Fish cage

Abstract

A fish cage is provided, comprising a fish bag (130) with an inclined panel (136), separating an upper vertical part (132) and a lower bottom part (134) of the fish bag, wherein each position along the circumference of the fish cage, the sinker tube (120) is connected to an upper attachment (152) where the upper vertical part (132) of the fish bag (130) connects to the inclined panel (136), and to a lower attachment (154) where the bottom part (134) of the fish bag (130) connects to the inclined panel (136).

Description

[0001] TITLE: BASE CONNECTION POINT - FISH CAGE

[0002] Background of the Invention

[0003] Field of the Invention

[0004] The invention relates to a fish cage and more specifically a system for distributing forces acting on the different parts of a fish cage, such as a floating collar, weights such as a sinker tube, ropes and lines guys that connect the parts and a fish bag containing the fish.

[0005] Background Art

[0006] State of the art is reflected in traditional fish pens.

[0007] Most fish is still farmed in a traditional fish cage in the sea, having a floating collar on the surface of the sea, and bag stretching downwards from the floating collar. The cage may be an open cage having a bag of net, a closed cage having a bag of waterproof material such as tarpaulin or of stiff material such as fibreglass or even concrete. The cage may further be semi-closed meaning that the bag is partly of a material preventing water to flow through, and partly of a material allowing water to flow into the cage. A cage provided with a "skirt" of a material preventing water from flowing into the cage will also be considered as a semi-closed cage in relation to the present invention. The "skirt" may either be in addition to the regular bag or be integrated in the material of the bag, and is normally arranged from the top of the fish cage to a depth where the number of parasites such as salmon lice, is considerably reduced. The bag may be referred to as "cage bag" or "fish bag" in relation to this application.

[0008] When farming fish in a net cage, it is important to keep the mesh of the net expanded to ensure that sufficient water flow through to keep the water quality in the cage at a desired level. Further, the net should be expanded to give the fish sufficient volume to move and to prevent the fish from being injured due to entanglement or pressure. Therefore, a number of weights are connected to the lower parts of the wall and / or the bottom of the net cage, such as a sinker tube and / or bottom weights. The weights or sinker tube are fastened to the net cage in a transition between net wall and net bottom, keeping the walls down and as close to vertical as possible. Water current passing through the net will act on the wall, and the forces will try to displace it from vertical position.

[0009] The different parts of a fish cage, including the fish bag, the floating collar and the sinker tube are connected with lines that during normal operations keep the fish bag expanded. In situations with strong currents, the forces acting on the cage can exceed the maximum capacity and there is a risk that parts of the cage breaks or detach, with the worst-case scenario that the fish bag rips open, letting the fish inside escape.

[0010] The bottom weights and / or sinker tube are traditionally fastened to the fish bag at the transition between wall and bottom, to keep the fish bag expanded radially. The bottom weights and / or sinker tube will drag the fish bag downwards and outwards while the surroundings, such as water currents and wind will drag the fish bag to the side and upwards. The fastening between the bottom weights and / or sinker tube are thus exposed to forces which may be very large and discontinuous, and the forces needs to be distributed to the whole cage in order to avoid rupture of the bag.

[0011] From prior art one should refer to WO 2014189383 and NO 20200678, which disclose a typical fish pen.

[0012] In various situations, one may need to lift the fish bag, and this may be performed by simultaneously lifting the sinker tube. Lifting may for instance be necessary upon emptying or treatment of the fish in the fish cage, but also upon cleaning and replacement of the net cage. The fish bag may be lifted by pulling the sinker tube rope, and by pulling the bag and collecting it at the inside of the fish cage. The sinker tube ropes are distributed along the floating collar and must be pulled at the same time, or stage by stage on turn to avoid risks for stretch and tear of the bag. The same is related to lifting and collecting of the bag. This is time consuming and labour intensive, and the work may also be heavy and dangerous. There is also a risk of damage to the fish bag that can lead to fish escaping.

[0013] There is therefore a need for a system to overcome the above-mentioned problems. Summary of the Invention

[0014] By terms such as “up”, “down”, “circumference”, and “centre”, it is meant the directions that naturally occur when the system is deployed for use in a body of water. Vertical and horizontal also refers to the situation when the system is deployed and ready to use.

[0015] By “strengthening element”, it is in the context of this application meant any element such as lines or ropes, that strengthens the fish bag and protects the fish bag from excessive load. Such strengthening elements can be provided at different positions and are often given specific names. In the following, the following specific names are used: a “vertical strengthening element fastened to the wall of the fish bag, running from the floating collar to the bottom” is also known as a “lifting rope”, a “bottom part strengthening element” fastened to the bottom of the fish bag, running from the wall of the fish bag to the centre of the bottom, is also known as a “cross rope”, and a “horizontal strengthening element” fastened to the wall of the fish bag in circumferential direction is known as “waist line”. The lifting ropes and cross ropes may be the same rope running from the floating collar, along the wall, and across the bottom to the centre of the bottom. The waist line may be arranged at the top of the fish bag, at the transition between wall and bottom, and at any position between the top and bottom. The lifting ropes and waist line will cross each other and create a grid on the fish bag.

[0016] By “lines”, it is meant “ropes” that may comprise fibres that are twisted or weaved, but not chains.

[0017] Problems to be Solved by the Invention

[0018] Therefore, a main objective of the present invention is to avoid damages to the fish bag, both when deployed at sea and also during lifting, and to provide a system for distributing forces acting on a fish cage that can keep the fish bag stable and expanded without the risk of damage to the fish bag.

[0019] Means for Solving the Problems

[0020] The objective is achieved according to the invention by fish cage as defined in the preamble of claim 1 , having the features of the characterising portion of claim 1 . A number of non-exhaustive embodiments, variants or alternatives of the invention are defined by the dependent claims.

[0021] The present invention attains the above-described objective by a panel connecting an upper vertical wall to a lower bottom part, wherein the panel inclines from the wall towards the centre of the fish bag.

[0022] In a first aspect of the invention, a fish cage is provided, comprising a floating collar, a fish bag, a sinker tube below the wall, and strengthening elements, wherein the strengthening elements connect the floating collar, the fish bag, and the sinker tube so as to keep the fish bag expanded when deployed, and wherein the strengthening elements carry at least partly a load of the sinker tube. The fish bag comprises an upper vertical wall and a lower bottom part connected by a panel inclining from the wall towards the centre of the fish bag. The sinker tube is connected to the fish bag at a plurality of positions distributed along the circumference of the fish bag, wherein at each position the sinker tube is connected: to an upper attachment where the wall of the fish bag connects to the inclined panel, and to a lower attachment where the bottom part of the fish bag connects to the inclined panel.

[0023] The technical effect is that the connection between the sinker tube and the fish bag is at two different points, and the connection line between the sinker tube and the fish bag will be in a triangle. Thus, connections are now made at two base connection points, distributing the forces over a wider area, compared to the traditional single base connection point solution, and that the fish bag and the sinker tube are kept well apart.

[0024] By "a panel inclining from the wall towards the centre of the fish bag" while still connecting the wall and bottom part, it is herein meant that the upper circumference of the bottom is smaller than the lower circumference of the wall. When being connected to the wall in an upper part, and a smaller circumference of the bottom at the lower part, the panel will be inclining.

[0025] An angle of the transition between wall and bottom will be separated in two, meaning that the angles between wall and panel and bottom and panel will be blunter when using a panel. The use of the inclined panel thus also has the effect of eliminating an inner corner in prior art where the upper vertical part and the lower bottom part meet. With the inclined panel inserted, there are now two angles that are more obtuse, which makes it easier to clean the fish bag, especially using robots.

[0026] In one embodiment, the upper and lower attachments are connected by an inclined strengthening element.

[0027] This improves mechanical stability and reduces tension on the inclined panel. The inclined strengthening element together with the lines from the upper and lower attachments to the sinker tube, defines a closed triangle that provides mechanical stability.

[0028] Preferably, the inclined strengthening element is normally kept in an un-tensioned state, and will take up potentially damaging forces, preventing damage to the fish bag, were the other strengthening elements to be damaged.

[0029] In one embodiment, the sinker tube is connected to the fish bag using an intermediate strengthening element, comprising an upper substantial vertical leg, connecting to a lifting rope connecting to the floating collar, a lower inclined leg, connecting to a cross rope along the bottom part of the fish bag, wherein a first attachment means is arranged between the intermediate strengthening element and the sinker tube.

[0030] The technical effect is that the forces applied to the upper and lower attachments are in a more beneficial direction, with less bending of the strengthening elements.

[0031] In one embodiment, the upper attachment is a lower end of a lifting rope, and the lower attachment is an upper end of a cross rope, so that in a stable position, the upper substantial vertical leg is substantially coaxial with the lifting rope, and the lower inclined leg is substantially coaxial with the strengthening element along the bottom part of the fish bag.

[0032] The technical effect is that the intermediate strengthening element is substantially a continuation of the attached lifting ropes and cross ropes, which means said ropes are not bent. Strengthening elements, lifting ropes and cross ropes are typically lines made by twisted fibres, and repeated bending can reduce the useful lifetime of the lines. Further, if forces acts on a rope being bent, the forces are not acting equally on all fibres, and some of the fibres may break reducing the overall strength of the rope. In one embodiment, the first attachment means of the intermediate strengthening element is spliced into the upper inclined leg.

[0033] The technical effect is that the downward tension component from the force from the sinker tube is transmitted via the intermediate strengthening element to the lifting rope with minimal bending of the fibres in the strengthening element.

[0034] In one embodiment, wherein the intermediate strengthening element further comprises a second attachment means for connecting to a lifting line for raising the sinker tube with the fish cage.

[0035] The technical effect is that the upward tension component from the force from the lifting line is transmitted via the intermediate strengthening element to the cross rope and simultaneously to the sinker tube.

[0036] In one embodiment, wherein the second attachment means of the intermediate strengthening element is a line spliced into the lower inclined leg.

[0037] The technical effect is that upward tension component from the force from the lifting line is transmitted via the intermediate strengthening element to the strengthening element with minimal bending of the fibres in the strengthening element.

[0038] In one embodiment, wherein the second attachment means is also connected to the strengthening element connected to the sinker tube.

[0039] The technical effect is to provide redundancy in case the first attachment means should fail.

[0040] In one embodiment, the lifting rope, the upper substantial vertical leg, the lower inclined leg, and the cross rope are formed by one continuous line.

[0041] The technical effect is that the construction is stronger with a single continuous line compared to a plurality of lines and that the fibres in the lines are not strongly twisted as occurs inside knots, and also that the load is substantially along the direction of the fibres. Effects of the Invention

[0042] The present invention comprises a technological advantage over known systems and methods by use of an inclined panel between the vertical and the bottom part of the fish bag, wherein the inclined panel separates upper and lower attachments.

[0043] The present invention provides several further advantageous effects: it makes it possible to distribute forces to the fish bag in a safer way that is more resistant to fish bag damages, it makes it easier to clean the fish bag, especially in the region where the vertical part meets the inclined panel, and where the inclined panel meets the bottom part, the inclined panel also means that the part of the fish bag close to the attachment means or lines, are less susceptible to damage caused by friction between the fish bag and said attachment means or lines.

[0044] Brief Description of the Drawings

[0045] The above and further features of the invention are set forth with particularity in the appended claims and together with advantages thereof will become clearer from consideration of the following detailed description of an [exemplary] embodiment of the invention given with reference to the accompanying drawings.

[0046] The invention will be further described below in connection with exemplary embodiments which are schematically shown in the drawings, wherein:

[0047] Fig. 1 shows a typical fish cage according to prior art,

[0048] Fig. 2 shows a detail of Fig. 1 with the base connection point,

[0049] Fig. 3 shows a fish cage according to one embodiment,

[0050] Fig. 4 shows a detail of Fig. 3 with the base connection points, and

[0051] Fig. 5 shows a closeup of Fig. 4.

[0052] Description of the Reference Signs

[0053] The following reference numbers and signs refer to the drawings:

[0054] Detailed Description of the Invention

[0055] Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.

[0056] The invention will be further described in connection with exemplary embodiments which are schematically shown in the drawings.

[0057] Fig. 1 shows a typical fish cage 100 according to prior art. The fish cage 100 comprises a floating collar 110, a fish bag 130, a sinker tube 120 below the wall, and strengthening elements 140, wherein the strengthening elements connect the floating collar, the fish bag, and the sinker tube so as to keep the fish bag expanded. The strengthening elements may carry most of the load of the sinker tube, and is tensioned between the collar and the sinker tube. In alternative embodiments, most of the load of the sinker tube is carried by separate lines or chains connected to the floating collar, while separate lines from the sinker tube to the fish bag keep the fish bag expanded.

[0058] The floating collar 110 floats on the surface of the water, defining an upper part of the fish cage, while a sinker tube 120 hangs below, defining a lower part of the fish cage. The fish bag is attached and suspended from floating collar. Strengthening elements are typically laced to the fish bag so that there is some flexibility and that the load is substantially taken up by the strengthening elements and not the more fragile fish bag. When the strengthening elements are tensioned, they keep the fish bag expanded so that a large inner volume for fish is maintained.

[0059] Strengthening elements 140, 142, 144, 148, 149 are located around the fish bag, providing the means for keeping the fish bag expanded. The strengthening elements are shown as lifting ropes 142 running vertically along the vertical part 132 of the fish bag, and waist line 148 running substantially horizontally around the fish bag. The lifting ropes 142 continue into or are connected to the strengthening elements 149 connected to the sinker tube 120. The strengthening elements are also shown as cross ropes 144 running from an upper part of the bottom part 132 of the fish bag 130 inclined downwards towards a center of the bottom and possibly a bottom weight (not shown).

[0060] The fish bag 130 comprises an upper vertical part 132 shown as a wall and a lower bottom part 134 shown as a cone, wherein the sinker tube is connected to the fish bag at a plurality of positions distributed along the circumference of the fish bag. At each position the sinker tube is connected to an attachment at the transition between the wall and the bottom of the fish bag.

[0061] Fig. 2 shows a detail of Fig. 1 at one point along the circumference of the fish cage, with the conventional base connection point 150. In order to keep the fish bag well expanded, it is preferred that the diameter and position of the sinker tube are adapted so that the connection means 122 between the fish bag 130 and the sinker tube has a radial component and is not just vertical in the normal state. That means that there is a corresponding strong force acting on the fish bag at the base connection point 150.

[0062] Principles Forming the Basis of the Invention

[0063] The inventor has recognised that the forces acting on each base connection point 150 are strong. There is the downward force from the sinker tube 130 but also the radial outward force due to the sinker tube being wider than the fish bag. These are the static forces, which are experienced in calm weather. Rough weather will further add dynamic forces to this, which can exceed the strength of the fish bag, resulting in loss of integrity and fish escaping from the fish bag 130.

[0064] Fig. 3 shows how the construction in Fig. 1 can be modified to overcome these problems, and Fig. 4 shows a detail of Fig. 3 with the base connection points, and Fig. 5 shows a closeup of Fig. 4. By connecting the sinker tube 120 to the fish bag 130 at two different positions, here shown as upper 152 and lower 154 attachment, where the attachments are separated by an inclined panel 136 positioned between the vertical wall 132 and the bottom 134 part of the fish bag, the forces acting on the fish bag are distributed in a way that reduces the potentials for damage.

[0065] The inclined panel 136 has several advantages. As is made clear by Figs. 3 and 4, the inclined geometry means that the panel is kept further away from the lines and the intermediate strengthening element, compared to a geometry without the inclined panel. Especially during strong currents, could the strengthening element cause damage to the net in the case of a traditional construction.

[0066] The inclined panel also means that the transition between the different parts of the fish bag are now separated by two transitions where the angle is now more obtuse than for a traditional construction. This is an advantage during cleaning, making the transition areas more accessible. The obtuse angle means that a cleaning device such as a robot, can straddle a transition without losing contact with the fish bag surface.

[0067] The attachments are typically parts of or extensions of the lifting ropes 142 and the cross ropes 144. Several embodiments are envisioned, such as the use of eye splice, optionally with a thimble, or the use of splicing, for connection directly or indirectly to the sinker tube.

[0068] In the case that the attachment points are connected to the sinker line, it is likely that the strengthening elements will experience a force that bends the fibres in the strengthening elements and possibly also applies too much radial force to the fish bag.

[0069] The inventor has realised that the above described structure can synergistically be further improved using an intermediate strengthening element.

[0070] In an embodiment, the two lines from the attachments 152, 154 to the sinker tube are replaced by two lines 210, 220 to the intermediate strengthening element plus one line from the strengthening element to the sinker tube. As the strengthening element is positioned closer to the fish bag, the bending forces and the radial forces will decrease.

[0071] Figs. 4 and 5 show an optimum position that can be achieved when the lines from the attachments extend coaxially with the respective strengthening elements. This can be designed for the static situation with no wind or currents, but it will be appreciated that in a non-static situation, this position is still a good position, and likely to be an improvement over the embodiment where the attachments are directly connected to the sinker line.

[0072] This also simplifies the work in handling the ropes and connections. The inventor has realised that the above described structure can synergistically be even further improved using an intermediate strengthening element 200, where first attachment means 212 is a line laced into the upper inclined leg 210. The first attachment means 212 is typically a loop, such as made by an eye splice, for attaching a line to the sinker tube. In this configuration, the bending of the fibres is minimised, the wear and tear is reduced, and the load bearing capacity is improved.

[0073] Similarly a second attachment means 222 can be a line spliced into the lower inclined leg 220, for instance for attaching a line to be used under hoisting of the net.

[0074] Best Modes of Carrying Out the Invention

[0075] It is preferred that the attachments 150 are placed where strengthening elements intersect, so that the upper attachment 152 is located where the lifting ropes 142 intersect with the horizontal strengthening element 148, and / or so that the lower attachment 154 is located where the cross ropes 144 intersect with the horizontal strengthening element 148.

[0076] Under normal circumstances, the forces on the fish bag and the strengthening elements should balance out as for the static situation. Nevertheless, an inclined strengthening element 146 connecting the upper 152 and lower 154 attachments is preferred as added safety. Fish cages are strictly regulated and it is important to prevent escape of the fish contained within the fish bag. It is preferred to use an inclined un-tensioned strengthening element. This will maintain the integrity of the fish bag 130 when strong forces act on the fish cage 100, by limiting the deformations caused.

[0077] While it is preferred that the first 222 and second 212 attachment means are both connected to the strengthening element connected to the sinker tube 120, it is preferred to use a larger loop for the second attachment means, so that in normal use, only the first attachment means is tensioned. Should the first attachment means be damaged, the second attachment means will take over. The first attachment means is expected to be subjected to more wear than the un-tensioned second attachment means, thus providing improved reliability through this fail safe mechanism. During lifting, the lifting line 214 is raised, which raises both the fish bag 130 together with the sinker tube 120, keeping both at safe distance from each other. Further lifting force is preferably applied to a secondary lifting line 124 directly connected to the sinker tube. Lifting lines are preferably provided at a plurality of positions distributed along the circumference of the fish cage 100.

[0078] It is preferred that the inclined panel 136, the vertical wall 132 and the bottom part 134 are all made of the same material, to reduce differential forces caused by currents in the water.

[0079] Alternative Embodiments

[0080] A number of variations on the above can be envisaged. For instance, the strengthening element, typically shown as an Y-shaped structure, can alternatively be a ring that clips on or otherwise attaches to the strengthening elements, possibly via an extension part. Said ring can then, in itself, be the attachment for the line connecting the sinker tube 120.

[0081] The base connection area shown in Fig. 3 has an upper 152 and a lower 154 attachment that are vertically aligned. That is not a requirement since the attachments can be offset, and that the intermediate panel means that an intermediate strengthening element can reach a neighbouring position along the circumference of the fish cage 100. A zig-zag structure will maintain the desired structure of the fish bag.

[0082] It is also possible that the intermediate strengthening element engages with more than two attachments.

[0083] In the embodiments shown, a sinker tube 120 is used to provide tensioning and also a force to keep the lower part of the vertical wall 132 of the fish bag 130 expanded.

[0084] In a variation, the sinker tube is replaced with a plurality of weights. These will provide a tensioning force but not the force to keep the lower part of the fish bag 130 expanded. In this embodiment, the floating collar 110 will still provide a force to keep at least the upper part of the fish bag expanded.

[0085] The panel should be sufficiently wide to reduce the bending of the strengthening elements, and thereby reducing the wear and tear of the elements as described above. Further, the panel should be sufficiently wide to allow distance between the fish bag and the attachment lines and / or sinker tube, to reduce or avoid contact and possible tear.

[0086] Even further the panel should be sufficiently wide to separate the transition from wall to panel and panel to bottom to make it easier to clean the fish bag in these regions. The cleaning and access to the transition area between wall and bottom will be further eased as the one angle between wall and bottom will be separated in two angles, meaning that the angle between wall and panel and the angle between bottom and panel will be larger.

[0087] When the fish cage is installed in exposed locations with strong water current and waves, it may be beneficial to allow movement of the first and second attachment of the sinker tube in relation to each other, and the panel should be wide enough to allow such movement. The necessary width to achieve the above said effects will depend on the size and dimensioning of the fish cage as such, and also on localization it should be installed, and will be obvious to a skilled person.

[0088] Such material of the panels may then differ from the material of the upper vertical wall 132 and / or the lower bottom part 134 both in terms of structure and / or whether or not the panel is open or closed in terms of flow of water.

[0089] The width of the panel may be very narrow, in some examples even a thick rope, as long as one can fit upper 152 and lower 154 attachments on opposite sides of the thick rope. This will still provide the technical effect of distributing the forces over a wider area, compared to the traditional single base connection point solution, and that the fish bag and the sinker tube are kept well apart.

[0090] As described above, the panel may also be very wide.

[0091] Industrial Applicability

[0092] The invention according to the application finds use in fish farming, using fish bags tensioned by a floating collar and a sinker tube.

Claims

Claims1 . A fish cage (100) comprising: a floating collar (110), a fish bag (130) having an upper vertical wall (132) and a lower bottom part (134), a sinker tube (120) below the upper vertical wall (132), and strengthening elements (140, 142, 144, 148, 149), wherein the strengthening elements (140, 142, 144, 148, 149) connect the floating collar (110), the fish bag (130), and the sinker tube (120) so as to keep the fish bag (130) expanded when deployed, and wherein the strengthening elements (140, 142, 149) carry at least partly a load of the sinker tube (120), characterised in that the upper vertical wall (132) and the lower bottom part (134) are connected by a panel (136), inclining from the wall towards the centre of the fish bag, wherein the sinker tube (120) is connected to the fish bag (130) at a plurality of positions distributed along the circumference of the fish bag (100), wherein at each position the sinker tube (120) is connected: to an upper attachment (152) where the upper vertical wall (132) of the fish bag (130) connects to the inclined panel (136), and to a lower attachment (154) where the bottom part (134) of the fish bag (130) connects to the inclined panel (136).

2. The fish cage (100) according to claim 1 , wherein the upper and lower attachments (150, 152, 154) are connected by an inclined strengthening element (146).

3. The fish cage (100) according to claim 1 or 2, wherein the sinker tube (120) is connected to the fish bag (130) using an intermediate strengthening element (200), comprising: an upper substantial vertical leg (210), connecting to a lifting rope (142) connecting to the floating collar (110) via the fish bag (130), a lower inclined leg (220), connecting to a strengthening element along the bottom part (134) of the fish bag (130), and a first attachment means (222) for connecting to the strengthening element connected to the sinker tube (120).

4. The fish cage (100) according to claim 3, wherein the upper attachment (152) is a lower end of a lifting rope (142), and the lower attachment (154) is an upper end of a cross rope,so that in a stable position, the upper substantial vertical leg (210) is substantially coaxial with the lifting rope (142), and the lower inclined leg (220) is substantially coaxial with the cross rope (144) along the bottom part (134) of the fish bag (130).

5. The fish cage (100) according to claim 3 or 4, wherein the first attachment means of the intermediate strengthening element (200) is a line spliced into the upper inclined leg (220).

6. The fish cage (100) according to one of claims 3 - 5, wherein the intermediate strengthening element (200) further comprises a second attachment means (212) for connecting to a lifting line (214) for raising the sinker tube (120) with the fish cage (100).

7. The fish cage (100) according to claim 6, wherein the second attachment means (212) of the intermediate strengthening element (200) is a line spliced into the lower inclined leg (220).

8. The fish cage (100) according to claim 6 or 7, wherein the second attachment means (212) is also connected to the strengthening element connected to the sinker tube (120).

9. The fish cage (100) according to one of claims 4 - 8, wherein the lifting rope (142), the upper substantial vertical leg (210), the lower inclined leg (220), and the cross rope (144) is formed by one continuous line.

10. The fish cage (100) according to one of the above claims, wherein the panel (136) is made from a different material from at least one of the upper vertical wall (132) and the bottom part (134) of the fish bag (130).

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