AU2013279648A1

AU2013279648A1 - Aquaculture net with strong bottom

Info

Publication number: AU2013279648A1
Application number: AU2013279648A
Authority: AU
Inventors: Eline DE ROOSE; Jeroen Gallens
Original assignee: Bekaert NV SA
Current assignee: Bekaert NV SA
Priority date: 2012-06-19
Filing date: 2013-06-04
Publication date: 2014-11-06
Also published as: CL2014003259A1; CN104411164A; WO2013189732A1; JP2015525080A; MX2014014541A

Abstract

The invention relates to an aquaculture net (60) having a bottom (64) and side walls (62), wherein said bottom and said side walls comprise steel wires, and wherein said bottom has a penetration strength that is higher than the penetration strength of said side walls thus resulting in a difference in penetration strength. The advantage of the aquaculture net is to prevent predators from breaking in the net.

Description

WO 2013/189732 PCT/EP2013/061486 1 AQUACULTURE NET WITH STRONG BOTTOM Description Technical Field [0001] The invention relates to an aquaculture net having a high penetration strength, in particular at the bottom part thereof, and thus preventing the attacks from the predators. Background Art [0002] Aquaculture nets or fish-farming nets are used to raise aquatic life such as fish. The aquaculture net keeps the aquatic life controlled and contained inside the net. However, predators, such as seals or sharks attack the nets, usually at night, irrespective of the size and species of fish in the aquaculture nets. The seals damaged both nets and fish, and sometimes fish escaped as a result of the attacks. How to protect the aquatic life inside the net against predators, i.e. mitigation of predators/fisheries interactions, has been the subject of fisheries operations. [0003] Mitigation measures can be described as modification to fishing practices and/or equipment in order to reduce interactions between predators and fisheries operations. [0004] Possible solutions include the use of devices that repel marine mammals from fishing areas or condition them to avoid these areas. For example, explosive devices, such as seal crackers or underwater firecrackers are thrown into the water where they explode under the surface. Also, acoustic harassment devices or acoustic deterrent devices have been developed and installed close to the aquaculture net. Deterrents as such helped reduce the number of seal attacks. However, on one hand, they are not totally successful to prevent seals from attacking fish-farms and there were many attacks in the presence of underwater acoustic seal scarers. On the other hand, there are associated issues concerning animal ethics and permits as the long term impacts of high intensity signals on marine mammals are not known. Seals appear to be undeterred by acoustic deterrent devices but may experience hearing damage at close range.

WO 2013/189732 PCT/EP2013/061486 2 [0005] Another solution would be the removal of individual seals by capture and relocation. However, the merit of the trapping and relocation of seals from marine fish farms is debatable, because whilst relocation benefits fish farmers, this can be at the cost of others. In addition, for those seals that may attack farms most frequently, i.e. seals which cannot be trapped or seals which have been captured/removed previously, the effectiveness of this method is limited. Thus, capture and relocation is rarely used as a broad scale management tool. [0006] The only way to effectively prevent seals from attacking fish-farms is to exclude them from the vicinity of the fish nets with physical barriers that they cannot penetrate. These are currently in use, and include perimeter fences around flexible polyethylene pipe pens and protection nets made of steel mesh. Steel mesh is a fence of steel wires woven into a diamond pattern. The aquaculture nets are usually of the chain-link fence type. The meshes have a dimension that is smaller than the dimension of the fish contained in the nets. Each steel wire is preformed by bending so that it exhibits a wavy pattern with maxima and minima. The maxima or the peak of the wave has the highest amplitude value while the minima or the trough of the wave has lowest amplitude value. The maxima of a steel wire interlock with the minima of a neighbouring wire to form the patterns of a series of diamonds. [0007] Aquaculture nets of the chain-link fence type have proven to be successful to control the aquatic life and to protect against predators. Experience has shown, however, that aquaculture nets of the chain-link fence type also cannot completely avoid the damage from the attacks of predators. The bottom part is a critical factor as the predators can grab the dead fishes and break in the cage. They do this by repeatedly attacking the cage, deforming the wires (until fracture) and increasing the mesh size until they get into the cage. Disclosure of Invention [0008] It is an object of the invention to avoid the disadvantages of the prior art. [0009] It is a further object of the invention to provide an aquaculture net having a higher penetration strength at the lower part.

WO 2013/189732 PCT/EP2013/061486 3 [0010] It is also an object of the invention to provide an aquaculture net with a prolonged life time. [0011] According to a first aspect of the present invention, there is provided an aquaculture net. The aquaculture net can be divided in at least two parts, i.e. a lower part and an upper part. Said lower part has penetration strength that is higher than the penetration strength of said upper part, thus resulting in a difference in penetration strength. [0012] Herewith, the penetration strength may be defined as the resistance of the aquaculture net to failure under a penetrating load or an attack, and is a relevant parameter to indicate the strength of the aquaculture net against attacks of the predators. [0013] The net can be made of a polymer, such as polyethylene, polyester or polyamide. The net is preferably made of metal wires, e.g. steel wires. Other suited metal wires are made of copper alloy or titanium. [0014] The difference in penetration strength is realized by any one or any combination of a) said lower part having wires which have a higher strength than wires in said upper part, b) said lower part having wires which are thicker than wires in said upper part, c) said lower part having a finer mesh than said upper part, d) said lower part attaching an additional piece of mesh, and use of barbed wires. [0015] In particular, said wires at the lower part of the aquaculture net have one or more of the following characteristics: a) a wire diameter that is larger than 2.0 mm, b) a tensile strength that is higher than 700 MPa, c) the wire mesh opening that is smaller than 40 mm, and d) the wire mesh opening that is decreased, e.g. divided by four, by an additional piece of mesh. [0016] Herewith, the mesh opening is normally diamond shaped or rhombus. The size of the mesh opening is defined as the longer liner distance or the long diagonal of the rhombus. [0017] The invention works for many embodiments by combining the wire or wire mesh with the penetration strength of a part or section to define penetration strength per section. [0018] The aquaculture net may be a chain-link fence.

WO 2013/189732 PCT/EP2013/061486 4 [0019] Said lower part is the bottom of said aquaculture net and said upper part is the side walls of said aquaculture net. Herein, the term "bottom" means the deepest or lowest part of the aquaculture net. It may be in a flat form having a rectangular or circular shape or may be in a funnel form. The side walls refer to the parts that forms the side of the aquaculture net. [0020] The aquaculture net, in particular the side wall, is preferably divided into sections having steel wire mesh of higher penetration for sections arranged more towards the bottom of the net. The sections are preferably arranged horizontally, i.e. parallel to the water level. [0021] The aquaculture net may comprise three parts, a lower part, an intermediate part and an upper part. Said lower part is the bottom of said aquaculture net, said intermediate part and said upper part are arranged horizontally and form the side walls of said aquaculture net. Herein, said lower part has a penetration strength that is higher than the penetration strength of said intermediate part, and said intermediate part has a penetration strength that is higher than the penetration strength of said upper part. [0022] As another example, the aquaculture net comprises three parts, a lower part, an intermediate part and an upper part. Said lower part is the bottom of said aquaculture net, said intermediate part and upper part are arranged horizontally and form the side walls of said aquaculture net. In this example, said lower part and said intermediate part having a same penetration strength that is higher than the penetration strength of said upper part. [0023] The steel wires may have a wire diameter that is smaller than 3.0 mm. In the three-part embodiment, the upper part may have steel wires with a diameter smaller than 2.0 mm. The intermediate part may have steel wires with a diameter ranging from 1.60 mm to 2.5 mm. The lower part may have steel wires with a diameter greater than 2.0 mm. Herein, the condition remains: the steel wire diameter of the lower part is larger than that of the intermediate part and the steel wire diameter of the intermediate part is larger than that of the upper part. [0024] In a specific embodiment, the aquaculture net may have a full flat bottom. Alternatively, the aquaculture net may also have a funnel shaped bottom.

WO 2013/189732 PCT/EP2013/061486 5 [0025] The wires of the aquaculture net may be steel wires. Preferably, the wires are stainless steel wires. More preferably, said steel wires have a metallic and/or polymeric coating to give an anti-corrosion and/or antifouling property to said steel wires. Most preferably, the aquaculture net is galvanized or copper nickel alloy coated. [0026] The coating may be formed by any available method, such as hot dipping, electrodeposition and cladding. [0027] The metal coating may be in the form of a strip or a foil that is fixed around the steel core. A strip of a suitable metal of controlled composition and predetermined and desired thickness can be formed into a tube form. The width of this strip is somewhat greater or equal to the circumference of the steel core to be covered. The strip is closed in a tube and welded on or around the steel core. [0028] In a preferred embodiment said metal coating is a copper nickel alloy. Copper nickel coatings have proven to provide good resistance against fouling, i.e. against fouling material that may grow on the mesh structure, because of the effect of copper, and a good resistance against corrosion because of the nickel. [0029] The ocean or the sea forms a huge challenge with respect to corrosion resistance. In addition to this highly corroding environment, the waves and tidings subject the aquaculture net to a continuous and repeated movement. The invention aquaculture net on the one hand have good antifouling and anti-corrosion resistance. On the other hand, in an invention aquaculture net of the chain-link fence type, each steel wire must carry the weight of the rest of the net below it. [0030] In addition, barbed wires may be installed on the outside of said aquaculture net. Preferably, said barbed wires are installed at the lower part of said aquaculture net with a separation distance of 5 meshes from each other. [0031] As such, the aquaculture net according to the invention preferably has the shape of a square, rectangular or cylinder, but may also be shaped as a cone, as a sphere, or any other shape, comprising sections of different diameter of the wire and different height of the parts or sections. In one WO 2013/189732 PCT/EP2013/061486 6 embodiment said aquaculture net has dimensions which are greater than 1 m x 1 m x 1 m (length x width x depth). [0032] According to the second aspect of present invention, there is provided an aquaculture net comprising wires, wherein that said wires are lower in penetration strength towards the top of the net in comparison with those at the bottom of the net. [0033] The solution provided by the present invention is based on the following principle. The lower the part within the net, the more chance to be attacked by predators, the higher penetration strength this part of the net must be. This can be realized by making the lower parts of the net with a bigger wire diameter, a higher tensile strength steel wire and a smaller mesh opening compared with the upper parts of the net. [0034] This enforced effect results in an overall optimization of the weight reduction and penetration strength improvement of the entire net. Therefore the life of the aquaculture net is prolonged while the material and production cost are reduced. Brief Description of Figures in the Drawings [0035] Figure 1 and 2 each show a top view of an installed aquaculture net (floating support). [0036] Figure 3 shows a side view of an installed aquaculture net according to the first embodiment of the present invention. [0037] Figure 4 shows a side view of a chain-link fence aquaculture net according to the second embodiment of the present invention. [0038] Figure 5 shows a view of a bottom of an aquaculture net according to the second embodiment of the present invention. [0039] Figure 6 shows an aquaculture net with barbed wires at the bottom according to the third embodiment of the present invention. Mode(s) for Carrying Out the Invention [0040] Figure 1 illustrates a square embodiment of a raft 10 for an aquaculture net as described by the present invention. The raft 10 comprises various galvanized steel bars 12 supported by high-density polyethylene (HDPE) WO 2013/189732 PCT/EP2013/061486 7 floating devices 16. A platform 14 is connected thereto. People can walk around on the platform 14. The aquaculture net can be directly connected to the steel bars 12 by means of ropes or wires. The galvanized steel bars 12,22 are isolated from the aquaculture net, i.e. no direct contact, when connections with steel wires are used. Alternatively, connections between the net and the raft 10,20 are made with ropes, i.e. non-metallic material, to prevent metallic contacts between the net and the raft in case of different materials used for the net and raft. [0041] Figure 2 illustrates a circular embodiment of a raft 20 for an aquaculture net as described by the present invention. A circular raft 20 may be made from HDPE tubes 26 connected to one another by means of brackets 22. A platform 24 is connected thereto. The aquaculture net can be suspended directly at the raft by means of ropes and/or wires. The bottom of the aquaculture net may still have the shape of a rectangle or square whereby the upper side takes a form close to a circle (more precisely, the form of a polygon). Embodiment 1 [0042] Figure 3 illustrates a side view of an embodiment of an installed aquaculture net according to the present invention. The floating support 10 is of the square type as illustrated in Figure 1. The aquaculture net is connected to the floating devices 16 by means wires or ropes (not shown). The bottom part of the aquaculture is not shown in Figure 3. The side wall 30 of the net comprises two sections each having a wire mesh of different penetration strength. [0043] In a first example, the diameter of the wire and the mesh openings are the same all over the aquaculture net. The upper or top section 32 has a wire with a tensile strength in the range of 400 to 800 MPa; the wire of the middle or intermediate section 34 has a tensile strength in the range of 600 to 1000 MPa; the wire of the lower or bottom section, deepest in the water, has a tensile strength in the range of 700 to 1500 MPa. Also it remains the tensile strength of the wire at the lower part is higher than that in the upper part.

WO 2013/189732 PCT/EP2013/061486 8 [0044] In a second example, the tensile strength of the wire and mesh openings are the same all over the aquaculture net. The upper or top section 32 has a diameter of about 1.60 mm; the wire of the middle or intermediate section 34 has a diameter of about 1.80 mm; the wire of the lower or bottom section, deepest in the water, has a diameter of about 2.20 mm. [0045] In a third example, the diameter and the tensile strength of the wire are the same all over the aquaculture net. The upper or top section 32 has a mesh opening in the range of 40 to 60 mm; the wire of the middle or intermediate section 34 has a mesh opening in the range of 30 to 50 mm; the wire of the lower or bottom section, deepest in the water, has a mesh opening in the range of 20 to 40 mm. Also it remains the mesh opening at the lower part is smaller than that in the upper part. [0046] In addition, the combinations of above any two or three examples are also possible. For instance, the tensile strength of the wire at the lower part is higher than that in the upper part and the mesh opening at the lower part is smaller than that in the upper part. [0047] In this embodiment, the side wall of the aquaculture net is divided into two sections 32 and 34. It is also possible that the side wall of the aquaculture net is divided into plurality of sections, which are preferably horizontally arranged. Herewith, the lower sections have higher penetration strength than the upper sections. [0048] In the three-part embodiment, the intermediate and the upper parts or sections 34, 32 may have the same size or height. Alternatively, the intermediate and the upper parts 34, 32 may have a different size or height. As one example, the height of the upper part may be greater than the height of the intermediate part, hereby reducing the entire weight of the aquaculture net. As another example, the height of the intermediate part may be greater than that of the upper part, hereby increasing the strength of the part which is easy to be attacked by predators. [0049] The various sections 32, 34 can be connected to one another in various ways, e.g. means of a spiralling steel wire going through the side openings of the neighbouring sections, e.g. by means of a metal rope going through the side openings of the neighbouring sections or e.g. by means of pieces of binding wire.

WO 2013/189732 PCT/EP2013/061486 9 [0050] Alternatively, the various sections consisted of the side wall of the aquaculture net do not form separate parts but are part of one continuous woven chain link fence made of same type of wire but different from the wires at the bottom section. Embodiment 2 [0051] Figure 4 shows an alternative embodiment of a side of a chain-link fence aquaculture net 40 according to the present invention. The aquaculture net is directly connected to the floating devices 16. The side wall of the aquaculture net comprises part of one continuous woven chain link fence with the same penetration strength which is lower than that of the bottom part. [0052] In this embodiment the first top wire 42 of the chain-link fence may be made of the largest diameter to be able to carry most weight and to strengthen the attachment to the floating raft. The wires 44,46 below have a smaller diameter and even smaller to the bottom of the net. [0053] Figure 5 is a view of the bottom of an aquaculture net 50 according to the second embodiment of the present invention. In this embodiment, the penetration strength of the bottom part is enhanced by attaching an additional chain link mesh 54. As shown in Figure 5, the additional chain link mesh 54 may have the same diameter and tensile strength with the original chain link mesh 52 of the bottom. Moreover, the additional chain link mesh 54 has the same mesh opening with the original chain link mesh 52. [0054] The two pieces of chain link mesh 52, 54 can be connected to one another in various ways, e.g. means of a spiralling steel wire going through the side openings of the neighbouring sections, e.g. by means of a metal rope going through the side openings of the neighbouring sections or e.g. by means of pieces of binding wire. Moreover, extra connections can be provided all over the entire bottom. For instance, a connecter 56 is provided every 5 meshes,1 0 meshes or 20 meshes. [0055] As shown in Figure 5, the two pieces of meshes are preferably arranged in such a way that the original chain link mesh are divided into almost four equivalent parts by the additional piece of chain link mesh.

WO 2013/189732 PCT/EP2013/061486 10 [0056] This embodiment provide the possibility to strengthen the aquaculture net, in particular the bottom part, after the aquaculture net is already produced or installed in case the attacks from the predators are initially overlooked. [0057] Similarly, more additional chain link mesh may be attached to make the aquaculture net stronger. In particular, additional piece of chain link mesh may be provided in a relatively weak region, e.g. the connection part of different pieces of chain link fence. Embodiment 3 [0058] In this embodiment, barbed wires are included as an extra deterrent for the predators. The barbed wires may be applied to any of the above introduced aquaculture nets. It may be applied all over the aquaculture net 60, i.e. at the side wall 62 and the bottom 64, or merely at the bottom 64 of the aquaculture net. Figure 6 shows an aquaculture net 60 with barbed wires 66 at the bottom 64. The aquaculture net in figure 6 shows a tunnel shaped round bottom, but it does not exclude a flat round bottom or a square shaped bottom aquaculture net. [0059] Herewith, the barbed wires may be conventional barbed wires available in the market, e.g. MOTTO@ wire. The barbed wire may also be made of the same material as the wires used in the aquaculture net. In particular, in case of metallic barbed wire and metallic net, the barbed wire and net are preferably made of the same material to prevent galvanic corrosion. [0060] The barbed wire can be connected to the chain link fence in various ways, e.g. means of a spiralling steel wire going through the side openings of the chain link fence, e.g. by means of a metal rope going through the chain link fence, e.g. by means of pieces of binding wire or e.g. by clips. A connecter may be provided for instance every 5,10 or 20 meshes. [0061] The distance between barbed wires may be different. However, the distance between barbed wires is preferably the same and the barbed wires are separated every 5, 10 or 20 meshes. [0062] The invention illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. It should be understood that although the present invention has been specifically disclosed by preferred WO 2013/189732 PCT/EP2013/061486 11 embodiments and optional features, modification and variation of the inventions embodied herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention. List of references 10 square raft 12 steel bar 14 platform 16 HDPE floating device 20 circular raft 22 bracket 24 platform 26 HDPE tube 30 side wall 32 top section 34 middle or intermediate section 40 side of an aquaculture net 42 first top wire 44 wire 46 wire 50 bottom of an aquaculture net 52 original chain link mesh 54 additional chain link mesh 56 connecter 60 aquaculture net 62 side wall 64 bottom 66 barbed wire

Claims

1. An aquaculture net having a bottom and side walls, wherein said bottom and said side walls comprise steel wires, and wherein said bottom has a penetration strength that is higher than the penetration strength of said side walls thus resulting in a difference in penetration strength.

2. An aquaculture net according to claim 1, wherein said difference in penetration strength is realized by any one or any combination of a) said bottom having steel wires which have a higher strength than wires in said side walls, b) said bottom having steel wires which are thicker than wires in said side walls, c) said bottom having a finer wire mesh than said side walls, d) said bottom attaching an additional piece of mesh, and e) use of barbed wires.

3. An aquaculture net according to claim 2, wherein said steel wires at bottom have one or more of the following characteristics: a) a steel wire diameter that is larger than 1.6 mm, b) a tensile strength that is higher than 700 MPa, c) the wire mesh opening that is smaller than 40 mm, and d) the wire mesh opening that is decreased by the additional piece of mesh.

4. An aquaculture net according to any one of the preceding claims, wherein said aquaculture net is a chain-link fence.

5. An aquaculture net according to any one of the preceding claims, wherein said side walls of said aquaculture net comprise at least two parts, a lower part and an upper part, and wherein said lower part has a penetration strength that is higher than the penetration strength of said upper part.

6. An aquaculture net according to any one of the preceding claims, wherein said aquaculture net has a full flat bottom. WO 2013/189732 PCT/EP2013/061486 13

7. An aquaculture net according to any one of the preceding claims, wherein said aquaculture net has a funnel shaped bottom.

8. An aquaculture net according to any one of the preceding claims, wherein said steel wires have a metallic and/or polymeric coating to give an anti-corrosion and/or antifouling property to said steel wires.

9. An aquaculture net according to claim 8, wherein said metallic coating is copper nickel alloy.

10. An aquaculture net according to claims 2 to 9, wherein barbed wires are installed on the outside of said aquaculture net.

11. An aquaculture net according to claim 10, wherein barbed wires are installed at said bottom of said aquaculture net with a separation distance of 5 meshes from each other.