Net mouth height vector trawlnet

Abstract

To provide a bottom trawl system which operates by fixing a small number of floats to a towing rope, releasing the rope with the float from a fishing boat and tying it to the net, making it slightly longer than a straight line, and the angle of elevation between the vector direction, the horizontal line and the rope diagonally upward forward is preferably between about 65 degrees and about 85 degrees, measuring the tension with a constant load torque meter on the side of the fishing boat, keeping the longitudinal force below a certain level, reeling it in and shrinking it, sinking the float, and raising the net opening of the bottom trawl to prevent the net bottom from separating from the seabed; the towing rope being automatically driven by a motor and a driver; to deal with the case of entering a deep fishing ground by letting out from the ram and reducing the tension; regarding the processing of the net, an additional lowering operation being performed when the eaves net connected in front of the head rope is hauled up; by summarizing these technologies, to make it possible to prevent fishes from escaping from the net mouth and automatically release the towing rope when the water depth increases; conversely, when the water depth becomes shallower, to make it possible to provide a bottom trawl fishing gear that retracts and adjusts the rope, lowering the float attached to the towing rope and raising the net mouth, so that the net mouth does not separate from the seabed.SELECTED DRAWING: Figure 1

Description

[0001] New bottom trawl net made by fishermen [Technical Field]

[0002] This is a bottom trawl fishing gear newly made by fishermen. A new rope with one or more floats or floats attached and two conventional warps are let out from the fishing boat and tied to the net in advance, so that the net is pulled with three ropes. A transmitter and receiver, which are part of the fish finder on the fishing boat, are attached to the rope, or an underwater camera is attached to part of the net, so that the shape of the net underwater and information on the fish schools on the seabed can be seen on board, along with the height of the net opening, and seafood can be caught.

[0003] In addition to the two conventional warps, three ropes with one or more floats attached are released and tied to the bottom trawl net in advance, and the length and tension of the rope are automatically adjusted by extending and retracting it in conjunction with the fishing boat's winding drum, so that one or more floats or floating bodies are floating on the sea surface from the beginning.When towing, the rope is wound up on the boat and the floats are pulled into the sea, giving the rope vector tension to raise the net opening.At the same time, a fish finder is used to display one or more of the net shape, seabed and net bottom images, and fish positions using ultrasonic echoes sent into the sea, or an underwater camera is used to view seabed images, and net information such as the depth of the seabed and net height can be confirmed.The length of the towing rope and the tension are determined by the subtle buoyancy of the floats as they sink below the sea surface, and these serve eleven purposes. The first is a small bottom trawl fishing method in which a portion of the net mouth is raised, the total float weight kept below 25 kg, and attached to a certain section of the rope. The rope is then let out to achieve the initial state (8), and gradually wound around the drum, causing the floats floating on the surface to sink below the surface. The rope, which is at an angle of elevation, is then brought to a state below state (7). The force of the floats trying to float is transmitted via the rope to a portion of the net, keeping the net mouth elevated and towing it. The optimal amount of floats to sink is set just before the net floats, and all floating floats are removed to prevent the net bottom from separating from the seabed, preparing for the next catch. This fishing gear efficiently catches marine products such as tilefish and flounder, as well as shrimp, crab, and squid, by raising the net mouth above the sea. The second method involves leaving a certain section and the end of the rope just deep enough to allow it to sink, and then attaching it to the point where the elevation angle intersects with the sea surface. The float weight is set to 25 kg for small bottom trawl nets, and 65 kg for total float weight for trawl nets. The tension through the rope is transmitted to part of the net, raising the height of the net mouth. The net will not separate from the bottom. The optimum true float weight is the sinking just before the net separates from the bottom, and any floats remaining afloat after that are removed from the rope to protect the net from the bottom due to waves and swells. The third effect is that the trawl net is made by combining at least one of the following: floats on the towing rope, ropes with floats, fish finders, silver paper plates attached to the net, ultrasonic aluminum reflective thin metal plates, spring tension meters, sensors, underwater cameras, drums, floats, floats, shielded wires, cable wires, etc., to increase the height of the bottom trawl net and prevent the net from separating from the seabed. The fourth is mid-water dragnets, which use buoys to move the net up and down quickly, providing a mechanism for increasing catches. If there are dangerous objects or obstacles on the seabed, the rope is reeled in quickly to float the net. If the net leaves the seabed, a warning light such as a red lamp is activated. Fifth, small bottom trawls monitor whether the bottom of the net is touching the seabed using a fish finder attached to part of the net or an underwater camera.

[0004] Sixth, if we illustrate the elevation angle between the towing rope and the horizon, from Figure 1, elevation angle situation (1) is approximately 0 degrees, elevation angle situation (2) is approximately 15 degrees, elevation angle (3) is approximately a straight line connecting the boat and the net, elevation angle situation (4) is approximately 30 degrees, elevation angle situation (6) is approximately 60 degrees, elevation angle situation (7) is approximately 75 degrees, elevation angle situation (8) is 90 degrees, the towing rope is let out and one or more floats with devices attached are placed in the middle, and it is desirable that the floats in situations (6) and (7) are extended above the sea surface and are not too long to come close to the straight line distance between the fishing boat and the net connected by the towing rope.

[0005] The seventh method is to use a spring tension meter attached to the bottom trawl net in addition to the towing rope. Tie the towing rope to one or more floats and a portion of the head rope with sufficient slack. This will ensure a good net opening height and a straight-line distance (3) between the bottom trawl net and the boat (4) will be avoided. An elevation angle of (4) or less or (9) or more will result in negative resistance. For elevation angles above (7) and above (6), a setting between (7) and (6) is desirable. The pulling force is monitored using a tension meter, sensor, underwater camera, fish finder, or underwater camera footage, taking into account the length of the rope. Attaching a weight, such as a chain, to the ground rope is necessary to prevent the net bottom from lifting, creating gaps, and separating from the bottom.

[0006] The eighth is the blowing of the towing rope due to the current speed, and the float floats on the surface of the sea up to the elevation angle situation (7) = elevation angle situation (8). When the float is floating on the sea surface, no tension is generated, but when it goes below the sea surface, tension is generated through the towing rope to the elevation angle situation (6) elevation angle situation (7), which is effective, but the rope causes the bottom trawl net to float above the seabed, and fish pass through between the ground dope and the seabed. The ninth method requires the strength to make the net as high as possible and to prevent it from coming off the bottom.Since this is done using a single towing rope, the net is monitored with a fish finder using an ultrasonic reflecting metal plate. The tenth point is that the towing rope conditions in elevation angle (2), elevation angle (3), elevation angle (4), elevation angle (5), elevation angle (6), elevation angle (7), and elevation angle (8) are shown in Figure 1, and the relationship between the resistance and buoyancy of a conventional towing rope and the vector resistance is shown in Figure 3. However, mid-water trawl nets can be pulled with a large, powerful force by the towing rope. Bottom trawl nets always have the problem of the net separating from the bottom. [Technical Field]

[0007] This invention is a mechanism for raising the height of the net mouth of bottom trawl nets used in fishing, which can be made using readily available materials, by adjusting the shape of the net to the angle of elevation between the towing rope and the horizon, using a fish finder or underwater camera to view the seabed, jumping over obstacles in the net to avoid them, chasing schools of fish, or in an emergency, by quickly reeling in the drum to lift the net off the seabed and remove it, so that the height of the net mouth cannot be raised suddenly. [Background technology]

[0008] The resistance R of the towing rope with floats or floats used in bottom trawl nets is R=aV squared, and the author has developed this in patent application 1973-27965. The towing speed of the net is about 4 knots, and the resistance and buoyancy of the towing rope are shown in the vectors in Figure 4, where the force of the floats is eliminated and the only thing felt is resistance. First, in addition to the flow resistance of the towing rope and floats, one or more subtle floats or floats that increase the net height add a buoyancy force as they sink, gradually increasing. Next, the net is pulled with such force that it easily floats off the seabed, which can be fatal. The 11-eye net is a bottom trawl, and if the net floats, it becomes a trawl, and the fish escape through the gaps, resulting in the catch escaping. If the net can be prevented from floating and the opening of the net can be increased by 1.5 times or more with minimal expense, this alone will reduce the cost of heavy oil for the fishing boat, making it cost-effective and increasing profits. If the net floats, it is sufficient to attach weights made from used parts such as chains, china, and wire, and although there are limits, the expenses will be minimal. [Prior art documents]

[0009] [Patent Document 1] Patent Application No. 48-27965 [Patent Document 2] Patent Publication No. 49-115878 [Patent Document 3] Tokkosho 46-5015 [Patent Document 4] Patent Publication No. 2002-90453 [Patent Document 5] Saneaki 63-53264 [Patent Document 6] Patent Publication No. 1-202232

[0010] Patent document 1 describes a trawl net, patent document 2 describes a bottom trawl system, and patent document 3 describes how to separate a towing rope. Patent document 4 describes a fish finder. Patent document 5 describes a trawl net with a deterrent device. Patent document 6 describes the up and down movement of a trawl net. The three-strand trawl method was invented by us.

[0011] When the towing rope is pulled strongly, the resistance of the net and float plus the resistance of the rope from the boat to the net plus the resistance of the wind create a component force of a vector in the vertical direction, increasing the mesh size.

[0012] Before the towing rope is released, this invention uses the towing rope to raise the net mouth, and combines one or more of the following: a fish finder, an underwater camera, a spring-type tension meter, a sensor, a touch panel, a switch, an underwater camera, a red light, a weight, an alarm device, a chain, a motor, a rope, a shielded wire and a winding drum, and an ultrasonic-reflecting metal sheet. The resulting sensor and switch can be used as a touch panel or an underwater camera to act as a red light or other alarm signal for the fish finder. This design was developed to clarify the proper angle of elevation between the rope used to raise the net mouth and the horizon for bottom trawl fishing, and to increase catches. Close examination reveals that the mesh of the net opens vertically, forming a diagonal square. Until then, resistance would pull the net horizontally, crushing the mesh in the side nets and separating the ground rope from the seabed. This allows fish such as tilefish and flounder, as well as shrimp, crabs, and squid, to escape through the gaps created by the bottom trawl, resulting in a loss of catch. Fish, shrimp, and crabs will laugh at you. Other factors to consider include increased towing speed, increased depth, and the presence of obstacles at the bottom. Even if the water gets deeper, the net will float. Only a fish finder and an underwater camera can detect this.

[0013] Due to the vector pointing diagonally upwards, the angle of elevation between the towing rope and the horizon at the point where the towing rope is fastened to part of the head rope is as follows: Elevation angle (1) = 0 degrees, Elevation angle (2) = approximately 15 degrees, Elevation angle (3) = almost a straight line connecting the boat and the net, Elevation angle (4) = approximately 30 degrees, Elevation angle (5) = approximately 45 degrees, Elevation angle (6) = approximately 60 degrees, Elevation angle (7) = approximately 75 degrees, Elevation angle (8) = 90 degrees, where wind is a negative factor. Of the effective angles of elevation, an angle of elevation between 60 degrees and approximately (7) 75 degrees is the most effective for raising the net mouth, while (3) is the shortest and almost straight line, and (8) 90 degrees may not be desirable due to increased resistance caused by wind from flowing water. It is possible that the fishing boat may suddenly enter a deep seabed, so it is best to raise the net mouth with a gentle, delicate tension at an elevation angle of approximately 75 degrees. If the tension suddenly increases, it indicates that the net has left the seabed, and the tension must be relaxed to allow the net bottom to settle on the seabed.

[0014] To release the towing rope, we install electromagnetic, electronic, transmitting / receiving equipment, and camera components in a sealed counter pressure vessel. Here, we have conducted bottom trawl experiments using an ocean current tank, and we are well aware of how the net changes with the current speed. I think that even fishermen who are unfamiliar with model experiments are amateurs. This is because we know well from tank experiments that a weak force raises the net opening, and then this weak force gradually builds up to a strong force, which separates the net from the seabed and then causes it to float. Seeing is believing.

[0015] One end of the towing rope is connected to the drum and motor via a strain gauge or spring tension meter, and can be rotated forward or backward depending on the tension. Using a strain gauge or constant force spring tension meter as a tension meter for the towing rope during operation, the rope tension is measured using only the resistance of the rope and float, set at the average water depth, and then rotate forward or backward using + / -, allowing for as scientific an extension and contraction as possible during operation.

[0016] According to this table, once the distance in the middle of the sea in the fishing area, the length of the towing rope, the size of the net, the water depth, the specific gravity of the rope, and the length of the net are determined, the length of the towing rope can be determined by drawing a scaled diagram between the horizontal line on the net, as shown in Figure 5.

[0017] To determine the tension in the fixed part of the towing rope end boat, carefully observe the spring gauge, strain gauge tension meter, and spring tension meter to find the resistance when the net is raised, and then compare it with the image from the fish finder and observe and think carefully about it.

[0018] When the red light comes on, sound an alarm and loosen the towing rope without pulling. It is difficult to select the specific gravity, thickness, and material name of the towing rope, so no model experiments have been conducted, but it has been found that good results can be obtained if one or more tension measurement systems using elastic springs, rubber, or a constant load system are required.

[0019] This combination of a fish finder or underwater camera and a towing rope equipped with a constant-load spring automatically raises the net mouth, preventing the fishing boat from slowing down or coming off the bottom. This solves the critical problem of solving numerous conflicting factors, including marking the net at a certain elongation. By maintaining a constant tension on the rope, the net maintains a constant load, resulting in maximum catch. A touch-panel switch system allows for automatic to manual operation, achieving the highest net heights since the dawn of bottom trawling. Furthermore, attaching one or more soft reflectors to a portion of the net emits ultrasonic waves, which are then converted into echoes. The echoes are then imaged and collected by an onboard fish finder, providing a good indication of the direction of the fish schools.

[0020] If a large triangular net is placed in the side net of the overhead net, and a eaves net and sinkers are added in front of the head rope, the height of the net will be lowered and the net mouth can be closed after the towing rope is cut off.However, in Patent Document 5, where the mid-water trawl tends to move up and down when a large force is applied to the towing rope, it is not possible to operate the trawl with the net bottom touching the seabed while keeping the net mouth raised.

[0021] This system is capable of mid-water drag nets, but when it comes to trawl nets, beam trawl nets, side trawl nets, shrimp trawl nets, small bottom trawl nets, and medium-sized offshore bottom trawl nets, if a large force is applied to the net mouth diagonally upwards, it becomes impossible to raise the net mouth and touch the bottom of the net to the seabed and operate. [Brief explanation of the drawings]

[0022] [Figure 1] Schematic diagram of the bottom trawl, towing rope and float system [Figure 2] An explanatory diagram of the resistance tension during operation when the net's flow resistance increases. [Figure 3] An explanatory diagram of the vector direction of the net height factor. [Figure 4] An explanatory diagram of net height displayed on a fish finder. [Figure 5] Exploded view of mesh parts

[0023] 1 to 5 show and briefly explain an embodiment of the present invention. [Example]

[0024] In Figures 1 to 7 according to this embodiment, 1 is a small bottom trawl fishing boat, 2 is a bottom trawl net, 3 is the seabed, 4 is the sea surface, 5 is a towing rope, 6 is a perpendicular line, 7 is the elevation angle between the horizontal line and the towing rope, 8 is a head rope, 9 is a ground rope, 10 is a float on the sea surface, 11 is the rope situation at an elevation angle of 0 degrees in (1), 12 is the elevation angle and rope situation in (2), 13 is the rope situation in (3), 14 is the rope situation at an elevation angle of 30 degrees, 15 is the rope situation at an elevation angle of approximately 45 degrees, 1 6 is the rope elevation angle when it is approximately 60 degrees, 17 is the rope condition when the elevation angle of the rope of (7) is set to approximately 75 degrees, 17 is the rope condition when the elevation angle of the rope of (7) is set to approximately 75 degrees, 18 is the rope condition of (8) when the elevation angle is set to approximately 90 degrees, 19 is the rope elevation angle condition at approximately 105 degrees, 20 is a weight or sinker, 21 is a float under the sea surface, 22 is a length meter, 23 is a fish finder or underwater camera, 24 is an ultrasonic reflector, 25 is a vector, and 26 is an alarm device.

[0025] We analyze the net height and the resistance of the towing rope and float, and we want to know whether a lifting board was used to raise the net opening, how much small force was used to pull it in the elevation direction, and how much the numbers displayed on the fish finder or underwater camera actually represent. We want to know whether they are the numbers on the weak tension meter used to measure the resistance of the gradually increasing net height. The angle with the horizon (elevation angle) is important, and the length of the towing rope is also an important factor. By extracting the numbers on the tension meter and combining them with the fish finder or underwater camera footage, we can understand the net shape. The force pulling from behind is also an important factor, depending on the fishing boat, water depth, speed, net size, etc., and also the influence of inertia.

[0026] Figure 1 is a simplified scale diagram of bottom trawl operation. While figures vary depending on the fishing boat and fishing ground, assuming a 19-ton single-row bottom trawl system and a fishing ground 80 meters deep, the warp length is approximately 200 meters. The towing rope is shielded wire, as short as possible, and the net mouth is kept high with a delicate adjustment. One end is tied to the head rope, and the other end is fixed to the winding drum via a tension meter. The fish finder is adjusted to measure the net mouth height, the ground rope distance, and the fish so that they appear on the screen. The elevation angle (1) is approximately 0 degrees, the elevation angle (2) is approximately 15 degrees, the elevation angle (3) is approximately a straight line connecting the boat and the net, the elevation angle (4) is approximately 30 degrees, the elevation angle (5) is approximately 45 degrees, the elevation angle (6) is approximately 60 degrees, the elevation angle (7) is approximately 75 degrees, and the remaining elevation angle (8) is approximately 90 degrees, but attention should be paid to wind.

[0027] Figure 1 is scaled correctly, allowing us to determine the length of the towing rope, i.e., the distance between the fishing boat and the net. By accurately recording the gentle curve and the position of the float, the length of the towing rope can be determined accurately. The height of the net mouth has increased from 2m to nearly 4m.

[0028] In Figure 2, the angle of elevation of the towing rope with respect to the horizon in situation (3) is approximately 30 degrees, and in situation angle (3) it is almost straight. Winding the rope on the drum at an angle of approximately (3) 30 degrees or less can cause excessive tension and become a factor. Figure 3 is a correlation graph of the resistance of the float and floatation body on the head rope at 2 knots or 4 knots. At 4 knots it feels like there is only resistance.

[0029] Figure 4 shows the resistance of the head rope float and the net, using shielded wire for the towing rope, sealing the float, and attaching a transmitter. This makes sense as the net will not be lifted even with a small, gentle force. Balancing the tension of the trowel seems simple when looking at a photo taken in a circulating water tank, but in reality it is difficult because we are under the sea and cannot see.

[0030] Figure 1 is a schematic diagram of this bottom trawl. The towing rope 5 has a shape (4), but the float that floats on the sea surface emits radio waves that determine the position behind the fishing boat and the distance. It is not straight, but has a sufficient length. Light tension is desirable, but when it enters a straight state (3), the tension increases. If strong tension is applied to the towing rope, the net will float above the seabed. This must be avoided. Therefore, the length of the slack portion is increased, avoiding the tensed portion, and the float sinks below the sea surface, so it can be contained by simply submerging. Operations can continue as is. The float sinks with a small force, resulting in a very small force.

[0031] As shown in Figure 5, the net opening height can reach from approximately 2m to nearly 4m. Operations can continue as is. If the weak tension in the net is shown as a vector, it becomes as shown in Figure 7, and sufficient triangular nets are placed on both sides of the ceiling net and a eaves net is placed in front.

[0032] As shown in Figure 5, by sinking the float from the sea surface, a weak force is transmitted to the towing rope, and the towing rope can be sunk when passing behind a fishing boat or other vessel, eliminating the risk of it being cut, and providing the advantage of safe operation. It is clear that it is better to keep the float submerged and stable than to move up and down due to waves and swells, and this will produce better results.

[0033] You can use a pressure-resistant underwater camera to check whether the net is loose from the bottom. Pulling gently with a small force in an upward, forward diagonal direction will prevent the bottom from floating (it is a good idea to wind a balanced chain around the ground rope beforehand to make it heavy enough). Be careful not to go too fast.

[0034] Figure 5 shows containers of kelp seeds and other perforated items being attached to nets, scattering the seeds during fishing operations in the hope of improving the fishing ground environment in the long run. Trawl fishing is banned across the United States because it captures bottom-dwelling organisms completely, but Japan has set up closed fishing periods to protect the catch, and maintaining resources is also important. Trawl fishing is banned nationwide in the United States, but what about Japan? What about mid-water trawls, trawls, and bottom trawls? [Industrial Applicability]

[0035] It seems that a major company may have mistaken it for a homemade product, so there seems to be no problem. However, because the length, tension, vector, and float buoyancy had not been resolved, the previous test operation, conducted in Hiragata City, Ibaraki Prefecture, failed because the float force was too strong and the net floated, making it impossible to measure. A public institution has offered to purchase it.

[0036] Floating bodies exert a large force on the mid-water and trawl nets when moving up and down during mid-water dragging, and although they are not often used for small dragging nets, they can be used when necessary. Floating lifting bodies are connected to the towing rope fishing boat, equipped with instruments, etc., and function as a relay station; they are sealed, pressure-resistant, have lifting force, and have space.

[0037] Sign display 1 fishing boat 2 Bottom trawl 3 undersea, 4 sea level 5 Towing rope 6 Vertical Lines 7 horizontal line 8 Head Rope 9 Ground Rope 10 Float on the sea surface 11 (1) situation = elevation angle 0 degrees 12 (2) situation = elevation angle of approximately 15 degrees 13 (3) Situation = Elevation angle is almost straight 14 (4) situation = elevation angle of approximately 30 degrees 15 (5) situation = elevation angle is almost 45 degrees 16 (6) situation = elevation angle almost 60 degrees 17 (7) situation = elevation angle is almost 75 degrees 18 (8) situation = elevation angle almost 90 degrees 19 (9) situation = elevation angle almost 105 degrees 20 weights or sinkers 21 Underwater float 22 Tension meter 23 Fish finder 24 Ultrasonic reflector 25 Vector 26 Alarm device, red lamp, buzzer 27 Triangular mesh 28 Nokiami 29 Towing rope 30 Warp

Claims

1. In this invention, it is fundamentally physically impossible to maintain a three-dimensional shape with two supports. In addition to the two conventional warps let out from a bottom trawl fishing boat, a new method is used to limit the total buoyancy of the towing rope and one or more floats attached to a certain section of the rope, with the total float weight limited to 25 kg for small bottom trawls, 40 kg for offshore bottom trawls, and 65 kg for trawl nets. Applying a large force will cause the net to float off the seabed, so the force must be as subtle and small as possible, and one or more floats are attached to the rope at a certain interval so that they float on the sea surface. The rope is then wound up, and the angle of elevation between the rope and the horizon is kept between approximately 60 degrees and approximately 85 degrees, allowing the net to be lifted as efficiently as possible in the forward, upward diagonal direction. The bottom trawl fishing gear is characterized in that the shape of the net in the sea can be monitored on the fishing boat by using a fish finder or an underwater camera in combination with a touch panel and a shielded wire.

2. The fixed section means that the tip of the rope is left at the water depth, and the rope is attached from there, and is attached between fixed points where the elevation angle and the sea surface intersect, the float amount is within 25 kg for the small bottom trawl net, and the rope is wound up to gradually sink the float, within 40 kg for the offshore bottom trawl net, and within 65 kg for the trawl net, and the rope is wound up to sink the float below the sea surface, and the buoyancy is transmitted to the net via the rope, which becomes the force to lift the net, and the net opening is raised with the vector in the forward and upward diagonal direction.

3. The float is attached to the towing rope and floats on the sea surface during operation, and is connected to the bottom trawl net during trawl fishing. The rope is wound up to sink the float on the sea surface below the sea surface, and its buoyancy is connected to the net mouth via the towing rope, allowing the net mouth to be raised to a height of approximately 2 to 4 m. At this time, it is important to ensure that the net bottom does not separate from the seabed and not to apply excessive large force. In the case of the small bottom trawl net, the total buoyancy of the floats on the sea surface is within 25 kg, in the case of the offshore bottom trawl net, the total buoyancy is within 45 kg, and in the case of the trawl net, the total buoyancy is within 65 kg. The floats are attached to the towing rope, attached at a certain interval, and operated between the elevation angle of approximately 60 degrees and the elevation angle of approximately 85 degrees. The bottom trawl net with a raised net mouth according to claims 1 and 2, characterized in that from the next time the net is cast, the floats exert buoyancy in the water, allowing them to cope with bad weather caused by waves, swells, etc., and any floats that do not sink are removed from the rope to lift the net mouth.

4. A bottom trawl net as claimed in any one of claims 1 to 3, characterized in that the ultrasonic signal transmitted from the fish finder or an underwater camera is attached to a part of the net, the rope is the shielded wire, and one or more reflectors are attached as parallel to the horizon as possible to generate the echoes, which are information on the shape of the net, the seabed, and the fish school, and the echoes are visualized by the fish finder or underwater camera to display an alarm when the net separates from the seabed, to alert the user to any dangerous objects on the seabed.

5. A bottom trawl net according to claims 1, 2, 3 and 4, characterized in that the towing rope let out from the fishing boat of the bottom trawl net is fastened to a part of the net mouth, and one or more floats, and one or more resin floats or floats are attached at intervals along the vertical length at the sea surface, and floated on the sea surface, the towing rope is extended from the net to the sea surface, the elevation angle is increased to 15 degrees or more, the winding elevation angle status rank is lowered, and the floating one or more floats are sunk, and the force is transmitted to the net mouth via the towing rope, raising the net mouth.

6. The angle of elevation between the horizontal line of the bottom trawl net's mouth and the towing rope is set to approximately 60 degrees or approximately 90 degrees, particularly between approximately 65 degrees and approximately 85 degrees, the delicate force acting on the towing rope in bottom trawl fishing is safe, the small force acting on the small bottom trawl net is delicate regardless of whether there is a catch or not, the total float buoyancy of the small bottom trawl net is approximately 25 kg or less, the tension vector of the trawl net is diagonally upward forward, and the angle of elevation is ideally between 60 degrees and 90 degrees. A bottom trawl fishery in which a part of the mouth of the bottom trawl net is kept elevated to make it difficult to separate from the seabed as described in claims 1, 2, 3, 4 and 5, characterized in that the large force at the edge of bottom-off or mid-water trawl fishing is measured and necessary additional weights are added to make it difficult to separate from the bottom.

7. The float is attached to the towing rope, and when the resistance of the rope from the float resistance to the net, which has a large netting resistance, is added to the resistance of the float, the resistance becomes a vector direction that raises the net opening, and the force that makes the net and the mesh approximately square is the vector direction that raises the net opening, and the weak force that raises the net opening is pulled upward, and the angle of elevation with the horizon is greatly influenced by a forward diagonal upward direction. A bottom trawl net that is difficult to separate from the bottom according to claims 1, 2, 3, 4, 5 and 6, characterized in that it is kept from separating from the seabed by being part of the standard mean float attachment point, and a chain or a Seto weight is attached to prevent the bottom from separating.

8. 8. A bottom trawl net, trawl net, offshore bottom trawl net, small bottom trawl net, two-saw trawl net or other drag net system for raising the net mouth according to claims 1, 2, 3, 4, 5, 6 and 7, characterized in that in the dangerous waters where there is an obstacle on the seabed, one or more of the sonar image such as a red lamp or buzzer, the seabed image captured by a fish finder or underwater camera, the net-shaped image, the distance between the seabed and the net bottom, the fish shadows, etc. are selected and displayed, and the towing rope is shortened by the drum, and maintenance is carried out while the alarm signal disappears or until the elevation angle of the towing rope is restored, and the fish finder, the towing rope, the bottom trawl net, and the sunken floats are attached and the non-sunken floats are detached and the height is maintained.

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