EP0961544A1

EP0961544A1 - Assembly for floating cages for fish

Info

Publication number: EP0961544A1
Application number: EP98901590A
Authority: EP
Inventors: Kjell Midling; K Re Aas; Svein H. J RGENSEN
Original assignee: Refa AS
Current assignee: Refa AS
Priority date: 1997-01-20
Filing date: 1998-01-16
Publication date: 1999-12-08
Also published as: NO970233A; NO970233D0; WO1998031217A1; CA2276739A1; NO303313B1

Abstract

Floating rings (1) with wires (3) fastened to a bottom ring (4), and a trampoline base (5) with tension mechanism (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22). A lift ring (12) which may be connected to compressed air supply, and a ballast block (21).

Description

ASSEMBLY FOR FLOATING CAGES FOR FISH

The present invention relates to a solution for flat-bottom floating cages for stocking live fish and farming of such species as flounder, halibut, catfish and any other flatfish requiring flat-bottom cages. Fish farming has nowadays become a major industry. The main volume and revenues come today from farming various species of salmonidae such as salmon itself and char. Research has subsequently provided useful knowledge for farming and raising of other species such as cod fish in which the industry has developed an interest and anticipates substantial financial profit. The new species which seem to be of significant economic interest for the future are the flatfish species. Halibut, plaice and turbot are the species which seem to awaken the greatest interest for future fish farming. These are demersal species, living and feeding on the sea bed. Most of the time, such fish lie immobile on the sea floor. Research and experience in farming of such species is restricted to raising in troughs or tanks. Troughs are shallow, open channels filled with running water, in which halibut remain on the bottom. Such troughs are suitable for small fishes only, and another solution must be found for the farming of halibut to marketable size. Experiments have also been made with round tanks to provide a larger base area and reduce the space occupied by the tank. One type of fish cage providing a flat base is called the AMY cage. It is built with a chequered framework of floating elements on top of which catwalks are provided. Inside each square is placed a fish pen, around the lower periphery of which are attached several lateral tension ropes connected to a main rope which is anchored to a ballast block and a float. In this manner, the fish pen is stretched sideways and an approximately flat base area is formed. This method of flattening the bottom of a pen does not provide the tension necessary to obtain a sufficiently flat and stable base area which can be used for raising flatfish and similar species. Such farming methods will hardly be financially profitable and will not be suitable for large-scale farming. It is therefore necessary to abandon the idea of land-based fish farming and turn to offshore farming. It is then natural to contemplate options utilizing fish cage structures which can resolve the problem. One such solution can be to use flat-bottom cage structures.

Captured cod fish which will later be used for raising or to be stocked as live fish, may suffer from a blown up swimming bladder when it is brought too rapidly up to the surface from the deep. A blown up swimming bladder is however a reversible process and the bladder may be restored to its original state if the fish is allowed to rest on a flat base for one or two days. The cod then becomes pelagic and can be transferred to an ordinary fish cage. The object of the present invention is to: - enable acclimatization of freshly caught live fish before transfer to conventional cages

- stock wild fish such as plaice, sole and catfish which do not possess a swimming bladder

- satisfy the requirements for raising flatfish such as halibut, plaice, turbot and the like, as well as catfish.

This is achieved with the help of a floating ring to which wires are attached by one of their extremities while the other extremity is fastened to a bottom ring with trampoline base. A fish pen is suspended to the floating rings, is further secured to the wires and rests on the trampoline base and a tension mechanism. Further details of the invention appear from the following description of a preferred embodiment of the invention with reference to the illustrations.

Figure 1 illustrates the various parts composing the invention.

Figure 2 shows the suspension system of the fish pen to the frame structure.

Figure 3 illustrates the wave-reduction system of the invention. Figure 4 illustrates the tension mechanism for the base net and the lifting mechanism for the base. Figure 5 illustrates details of the lifting mechanism for the base Figure 6 shows details of the tension mechanism and of the locking system The various components of the cage structure appear on figure 1 The structure is composed of two floating rings 1 which consist of two tubes each shaped in a ring, the two rings being of unequal diameters so as to float next to each other on the surface A number of suspension wires 3 are regularly positioned around the periphery of the floating rings 1 and fastened to it Their opposite extremity, which falls below the floating rings 1 down in the sea, is fixed to a bottom ring 4, approximately corresponding to the floating rings 1 A trampolinelike net made up of several parts, the trampoline base 5, is stretched across the inside of the bottom ring 4. The fish pen 2 is a flat -bottom net which is suspended to the floating rings 1 and rests on the trampoline base 5 The fish pen 2 is attached to the wires 3 in such a manner as to slide vertically along those Thus, under normal use, the pen 2 remains stable inside the frame structure composed of the floating rings 1, the wires 3 and the trampoline base 5 The base of the fish pen 2 can be lifted up towards the floating rings 1 as it slides inside said frame structure in a controlled manner Figure 2 shows details of the suspension system for the fish pen 2 to the wires 3 with the help of slide rings 6 Figure 3 illustrates how the wires are longitudinally mounted in a rubber-moulded spring system 7 of a known design This system acts as an elastic arrangement and provides a reduction of any wave effect which might propagate from the floating rings 1 to the rest of the structure Figure 4 illustrates how the trampoline base 5 is mounted and stretched in order to remain flat. The trampoline base 5 is in the shape of a circular disc and is fastened to the bottom ring 4 along its outer circumference It is not made of one single net, but of four quadrant-shaped pieces of net The right-angle corners of the four net quadrants are assembled together over and inside a central ring 8 which is provided under the trampoline base 5 This central ring 8 is a part of the tension mechanism for the trampoline base 5, the details of which appear on figure 6 The tension mechanism is designed in the shape of a vertical cylinder Starting from a number of stay attachment lugs 9 positioned around the outer edge of the central ring 8, a first set of stays 10 is stretched over to a stay ring 11 This stay ring 1 1 consists of two circular tubes, one inner ring 11 ' and one outer ring 1 1", one of the rings being of a somewhat larger diameter than the other Furthermore, the inner ring 11' and the outer ring 11" are positioned at a small distance from one another with the help of spacers 12 These may be made of rope The first set of stays 10 is fixed to the inner ring 11' From the outer edge of the outer ring 1 1", and positioned regularly around said edge, a second set of stays 13 is stretched over to the bottom ring 4 and continues, passing through turnbuckles 14, to stay lugs 9 provided on a base ring 15 which is situated on the opposite side of the tension mechanism relative to the central ring 8 The bottom ring 4, the stay ring 1 1, the first set of stays 10, the second set of stays 13 and the turnbuckles 14 constitute altogether a rig which stretches the tension mechanism in the centre of the bottom ring 4 and under the trampoline base 5

The tension mechanism is further described in detail with reference to figures 4 and 6 The right-angle corners of the four net pieces which constitute the trampoline base 5 are assembled together in the centre of the bottom ring 4, and further brought inside and down into the central ring 8 The corners of said net pieces are firmly attached to a chain 18 which itself constitutes a part of the tension mechanism The corners of the net pieces can, as an option, be directly fastened to the tension mechanism without the help of the chain 18 Closest to the trampoline base 5, the tension mechanism comprises the previously mentioned central ring 8

Between said central ring 8 and the base ring 15, several vertical rods 16 are mounted A flat frame ring 17, mobile along these rods 16, is provided, to which the opposite extremity of the chain 18 is fastened A tension wire 19, fixed to the frame ring 17 in the opposite direction to the chain 18, is connected to a winch 20 The latter is situated on the opposite side of the base ring 15 relative to the frame ring 17. To the base ring 15 is fastened a ballast block 21 which floats over the sea bed and stabilizes the cage in the water. Another stabilizing system for the cage could be to attach chains to the bottom ring 4 and let the free extremities of the chains lie on the sea bed, to the side of the cage.

When the trampoline base 5 is to be stretched to the correct tension in order to obtain a flat bottom, the winch 20 is actuated to tighten the tension wire 19 fastened to the frame ring 17, the chain 18 and the right-angle corners of the trampoline base 5. When the correct tension has been achieved, tie bars 22 are mounted between the frame ring 17 and the base ring 15. Stretching a net by drawing its centre downwards is more effective than for example stretching the outer edge of the net over the bottom ring 4. This method provides adequate tension to give a flat bottom, and, in addition, the central ring 8 remains in the horizontal plane, as does the bottom of the net, permitting the centre of the trampoline base to be locked in the correct position.

As mentioned above, the trampoline base 5 may consist of four quadrant- shaped pieces. The net used will therefore need to be stronger towards the centre of the trampoline base 5. This can be achieved by using yarn of a larger cross section or by decreasing the mesh. An alternative embodiment of the trampoline base 5 may be net pieces consisting of sectors of a circle meeting in the centre and being stretched.

On the side away from the trampoline base 5, a sausage-like, ring-shaped lift ring 23 is provided. This consists of a tubular circular bellows wrapped in a tubular net of a diameter somewhat inferior to that of the bellows in order to avoid irregular inflating of the bellows which may cause uneven buoyancy. The lift ring 23 is positioned between the inner ring 11' and the outer ring 1 1" and in contact with those. It can be filled with compressed air.through a hose 25 connected to the surface, thus providing a certain effect of buoyancy. When filling this lift ring 23, the whole bottom ring of the cage and the base of the fish pen 2 can be lifted towards the surface. This will be necessary when handling and collecting the fish which is, for example, ready for killing.

One of the major intentions behind the present floating cage structure is to achieve the largest possible surface, as the volume will not be the most important parameter for the species for which the cage is intended.

The cage system can be equipped with a false bottom 24 consisting of a net stretched over a circular tube, i.e. a tension tube. This is positioned horizontally somewhere between the base of the fish pen 2 and the floating rings 1. Its purpose is to enable observation and monitoring of fish behaviour, for example by feeding the fish and thus force it to swim up from the base of the pen 2 and on to the false bottom 24. In this manner, it will be possible to discover any dead individuals.

Claims

1. Assembly for floating cage for fish c h a r a c t e r i z e d b y a floating ring (1) to which wires (3) are attached by one of their extremities while the other extremity is fastened to a bottom ring (4) with trampoline base (5), a fish pen (2) being mounted so as to slide vertically along the wires (3) and being suspended from the floating ring (1), further mounted to the wires (3) and resting on the trampoline base (5), and a tension system (8, 9, 10, 11, 12, 13, 14, 15, 16,

17,18, 19,20,22).

2. The assembly for floating cage for fish of claim 1 characterized in that the trampoline base (5) has a circular circumference and consists of four quadrant-shaped parts, being made of thicker yarn and/or narrower mesh towards the centre.

3. The assembly for floating cage for fish of claim 1 characterized in that the trampoline base (5) is made up of several parts in the shape of sectors of a circle, being made of thicker yarn and/or narrower mesh towards the centre.

4. The assembly for floating cage for fish of claims 1, 2 and 3 characterized in th t the trampoline base (5), with its circular circumference is fastened to the bottom ring (4) and the centre of the net pieces lies above a central ring (8) and is fixed to a chain (18)..

5. The assembly for floating cage for fish of claim 6 characterized in that the central ring (8) is mounted on a base ring (15), both rings being positioned around the axis of the trampoline base (5), said rings being fastened to each other with the help of several rods (16), and between the central ring (8) and the base ring (15), sliding on the rods (16) a circular, flat frame ring (17) is mounted to which the chain (18) is secured and on which is fastened a tension wire (19) which stretches away from the trampoline base (5) and is further connected to a winch (20). 6 The assembly for floating cage for fish of claim 7 characterized in that a first set of stays (10) is fastened to stay lugs (9) on the central ring (8), said first set of stays (10) being stretched over to a stay ring (11) which is situated between the centre of the trampoline base (5) and the bottom ring (4), and further, a second set of stays (13) is stretched from the stay ring (11), over the bottom ring (4) and after passing through turnbuckles (14), is fastened to lugs (9) provided on the base ring (15) 7 The assembly for floating cage for fish of claim 8 characterized in that the stay ring (11) consists of two separate circular tubes of different diameters, the inner ring (IT) and the outer ring (11"), separated by spacers (12)

8 The assembly for floating cage for fish of claims 8 and 9 characterized in that a lift ring (23) is provided at the level of the stay ring (11) on the side furthest away from the trampoline base (5), the lift ring (23) being a bellows- shaped tube wrapped in a net, the bellows being connected to a compressed air supply

9 The assembly for floating cage for fish of claim 7 characterized in th t the frame ring (17) can be secured to the base ring (15) with the help of tie bars (22)

10 The assembly for floating cage for fish of claim 1 characterized in that a false bottom (24) is provided inside the fish pen (2)