GB2549090A - Apparatus for rearing shellfish - Google Patents

Abstract

Apparatus 1 for rearing shellfish (lobsters) includes an enclosure having a base 3, a top 3 and a side wall 2. The side wall extends between the base and the top. The base and the top both have a substantially quadrilateral shape, preferably a rhombus. The side wall of the enclosure is perforated 7 to permit water flow through the enclosure. A first attachment device 11, 61 permits the enclosure to be attached, in use, to an underwater securing means (75, fig 11). The attachment device is located adjacent a first corner (20, fig 3) of the quadrilateral shape. Dividers may be provided to spilt the enclosures into compartments. Multiple enclosures may be provided one on top of the other. The side wall may be made up of multiple sections. Connecting and disconnecting the sections from one another allows shellfish to be inserted and removed.

Description

APPARATUS FOR REARING SHELLFISH

The invention relates to apparatus for rearing shellfish and especially but not solely, apparatus for rearing crustaceans, for example lobsters.

The Food and Agricultural Organisation of the United Nations (FAO) predicts that the world’s human population will increase by 34% to reach 9.1 billion by 2050 (Fisheries and Aquaculture Department, 2010). To feed this increasing population, it is estimated that food production must increase by approximately 70%. With many capture fisheries under intense pressure and with very little potential for growth, aquaculture technologies are rapidly increasing in relevance and requirement to help meet the growing global demand for seafood products.

The European lobster, Homarus gammarus (L) is an economically important, high-value species with a relatively limited fishery. For many years, lobsters have been reared in hatchery conditions, from larvae through the early juvenile stages of development for purposes of stock enhancement, ranching and re-stocking. /-/. gammarus is not currently exploited by the aquaculture sector, and low supply from capture fisheries is generally far exceeded by demand, resulting in very high prices across global markets.

There is currently a lack of appropriate technological development in system design for rearing H. gammarus, coupled with inappropriate economies of scale for on-growing economically viable numbers of post-juvenile lobsters in land based systems. Due to their cannibalistic nature when confined in restricted spaces, this and other species of clawed lobster demand the use of rearing systems that provide individual compartments while allowing sufficient water exchange and provision of food.

Field trials have been conducted experimenting with rearing lobsters using baskets designed to rear oyster spat. However, despite some aspects of these trials producing encouraging results, overall success has been limited.

The use of oyster spat baskets has a number of disadvantages for rearing lobster juveniles. For example, water flow through the oyster spat basket can be too high at maximum tidal flow. This is likely to result in stress to juvenile lobsters, inhibiting their growth and in some instances contributing to elevated mortality rates.

In addition, the design of oyster spat baskets (with multiple compartments in a circular arrangement) means that lobsters are exposed to very different rearing conditions (e.g. flow rate) depending on where their compartment is positioned within the basket. This can cause a marked variation in the growth and survival of lobsters. The internal (radially extending) walls within the oyster spat basket also inhibit the evenness of water flow through the compartments, impeding optimum conditions for lobster growth.

As used herein, the term “shellfish” means any species of crustaceans, molluscs and echinoderms.

In accordance with a first aspect, there is provided apparatus for rearing shellfish, the apparatus comprising an enclosure having a base, a top and a side wall extending between the base and the top, the base and the top both having a substantially quadrilateral shape, the side wall of the enclosure being perforated to permit water flow through the enclosure, and a first attachment device to permit the enclosure to be attached, in use, to an underwater securing means, the first attachment device being located adjacent a first apex of the quadrilateral shape.

Preferably, the quadrilateral shape is a kite shape and most preferably substantially a rhombus. However, another quadrilateral shape could be used, such as a rectangle, square.

Typically, the apparatus further comprises a first divider extending from one apex to an opposite apex of the quadrilateral, the first divider dividing the enclosure into two sub-enclosures, the plane of the first divider being transverse to the plane of the base. Preferably, the two sub-enclosures formed by the first divider have a substantially triangular cross-section.

Typically, the one apex from which the first divider extends is the first apex adjacent the first attachment device.

The first attachment device may comprise a channel or hole having a longitudinal axis substantially parallel to an axis extending between the top and the base. The first attachment device may extend between the top and the base. Typically, the first attachment device extends along the side wall.

Preferably, the apparatus further comprises a number of compartments located on top of each other, a top of one compartment forming the base of the compartment above. In other words, a number of compartments are arranged in the form of an array extending from the base to the top.

The sidewall may be engaged with the base adjacent one end of the side wall, the top may be engaged with the opposite end of the sidewall; the sidewall, the base and the top may define an enclosed space; and a number of dividers located within the enclosed space to divide the enclosed space into a number of compartments. Typically, the dividers may contact at least one of the sidewall, base and top

The dividers may comprise at least one of a first divider having a plane substantially perpendicular to the plane of the base and a second divider having a plane substantially parallel to the base. Where there are both first and second dividers, at least some of the first and second dividers alternate between the base and the top.

Preferably, the base and top are each formed from a second divider.

The sidewall may be provided with formations that are adapted to be engaged with formations on the dividers. Typically, the second divider may have at least one protrusion that engages with an aperture in the side wall. The protrusion may protrude through the side wall to the other side of the side wall. The protrusion may have a retaining formation and when the protrusion protrudes through the side wall, the retaining formation is located on the other side of the side wall and is adapted to receive a retaining member to prevent the protrusion from disengaging from the aperture. The protrusion may be in the form of a wedge or a trapezoidal shape. Preferably, the second divider has both a wedge shaped protrusion and a trapezoid shaped protrusion and most preferably, two wedge shaped protrusions and/or two trapezoidal shaped protrusions.

Preferably, at least one of the first dividers and the second dividers have a perforated portion to permit water flow through the dividers. Preferably, all the dividers are perforated. Preferably, the top and the base of the container are also perforated.

The amount of perforations on the apparatus is preferably maximised to increase the surface area available for deposition and/or growing of food on the surfaces of the apparatus. Preferably, the perforations are provided by a mesh structure. Typically, the mesh structure is formed during forming of the apparatus. Most preferably, the mesh structure comprises a square mesh structure. However, alternatively, or in addition, other mesh structures or other types of perforations could be used, such as circular holes.

The base, top and side wall may be formed as separate components from each other, typically by a moulding process and the perforations are formed during the moulding process. Where the side wall comprises a number of side wall sections, each side wall section is typically formed as a separate component.

Typically, the apparatus is formed from a plastics material, such as a thermoplastic material. It is possible that different parts of the apparatus could be formed from different materials. However, preferably, the different parts of the apparatus are formed from the same material which, for example, could be polyethylene.

Typically, another formation on the first divider engages another formation on the second dividers. The other formation on the first divider may be one of a channel and a lip and the other formation on the second divider may be the other of a channel and a lip. Preferably, there are two other formations on each first divider and two other formations on each second divider, whereby two first dividers can engage with each second divider and two second dividers can engage with each first divider.

Typically, a third divider may also be provided having a plane substantially perpendicular to the plane of the base, the height of the third divider being different from the first divider. Preferably, the third divider has a height greater than the height of the first divider. The third divider being used to create a compartment that has a bigger height than the compartment created by the first divider. Most preferably, the height of the third divider is approximately equal to the height of two first dividers plus the thickness of a second divider.

Typically, the enclosed space defined by the sidewall, base and top is substantially a cuboid.

The sidewall may comprise a number of sidewall sections that contact each other to form the sidewall. The apparatus may further comprise attachment means to attach the sidewall sections to each other to form the sidewall. Typically, the side wall comprises four sidewall sections.

When two of the side wall sections are attached to each other, the base and top may be engaged with the two side wall sections. The dividers may also be engaged with the two side wall sections when the two side wall sections are attached to each other. Another two side wall sections may be attached to each other and then attached to the first two side wall sections to form the enclosed space.

Typically, one of the other two side wall sections is adapted to be attached to one of the first two side wall sections preferably by a pivoting mechanism, and the other two side wall sections and the first two side wall sections are then adapted to pivot with respect to each other to bring the other of the other two side wall sections into contact with the other of the first two side wall sections to permit them to be attached to each other to form the enclosed space.

The pivoting mechanism may comprise a first hinge pin. The other of the other two side wall sections may be adapted to be attached to the other of the first two side wall sections by a second hinge pin.

Preferably, at least one of the base, the top and each of the sidewall sections are substantially planar.

The first attachment device may define an axis of rotation about which the apparatus can pivot.

The first attachment device may comprise a channel or hole having a longitudinal axis substantially parallel to an axis extending between the top and the base. The axis of rotation may coincide with the longitudinal axis of the channel or hole. The first attachment device may extend between the top and the base. Typically, the first attachment device extends along the side wall. Preferably the first attachment device forms part of the side wall.

The underwater securing means may comprise an elongate member, the elongate member being at least one of a flexible elongate member, such as a rope, and a rigid elongate member. The underwater securing means may further comprise a buoy and/or weight. If the securing means comprises a rigid elongate member, the rigid elongate member may comprise an anchoring stake, such as a metal rod.

The apparatus may further comprise a second attachment device, the second attachment device being located adjacent a second apex of the quadrilateral, the second apex being opposite the first apex. Preferably, the second attachment device is the same as the first attachment device.

Preferably, the angle of the first apex adjacent the first attachment device is smaller than the angles of the apexes adjacent the first apex. Typically the first apex has an angle that is less than 90°. The angles of the apexes adjacent the first apex are typically greater than 90°. The angle of the second apex is typically less than 90° and preferably the same as the first apex. Preferably, the first apex is between 65° and 85°, more preferably between 70° and 80° and even more preferably between 74° to 78° and most approximately 76°. Where the quadrilateral is a rhombus, the first apex and the apex opposite are most preferably approximately 76° and the other two apexes are approximately 104°. This feature of the angle of the first apex being smaller than the angles of the apexes adjacent the first apex is particularly useful where the shellfish are lobsters, such as H. gammarus.

Typically, the shape of the quadrilateral and the size of the angles of the apexes are selected to control water flow within the enclosure. Preferably, the angles are selected so that the water flow within the enclosure is less than 300 mm/s if the shellfish is H. gammarus, and more preferably, no greater than 250 mm/s.

Typically, the perforations in the side wall have a central axis that is substantially perpendicular to the plane of the side wall. The angle of the central axis of the perforations can also help to control water flow within the enclosure and is preferably combined together with the angle of the apexes to control water flow within the container.

The apparatus may be for rearing crustaceans, such as lobsters.

In accordance with a second aspect, there is provided apparatus for rearing shellfish, the apparatus comprising an enclosure having a base, a top and side wall, the side wall of the enclosure being perforated to permit water flow through the enclosure, and a first attachment device to permit the enclosure to be attached, in use, to an underwater securing means, the first attachment device being located adjacent the side wall; and wherein the enclosure has a number of separate compartments located within the enclosure.

Preferably, the compartments are located in an array extending between the base and the top.

The second aspect may also be used with any of the features of the first aspect.

In accordance with a third aspect, there is provided a method of stocking or loading shellfish into apparatus for rearing shellfish, the apparatus comprising an enclosure having a base, a top and a side wall, the enclosure having a number of separate compartments located within the enclosure, and the side wall comprising a number of side wall sections, each of the side wall sections being attachable to form the side wall; the method comprising: inserting shellfish into the compartments in the enclosure with at least an edge of one side wall section being detached and separated from an edge of another side wall section; and after the shellfish are inserted into the compartments, moving the one side wall section and the other side wall section with respect to each other until the edges are adjacent each other and attaching the one side wall section to the other side wall section to form the side wall and to complete the enclosure, whereby the shellfish are retained in their compartments in the apparatus when the one side wall section edge is adjacent the other side wall section edge and the one side wall section is attached to the other side wall section.

In accordance with a fourth aspect, there is provided a method of harvesting or unloading shellfish from apparatus for rearing shellfish, the apparatus comprising an enclosure having a base, a top and a side wall, the enclosure having a number of separate compartments located within the enclosure, and the side wall comprising a number of side wall sections, each of the side wall sections being attachable to form the side wall; the method comprising: detaching one side wall section from another side wall section; moving the one side wall section and the other side wall section with respect to each other to separate an edge of the one side wall section from an edge of the other side wall section; and removing shellfish from the compartments in the enclosure.

Preferably, the side wall sections are moved with respect to each other by a pivoting movement.

The apparatus of either of the first or second aspects may be used with the methods of the third or fourth aspects.

An example of apparatus for rearing shellfish in accordance with the invention will now be described with reference to the accompanying drawings, in which;

Fig. 1 is a perspective view of a container for rearing lobsters in accordance with the invention.

Fig. 2 shows a sidewall section forming part of the container shown in Fig. 1;

Fig. 3 shows a horizontal divider forming part of the container shown in Fig. 1;

Fig. 4 shows a first example of an internal vertical divider for use with the container shown in Fig. 1;

Fig. 5 shows a second example of an internal vertical divider for use with the container shown in Fig. 1;

Fig. 6 shows a securing pin forming part of the container shown in Fig. 1;

Fig. 7 shows four of the sidewall sections of Fig. 2 with a first pair secured to each other and a second pair secured to each other;

Fig. 8 shows the two sidewall section pairs of Fig. 7 secured to each other with the securing pin shown in Fig. 6 and the horizontal divider of Fig. 3 being inserted;

Fig. 9 is a cross-sectional view through the assembled container of Fig. 1;

Fig. 10 shows the container of Fig. 1 in use with a single securing system; and Fig. 11 shows the container of Fig. 1 in use with two securing systems.

Fig. 1 shows an aquaculture container 1 having a number of compartments (see Fig. 9) for rearing lobsters, such as Homarus gammarus. The components of the container 1 include four sidewall sections 2(a-d), a number of horizontal dividers 3 and two securing pins 4. In addition, the container 1 can include a combination of small vertical dividers 5 and /or large vertical dividers 6. The large vertical divider 6 has a height that is approximately twice the height of the small vertical divider 5. These components are shown individually in more detail in Figs. 2 to 6.

Fig. 2 shows one of the sidewall sections 2. The sidewall sections 2 each have a central section in the form of a mesh 7 which is divided into a number of mesh sections 7a to 7e. Located in the central section are a number of apertures 8. On one edge 17 of the sidewall 2 are pairs of semi-circular formations 9, 10. Each semi-circular formation 9 of a pair is offset and opposes the other semi-circular formation 10 of the pair. On the opposite edge 12 of the sidewall 2 is another semi-circular formation 11 that runs along the entire length of the edge 12 of the central section of the sidewall 2. The semi-circular formation 11 has a number of apertures 13, 16 formed in it. Adjacent to the semi-circular formation 11 are flat surfaces 14, 15 that together define a plane that is at an angle to the plane of the central section formed by the mesh 7.

The sidewall sections 2 are typically manufactured from a plastics material, such as a thermoplastic material, and may be formed by a moulding process, such as by injection moulding.

The horizontal divider 3 is in approximately the shape of a rhombus with the apexes 20, 21 defined by the smaller angles of the rhombus and having an approximately U-shaped channel 22 extending between the apexes 20, 21 on each side of the horizontal divider 3. In this example, the angles of the apexes 20, 21 are 76.1° and the angles of the other two apexes are 103.9°. However, it is possible that the angles may be varied depending on the species of shellfish which the container 1 is intended to be used for rearing and/or other factors, such as the intended location of the container 1 and/or age of the shellfish to be reared.

The horizontal divider 3 has flattened sections 23, 24 where the other apexes of the rhombus would be. In addition, adjacent sides 25, 26 of the horizontal divider 3 each have a wedge-shaped protrusion 27. The other two adjacent sides 33, 34 each have a protrusion 46 in the shape of a trapezoid. Both the wedge-shaped protrusions 27 and the trapezoidal-shaped protrusions 46 have an aperture 32. The horizontal divider 3 has two mesh sections 28a, 28b which are located within an area defined by the channel 22 and peripheral rims 29, 30. It is to be noted that the side of the horizontal dividing member 3 that is hidden from view in Fig. 3 is identical to the side that is shown in Fig. 3. A lip 31 extends around the peripheral edge of the horizontal divider 3 and extends out from the rims 29, 30.

The horizontal divider 3 may also be formed from a plastics material, such as a thermoplastic, and may be formed by a moulding operation, such as by injection moulding.

The small vertical divider 5 is shown in Fig. 4 and has a tongue 35 at each end and a lower edge 36 and an upper edge 37. The distance between lower edge 36 and the upper edge 37 is approximately the same as the distance between adjacent slots 8 in the sidewalls sections 2. The small vertical divider 5 may also be formed from a plastics material, such as a thermoplastic, and may be formed by a moulding operation, such as by injection moulding. It is predominantly in the form of a mesh 38 with a lip 39 formed around the periphery of the mesh 38.

The large vertical divider 6 is similar to the small vertical divider 5, but has two tongues 40 at each end and at each end the tongues 40 are separated by a triangular protrusion 41. The large vertical divider 6 has a lower edge 42 and an upper edge 43 and the distance between the lower edge 42 and the upper edge 43 is approximately the distance between the next nearest adjacent slots 8 in the sidewall section 2 (or approximately twice the distance between adjacent slots 8). As with the small divider 5, the large divider 6 is predominately in the form of a mesh section 44 surrounded by a peripheral lip 45. The large divider 6 may also be formed from a plastics material such as a thermoplastic, and may be formed by a moulding operation, such as by injection moulding.

The securing pin 4 has an elongated cylindrical section 50 with a frustoconical section 51 at one end and a flange formation 52 formed at the other end. The securing pin 4 may also be formed from a plastics material such as a thermoplastic, and may be formed by a moulding operation, such as by injection moulding.

In use, two sidewall sections 2a, 2b are orientated such that the flat sections 14, 15 butt against each other and fastening devices, such as wire or cable ties, are passed through the slots 13, 16 to secure the two sidewall sections 2 together at the semi-circular formations 11. Hence, when the sidewall sections 2 are secured together the semi-circular formations 11 define a circular hole 61. A second pair of sidewalls sections 2c, 2d are also secured together in a similar manner to the pair 2a, 2b, as shown in Fig. 7.

The two pairs of attached sidewalls 2a, 2b and 2c, 2d are then positioned with one edge 17 of one pair positioned adjacent to one edge 17 of the other pair, as shown in Fig. 8, such that the opposing semi-circular formations 9, 10 on the edge 17 of sidewall section 2a locate between the semi-circular formations 9, 10 on the edge 17 of sidewall section 2c. This enables the semi-circular formations 9, 10 on the adjacent edges 17 to form a channel into which one of the securing pins 4 can be located to secure sidewall section 2a to sidewall section 2c, as shown in Fig. 8. The frustoconical end section 51 helps to facilitate easier location and insertion of the pin 4 into the channel formed by the formations 9, 10.

After the two pairs of sidewall sections 2a, 2b and 2c, 2d have been secured together with the securing pin 4, as shown in Fig. 8, horizontal dividers 3 can then be inserted into the U-shaped channels 65 formed on the inside of the sidewall sections 2. The lip 31 on the horizontal divider locates in U-shaped channel 65 and when it is pushed in such that the apex 20 is received into the curved U-shaped channel 66 and the protrusions 27 snap into the corresponding slots 8 formed in the channel 65. In addition, other horizontal dividers 3 can also be positioned into the curved U-shaped channel portions 67 with the protrusions 27 locating in slots 8 to divide the container of compartments into smaller compartments. When the dividers 3 are fully located in the corresponding channels 65, 66,67 and the protrusions 27 are fully inserted into the holes 8, the protrusions 27 extend through the holes 8 to the outside of the side wall sections 2c, 2d so that the holes 32 are located on the outside of the side wall sections 2c, 2d.

This enables a fastener, such as a cable tie or other retaining means (for example, a retaining pin), to be inserted through the hole 32 after the barb 27 is located in the slots 8. This helps to retain the horizontal divider 3 in position on the sidewall sections 2c, 2d and helps to prevent accidental disengagement of the dividers 3 from the channels 65, 66, 67.

Furthermore, vertical dividers 5, 6 can be used to divide each compartment in half. In this case, the vertical dividers 5, 6 are inserted after the horizontal dividers 3 are inserted. The vertical dividers 5, 6 are inserted by sliding the edges 36, 37, 42, 43 into the U-shaped channels 22 in the horizontal dividers 3, such that the lower edge 36, 42 is inserted into an upwardly facing U-shaped channel 22 of a lower horizontal divider 3 and an upper edge 37, 43 is inserted into downwardly facing U-shaped channel 22 of an upper horizontal divider 3.

Hence, the container 1 of compartments can be configured as desired to include up to twenty separate compartments if the horizontal dividers are inserted into all the U-shaped channels 65 and curved channels 66, 67 and ten small vertical dividers 5 are inserted between each pair of horizontal dividers. If a horizontal divider is not inserted into one or more of the curved U-shaped formations 67, then one or more large vertical dividers 6 can be inserted between the horizontal dividers 3 and the triangular protrusions 41 of the large vertical divider 6 will protrude into the U-shaped channel 67 between the horizontal dividers 3. With only a base horizontal divider 3 and a top horizontal divider 3 inserted, and no other horizontal dividers and no vertical dividers, the container 1 would be a single large compartment.

Fig. 9 shows a cross-sectional view through the container 1 with the container 1 configured with nine internal horizontal dividers 3 inserted, in addition to the base horizontal divider and the top horizontal divider, and ten small vertical dividers 5. In this configuration the container 1 is configured to have the maximum number of separate compartments 70, which is twenty compartments 70. Each compartment 70 within the container 1 can contain a lobster.

After all the required horizontal dividers 3 and vertical dividers 5, 6 are inserted, lobsters are placed in the individual compartments 70. When all the lobsters are in their compartments, the sidewall sections 2a, 2b can be rotated on the pin 4 relative to the side wall sections 2c, 2d to close the open container. As the sidewall sections 2a, 2b are rotated relative to sidewall sections 2c, 2d, the lip 31 on sides 33, 34 of the horizontal dividers locates in the corresponding slots 65, 66, 67 on sidewall sections 2a, 2b and the protrusions 46 locate in the corresponding slots 8 in the sidewall sections 21, 2b. When the sidewall sections 2a, 2b have rotated so that the edge 17 of sidewall section 2b butts against the edge 17 of the sidewall section 2d this enables the second securing pin 4 to be inserted into the channel formed by the semi-circular formations 9, 10 on the edges 17 to lock the sidewall sections 2b, 2d together. The compartments 70 are then locked shut and the container 1 is ready to be deployed in a subsea location and anchored to the seabed.

Being able to modify the container 1 by changing the configuration and size of the compartments allows considerable flexibility in the size of the compartments and the number of animals that can be accommodated within the container 1. This enables lobsters of different sizes and different ages to be accommodated within different sized compartments, even within the same container 1. Hence, the compartment sizes can be configured to suit a particular lobster size to increase the efficiency of the container and minimise wasted space. With a small vertical divider 5, the height of a compartment 70 is 37.1 mm and the compartment has a volume of approximately 1166cm3. With one horizontal divider omitted and a large vertical divider 6 replacing a small vertical divider 5, the height of a compartment is 76.7mm and the volume is approximately 2412cm3. To create larger compartments the vertical dividers 5, 6 can be omitted so that there is no vertical divider 5, 6 between adjacent horizontal dividers 3 and/or two or more horizontal dividers 3 can be omitted. It is also possible that vertical dividers having a height greater than the dividers 5, 6 can be used to create larger compartments. For example, with two adjacent horizontal dividers omitted from the configuration shown in Fig. 9, a vertical divider having a height equal to three times the height of a divider 5 plus two times the thickness of the divider 3 could be used to divide the compartment created by omission of two adjacent dividers 3.

In addition, all the individual components 2, 3, 4, 5, 6 have substantially flattened profiles, which permits flat-packing for volumetrically efficient storage. This is advantageous during shipping (to minimise carriage costs), during deployment and harvest (when held on space limited vessels) and during de-fouling operations (as it allows easy access to all areas of the container and facilitates efficient submerged cleaning operations).

To secure the container 1 in a subsea location, a sub-surface securing system 75 (as an example, this could be a flexible or solid structure i.e. a rope or mooring stake) can be inserted through one of the holes 61 with the securing system 75 extending vertically as shown in Fig. 10. In this arrangement with a single securing system 75, the container 1 is able to pivot about a vertical axis on the securing system 75 as the direction of tidal or current flow changes, so that the container 1 is orientated downstream of the securing system 75 and the orientation of the container 1 with respect to the sea bed can change. This is particularly relevant in coastal regions where tidal flows cause frequent and considerable variation in the prevailing direction of water flow. An example of a suitable securing system is an aquaculture long line system, similar to those used in mussel aquaculture.

The advantage of the rhombus footprint shape of the container 1 is that, as the mesh holes are perpendicular to the side wall sections 2, they are positioned at an angle to the direction of the current or tidal flow. This helps to reduce the water flow in the container 1 and the compartments 70 to less than the actual water flow around the container 1. This is beneficial in reducing the shear stress and turbulence within the container 1 to a magnitude that does not stress the lobsters or impair their growth and survival. Preferably, the maximum water flow within the container 1 for the successful growth and development of H. gammarus is not greater than 250 mm/s and preferably the minimum water flow within the container 1 is not less than 4.1 mm/s.

However, the maximum and minimum water flow within the container 1 could be different for other shellfish species reared in the container. Depending on the type of shellfish to be housed and their flow requirement, the maximum flow within the container could be varied to be either greater than or less than 250 mm/s by varying the angles of the apexes of the footprint of the container 1. For example, this could be varied to a different rhomboid or other quadrilateral shape. Similarly, the minimum flow within the container could also be varied to be greater than or less than 4.1 mm/s by varying the angles of the apexes of the footprint of the container 1. In addition, the flow could be varied by changing the footprint to a different polygonal shape or a non-polygonal shape, such as a circle or ellipsoid.

In another example, the container 1 could be anchored with two securing systems 75, as shown in Fig. 11. In this arrangement, the securing systems are also vertical and the orientation of the container 1 is fixed relative to the sea bed and does not change orientation with respect to the direction of the current or tidal flow.

In addition, with either the single or double securing system, multiple containers 1 may be placed on top of each other on the same securing system 75 to make use of vertical space (i.e. water column depth) and make more efficient use of the horizontal space (i.e. seabed area) occupied by the containers 1. This can be particularly important in any commercial aquaculture implementation, where the surface area of the seabed licenced to support rearing equipment is often strictly limited.

The horizontal dividers 3 are formed predominantly of a mesh to enable water penetration through the container. Flaving the horizontal dividers largely formed from permeable mesh is also desirable as it enables particulate waste to fall through the container and exit from the lowermost horizontal divider, preventing excessive build-up of lobster’s waste products or any other suspended detritus.

Another important aspect of the use of the mesh 7, 28, 38 and 44 is that it presents a large surface area on which drifting organisms can attach, thereby ensuring sufficient food supply for the lobsters within the container 1.

In addition, the rhomboidal shape of the container 1 helps to produce a relatively uniform flow through the internal compartments 70. This is especially the case when the container 1 is anchored or moored with only one securing system 75 and the vertical dividers are orientated so that they extend from the apex adjacent the securing system 75 to the opposite apex, as in this instance the vertical divider is effectively held parallel to the tidal or current flow, and helping to minimise uneven flow within the container 1. This means that all lobsters in the container essentially experience uniformity of water flow and food supply, regardless of the relative position of their internal compartment.

The use of the securing pins 4 enables one of the securing pins 4 to be removed to permit hinging of one pair of sidewall sections 2a, 2b relative to the other pair 2c, 2d. This facilitates access to the compartments 70 for stocking (loading), grading, harvesting (unloading) of lobsters to and from the compartments. It also has the advantage of enabling reconfiguration of the compartments 70 within the container to be carried out (for example, during a stock grading operation) without requiring the whole container structure to be disassembled.

Although for lobsters and other marine shellfish species, the container would be moored or anchored in the sea, the container 1 could be moored or anchored in a body of fresh water, such as a lake or river, for rearing freshwater shellfish.

Claims (45)

1. Apparatus for rearing shellfish, the apparatus comprising an enclosure having a base, a top and a side wall extending between the base and the top, the base and the top both having a substantially quadrilateral shape, the side wall of the enclosure being perforated to permit water flow through the enclosure, and a first attachment device to permit the enclosure to be attached, in use, to an underwater securing means, the first attachment device being located adjacent a first apex of the quadrilateral shape.

2. Apparatus according to claim 1, wherein the quadrilateral shape is substantially a rhombus.

3. Apparatus according to claim 1 or claim 2, further comprising a first divider extending from one apex to an opposite apex of the quadrilateral, the first divider dividing the enclosure into two sub-enclosures, the plane of the first divider being transverse to the plane of the base.

4. Apparatus according to claim 3, wherein the two sub-enclosures formed by the first divider have a substantially triangular cross-section.

5. Apparatus according to claim 3 or claim 4, wherein the one apex from which the first divider extends is the first apex adjacent the first attachment device.

6. Apparatus according to any of the preceding claims, further comprising a number of compartments located on top of each other, a top of one compartment forming the base of the compartment above.

7. Apparatus according to claim 6, wherein the apparatus further comprises a sidewall engaged with the base adjacent one end of the side wall, a top engaged with the opposite end of the sidewall, the sidewall, the base and the top defining an enclosed space; and a number of dividers located within the enclosed space and contacting at least one of the sidewall, base and top to divide the enclosed space into a number of compartments.

8. Apparatus according to claim 7, wherein the dividers comprise at least one of a first divider having a plane substantially perpendicular to the plane of the base and a second divider having a plane substantially parallel to the base.

9. Apparatus according to claim 8, wherein at least some of the first and second dividers alternate between the base and the top.

10. Apparatus according to claim 8 or claim 9, wherein the second divider is the same as the base, and the top is the same as the base.

11. Apparatus according to any of claims 7 to 10, wherein the sidewall has formations that are adapted to be engaged with formations on the dividers.

12. Apparatus according to claim 11 when dependent on any of claims 8 to 10, wherein the second divider has at least one protrusion that engages with an aperture in the side wall and protrudes through the side wall to the other side of the side wall.

13. Apparatus according to claim 12, wherein the protrusion has a retaining formation and when the protrusion protrudes through the side wall, the retaining formation is located on the other side of the side wall and is adapted to receive a retaining member to prevent the protrusion from disengaging from the aperture.

14. Apparatus according to claim 12 or claim 13, wherein the protrusion is in the form of a wedge.

15. Apparatus according to any of claims 8 to 14, wherein at least one of the first dividers and the second dividers have a perforated portion to permit water flow through the dividers.

16. Apparatus according to any of claims 8 to 15, wherein another formation on the first divider engages another formation on the second dividers.

17. Apparatus according to claim 16, wherein there are two other formations on each first divider and two other formations on each second divider, whereby two first dividers can engage with each second divider and two second dividers can engage with each first divider.

18. Apparatus according to any of claims 8 to 17, further comprising a third divider having a plane substantially perpendicular to the plane of the base, wherein the third divider has a height greater than the height of the first divider, the third divider being used to create a compartment that has a bigger height than the compartment created by the first divider.

19. Apparatus according to claim 18, wherein the height of the third divider is approximately equal to the height of two first dividers plus the thickness of a second divider.

20. Apparatus according to any of claims 7 to 19, wherein the enclosed space defined by the sidewall, base and top is substantially a cuboid.

21. Apparatus according to any of claims 7 to 20, wherein the sidewall comprises a number of sidewall sections that contact each other to form the sidewall and the apparatus further comprising attachment means to attach the sidewall sections to each other to form the sidewall.

22. Apparatus according to claim 21, wherein when two of the side wall sections are attached to each other the base and top may be engaged with the two side wall sections.

23. Apparatus according to claim 22, wherein the dividers may also be engaged with the two side wall sections.

24. Apparatus according to claim 22 or claim 23, wherein another two side wall sections may be attached to each other and then attached to the first two side wall sections form the enclosed space.

25. Apparatus according to claim 24, wherein one of the other two side wall sections is adapted to be attached to one of the first two side wall sections by a pivoting mechanism, and the other two side wall sections and the first two side wall sections are then adapted to pivot with respect to each other to bring the other of the other two side wall sections into contact with the other of the first two side wall sections to permit them to be attached to each other to form the enclosed space.

26. Apparatus according to claim 25, wherein the pivoting mechanism comprises a first hinge pin.

27. Apparatus according to claim 25 or claim 26, wherein the other of the other two side wall sections is adapted to be attached to the other of the first two side wall sections by a second hinge pin.

28. Apparatus according to any of claims 7 to 27, wherein the base, the top and each of the sidewall sections are substantially planar.

29. Apparatus according to any of the preceding claims, wherein the top and the base of the container are perforated.

30. Apparatus according to any of the preceding claims, wherein the first attachment device forms an axis of rotation about which the apparatus can pivot.

31. Apparatus according to any of the preceding claims, wherein the angle of the first apex adjacent the first attachment device is smaller than the angles of the apexes adjacent the first apex.

32. Apparatus according to any of the preceding claims, wherein the underwater securing means comprises an elongate member, the elongate member being at least one of a flexible elongate member, such as a rope, and a rigid elongate member.

33. Apparatus according to any of the preceding claims, further comprising a second attachment device, the second attachment device being located adjacent a second apex of the quadrilateral, the second apex being opposite the first apex.

34. Apparatus according to any of the preceding claims, wherein the apparatus is for rearing crustaceans, such as lobsters.

35. Apparatus for rearing shellfish, the apparatus comprising an enclosure having a base, a top and side wall, the side wall of the enclosure being perforated to permit water flow through the enclosure, and a first attachment device to permit the enclosure to be attached, in use, to an underwater securing means, the first attachment device being located adjacent the side wall; and wherein the enclosure has a number of separate compartments located within the enclosure.

36. Apparatus according to claim 35, wherein the compartments are located in an array extending between the base and the top.

37. Apparatus according to claim 35 or claim 36, further comprising any of the features of claims 1 to 34.

38. Apparatus according to any of the preceding claims, wherein the parts of the apparatus, such as the perforation, in use, form a surface for deposition and/or growth of water-based organisms.

39. A method of stocking or loading shellfish into apparatus for rearing shellfish, the apparatus comprising an enclosure having a base, a top and a side wall, the enclosure having a number of separate compartments located within the enclosure, and the side wall comprising a number of side wall sections, each of the side wall sections being attachable to form the side wall; the method comprising: inserting shellfish into the compartments in the enclosure with at least an edge of one side wall section being detached and separated from an edge of another side wall section; and after the shellfish are inserted into the compartments, moving the one side wall section and the other side wall section with respect to each other until the edges are adjacent each other and attaching the one side wall section to the other side wall section to form the side wall and to complete the enclosure, whereby the shellfish are retained in their compartments in the apparatus when the one side wall section edge is adjacent the other side wall section edge and the one side wall section is attached to the other side wall section.

40. A method of harvesting or unloading shellfish from apparatus for rearing shellfish, the apparatus comprising an enclosure having a base, a top and a side wall, the enclosure having a number of separate compartments located within the enclosure, and the side wall comprising a number of side wall sections, each of the side wall sections being attachable to form the side wall; the method comprising: detaching one side wall section from another side wall section; moving the one side wall section and the other side wall section with respect to each other to separate an edge of the one side wall section from an edge of the other side wall section; and removing shellfish from the compartments in the enclosure.

41. A method according to claim 39 or claim 40, wherein side wall sections are moved with respect to each other by a pivoting movement.

42. A method according to any of claims 39 to 41, wherein the apparatus is further in accordance with any of claims 1 to 38.

43. Apparatus for rearing shellfish substantially as herein before described with reference to any of the accompanying drawings.

44. A method of stocking or loading shellfish into apparatus for rearing shellfish, substantially as herein before described with reference to any of the accompanying drawings.

45. A method of harvesting or unloading shellfish from apparatus for rearing shellfish, substantially as herein before described with reference to any of the accompanying drawings.