JPH0753068B2 - Induction method of baby ayu - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for guiding baby ayu in a river, which has just been hatched from an egg and has a weak swimming power, toward one side of the river.

[0002]

2. Description of the Related Art Ayu is a typical fish that is artificially propagated along with salmon, among fish targeted for fishing in Japanese rivers. Ayu spawns in the middle and lower reaches of the river, and the ayu that hatched from the egg heads down the river to the sea and grows to some extent in the sea before returning to the river. Has also been done.

However, if there is an intake for water or the like in the middle of the river, baby ayu with weak swimming power is taken into this intake due to the flow of the river and cannot go to the sea.
Therefore, if there is an intake in the river for growing ayu,
It is necessary to take measures to prevent baby ayu from being taken into the intake. As a countermeasure, for relatively large fish with swimming ability, a method of returning the fish near the intake side to the opposite side with an electric screen etc. is adopted, but this is the case for baby ayu with weak swimming ability. However, no effective measures could be taken to prevent the ayu from being taken into the intake.

[0004]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the problems of the prior art as described above, and is effective for guiding the baby ayu having a weak swimming power to the opposite bank of the water mouth. The purpose is to provide a method.

[0005]

In order to achieve the above object, the first aspect of the present invention is to irradiate one side of a river with light in a predetermined section in the lengthwise direction of the river so that the sweetfish in the river can be lit. A method for inducing baby ayu, characterized in that the fish is induced along the light toward the one shore. According to a second aspect of the present invention, light is applied to a predetermined section in the lengthwise direction of the river, and the irradiation width of the light in the widthwise direction of the river is biased toward one bank of the river as it goes from the upstream side to the downstream side. Then, there is provided a method for guiding a sweetfish in the river, which comprises guiding the sweetfish in the river toward the one shore side along the light.

According to a third aspect of the present invention, in addition to the features of the first or second aspect, a screen for dividing the water of the river in the width direction is installed in the vicinity of the downstream end of the river where the light is irradiated. Also provided is a method for inducing a sweetfish which is characterized in that the sweetfish in the river is guided toward the one shore even downstream from the terminal end. According to a fourth aspect, in addition to the features of the first to third aspects, the array distance of the light in the length direction of the river is calculated from the width of the river, the flow velocity, and the swimming speed of the baby ayu. Provided is a method for inducing baby ayu.

[0007] The term "ayu (sweetfish)" as used herein means an ayu that has just hatched from an egg and has a body length of about 5 mm. It has a weak swimming power and a swimming speed of about 3 cm / s at the maximum, and is an average for a long time. The swimming speed is estimated to be about 1 cm / s.

[0008]

[Function] The results of examining the change in the number of individuals per day by counting the number of baby ayu in the river for growing ayu per hour are shown in Fig. 1.
As shown in, the results show that ayu (sweetfish) goes down more rivers at night than at daytime. The reason for this is probably because the ayu that has just hatched from an egg has weak physical strength and is likely to die without being able to withstand the ultraviolet rays in the daytime, and it may be because it is active at night when there is almost no ultraviolet ray irradiation.

[0009] Further, although it is said that ayu has a habit of hating light when it becomes an adult fish, as a result of the experiment, it was found that the baby ayu reacts to the light and approaches. That is, using a sodium lamp that emits orange light, the width direction of the river was divided into left and right halves, and only one side was illuminated, and the number of baby ayu present on each side was examined.
The results are shown in FIGS. 2 (a) and 2 (b). In each case, the number of baby ayu on the side illuminated by sodium lamps was quite high.

From these things, according to the method of claim 1, since the light is applied to one bank side of the river in a predetermined section in the length direction of the river, the baby sweetfish in the river is at night. In response to this light, it approaches and heads for the one bank.
Further, according to the method of claim 2, the irradiation width of light in the width direction of the river is biased toward one of the shores of the river toward the downstream side from the upstream side to the downstream side.
At night, it travels underwater along the array of lights and heads for one shore of the river.

Therefore, by setting the one shore side to the opposite bank at a place where it is not desired to direct the ayu such as an intake, when the ayu goes down the river at night, the ayu is directed toward the opposite bank. It is possible to prevent them from being taken into the intake port. According to the method of claim 3, in addition to the methods of claims 1 and 2, a screen is provided in the vicinity of the downstream end of the river where the light is irradiated. As a result, it is possible to prevent the baby sweetfish guided to one shore side from heading to the other shore side.

Since the easiness of the baby ayu flowing to the shore is determined by the width and flow velocity of the river and the swimming speed of the baby ayu, according to the method of claim 4, as shown in FIG. When the light irradiation end point A is set at the upstream end of a place where the sweetfish such as 12 is not desired to be directed, the light irradiation start point B for effectively guiding the baby sweetfish to the opposite bank is known. That is, for example, as shown in FIG. 3, the width of the river is W, the flow velocity is u, the swimming speed of the baby ayu is v, the irradiation distance of light in the length direction of the river is X, and B is
Assuming that light is emitted over the entire width of the river at the point, theoretically, if W / X = v / u (1) is satisfied, the baby ayu is straight line L (point A and point B). The straight line connecting the points on the opposite side of the river) causes the ayu to be easily guided along the light radiated in the river.

[0013]

An embodiment of the method of the present invention will be described below with reference to the drawings. FIG. 4 is a plan view showing a river to which this method is applied. On the right bank of the river 1 where the baby ayu flows down, there is an intake 12 directed to the water 11. Inside the river 1, from the upstream end A ₁ point of the intake 11 to the upstream B ₁ point. In between, a large number of sodium lamps 2 are arranged. That is, in the lengthwise direction of the river, point A on the left bank, position T
Along a straight line L ₁ connecting _A and the point B on the right bank T _B, and straight lines L _{2 to} L ₄ parallel to the straight line L _1, and in the width direction, equal intervals are provided along a line perpendicular to the length direction. Each sodium lamp 2 is installed.

The river 1 has a width of 80 m and a flow velocity of 15 c.
m / s, and the swimming speed of the baby ayu is about 1 cm / s, so here, the array distance X ₁ of the lights in the length direction of the river is calculated from the above formula (1) (X ₁ = (1
5/1) × 80 m = 1200 m), and the B ₁ point was set at a position 1200 m away from the A ₁ point. Since equation (1) is a theoretical value that ignores the influence of wind, etc., the swimming speed of the baby ayu is estimated to be small (for example, v ₁ = 0.5v) and the flow velocity of the river is largely estimated (for example, u ₁ = 1.5u), for example, X = (1.5v / 0.5u) × W may be used to calculate the lamp array distance X ₁ in the river length direction.

As shown in FIG. 5, each of the sodium lamps 2 is to be submerged in a state in which a weight 21 such as a sandbag is attached to the lower side by a mooring line 22a and a float 23 is attached to the upper side by a mooring line 22b. And, it is stably installed at a predetermined height in the water. Power cord 2a of this sodium lamp 2
Is wound around the mooring line 22b, then taken out above the surface of the water via the float 23, and connected to a 100V power source on the left bank. Alternatively, a battery may be placed on the float 23 and connected to it. In addition, each sodium lamp 2 may be installed above the water surface of the river.

Further, in the lengthwise direction of the river 1, a dozen or so screens 3 are arranged near the central portion in the widthwise direction from just before the downstream end of the sodium lamp 2 to near the left bank of the water 11. did. As can be seen from FIGS. 6 (a) and 6 (b), the screen 3 is made of a vertically long plate material and is arranged obliquely with respect to the water flow in a plan view so that the upstream side faces the right bank side and the downstream side faces the left bank side. is there. With this arrangement, the baby ayu can proceed as shown by arrow C while riding on the water flow, for example.

In order to stably install these screens 3 at predetermined positions in the water, a dozen or more screens 3 are used.
Are arranged in series at equal intervals, the upper ends of the screens 3 are connected by the rope material 31, the floats 31 are attached to both ends of the rope material 31, and the lower end portions of the screens 3 are connected by the rope material 33. The ends of the rope 33 are tightly bound so that they will not fray. Further, a rope 34 is applied to the lower end surface of each screen 3 and fixed, and sandbags 35 are attached to both ends of the rope 34.

Therefore, since the ayu (ayu) flowing from the upstream side at night is guided by the light of the sodium lamp 2 from the installation start point B ₁ of the sodium lamp 2 to the end point A ₁ , the ayu of the river 1 is near the intake 12. Down the left bank. In addition, by installing the screen 3, the baby sweetfish that was guided to the left bank, the intake 1
It is possible to prevent heading to the right bank side in the vicinity of 2. As a result, the ayu (sweetfish) can be prevented from being taken into the water port 12 and can be further moved downstream.

Further, in another embodiment of the present invention, as shown in FIG. 7, a sodium lamp 4 can be installed. That is, in this case, as shown in FIG. 8, the base 41 for installing the sodium lamp 4 is fixed to the ground 10 forming the left bank of the river 1, the arm 42 is extended from the base, and the sodium lamp 4 is attached to the tip of the arm 42. It is attached so that the water on the left bank is illuminated by light. A flexible mechanism 43 is provided at the tip of the arm 42 so that the irradiation angle of the sodium lamp 4 with respect to the water surface can be changed. Also, in this example, the illuminance in the river can be easily changed by replacing the sodium lamp 4 used with one having a different wattage.

In this way, a plurality of sodium lamps 4
During the distance X ₂ similar to X ₁ in FIG.
By installing so that the installation interval becomes large from the upstream side to the downstream side, the light from the sodium lamp 4 is made to reach the portion S surrounded by the imaginary line D and the left bank of the water surface of the river 1. . The screen 3 used in the method of the present invention is not limited to the one made of the plate material as described above,
Various things such as a net-like thing are included.

In addition, larvae such as sculpins are expected to come closer in response to light from sodium lamps, and these can be guided in the river in the same manner as the method of the present invention. It is thought to be possible.

[0022]

As described above, according to the present invention, the ability to swim can be utilized by utilizing the habit of baby ayu, that is, going down a river at night and approaching in response to a light. It is possible to provide an effective method for guiding weak ayu to one side of the river. As a result, the baby sweetfish is guided to one side of the river, so that the growing sweetfish can be prevented from being taken into the intake port or the like in the middle of the river.

[Brief description of drawings]

FIG. 1 is a graph showing the results of examining the change over time in the number of baby ayu present in a river.

FIG. 2 is a graph showing the results of examining whether or not baby ayu reacts to sodium lamp.

FIG. 3 is an explanatory diagram for explaining an example of the method of claim 4;

FIG. 4 is a plan view showing a river to which the method according to the embodiment of the present invention is applied.

FIG. 5 is an explanatory diagram showing a method of installing each sodium lamp in a river in this embodiment.

6A and 6B are a perspective view and a plan view showing a method of installing a screen in this embodiment.

FIG. 7 is a plan view showing a river to which another embodiment of the present invention is applied.

FIG. 8 is a cross-sectional view showing how to install each sodium lamp in FIG.

[Explanation of symbols]

 1 river 2 sodium lamp 3 screen 4 sodium lamp

Claims (4)

[Claims] 1. A method of irradiating one bank side of a river with light in a predetermined section in the length direction of the river, and guiding baby ayu in the river toward the one bank side along the light. A method for inducing baby ayu characterized by. 2. The light is irradiated to a predetermined section in the length direction of the river, and the irradiation width of the light in the width direction of the river is deviated to one shore side of the river from the upstream side to the downstream side to be small. Then, the method for inducing a sweetfish in the river is characterized by guiding the sweetfish in the river toward the one bank along the light. 3. A screen for partitioning the water of the river in the width direction is installed in the vicinity of the downstream end of the river where the light is irradiated, and the inside of the river is also downstream from the end. 3. The method for inducing ayu (sweetfish) according to claim 1, wherein said ayu (sweetfish) is guided toward the one bank. 4. The irradiation distance of the light in the lengthwise direction of the river is calculated from the width and flow velocity of the river and the swimming speed of the baby ayu. The method for inducing baby ayu according to.