connecting a pump 44 to the free end of the hose 9. When the pump 44 is connected to the hose 9, the catch caught by using the trawl net 8 can be pumped on board the boat 6 via the hose 9.

[0202] There is a wired connection (via a line integrated into or attached to the guiding line 10) between the underwater drone (not shown) and the control unit 14. Thus, control signals may be sent to the underwater drones from the control unit 14 via the guiding line 10. Information (including the position, speed and direction of the underwater drone) from the underwater drone may be sent to the control unit 14 via theguiding line 10.

[0203] 5List of reference numerals

[0204] 2 System

[0205] 4 Underwater drone 6 Boat

[0206] 8 Trawl net

[0207] 9 Hose

[0208] 10 Guiding line

[0209] 11 Rear end line

[0210] 12 Sea

[0211] 14 Control unit

[0212] 15 Towing wire

[0213] 38 Pumping unit

[0214] 40, 40' Surface drone

[0215] 42, 42' Guiding wire

[0216] 44 Pump

[0217] F Towering force

[0218] D Distance

[0219] W Width

Claims

Claims1. Method for trawling with a boat (6), said method comprising:- providing at sea (12) a boat (6) having a trawl net (8), a control unit (14) and at least one underwater drone (4) that is steerable by using the control unit (14),- bringing the trawl net (8) under the surface of the sea (12) by using the least one underwater drone (4),- controlling the position and velocity of the at least one underwater drone (4) while the at least one underwater drone (4) is connected to the trawl net (8),wherein the method comprising:- bringing the trawl net (8) to a first position behind the boat (6) by using the least one underwater drone (4),- hereafter bringing the trawl net (8) to a second position in front of or next to the boat (6) by using the least one underwater drone (4), characterised in that in the second position pumping, by using a pump (44), a catch caught by using the trawl net (8) on board the boat (6) by using a hose (9) that is connected to the trawl net (8), wherein a rear end line (11) is attached to the hose (9),wherein the method comprising bringing the hose (9) on board the boat (6) by towing the rear end line (11).

2. Method according to claim 1, wherein the rear end line (11) is attached to the distal end of the hose (9).

3. Method according to claim 1 or 2, the method comprising:- by using the least one underwater drone (4) that is connected to the trawl net (8) by a towing wire (15), providing and maintaining a towing force (F) large enough to prevent generations of knots in the towing wire(s).

4. Method according to one of the preceding claims, the methodcomprising:- in the second position, by using the least one underwater drone (4) securing that a rear portion of the trawl net (8) is maintained in a position no longer than 50 m from the boat (6).

5. Method according to one of the preceding claims, the method comprising using two underwater drones (4) for each trawl net (8), wherein each underwater drone (4) is steerable by using the control unit (14).

6. Method according to one of the preceding claims, the method comprising:- using a first and a second trawl net (8) to trawl with the boat (6);- bringing each of the trawl nets (8) to a first position behind the boat (6) by using the least one underwater drone (4),- hereafter bringing the first trawl net (8) to a second position in front and at the left side of the boat (6) by using two underwater drones (4) and bringing the second trawl net (8) to a second position in front and at the right side of the boat (6) by using two underwater drones (4), - in the second positions pumping, by using a first pump (44) a catch caught by using the first trawl net (8) on board the boat (6) by using a first hose (9) and by using a second pump (44) a catch caught by using the second trawl net (8) on board the boat (6) by using a second hose (9).

7. Method according to one of the preceding claims, the method comprising:- providing at least one of the at least one underwater drone (4) with an echo sonar (20) with an echo sonar field arranged and configured to communicate with the control unit (14) by using a communication module (24), said communication module (24) being configured to send information to the control unit (14),- detecting information (26) including the position of the one or more underwater drones (4) by using the one or more underwater drones (4) and- sending the detecting information (26) to the boat (6) and- by using the control unit (14) steering the at least one underwater drone (4) in dependency of the detecting information (26).

8. System (2) configured to carry out the method according to one of the claims 1-7, the system (2) comprising:-a boat (6),- at least one trawl net (8),- a control unit (14),- at least one underwater drone (4) that is steerable by using the control unit (14),wherein the system (2) is configured to:- bring the at least one trawl net (8) under the surface of the sea (12) by using the least one underwater drone (4),- control the position and velocity of the at least one underwater drone (4) while the at least one underwater drone (4) is connected to the trawl net (8),wherein the system (2) is configured to:- bring the at least one trawl net (8) to a first position behind the boat (6) by using the least one underwater drone (4),- hereafter bringing the trawl net (8) to a second position in front of or next to the boat (6) by using the least one underwater drone (4), characterised in that in the second position pumping, by using a pump (44), a catch caught by using the trawl net (8) on board the boat (6) by using a hose (9) that is connected to the trawl net (8), wherein a rear end line (11) is attached to the hose (9),wherein the system (2) is configured to bring the hose (9) on board the boat (6) by towing the rear end line (11).

9. System (2) according to claim 8, wherein the at least one underwater drone (4) comprises an echo sonar (20) with an echo sonar field arranged and configured to communicate with the control unit (14) by using a communication module (24), said communication module (24) being configured to send information to the control unit (14), wherein the system (2) is configured to:detect information (26) including the position of the one or more underwater drones (4) by using the one or more underwater drones (4) and- send the detecting information (26) to the boat (6) and- by using the control unit (14) steer the at least one underwater drone (4) in dependency of the detecting information (26).

10. System (2) according to claim 8 or 9, wherein the boat (6) comprises an echo sonar (28) with an echo sonar field, wherein the echo sonar (28) is arranged and configured to detect a position of the at least one underwater drone (4) relative to the boat (6).

11. System (2) according to one of the claims 8-10, wherein the rear end line (11) is attached to the distal end of the hose (9).

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