JP2000102333A - Trawl fishing net with submerged plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a trawl fishing net device suitable for quantitatively collecting the fry of small pelagic fishes at a high speed without being affected by the speed of a ship and the state of the sea. SOLUTION: This trawl fishing net with a submerged plate is obtained by attaching the curved submerged plate 2 to a place below the net opening frame of the trawling fishing net 1 through suspending cords 4 so as to maintain a constant angle of attach. Floats 7 for bringing the total weight of the trawl fishing net 1 in water to about zero are preferably attached to the upper portions of the opening frame of the trawl fishing net 1 with the submerged plate. The curved submerged plate 2 comprises a vertical blade 21 and horizontal blades 22 projected from both the sides of the vertical blade. The horizontal blades 22 have upward curved cross sections, respectively, and both the horizontal blades 22 are bound to each other so that the angles of the horizontal blades between their blade surfaces and horizontal surfaces are equal to each other. The curved submerged plate 2 is suspended with two right cords 4 and two left cords 4, whose lengths are approximately equal. When a curved submerged plate 2 having a longitudinal length/latitudinal length ratio of 6.0, a camber ratio of 15% and a dihedral angle of 20 degree is used, the submerging characteristic of the curved submerged plate 2 is enhanced about two times those of conventional submerged plates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a trawl net device suitable for collecting juveniles and larvae. More particularly, the present invention relates to a trawl net device suitable for collecting small-sized larvae of small floating fish such as sardines, sardines and anchovies at high speed and quantitatively.

[0002]

2. Description of the Related Art Estimation of fish species resources by collecting fry and larvae is an indispensable means for fishery resource management.
Traditionally, fry surveys have included Isaacs Kid Mid-Troll, Tucker Troll and Rectangular Mid-Troll (RMT: Re
ctangular Midwater Trawl), MOCNESS: Multiple Opening / Closing Net and
Various fry collection nets such as Environmental sensing System are used. However, the Isaacs Kid Middle Troll is capable of high speed dragging at 2.5m / sec or more,
The seine water depth and net mouth cross-sectional area change depending on the ship speed and other factors, making quantitative collection difficult. The rectangular middle trawl can be opened and closed with four horizontal bars at the mouth, but the towing rope is attached only to the bar at the top of the mouth, and the net mouth is inclined, so the towing speed must be kept below 1.0 m / sec. There are disadvantages that cannot be obtained. In addition, the multi-stage opening / closing net with an environmental sensor has a limit of towing speed of about 0.7 to 1.2 m / sec. Therefore, in order to quantitatively collect the fry of the target fish species, a high aperture ratio (the value obtained by dividing the total area of the opening of the mesh by the area of the mesh opening: indicates the filtering capacity of the net)
It is necessary to develop fishing gear that has the function of collecting only the sample at the target water depth and that does not change the towing net depth and net mouth area due to changes in ship speed or sea conditions. still,
A trawl net device in which a dive plate is mounted below a net frame of a small trawl net has already been used in Isaacs Kid middle trawl.

[0003]

SUMMARY OF THE INVENTION The present invention has been developed in response to the above-mentioned needs, and provides a trawl net apparatus suitable for collecting small-sized pelagic larvae at high speed and quantitatively. That is the task.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a dive in which a curved dive plate is attached to a trawl net by a suspension cable so as to maintain a constant angle of attack below a net opening frame. It is a trawl net with a plate. Also preferably,
This is a trawl net with a dive board provided with a float for making the underwater weight of the entire trawl net close to zero above the net opening frame.

In general, the opening of the trawl net is constituted by a net opening frame, a plate frame attached thereto, and a depressor (sinking tool) suspended below the net frame. The dive plate referred to in the present invention is a type of depressor and has a hydrofoil structure, and works to sink the net by the lift below it. The dive board in trawl fishing is an important device for sinking the trawl net to the desired depth.

[0006] In the trawl net with a dive plate of the present invention, a curved dive plate is used. The curved underground plate referred to in the present invention is:
It consists of a vertical wing and horizontal wings that protrude on both sides of the vertical wing.The horizontal wing has an upwardly curved cross section, and both horizontal wings are joined so that the angle between the wing surface and the horizontal plane is equal. It has a certain structure. Note that having a cross section in which the horizontal blade is curved upward means that the side surface of the horizontal blade is curved upward in an arc shape, and the horizontal blade is formed into a shape just like a gutter. The curved underwater plate of the present invention can generate a high sedimentation force because it has the curved horizontal wings.

In the present invention, the horizontal wings of the curved underwater plate are mounted so as to always maintain a constant angle of attack. Specifically, it is preferable that the curved underwater plate be attached with two left and right suspension cables of approximately equal length while maintaining an angle corresponding to a preset elevation angle.

[0008] The shape of the curved underwater plate of the present invention can be represented by numerical values such as a dihedral angle, a camber ratio, and an aspect ratio.
These terms are used to describe the shape of the wing of an airplane in aeronautical engineering, and are used internationally in the field of fishing gear as the same meanings. Explaining for reference, the dihedral angle refers to the angle between the wing surface of the horizontal wing and the horizontal plane, and the warpage ratio represents the degree of curvature of the side surface of the horizontal wing, and the width of the horizontal wing (horizontal wing) Length of the front and back direction)
Is the ratio of the depth of the gutter-like curvature to the depth of the gutter. The aspect ratio refers to the ratio between the blade length and the blade width of the entire dive plate.

In the trawl net with a dive plate of the present invention, a curved dive plate having excellent dive force characteristics is used. Specifically, it is preferable to use a curved underwater plate formed with an aspect ratio of 6.0, a warpage ratio of 15%, and a dihedral angle of 20 degrees. As shown in a test example described later, the curved underwater plate thus formed has a maximum dive force coefficient of 1.57, and the dive characteristics are approximately twice as large as those of the conventional Isaacskid middle-layer trawl plate. It has been confirmed to be up.

In the trawl net with a dive plate of the present invention,
It is desirable to attach a float above the mesh opening frame so as to bring the underwater weight of the entire trawl net close to zero. There is no limitation on the material, shape, structure, mounting method, etc. of the float,
Conventionally configured floats can be used as long as they can withstand the water pressure at the target depth.

[0011]

In the trawl net with a dive plate of the present invention, a curved dive plate having excellent dive force characteristics is attached to the trawl net below the opening frame of the trawl net with a hanging cable so as to maintain a constant angle of attack. Even if the speed of the boat changes, the curved submersible plate can maintain the maximum dive force without stalling, and can obtain a stable water depth during operation.

In particular, the trawl net with a dive board of the present invention is characterized in that the curved dive board is maintained at an angle equivalent to a preset elevation angle from a side plate attached to a substantially central portion on the left and right sides of the opening frame, and has a substantially equal length. When the boat is suspended with two hanging ropes on the left and right sides, a total of four hanging ropes are kept substantially parallel during the towing, so even if the boat speed changes, unless the net opening frame is inclined, The dive board can always be kept at the same angle of attack, and the maximum dive power can always be exerted. Particularly in the present invention, the aspect ratio is 6.0, the warpage ratio is 15%,
When using a curved underground plate formed at a dihedral angle of 20 degrees,
Its dive characteristics are almost doubled compared to the conventional one. In the normal case, the trawl cord is attached to the center of both sides of the net opening frame, and the length of the net is designed to be sufficiently large with respect to the height and width of the net opening. It is almost impossible for the mouth frame to tilt.

[0013] The trawl net with a descent plate according to the present invention, as described above, makes the length of the trawl cord substantially equal, and floats the underwater weight of the entire trawl net above the net opening frame to approach zero. When attached, it is possible to control so that the net is always drawn to a constant depth.

Therefore, the trawl net with a dive board according to the present invention is capable of controlling the length of the towed rope and controlling the depth of the dive board at a constant depth while maintaining the maximum dive force irrespective of changes in ship speed or sea conditions. Can be dragged at high speed. Therefore, it is possible to quantitatively collect a sample of a fry of a target fish species at a target water depth under a high-speed running state.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be further described below with reference to the drawings.

[0016]

Embodiment 1 FIG. 1 is a diagram showing an overview of an embodiment of a trawl net with a dive board according to the present invention. In FIG. 1, reference numeral 1 denotes a trawl net (net opening 2.25 m × 2.25 m, length 12 m),
Is a curved underwater plate. The curved underwater plate 2 of the present embodiment includes:
Consists of a vertical wing 21 and horizontal wings 22 projecting on both sides thereof, the horizontal wing 22 has an upwardly curved cross section 23
Wing area 2000cm ² , wing width 244cm, aspect ratio 6.0, warpage ratio 15
%, Formed at a dihedral angle of 20 degrees. In this embodiment, the left and right hanging cables 4, 4 and 4, 4 of approximately the same length are obtained from the side plate 6 in which the curved underground plate 2 is mounted on the left and right central portions of the substantially square mesh opening frame 3. It is suspended at an elevation angle of 20 degrees. Above the mesh opening frame 3, floats 7, 7 having a buoyancy of 35 kg are attached so as to make the underwater weight of the entire trawl net close to zero.

The trawl net with curved submergence plate of the present embodiment has the configuration as described above, and the aspect ratio is 6.0 and the warpage ratio is 1
Since the curved underwater plate 2 formed at 5% and a dihedral angle of 20 degrees is used, as shown in a test example described later, extremely excellent underwater force characteristics can be exhibited. Further, in the trawl net with a dive plate of the present embodiment, a hanging line having a substantially equal length is provided from the side plate 6 in which the curved dive plate 2 is attached to the left and right substantially central portions of the substantially square mesh opening frame 3. 4,4,4,4
Is suspended at an elevation angle of 20 degrees.
Since the hanging ropes 4, 4, 4, 4 of the book are substantially parallel to each other, the descent plate 2 can always be maintained at the elevation angle of 20 degrees defined by the side plate 6 unless the net frame 3 is inclined. .

Further, the trawl net with a dive plate of the present embodiment
Since the floats 7, 7 having a buoyancy of 35 kg are attached above the opening frame 3 of the trawl net 1, the underwater weight of the entire trawl net can be reduced to a state close to zero. be able to.

Therefore, the trawl net with a dive board of the present embodiment can quantitatively analyze a fry sample of a fish species to be harvested at a target water depth at a high speed simply by manipulating the length of the towing line 5 from the ship. Can be collected.

That is, in the trawl net with a dive board of the present embodiment, the dive board 2 always exerts the maximum dive force irrespective of the change of the ship speed or the sea condition only by controlling the length of the towing line 5. , Can seine at a constant depth at high speed.

Hereinafter, the present invention will be further described with reference to Test Examples.

[Test Example 1] Using a 1/5 actual model, a model experiment was conducted in a circulating water tank to measure the dive force characteristics of the dive plate, the drag, and the restoring moment when the curved plate was tilted left and right. That is, wing area 397.7cm ² , wing width 8.12cm, aspect ratio
6.0, using a model dive board with a warpage ratio of 15% and a dihedral angle of 20 degrees,
In the circulating water tank, the dive force and the drag were measured at an angle of attack of 10 to 80 degrees and a flow rate of 30 to 100 cm / sec. Furthermore, the influence on the restoring moment and the dive force when the dive board was tilted left and right by changing the left and right tilt angles to 30 degrees was also measured. In the experiment, high-strength polyethylene made of the same material as the real net (Dyneema)
Using a net (leg length 1.95 mm, mesh thread diameter 0.36 mm), a 1/5 model net was made in the same way as the immersion board, and the above-mentioned curved immersion board model was attached. By changing the flow velocity, the seine water depth of the net was measured.

As a result of the experiment, as shown in FIG. 2, a maximum dive force coefficient of 1.57 was obtained at an angle of attack of 20 degrees. This is approximately twice as large as the maximum dive force coefficient of the conventional flat diving plate for Isaac's kid middle trawl 0.84, and it has been confirmed that the curved diving plate of the present invention has high diving force characteristics. The drag coefficient at this angle of attack is about 0.4. At the angle of attack where the maximum dive force coefficient was obtained, there was almost no effect on the dive force up to an inclination angle of 20 degrees left and right, and it was confirmed that the restoring moment was larger than that of the flat type dive plate.

[0023]

[Test Example 2] A real net of 2.25m x 2.25m and 12m in length
A 1/5 model net is made of the same material as the real net (leg length 1.95m
m, high strength polyethylene with a mesh thread diameter of 0.36 mm), and the model immersion board used in Test Example 1 was attached below the mesh opening frame at an angle of attack of 20 degrees. Buoyancy 75 above the mouth opening frame to approach zero
A 3g float was attached. In this way, in the circulating water tank, the length of the trawl rope is 260 m, 310 cm, 410 m, and the flow velocity is 20 to 90 cm /
The water depth of the net was measured in seconds. FIG. 3 shows the obtained results. From Fig. 3, in the model experiment in the circulating water tank, it was recognized that the longer the length of the trawl cord, the greater the water depth of the net. It was confirmed that the net depth was almost constant. Also, during the experiment, no inclination of the net opening frame was observed even when the flow velocity was high, and the submersible plate could always maintain the set angle of attack.

[0024]

[Test Example 3] In the sea area at a depth of 1000 m of Suruga Bay, a real experiment was conducted on the seine characteristics of the net using the curved underwater plate of Test Example 1. However, no float was attached to the net opening frame to reduce the weight of the net underwater. FIG. 4 shows the results of the towing water depth of the net obtained when the length of the towing rope and the boat speed were changed in the experiment. According to Fig. 4, when the boat speed is 2.09kt, a value equivalent to the length of the towing rope with the towing net depth of about 1/2 is obtained, indicating that the dive board has sufficient dive capacity. I was assured.

[0025]

As described above, according to the trawl net with a dive board of the present invention, a curved dive board having excellent dive force characteristics is maintained at a constant angle of attack below a net opening frame of the trawl net by a hanging cable. , So that the curved underwater plate does not stall even at a change in the speed of the towing net, so that the maximum underwater force can always be maintained, and a stable water depth can be obtained during operation.

In the trawl net with a dive board of the present invention, the curved dive board is maintained at an angle corresponding to a preset elevation angle from a side plate attached to a substantially central portion on the left and right sides of the opening frame, and has a substantially equal length. When hanging with two hanging ropes on the left and right sides of the boat, the total of four hanging ropes are kept substantially parallel during the towing, so that the submergence plate always keeps the same angle of attack even if the ship speed changes And can always exert its maximum dive power. In addition, the trawl net with a submersible plate of the present invention has the length of the trawl cord substantially equal to the length as described above, and a float for attaching the underwater weight of the entire trawl net to near zero above the mouth frame. Sometimes, a constant depth can be dragged.

Therefore, the trawl net with a dive board according to the present invention is capable of controlling the length of the trawl cord and maintaining the maximum dive force at a constant water depth while the dive board always exerts the maximum dive force irrespective of changes in the ship speed or sea conditions. Can be collected at high speed, and a sample of a fry of a target fish species can be collected at a target depth in a high-speed running state. As described above, according to the present invention, it is possible to provide a trawl net apparatus suitable for collecting small-sized floating fish larvae quantitatively at high speed.

[Brief description of the drawings]

FIG. 1 is a schematic view of an embodiment of a trawl net with a dive board according to the present invention.

FIG. 2 is a graph showing a dive force coefficient (filled circle) and a drag coefficient (filled triangle) with respect to the angle of attack of the curved underwater plate according to the present invention.

FIG. 3 is a graph showing the relationship between the towing net depth and the flow velocity at different towing rope lengths of the trawl net with a dive board according to the present invention.

FIG. 4 is a graph showing a change in the depth of the towing net with respect to the length of the towing rope in a real experiment of the trawl net with a dive board according to the present invention.

[Explanation of symbols]

 1: Troll net 2: Curved submersible board 21: Vertical wing of curved submersible board 22: Horizontal wing of curved submersible board 23: Cross section of horizontal wing 3: Net mouth frame 4: Hanging cable 5: Towing cable 6: Side plate 7: Float

Claims (5)

[Claims] 1. A trawl net with a dive plate, wherein the curved dive plate is attached by a hanging cable below a mesh frame of the trawl net so as to maintain a constant angle of attack. 2. The trawl net with a dive plate according to claim 1, wherein a float is provided above the net opening frame so as to reduce the underwater weight of the entire trawl net to zero. 3. The dive according to claim 1, wherein the curved dive board is suspended by two left and right suspension cables of substantially equal length while maintaining an angle corresponding to a preset elevation angle. Troll net with plate. 4. A vertical wing and a horizontal wing extending on both sides of the vertical wing. The horizontal wing has an upwardly curved cross section, and both horizontal wings have the same angle between a wing surface and a horizontal plane. The trawl net with a dive plate according to any one of claims 1 to 3, wherein a curved dive plate joined in such a manner is used. 5. The trawl net with a submerged plate according to claim 1, wherein a curved submerged plate formed with an aspect ratio of 6.0, a warpage ratio of 15%, and a dihedral angle of 20 degrees is used.