JP2008187910A - Net-shaped configuration for aquaculture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress generation of adhesive aquatic lives, such as algae and shellfish on a net basket, or a fishing net placed in seawater or fresh water for culturing or preserving living aquatic resources. <P>SOLUTION: A conductive material having a titanium oxide photocatalyst layer on the surface is used for making at least a part of a net basket 1 or net baskets. A counter electrode 3, provided electrically connected to the conductive material via an external circuit 4, is short-circuited to the conductive material in water. The effect for preventing generation of adhesive aquatic lives by the titanium oxide photocatalyst layer is reinforced by combining with the counter electrode 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an aquaculture net-like structure such as a net cage installed in seawater or fresh water for culturing or raising aquatic products, a fishing net for a cage, and a stationary net, and more specifically, algae attached to and propagate on these The present invention relates to a net structure for aquaculture that can effectively suppress the occurrence of sticky aquatic organisms such as shellfish.

  Oyster culture is one of the typical marine products. In this oyster culture, instead of the traditional drooping method, a netting method has been developed, a test for practical application has been promoted, and some have already been put into practical use. In the cultivation of oysters using a net cage, a plurality of oyster shells are put together in a net cage and hung from the sea bream floating on the sea surface to grow in the sea. Although the method using the net cage is more time-consuming than the drooping series, switching from the drooping series is being promoted because of the advantages such as the ability to produce high quality single oysters and the absence of environmental impact due to falling.

  At the beginning of aquaculture, oysters are small, and it is necessary to use small nets. However, in aquaculture with a net cage, a large amount of algae, shellfish, etc. adhere to the net cage in a short period of time, causing clogging. When clogging occurs, the distribution of seawater is hindered, and there is a risk that the oysters in the nets will die or become poorly grown. For this reason, it is necessary to frequently perform a cleaning operation such as lifting the net cage to remove the attached aquatic organisms such as algae and shellfish, and the burden required for the cleaning operation becomes enormous.

  In view of this, a method of increasing the mesh size of the mesh net step by step with the growth of the oysters to reduce the labor of cleaning. However, this method requires a new oyster replacement work. For this reason, the actual situation is that the total man-hours and work costs do not change so much.

  Under such circumstances, in the cultivation of oysters using netting, it is also considered to control the depth of the netting so that the netting is not exposed to sunlight, and the alga is not easily generated. However, in such a deep place, there is a problem that the growth of oysters is delayed because there are few planktons that feed oysters. The problem of seawater distribution obstruction due to the adhesion of algae and the like has been pointed out in fishing nets and the like that make up fish cages for fish farming, and in order to remove algae attached to the fishing nets, Even things like diving in are being done.

  In order to solve the problem of adhesion of algae and the like in aquaculture nets and fishing nets, for example, it is considered to coat a photocatalyst layer made of titanium oxide on a conductive net. In addition, an electrochemical algae prevention method in which a counter electrode is combined with a conductive net and a voltage is applied between the two in seawater has been proposed (Patent Documents 1 and 2).

JP 2003-155583 A JP 2003-235402 A

  The mechanism of algae prevention by the titanium oxide photocatalyst is considered as follows. It is believed that the oxidizing power of the titanium oxide photocatalyst causes inactivation of adherent cells and decomposition of adhesive substances, resulting in weak adhesion of algae and the like, and an excellent anti-algae function. However, in order to exert its effectiveness, sunlight as strong as possible is necessary, and for this reason, nets or the like must be installed in a shallow place where the sunlight hits well. However, such a place is suitable for the growth of algae and the like on the one hand as described above, and since this counteracts the anti-algal function of the titanium oxide photocatalyst, it does not provide the expected anti-algae effect. is there.

  On the other hand, the electrochemical algae control method requires a large amount of incidental equipment such as a power source, and there is a problem that the equipment cost increases.

  The object of the present invention is to reduce the occurrence of aquatic organisms in spite of the fact that they are installed in shallow water where the occurrence and growth of adherent aquatic organisms such as algae and shellfish that hinder the cultivation or livestock of marine products. The object is to provide a net structure for aquaculture that can be effectively prevented by cost.

  In order to achieve the above object, the present inventor considered that the use of a titanium oxide photocatalyst was indispensable, and conducted extensive experiments on a method for enhancing its function. As a result, it was concluded that it is effective to combine a counter electrode electrically connected to the titanium oxide photocatalyst.

That is, when the generation of algae on the surface of a metal material that is immersed in water and receives light is prevented by the titanium oxide photocatalyst, the surface of the metal material is coated with a titanium oxide photocatalyst, usually a TiO ₂ film. Although it is true that the generation of algae can be suppressed by coating with a titanium oxide photocatalyst compared to the case without coating, the period until the generation of algae can be extended, and the generation can be prevented over a long period of time. It is difficult to do. However, when a counter electrode electrically connected to a metal material by an external circuit is immersed in water together with the metal material and the two are connected and short-circuited through the water, the algae that become an obstacle to aquaculture can be used in the same operating environment. Even if the generation can be almost completely prevented or cannot be completely prevented, the period until these algae start to occur can be greatly extended, and the growth rate can be greatly suppressed.

  The aquaculture net structure of the present invention has been completed on the basis of such knowledge, and is provided in seawater or fresh water for aquaculture or animal breeding and is composed of a net material for aquaculture. In the body, at least a part of the mesh material is composed of a conductive material having a titanium oxide photocatalyst layer on the surface, and a counter electrode electrically connected to the conductive material via an external circuit is the seawater or The antifouling effect of the titanium oxide photocatalyst layer by receiving light is remarkably enhanced by combining the counter electrode.

  Specifically, the aquaculture net-like structure of the present invention is a fish net constituting a fish cage for cultivating or raising fishery products or shellfish, or a net suspended in water for culturing fishery products or shellfish. Idempotent. These reticulated structures are installed in shallow places under the sun. The reticulated material constituting these reticulated structures is at least partially, preferably entirely or substantially entirely composed of a conductive material, and a titanium oxide photocatalyst layer is provided on a part of the conductive material, preferably the entire surface. . And the counter electrode electrically connected via the external circuit is combined with the electroconductive material in which the titanium oxide photocatalyst layer was provided in the surface. The counter electrode is installed in the water together with the conductive material, and is preferably installed at a position close to the conductive material, and both are electrically short-circuited in the water.

  By using such a counter electrode, the effect of preventing the propagation of adherent aquatic organisms by the titanium oxide photocatalyst layer, for example, the anti-algae effect, is remarkably enhanced with no power supply as compared with the case where the counter electrode is not used. Further, if the external circuit is provided with a power source through which current flows from the counter electrode to the conductive material, the effect of the titanium oxide photocatalyst layer is further enhanced.

  The reason why the effect of the titanium oxide photocatalyst layer is enhanced in the aquaculture net structure of the present invention is considered as follows. When the counter electrode does not exist, that is, when only the titanium oxide photocatalyst layer is present, the anode and the cathode are mixed in various parts of the titanium oxide photocatalyst layer, but the cathode and the anode are separated by combining the counter electrode, and the positive cathode current (the anode side) Current flows at a potential at which the current of the cathode and the current on the cathode side are equal. As a result, the electrode potential can be easily controlled by changing the electrode surface area ratio, mass transfer by stirring, and the like, and by generating a current corresponding to the potential, it is possible to enhance the effect of preventing the growth of adherent aquatic organisms. If a power source is further added from this state, the electrode potential can be forcibly changed, and the effect of preventing reproduction can be further improved by increasing the cathode current due to the potential difference.

  As the material of the counter electrode, carbon, copper-based metal (copper or copper alloy), various steels, and the like can be used, but carbon is particularly preferable because it has a large energization amount and a high reproduction preventing effect. Further, the reticulated material includes not only an original net but also expanded metal, punching metal and the like. In short, it may be a perforated material with excellent flowability of seawater or fresh water. The conductive material on which the titanium oxide photocatalyst layer is provided is not particularly limited in terms of material and form. It may be a conductive film, a plate, a coating film, a fiber, a porous body, or the like. In the case of fibers and porous bodies, a photocatalyst layer can be provided not only on the exposed surface but also on the inside.

  The light applied to the titanium oxide photocatalyst layer may be not only sunlight but also illumination light.

  The aquaculture network structure of the present invention comprises at least a part of a mesh material as a conductive material, a titanium oxide photocatalyst layer on the surface thereof, and a counter electrode connected to the conductive material through an external circuit in water. Combining with a conductive material so as to short-circuit can remarkably enhance the effect of preventing the growth of adherent aquatic organisms such as algae by a titanium oxide photocatalyst, and the effort and cost required to remove the attached aquatic organisms Can be greatly reduced. Further, since the effect can be obtained with no power source or a simple power source, it is excellent in economic efficiency, and if a separate power source is used, the effect of preventing reproduction can be further enhanced. Furthermore, since sunlight is effective and the effect is exerted in shallow water rich in plankton, it is possible to avoid a problem of a decrease in aquaculture efficiency that is problematic when installed in deep water.

  That is, the aquaculture reticulated structure of the present invention effectively and economically prevents only the breeding of adherent aquatic organisms in shallow water that is suitable for aquaculture and in which the breeding of adherent aquatic organisms is remarkable.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an aquaculture net-like structure showing an embodiment of the present invention.

  The net structure for aquaculture of this embodiment is a metal net 1 used for oyster culture. The mesh cage 1 uses a metal mesh (including expanded metal) excellent in corrosion resistance, such as Ti, as a mesh material, and here is formed by forming it into a quadrangular pyramid cage shape. The net cage 1 can open and close at least one of four triangular sides for taking in and out of oyster shells.

A titanium oxide photocatalyst layer made of TiO ₂ is provided on the surface of the metal net constituting the net cage 1, more specifically, the surface of the metal wire constituting the metal net. The mesh of the metal net is set according to its size so that it can accommodate the oyster shell to be grown.

  The quadrangular pyramid net 1 is suspended in the sea by an insulating hanging wire 2 made of an insulating wire such as a nylon rope and submerged to a predetermined depth. Equipped with a suspended counter electrode 3. The counter electrode 3 is made of, for example, a graphite plate (carbon electrode), and is suspended and supported at a substantially central position in the cage by a covered conductive wire 4 that also serves as a wire for suspension. The insulative hanging wire 2 that suspends the net 1 is suspended downward from the top of the net 1 through the inside of the net in order to hang the net 1 in multiple stages.

  The covered conductive wire 4 is a support member that suspends and supports the counter electrode 3, and at the same time, an external circuit that is electrically connected to the metal mesh constituting the mesh cage 1 and electrically connects the metal mesh and the counter electrode 3. It is composed. The coated conductor 4 has a structure in which a conductive core material such as Ti having excellent corrosion resistance is coated with an insulating material, and the purpose of the coating is to conduct only the counter electrode 3 with the metal net in seawater, and an external circuit passes seawater. It is to prevent a conductive short circuit with the metal net.

  Next, the usage method and function of the aquaculture net structure of the present embodiment will be described.

  The oyster to be grown is put in the net cage 1 so as not to interfere with the counter electrode 3. One or a plurality of the net cages 1 are connected in series, suspended from the ocean cage and submerged. The depth of sinking shall be a level at which sunlight hits well.

  In shallow places in the sea, sunlight hits well and there are many plankton, which is suitable for the growth of oysters. On the other hand, the growth of algae in the net 1 is also remarkable. However, a titanium oxide photocatalyst layer is coated on the surface of the wire rod of the metal net constituting the net cage 1, and the net cage 1 is electrically connected by the coated conductor 4 and is short-circuited via seawater. It is combined. For this reason, the formation of a photoelectrochemical cell and the enhancement of the algae-preventing effect by the titanium oxide photocatalyst enhance the growth of the algae, and further the propagation of shellfish etc. Is effectively suppressed. The detailed reason for this is as described above.

  As a result, in the net cage 1, sufficient circulation of seawater is ensured over a long period of time without maintenance, and fresh seawater continues to be supplied. Moreover, the seawater is rich in plankton, which is a food for oysters. For this reason, oysters can be grown at a low cost in a short period of time, and the production cost can be significantly reduced in terms of both work cost and culture period.

  FIG. 2 is a schematic configuration diagram of an aquaculture net-like structure showing another embodiment of the present invention. The net structure for aquaculture of this embodiment is also a metal net 1 used for oyster culture.

  The reed 1 is composed of a metal titanium wire as in the above-described embodiment, and the shape is a rectangular box unlike the above-described embodiment. This box body is hung at the four corners by four conductive hanging wires 6 made of coated conductive wires, and the four conductive hanging wires 6 are bound at the tip, and the tip of the box is one insulating hanging wire 2. It is designed to be hung by. The insulative hanging wire 2 hangs down from the top of the net cage 1 through the inside of the cage to hang the mesh cage 1 in multiple stages. The counter electrode 3 is suspended in the mesh cage 1 by the covered conducting wire 4 from the bundling portion of the four conductive hanging wires 6. The counter electrode 3 is electrically connected to the reed 1 through the covered conductor 4 and the four conductive hanging wires 6.

  In seawater, the counter electrode 3 is electrically connected to the reed 1 through the seawater. This enhances the anti-algae effect of the photocatalyst layer on the surface of the net cage 1 as in the previous embodiment. Although the upper surface of the net 1 is open in this embodiment, it can also be covered with a metal net.

  FIG. 3 is a schematic configuration diagram of an aquaculture net-like structure showing still another embodiment of the present invention. The net structure for aquaculture of this embodiment is also a metal net 1 used for oyster culture.

  The basic structure is the same as that of the network structure in FIG. 2 is that a part of the covered conductor 4 which is an external circuit is exposed to the sea, and a power source 5 is interposed therein. The power source 5 has a polarity through which a current flows from the counter electrode 3 to the net 1 and is preferably used from the viewpoint of cost and the like using a solar cell because the place of use is at sea. As described above, the use of the power source 5 further enhances the anti-algae effect of the photocatalyst layer on the surface of the net cage 1.

  The embodiment described above is a net cage for oyster culture, and the shape thereof is a square box type such as a square pyramid, a cube, and a rectangular parallelepiped, but other shapes may be used, and the shape is not particularly limited. Moreover, although the material of this net is a metal net (including expanded metal) as the name suggests, it may be composed of punching metal or the like, and the material is not limited. Ti is used as the material, but stainless steel or the like may be used, and the type is not particularly limited as long as the corrosion resistance is not a problem.

  The embodiment described above is also a net for raising oysters, but it may be a fishing net for constructing a cage in the sea. Because fishing nets for sacrifice are installed near the sea surface, algae breeding, clogging due to this, and the resulting deformation and breakage due to increased resistance have become a major problem. Although work is indispensable, the employment of the present invention can greatly reduce these work, and the cost merit is great. By the way, fishing nets for fishing rods are installed in the sea by suspending them at one corner or several places in the middle and hanging them on the rod with ropes.

  In order to verify the effect of the present invention, the following comparative test was conducted. Assuming a net-like structure for seafood or crustacean aquaculture or livestock raising, a cubic net cage having an open top with a side of 300 mm as shown in FIG. 2 was prepared. The mesh cage is made of expanded metal manufactured from a metal titanium plate, the wire rod width is 0.5 mm, the mesh is a rhombus with a 1.8-3.0 mm length and a 2.2-4.5 mm width. .

Four such screens were prepared, and the first screen was used as it was. In the second screen, the surface of the metal titanium wire constituting the second mesh was covered with TiO ₂ which is a titanium oxide photocatalyst. The third mesh rod is coated with TiO ₂ on the surface of the titanium metal wire, and the carbon electrode as a counter electrode is suspended in the cage by one coated conductor and four conductive suspension wires. Connected to. The fourth netting is the same as that of the third netting, with a part of the covered conducting wire drawn out to the sea and a solar power generation device and a storage battery provided in this part so that current can always be supplied from the counter electrode to the netting ( (See FIG. 3).

  These four types of netting are submerged using insulating hanging wires from the beginning of July, when algae generation and adhesion are expected to occur, to the same depth within the reach of the sun in the sea. The state of shellfish adhesion was investigated. The survey results are as follows.

  Algae was observed on the surface of the first net cage one month after the start of the survey. Algae was observed on the surface of the second net cage 1.5 months after the start of the survey. In contrast, in the third net cage, the attachment of algae to the surface was observed 3.5 months after the start of the survey. In the fourth net, no algae adhered to the surface even after 6 months from the start of the survey.

It is a schematic block diagram of the net-like structure body for aquaculture which shows one Embodiment of this invention. It is a schematic block diagram of the reticulated structure for aquaculture which shows another embodiment of this invention. It is a schematic block diagram of the aquaculture net | network structure which shows another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Net fence 2 Insulating hanging wire 3 Counter electrode 4 Coated conductor (external circuit)
5 Power supply 6 Conductive hanging wire (coated wire)

Claims (5)

  In the aquaculture network structure constructed in a seawater or fresh water for culturing or raising marine products and composed of a mesh material, at least a part of the mesh material has a titanium oxide photocatalyst layer on the surface. The counter electrode electrically connected to the conductive material through an external circuit is provided so as to be short-circuited by the seawater or fresh water, and the titanium oxide photocatalyst layer receives light, thereby providing an antifouling effect. An aquaculture net structure characterized by exhibiting   The aquaculture reticulated structure according to claim 1, wherein the external circuit includes a power source that passes a current from the counter electrode toward the conductive member.   The net structure for aquaculture according to claim 1, wherein the counter electrode is carbon, copper-based metal, or steel.   The net structure for aquaculture according to claim 1, wherein the antifouling effect is an adhesion preventing effect of adherent aquatic organisms including an algae preventing effect.   2. The net-like structure for aquaculture according to claim 1, which is a fishing net constituting a cage for culturing or raising fishery products or shellfish, or a fishnet suspended in water for culturing fishery products or shellfish. .

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