WO2023021047A2

WO2023021047A2 - Aquaculture pen

Info

Publication number: WO2023021047A2
Application number: PCT/EP2022/072879
Authority: WO
Inventors: Stewart Graham
Original assignee: Stewart Graham
Priority date: 2021-08-16
Filing date: 2022-08-16
Publication date: 2023-02-23
Also published as: WO2023021047A3; CA3229144A1

Abstract

An aquaculture pen comprises a sidewall, a base, and a frame. The frame can be, for example, a sinker tube. The pen is configured such that the frame is submerged, in use. A lower edge of the sidewall and an outer edge of the base are continuously attached to the frame, such that the sidewall and base together at least partly define an enclosure for aquaculture.

Description

Aquaculture Pen

FIELD OF THE INVENTION

This invention pertains generally to the field of aquaculture. It has been developed for use in enclosure-based finfish farming, and will be described with reference to that application. However, the skilled person will appreciate that the invention may be applied to other forms of aquaculture.

BACKGROUND OF THE INVENTION

One form of aquaculture involves an enclosure that is substantially submerged within a body of water, such as the sea or a lake. Aquatic animals, including finfish such as salmon, can be raised within the controlled environment of the enclosure.

Such enclosures can include an upper frame from which an enclosure is suspended. A sinker tube can connect to and surround a lower portion of the enclosure. The sinker tube provides downward tension on the enclosure, as well as preventing the wall from moving inwards and reducing a volume of the enclosure.

SUMMARY OF THE INVENTION

In accordance with a first aspect, there is provided an aquaculture pen comprising a sidewall, a base, and a frame (or rigid structural support element, optionally discrete), the pen being configured such that the frame is submerged, in use, wherein a lower edge of said sidewall and an outer edge of said base are continuously attached to said frame, such that the sidewall and base together at least partly define an enclosure for aquaculture.

The use of a separate sidewall and base may offer various advantages compared to single-piece constructions, such as easier installation, the flexibility to combine different sidewall and base materials, and/or more flexible maintenance options. The frame (or rigid structural support element, optionally discrete) may include an outer surface, at least a part of the outer surface partly defining the enclosure.

The frame may comprise a first flange, and the lower edge of said sidewall may be attached to the first flange. This may allow for convenient attachment of the lower edge of the sidewall to the frame.

The first flange may be continuous along the length of the frame. This may allow for a relatively continuous join between the lower edge of the sidewall and the frame.

The first flange may extend upwards, in use.

The aquaculture pen may comprise one or more clamps that clamp the lower edge of said sidewall to said first flange.

The outer edge of the base may be attached to the first flange.

The frame may comprise a second flange and the outer edge of the base may be attached to the second flange. This may allow for convenient attachment of the outer edge of the base to the frame.

The second flange may be continuous along the length of said frame. This may allow for a relatively continuous join between the outer edge of the base and the frame.

The second flange may extend away from frame at an angle of from 0° to 90° downwards, relative to the horizontal. This may help reduce lateral forces on the second flange due to tension from the base.

The aquaculture pen may comprise one or more clamps that clamp the outer edge of said base to said second flange.

The sidewall may be substantially impermeable to sea lice, algal blooms or jellyfish. Optionally, the sidewall may be substantially impermeable to water.

The base may be substantially impermeable to sea lice, algal blooms or jellyfish. Optionally, the base may be substantially impermeable to water.

The sidewall and/or the base may be substantially formed from a flexible material. For example, the sidewall and/or the base may be substantially formed from a fabric and/or film. For example, the sidewall and/or base may be made from panels that are welded and or sewn together to form the required size and shape.

In accordance with a second aspect, there is provided an aquaculture pen comprising: a wall at least partly defining an enclosure for aquaculture; a frame (or rigid structural support element, optionally discrete) to which the wall is connected, the frame configured to be submerged in use; and a water pump configured for pumping water from outside the enclosure into the enclosure, the water pump comprising an impeller, wherein at least the impeller of the water pump is attached to, and at least partly supported by, the frame.

Attaching at least the impeller to the frame may improve efficiency, because the impeller is closer to the source of the water it is pumping. This may also reduce a distance that water must be pumped and reduce the pumped head.

The water pump may be configured to pump the water such that it passes through the frame. This may provide a convenient route for the water that does not require it to pass through an aperture in the wall. This may be of particular advantage when the wall at or adjacent the frame is formed from a flexible material, such as a fabric and/or film.

The aquaculture pen may comprise a conduit, the conduit comprising an inlet situated outside the enclosure and an outlet situated inside the enclosure, the pump being connected to, and configured for, pumping the water through the frame via the conduit. This may provide a relatively short path for water to traverse and/or offer support and/or protection to the conduit as it enters the enclosure.

The conduit may extend in a generally radial direction through the frame.

The outlet may be angled such that the water is pumped into the enclosure with a tangential component. This may assist in mixing incoming water with water held within the enclosure. The outlet may be angled such that the water is pumped into the pen with a vertically upward component. This may assist in mixing incoming water with water held within the enclosure.

The inlet may be disposed below the frame, in use. This may allow for water to be sourced at a depth below the frame, where the water may have fewer pests such as sea lice.

The aquaculture pen may comprise a plurality of the water pumps. Optionally, these may be distributed around a periphery of the aquaculture pen, which may assist in mixing incoming water with water held within the enclosure.

A pumping capacity of the water pumps may be sufficient that if one or more of the water pumps is inoperable, the remaining pumps are able to supply sufficient water to the enclosure. Such redundancy may help reduce downtime and increase safety, which may be of additional concern if the pumps are submerged at substantial depth.

The aquaculture pen may comprise a plurality of sets of the water pumps, wherein a pumping capacity of the water pumps is sufficient that if one or more water pumps within one of the sets is inoperable, the pumps of the remaining set or sets are able to supply sufficient water to the enclosure.

The frame may extend around the walls and the walls may comprise a sidewall and a base. A lower edge of the sidewall and an outer edge of the base may be continuously attached to frame, such that the sidewall and base together at least partly define the enclosure.

The use of a separate sidewall and base may offer various advantages compared to single-piece constructions, such as easier installation, the flexibility to combine different sidewall and base materials, and/or more flexible maintenance options.

The water pump may be attached to, and at least partly supported by, the frame.

At least the impeller of the water pump may be positioned, in use, at least 5 metres below a surface level of the water outside the aquaculture pen. Optionally, the impeller may be positioned at least 10 or even 15 metres below the water level. The water pump may be positioned, in use, at least 5 metres below a level of the water outside the aquaculture pen.

At least the impeller of the water pump may be positioned, in use, at a depth greater than 30% of a maximum draft of the aquaculture pen.

The water pump may be positioned, in use, at a depth greater than 30% of a maximum draft of the aquaculture pen.

The aquaculture pen may be configured such that water pumped by the pump travels to a depth no higher than 30% of a maximum draft of the aquaculture pen before it enters the enclosure. By limiting the amount by which water is raised, power requirements may be reduced.

The frame may comprise (or may be) a sinker tube to which the wall is connected.

The wall may comprise a sidewall and a base, wherein a lower edge of the sidewall and an outer edge of the base are continuously attached to the frame, such that the sidewall and base together at least partly define the enclosure.

The frame may include an outer surface, at least a part of the outer surface partly defining the enclosure.

In accordance with a third aspect, there is provided a method of supplying water into an enclosure of an aquaculture pen, the method comprising: using a pump, extracting water from outside the enclosure; and passing the water through the enclosure at a depth greater than 30% of a maximum draft of the aquaculture pen.

By limiting the amount by which water is raised relative to the aquaculture pen, power requirements may be reduced.

The aquaculture pen may comprise a frame (or rigid structural support element, optionally discrete) for supporting the wall, the frame being submerged in use, the method comprising passing the water through the frame.

The frame may comprise (or may be) a sinker tube, and the method may comprise passing the water through the sinker tube.

The method may comprise passing the water through a conduit passing through the sinker tube. In accordance with a fourth aspect, there is provided an aquaculture pen comprising: a wall at least partly defining an enclosure for aquaculture; and a water pump configured for pumping water from outside the enclosure into the enclosure, the water pump comprising an impeller, wherein at least the impeller of the water pump is positioned, in use, at least 5 metres below a surface level of the water outside the aquaculture pen.

The impeller may be positioned, in use, at least 10 metres below a surface level of the water outside the aquaculture pen.

The water pump may be positioned, in use, at least 5 metres below a surface level of the water outside the aquaculture pen.

The aquaculture pen may be configured such that water pumped by the pump travels to a depth no higher than 30% of a maximum draft of the aquaculture pen before entering the enclosure.

In accordance with a fifth aspect, there is provided a pen including a wall, a sinker tube, and an impeller, where the impeller is within 5 metres’ vertical distance of the sinker tube. For example, the impeller can be within 1 metre’s vertical distance of the sinker tube. Optionally, the impeller can be located within a housing that is at least partly supported by the sinker tube. Optionally, the impeller can form part of a pump, the pump comprising a motor for driving the impeller.

In accordance with a sixth aspect, there is provided an aquaculture pen comprising: a flexible wall at least partly defining an enclosure for aquaculture; an upper flotation frame to which an upper portion of the wall is connected; a lower frame attached to the wall to assist in maintaining a configuration of the wall; and a mooring system, the mooring system comprising: at least two first bridles, each first bridle being connected between the upper flotation frame and a corresponding first bridle connection point radially outward of the upper flotation frame; and at least two second bridles, each second bridle being connected between the lower frame and a corresponding second bridle connection point positioned radially outward of the lower frame; the mooring system being configured such that the lower frame can be raised towards the upper flotation frame without disconnecting the bridles.

The lower frame may comprise a sinker tube.

The upper frame may provide buoyancy such that the aquaculture pen is net positively buoyant.

The or each first bridle connection point may be connected to a plurality of the first bridles.

The or each second bridle connection point may be connected to a plurality of the second bridles.

The aquaculture pen may comprise a plurality of the first bridle connection points circumferentially spaced around the aquaculture pen, and a plurality of the second bridle connection points circumferentially spaced around the aquaculture pen.

At least one first bridle connection point may be coincident with at least one second bridle connection point.

At least one of the first and/or second bridle connection points may be disposed at a depth around halfway between the upper and lower frames.

At least one of the first bridle connection point and/or the second bridle connection point may be anchored.

The first bridle connection point and/or the second bridle connection point may be anchored to a sea floor, riverbed, or lakebed, or connected to a bridle connection point of an adjacent aquaculture pen.

The aquaculture pen may be configured such that, as the second frame is raised towards the first frame, an angle between the or each first bridle and an adjacent the or each second bridle in a vertical plane reduces. An average length of the or each first bridle may be less than or equal to an average length of the or each second bridle.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects and implementations will now be described, without limitation and by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of an aquaculture pen;

Figure 2 is a side elevation view of the aquaculture pen of Figure 1;

Figure 3 is a cutaway view of the aquaculture pen of Figures 1 and 2;

Figure 4 is detailed perspective view of a lower edge of the aquaculture pen of Figures 1 to 3;

Figure 5 is a detailed sectional view of a sinker tube of the aquaculture pen of Figures 1 to 4;

Figures 6 to 9 are detailed sectional views of sinker tubes of other aquaculture pens;

Figures 10 to 13 are detailed sectional views of sinker tubes and pumps of yet other aquaculture pens;

Figure 14 shows a method of supplying water into an enclosure of an aquaculture pen;

Figures 15 to 17 are plan views of aquaculture pens comprising bridles;

Figures 18 and 19 are a vertical sectional view through one side of an aquaculture pen comprising bridles;

Figures 20 and 21 show a schematic vertical section through one side of a further aquaculture pen comprising bridles;

Figures 22 and 23 show a schematic vertical section through one side of a further aquaculture pen comprising bridles; and

Figures 24 and 25 show a schematic vertical section through one side of a further aquaculture pen comprising bridles. DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows an aquaculture pen 100 comprising a sidewall 102 and a base 104. An upper edge of sidewall 102 is connected to a circular float structure 106, which in the illustrated example comprises concentric hollow tubular rings 107 that provide structure and buoyancy to the aquaculture pen as a whole. Rings 107 are joined by brackets 108, and together provide a structure upon which other elements of aquaculture pen 100 can be mounted. For example, walkways, handrails, frame elements for mounting anti-bird netting, and the like can be mounted to rings 107 and/or brackets 108.

Rings 107, brackets 108, and other elements of float structure 106 can be formed from any suitable material, such as a polymer (e.g., UV-stabilised polyethylene), metal (e.g., aluminium or galvanized steel), composites (e.g., glass or plastic fibre reinforced plastics or resin), or any combination of suitable materials.

Sidewall 102 is generally cylindrical, extending generally vertically downward from where it is attached to circular float structure 106, with a slight inward curve in section.

Sidewall 102 is formed from a flexible material, such as a woven or non-woven fabric or film. For example, sidewall 102 can be formed from a woven synthetic fabric having a non-permeable coating. A specific example is a woven polyester fabric with a PVC coating, although other types and combinations of materials can be used depending upon the needs of the implementation.

In the illustrated example, sidewall 102 is substantially impermeable to water. This prevents water from inside pen 100 from leaking into the surrounding water. This may help reduce the impact of, for example, food and waste products on the surrounding environment. The impermeable nature of sidewall 102 also prevents pests such as sea lice, algae, and jellyfish from entering pen 100.

In other examples, sidewall 102 is not impermeable to water. Allowing at least some water to pass through sidewall 102 enables, for example, oxygenated water to enter the pen, reducing the need for pumped, oxygenated water. The permeability of sidewall 102 in this example may be achieved by forming at least some of sidewall 102 from netting, a more open-weave fabric, or a porous woven or non-woven fabric or film, or any combination of such materials.

The skilled person will appreciate that the particular pests to be targeted, and hence the desired permeability of sidewall 102 and base 104, will vary depending upon such factors as the geographical location of pen 100, the time of year, the species being grown within pen 100, and whether pen 100 is located within salt, fresh or brackish water, for example.

Base 104 is generally conical, tapering downwards to a sump 110. Material such as faeces, uneaten food, and dead fish sink towards sump 110. An extract conduit 112 extends from a service barge (not shown) and terminates within sump 110. Extract conduit 112 is used to suck water and material from within sump 110 out of pen 100 for processing.

Sump 110 may be weighted to help base 104 maintain its conical shape. Alternatively, if a head of water is maintained within pen 100, the pressure caused by the head of water may be sufficient to allow base 140 maintain its conical shape.

Mooring lines 105 are used to moor pen 100 in position, as described in more detail below. Buoys 200 are connected at outer ends of mooring lines 105, as described in more detail below.

Base 104 may be formed from a flexible material. In one implementation, base 104 is formed from the same material as sidewall 102. Alternatively, base 104 is formed from a different material. For example, sidewall 102 can be formed from a material that is slightly permeable to water, but still keeps out pests, whereas base 104 can be formed from a water-impermeable material to prevent solutes generated by waste material sitting on base 104 from diffusing into the surrounding water. Any suitable combination of materials can be used for sidewall 102 and base 104.

Pen 100 includes a frame that, in the illustrated example, comprises a sinker tube 114. A lower edge of sidewall 102 and an outer edge of base 104 are connected to sinker tube 114, as described in more detail below. Sinker tube 114 is a circular tubular member that is negatively buoyant, such that it provides a downward force that maintains sidewall 102 in tension. Negative buoyancy may be provided by weighting the tube with, for example, chains, cable, or any other mass-providing elements. Sinker tube 114 is also supports base 104.

A lower edge of sidewall 102 and an outer edge of base 104 are continuously attached to sinker tube 114, such that the sidewall and base together at least partly define an enclosure 101 for aquaculture.

Turning to Figure 5, there is shown one way in which sidewall 102 and base 104 can be continuously attached to sinker tube 114. In this example, sinker tube 114 includes an upper flange 116 that extends upwardly from sinker tube 114. By extending upwardly in this way, upper flange 116 is approximately parallel to the vertical angle of sidewall 102 at this point, which reduces lateral forces on upper flange 116 in use. Upper flange 116 is continuous around the full circumference of sinker tube 114. Radially extending holes 118 are formed through upper flange 116 at circumferentially spaced points around sinker tube 114.

To help prevent tearing, a lower edge of sidewall 102 is folded back upon itself around a circumferentially extending stop line 121 to define an overlapping region 122. The fold can be in either direction; in this case, the edge of sidewall 102 is folded outwards. Overlapping region 122 is trapped between an inner packer 124 and an outer packer 126. Inner packer 124 is concentric with outer packer 126. Inner packer 124 and outer packer 126 can each be formed from a single piece, although in view of the size of pen 100, it may be more convenient for each of them to be formed from several arcuate pieces. Optionally, inner packer 124 and/or outer packer 126 can be formed from a compressible material, such as a resilient polymer, which may provide a more effective seal in some circumstances.

A clamping piece 128 extends along the radially outer surface of outer packer 126. As with inner packer 124 and outer packer 126, clamping piece 128 can be formed from a single piece, although in view of the size of pen 100, it may be more convenient for it to be formed from several arcuate pieces.

Inner packer 124, overlapping region 122, outer packer 126, and clamping piece 128 have radially coincident apertures formed in them that align with holes 118 in upper flange 116. A bolt 130 passes through each hole 118 in upper flange 116, then through inner packer 124, overlapping region 122, outer packer 126, and clamping piece 128. A nut 132 is threaded onto the end of bolt 130, and tightened to clamp inner packer 124, overlapping region 122 and outer packer 126 between the radially outer surface of upper flange 116 and the radially inner surface of clamping piece 128. This provides a continuous circumferential structural attachment between the lower edge of sidewall 102 and sinker tube 114, which in the described implementations also forms a sealed joint between the side wall and the sinker tube. By way of non-limiting example, one definition of “continuous” in this context is that the attachment is not significantly less water- impermeable than the material from which the sidewall is formed.

In the Figure 5 example, sinker tube 114 also includes a second flange in the form of a lower flange 134 that extends from sinker tube 114. Lower flange 134 extends away from sinker tube 114 at an angle such that lower flange 134 is approximately parallel to the angle at which it joins the edge of base 104, which reduces lateral forces on lower flange 134 in use. In the illustrated example, lower flange 134 extends at an angle of approximately 45° to the horizontal, although any suitable angle may be used depending upon the implementation.

Lower flange 134 is continuous around the full circumference of sinker tube 114. As with upper flange 116, radially extending holes 118 are formed through lower flange 134 at circumferentially spaced points around sinker tube 114. The outer edge of base 104 may be folded in a similar manner to that of the lower edge of sidewall 102. Similarly, an additional inner packer 124, outer packer 126, and clamping piece 128 are provided to allow joining of the outer edge of base 104 to lower flange 134, using additional bolts 130, in a similar fashion to that described in relation to the joining of lower edge of sidewall 102 to upper flange 116. This provides a continuous attachment between the outer edge of base 104 and sinker tube 114.

The skilled person will appreciate that lower flange 134 and/or upper flange 116 may be provided at any other suitable angle. As a non-limiting example, upper flange 116 may be provided at an angle of between 45° from the horizontal on the inner side of sinker tube 114, and 45° from the horizontal on the outer side of sinker tube 114. As a similarly non-limiting example, lower flange may be provided at an angle of between 0° and 90°, or more preferably between 10° and 80°, downwards from the horizontal on the inner side of sinker tube 114. The provision of the lower flange 134 and/or upper flange 116 at an angle parallel to sidewall 102 and base 104 is also optional, and any relative angle may be used depending upon the implementation.

The frame to which side 102 and base 104 are attached may include an outer surface, at least a part of the outer surface partly defining the enclosure 101. For example, in the case where the frame takes the form of a sinker tube, at least part of an outer surface between side 102 and base 104 defines part of an inner surface of the enclosure 101. In the example illustrated in Figures 1-5, an outer surface of a cross-sectional segment 136 of sinker tube 114 defines part of an inner surface of the enclosure 101. As described in more detail below, such an outer surface may also be provided where the frame does not take the form of a sinker tube.

Turning to Figure 6, there is shown an alternative implementation, in which only a single flange 138 is provided. The lower edge of sidewall 102 is attached to an upper side of flange 138, and the outer edge of base 104 is attached to a lower side of flange 138. Flange 138 is continuous around the full circumference of sinker tube 114.

As with upper flange 116 and lower flange 134, radially extending holes 118 are formed through flange 138 at circumferentially spaced points around sinker tube 114. The outer edge of base 104 and the lower edge of sidewall 102 are folded in a similar manner to that described above. Packers and clamping pieces may be provided, but are omitted for clarity.

Bolts 130 and nuts 132 clamp both the lower edge of sidewall 102 and the outer edge of base 104 to flange 138, in a similar fashion to that described in relation to the joining of the lower edge of sidewall 102 to upper flange 116, and the joining of the outer edge of base 104 to lower flange 134. This provides a continuous attachment between the lower edge of sidewall 102, outer edge of base 104 and sinker tube 114. The skilled person will appreciate that flange 138 may be provided at any other suitable angle. As a non-limiting example, flange 138 may be provided at an angle of between the vertical and the horizontal on the inner side of sinker tube 114. Flange 138 will not extend parallel to both sidewall 102 and base 104 when they are not themselves parallel to each other.

In relation to Figure 6, the skilled person will appreciate that the direction that the lower edge of sidewall 102 and the outer edge of base 104 approach flange 138 allows for them to be joined to flange 138 from outside the enclosure. That is, bolts 130 can be passed through the holes in one of sidewall 102 and base 104, then through flange 138, and the other of sidewall 102 and base 104, before nut 132 is threaded into place and tightened. Alternatively, overlapping regions 122 of the edges of sidewall 102 and base 104 can be turned inwards towards the enclosure, in which case they are joined from within the enclosure.

Although upper flange 116, lower flange 134, and flange 138 are continuous in the described examples, they may also be discontinuous in other implementations.

Turning to Figures 7 and 8, there are shown implementations in which the frame is not a sinker tube. In these cases, a sinker tube or other weighting system can still be provided, but the sinker tube itself does not form the primary structural frame to which sidewall 102 and base 104 is directly connected.

As shown in Figure 7, a frame is provided in the form of a generally annular strip 140. Strip 140 is formed from any suitable material or combination of materials, such as a polymer, aluminium, or galvanised steel. Strip 140 is generally circular in plan, although any other suitable shape is possible. Strip 140 defines an upper flange 116, and a lower flange 134. The lower edge of sidewall 102 is connected to upper flange 116, in a similar fashion to that described above in relation to Figures 1-5. Similarly, the outer edge of base 104 is connected to lower flange 134, in a similar fashion to that described above in relation to Figures 1-5. A conduit 142 passes radially through strip 140, for passage of pumped water as described in relation to further embodiments below. However, conduit 142 may be omitted in other implementations.

An alternative implementation of strip 140 is shown in Figure 8, in which the lower edge of sidewall 102 and the outer edge of base 104 are attached directly to opposites side of strip 140. An inner packer 124, outer packer 126, and clamping piece 128 are provided, but are omitted for clarity. An optional anchoring ring 144 is shown, allowing for attachment to a sinker tube, mooring lines, or any other mechanism that allows the weighting and/or mooring of strip 140. An anchoring ring 144 can also optionally be used with all other implementations and potential embodiments.

An advantage of the arrangement of Figure 8 over that of other described implementations is a reduction in the amount of material required for the frame, which potentially reduces manufacturing costs.

The skilled person will appreciate that strip 140 may be disposed at any suitable angle in cross-section, and may have a different cross-sectional shape, including arrangements in which the faces to which sidewall 102 and base 104 are attached are not parallel.

Turning to Figure 9, there is shown an implementation in which flanges are not used. Instead, the lower edge of sidewall 102 and the outer edge of base 104 are attached directly to sinker tube 114. Optionally, one of sidewall 102 and base 104 can be attached by way of a flange, while the other is attached directly to the frame. Similar alternatives apply when the frame does not take the form of a sinker tube.

Further implementations will now be described with reference to Figures 10-13, in which like features are designated with corresponding reference numerals.

Referring to Figure 10, pen 100 includes a wall 148 at least partly defining the enclosure 101 for aquaculture. Wall 148 can comprise, for example, the combination of sidewall 102, base 104, and segment 136. However, this is not strictly a requirement, and any suitable combination of walls may be used for the implementations described in relation to Figures 10-13. For example, a single- piece wall arrangement may be used, optionally formed from several panels joined together. Such joining may be performed in any suitable manner, such as stitching, heat or ultrasonic welding, stapling, or by way of adhesives. In particular, any downwardly-depending sidewall need not be joined to a base by way of a frame, as was described in relation to earlier implementations.

A frame is provided, to which the wall 148 is connected. In Figure 10, the frame takes the form of sinker tube 114, and this may provide particular advantages in certain specific implementations, as discussed in more detail below. However, the skilled person will appreciate that the frame need not take the form of a sinker tube.

Pen 100 includes a water pump 150, configured for pumping water from outside enclosure 101 into enclosure 101. In the implementation of Figure 10, water pump 150 is attached to, and supported by, a frame in the form of sinker tube 114.

Pump 150 can be attached to sinker tube 140 in any suitable manner. For example, in the implementation of Figure 10, an inner end 152 of pump 150 is bolted to sinker tube 114, using bolts 153. An outer end 154 of pump 150 is attached to sinker tube 114 by way of a bracket 155. Together, these attachments to sinker tube 114 provide support for pump 150.

Pump 150 includes an impeller 156, shown in dotted outline.

Impeller 156 is disposed within an internal passageway 158, also shown in dotted outline, within pump 150. Impeller 156 is an axial impeller, although radial or other forms of impeller may be employed.

Impeller 156 is mounted on a shaft 160, which in turn is driven by an electric motor 162. Motor 162 can be, for example, an AC or DC motor, driven by way of signals provided by way of an electric cable 164. Electric 164 extends to the surface, and terminates at, for example, a tender or other location from which motor drive signals can be provided.

Alternatively, pump 150 can be a hydraulic pump, driven by pressurised hydraulic fluid supplied over a hydraulic line from the surface.

Pump 150 is configured to pump water from outside to inside enclosure 101. For example, pen 100 may comprise a conduit 166, comprising an inlet 168 situated outside enclosure 101 and an outlet 170 situated inside enclosure 101. In the implementation of Figure 10, pump 150 is located outside enclosure 101, and conduit 166 passes through wall 148. On the other side of pump 150, conduit 166 is directed downwardly to extract water at a depth that excludes at least a substantial number of undesirable pests such as sea lice, jellyfish, and/or algae. The skilled person will appreciate that the particular pests to be targeted will vary depending upon such factors as the geographical location of pen 100, the time of year, recent weather, the species being grown with pen 100, and whether pen 100 is located within salt, fresh or brackish water, for example.

Within enclosure 101, outlet 170 is optionally angled such that the water is pumped into the enclosure with a tangential component. This may be achieved by having the conduit curve as it moves radially inwards, or a bend may be provided. Alternatively, the direction of conduit 166 through wall 148 may be selected to provide the required angle. Providing a tangential component may assist in mixing incoming water with water held within enclosure 101.

Outlet 170 is also optionally angled such that the water is pumped into the pen with a vertically upward component. This may be achieved by having the conduit curve as it moves radially inwards, or a bend may be provided. Alternatively, the direction of conduit 166 through wall 148 may be selected to provide the required angle. Providing a vertical component may assist in mixing incoming water with water held within enclosure 101.

Turning to Figure 11, there is shown an implementation in which a frame in the form of sinker tube 114 is separate from wall 148. In this case, pump 150 is still attached to, and supported by, sinker tube 114. Sinker tube 114 is connected to wall 148 by stays 172, which can take the form of a rigid or flexible member or members, including a polymer rope, chain, metal wire, or solid state, connected at one end to sinker tube 114 and at the other end to wall 148. In this way, the form of wall 148, and thereby enclosure 101, is maintained without sinker tube 114 forming part of enclosure 101.

Turning to Figure 12, there is shown an implementation similar to that of Figure 11, except that pump 150 is located inside enclosure 101. In this case, conduit 166 passes through wall 148, and is attached to, and at least partly supported by, a frame in the form of sinker tube 114. Conduit 166 in turn supports pump 150 within enclosure 101.

The earlier-described implementations Figures 1-5, 7, and 9 show arrangements in which conduit 166 passes through a frame in the form of sinker tube 114 or strip 140. Pump 150 can be located inside or outside enclosure 101 (e.g., as shown in Figures 10-12), or can be mounted at least partly within, or passing through, sinker tube 114 or frame 140.

Turning to Figure 13, there is shown an implementation in which pump 150 includes impeller 156, but not motor 162. In this case, motor 162 is located remotely, and drives impeller 156 by way of a flexible driveshaft 174. Pump 150, and hence impeller 156, is at least partly supported by the frame. Driveshaft 174 includes a sheath that encloses a central drive member. This allows motor 162 to be located closer to a surface of the water within which pen 100 is situated. For example, motor 162 can be mounted to float structure 106, or even on a tender or barge (not shown). This allows for quicker and easier replacement of motor 162 in the event of damage or the need for maintenance. Motor 162 may also be made more cheaply when it does not need to be submersed at depth, due to less onerous sealing and operational requirements.

Locating at least impeller 156, and optionally motor 162, beneath the water reduces the total distance that water must be pumped. In particular, there is a reduction in total height to which water must be pumped, compared to, for example, pumping water all the way up and over float structure 106.

There may be additional advantages when the pump or conduit passes through a frame, such as a sinker tube 114 or strip 140. Because the frame offers structure, it provides support to the pump or conduit passing through it. This may be of particular advantage when the wall at or adjacent the frame is formed from a flexible material, such as a fabric and/or film, as it may not be desirable or even possible to adequately support the pump or conduit with such flexible material. Even if the flexible material is capable of supporting the pump or conduit, there may be issues with sealing around the pump or conduit, and with finishing any cut edges of the flexible material to allow passage of the pump or conduit. It will be appreciated that, although only a single pump is shown in Figures 10-13, there will often be several pumps in use.

One potential reason for the use of several pumps is that a relatively large amount of water may need to be continuously or periodically pumped into enclosure 101, depending upon the permeability of wall 148. If wall 148 is relatively impermeable, then water may need to be supplied at a high rate to enclosure 101, to provide sufficient cooling and to ensure adequate fresh oxygenated water. It may be easier to provide large volumes of water with a number of smaller-capacity pumps than with a single large-capacity pump.

Another potential reason for the use of several pumps is redundancy. If only one or two relatively large-capacity pumps are used, the failure of a single pump, or the need to maintain either or both of the pumps, drastically reduces the ability to deliver fresh water to enclosure 101.

Yet another potential reason for the use of several pumps is improved distribution of water within enclosure 101, especially when the pumps are distributed around a periphery of enclosure 101. By providing several pumps with independent outlets, fresh water can be supplied at multiple points around enclosure 101, which may reduce regions of stagnant water. Using several pumps may also improve movement of water within enclosure 101, again potentially reducing regions of stagnant water.

A pumping capacity of the water pumps may be sufficient that if one of the water pumps is inoperable, the remaining pumps are able to supply sufficient water to the enclosure. Such redundancy may help reduce downtime and increase safety, which may be of additional concern if the pumps are submerged at substantial depth.

Pen 100 may comprise a plurality of sets of the water pumps 150, where a pumping capacity of the water pumps is sufficient that if one or more water pumps within one of the sets is inoperable, the pumps of the remaining set or sets are able to supply sufficient water to the enclosure.

At least the impeller of the or each water pump may be positioned, in use, at least 5 metres below a level of the water outside the aquaculture pen. Optionally, the impeller(s) may be positioned at least 10 or even 15 metres below a water level outside the aquaculture pen. As explained above, positioning the impeller below the water surface level reduces the distance that pumped water needs to travel before reaching the inside of enclosure 101.

Where the entire pump (i.e., not just the impeller) is located at depth, the or each pump may be positioned, in use, at least 5 metres below a level of the water outside the aquaculture pen. Optionally, the pump(s) may be positioned at least 10 or even 15 metres below a water level outside the aquaculture pen.

At least the impeller(s) may be positioned, in use, at a depth greater than 30% of a maximum draft of the aquaculture pen. For example, if pen 100 has a draft of 20m, the impeller(s) are positioned at least 6m below the water.

Where the entire pump (i.e., not just the impeller) is located at depth, the or each pump may be positioned, in use, at a depth greater than 30% of a maximum draft of the aquaculture pen. For example, if pen 100 has a draft of 20m, the pump(s) are positioned at least 6m below the water.

Pen 100 may be configured such that water pumped by the pump travels to a depth no higher than 30% of a maximum draft of the aquaculture pen. For example, if pen 100 has a draft of 20m, the water pumped by the pumps travels to a depth no higher than 6m below the water.

According to yet another aspect, there is provided a pen including a wall, a sinker tube, and an impeller, where the impeller is within 5 metres’ vertical distance of the sinker tube. For example, the impeller can be within 1 metre’s vertical distance of the sinker tube. Optionally, the impeller can be located within a housing that is at least partly supported by the sinker tube. Optionally, the impeller can form part of a pump, the pump comprising a motor for driving the impeller.

Turning to Figure 14, there is provided a method 175 of supplying water into an enclosure of an aquaculture pen, such as pen 100 for example. The method comprises, using a pump, extracting 176 water from outside the enclosure; and passing 178 the water through the enclosure at a depth greater than 30% of a maximum draft of the aquaculture pen.

Where the aquaculture pen includes a frame for supporting and/or weighting the wall, the frame being submerged in use, the method comprises passing the water through the frame, for example as described in relation to some of the previous implementations.

Where the frame includes a sinker tube, the method may comprise passing the water through the sinker tube. For example, the method may comprise passing the water through a conduit passing through the sinker tube.

Returning to Figure 1, float structure 106 comprises an upper flotation frame, and sinker tube 114 comprises a lower frame that assists in maintaining a configuration of sidewall 102. Pen 100 also comprises a mooring system 180 for maintaining a position of pen 100 relative to, for example, a sea floor, riverbed or lakebed.

Mooring system 180 comprises several first bridles 182. In Figure 1, there are four radially spaced apart first sets 184 of first bridles 182, each first set 184 comprising four of first bridles 182. Each first bridle 182 is connected between float structure 106 and a corresponding first bridle connection point 186. Each first bridle connection point 186 is disposed, in plan, radially outward of float structure 106. In Figure 1, all first bridles 182 in each set 184 terminate at the same first bridle connection point 186.

Mooring system 180 also comprises several second bridles 188. In Figure 1, there are four radially spaced apart second sets 190 of second bridles 188, each second set 190 comprising four of second bridles 188. Each second bridle 188 is connected between sinker tube 114 and a corresponding second bridle connection point 192. Each second bridle connection point 192 is disposed, in plan, radially outward of sinker tube 114.

In Figure 1, each first bridle connection point 186 is coincident with one of second bridle connection points 192. For example, each first bridle connection point 186 can share a connector, such as a shackle or hoop, with one of second bridle connection points 192.

As described in more detail with reference to Figures 18 to 25, mooring system 180 is configured such that sinker tube 114 can be raised towards float structure 106 without disconnecting the bridles 182, 188.

In Figure 1, float structure 106 provides buoyancy such that aquaculture pen 100 is net positively buoyant. In other implementations, one or more additional flotation devices (not shown) may be provided, to add buoyancy to float structure 106, and pen 100 as a whole. Such flotation devices may be connected directly to float structure 106, or can be connected to float structure 106 and/or other components of pen 100 by suitable connectors, additional frame elements, cables, or the like.

In Figure 1, each first bridle connection point 186 and second bridle connection point 192 is anchored to the sea floor, riverbed, or lakebed by way of a mooring or anchoring cable (not shown). In other implementations, one or more of first bridle connection points 186 and second bridle connection points 188 can be anchored to other mooring points, such as other pens (including a bridle connection point of such any such pen), service vessels or land.

In Figure 1, at least one of the first and/or second bridle connection points is disposed at a depth around halfway between the upper and lower frames. However, in other implementations, including that of Figures 20 and 21, the first and/or second connection points can be disposed at a depth other than around halfway between the upper and lower frames. For example, the first and/or second connection points can be disposed at a depth above around halfway between the upper and lower frames.

Turning to Figure 15, there is shown a plan view of an aquaculture pen 100 that includes two diametrically opposed first bridles 182 and two diametrically opposed second bridles 188 (second bridles 188 are obscured below first bridles 182). This arrangement has the benefit of simplicity and a reduced number of bridles and connection points compared to the implementation of Figure 1, although may not be suitable for rougher conditions or situations in which continuous accurate positioning of pen 100 is required. It should be noted that buoys 200 may be employed in any of the implementations shown in Figures 15 to 25, but are omitted from those Figures for clarity.

Figure 16 shows a plan view of an aquaculture pen 100 that includes two diametrically opposed first sets 184 of two first bridles 182, and two diametrically opposed second sets 190 of two second bridles 188 (second sets 190 of second bridles 188 are obscured below first bridles 182). The additional bridles in this implementation compared to that of Figure 15 offer greater positional stability, including reduced translation and rotation of pen 100 when in use.

Figure 17 shows a plan view of an aquaculture pen 100 that includes four first bridles 182 and four second bridles 188 (second bridles 188 are obscured below first bridles 182). The additional connection points 186, 192 in this implementation compared to that of Figures 15 and 16 offer improved mooring stability due to the larger number of anchoring points.

Turning to Figure 18, there is shown a simplified schematic view of an aquaculture pen 100, showing a first bridle 182 and a second bridle 188. In this implementation, first bridle 182 and second bridle 188 are approximately the same length, and are connected at a common connection point 186, 192 that is disposed at a depth around halfway between float structure 106 and sinker tube 114. Connection point 186, 192 is anchored to the underlying sea floor (not shown) by way of an anchor line 194.

As shown in Figure 19, sinker tube 114 can be raised relative to float structure 106. This can be done for several reasons, including reducing a volume of enclosure 101 to allow for easier capture of farmed fish (e.g., for harvesting or medical treatment), or replacement or maintenance of components such as sidewall 102 or base 104.

In addition, sinker tube 114 can be raised relative to float structure 106 as part of initial commissioning of pen 100. For example, sidewall 102 and/or base 104 can be attached to sinker tube 114 while it is in the raised position shown in Figure 19, which may be quicker, more convenient, and/or safer than making such attachments when sinker tube 114 is in the lowered position shown in Figure 18. Sinker tube 114 can be raised relative to float structure 106 using any suitable mechanism. For example, one or more winches (not shown) mounted on or adjacent float structure 106 can draw sinker tube 114 towards float structure 106 using winch cables (not shown). Alternatively, or in addition, sidewall 102 can be mounted to a windlass arrangement (not shown) that rotates and winds sidewall 102 onto it to raise sinker tube 114.

Mooring system 180 is configured such that sinker tube 114 can be raised towards float structure 106 without disconnecting bridles 182, 188. In Figure 18 and 19, as sinker tube 114 is raised towards float structure 106, an angle 196 between first bridle 182 and second bridle 188 in a vertical plane reduces, approaching 0 degrees as sinker tube 114 comes close to float structure 106. The ability to raise sinker tube 114 towards float structure 106 without disconnecting bridles 182, 188 significantly simplifies the process of raising sinker tube 114.

In at least some implementations, an average length of the first bridles can be less than or equal to an average length of the second bridles. For example, Figures 20 and 21 show a simplified schematic view of an aquaculture pen 100, showing a first bridle 182 and a second bridle 188. In this implementation, first bridle 182 is shorter than second bridle 188, and they are connected at a common connection point 186, 192 that is disposed at a depth above halfway between float structure 106 and sinker tube 114. Connection point 186, 192 is anchored to the underlying sea floor (not shown) by way of an anchor line 194.

As shown in the implementation of Figures 18 and 19, sinker tube 114 can be raised relative to float structure 106. In the implementation of Figures 20 and 21, however, second bridle 188 being longer than first bridle 182 causes some slackness in second bridle 188 as sinker tube 114 rises towards float structure 106. This allows for some relative movement of sinker tube 114 in plan.

Turning to Figures 22 and 23, there is shown a simplified schematic view of an aquaculture pen 100, showing a first bridle 182 and a second bridle 188. In this implementation, first bridle 182 and second bridle 188 are the same length. In this case, however, first bridle connection point 186 is vertically offset from second bridle connection point 192. In the illustrated implementation, a connection bar 198 is disposed generally vertically. First bridle 182 is connected to an upper portion of connection bar 198, and second bridle 188 is connected to a lower portion of connection bar 198.

As shown in the implementations of Figures 18 to 21, sinker tube 114 can be raised relative to float structure 106. In the implementation of Figures 22 and 23, however, the respective angles of first bridle 182 and second bridle 188 change relative to connection bar 198. However, it is still the case that, as sinker tube 114 is raised towards float structure 106, the angle 196 between first bridle 182 and second bridle 188 in a vertical plane reduces. Angle 196 goes past 0 degrees as sinker tube 114 comes close to float structure 106.

Turning to Figures 24 and 25, there is shown a simplified schematic view of an aquaculture pen 100, showing a first bridle 182 and a second bridle 188. This implementation is similar to that shown in Figures 22 and 23, except that first bridle 182 crosses second bridle 188.

As shown in the implementations of Figures 18 to 23, sinker tube 114 can be raised relative to float structure 106. In the implementation of Figures 24 and 25, the respective angles of first bridle 182 and second bridle 188 change relative to connection bar 198.

Although first bridle 182 and second bridle 188 are shown as being similar in length in Figures 22 to 25, it will be appreciated that first bridle 182 and second bridle 188 can be of different lengths in other implementations. For example, first bridle 182 may be shorter than second bridle 188.

Although the illustrated implementations show both a first bridle 182 and a second bridle 188 at each radial position around pen 100, the skilled person will appreciate that in other implementations, one or more first bridles 182 can be radially offset from one or more second bridles 188. For example, referring to Figure 17, the upper left and lower right positions can be first bridles 182, and the upper right and lower left positions can be second bridles 188. In yet other implementations, at least some first bridles 182 can be radially coincident with second bridles 182, while one or more first bridles 182 and/or second bridles 188 are not radially coincident with any other bridle. Similar comments apply to sets 184, 190 of bridles. Although mooring system 180 has been described with reference to aquaculture pen 100 described in relation to Figures 1 to 14, the skilled person will appreciate that mooring system 180 can be applied to other aquaculture pens that use upper and lower frames. The invention has been described with reference to a number of non-limiting implementations, examples and alternatives. However, it will be appreciated that variations and modifications can be effected by a person of ordinary skill in the art without departing from the scope of the invention.

Claims

1. An aquaculture pen comprising a sidewall, a base, and a frame, the pen being configured such that the frame is submerged, in use, wherein a lower edge of said sidewall and an outer edge of said base are continuously attached to said frame, such that the sidewall and base together at least partly define an enclosure for aquaculture.

2. The aquaculture pen of claim 1, wherein said frame includes an outer surface, at least a part of the outer surface partly defining the enclosure.

3. The aquaculture pen of claim 1 or 2, wherein the frame comprises a first flange, and the lower edge of said sidewall is attached to said first flange.

4. The aquaculture pen of claim 3, wherein said first flange is continuous along the length of said frame.

5. The aquaculture pen of 3 or 4, wherein said first flange extends upwards, in use.

6. The aquaculture pen of any one of claims 3 to 5, comprising one or more clamps that clamp the lower edge of said sidewall to said first flange.

7. The aquaculture pen of any one of claims 3 to 6, wherein the outer edge of said base is attached to said first flange.

8. The aquaculture pen of any preceding claim, wherein said frame comprises a second flange and the outer edge of said base is attached to said second flange.

9. The aquaculture pen of claim 7, wherein said second flange is continuous along the length of said frame.

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10. The aquaculture pen of claim 8 or 9, wherein said second flange extends away from said frame at an angle of between 0° and 90° downwards, relative to the horizontal.

11. The aquaculture pen of any one of claims 8 to 10, comprising one or more clamps that clamp the outer edge of said base to said second flange.

12. The aquaculture pen of any preceding claim, wherein the sidewall is substantially impermeable to sea lice, algal blooms or jellyfish.

13. The aquaculture pen of any preceding claim, wherein the sidewall is substantially impermeable to water.

14. The aquaculture pen of any preceding claim, wherein the base is substantially impermeable to water.

15. An aquaculture pen comprising: a wall at least partly defining an enclosure for aquaculture; a frame to which the wall is connected, the aquaculture pen being configured such that the frame is submerged, in use; and a water pump configured for pumping water from outside the enclosure into the enclosure, the water pump comprising an impeller, wherein at least the impeller of the water pump is attached to, and at least partly supported by, the frame.

16. The aquaculture pen of claim 15, wherein the water pump is configured to pump the water such that it passes through the frame.

17. The aquaculture pen of claim 16, comprising a conduit, the conduit comprising an inlet situated outside the enclosure and an outlet situated inside the enclosure, the pump being connected to, and configured for, pumping the water through the frame via the conduit.

18. The aquaculture pen of claim 17, wherein the conduit extends in a generally radial direction through the frame.

19. The aquaculture pen of claim 17 or 18, wherein the outlet is angled such that the water is pumped into the enclosure with a tangential component.

20. The aquaculture pen of any one of claims 17 to 19, wherein the outlet is angled such that the water is pumped into the pen with a vertically upward component.

21. The aquaculture pen of any one of claims 17 to 20, wherein the inlet is disposed below the frame, in use.

22. The aquaculture pen of any one of claims 15 to 21, comprising a plurality of the water pumps.

23. The aquaculture pen of claim 22, wherein a pumping capacity of the water pumps is sufficient that if one of the water pumps is inoperable, the remaining pumps are able to supply sufficient water to the enclosure.

24. The aquaculture pen of claim 23, comprising a plurality of sets of the water pumps, wherein a pumping capacity of the water pumps is sufficient that if one or more water pumps within one of the set is inoperable, the pumps of the remaining set or sets are able to supply sufficient water to the enclosure.

25. The aquaculture pen of any one of claims 15 to 24, wherein: the frame extends around the walls; and the walls comprise a sidewall and a base, a lower edge of said sidewall and an outer edge of said base being continuously attached to said frame, such that the sidewall and base together at least partly define the enclosure.

26. The aquaculture pen of any one of claims 15 to 25, wherein the water pump is attached to, and at least partly supported by, the frame.

27. The aquaculture pen of any one of claims 15 to 26, wherein at least the impeller of the water pump is positioned, in use, at least 5 metres below a level of the water outside the aquaculture pen.

28. The aquaculture pen of any one of claims 15 to 27, wherein at least the impeller of the water pump is positioned, in use, at least 10 metres below a level of the water outside the aquaculture pen.

29. The aquaculture pen of any one of claims 15 to 28, wherein the water pump is positioned, in use, at least 5 m below a level of the water outside the aquaculture pen.

30. The aquaculture pen of any one of claims 15 to 29, wherein at least the impeller of the water pump is positioned, in use, at a depth greater than 30% of a maximum draft of the aquaculture pen.

31. The aquaculture pen of any one of claims 15 to 30, wherein the water pump is positioned, in use, at a depth greater than 30% of a maximum draft of the aquaculture pen.

32. The aquaculture pen of any one of claims 15 to 31, configured such that water pumped by the pump travels to a depth no higher than 30% of a maximum draft of the aquaculture pen.

33. The aquaculture pen of any one of claims 15 to 32, wherein the frame comprises a sinker tube to which the wall is connected.

34. The aquaculture pen of any one of claims 15 to 33, wherein the wall comprises a sidewall and a base, wherein a lower edge of said sidewall and an outer edge of said base are continuously attached to said frame, such that the sidewall and base together at least partly define the enclosure.

35. The aquaculture pen of claim 34, wherein said frame includes an outer surface, at least a part of the outer surface partly defining the enclosure.

36. A method of supplying water into an enclosure of an aquaculture pen, the method comprising: using a pump, extracting water from outside the enclosure; and passing the water through the enclosure at a depth greater than 30% of a maximum draft of the aquaculture pen.

37. The method of claim 36, wherein the aquaculture pen comprises a frame for supporting the wall, the frame being submerged in use, the method comprising passing the water through the frame.

38. The method of claim 37, wherein the frame comprises a sinker tube, and the method comprises passing the water through the sinker tube.

39. An aquaculture pen comprising: a wall at least partly defining an enclosure for aquaculture; and a water pump configured for pumping water from outside the enclosure into the enclosure, the water pump comprising an impeller, wherein at least the impeller of the water pump is positioned, in use, at least 5 metres below a level of the water outside the aquaculture pen.

40. An aquaculture pen comprising: a flexible wall at least partly defining an enclosure for aquaculture; an upper flotation frame to which an upper portion of the wall is connected; a lower frame attached to the wall to assist in maintaining a configuration of the wall; and

-31- a mooring system, the mooring system comprising: at least two first bridles, each first bridle being connected between the upper flotation frame and a corresponding first bridle connection point radially outward of the upper flotation frame; and at least two second bridles, each second bridle being connected between the lower frame and a corresponding second bridle connection point positioned radially outward of the lower frame; the mooring system being configured such that the lower frame can be raised towards the upper flotation frame without disconnecting the bridles.

41. The aquaculture pen of claim 40, wherein the lower frame comprises a sinker tube.

42. The aquaculture pen of claim 40 or 41, wherein the upper frame provides buoyancy such that the aquaculture pen is net positively buoyant.

43. The aquaculture pen of any one of claims 40 to 42, wherein the or each first bridle connection point is connected to a plurality of the first bridles.

44. The aquaculture pen of any one of claims 40 to 43, wherein the or each second bridle connection point is connected to a plurality of the second bridles.

45. The aquaculture pen of any one of claims 40 to 44, comprising a plurality of the first bridle connection points circumferentially spaced around the aquaculture pen, and a plurality of the second bridle connection points circumferentially spaced around the aquaculture pen

46. The aquaculture pen of any one of claims 40 to 45, wherein at least one first bridle connection point is coincident with at least one second bridle connection point.

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47. The aquaculture pen of any one of claims 40 to 46, wherein at least one of the first and/or second bridle connection points is disposed at a depth around halfway between the upper and lower frames.

48. The aquaculture pen of any one of claims 40 to 47, wherein at least one of the first bridle connection point and/or the second bridle connection point are anchored.

49. The aquaculture pen of claim 48, wherein the first bridle connection point and/or the second bridle connection point are anchored to a sea floor, riverbed, or lakebed.

50. The aquaculture pen of claim 48 or 49, wherein the first bridle connection point and/or the second bridle connection point are anchored to a bridle connection point of an adjacent aquaculture pen.

51. The aquaculture pen of any one of claims 40 to 50, configured such that, as the second frame is raised towards the first frame, an angle between the or each first bridle and an adjacent the or each second bridle in a vertical plane reduces.

52. The aquaculture pen of any one of claims 40 to 51, wherein an average length of the or each first bridle is less than or equal to an average length of the or each second bridle.

53. The aquaculture pen as claimed in any one of claims 1 to 14, which comprises the further features defined in any one of claims 15 to 39 and/or claims 40 to 53.

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