Coral settlement nets, installation methods for coral settlement nets

Abstract

To provide a coral settlement net and a method for installing the net, which can realize the natural spreading of coral over a wide area without collecting or transplanting coral seedlings, by a simple, inexpensive structure with a low environmental load. [Solution] The coral growth net 1 is a metallic coral growth net for growing corals, and comprises a metallic wire mesh body 10 having mesh holes 12, and a strip-shaped metal body 20 that passes through the mesh holes 12 of the wire mesh body 10 and extends alternately to one side and the other side of the wire mesh body 10.

Description

[Technical Field]

[0001] The present disclosure relates to a coral settlement net and a method for installing the coral settlement net. [Background technology]

[0002] Currently, areas where coral restoration is desired include the Coral Triangle, which stretches across the Philippines, Malaysia, Indonesia, East Timor, Papua New Guinea, and the Solomon Islands. In this Coral Triangle, seafood caught in coral reef areas is a food source for local residents and an important marine industry for the country. Furthermore, the benefits of coral reefs have a significant impact on the revenue of the region's tourism industry.

[0003] In the Coral Triangle, coral reefs are declining due to destruction caused by dynamite fishing and by larger typhoons due to climate change, while fine sediment from land caused by deforestation and other factors has made the waters turbid, hindering coral growth. For this reason, these areas are desperately looking to restore coral. Furthermore, low-cost, simple coral restoration techniques that can be implemented locally are needed.

[0004] Coral restoration requires low costs that can be sustainably achieved locally, simple methods that anyone can implement, a simple structure, lightweight construction to reduce transportation costs, and reduced environmental impact by limiting carbon dioxide emissions.

[0005] Traditionally, corals have been grown locally using methods such as transplanting coral fragments, fixing them with underwater bonds, and using transplanting jigs. These methods are now being applied to coral aquaculture, and traditional coral regeneration has mainly relied on transplantation (plantation). This method has many unresolved issues, including the loss of genetic diversity caused by transplanting large numbers of a specific type of coral, the impact on the marine environment caused by the leaching of organic matter from the underwater bonds typically used for transplantation, and the decline of donor corals due to the harvesting of transplanted corals.

[0006] Therefore, there is a desire for coral to grow and regenerate more naturally, without relying on aquaculture. However, there are few cases where natural coral reefs have been efficiently restored on a large scale. Patent Document 1 discloses an invention for an artificial coral implantation reef, which is a technology for implanting coral onto artificial structures. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-154471 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the technology disclosed in Patent Document 1 is relatively expensive because it uses a fired porous ceramic body, and further cost reduction is necessary to expand its application. Also, the technology disclosed in Patent Document 1 requires complicated underwater work, such as setting up a floating artificial coral settlement reef in the sea, attaching and cultivating corals, and then fastening it to the seabed with bolts.

[0009] In areas where there are few professional divers skilled in underwater work, divers involved in the fishing and tourism industries will be required to carry out the work, so simple methods are required.It is also necessary to keep costs low to lead to sustainable restoration and conservation.

[0010] The object of the present disclosure is to provide a coral settlement net and a method for installing the coral settlement net that can achieve the natural spread of coral over a wide area without the need for coral seedling collection or transplantation, using a simple, inexpensive structure that places a low burden on the environment. [Means for solving the problem]

[0011] The present disclosure solves the above-mentioned problems by the following means: For ease of understanding, the following description will be given with reference numerals corresponding to the embodiments of the present disclosure, but the present disclosure is not limited to these.

[0012] The first disclosure is, for example, as shown in Figures 1 and 2, a metallic coral-growth net (1) for growing corals, comprising a metallic wire mesh body (10) having mesh holes (12), and strip-shaped metal bodies (20) passing through the mesh holes (12) of the wire mesh body (10) and extending alternately to one side and the other side of the wire mesh body (10).

[0013] The second disclosure is a coral-growth net (1) described in the first disclosure, characterized in that the metal material constituting the strip-shaped metal body (20) has a more negative ionization tendency than the metal material of the wire mesh main body (10).

[0014] The third disclosure is a coral-growth net (1) described in the first disclosure, characterized in that the metal material constituting the strip-shaped metal body (20) has a more positive ionization tendency than the metal material of the wire mesh main body (10).

[0015] The fourth disclosure is a coral-growth net (1) described in the first disclosure, characterized in that the band-shaped metal body (20) is provided with both a first band-shaped metal body (20) made of a metal material having a more negative ionization tendency than the metal material of the wire mesh main body (10), and a second band-shaped metal body (20) made of a metal material having a more positive ionization tendency than the metal material of the wire mesh main body (10).

[0016] The fifth disclosure is a method for installing a coral growth net (1) described in any one of the first to fourth disclosures, for example, as shown in Figure 3, in which the coral growth net (1) is installed in the sea in a state in which the coral growth net (1) is bent so that multiple convex portions (1a) that convex toward one side of the coral growth net (1) and multiple concave portions (1b) that convex toward the other side of the coral growth net (1) are lined up along the extension direction of the strip-shaped metal body (20).

[0017] The sixth disclosure is a method for installing a coral adhesion net (1), which combines the coral adhesion net (1) described in the second disclosure with the coral adhesion net (1) described in the third disclosure and installs it underwater. [Effects of the Invention]

[0018] According to the present disclosure, it is possible to provide a coral settlement net and a method for installing the coral settlement net that can achieve the natural spread of coral over a wide area without the need for coral seedling collection or transplantation, using a simple, inexpensive structure that places a low burden on the environment. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 illustrates a first embodiment of a coral growth net according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of the coral settlement net taken along the arrow AA in FIG. 1. [Figure 3] FIG. 1 is a cross-sectional view showing a state in which a coral settlement net is installed on the seabed. [Figure 4] FIG. 2 is a diagram showing the results of an experiment in which coral growth was confirmed using the coral growth net of the first embodiment. [Figure 5] 10 is a diagram showing the results of an experiment comparing the difference in coverage of calcareous algae between the front and back of the metal strip 20. FIG. [Figure 6] 10 is a diagram showing the results of an experiment comparing the difference in the number of coral growths (number of new recruits) on the front and back of the band-shaped metal body 20. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0021] (First embodiment) FIG. 1 is a diagram showing a first embodiment of a coral-growth net according to the present disclosure. FIG. 2 is a cross-sectional view of the coral-growth net cut at the position of arrow AA in FIG. 1. Note that the figures shown below, including FIGS. 1 and 2, are schematic diagrams, and the size and shape of each part are exaggerated or omitted as appropriate for ease of understanding. In addition, the following explanation will be given using specific numerical values, shapes, materials, etc., but these can be changed as appropriate.

[0022] The coral growth net 1 in this embodiment is a mesh-like member that promotes the growth and development of corals simply by being placed in the sea, without the need for artificially attaching corals. Furthermore, the coral growth net 1 has the effect of trapping coral fragments placed underneath it or coral fragments that have washed up naturally, preventing these corals from being washed away by waves and allowing them to settle and grow on the coral growth net 1. The coral growth net 1 is composed of a wire mesh main body 10 and a strip-shaped metal body 20 combined together.

[0023] The wire mesh body 10 is made of a wire-shaped metal material, and can be, for example, a metal wire mesh that has been widely used in the past. In this embodiment, an iron wire mesh known as a chicken net, which is available at low cost on the market, is used. The wire mesh body 10 includes wire portions 11 formed of a metal material (iron in this embodiment) and meshes 12 surrounded by the wire portions 11. In this embodiment, the meshes 12 are hexagonal. Note that the shape of the meshes 12 is not limited to a hexagon and may be, for example, a square, and can be selected as appropriate. The wire diameter of the wire portions 11 can be selected as appropriate, but is preferably, for example, 0.2 mm or more and 2.0 mm or less, because this facilitates the deformation process (described below) of deforming the coral growth net 1 into a wavy shape. Regarding the size of the meshes 12, for example, the pitch of the wire portions 11 is preferably 10 mm or more and 50 mm or less, so that the strip-shaped metal body 20 (described below) can be easily passed through. In this embodiment, a commercially available wire mesh known as "chicken net" is used, with a wire diameter of 1.1 mm and a pitch of 20 mm for the wire portions 11. The wire mesh body 10 may be made of zinc-plated iron. Corrosion can also be prevented by applying paint containing zinc or a biodegradable material. Although the lifespan of the material itself will be extended, it is best to use the material according to the purpose.

[0024] In the first embodiment, the wire mesh main body 10 can be made of, for example, stainless steel, but in this embodiment, as will be described later, the metal material of the strip-shaped metal body 20 has a more negative ionization tendency (positive potential) than the metal material of the wire mesh main body 10. Therefore, if the wire mesh main body 10 is made of stainless steel in the first embodiment, it is preferable to use a metal material for the strip-shaped metal body 20 that has a more negative ionization tendency (positive potential) than stainless steel. Examples of such metals include silver, platinum, and gold.

[0025] The metal strip 20 passes through (penetrates) the meshes 12 of the wire mesh main body 10 and extends alternately to one side and the other side of the wire mesh main body 10. In the following description, the one side and the other side will be referred to as the front and the back, respectively, for convenience, but this does not limit the orientation. The metal strip 20 does not need to be arranged (extend) alternately to the front and the back of adjacent meshes 12. That is, a metal strip 20 extending through a mesh 12 (temporarily referred to as a "first mesh 12a") to the back side may extend along the back side of multiple meshes 12, and then extend to the front side through a mesh 12 (temporarily referred to as a "second mesh 12b") that is positioned away from the first mesh 12a, with several meshes 12 in between. The number of meshes 12 between the first mesh 12a and the second mesh 12b is not particularly limited. In the example shown in Fig. 1, the number of meshes 12 between the first mesh 12a and the second mesh 12b is either one or three. The number of meshes 12 between the first mesh 12a and the second mesh 12b may be mixed as shown in Fig. 1, or may all be the same number.

[0026] In the present disclosure, the metals constituting the wire mesh main body 10 and the band-shaped metal body 20 are dissimilar metals to control corrosion of the coral-growth net. More specifically, the corrosion of the coral-growth net is controlled by the difference in ionization tendency between the metals constituting the wire mesh main body 10 and the band-shaped metal body 20. The metal material constituting the band-shaped metal body 20 in the first embodiment has a more negative ionization tendency than the metal material of the wire mesh main body 10. That is, in this embodiment, the metal material constituting the wire mesh main body 10 is iron, and the band-shaped metal body 20 is made of stainless steel, which is a metal with a less negative ionization tendency (more negative) than iron. Specifically, SUS304 stainless steel is used for the band-shaped metal body 20 in this embodiment. Note that the band-shaped metal body 20 used in the first embodiment is not limited to stainless steel, and any metal material with a more negative ionization tendency than the iron of the wire mesh main body 10, such as lead or copper, can be used as appropriate. Furthermore, it is desirable that the metal material constituting the metal strip 20 can be easily plastically deformed manually by the deformation operation described below.

[0027] Because the metal material constituting the strip-shaped metal body 20 has a more negative ionization tendency than the metal material of the wire mesh main body 10, the strip-shaped metal body 20 has a higher potential than the wire mesh main body 10 and is less likely to ionize, i.e., the strip-shaped metal body 20 is less likely to corrode and the wire mesh main body 10 is more likely to corrode. This effect will be described later. Note that a negative ionization tendency refers to a small ionization tendency, and the potential is positive. Also, a positive ionization tendency refers to a large ionization tendency, and the potential is negative. In the specification and claims of this application, a small ionization tendency is described as a "negative ionization tendency," and a large ionization tendency is described as a "positive ionization tendency."

[0028] The shape of the band-shaped metal body 20 used in the first embodiment may also be selected as appropriate, but it is desirable to set the thickness to, for example, 0.2 mm or more and 1 mm or less, as this facilitates the deformation process (described below) of deforming the coral-growth net 1 into a wavy shape. Furthermore, the width of the band-shaped metal body 20 is not particularly limited as long as it is wide enough to penetrate the mesh 12 of the wire mesh main body 10. However, in order to promote coral growth, it is desirable that the width of the band-shaped metal body 20 be 8 mm or more. In this embodiment, the band-shaped metal body 20 is constructed using stainless steel with a thickness of 0.3 mm and a width of 10 mm.

[0029] Next, a method for installing the coral growth net 1 of this embodiment will be described. Fig. 3 is a cross-sectional view showing the state in which the coral growth net is installed on the seabed. The cross section in Fig. 3 is shown cut in a direction along the extension direction of the band-shaped metal body 20. Note that in Fig. 3, the coral growth net 1 is shown simply as a single line, and detailed illustration of the wire mesh main body 10 and the band-shaped metal body 20 is omitted.

[0030] The coral growth net 1 is installed in the sea in a bent state such that multiple convex portions 1a that are convex on one side (e.g., the front side) of the coral growth net 1 and multiple concave portions 1b that are convex on the other side (e.g., the back side) of the coral growth net 1 are lined up along the extending direction of the band-shaped metal body 20. In other words, the coral growth net 1 is installed on the seabed G in a shape that is repeatedly bent in a roughly wave-like shape along the extending direction of the band-shaped metal body 20, as shown in Figure 3.

[0031] Although the wire mesh main body 10 alone can be deformed into a desired shape over a certain period of time, it often returns to a generally flat shape after a while. Furthermore, the shape is easily distorted by the influence of waves, tidal currents, etc. On the other hand, the coral-growth net 1 of this embodiment is provided with the band-shaped metal body 20, which allows the band-shaped metal body 20 to maintain a desired bent shape, thereby enabling the entire coral-growth net 1 to maintain its bent shape.

[0032] The coral growth net 1 of this embodiment is installed on the seabed to promote natural coral growth. Furthermore, the coral growth net 1 traps coral fragments placed underneath it or those that have naturally washed ashore, preventing them from being washed away by waves and allowing the corals to settle and grow on the coral growth net 1. However, simply installing the net on the seabed, etc., may result in many portions being buried in silt, sand, gravel, etc. (hereinafter simply referred to as gravel). Once buried in gravel, coral growth is virtually impossible in those areas. The coral growth net 1 of this embodiment is installed on the seabed G in a shape that is repeatedly bent in a roughly wave-like shape, as shown in FIG. 3 . Therefore, even if the recessed portions 1b are buried in gravel G1, most portions, including the protruding portions 1a, can be prevented from being buried in gravel G1. Furthermore, as described above, the band-shaped metal body 20 maintains the desired bent shape, allowing the net to maintain a condition favorable for coral growth for a long period of time.

[0033] The above-mentioned deformation work, i.e., the work of deforming the coral growth net 1 into a shape with repeated bends in a roughly wave-like shape along the extending direction of the band-shaped metal body 20, may be performed on land or on a ship, or may be performed by a worker underwater. When the deformation work is performed underwater by a worker, the work can be performed more flexibly according to the conditions of the seabed.

[0034] Furthermore, since the coral growth net 1 includes the wire mesh main body 10, it can fulfill additional functions in addition to the natural coral growth described above. Corals growing naturally in natural environments can sometimes be broken by waves or other factors and deposited on the seabed. If left as is, such coral fragments are easily moved by waves and currents, making regeneration difficult. Therefore, conventional practice is to secure broken coral fragments with wire mesh or other means to anchor the coral fragments and promote stabilization. The coral growth net 1 of this embodiment can also be used to anchor these coral fragments. In this case, in addition to the effect of natural coral growth described above, the effect of anchoring using the coral fragments can also be obtained. Moreover, since the coral fragments are placed adjacent to the coral growth net 1, the effect of natural coral growth described above can be expected to be enhanced.

[0035] Next, we will explain the results of an experiment in which coral growth was confirmed using the coral-growth net 1 of the first embodiment. Figure 4 shows the results of an experiment in which coral growth was confirmed using the coral-growth net of the first embodiment. In the experiment, the coral-growth net 1 of the first embodiment described above was deformed into a corrugated shape and installed in the sea, and the number of coral individuals was counted multiple times over a period of two years and three months. No coral was transplanted onto the coral-growth net 1; at the time of installation, only the wire mesh main body 10 and the strip-shaped metal body 20 were attached. As a comparative example, the number of coral individuals was also counted on natural ground where the coral-growth net 1 was not installed. As shown in Figure 4, it was confirmed that by using the coral-growth net 1 of the first embodiment, coral naturally grew and the number of individuals gradually increased.

[0036] The reason why the coral growth was effectively promoted by the coral growth net 1 of this embodiment in the above experimental results will be explained. The underside of the band-shaped metal body 20 (the side of the seabed that is not exposed to sunlight: the side facing the Earth) is more effective in attracting corals than the upper side of the band-shaped metal body 20 (the side exposed to sunlight). This is because coral growth is attracted by "calcareous algae," which are a type of algae but not coral. The corals that grow on the band-shaped metal body 20 will eventually grow on the metal mesh net as well.

[0037] Calcareous algae have the property of easily growing in areas with relatively low light. Therefore, the area where calcareous algae are most likely to attach is "one side (back side) of the metal strip 20 facing the seabed where the amount of light is low." Furthermore, this side (back side) of the metal strip 20 facing the seabed where the amount of light is low makes it difficult for other algae to attach. Therefore, calcareous algae are relatively dominant, making it easier for them to attach. Corals are attracted to these calcareous algae, which also promotes their attachment. These corals propagate from the metal strip 20 to the wire mesh body 10, expanding the area where they attach. Furthermore, while there are many types of calcareous algae, the one that particularly contributes to the attraction and metamorphosis of corals is the calcareous algae that adhere in clumps and plates, as exemplified by the non-articulated coralline algae "Hydrolithon cruciatum." In this specification, the term "calcareous algae" is used as a general term to include these non-articulated coralline algae.

[0038] Fig. 5 shows the results of an experiment comparing the difference in coverage of calcareous algae on the front and back of the strip-shaped metal body 20. Fig. 6 shows the results of an experiment comparing the difference in the number of coral growths (number of new recruits) on the front and back of the strip-shaped metal body 20. In Figs. 5 and 6, A, B, C, and D respectively indicate samples of the strip-shaped metal body 20, and sample A in Fig. 5 and sample A in Fig. 6 are the same sample, as are samples B, C, and D. The experiment shown in Figs. 5 and 6 shows the results of a sample that initially had no calcareous algae or coral growing on it, which was set in the form of the coral-growth net 1 of this embodiment at a depth of 2 to 3 m in the sea, and the front and back were observed after 4 months.

[0039] 5 and 6, it can be seen that almost no calcareous algae or coral grows on the front side of the metal strip 20, while a large amount of calcareous algae and coral grows on the back side. From these experimental results, it can be said that by placing the metal strip 20 and creating a shaded area on the back side where light is less likely to reach, calcareous algae can be grown, and as a result, coral growth can be promoted.

[0040] Furthermore, in the first embodiment, the metal material constituting the band-shaped metal body 20 has a more negative ionization tendency than the metal material of the wire mesh main body 10. This also promotes lime (calcium carbonate) deposition due to the potential difference between the wire mesh main body 10 and the band-shaped metal body 20. As described above, the band-shaped metal body 20 is resistant to corrosion, while the wire mesh main body 10 is susceptible to corrosion. Therefore, the coral-growth net 1 of the first embodiment is suitable for use in growing coral species that require a long period of time to grow, as the band-shaped metal body 20 is inhibited from corroding for a long period of time. Furthermore, because the wire mesh main body 10 is susceptible to corrosion, the wire mesh main body 10 does not remain for a long period of time and naturally disappears. Although the band-shaped metal body 20 will remain for a longer period of time than the wire mesh main body 10, it can be made to disappear after an appropriate period of time has passed by providing it with a thickness that allows it to gradually corrode and disappear after sufficient coral growth has occurred.

[0041] As described above, the coral-growth net 1 of the first embodiment promotes the growth of calcareous algae, particularly on the back side (the side facing the seabed) of the strip-shaped metal body 20, thereby promoting the growth of coral. Furthermore, by deforming the strip-shaped metal body 20 into a corrugated shape and installing it, it is possible to prevent most of the coral-growth net 1 from being buried in silt, sand, gravel, etc., thereby increasing the coral growth rate. Furthermore, the coral-growth net 1 of the first embodiment has a very simple configuration, can be provided inexpensively, and can be used in a wide variety of locations, making it highly feasible. Furthermore, since the coral-growth net 1 does not require external energy sources or complex structures, its manufacturing process is environmentally friendly, and it also has a low environmental impact in terms of its natural disappearance. Thus, the coral-growth net 1 and the installation method for the coral-growth net 1 of the first embodiment enable the natural spread of coral over a wide area without the need for coral seedlings or transplantation, using a simple, inexpensive, and environmentally friendly structure.

[0042] (Second embodiment) As previously mentioned, in the present disclosure, the metals constituting the wire mesh main body 10 and the strip-shaped metal body 20 are dissimilar metals to control corrosion of the coral-growth net. More specifically, corrosion of the coral-growth net is controlled by the difference in ionization tendency between the metals constituting the wire mesh main body 10 and the strip-shaped metal body 20. The second embodiment is similar to the first embodiment except that the metal material constituting the strip-shaped metal body 20 has a more positive ionization tendency than the metal material of the wire mesh main body 10. Therefore, only the parts related to the above changes will be explained, and redundant explanations will be omitted as appropriate.

[0043] The metal material constituting the strip-shaped metal body 20 in the second embodiment has a more positive ionization tendency than iron, which is the metal material of the wire mesh main body 10. Specifically, the metal material constituting the strip-shaped metal body 20 in the second embodiment is aluminum. Note that the strip-shaped metal body 20 used in the second embodiment is not limited to aluminum, and metal materials with a more negative ionization tendency than iron, such as zinc, magnesium copper, etc., can be used as appropriate. Note that stainless steel can also be used as the metal material constituting the strip-shaped metal body 20 in the second embodiment. In that case, it is preferable that the wire mesh main body 10 be made of a metal material with a more negative ionization tendency (more positive potential) than stainless steel, rather than iron. Examples of such metals include silver, platinum, and gold. Furthermore, as with the first embodiment, it is desirable that the metal material constituting the strip-shaped metal body 20 be easily plastically deformed by manual deformation.

[0044] In the second embodiment, the wire mesh main body 10 can also be made of, for example, stainless steel, but in this embodiment, the metal material of the strip-shaped metal body 20 has a more positive ionization tendency (more negative potential) than the metal material of the wire mesh main body 10. Therefore, if the wire mesh main body 10 is made of stainless steel in the second embodiment, it is preferable to use a metal material for the strip-shaped metal body 20 that has a more positive ionization tendency (more negative potential) than stainless steel. Examples of such metal materials include iron and aluminum.

[0045] The shape of the band-shaped metal body 20 used in the second embodiment may also be selected as appropriate, but for example, a thickness of 0.2 mm to 1 mm is desirable because this facilitates the deformation process (described below) of deforming the coral-growth net 1 into a wavy shape. Furthermore, the width of the band-shaped metal body 20 is not particularly limited as long as it is wide enough to penetrate the mesh 12 of the wire mesh main body 10. However, in order to promote coral growth, it is desirable that the width of the band-shaped metal body 20 be 8 mm or more. In this embodiment, the band-shaped metal body 20 is constructed using aluminum with a thickness of 0.3 mm and a width of 10 mm.

[0046] In the second embodiment, the metal material constituting the strip-shaped metal body 20 has a more positive ionization tendency than the metal material of the wire mesh body 10, so that the strip-shaped metal body 20 has a lower potential than the wire mesh body 10 and is more likely to ionize, i.e., the strip-shaped metal body 20 is more susceptible to corrosion, while the wire mesh body 10 is less susceptible to corrosion. Due to this characteristic, the coral-growth net 1 of the second embodiment is suitable for use in situations different from those of the coral-growth net 1 of the first embodiment.

[0047] When growing corals in a natural environment, depending on the type of coral naturally growing at the site and the environment, it may take a long time for the corals to grow, but in other cases it may be possible for the corals to grow in a relatively short time. In the coral-growth net 1 of the second embodiment, the metal strip 20 corrodes faster than in the first embodiment, so it can be used preferably in cases where corals can grow in a relatively short time.

[0048] In the second embodiment, the metal material constituting the band-shaped metal body 20 has a more positive ionization tendency than the metal material of the wire mesh main body 10, so the band-shaped metal body 20 becomes the cathode. Basic zinc carbonate compounds (e.g., ZnCO3) are naturally produced at the cathode in the sea, which also has the effect of promoting the settlement of coral larvae.

[0049] According to the coral-growth net 1 of the second embodiment, the band-shaped metal body 20 corrodes easily, causing the band-shaped metal body 20 to disappear early, while corrosion of the wire mesh main body 10 is suppressed. Therefore, in the second embodiment, corals grow on the band-shaped metal body 20 earlier than in the first embodiment, and the corrosive action spreads to the wire mesh main body 10, expanding the area of ​​growth. Furthermore, after the band-shaped metal body 20 disappears, corrosion of the wire mesh main body 10 progresses, but because the wire mesh main body 10 itself is made of thin metal wire (made of iron in this embodiment) and is easily corroded, the wire mesh main body 10 also eventually disappears.

[0050] In general, it is often considered undesirable for aesthetic reasons to leave artificial objects such as the wire mesh body 10 and the metal strip 20 on a coral reef for a long period of time. In the second embodiment, although it depends on the selection of the metal material and the settings of its width and thickness, it is possible to promote corrosion of the metal strip 20, making it easier to hasten the disappearance of the entire coral-growth net 1 than in the first embodiment.

[0051] (Variations) The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible, and these are also within the scope of the present disclosure.

[0052] (Variation 1) In the first embodiment, the metal material constituting the band-shaped metal body 20 has a more negative ionization tendency than the metal material of the wire mesh main body 10, and in the second embodiment, an embodiment has been exemplified in which the metal material constituting the band-shaped metal body 20 has a more positive ionization tendency than the metal material of the wire mesh main body 10. This is not limiting, and for example, in one coral growth net, the metal material constituting the band-shaped metal body may be a mixture of a first band-shaped metal body (corresponding to the band-shaped metal body 20 in the first embodiment) having a more negative ionization tendency than the metal material of the wire mesh main body 10 and a second band-shaped metal body (corresponding to the band-shaped metal body 20 in the second embodiment) having a more positive ionization tendency.

[0053] (Variation 2) In each embodiment, in the first embodiment, the metal material constituting the band-shaped metal body 20 has a more negative ionization tendency than the metal material of the wire mesh main body 10, and in the second embodiment, the metal material constituting the band-shaped metal body 20 has a more positive ionization tendency than the metal material of the wire mesh main body 10. These two types of coral growth nets may be combined and installed in the sea. This allows multiple types of coral with different ease of growth to naturally grow on them.

[0054] (Variation 3) In each embodiment, the wire mesh body 10 has been described as being made of iron or stainless steel. However, this is not limiting, and the wire mesh body 10 may be made of other metals, such as aluminum or copper. Even in these cases, the metal material constituting the wire mesh body 10 and the metal material constituting the strip-shaped metal body 20 are configured to have different ionization tendencies, thereby controlling corrosion of the coral growth net.

[0055] (Modification 4) In each embodiment, the metal strip 20 has been described as being made of stainless steel or aluminum. However, the metal strip 20 may be made of a shape memory alloy, for example. In this case, it is preferable to deform the metal strip 20 into a wave shape beforehand.

[0056] (Variation 5) In each embodiment, an example has been described in which the band-shaped metal body 20 is made of a metal material with a different ionization tendency from the metal material of the wire mesh main body 10. However, this is not limiting, and for example, the band-shaped metal body 20 may be made of a metal material with the same ionization tendency as the metal material of the wire mesh main body 10.

[0057] The embodiments and modifications may be used in combination as appropriate, but detailed description thereof will be omitted. The present disclosure is not limited to the embodiments described above. [Explanation of symbols]

[0058] 1. Coral Adhesion Net 1a Convex part 1b Recess 10 Wire mesh body 11 Linear part 12 Mesh 12a First Mesh 12b Second mesh 20 Metal strip

Claims

1. A metal coral settlement net for growing corals, a metal wire mesh body having mesh holes; a strip-shaped metal body extending alternately from one side to the other side of the wire mesh body through the mesh of the wire mesh body; A coral settlement net equipped with

2. The coral adhesion net according to claim 1, The metal material constituting the strip-shaped metal body has a more negative ionization tendency than the metal material of the wire mesh body; A coral epiphytic net characterized by:

3. The coral adhesion net according to claim 1, The metal material constituting the strip-shaped metal body has a more positive ionization tendency than the metal material of the wire mesh body; A coral epiphytic net characterized by:

4. The coral adhesion net according to claim 1, The metal strip is a first band-shaped metal body made of a metal material having a more negative ionization tendency than the metal material of the wire mesh body; a second band-shaped metal body made of a metal material having a more positive ionization tendency than the metal material of the wire mesh body; Both of the above are provided. A coral epiphytic net characterized by:

5. A method for installing a coral growth net according to any one of claims 1 to 4, A method for installing a coral growth net, comprising: bending the coral growth net so that multiple convex portions that are convex on one side of the coral growth net and multiple concave portions that are convex on the other side of the coral growth net are lined up along the direction in which the strip-shaped metal body extends; and installing the coral growth net in the sea.

6. The coral adhesion net according to claim 2; The coral adhesion net according to claim 3; This is a method of installing a coral settlement net by combining these and setting it underwater.

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