WO1996002132A1

WO1996002132A1 - Improvements in or relating to fish farms

Info

Publication number: WO1996002132A1
Application number: PCT/GB1995/001635
Authority: WO
Inventors: William James Lithgow; William George Miller; David Lincoln Thomlinson
Original assignee: Campbeltown Developments Limited
Priority date: 1994-07-13
Filing date: 1995-07-12
Publication date: 1996-02-01
Also published as: GB2304020A; NO970103L; NO970103D0; GB9414103D0; GB9700451D0

Abstract

There is disclosed a fish farm (100, 100') having a rotatable cage net (120, 120'). A major operational cost is the maintenance of nets which have to be routinely cleared of fouling and reanti-fouled. This procedure has disadvantages, for example, it disturbs the stock, involves heavy handling, leads to abrasion of the net and involves substantial cost. Accordingly the present invention provides a fish farm (100, 100') comprising a structure (105, 105') forming a pool (110, 110') within which a cage net (120, 120') can be suspended, wherein the net (120, 120') forms a closed volume and there are provided means for rotating the net (120, 120') within the pool (110, 110') so as to orientate any selected portion of the net (120, 120') out of the water at any given time.

Description

Improvements in or Relating to Fish Farms

This invention relates to fish farms, and in particular to a fish farm having a rotatable cage net .

A fish farm may be formed from a structure comprising a series of inter-connected box girders forming one or more pools, a cage net being provided within each pool to hold the fish. Conventionally the net is supported from handrails fixed to the structure and surrounding the pool.

A conventional net is open at the top, having four side facets and a bottom made of heavy mesh reinforced with ropes both at the edges and also sewn in horizontally at intervals to allow the depth of the net to be varied by reefing. The open top of the net is normally covered with a light predator net.

A major cost of operation is the maintenance of the nets which have to be routinely changed so that they may be cleared of fouling and re anti-fouled. This procedure has a number of disadvantages, for example, it disturbs the stock, involves heavy handling, leads to abrasion of the net and involves substantial cost, the net having to be returned to the manufacturer for re anti-fouling.

It is an object of the present invention to obviate or mitigate at least some of the disadvantages in the prior art hereinbefore described.

According to a first aspect of the present invention there is provided a fish farm comprising a structure forming a pool within which a cage net can be suspended, wherein the net forms a closed volume and there are provided means for rotating the net within the pool so as to orientate any selected portion of the net out of the water (at any given time) . The net may be substantially parallelepiped shaped.

In a preferred embodiment the net may be substantially cube shaped.

In this embodiment the selected portion may be a face of the cube, which face when selected may lie substantially horizontally above the water level .

Also, in this embodiment, the rotational means may be capable of rotating the net in either of two substantially horizontal axes each of which axes pass between opposing faces of the cube substantially midway thereupon.

Further, in this embodiment, there may be provided means for reefing the net horizontally and/or vertically.

Faces of the cube net may be retained together by retaining means (such as zips, laces and ties) so as to facilitate replacement of a face.

The structure may comprise an array of four pools.

Advantageously, the structure may be formed from trapezoidal box girders.

The net may be provided with one or more socks capable of collecting mortalities (dead socks) .

The rotation means may include a plurality of pulleys and endless ropes. The rotation may include a plurality of buoyancy chambers.

According to a second aspect of the present invention there is provided a net for use in a fish farm according to the first aspect. According to a third aspect of the present invention there is provided a method of maintaining a fish farm comprising the steps of: providing a fish farm comprising a structure forming a pool from which a cage net can be suspended; providing a net forming a closed volume; providing means for rotating the net within the pool so as to orientate any selected portion of the net out of the water (at any given time) ; selecting a portion of the net and moving the portion out of the water by the rotational means such that maintenance work can be carried out on the portion.

According to a fourth aspect of the present invention there is provided a fish farm comprising a structure forming a pool within which a cage net can be suspended, wherein the net is held in position, in use, by means external to the net.

Provision of such external positioning means dispenses with the need for a frame internal of the net.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, which are:

Fig 1 a partial perspective view of a fish farm according to a first embodiment of the present invention;

Fig 2 a plan view of the fish farm of Fig 1;

Fig 3 a side view of a control guide rope spacer for use in the fish farm of Fig 1;

Fig 4 a side view of the fish farm of Fig 1 with a cage net in a normal operational position; a side view of the fish farm of Fig 1 with the cage net being rotated between first and second normal operational positions;

a simplified perspective view of a cage net for use in the fish farm of Fig 1;

a sectional side view of a combined corner bracket/airlift body for use in the net of Fig 6;

a perspective view of an outer portion of the combined corner bracket/airlift body of Fig 7;

a perspective view of an inner portion of the combined corner bracket/airlift body of Fig 7;

a perspective view of the combined corner bracket/airlift body of Fig 7;

a perspective view to an enlarged scale of a bottom corner of the fish farm of Fig 1;

a perspective view of a corner bracket for use in the fish farm of Fig 1;

a side view to an enlarged scale of a Karabiner, endless rope and edge control guide rope forming part of the fish farm of Fig 1;

a side view of a vertical edge of the fish farm of Fig 1;

a partial perspective view of a fish farm according to a second embodiment of the present invention;

a partial sectional side view through the fish farm of Fig 15 ; Fig 17 a simplified perspective view of a cage net for use in the fish farm of Fig 15; and

Fig 18 a detailed view along on edge of the cage net of Fig 17.

Referring to Figs 1 to 14 there is illustrated a first embodiment of a fish farm according to the present invention, generally designated 100, comprising a structure 105 forming at least one pool 110 and having a deck 88. A cage net 120 can be suspended within the pool 110 from the structure 105. The net 120 forms a closed volume - namely, in this embodiment a cube. Means are provided for rotating the net 120 within the pool 110 so as to orientate any selected portion - namely a face - of the net 120 out of the water at any give time. When oriented out of the water the selected face lies substantially horizontally above the water level.

The rotational means, which will be described in greater detail hereinafter, are capable of rotating the net 120 in either of two substantially horizontal axes, each of which axes pass between opposing faces of the cube net 120 substantially midway thereupon. In this way any given face may be oriented uppermost. The net 120 is provided with rope edges 7 and to ensure symmetry intermediate reinforcing/reefing ropes 6, 10 run both horizontally and vertically. The net 120 comprises 6 square net panels 1 zipped, laced or tied together.

It is envisaged that the net 120 may be routinely rotated at periods of say twice per week such that at any one time one face is above water level, drying out in light and air. By this procedure fouling of the net 120 may be arrested and killed off. The top face meanwhile acts as a predator net. The means for rotating the net 120 will now be described in more detail. In this embodiment the rotational means also controls the shape and placement of the net 120. The rotational means comprises a system of panel control guide ropes 9, 11 external to sewn in panel reinforcement ropes 6, 10 and attached at the intercepts by figure of eight spacers 8. External to the cage net 120 are edge control guide ropes 5 equal in length to and duplicating the internal edge ropes 7. A rigid corner bracket 2 is built into each of eight corners of the net 120 and to each of which are attached three respective edge control guide ropes 5 through tubular horns 23 welded to edges of the bracket 2. A lifting eye 61 is incorporated into the corner bracket 2 to facilitate lifting and fixing of the net corners.

Each of the four top corners is attached via a snap shackle (Karabiner) 90 and rope 92 to corner gallows 80 provided on the structure 105 and tied off. Each top edge rope 7 is also attached to deck handrail horns 89 at, for example, 1.5 metre or 3 metre intervals. Each of the four bottom corners is tensioned down towards fixed weights 83 suspended on wires 82 from the structure 105. Tensioning is achieved by a Karabiner 25 attached to an endless rope 26 and clipped over a vertical edge control guide rope 5. The endless rope 26 runs over a top pulley 81 attached to the gallows 80 and a bottom pulley 84 attached to the fixed weight 83. By rotating the endless rope 26 the Karabiner 25 can be made to travel up and down the edge control guide rope and locate in a tubular horn 23 being part of a bottom corner bracket 2 or 3. Thus by pulling the Karabiner 25 down on the endless rope 24 the bottom corner of the net 120 can be tensioned towards the fixed weight 83 thus holding it firmly in position.

The procedure for rotation will now be described. Referring to Fig 4, to prepare for rotating by one facet (say anti¬ clockwise) fixed Karabiners 90 are arranged right-hand on right vertical edge control guide rope 5 and left-hand on top horizontal edge control guide rope 5.

Both endless rope Karabiners 25 are then brought to the top and released from the edge control guide ropes 5 freeing the bottom of the net 120.

The right-hand top corner bracket may then be lifted and attached to a span wire 91 between the gallows 80 by means of another Karabiner or pulley 87 thus keeping that net corner as high as possible.

The net 120 can then be rotated anti-clockwise by pulling the Karabiner or pulley 87 attached to the net corner bracket 2 along the span wire (shown at mid rotation - Figure 5) . It may be necessary to use the endless rope and Karabiners 25 on the right-hand vertical lower and left-hand horizontal edge control guide ropes 5 to 'follow' the rotation procedure and help maintain the net shape during tidal conditions when the shape may tend to collapse.

When the Karabiner 87 has been pulled fully along the span wire 91 the right-hand fixed Karabiner 90 is attached to the corner bracket 2. The travelling Karabiner 87 is released from the left-hand corner bracket 2 which is then lowered and the left-hand fixed Karabiner 90 attached to this bracket thus securing it in position.

The endless rope Karabiners 25 are attached to the vertical edge control guide ropes 5 and pulled down to secure the bottom corners of the net 120. The top edge ropes 7 are attached to the handrail horns 89 to secure the complete net 120.

When it is desired to reduce the depth of the net 120 for husbandry reasons the endless ropes 26 are initially slackened off. The net 120 is then reefed by lifting systematically on the vertical panel control guide ropes 9,

11 and hanging at the control guide rope intersects onto horns attached to the top of the handrails 89. Once the net

120 is at the desired depth the endless guy tension ropes are re-tightened to again hold the cage net 120 in shape.

To allow the mesh size to be changed or major repair work to be undertaken, a complete facet 1 can be removed and replaced since its edge ropes 7 may be attached to the adjacent panel edge ropes 7 by a lacing or releasable tie system.

Similarly if for husbandry purposes access is required to a limited area of the top of the cage net 120 a corner or rectangle can be opened in a flap.

In order to facilitate the removal of mortalities, three of the edge ropes 7 have attached to them internally a system comprising an air hose 44 and shut off selector valves 46, 47 with quick release coupling 45 at either end for connection of a compressed air line and a large diameter water hose 4 which is connected at each end to an airlift body 40 built into the corner bracket assembly 2. By surface connections an airlift can be induced at the bottom corner of the cage discharging the mortalities through a discharge hose connected to a top coupling 43 of the airlift body 2 into a portable dewatering trolley on deck. The cage net 120 can be manipulated by lifting the other three corners of the net 120 and inclining the base of the net 120 towards the airlift. Alternatively a 'dead sock' or pouch could be incorporated into each corner of the net 120 so that mortalities could be directed into this sock be inclining the net 120 and then rotating the net 120 to bring the sock to the surface.

As can be seen from Fig 7 the net 120 corners are provided with reinforcement ropes 22 laced to a corner bracket 2, 3. As can be seen from Fig 11 the fixed weights 83 are provided with stability arms 86. Further, between adjacent weights 83 are provided anti-rotation wires 85.

Referring now to Figs 15 to 18 there is illustrated a second embodiment of a fish farm according to the present invention. For ease of reference parts of the second embodiment will be identified by the same numerals as were used to identify like parts of the first embodiment but suffixed with an apostrophe ("'") .

The second embodiment of the fish farm 100' is similar to the first embodiment. However, in the second embodiment the endless ropes and pulleys 81, 84 have been dispensed with, and have been replaced with ballast/buoyancy chambers 226' moving up and down on the tensioned wires 82' . In this embodiment there are provided four chambers 126', one at each corner of the pool 110' .

The raising and lowering of the four chambers 126' is controlled (each independently) from a central control panel 200' . The fixed weights 83' are still fixed. The Karabiner 25' is attached by a short chain strap 205' to the chamber 226' and its operation of the vertical control guide ropes 5' is unchanged. Each chamber 226' may be supplied with compressed air via a hose 215' for evacuation of the buoyancy space therein and a catenary chain 210' serves to prevent the chamber 25' rotating, and keeps the air hose 215 clear of the tensioned wire 82' . The length of the chain 205' may also be carefully adjusted to provide a small horizontal force on the chamber 226' when fully down, thus moving the chamber 226' outwards to the side and splaying the net 120' slightly thus increasing the effective volume of the net 120 I

The net 120' of this second embodiment may be rotated in a similar manner to the net 120 of the first embodiment. In addition in this second embodiment, the lower corner of the net 120' may be raised during rotation by the following means. Prior to rotation at the corners to be raised, the two chambers 226' previously tensioning the net 120' underwater are raised to the surface. The Karabiners 25' are detached from the vertical edge control guide ropes 5', and onto those ropes 5' is attached a one-way rope cam cleat (similar in principal to a mountaineering "jumar") - not shown. The Karabiner 25' is attached to this cleat, and the chamber 226' is sent down pulling the cleat down the guide rope 5' . Now at the time of rotation when the other two chambers 226' will pull downwards on the above water corners, the chambers 226' attached to the guide ropes 5' by the cleat will be raised, and as the cleat is of one-way type it will grip the guide rope 5 ' at its lowest extent and thus pull the underwater corner upwards. Upon completing the rotation the cleat will be detached and the chamber 226' sent down again to tension the net 120' underwater.

The use of the four chambers 226' also provides for a very effective method of tensioning the net 120' underwater thus giving a much greater in-situ net volume than that given by conventional weighting arrangement on conventional nets.

Referring to Figs 17 and 18 an embodiment of the "dead sock" mentioned hereinbefore is illustrated. Along three edges of the net 120' (or as many as required) dead socks or gutter pouches 220' are provided which allow any dead fish to fall into a sock 220' during a rotation when the corner of the cube net 210' is at its low point. When the sock 220' is brought to the surface by the rotation process, the base of the sock 220' is opened by using a zip (or lacing etc) 225', and the operators remove the mortalities by hand. The mouth of the sock 220' is held open at all times by spacer members

225', but the sock 220' is effectively closed when the net 120' is in its static position or the socks 220' are rising/lowering from the surface due to the fact that as the net 120' sinks in water the sock 225' hangs vertically down and covers the mouth.

Referring to Fig 15 and 16 it can be seen that in this second embodiment the structure 105 ' comprises an array of four pools 110', the deck 88' providing walkways 230' between adjacent pools 110' . The structure 105' is fabricated from trapezoidal girders 235' which provide storage space 240' below walkways 230' .

The structure 105' may further be provided with a raised deck 240' suitable for supporting enclosed workspace, accommodation space, plant machinery and/or automated feeding apparatus.

The embodiments of the present invention hereinbefore described are given by way of example only and are not meant to limit the scope thereof in any way. It should particularly be appreciated that in the disclosed embodiments the cage net 120, 120' comprises 6 flexible faces, formed by net panels 1, 1', the net 120, 120' being held under tension, in use. Thus in the preferred embodiments of the invention the net 120, 120' is held in place without the use of a rigid frame. It should further be appreciated that by rotating a selected portion out of the water maintenance work may be carried out on said selected portion. Such work may merely involve allowing the sun to dry off the selected portion over a period of time.

Claims

1 A fish farm comprising a structure forming a pool within which a cage net can be suspended, wherein the net forms a closed volume and there are provided means for rotating the net within the pool so as to orientate any selected portion of the net out of the water.

2. A fish farm as claimed in claim 1, wherein the net is substantially parallelepiped shaped.

3. A fish farm as claimed in claim 1 or claim 2, wherein the net is substantially cube shaped.

4 A fish farm as claimed in claim 3, wherein the selected portion is a face of the cube, which face when selected lies substantially horizontally above the water level.

5. A fish farm as claimed in either of claim 3 or 4, wherein the rotational means are capable of rotating the net in either of two substantially horizontal axes each of which axes pass between opposing faces of the cube substantially midway thereupon.

6. A fish farm as claimed in any one of claims 2 to 5, wherein there are provided means for reefing the net horizontally and/or vertically.

7. A fish farm as claimed in any of claims 3 to 5 or claim 6 when dependent upon claim 5, wherein faces of the cube net are retained together by retaining means such as zips, laces or ties.

8. A fish farm as claimed in any preceding claim, wherein the structure comprises an array of four pools.

9. A fish farm as claimed in any of claims 1 to 8, wherein the structure is formed from trapezoidal box girders .

10. A fish farm as claimed in any preceding claim, wherein the net is provided with one or more dead socks.

11. A fish farm as claimed in any of claims 1 to 10, wherein the rotation means includes a plurality of pulleys and endless ropes.

12. A fish farm as claimed in any of claims 1 to 10, wherein the rotation means includes a plurality of buoyancy chambers.

13. A net for use in a fish farm according to any of claims 1 to 12.

1 . A method of maintaining a fish farm comprising the steps of: providing a fish farm comprising a structure forming a pool from which a cage net can be suspended; providing a net forming a closed volume; providing means for rotating the net within the pool so as to orientate any selected portion of the net out of the water; selecting a portion of the net and moving the portion out of the water by the rotational means such that maintenance work can be carried out on the portion.

15. A fish farm comprising a structure forming a pool within which a cage net can be suspended, wherein the net is held in position, in use, by means external to the net.