EP4167730A1

EP4167730A1 - Apparatus, assembly and method for use in high energy marine environments

Info

Publication number: EP4167730A1
Application number: EP21826469.5A
Authority: EP
Inventors: Kevin HEASMAN
Original assignee: Cawthron Institute Trust Board
Current assignee: Cawthron Institute Trust Board
Priority date: 2020-06-19
Filing date: 2021-06-21
Publication date: 2023-04-26
Also published as: AU2021291806A1; WO2021255714A1; JP2023531015A

Abstract

An apparatus, a receiver and retainer assembly, and their use in open ocean aquaculture are described. The apparatus incorporates multiple interchangeable rotatably mounted cultivation racks. The apparatus is used with a single mooring line. Interlocking float bodies are mounted on an axle through which the mooring line passes. When submerged the interlocking float bodies provide the apparatus with buoyancy. The apparatus is held at a desired depth by the receiver and retainer assembly releasably engaging the mooring line. When released the buoyant apparatus rises to the surface. At the surface the interlocking float bodies cause the apparatus to be oriented so that the rotatably mounted cultivation racks can easily be accessed.

Description

APPARATUS, ASSEMBLY AND METHOD FOR USE IN HIGH ENERGY MARINE ENVIRONMENTS

TECHNICAL FIELD

The invention relates to an apparatus and its use in aquaculture. The invention also relates to a retainer and receiver assembly for use in the subsurface positioning of buoyant apparatus on a mooring line. In particular, although not exclusively, the invention relates to an aquaculture apparatus and assembly suitable for use in high energy marine environments.

BACKGROUND ART

The publication of Costa-Pierce (2016) states that seawater aquaculture (mariculture) is the only solution to the world's food supply.As coastal urbanization, industrialization, water pollution, and overall environmental degradation limit the availability of sites for nearshore mariculture, there is an increasingly urgent need to develop large scale open ocean aquaculture. The utilization of open ocean sites requires the development of robust submerged technologies.

The publication of Burgess (1997) discloses a submersible platform for farming shellfish such as mussels and oysters. The platform comprises a frame incorporating chambers of adjustable buoyancy and is submersible.

The publication of Bugrov et al (1998) discloses a fish cage having a means for providing constant buoyancy and vertical positioning system including a negative buoyancy flexible member. The fish cage is held in position by a combination of guy wires, intermediate floats and other lines.

The publication of Jorgensen (2001) discloses a fish cage mounted on a center unit. The fish cage is either fixed to the center unit or movable. The fish cage can be located at any vertical position on the center unit between a mooring device or a surface unit.

The publication of Buck and Buchholz (2007) discloses a device for cultivating marine organisms comprising a pair of concentric and coplanar rings between which radial and concentric cultivation lines are disposed. The device is held submerged between a float at the surface and an anchor weight at the seabed by ropes connected to the outer of the two concentric rings.

The publications of Cortinas and Arbones (2008 and 2010) disclose systems for use as submersible mollusc farms. In one of the disclosed systems, ropes for growing the molluscs are hung from cables strung between end floats. The buoyancy of the end floats may be adjusted to raise or lower the farm.

Tension buoys are connected to the end floats through a series of cables and pulleys attached to dead weights. In another of the disclosed systems, a submerged frame moves vertically along guide tubes fitted to surface floats. The publication of Leslie and Young (2011) discloses an aquaculture apparatus for culturing oysters in deep waters. The apparatus comprises a plurality of float bodies, each anchored to the seabed. The position of each float body relative to the surface is adjustable.

The publication of Thorvardarson et al (2011) discloses a submersible cage for fish farming. The cage comprises a buoyant structure positioned about a central axle and netting attached to the buoyant structure. The submerged cage may be rotated about the central axle. Tethering lines are shown to be attached to either or both ends of the central axle and a fixation or mooring point.

The publications of Menard (2015 and 2020) disclose offshore aquaculture installations. The installations comprise a ballasted floating structure that is submersible and anchored at one point. The installation comprises one or more square or rectangular cages accessible via a handling bridge in the upper portion of the installation.

The publications of Newell (2016 and 2017) disclose a modular submersible aquaculture raft. The raft is submersible, the weight of the raft being distributed between multiple float devices at the surface.

Systems for the offshore cultivation of marine species need to be adaptable, robust, and simple to operate and maintain if they are to be economically viable. The publication of Buck and Langan (2017) provides a review of recent approaches to sustainable offshore food production and the development of the technologies required in these high energy environments.

It is an object of the present invention to provide an apparatus that is relatively simple to deploy and operate in such high energy, open ocean environments. It is a further object of the present invention to provide a method of culturing marine species using the apparatus. It is a yet further object of the invention to provide a system for the offshore cultivation of one or more marine species. Each of these objects is to be read in the alternative with the object of at least to provide a useful choice in the selection of such an aquaculture apparatus, method or system.

SUMMARY OF INVENTION

In a first aspect an aquaculture apparatus for use with a single mooring line is provided, the apparatus comprising:

• an upper end frame and a lower end frame mounted around opposite ends of an open-ended hollow axle so that the mooring line may pass freely through the hollow of the axle;

• three or more evenly spaced apart beams each attached orthogonally at each end to corresponding positions on the periphery of each of the upper and lower end frames;

• one or more cultivation racks releasably mounted between one or more pairs of mountings located at corresponding positions on the periphery of each of the upper and lower end frames midway between where the beams are attached; and

• a float sleeve mounted around the axle.

The apparatus is buoyant when immersed in sea water. The axle, end frames and beams are necessarily fabricated from a material that is tolerant of sea water, such as stainless steel. Fabrication from other materials that are sufficiently rigid and strong, such as fibre-reinforced polymer pultrusions, is also contemplated.

The upper end frame and the lower end frame may be mounted around the opposite ends of the open-ended hollow axle via crossbeams. In one option the crossbeams are integral with the end frame. In another option the crossbeams are joined to the end frames, e.g. by welding. Typically, the upper end frame and the lower end frame will be fixedly mounted around the opposite ends of the open-ended hollow axle.

Advantageously, the lower end of the open-ended axle is provided with a trumpet shaped funnel to both guide the passage of the single mooring line through the hollow of the axle and reduce wear on the mooring line. The upper end of the open-ended axle is typically provided with a receiver for accepting a retainer that releasably engages the mooring line.

Advantageously, the engagement of the mooring line by the retainer is maintained at least in part by the buoyancy of the apparatus.

The spaced apart beams provide the apparatus with rigidity.A spaced apart beam may be attached directly or via a plate joined to the end frames, e.g. by bolting or welding. The spaced apart beams may take the form of a rectangular tube or an I-beam.

The cultivation racks are releasably mounted on the rigid cage formed by the end frames and spaced apart beams via mountings that may incorporate water lubricated synthetic brushes. The cultivation racks are thereby releasably and rotatably mounted on the rigid cage formed by the end frames and spaced apart beams. Different types of cultivation racks may be releasably mounted on the rigid cage allowing for the culture of different marine species on the same apparatus.

Advantageously, the float sleeve comprises interlocking float bodies mountable on the axle so that the buoyancy provided by the float sleeve may be conveniently adjusted.An interlocking float body may be a disc having a channel from its periphery to its centre that is dimensioned to allow the float body to be mounted on the axle and complementary projections and recesses on its upper and lower faces. The interlocking float bodies may be foam filled or hollow. The interlocking float bodies are required to be low density rigid structures having a substantially constant displacement at depths up to fifteen metres below the sea surface.

In a second aspect an assembly for releasably engaging a mooring line without slippage is provided, the assembly comprising a receiver and a retainer where:

• The receiver is a first rigid body having an upper face and a lower face and a truncated conical void tapering from the upper face of the first rigid body to the lower face of the first rigid body and dimensioned to allow the mooring line to pass freely through the first rigid body;

• The retainer is a second rigid body dimensioned to substantially fill the truncated conical void of the receiver and consisting of two or more interlocking parts; and

• The interlocking parts interlock to form an open-ended hollow dimensioned to accommodate the mooring line and having contoured inner surfaces that engage the mooring line in a vice-like grip so that there is no slippage when the mooring line is engaged by the assembly.

In a third aspect a method of culturing marine species in open ocean using the aquaculture apparatus of the first aspect is provided, the method comprising: a)Passing the free end of an anchored mooring line through the open-ended hollow axle of the apparatus to provide a threaded apparatus; b)Immersing the threaded apparatus to a depth at least 5 metres below the surface of the open ocean to provide a submerged apparatus; and c)Releasably engaging the mooring line with a retainer to prevent the submerged apparatus rising above the depth.

Typically, the method will be exploited offshore in the open ocean and the marine species will include species of bivalve molluscs, macroalgae (seaweeds) and shellfish. Bivalve molluscs that may be cultured include mussel spat and oysters.

The mooring line is required to be capable of withstanding the maximum tensions developed during adverse conditions, i.e., storms. Typically, the mooring line will be a wire rope mooring line. Immersing the apparatus to a depth at least 5 metres below the surface reduces the risk of the mooring line breaking. The retainer is required to engage the mooring line so as to prevent slippage or the unintended release of the submerged apparatus from the desired depth.

The maximum depth to which the apparatus may be immersed will depend on local conditions and the marine species being cultured. Immersing the apparatus to a depth between 5 and 15 metres below the surface is likely to be optimal for most combinations of local conditions and the marine species being cultured.

In a fourth aspect a system for the offshore cultivation of one or more marine species is provided, the system comprising:

• a submerged aquaculture apparatus of the first aspect; and

• a mooring line anchored to the seabed, where the mooring line passes through the open-ended hollow axle of the apparatus and the apparatus is prevented from rising above a depth below the surface using a retainer releasably engaged with the mooring line.

Advantageously, the retainer releasably engaged with the mooring line is the sole means for preventing the apparatus from rising above the depth below the surface.

Preferably, a receiver for the retainer is mounted around the upper end of the open-ended axle of the apparatus. More preferably, the apparatus is prevented from rising above the depth below the surface using a retainer and receiver assembly of the second aspect.

In the description and claims of this specification the following abbreviations, acronyms, terms and phrases have the meaning provided: "buoyant" means able or tending to keep afloat or rise to the top of a liquid or gas; "complementary" means having corresponding shape, i.e., congruent; "comprising" means "including", "containing" or "characterized by" and does not exclude any additional element, ingredient or step; "consisting essentially of" means excluding any element, ingredient or step that is a material limitation; "consisting of" means excluding any element, ingredient or step not specified except for impurities and other incidentals;

"contoured" means having been moulded into a specific shape; "crossbeam" means a transverse beam; "culturing" means maintaining in conditions suitable for growth and includes collecting and maintaining in conditions suitable for growth; "fixedly" means not allowing for relative movement; "halves" means two equal or corresponding parts into which something is or can be divided; "hollow" means a hole or depression in something; "interlock" means engage with each other by the fitting together of projections and recesses; "low density" means having a density less than that of water; "mounted" means placed or fixed on a support; "mounted around" means mounted so as not to obstruct, e.g., a collar mounted around an opening so as not to obstruct passage through the opening; "offshore" and "open ocean" mean situated in a high energy environment at sea such as encountered at least 1 nautical mile from the shore; "rigid" means unable to bend or be forced out of shape; "rotational symmetry" means in respect of the location of the complementary projections and recesses of two identical stackable float bodies that the float bodies may be stacked in two or more orientations relative to each other, the orientations being accessed by rotating one of the two float bodies about their common axis; "serrated" means having a jagged edge or surface; "slippage" means the action or process of slipping; "truncate" means shorten by cutting off the end; "taper" means diminish or reduce in thickness towards one end; "threaded" means (in relation to the aquaculture apparatus described here) having a mooring line passing through the hollow of the open- ended axle, and "void" means a completely empty space.A paronym of any of the defined terms has a corresponding meaning.

The terms "upper" and "lower" are used to distinguish features of the aquaculture apparatus or assembly according to their relative position when the apparatus or assembly is deployed. The terms "first", "second", "third", etc. used with reference to elements, features or integers of the subject matter defined in the Statement of Invention and Claims, or when used with reference to alternative embodiments of the invention are not intended to imply an order of preference.An order of preference is implied by "preferably", "more preferably", etc.Any preferment of an element, feature, integer or limitation of one aspect of the invention is also a preferment of the same element, feature, integer or limitation when present in another aspect of the invention.

A non-limiting exemplary embodiment of the aquaculture apparatus and its use in conjunction with the retainer and receiver assembly will now be described with reference to the figures of the accompanying drawings pages.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1. A perspective view from above the cage (1) of an aquaculture apparatus showing upper end frame (2), lower end frame (3), hollow axle (4), crossbeams (5), beams (6) and their attachment positions (8,9), cultivation rack mountings (10, 11) and receiver (12).

Figure 2. A perspective view from below of the cage (1) additionally showing the trumpet horn shaped guide (13).

Figure 3. A perspective view of the cage (1) with interlocking float bodies (14) mounted on the hollow axle (4) to form a float sleeve. Figure 4. Perspective views of the upper (top) and lower (bottom) faces of a float body (14) showing the channel (15) and complementary projections (16) and recesses (17).

Figure 5A. Perspective view of a cylindrical cultivation rack (18).

Figure 5B. Perspective view of a box-shaped cultivation rack (19).

Figure 6A. Perspective view of a cylindrical cultivation rack (18) wound with ropes (20) for mussel spat collection.

Figure 6B. Perspective view of a box-shaped cultivation rack (19) containing two boxes (22) of cultivation frames (21) wound with spat rope (20).

Figure 6C. Perspective view of a box-shaped cultivation rack (19) loaded with oyster baskets (23).

Figure 7. A perspective view of the aquaculture apparatus (24) with interlocking float bodies (14) mounted on the hollow axle (4) and cylindrical cultivation racks (18) and box-shaped cultivation racks (19) mounted alternately between corresponding rack mountings (10,11).

Figure 8. A perspective view of the aquaculture apparatus (24) with the loaded or wound cultivation racks (18,19) shown in Figures 6A to 6C mounted between the rack mountings (11, 12).

Figure 9. A photograph of an embodiment of the aquaculture apparatus being deployed from the deck of a barge using a sea crane with the mooring line and an empty octagonal cultivation cage in the foreground and interlocking float bodies mounted on the central axle.

Figure 10. Schematic representation of the deployment of the aquaculture apparatus (24) using a single mooring line (25) with screw anchor (26), swivel (27), load cell (28) and marker buoy (29).An adjacent monitoring buoy (30) is also shown attached to a second mooring line (25) and screw anchor (26) (not to scale).

Figure 11. Schematic representation of the deployment shown in Figure 10 with the aquaculture apparatus (24) at the surface.

Figure 12. Perspective (A), inner face (B) and side (C) views of the first part of a preferred embodiment of a retainer including an optional cap.

Figure 13. Perspective (A), side (B) and inner face (C) views of the second part of a preferred embodiment of the retainer including an optional cap.

Figure 14. Schematic representation of the first and second parts of the preferred embodiment of the retainer interlocking to engage a wire rope and a receiver (tapered collar) through which the wire rope passes. Figure 15. Cross-sectional view of the first and second interlocking parts of the preferred embodiment of the retainer and the receiver (tapered collar) before (A) and after (B) releasable engagement with the mooring line.

DESCRIPTION

The aquaculture apparatus comprises a cage on which cultivation racks are releasably and rotatably mounted.Advantageously, the apparatus can be deployed with a minimal amount of infrastructure, i.e., a single anchor for the mooring line. The cage includes a hollow axle through which the single mooring line is able to pass. Interlocking float bodies are releasably mounted on this axle forming an elongate float sleeve that both provides buoyancy when the apparatus is submerged and orients the apparatus when it is at the surface.Advantageously, the apparatus can be brought to the surface and the cultivation racks inspected without the need for the apparatus to be lifted out of the water.

A cage (1) comprising an upper end frame (2) and a lower end frame (3) mounted around the upper and lower ends, respectively, of an open-ended hollow axle (4) is shown in Figure 1. The end frames (2,3) are mounted at opposite ends of the hollow axle (4) via crossbeams (5).A plurality of evenly spaced apart beams (6) joined orthogonally to the periphery of each of the end frames (2,3) at corresponding positions (8,9) midway between the vertices of the end frames (2,3) provide the cage with rigidity. The peripheries of each of the end frames (2,3) are additionally provided with rack mountings (10,11) located at the vertices of the end frames (2,3). In alternative embodiments, the beams (6) may be joined at the vertices and the rack mountings (10,11) located midway between the vertices. However, the former configuration of beams (6) and mountings (10,11) will generally be preferred as larger diameter racks may be accommodated.

The end frames (2,3) and beams (6) form an open cage (1) allowing for the flow of seawater through the body of the aquaculture apparatus when it is submerged. In the embodiment illustrated in the figures of the accompanying drawings pages the end frames (2,3) are substantially hexagonal in shape. In other embodiments, end frames that are substantially triangular, square, pentagonal, heptagonal or octagonal in shape may be used. The selection will depend at least in part on the size and number of cultivation racks to be mounted. End frames that are substantially hexagonal or octagonal with two, three or four crossbeams are generally preferred.

A mooring line may pass freely through the hollow of the axle (4) of the cage (1). The upper end frame (2) incorporates a receiver (12), for example a tapered collar, dimensioned to receive a collet or other form of retainer that releasably engages the mooring line. Possible retainer and receiver assemblies are described in the specification accompanying international application no. PCT/NZ2014/000008 [publ. no. WO 2014/116123 A2] However, a particularly preferred retainer and receiver assembly is described below. To facilitate passage and reduce wear on the mooring line the lower end frame (3) incorporates a trumpet horn shaped guide (13) as shown in Figure 2.

Several float bodies (14) are shown mounted on the axle (4) of the cage (1) in Figure 3 and the upper and lower faces of these float bodies (14) are shown in Figure 4. Each of the float bodies (14) has a channel (15) from the circumference to the centre dimensioned to allow the float body to be slidably mounted on the axle (4). The float bodies (14) have complementary projections (16) and recesses (17) on their upper and lower faces, respectively, and rotational symmetry in respect of the location of these complementary projections (16) and recesses (17). The float bodies (14) are therefore stackable and interlocking. The projections (16) and recesses (17) of the float bodies (14) provide for the interlocking in a manner akin to a mortise and tenon. When mounting float bodies (14) on the axle (4), rotating each successive float body (14) about the axle (4) ensures non-alignment of the channels (15) of successive float bodies (14), but alignment of the projections (16) with the complementary recesses (17) of the adjacent float body (14). The float bodies (14) may thereby be releasably retained mounted on the axle (4) as an elongate "float sleeve" using a single locking mechanism and the buoyancy of the aquaculture apparatus readily adjusted by the removal or addition of individual float bodies (14).

Examples of interchangeable cultivation racks (18,19) are shown in Figures 5A and 5B. The cylindrical cultivation rack (18) shown in Figure 5A may be used for the collection of mussel spat or the growth of macroalgae (seaweed). When used for the collection of mussel spat coil or rope (20) is wound around the cylindrical cultivation rack (18) as shown in Figure 6A. When used for the growth of seaweed pre-sown cloth, e.g. linen, is wrapped around the cylindrical cultivation rack (18). The box-shaped cultivation rack (19) shown in Figure 5B may also be used for the collection of mussel spat. When used in this way cultivation frames (21) are wrapped with coil or rope (20) and inserted into boxes (22) designed to hold the cultivation frames (21). The boxes (22) are then inserted into the box-shaped cultivation rack (19) as shown in Figure 6B. The box-shaped cultivation rack (19) may also be used to culture oysters with oyster baskets (23) stacked in the rack as shown in Figure 6C.

The aquaculture apparatus (24) is shown in Figure 7. The aquaculture apparatus (24) is shown with a float sleeve consisting of nine interlocking float bodies (14) mounted on the axle (4). Each float body (14) is sufficiently rigid to maintain substantially the same displacement of water at depths up to 15 metres. The number of float bodies (14) mounted on the axle (4) is adjusted to provide the apparatus with the desired buoyancy. Each of the cultivation racks (18,19) is releasably mounted between an upper rack mounting (11) and a corresponding lower rack mounting (12).

In the embodiment of the aquaculture apparatus (24) shown in Figures 7 (unloaded cultivation racks) and 8 (loaded cultivation racks) the components (end frames (2,3), axle (4) and beams (5,6) are typically fabricated from stainless steel (SS316) and welded together to provide the cage (1) of the aquaculture apparatus (24) with the required rigidity, strength and durability.As a guide to the size of the embodiment of the aquaculture apparatus (24) shown in Figures 7 and 8 the length of the axle (4) is between 1750 and 2250 mm in length and the sides of the hexagonal upper and lower end frames (2,3) are between 1300 and 1600 mm in length. With ten float bodies (14) mounted on the axle (4) the float sleeve provides a total buoyancy of around 1400 Kg.

The apparatus is intended to have a lifespan of 15 to 20 years. Galvanized or polyurethane coated mild steel are possible alternatives to the use of stainless steel (SS316) as is the use of polymers, such as high-density polyethylene (HDPE), with or without fibre reinforcement. Limitations on the use of alternatives to stainless steel (SS316) include the need for sufficient rigidity and strength in the joints of the apparatus. These limitations are less applicable to the cultivation racks (18,19) and the use of a cage fabricated from stainless steel (SS316) with racks fabricated from alternative materials is anticipated due to the greater facility with which the cultivation racks (18,19) may be inspected and replaced in the aquaculture apparatus (24).

The aquaculture apparatus (24) is typically deployed from the deck of a vessel such as a barge using a sea crane as shown in Figure 9. The aquaculture apparatus (24) is deployed using a single mooring line anchored offshore. For example, the mooring line (25) may be attached to a screw anchor (26) installed at the depth of around 45 metres as shown in Figure 10. Advantageously, a swivel (27) is included in the mooring line (25) below the depth to which the aquaculture apparatus (24) is to be deployed. Installing the swivel at a depth between 16 and 20 metres will be suitable for most uses of the aquaculture apparatus. The mooring line (25) may similarly include a load cell (28) located below the depth to which the aquaculture apparatus (24) is to be deployed, but above the location of the swivel (27). Installing the load cell at a depth of 8 to 10 metres will be suitable when the aquaculture apparatus is immersed to 5 metres below the surface. The load cell (28) may serve to provide remote monitoring of the load on the mooring line when the aquaculture apparatus (24) is deployed. The swivel (27) serves to release tension in the mooring line as the deployed aquaculture apparatus (24) is rotated by water currents and wave action.

The location of the mooring line is identified by a single surface marker buoy (29) that can easily be brought on to the deck of the vessel and temporarily detached from the mooring line. The free end of the mooring line is then passed through the trumpet horn shaped guide (13) and the hollow of the axle (4) of the aquaculture apparatus (24). Enough mooring line is passed through the hollow of the axle (4) to allow the collet or other form of retainer that releasably engages the mooring line (25) to be introduced and the surface marker buoy (29) reattached. Where a collet is used the mooring line (25) is fed through the collet before reattachment of the marker buoy (29). Other retainers may comprise a pair of tapered collars that in combination perform the same function as a collet, i.e., engaging the mooring line (25) as their outer faces are abutted by the inner walls of the receiver (12).

The threaded aquaculture apparatus (24) is attached to the hook of a sea crane, lifted from the deck of the vessel, and lowered to the water surface. To facilitate immersion, the threaded aquaculture apparatus (24) may be temporarily weighted and guided to the desired depth with the assistance of scuba divers. The threaded aquaculture apparatus (24) will typically be submerged to a depth of 5 to 10 meters below the surface, the depth being measured from the upper face of the upper end frame (2) of the aquaculture apparatus (24). Once the collet or other form of retainer is in place any weights temporarily attached to the threaded aquaculture apparatus (24) may be removed, attached to the hook of the sea crane and then the threaded aquaculture apparatus (24) detached from the hook.

The mooring line (25) will often be required to be a wire rope. Steel wire ropes and their use as mooring lines are well known. Examples of wire ropes suitable for use in marine and offshore applications and in conjunction with the assembly include those supplied by Katradis (Piraeus, Greece). Relative to mooring lines that are ropes made from natural fibres or synthetic materials, such as polyethylene, mooring lines that are wire ropes are generally less susceptible to stretching. In use, the cross-section of the mooring line is therefore more constant and resistant to compression.

Referring to Figures 12 to 15 of the accompanying drawings pages, a retainer and receiver assembly particularly suited for use with a wire rope mooring line (25) is described. The retainer comprises two asymmetric interlocking halves (31,37). Although the use of this assembly is described in the context of the deployment of the aquaculture apparatus (24), it will be recognised that the assembly may be advantageously used in the deployment of any buoyant marine apparatus where releasable engagement with a mooring line (25) is desired.

Referring to Figure 12 the first half (31) of the retainer is shown. The first half (31) of the retainer has an inner face and an outer surface. The length of the inner face is provided with a central, elongate, open-ended channel (32) dimensioned to accommodate the mooring line (25) when the two asymmetric interlocking halves (31,37) are combined. The first half (31) of the retainer is also provided with two protrusions (33,34) from the inner face either side of the channel (32). The opposing surfaces of the two protrusions (33, 34) are contiguous with the side walls of the channel (32) and each have a contoured surface (35,36).

Referring to Figure 13 the second half (37) of the retainer is shown. The second half (37) of the retainer has an inner face and outer surface. The length of the inner face is provided with a central, elongate, open-ended channel (38) that mirrors that of the first half (31) of the retainer. The second half (37) of the retainer is also provided with two pairs of protrusions (39,40,41,42) from the inner face either side of the channel (32) that define a recess for receiving the protrusions (33, 34) of the first half (31) of the retainer. The opposing surfaces of the two pairs of protrusions (39,40,41,42) are contiguous with the side walls of the channel (38) and each have a contoured surface (43,44,46,47).

The contoured surfaces (35,36,43,44,46,47) may be complementary to the surface of a preselected mooring line or simply serrated. When the contoured surfaces are complementary to the surface of a preselected mooring line the avoidance of slippage is most effectively achieved with the use of 4-, 5-, or

6-strand wire rope mooring lines.

The surfaces of the faces of the first half (31) and the second half (37) of the retainer are complementary and the outer surface of the first half (31) and second half (37) of the retainer are curved so that when the halves (31,37) are interlocked, the body of the retainer is formed as a truncated cone through which the mooring line (25) passes and is held in a vice-like grip when the retainer is housed within the receiver.

Referring to Figures 14 and 15 the interlocking of the first and second halves (31,37) and engagement of the retainer thus formed with a mooring line (25) is shown. In Figure 14 the inner faces of the first and second half of the retainer (31,37) are shown before engagement of the retainer with the mooring line (25). The receiver (12) is shown as a tapered collar. However, it will be recognised that the receiver (12) merely needs to be a rigid body that provides a truncated conical void tapering from an upper face of the rigid body to a lower face of the rigid body. The retainer is dimensioned to substantially fill this void. In Figure 15 a cross-sectional view of the interlocking first and second halves of the retainer (31,37) engaging the mooring line (25) and the retainer then being secured in position by the receiver (12) is shown. The deployment of the aquaculture apparatus (24) as shown in Figure 10 using this retainer (31,37) and receiver (12) assembly has been found to be capable of tolerating water current velocities of 40 cm/s and waves of 5 metre height.

When the aquaculture apparatus (24) is to be inspected or harvested the procedure for deployment may be repeated, but in reverse. For example, the hook of a sea crane may be attached to the aquaculture apparatus and, if required to facilitate disengagement with the mooring line, weights temporarily attached to the threaded aquaculture apparatus and the two halves of the retainer (31,37) withdrawn from the receiver (12) thereby allowing the aquaculture apparatus (24) to be drawn to the surface. In some circumstances the buoyancy provided by the float sleeve may be sufficient to cause the aquaculture apparatus (24) to rise to the surface once the retainer is withdrawn from the receiver (12) without the need to use a sea crane.

At the surface, and in the absence of any weighting, the buoyancy provided by the interlocking float bodies (14) of the float sleeve mounted on the axle (4) will cause the aquaculture apparatus (24) to be oriented so that the length of the axle (4) is substantially parallel to the surface as shown in Figure 11. Each of the cultivation racks (18,19) may then conveniently be inspected by simply rotating the aquaculture apparatus (24) about this axis. This feature of the aquaculture apparatus and its use obviates the need to lift the aquaculture apparatus (24) out of the water, thereby increasing the efficiency of operation and maintenance. Once deployed, the aquaculture apparatus can be periodically inspected from the deck of a barge without the need for specially designed vessels.

Although the apparatus, assembly and their use have been described with reference to exemplary embodiments it will be appreciated that variations and modifications may be made to these embodiments without departing from the scope of the invention. Where known equivalents exist to specific elements, features or integers of the aquaculture apparatus and its use, such equivalents are incorporated as if specifically referred to in this description. Unless specifically disclaimed, variations and modifications to the described embodiments that include elements, features or integers disclosed in and selected from the referenced publications are within the scope of the invention and are hereby incorporated by reference. The advantages provided by the described embodiments may be provided in the alternative or in combination in different embodiments of the invention.

INDUSTRIAL APPLICABILITY

An apparatus, assembly and method for their use in the cultivation of marine species in open ocean environments is provided.

REFERENCED PUBLICATIONS

Buck and Buchholz (2007) Support device for the cultivation of macro organisms in marine waters United States patent application no. 10/590,879 [publ. no. US 2007/0193115 Al].

Buck and Langan (2017) Aquaculture perspective of multi-use sites in the open ocean - the untapped potential for marine resources in the Anthropocene. Springer International Publishing AG.

Buck et al (2018) State of the art and challenges for offshore integrated multi-trophic aquaculture (IMTA) Frontiers in Marine Science, 5, Article 165, 121

Bugrov et al (1994) Submersible cage device for fish farming International application no. PCT/RU96/00222 [publ. no. WO 98/06254.

Burgess (1997) Submersible platforming for fish-farming United Kingdom patent no. 2302525A.

Cortinas and Arbones (2006) Submersible farm International application no. PCT/ES03/00316 [publ. no. US 2006/0037551 Al].

Cortinas and Arbones (2008) Submersible farm United States patent no. US 7,341,021 B2.

Cortinas and Arbones (2010) Submersible farm United States patent no.

7,650,856 B2.

Costa-Pierce (2016) Ocean foods ecosystems for planetary survival in the Anthropocene. In E.M. Binder (Ed.), World Nutrition Forum: Driving the Protein Economy (pp. 301-320). Austria: Erber, AG.

Heasman (2014) A releasably submersible [sic] float assembly and its use in aquaculture international application no. PCT/NZ2014/000008 [publ. no. WO 2014/116123 A2].

Leslie and Young (2011) Aquaculture assembly and method International application no. PCT/AU2011/000402 [publ. no. WO 2011/123895 Al].

Thorvardarson et al (2011) Submersible cage and system for fish farming United States patent application no. 12/514,574 [publ. no. US 2011/0126447 Al]. INCORPORATION BY REFERENCE

Where the claims, description or drawings of this specification are missing in their entirety or part, the corresponding portion of the specification accompanying the most recently filed application from which priority is claimed is to be incorporated by reference so as to complete this specification in accordance with Rules 4.18, 20.5 and 20.6 of the PCT Regulations (as in force from 1 July 2015 and subsequently amended).

For the purposes of 37 C.F.R. 1.57 of the United States Code of Federal Regulations the disclosures of the following publications (as more specifically identified under the heading "Referenced Publications") are incorporated by reference: Buck and Langan (2017) and Heasman (2014).

Claims

1) A buoyant aquaculture apparatus for use with a single mooring line comprising:

(a) an upper end frame and a lower end frame mounted around opposite ends of an open-ended hollow axle so that the mooring line may pass freely through the hollow of the axle;

(b) three or more evenly spaced apart beams each attached orthogonally between corresponding positions on the periphery of each of the upper and lower end frames;

(c) one or more cultivation racks each releasably mounted between a pair of mountings located at corresponding positions on the periphery of each of the upper and lower end frames midway between the positions where the beams are attached; and

(d) a float sleeve mounted around the axle.

2) The apparatus of claim 1 where the float sleeve comprises a plurality of interlocking float bodies releasably mounted around the axle.

3) The apparatus of claim 1 or 2 where a guide for the mooring line is mounted around the lower end of the open-ended axle.

4) The apparatus of any one of claims 1 to 3 where a receiver for a retainer for releasably engaging the mooring line is mounted around the upper end of the open-ended axle.

5) An assembly for releasably engaging a mooring line comprising a receiver and a retainer where:

(a) The receiver is a first rigid body having an upper face and a lower face and a truncated conical void tapering from the upper face of the first rigid body to the lower face of the first rigid body and dimensioned to allow the mooring line to pass freely through the first rigid body;

(b) The retainer is a second rigid body dimensioned to substantially fill the conical void of the receiver and consisting of two or more interlocking parts; and

(c) The interlocking parts interlock to form an open-ended hollow dimensioned to accommodate the mooring line and having contoured opposing inner surfaces that engage the mooring line in a vice-like grip.

6) The assembly of claim 5 where the contoured opposing inner surfaces are serrated opposing inner surface. 7) The assembly of claim 5 or 6 where the two or more interlocking parts are two asymmetric interlocking halves.

8) A method of culturing marine species in open ocean comprising:

(a) Passing the free end of an anchored mooring line through the open- ended hollow axle of the apparatus of any one of claims 1 to 4 to provide a threaded apparatus;

(b) Immersing the threaded apparatus to a depth between 5 and 15 metres below the surface of the open ocean to provide a submerged apparatus; and

(c) Releasably engaging the mooring line with a retainer to prevent the submerged apparatus rising above the depth.

9) The method of claim 8 where a receiver for the retainer is mounted around the upper end of the open-ended axle of the apparatus.

10) The method of claim 9 where the retainer comprises an asymmetric pair of interlocking halves that engage the mooring line in a vice-like grip.

11) A system for the open ocean cultivation of one or more marine species comprising the aquaculture apparatus of claim 4 and a mooring line anchored to the seabed where the mooring line passes through the open- ended hollow axle of the apparatus and the apparatus is held submerged at a depth between 5 and 15 metres below the surface of the ocean by the assembly of claim 7.

12) The system of claim 11 where the marine species are selected from the group consisting of: bivalve molluscs and macroalgae.