EP2101566A1

EP2101566A1 - Apparatus for the cultivation of shellfish

Info

Publication number: EP2101566A1
Application number: EP07856912A
Authority: EP
Inventors: Pieter Van Ysseldijk
Original assignee: Navital (UK) Ltd
Current assignee: Navital (UK) Ltd
Priority date: 2006-12-23
Filing date: 2007-12-19
Publication date: 2009-09-23
Also published as: GB0625899D0; WO2008077562A1

Abstract

A net for cultivating shellfish, the net comprising first and second parts (311A, 311B), each part having at least two open mouthed net portions (20,366). The net is pivotable into and out of a closed state in which the respective mouth of the net portions of the first part are substantially- facing and in register with the respective mouth of a respective net portions of the second part to form a plurality of net pockets (366). The net is suitable for use in a shellfish cultivation system comprising a mooring line (152), wherein a plurality of nets are coupled to the mooring line.

Description

Apparatus for the Cultivation of Shellfish

Field of the Invention

The present invention relates to apparatus for the cultivation of shellfish, particularly bi-valve molluscs, and especially mussels.

Background to the Invention

It is known to cultivate mussels by suspending ropes or nets in a water column. Typically, a system of anchored buoys act as floats on the water surface. To these, nets or lines are attached directly or via a head rope. The nets or lines serve as substrates on which mussel seed may be collected and on which mussels may be grown. Disadvantages with this type of farming include: adverse weather conditions can cause agitation of the nets/ropes leading to loss of mussels/seed; time consuming harvesting methods; and vulnerability of stock to predators.

It would be desirable to provide a system that mitigates these problems.

Summary of the Invention

A first aspect of the invention provides a net for cultivating shellfish, the net comprising first and second parts, each part having at least two net portions, each net portion having an open mouth, the net being operable into and out of a closed state in which the respective mouth of the net portions of said first part are substantially facing and in register with the respective mouth of a respective net portion of the second part to form a plurality of net pockets.

The net is particularly intended for use in cultivating shellfish, especially mussels, although it may also be used for other marine or sub-sea purposes, for example to house or shelter fish or other marine creatures. The preferred net has an in-use bottom end and an in-use top end, the net pockets being stacked in a first axial direction extending between said top and bottom ends.

Preferably, the first and second parts are pivotably coupled to one another at a first side of the net such that said first and second parts are pivotable about an axis that is substantially parallel with said first axial direction.

Advantageously, in a first open state, the cross sectional shape of the net taken in a plane substantially perpendicular with said first axial direction is substantially circular. To this end, in the closed state, the cross sectional shape of the net taken in a plane substantially perpendicular with said first axial direction, may be substantially oval.

Preferably, in the closed state, said first and second parts fit together to form a substantially tubular body, said first and second parts including at least one divider for dividing said body to form said net pockets.

A second aspect of the invention provides a shellfish cultivation system comprising at least one net, preferably but not necessarily a net according to the first aspect of the invention, and a mooring line, the or each net being coupled to the mooring line.

Each net is preferably independently connectable to and re leasable from the mooring line, for example by means of at least one flexible and substantially non- rigid connecting line.

The in use bottom end of the net may be coupled to the mooring line, at least one float being provided on or connected to the net and arranged to urge the net to adopt, during use, an orientation in which said first axis is substantially vertical. The mooring line is typically connected between first and second anchors, the mooring line being dimensioned to provide enough slack to allow a portion of the mooring line to be passed over a vessel located on the surface of the water in which the system is installed. Conveniently this may be achieved without having to lift, or preferably still even to dislodge the anchors.

A further aspect of the invention provides a net including frame comprised of a plurality of frame components, each frame component carrying a respective portion of netting, wherein the frame is foldable along at least one axis from and into a closed state in which at least one respective pair of frame components are in face-to-face engagement and their respective net portions form a netting pocket.

Preferably, each frame component is pivotably connected to the, or each, adjacent frame component about respective substantially parallel axes.

Preferably, at least some of said frame components carry one or more catch member, for example a hook, for engagement with another frame member in the closed state.

Preferably, the net portions are formed wholly or partially from a semi-rigid netting material, or other reticulated material.

The mooring line is typically provided with one or more anchors and/or one or more weights and, preferably, at least one marker buoy. The or each net advantageously carries one or more floats arranged to urge the net to adopt a substantially vertical orientation in use.

In use, the mooring line lies at the bottom of a body of water and the or each net is disposed at or adjacent said bottom, or the water surface, or in the intermediate water column, depending on the length of one or more connecting lines provided between the or each net and the mooring line.

Further advantageous aspects of the invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments and with reference to the accompanying drawings.

Brief Description of the Drawings

Embodiments of the invention are now described by way of example and with reference to the accompanying drawings in which like numerals are used to indicate like parts and in which:

Figure 1 is a perspective view of a net apparatus embodying one aspect of the present invention, the net being shown in an open state;

Figure 2 is an alternative view of the net apparatus of Figure 1 shown in a closed state;

Figure 3 is a perspective view of an alternative embodiment of the net apparatus (excluding netting), part of which is shown, for illustration purposes, in a closed state and part in an open state;

Figure 4 is an enlarged view of part of the net apparatus of Figure 3;

Figure 5 is a side view of part of the net apparatus of Figure 3;

Figure 6 is a perspective view of a further alternative embodiment of a net apparatus (excluding netting); Figure 7 is a schematic view of a cultivating system embodying a further aspect of the invention, the system being shown in situ and comprising a plurality of nets embodying the first aspect of the invention;

Figures 8A and 8B show further schematic views of the system of Figure 7 shown in situ together with a fishing vessel;

Figure 8C shows an aft view of the fishing vessel;

Figure 9A shows a perspective view of a preferred net apparatus embodying the first aspect of the invention;

Figure 9B shows a perspective view of part of the net of Figure 9A;

Figure 9C shows an end view of the net of Figure 9A in a closed state;

Figure 9D shows an end view of the net of Figure 9A in an open state; and

Figures 1OA to 1OD show the net of Figure 9A with preferred lifting harnesses.

Detailed Description of the Drawings

Referring now to Figures 1 and 2 of the drawings, there is shown, generally indicated as 10, a net apparatus, or net, embodying the invention. The net 10 comprises a frame 12 and netting 14. The frame 12 comprises a plurality of frame components 16 which, in preferred embodiments, are substantially rectangular in shape. In Figures 1 and 2, the frame 12 comprises four frame components 16 by way of example. More generally, the frame comprises at least two and preferably at least four frame components 16. Each frame component 16 is connected to one or more adjacent frame components 16 at or along a respective side. In the present embodiment, the connection is such that adjacent frame components 16 are capable of pivoting, or being folded, with respect to one another about an axis that is substantially parallel with the connected sides. In the embodiment of Figures 1 and 2, the pivotable connection is provided by binding the adjacent sides together using wire 18, clips 19 and/or other binding material or devices.

One or more lugs 21, or other attachment members, may be provided on the frame 12 by which the net 10 may be suspended, grasped or tethered during its various modes of use as will be described in more detail below. In the embodiment of Figures 1 and 2, the lugs 21 are provided at the in use top and bottom ends of the frame 12 (see Figure 7 for in use orientation) but, in alternative embodiments, the lugs or other attachment members may be provided at one or both sides of the frame 12 (as viewed in Figure 7).

A respective portion 20 of netting 14 is fixed to each frame component 16, substantially covering the area defined by the frame component 16. The netting 14 is advantageously self-supporting, e.g. formed from a rigid or semi-rigid material, so that it may hold its shape in normal working conditions. By way of example, the netting 14 may be formed from a semi-rigid plastics coated polyester fibre grid of the type marketed under the trade mark AQUAGRJD by Ten Cate Nicolon. Each net portion 20 is shaped to define a cavity or basin, the mouth of which is defined by the respective frame component 16. It will be understood that the term "netting" as used herein is intended to embrace any reticulated material.

At least one side of each frame component 16 carries one or more catch device which, in preferred embodiments, takes the form of a hook 22. In the illustrated embodiments, one side of each frame component 16 is provided with two spaced apart hooks 22. The frame components 16 are arranged so that the hook-carrying side of one frame component 16 is pivotably connected to the non-hook carrying side of an adjacent frame component 16. Each hook 22 is arranged to catch and hold another frame component 16 when the frame 12 adopts a closed state. To this end, each hook 22 is positioned to curve towards the nearest adjacent frame component 16.

Figure 1 shows the net 10 in an open or, more particularly a semi-open, state. Figure 2 shows the net in the closed state in which the frame 12 is folded, conveniently at its mid-point, such that pairs of frame components 16 are brought into face-to-face engagement with one another such that the respective net portions 20 together form net pockets, or net compartments. Hence, in its closed state, the net 10 may be described as a pocket net. When frame components 16 are brought into face-to-face engagement with one another, the respective hooks 22 of one frame component 16 engage with the other frame component 16 to hold the net 10 in the closed state. Conveniently, the hooks 22 are shaped and arranged to catch the side of the other frame component 16. In preferred embodiments, the free end of each hook 22 is arranged to project in a direction that is substantially parallel with the plane in which the associated frame component 16 lies. In the preferred embodiment, the hooks 22 on either side of the location (indicated as A in Figure 1) at which the net 10 is folded when in the closed state face in substantially opposite directions so that the hook 22 of each frame component 16 can engage with the other frame component 16.

Figures 3 to 5 show an alternative embodiment of the net, generally indicated as 110. The net 110 is generally similar to the net 10 and a similar description applies, like numerals being used to indicate like parts. In Figures 3 to 5, the netting is omitted for reasons of clarity. Adjacent frame components 116 are pivotably connected together by means of clips 130 instead of wire, although it will be understood that any alternative pivotable connection means may be used.

In Figure 3, the upper part 132 of the net 110 is shown in the closed state, the remainder of the net 110 being shown in the open state for illustration purposes. From Figures 4 and 5, the interengagement of the hooks 122 and frame components 116 may clearly be seen.

Figure 6 shows a further alternative embodiment of the net, generally indicated as 210. The net 210 is generally similar to the nets 10, 110 and a similar description applies, like numerals being used to indicate like parts. In Figure 6, the netting and the connection between adjacent frame components 216 is not shown. In this embodiment, the hooks 222 are operable, by means of a respective lever 234 between a locking state, in which the hooks 222 hold two frame components 36 together, and an unlocked state, in which the frame components 216 are free to move apart. In the illustrated embodiment, each hook 222 is pivotably mounted to the frame component 216 by means of a bracket 236, and the lever 234 takes the form of an extension to the hook 222 by which the hook 22 can be rotated between the locking and unlocked states.

It will be apparent that the preferred configuration of the net 10, 110, 210 in which each frame component 16, 116, 216 is pivotably connected to the next, facilitates the handling of the net 10, 110, 210 during brushing, filling, transportation and storage. In alternative embodiments (not illustrated), however, it is not essential that each frame component is pivotably connected to each adjacent frame component. For example, the frame of the net may be provided with only one pivoting or folding joint, e.g. at its mid-point, the remainder of the frame components being rigidly connected to one another. This arrangement may be manageable in cases where the net comprises a relatively small number of pockets, say, two, four or six pockets, but may become unwieldy for nets with more pockets.

Referring now to Figures 9A to 9D, there is shown, generally indicated at 310, a preferred embodiment of a net apparatus, or net. The net 310 may be generally similar to the nets 10, 110, 210 and so a similar description applies, like numerals being used to indicate like parts. In this embodiment, the net 310 comprises a body 311 in which is provided at least one divider 313 in order to divide the interior of the body 311 into at least two compartments or pockets 366 (only half of each pocket 366 is shown in Figure 9B). Typically, a plurality of dividers 313 are provided and are preferably substantially parallely disposed, spaced apart along a first axis of the body 311 (typically the longitudinal axis of the body 311). Hence, the pockets 366 are stacked on top of one another in the first axial direction. The pockets 366 are substantially in register with one another to form a column. The body 311 is formed at least partially from reticulated material, such as netting, so that, during use, water is able to flow through the body 313 and through the pockets 366. The dividers 313 are preferably also formed from reticulated material such as netting. The reticulated material used for the body 311 and/or dividers 313 is preferably, but not necessarily, self-supporting, e.g. rigid or semi-rigid. The body 311 is typically closed at each end 319, 321, for example by a respective end wall which may or may not be reticulated. The body 313 is preferably takes the form of a tube, typically a tube that is closed at both ends.

In the illustrated embodiment, the body 311 comprises a first and a second part 31 IA and 31 IB which may be operated between a closed and an open state. Each part 3 HA, 31 IB comprises a respective frame 312 having a plurality of frame components 316. Each frame component 316 defines a respective mouth of a respective cavity, or basin, formed by a respective portion 320 of the body part 31 IA, 31 IB, and respective divider(s) 313. The body parts 31 IA, 31 IB preferably also include one or more ribs 315 projecting from the frames 312 to support the respective body part 311 A, 311 B and/or divider 313 as necessary. In the present embodiment, the dividers 313 are provided as separate components that may be, inserted into the body 311 and fixed in place by any suitable means. When the body 311 is in its closed state, the respective frames 312 come together in face-to-face engagement with one another such that respective pairs of body portions 320 form a respective pocket 366. In the illustrated embodiment, the dividers 313 and the walls of the pockets 366 as provided by the body 311 are all formed from reticulated material, although this need not necessarily be the case. In the closed state, the pockets 366 are substantially closed apart from the reticulations. Because of the preferred symmetry of the body parts, Figure 9 may be viewed as a representation of both of the body parts 31 IA, 31 IB.

The net 310 further includes means for releasably retaining the body parts 31 IA, 31 IB in the closed state. For example, one or more latches or other releasable fastening mechanisms (not shown), e.g. hooks or clasps, may be provided at one, or both, sides 317 of the body 311. Preferably, the first and second body parts 31 IA, 31 IB are pivotably coupled together at one side 317', for example by means of one or more hinges or other mechanism (not shown), the or each fastening mechanism being provided at the other side 317". Hence, the net 310 is able to open and close pivotably about an axis that is substantially parallel with said first axis, i.e. an axis running along one side 317' of the body 311. The pockets 366 may therefore be opened and closed simultaneously. In the preferred embodiment, each of the body parts 31 IA, 31 IB constitutes approximately half of the body 311. More particularly, each body portion 320 constitutes approximately half of the respective net pocket 366.

The transverse cross-section of the body 311, when closed, may take a variety of shapes, e.g. substantially circular or polygonal. However, it is preferred that the transverse cross section of the body 311 is substantially oval or elliptical in shape when closed (see for example Figure 9C). The arrangement is such that the body 311 may be opened into an open state (e.g. a partially open state as opposed to a fully open state) in which the transverse cross-section of the body is substantially circular (see for example Figure 9D). This facilitates the handling of the net 310 during harvesting since the net 311 is amenable to being rotated about its longitudinal axis when in said open state, and/or to being cleaned by rotatable circular brushes or scraping devices. To this end, the body 311 is preferably adapted to receive an axle 333 along its longitudinal axis when in said open state. This may be achieved by any suitable means, for example providing one or more bushings, or other axle seats, at suitable locations in the frames 312. In the present embodiment, bushings or the like are not shown as they are found not to be necessary - it is found that an axle can bear directly against, and between, the frames 312 when the body 311 is partially open. By way of example, the net 310 may be mountable on a cleaning apparatus (not shown) including the axle and means for causing relative rotation of the net 310 and the axle, or of causing rotation of the net 310 with the axle. The axle may carry one or more radially projecting brushes that act to remove the contents of the pockets 366 when the net 310 is rotated. Alternatively, the net 310 may be held static, while the brush(es) are rotated.

Figure 7 shows a plurality of nets 10, 110, 210, 310 combined with a mooring system to form a cultivation system 150 for shellfish, particularly bi-valve molluscs, and especially mussels. The mooring system comprises a mooring line or chain 152 which, in use, is laid on the bed 153 of a volume of water 154. One or more anchors and/or weights 156, 158 are provided on the mooring chain 152 to hold it in position. One or more surface marker buoys 160 are connected directly or indirectly to the mooring chain 152, by any convenient means, e.g. a line, in order to indicate its location.

The nets 10, 110, 210, 310 are connected, preferably releasably connected, to the mooring chain 152 by any suitable means, e.g. one or more lines 162, with, for example, one or more hooks (not shown), or other means for releasable connection to the net 10, 110, 210, 310 and/or the mooring line 152. The lines 162 are typically flexible and not rigid or semi rigid, and may for example comprise ropes or chains 162. Each net 10, 110, 210, 310 carries one or more floats 164 for urging the nets 10, 110, 210, 310 to be disposed substantially vertically in the water column during use (or substantially perpendicular with the sea bed). Conveniently, the float(s) 164 are located at the in use top end of the nets 10, 110, 210, 310 the chains 162 being provided at the in use bottom end of the nets 10, 110, 210, 310. The float(s) 164 may be removable to facilitate processing of the nets after harvesting.

In a preferred mode of use, the nets 10, 110, 210, 310 adopt the closed state when disposed in the water column, i.e. during the cultivation process. The nets 10, 110, 210, may be partially closed whereby only some of the frame components 16, 116, 216, are held in face-to-face engagement to form compartments, or pockets (as, for example, illustrated in Figure 3). More typically, however, the nets 10, 110, 210, 310 adopt a fully closed state in which all of the frame components are paired with another frame component to form a respective net pocket. Advantageously, the arrangement is such that the net pockets are substantially horizontally disposed (or at least substantially parallel with the sea bed), and, preferably, stacked one on top of the other.

Preferably, the arrangement is such that the location at which the net 10, 110, 210 is folded is uppermost in the water column, the free ends (when open) of the frame 12, 112, 212 being lowermost in the water column. In this orientation, the hooks 22, 122, 222 hold the nets 10, 110, 210 in the closed state during the cultivation process.

By selection of the length of the chains 162, the nets 10, 110, 210, 310 may be disposed on or adjacent the sea bed, adjacent the sea surface, or elsewhere in the water column. Preferably, the floats 164 are selected with buoyancy that is just sufficient to keep the nets 10, 110, 210, 310 in a substantially vertical (or perpendicular) position. It is further preferred that the length of the chains 162 is such that the floats 164 are not visible on the water surface. Typically, approximately 30 nets 10, 110, 210, 310 are attached to the mooring chain 152 which may be approximately 120 metres long.

In a typical mode of use (illustrated in Figure 8A), the nets 10, 110, 210, 310 rest on the sea bed 153 under their own weight and/or by virtue of the line(s) 162 or other means connecting them to the mooring line 152. The float(s) 164 are selected to create a buoyancy that is sufficient to urge the nets to adopt a substantially vertical orientation, but not to lift the nets off the sea bed.

It will be apparent that the net 310 is also suitable for use with the cultivation system 150 and so that foregoing description applies equally to the net 310 as will be apparent to a skilled person. To this end, the net 310 may include means for enabling it to be releasably connected to the mooring line 152. Conveniently, this comprises one or more of said lines 162, one end of which is connected or connectable to the net 310, the other end being connected to, or connectable to, the mooring chain 152. Typically, the line(s) 162 are connected in use to the lower end 319 of the net 310. One or more floats 364 are provided on the net 310, preferably at or adjacent the in use top end 321 of the net 310. The preferred arrangement is such that, during use, the longitudinal axis of the net 310 is disposed substantially vertically under the action of the floats 364. Hence, the pockets 366 are stacked in a substantially vertical direction. The actual orientation of the nets 310 may be affected by the number of, and or arrangement of the lines 162, and/or on the orientation of the line 152, although the floats 364 always act to urge the net upwardly, or at least to adopt a substantially vertical orientation. Preferably, the line(s) 162 are arranged to allow the net 310 to adopt a substantially vertical orientation, and typically an orientation in which the first axial direction is substantially perpendicular to the mooring line 152.

In preferred embodiments, the two parts 31 IA, 31 IB of the net 310, or the corresponding parts of the nets 10, 110, 210 each constitute substantially half of the net, each part being similarly shaped and dimensioned to the other. Preferably, the two parts are substantially symmetrical about a plane that bisects, or substantially bisects, the net (or more particularly the net pockets), when closed, and along which said first axial direction, or the pivot axis, runs. More generally, where the net is comprised of two parts that can be opened and closed, the two parts are separated, when the net is closed, by a plane that intersects, and preferably substantially bisects, all of the net pockets. If possible, the plane may be located substantially at or parallel with the longitudinal axis of the net pockets. This facilitates the handling of the net, especially during filling and harvesting since all of the pockets can be opened at once. In alternative embodiments, where the net comprises more than two closable parts, it is preferred that each part is of substantially the same shape and dimensions.

Referring now in particular to Figures 8A to 8C, an example of how the nets 10, 110, 210, 310 may be harvested is described. A fishing vessel 170 has a gantry 172 typically located aft of the vessel 170. The gantry 172 is located at or adjacent one end of a storage area or deck 176 for receiving the nets 10, 110, 210, 310. The gantry 172 is provided with one or more line handling devices 178, e.g. winches and/or pulleys, to assist in lifting nets onto the deck 176. The device 178 preferably includes an automated winch or hauling device, for example a hydraulic hauler. A line guide 174 may also be provided aft of the vessel 170. The hauling device is cooperable with the handling device 178 to reel in the line 152 and attached nets. A lifting device, e.g. a crane 180 is provided to lift the nets, once they are detached from the line 152, onto the deck 176.

In use, the mooring line 152 is coupled to the winch 174 which hauls the line 152, and therefore the nets 10, 110, 210, 310, up onto the vessel 170. It is noted that, as each net 10, 110, 210, 310 is lifted, and especially when it leaves the water, it adopts an inverted orientation in comparison to its orientation when underwater. In the inverted orientation, the hooks 22, 122, 222 lend themselves to being disengaged and this facilitates opening the nets 10, 110, 210 if desired.

Preferably, the line 152 is capable of being passed through the line handling mechanism without having to remove or disturb the anchors. To this end, it is preferred that the line 152 is dimensioned to provide slack while the system 150 is in situ, the slack being sufficient to allow the line 152 to be lifted and passed through the line handling mechanism 174 in the manner described above. Referring now to Figures 1OA to 1OD, the net 310 is shown with lifting harnesses. Figure 1OA shows a first lifting harness 369, which embraces the net 310 in the closed state. The preferred harness 369 comprises a plurality of lines 371 that run longitudinally around the net 310 between a respective common hub 373, 373 ' located in use at either end 319, 321 of the net 310, preferably substantially centred at the end 319, 321. The hubs 373, 373' may take any suitable form. The harness 369 also includes means for allowing it to be engaged by a lifting device (e.g. the crane 180). In the illustrated example, the hubs 373, 373' take the form of lifting eyes for this purpose, although it will be understood that lifting eyes or other lift-enabling devices may be provided elsewhere on the harness, preferably at one or both ends of the net 310. In the illustrated embodiment, four lines 371 extend between the hubs 373, 373' and are preferably substantially evenly spaced around the net 310. More or fewer lines 371 may be provided in alternative embodiments, preferably substantially evenly spaced around the net 310.

Preferably, a connecting line 162' is provided on the harness at the in use bottom end 319 of the net 310 (Figure 10B). The line 162' may for example be used to connect the net 310 to the mooring line 152. To this end, it may be provided with a hook, clasp or other coupling device 163 at its free end. The harness 369 may be used to lift the net 310 during use. The arrangement of the lines 371 distributes the load of the net 310 throughout the harness 369. By way of example, the crane 180 may use the lifting eye provided at the hub 373 at the bottom of the net 310. This allows the net to be attached or detached from the mooring line 152 using the tail 162'.

Referring now to Figures 1OC and 10D, a net opening device in the preferred form of a second harness 375 is provided, in use, around the net 310. The harness 375 comprises a respective line 377A, 377B for each part 311 A, 31 IB of the net, each line 377A, 377B having at least one first point of coupling 379A, 379B, or connection, to the respective part 311 A, 311 B at the side 317" at which the net 310 opens. The lines 377 are coupled together at a location 381 that is at, or substantially at, the other side 317' of the net 310, i.e. the side at which the net's pivot axis is located. One or more loops or other couplings (not shown) may be provided along the desired path of the lines 377A, 377B to hold them in place. A lift-enabling device, which may for example comprise a lifting eye 383 or other suitable device, is provided at the coupling location 381. The arrangement is such that, when the net 310 is lifted by the eye 383, tension in the lines ?>11K, 377B caused by the weight of the net 310, causes the net 310 to open (as shown in Figure 10C), provided the fastening mechanism(s) are released. This facilitates the handling of the net 310 during, for example, filling and emptying.

The harness 375 shown in Figures 1OC and 1OD is a preferred version in which each line 377A, 377B has its ends connected to a respective end 319, 321 of the net 310, preferably at or adjacent the side 317", and is fed over the net 310 substantially along the other side 317'. A tube 385 or other coupling device is provided at the coupling location 381 in order to couple the lines 377A, 377B together. The lifting eye 383 is attached to the tube 385. The lines 377A, 377B may alternatively be directly transversely around the net 310. The harness may include more than one line for each part of the net.

The lines 371, 377 may take any suitable form, for example ropes or chains.

Harnesses similar to the harnesses 369, 375 may be used with any other net embodying the invention.

The apparatus and system described herein are particularly suited for farming and processing large quantities of live shellfish using suspended culture with relatively limited manual labour. They allow for offshore farming in locations which are not amenable to traditional mussel farming techniques. The technology can be used for purifying shellfish offshore thereby avoiding expensive onshore purification. The nets can be used for seed collection of shellfish in the water (typically with a suitable inner lining provided within the netting), or for the storage and purification of any size of shellfish in the water column (where the shellfish are very small, a suitable inner lining may be provided), or for the growing of shellfish in the water. The nets may also be used for the transport of shellfish on board a vessel from the farm to a processing factory and vice versa, and for the transport of shellfish in any other vehicle. The nets may be used generally for the storage of shellfish in, for example, a processing factory.

Moreover, the nets are well suited to automated harvesting and filling of shellfish in a processing factory.

When used for seed collection purposes, the seed can be brushed from each pocket 166, 366 and either graded and kept in the same pocket 166, 366, or placed in other pocket net, for further growing. Alternatively, the nets, together with their contents, can be carried by the fishing vessel and taken to sheltered locations for bottom culture for, for example, bottom culture mussel growing. The nets may be cleaned on board the vessel and can also be filled on board by shellfish from extensive culture territories.

The pocket nets may alternatively be processed in a factory and, after brushing, can be filled in the factory again and moved back to an offshore location for growing purification purposes.

The nets can be raised or lowered in the water column either by adjusting the lengths of the lines 162, or by changing the floats.

During use, the nets may be placed adjacent the sea bed for at least 40 weeks of the year. Only during seed collection are the nets typically suspended at the water surface. As a result, damage to the equipment caused by, for example, sea going vessels, adverse weather conditions, surface current, ice etc., can be avoided.

Loss of shellfish resulting from turbulence in the water and/or predators is reduced because of the provision of closed pocket nets and the positioning of the nets in the water column. Moreover, because the mooring system is usually submerged it does not contribute to "visual seascape pollution," nor does it present a hazard in environmentally sensitive and/or busy locations.

In one embodiment, by using a submerged marker buoy, capable of surfacing on demand by means of, for example, an acoustic pulse from the surface vessel, the mooring system can continue to operate under, for example, an ice layer without being damaged or displaced by the drift of ice.

The system creates the possibility for both sea ranching of shellfish, for example crustaceans (e.g. lobster, crabs or prawns), as well as sheltering endangered fish species.

The invention is not limited to the embodiments described herein which may be modified or varied without departing from the scope of the invention.

Claims

CLAIMS:

1. A net for cultivating shellfish, the net comprising first and second parts, each part having at least two net portions, each net portion having an open mouth, the net being operable into and out of a closed state in which the respective mouth of the net portions of said first part are substantially facing and in register with the respective mouth of a respective net portion of the second part to form a plurality of net pockets.

2. A net as claimed in claim 1, wherein the net has an in-use bottom end and an in-use top end, the net pockets being stacked in a first axial direction extending between said top and bottom ends.

3. A net as claimed in claim 1, wherein said first and second parts are pivotably coupled to one another to allow the net to be operated into and out of the closed state.

4. A net as claimed in claim 2, wherein said first and second parts are pivotably coupled to one another at a first side of the net such that said first and second parts are pivotable about an axis that is substantially parallel with said first axial direction.

5. A net as claimed in claim 4, wherein, in a first open state, the cross sectional shape of the net taken in a plane substantially perpendicular with said first axial direction is substantially circular.

6. A net as claimed in any one of claims 2, 4 or 5, wherein, in the closed state, the cross sectional shape of the net taken in a plane substantially perpendicular with said first axial direction, is substantially oval.

7. A net as claimed in claim 5 or 6, wherein, when in said first open state, the net is adapted to receive an axle such that the axle is located substantially centrally of the net and disposed in said first axial direction.

8. A net as claimed in any preceding claim, wherein, in the closed state, said first and second parts fit together to form a substantially tubular body, said first and second parts including at least one divider for dividing said body to form said net pockets.

9. A net as claimed in any preceding claim, wherein said first and second parts include a respective frame comprised of a plurality of frame components, each frame component providing the mouth of a respective net portion, wherein in the closed state, at least one respective pair of frame components are in face-to-face engagement and their respective net portions form a respective one of said net pockets.

10. A net as claimed in claim 9, wherein each frame component is pivotably connected to the, or each, adjacent frame component about respective substantially parallel axes.

11. A net as claimed in claim 9 or 10, wherein at least some of said frame components carry one or more catch member for engagement with another frame member in the closed state.

12. A net as claimed in any preceding claim, wherein the net portions are formed at least partially from a reticulated material, preferably a rigid or a semi-rigid netting material.

13. A net as claimed in claim 8, wherein the, or each, divider is formed at least partially from a reticulated material, preferably a rigid or a semi-rigid netting material.

14. A net as claimed in any preceding claim, wherein one or more floats are provided on or connected to the net, preferably at, or adjacent, the in use top end of the net.

15. A net as claimed in any preceding claim, wherein means for coupling the net to a mooring line are provided on the net, preferably at or adjacent the in use bottom end of the net.

16. A net as claimed in any preceding claim, in which the respective net portions of said first part are substantially the same shape and dimensions and the respective net portions of said second part.

17. A net as claimed in any preceding claim, in which a harness is fitted to the net, the harness comprising at least two radially spaced apart lines extending around the net, preferably longitudinally around the net, and at least one coupling device by which the harness can be engaged.

18. A net as claimed in any preceding claim, in which a net opening device is fitted to the net, the net opening device comprising a respective line for each part of the net, each line having at least one first point of coupling to the respective part, preferably at the side at which the net opens, the lines being coupled together at a location that is at, or substantially at, the side of the net at which the net's pivot axis is located.

19. A system for cultivating shellfish, the system comprising at least one net as claimed in any preceding claim, a mooring line, and means for coupling the or each net to the mooring line.

20. A system as claimed in claim 19, wherein each net is independently connectable to and releasable from the mooring line.

21. A system as claimed in claim 19 or 20, wherein the coupling means comprises at least one flexible and substantially non-rigid connecting line.

22. A system as claimed in any one of claims 19 to 21, wherein the coupling means is arranged to allow the net to adopt an orientation in which said first axis is substantially perpendicular with the mooring line.

23. A system as claimed in any one of claims 19 to 22 when dependent on claim 2, wherein the in use bottom end of the net is coupled to the mooring line, and wherein at least one float is provided on or connected to the net and arranged to urge the net to adopt, during use, an orientation in which said first axis is substantially vertical.

24. A system as claimed in any one of claims 19 to 23, wherein the mooring line is connected between first and second anchors, the mooring line being dimensioned to provide enough slack to allow a portion of the mooring line to be raised to a vessel located on the surface of the water in which the system is installed.