Field of the invention

The present invention relates to an aquaculture fish pen system and a related method.

Background

Aquaculture farming of fish frequently takes place in enclosures floating partly submerged in a body of water. Such a floating enclosure may be positioned in a lake or in sea water and is commonly termed a fish pen.

Fish pens can be divided into open fish pens and closed fish pens.

An open fish pen comprises a water-permeable enclosure, e.g. a net, forming the physical enclosure for the fish and an encircling buoyancy unit keeping the enclosure afloat. The water flows freely through the enclosure.

An open fish pen has some drawbacks. The environment inside the enclosure, e.g. water temperature and oxygen level, follows that of the body of water into which the fish pen is submerged. Also, due to the water-permeable nature of the enclosure, fish inside the enclosure are vulnerable to be infected by pathogens or parasites present in the body of water surrounding the fish pen and vice versa. A water-permeable enclosure will also release waste products, e.g. faeces, treatment chemicals and uneaten feed, into the body of water in which the open fish pen is located. Also, fish are known to escape from an open fish pen when tears are accidentally formed in the water-permeable enclosure.

A closed fish pen, by contrast, comprises a water-impermeable enclosure though which water cannot flow freely. The enclosure may be a wall of a rigid material or of a soft material in cloth form and may consist of steel, concrete, polymer material or a combination thereof. The enclosure of a closed fish pen may also be encircled by a buoyancy unit keeping it afloat but closed fish pen enclosures having integrated buoyancy unit are also known in the art, e.g. enclosures being made up of watertight fibre-glass panels with intermediate foam material to give buoyancy.

In a closed fish pen a water circulation system is used to draw water from a water source, normally the body of water in which the fish pen is located, and circulate the water through the enclosure. In the water circulation system, the temperature, oxygen level, acidity etc. of the water feed to the enclosure can be controlled and adjusted. Consequently, the environment inside the enclosure is not dependent on the outside environment in the same degree as is the case with an open fish pen. Release of waste products to the surrounding environment can also be controlled, e.g. by conduiting water drawn from the enclosure through a waste management system before it is released to the surrounding body of water, thus allowing waste and other contaminants to be separated from the water. Although closed or semi-closed fish pen systems, as compared to open fish pen systems, allow better control over the inside environment and release of waste to the outside environment, there is a continuous need for improvements.

With this challenge in mind, the present invention relates to closed or semi-closed fish pen systems and seeks to improve on such systems.

Summary of the invention

One aspect of the invention relates to an aquaculture fish pen system which comprises:

- at least one endless enclosure forming an endless tunnel;

- a water circulation system configured to circulate a body of water through the at least one endless enclosure at a controlled flow rate;

- a fish station arranged in the endless enclosure to interact with fish present in the body of water circulating through the endless enclosure; and

- an opening in the at least one endless enclosure allowing fish to be brought into and/or out of the endless enclosure.

The at least one endless enclosure may comprise a plurality of pipe sections which are interconnected to form a closed polygonal circuit.

The at least one endless enclosure may in principle have any shape or form as long as it forms a closed tunnel. The at least one endless enclosure may e.g. be generally toroidal, i.e. have a generally circular cross-section and run in a circular loop. However, the cross-section of the at least one endless need not be circular, but may be rectangular, ellipsoidal or any other shape. Also, the loop along which the at least one endless enclosure runs need not be circular, but may be rectangular, ellipsoidal or any other shape. In fact, the loop along which the at least one endless enclosure runs need not be regular but may alternatively be irregular, thus allowing the at least one endless enclosure to be laid out along a fish pen system gangway structure having a regular or an irregular shape.

The at least one endless enclosure may have a cross-sectional area which is larger than 0.2 m ² , e.g. 2 m ² .

The controlled flow rate may be within the range of 0.2-2.0 m/s and desired flow rate typically depends on the size of the fish present in the at least one endless enclosure, where larger fish typically require a larger flow rate than smaller fish.

The at least one endless enclosure may, when the fish pen system is in operation, be arranged in a horizontal plane.

The at least one endless enclosure may comprise a system for temporarily introducing a wall structure into the at least one endless enclosure across the circulating body of water, which wall structure may comprise a netting, grid, grating or lattice allowing only fish smaller than a predetermined size to pass through the wall structure.

The at least one endless enclosure may comprise an opening, which may be closable, enabling access to the interior of the at least one endless enclosure, e.g. to introduce tools into the at least one endless enclosure. Such tools may include autonomous vehicles configured to travel along the length of the at least one endless enclosure, e.g. to clean the inside walls of the at least one endless enclosure and/or remove detritus and/or dead fish. Also, such autonomous vehicles may be equipped with a netting, grid, grating or lattice and be configured to drive fish along the length of the at least one endless enclosure, e.g. to guide fish towards an opening in the at least one endless enclosure for the purpose of transferring the fish out of the endless enclosure. Also, a window may be provided in the at least one endless enclosure to enable visual inspection of the interior of the at least one endless enclosures.

The fish pen system may comprise a waste evacuation system configured to remove waste from the body of water circulating through the at least one endless enclosure.

The waste evacuation system may comprise an evacuation conduit running below and in parallel to the at least one endless enclosure and a vertical conduit segments extending upwardly from the evacuation conduit and opening into the at least one endless enclosure at the bottom thereof.

The at least one endless enclosure may comprise a first endless enclosure and a second endless enclosure, and the fish pen system may comprise at least one cross-over conduit allowing transfer of fish between the first and the second endless enclosures.

The at least one cross-over conduit may comprise a valve or a system allowing transfer of fish between the first endless enclosure and the second endless enclosure to be controlled. For example, the at least one cross-over conduit may comprise a valve allowing the first endless enclosure to be hydraulically isolated from the second endless enclosure. The cross over conduit may in addition or alternatively comprise a system for temporarily or permanently introducing a wall structure into the cross-over conduit, which wall structure may comprise a netting or a grating allowing only fish smaller than a predetermined size to pass through the cross-over conduit. Alternatively, the wall structure may comprise a netting, grid, grating or lattice allowing water but not fish to pass through the cross-over conduit. The netting, grid, grating or lattice may for example be configured such that only water free from parasites and/or pathogens is allowed to pass through the cross-over conduit. Alternatively, the wall structure may be water-impermeable, thus preventing water from passing through the cross-over conduit altogether.

The first endless enclosure and the second endless enclosure may be coaxial.

The fish station may be configured to interact with the fish by at least one of the activities of treating, counting, measuring, sorting, cleaning, diagnosing and feeding the fish, and the fish station may comprise any one of: a fish biomass measuring apparatus, a fish feeding apparatus and a fish sorting apparatus.

The fish pen system may comprise a plurality of said fish stations and the fish stations may be arranged at different positions along the circumference of the at least one endless enclosure.

The fish pen system may comprise an environment control system configured to monitor and control the environment inside the at least on endless enclosure.

The fish pen system may additionally comprise at least one water-impermeable fish pen enclosure comprising a bottom section and a side wall section forming a reservoir of water having a free surface for holding fish and a transfer conduit allowing transfer of fish between the at least one endless enclosure and the at least one fish pen enclosure, which transfer conduit may open into said opening in the at least one endless enclosure.

The at least one fish pen enclosure may be floating partially submerged in a body of water having a surface. The body of water may be a freshwater lake or the sea, i.e. a saltwater ocean. The free surface of the reservoir of water held by the fish pen enclosure may be lower than, level to or higher than the surface of the body of water in which the fish pen enclosure is partially submerged.

The transfer conduit may comprise a valve which can be closed to allow the at least one endless enclosure to be hydraulically isolated from the fish pen enclosure. The transfer conduit may in addition or alternatively comprise a system for temporarily introducing a wall structure into the transfer conduit, which wall structure may comprise a netting, grid, grating or lattice allowing only fish smaller than a predetermined size to pass through the transfer conduit.

The at least one endless enclosure may be positioned above, at or below the free surface of the reservoir of water held by the at least one fish pen enclosure.

The at least one endless enclosure may be supported by the at least one fish pen enclosure. Alternatively, the at least one endless enclosure may be arranged floating in the body of water in which the at least on fish pen enclosure is partially submerged. According to yet an alternative, the at least one endless enclosure may be arranged on land.

In the fish pen system, an endless enclosure may be connected, via said transfer conduit, to only one fish pen enclosure or, alternatively, to a plurality of fish pen enclosures. In the latter case, there will be at least one transfer conduit running between each fish pen enclosure and the endless enclosure. Correspondingly, a fish pen enclosure may be connected to only one endless conduit or, alternatively, to a plurality of endless enclosures. In the latter case, there will be a plurality of transfer conduits running from the fish pen enclosure, i.e. at least one transfer conduit to each of the endless enclosures. Consequently, any one fish pen enclosure in the fish pen system may be connected to one, two, three or more of the endless enclosures in the system and, conversely, any one endless enclosure may be connected to one, two, three or more of the fish pen enclosures in the system.

Another aspect of the invention relates to a method of farming fish in an aquaculture fish pen system, comprising the step of interacting with the fish in at least one fish station arranged in an endless enclosure forming an endless tunnel in which a body of water is circulated at a controlled flow rate.

The method may comprise the steps of:

- raising juvenile fish in the endless enclosure; and

- when the fish has grown to a predetermined size, transferring the fish from the endless enclosure to a water-impermeable fish pen enclosure for holding via a transfer conduit extending between the endless enclosure and the fish pen enclosure.

The method may comprise the steps of:

- holding the fish in a water-impermeable fish pen enclosure;

- transferring the fish from the fish pen enclosure to the endless enclosure via a transfer conduit extending between the fish pen enclosure and the endless enclosure;

- interacting with the fish in the endless enclosure using said at least one fish station; and

- after said interaction, transferring the fish from the endless enclosure back to the fish pen enclosure.

A further aspect of the invention relates to a fish pen apparatus configured to be used in a fish pen enclosure having a generally circular-cylindrical side wall section. The fish pen apparatus comprises a hub which can be shifted vertically along a central axis of the fish pen enclosure and also rotated about the axis. The fish pen apparatus also comprises radially extending arms mounted to the hub. The length of each arm is somewhat less than the radius of the fish pen enclosure, thus allowing a distal end of each arm to be positioned adjacent the side wall section. The fish pen apparatus further comprises a circular netting or grating spanning the arms and being mounted thereto. Thus, when submerged in the fish pen enclosure, the fish pen apparatus allows the reservoir of water in the fish pen enclosure to be divided into a first, upper sub-reservoir of water above the netting or grating and a second, lower sub-reservoir of water below the netting or grating.

Nets may be suspended vertically from at least two of the arms, thus dividing the lower sub- reservoir into a plurality of zones separated by the nets.

When fish is to be transferred out from the fish pen enclosure via a transfer conduit positioned in the fish pen enclosure, the fish pen apparatus may be raised or lowered to reduce the volume of the sub-reservoir in which the transfer conduit is positioned, thus allowing fish being of a size larger than the openings in the netting or grating to be shepherd towards the transfer conduit. At least one of the arms may be telescopically retractable allowing the distal end of the arm and accompanying netting or grating to be moved away from the side wall section of the fish pen enclosure, thus creating an opening in the fish pen apparatus allowing fish to swim from one of the sub-reservoirs to the other.

The distal end of each arm may be provided with a cleaning element, e.g. a scraper. By rotating the fish pen apparatus and moving it up and down along said central axis, the cleaning element can be made to bear against the side wall section of the fish pen enclosure to detach growth that may have accumulated thereon.

Also, downwardly extending cleaning elements, e.g. scrapers, may be attached to the underside of at least one of the arms. By moving the hub to a lowermost position in the fish pen enclosure and rotating the fish pen apparatus, such cleaning elements can be made to bear against a bottom section of the fish pen enclosure to detach growth that may have accumulated thereon. Such cleaning elements may also, or alternatively, be used to push detached growth and other detritus in the fish pen enclosure towards a centre of the bottom section of the fish pen enclosure and, if present, into a central recess in the bottom section, from which the growth and detritus can easily be removed using conventional means, e.g. an air lift system or a suction pump. Alternatively, at least one of the arms may be provided with a suction system comprising downwardly facing suction nozzles or openings. By rotating the arms close to the bottom section of the fish pen enclosure, detached growth and/or detritus accumulated at the bottom section can then be removed.

At least one of the arms may be provided with an oxygenation system comprising a conduit for oxygen extending along the length of the arm, which conduit has openings through which oxygen can be released into the fish pen enclosure.

When not in used, the fish pen apparatus may be lifted out of the fish pen enclosure. This will prevent unnecessary growth accumulating on the fish pen apparatus. Also, it will enable the same fish pen apparatus to be used in different fish pen enclosures, thus reducing capital expenditure.

Yet a further aspect of the invention relates to a fish pen apparatus comprising a central support positioned axially inside a generally circular-cylindrical fish pen enclosure, which fish pen apparatus further comprises a plurality of arms extending generally radially from the central support to a side wall section of the fish pen enclosure. Each arm is rotatably connected to the central support, allowing each arm to be individually rotated generally parallel to and above a free surface of a reservoir of water held by the fish pen enclosure about an axis defined by the central support.

For each arm, the fish pen apparatus comprises a generally rectangular, flexible net or mesh, which can be brought between an inactive storage position, in which the net is rolled up on the arm above the free surface, and an active, deployed position, in which the net extends from the arm down into the reservoir of water to a bottom section of the fish pen enclosure. Consequently, when the nets of the arms are deployed, the nets will divide the reservoir of water into a plurality of cylinder-sector segments.

Each arm is rotatable about its longitudinal axis and by rotating the arm about this axis, the net of the arm can be brought from the storage position to the deployed position, and vice versa. One or a plurality of sinkers may be attached to a lower end of each net to ensure that the net abuts the bottom section in the deployed position.

The fish pen apparatus may be used to round up fish, e.g. to facilitate transfer of fish out of the fish pen enclosure. In such an operation, two arms of said plurality of arms, with the nets in their respective storage position, may be rotated about the axis defined by the central support such that they are brought next to each other. Thereafter, the nets of the two arms may be deployed, i.e. lowered to the bottom section, thus dividing the reservoir of water into a first, minor cylinder-section segment and a complementary second, major cylinder-section segment. Since the two nets are deployed next to each other, no fish will become entrapped in the first cylinder-sector segment and all fish will be located in the second cylinder-sector segment.

Thereafter, at least one of the two arms are rotated about the axis A, bringing the nets 536a, 536b to separate, thus causing the volume of the first cylinder-sector segment to increase and the volume of the second cylinder-sector segment to decrease correspondingly. Upon continued rotation of the arm(s) about the axis defined by the central support, fish will be driven or guided in front of the moving net(s), thus trapping the fish in the continuously shrinking second cylinder-sector segment. The rotation of the arm(s) is continued until the density of fish in the second cylinder-sector segment has become sufficiently large to allow efficient transfer of fish out of the second cylinder-sector segment. Such transfer may for example be effectuated by pumping.

In fish pen enclosures holding fish of different sizes, the mesh size of the nets may be adopted to allow small fish to escape through the nets, thus allowing only fish larger than a predetermined size to be singled out and rounded up in the second cylinder-section segment.

Above-discussed preferred and/or optional features of each aspect of the invention may be used, alone or in appropriate combination, in the other aspects of the invention.

Description of the drawings

In the following, examples of preferred embodiments of the invention are described with reference to the accompanying drawings, in which:

Fig. 1 shows schematically a top-view of a fish pen system according to one embodiment of the invention;

Fig. 2 shows schematically a cross-sectional view of the fish pen system shown in Fig. 1; Fig. 3 shows schematically a fish pen apparatus according to a further aspect of the invention.

Fig. 4 shows schematically another embodiment of a fish pen system according to the invention.

In the drawings, like reference numerals have been used to indicate common parts, elements or features unless otherwise explicitly stated or implicitly understood by the context.

Detailed description of the invention

Figs. 1 and 2 show an embodiment of a fish pen system 110 according to the invention.

The fish pen system 110 comprises a fish pen enclosure 112 floating partially submerged in a body of water 1 14 having a surface 115. The body of water may be a freshwater lake or the sea, i.e. a saltwater ocean. The fish pen enclosure 112 comprises a bottom section 116 and a side wall section 118 forming a reservoir of water 120 for fish having a free surface 123. The side wall section 118 is generally circular-cylindrical.

In the disclose embodiment, the free surface 123 of the reservoir of water 120 is level with the surface 115 of the body of water 114 in which the fish pen enclosure 112 is partially submerged. However, in other embodiments the free surface 123 may be located above or below the surface 115.

The fish pen enclosure 112 is closed, i.e. the bottom and side wall sections 116, 118 are impermeable to water, thus preventing direct exchange of water between the reservoir 120 and the body of water 114 in which the fish pen enclosure 112 is partly submerged. However, the fish pen enclosure 112 is not covered, i.e. it is accessible from above allowing operators and equipment access to the reservoir 120.

The surface 123 of the reservoir of water 120 inside the fish pen enclosure 1 12 may but need not be at the same level as the surface 1 15 of the body of water 114 into which the fish pen enclosure 112 is partly submerged.

The bottom section 116 is made from concrete and the side wall section 118 comprises polymer elements 122 embedded in concrete providing sufficient buoyance to the fish pen system. Beams or girders 124 made from steel are spanning the outside of the bottom section 116 providing additional rigidity to the fish pen enclosure 112.

The fish pen system 110 further comprises a first, outer 126 and a second, inner 128 endless enclosure, each forming an endless tunnel. Each endless enclosure 126, 128 has a generally polygonal shape. The endless enclosures 126, 128 are supported by the fish pen enclosure 112 and are positioned in a common, generally horizontal plane generally coaxial with the fish pen enclosure 112. The outer endless enclosure 126 has a diameter which is generally the same as the diameter of the side wall section 1 18 and the inner endless enclosure 128 has a diameter which is somewhat less than the outer endless enclosure 126, thus allowing the inner endless enclosure 128 to fit adjacently inside the outer endless enclosure 126.

Each of the endless enclosures 126, 128 is configured to hold a circulating body of water 200 having a free surface 202 and the fish pen enclosure 120 and the endless enclosures 126, 128 can be brought into fluid communication with each other to allow fish to be transferred between the fish pen enclosure 120 and the endless enclosures 126, 128. Such fluid communication will be described in more detail in the following.

The fish pen system 110 comprises a water circulation system 130 configured to circulate water through the otherwise closed fish pen system 110.

The water circulation system 130 comprises a first water intake 132a and a second water intake 132b, each being provided with a water intake pump (not visible) allowing water to be drawn from the sea water column at a desired depth (or depths, as the water intakes 132a, 132b can be positioned at different depths, if desired). Via distribution conduits (not shown) water intake conduit 134a extends from water intake 132a to a plurality of water intake openings 136a in the outer endless enclosure 126 and, likewise, via distribution conduits (not shown) a water intake conduit 134b extends from water intake 132b to a plurality of water intake openings 136b in the inner endless enclosure 128 (see Fig. 1).

Each water intake conduit 134a, 134b may comprise a plurality of water intakes (not shown) at different depths along the length of the water intake conduit 134a, 134b, thus allowing water to be drawn from different depths, e.g. to control the temperature of the intake water. A control system 212 (see Fig. 2, discussed in more detail below) can be used to activate suitable water intakes to achieve desired intake water quality, e.g. temperature.

A first, lower fish pen inlet conduit 138a, 138b extends from each intake conduit 134a, 134b through the side wall section 118 and opens into the fish pen enclosure 112 close to the bottom section 116. Also, a second, upper fish pen inlet conduit 140a, 140b extends from each intake conduit 134a, 134b through the side wall section 118 and opens into the fish pen enclosure 112 at the upper part of the reservoir 120.

Valves 142a, 144a, 146a and 148a are arranged in conduits 134a, 138a and 140a allowing intake water to be pumped from the intake 132a to the fish pen enclosure 1 12 and/or to the outer endless enclosure 126. Also, valves 142b, 144b, 146b and 148b are arranged in conduits 134b, 138b and 140b allowing intake water to be pumped from the intake 132b to the fish pen enclosure 112 and/or to the inner endless enclosure 128.

The water circulation system 130 further comprises a water outlet 150 which is in fluid communication with a water outlet pump 152 via a water outlet conduit 154. The water outlet pump 152 is connected to a lower end of a central conduit 156 which extends axially through the fish pen enclosure 112. Through-going opening 158 are provided in the central conduit 156 allowing the water outlet pump 152 to draw water from the fish pen enclosure 112. Consequently, water circulation through the fish pen enclosure 112 is achieved by pumping water into the fish pen enclosure 1 12 via conduit 134a and at least one of conduits 138a and 140a or via conduit 134b and at least one of conduits 138b and 140b, and pumping water out of the fish pen enclosure 112 via conduits 156 and 154.

Cross-over conduits 160a, 160b extend between the outer endless enclosure 126 and the inner endless enclosure 128 allowing fish to be transferred between the endless enclosures 126, 128. Valves 162a, 162b are arranged in the cross-over conduits 160a, 160b to control such transfer.

The fish pen system 110 comprises a waste evacuation system 163 configured to evacuate waste, e.g. fish faeces, uneaten feed, dead fish and other detritus, from the endless enclosure 126. The waste evacuation system 163 comprises an evacuation conduit 164 running below and in parallel to the endless enclosure 126. The waste evacuation system 163 further comprises vertical conduit segments 166 extending upwardly from the evacuation conduit 164 and opening into the endless enclosure 126 at the bottom thereof. Fish faeces, uneaten feed and other detritus will accumulate at the bottom of the endless enclosure 126 and will, by virtue of the circulating water, be brought and trapped in the openings where the conduit segments 166 open into the endless enclosure 126. Also, an autonomous vehicle (not shown) configured to travel along the length of the endless enclosure may be used to scrape detritus accumulate at the bottom of the endless enclosure 126 into the openings where the conduit segments 166 open into the endless enclosure 126.

By applying suction to the evacuation conduit 164, detritus trapped in the openings can be evacuated from the endless enclosure 126. The openings may advantageously be covered by a grating allowing detritus to enter the opening but preventing fish from doing so. Depending on the amount of detritus produced in the endless enclosure 126, suction may be applied to the evacuation conduit 164 continuously, intermittently or at regular time intervals. Via conduits not show in Fig. 4, the evacuation conduit 164 is in fluid communication with a waste disposal system 168 positioned below the fish pen enclosure 120.

A corresponding evacuation conduit (not shown) is provided below and in parallel to the inner endless enclosure 128. Consequently, detritus from both endless enclosures 126, 128 is evacuated to the waste disposal system 168.

Consequently, water circulation through the outer endless enclosure 126 is achieved by pumping water into the outer endless enclosure 126 via conduit 134a and drawing water from the outer endless enclosure 126 via conduit segments 166 and the evacuation conduit 164 positioned below the outer endless enclosure 126. Likewise, water circulation through the inner endless enclosure 128 is achieved by pumping water into the outer endless enclosure 126 via conduit 134b and drawing water from the inner endless enclosure 128 via conduit segments (not shown) and the evacuation conduit (not shown) positioned below the inner endless enclosure 128. In the fish pen enclosure 112, detritus will collect in a central recess 170. From the recess 170, the detritus may be evacuated using a gas lift system or any other conventional method known in the art. Alternatively, accumulated detritus may be transferred to the waste disposal system 168 via conduits (not shown) having valves (not shown) allowing controlled flushing of the accumulated detritus.

The fish pen system 110 comprises transfer conduits 400 allowing fish to be transferred between the fish pen enclosure 112 and the inner endless enclosure 128. The transfer conduit 400 extends between a funnel 402 submerged in the reservoir if water 120 and an opening 403 at the bottom of the inner endless enclosure 128, where the transfer conduit 400 opens. A pump 404 may be arranged in the transfer conduit 400 to raise water and fish from the pen enclosure 112 and the endless enclosure 128. Fish may also be transferred from the endless enclosure 128 to the fish pen enclosure 112 via the transfer conduits 400. Each transfer conduit 400 may comprise a system (not shown) for temporarily introducing a wall structure (not shown) into the transfer conduit 400, which wall structure may comprise a netting, grid, grating or lattice allowing only fish smaller than a predetermined size to pass through the transfer conduit. A valve (not shown) may be arranged in the transfer conduit 400 to allow the conduit 400 to be closed when no transfer of fish is to take place.

Fish may be transferred from the outer endless enclosure 126 to the fish pen enclosure 112 via peripheral transfer conduits 406a, 406b (see Fig. 1) which are connected to pen inlet conduits 140a, 140b, 138a, 138b via an intermediate conduit system (not shown).

Fish may be transferred out of and/or into the fish pen system 100, e.g. to or from a supply vessel, via transfer conduits 408a and 408b, which are connected to the outer endless enclosure 126.

The water circulation system 130 is configured to circulate the body of water 200 through each of the endless enclosures 126, 128 at a controlled flow rate, which typically may be within the range of 0.2-2.0 m/s.

Along the circumference of the endless enclosures 126, 128 there are arranged fish stations configured to interact with fish present in the body of water 200 circulating through the endless enclosures 126, 128. Fish, in particular salmonids, have a natural tendency to swim counter-current, i.e. against the direction of flowing water. Thus, by controlling the flow rate of the water circulating in the endless enclosures 126, 128, fish can be made to swim in a closed loop inside the endless enclosures 126, 128. Thereby, it can be ensured that all fish inside the endless enclosures pass a fish station at regular intervals. These intervals can be controlled by controlling the flow rate of the circulating body of water 200.

In the present embodiment, four fish stations are disclosed representing three different types of fish stations- a first fish station 204 configured to measure biomass of fish passing the fish station 204, a second fish station 206 configured to dispense feed to the fish, and a third 208 and a fourth 210 fish station configure to sort fish according to size. Consequently, the first fish station 204 comprises a fish biomass measuring apparatus, the second fish station 206 a fish feeding apparatus, and the third and fourth fish stations 208, 210 a fish sorting apparatus. Such apparatuses are, as such, known in the art and will not be described in any detail here. However, a fish sorting apparatus may typically comprise a, netting, grid, grating or lattice configured to allow only fish smaller than a predetermined size to pass. In the disclosed embodiment, the sorting apparatuses 208, 210 are positioned adjacent the cross over conduit 160a and, consequently, can be used to allow only fish smaller than a predetermined size to be transferred from one of the endless enclosures to the other, thus enabling fish to be sorted according to size in the inner and outer endless enclosures 126, 128. Advantageously, each sorting apparatus 208, 210 may comprise a system for temporarily introducing a wall structure 209, 211 into the at least one endless enclosure 126, 128 across the circulating body of water, which wall structure comprises a netting, grid, grating or lattice allowing only fish smaller than a predetermined size to pass through the wall structure.

Generally, a fish station can be configured to interact with the fish in the endless enclosures 126, 128 in one of many ways, including, but not limited to, treating, counting, measuring, sorting, cleaning, diagnosing and feeding the fish.

Consequently, the fish pen system 110 allows fish held in the fish pen enclosure 112 to be transferred to the endless enclosures 126, 128 to be e.g. measured, sorted, treated or otherwise interacted with and then released back to the fish pen enclosure 112. Also, the fish pen system 110 allows fish to be transferred to the endless enclosures 126, 128 to be sorted according to size, thus allowing fish that have reached sufficient size to be transferred out of the fish pen system 110 for further processing. The fish pen system 110 also allows young fish, e.g. fry such as salmon smolt, to be raised in one of the endless enclosures and, when they have reached a predefined size, to be transferred to the fish pen enclosure 112 for further farming.

The fish pen system 110 comprises an environment control system 212 configured to monitor and control the environment inside the endless enclosures 126, 128 to provide conditions that are beneficial for the wellbeing and efficient growth of the fish. By virtue of the endless enclosures 126, 128 being closed, the body of water 200 and the fish therein will not be directly exposed to the environment outside of the endless enclosures 126, 128. This allows the environment inside the endless enclosures to be controlled efficiently and also to be adapted to the fish inside the conduit, e.g. taking account the size and general health of the fish. Environmental parameters monitored and controlled by the environment control system 212 may include water quality parameters, e.g. parameters indicative of temperature, oxygen content, salinity, acidity, pathogen and parasite levels and clarity of the body of water 200. The environmental parameters may also include light quality parameters, e.g. the light intensity and spectral characteristics of light inside the endless enclosures 126, 128. The environment control system 212 may comprise one or a plurality of monitoring units (not shown) positioned inside the conduit to monitor the environmental parameters, e.g. thermometers and gauges configured to measure oxygen content, salinity and acidity.

In response to a deficit in one or a plurality of the water quality parameters, the environment control system 212 may instruct the water circulation system 130 to treat intake water before it is introduced into the endless enclosures 126, 128. For this purpose, the water circulation system 130 may comprise water conditioning units (not shown) positioned along the water intake conduits 134a, 134b, e.g. to oxygenate the water or to bring the water to a desired salinity and/or acidity level. The water conditioning units may also treat water to eliminate of minimize occurrence of pathogens and/or parasites in the water, e.g. bacteria, viruses and/or crustacean parasites such as salmon lice. The water conditioning units may be positioned at or adjacent the water intakes 132a, 132b and, in order to bring the water to desired quality, may comprise filters, temperature sensors, pumps and other apparatuses known in the art to be used in water treatment systems.

The endless enclosures 126, 128 comprise straight pipe sections 300 and angled pipe sections 302, each being provided with a flange at its respective end (not visible in the figures). The pipe sections 300, 302 are connected to each other by clamps 304 which enclose and secure flanges of neighbouring pipe sections 300, 302 to each other. This way of interconnecting the pipe sections 300, 302 enables easy replacement of pipe sections should this become necessary of otherwise desirable. Also, this modular design enables easy replacement of a pipe section with one type of fish station for a pipe section having another type of fish stations, thus making the system easy to configure and adapt to changed conditions.

The pipe sections 300, 320 may preferably be made from a polymer material but may alternatively be made from a metal material, e.g. aluminium or steel. In order to enable control of lighting conditions inside the endless enclosures, it may be advantageous that the endless enclosures 126, 128 are made from an opaque material.

A hatch (not shown) may be provided in at least one of the pipe sections 300, 302 to enable manual access to the interior of the endless enclosures 126, 128, e.g. to introduce tools into the endless enclosures 126, 128. Such tools may include autonomous vehicles (not shown) configured to travel along the length of the endless enclosure, e.g. to clean the inside walls of the endless enclosure and/or remove detritus and/or dead fish. Also, such autonomous vehicles may be equipped with a grating and configured to drive fish along the length of the endless enclosure 126, 128, e.g. to guide fish towards an opening in the endless enclosure for the purpose of transferring the fish out of the endless enclosure.

A window (not shown) may be provided in at least one of the pipe sections 300, 302 to enable visual inspection of the interior of the endless enclosures 126, 128.

When fish is to be transferred from the fish pen enclosure 112 to the endless enclosures 126, 128, fish in the fish pen enclosure 112 are guided towards the funnels 402 by means of a fish pen apparatus 500. The fish pen apparatus 500 comprises an annular hub 502 which is mounted about the central conduit 156 coaxially therewith. The hub 502 can be shifted vertically along the central conduit 156, e.g. preferably utilising an electric or a pneumatic actuator (not shown). The hub 502 may also be rotated about its axis, i.e. about the central conduit 156, once again preferably utilising an electric or a pneumatic actuator (not shown). The fish pen apparatus 500 also comprises radially extending arms 504 mounted to the hub 502. The length of each arm 504 is somewhat less than the radius of the fish pen enclosure 112, thus positioning a distal end of each arm 504 adjacent the side wall section 118. The fish pen apparatus 500 further comprises a circular netting or grating 506 spanning the arms 504 and being mounted thereto. Thus, the fish pen apparatus 500 allows the reservoir of water 120 to be divided into a first, upper sub -reservoir of water 508 above the netting 506 and a second, lower sub- reservoir of water 510 below the netting 508.

Also, nets (not shown) may be suspended vertically from at least two of the arms 504, thus dividing the lower sub-reservoir 510 into a plurality of zones separated by the nets.

When fish is to be transferred from the fish pen enclosure 112 to the endless enclosures 126, 128, the fish pen apparatus 500 is raised, thus reducing the volume of the upper sub-reservoir 508 and shepherding fish being of a size larger than the openings in the netting 506 towards the funnels 402.

At least one of the arms 504 may be pivotally attached to the hub 502 about a horizontal axis allowing the distal end of the arm to assume a position which is lower than the hub 502, as is illustrated by the dashed arm 504’ in Fig. 2. This will allow a proximal section of the arm 504’ to break the surface 123 when the hub 502 is raised and further reduce the volume of the upper sub-reservoir 508. The arm 504’ may be telescopically extendable, thus allowing the distal end of the arm 504’ to be kept adjacent the side wall section 118 when the arm 504’ is pivoted.

The fish pen apparatus 500 may comprise a paddle 512 attached to one of the arms 504 at a radial distance from the hub 502 corresponding to that of the funnels 402. The paddle 512 is provided with a vertical surface having an extension which is sufficient to cover the opening of a funnel 402, thus allowing the fish pen apparatus 500, when in its uppermost position as illustrated by the dashed arm 504’ in Fig. 2, to be rotated about the central axis of the hub 502 such that the paddle 512 is brought towards one of the funnels 402, thereby reducing the volume available to fish caught in the upper sub-reservoir 508 even further, thus forcing fish into the funnel 402 more effectively.

The fish pen apparatus 500 together with the endless enclosures 126, 128 also enables a flexible system for raising fish fry, in which fry is initially raised in the endless enclosures and, when the fry has reached a predefined size, are transferred to one of the sub-reservoirs in the main pen 112, where the fish pen apparatus 500 is positioned to provide a sub-reservoir volume that is suitable for the particular size of the fry. As the fish grows, the sub-reservoir volume can be increased by repositioning the fish pen apparatus 500 vertically. The fish pen apparatus 500 can further be used to separate juvenile fish from adult.

At least one of the arms 504 may be telescopically retractable allowing the distal end of the arm and accompanying netting 506 to be moved away from the side wall section 118, thus creating an opening in the fish pen apparatus 500 allowing fish to swim from one of the sub- reservoirs to the other. Of course, fish being of a size smaller than the openings in the netting 506 may pass the netting at will, also when the telescopically retractable arm or arms are not retracted.

The distal end of each arm 504 may be provided with a cleaning element 514, e.g. a scraper. By rotating the fish pen apparatus 500 and moving it up and down along the central conduit 156, the cleaning element 514 can be made to bear against the side wall section 118 to detach growth that may have accumulated thereon.

Also, downwardly extending cleaning elements (not shown), e.g. scrapers, may be attached to the underside of at least one of the arms 504. By moving the hub 502 to its lowermost position and rotating the fish pen apparatus 500, such cleaning elements can be made to bear against the bottom section 116 to detach growth that may have accumulated thereon. If the arms 504 are pivotally mounted to the hub 502, the arms 504 may, prior to the hub 502 being lowered to its lowermost position, be pivoted to assume an orientation that is parallel to the bottom section 116. Such cleaning elements may also, or alternatively, be used to push detached growth and other detritus towards the centre of the bottom section 116 and into the central recess 170, from which the growth and detritus can subsequently be removed using conventional means, e.g. an air lift system or a suction pump. Alternatively, at least one of the arms 504 may be provided with a suction system comprising downwardly facing suction nozzles or openings 518. By rotating the arms 504 close to the bottom section 116, detached growth and/or detritus accumulated at the bottom section 116 can then be removed.

At least one of the arms 504 may be provided with an oxygenation system comprising a conduit for oxygen (not shown) extending along the length of the arm, which conduit has openings through which oxygen can be released into the reservoir 120.

When not in used, the fish pen apparatus 500 may be lifted out of the fish pen enclosure 112. This will prevent unnecessary growth accumulating on the fish pen apparatus 500. Also, it will enable the same fish pen apparatus 500 to be used in different fish pen enclosures, thus reducing capital expenditure. In order to facilitate handling of the fish pen apparatus 500, the hub 502 and the arms 504 may be made from aluminium.

It is to be understood that the above-described fish pen apparatus 500 does not have to be used together with the endless enclosures 126, 128. Some or all of the features of the fish pen apparatus 500 may advantageously also be used in fish pen systems having no endless enclosures. Fig. 3 shows schematically a fish pen apparatus 520 according to a further aspect of the invention. The fish pen apparatus 520 is configured to be used in a fish pen enclosure 522 having a generally circular-cylindrical side wall section 524 and a generally circular bottom section 526 forming a reservoir of water (not shown in Fig. 3) having a free surface (not shown in Fig. 3). The fish pen enclosure 522 may for example be of the same type as the above-discussed fish pen enclosure 112.

The fish pen apparatus 520 comprises a central support 532 positioned axially inside the fish pen enclosure 522. The fish pen apparatus 520 further comprises a first and a second arm 534a, 534b extending generally radially from the central support 532 to the side wall section 524. Each arm 534a, 534b is rotatably connected to the central support 532, allowing each arm 534a, 534b to be individually rotated generally parallel to and above the free surface about an axis A defined by the central support 532, as is indicated by arrows R in Fig. 3.

For each arm 534a, 534b, the fish pen apparatus 520 comprises a generally rectangular, flexible net or mesh 536a, 536b, which can be brought between an inactive storage position, in which the net 536a, 536b is rolled up on the arm 534a, 534b above the free surface, and an active, deployed position, in which the net 536a, 536b extends from the arm 534a, 534b down into the reservoir of water to the bottom section 526. Consequently, when the nets 536a, 536b of both arms 534a, 534b are deployed, e.g. as is shown in Fig. 3, the nets 536a, 536b will divide the reservoir of water into two cylinder-sector segments 540, 542.

Each arm 534a, 534b is rotatable about its longitudinal axis and by rotating the arm 534a, 534b about this axis, the net 536a, 536b can be brought from the storage position to the deployed position, and vice versa. One or a plurality of sinkers 538a, 538b may be attached to a lower end of each net 536a, 536b to ensure that the net 536a, 536b abuts the bottom section 526 in the deployed position.

The fish pen apparatus 520 may be used to round up fish, e.g. to facilitate transfer of fish out of the fish pen enclosure 522. In such an operation, the arms 534a, 543b, with the nets 536a, 536b in the storage position, are rotated about the axis A such that they are brought next to each other. Thereafter, the nets 536a, 536b are deployed, i.e. lowered to the bottom section 526, thus dividing the reservoir of water into a first, minor cylinder-section segment and a complementary second, major cylinder-section segment. Since the nets 536a, 536b are deployed next to each other, no fish will become entrapped in the first cylinder-sector segment and all fish will be located in the second cylinder-sector segment.

Thereafter, at least one of the arms 534a, 534b are rotated about the axis A, bringing the nets 536a, 536b to separate, thus causing the volume of the first cylinder-sector segment to increase and the volume of the second cylinder-sector segment to decrease correspondingly. Upon continued rotation of the arm(s) 534a, 534b about the axis A, fish will be driven or guided in front of the moving net(s) 536a, 536b, thus trapping the fish in the continuously shrinking second cylinder-sector segment. The rotation of the arm(s) is continued until the density of fish in the second cylinder-sector segment has become sufficiently large to allow efficient transfer of fish out of the second cylinder-sector segment. Such transfer may for example be effectuated by pumping.

In fish pen enclosures holding fish of different sizes, the mesh size of the nets 536a, 536b can be adopted to allow small fish to escape through the nets 536a, 536b, thus allowing only fish larger than a predetermined size to be singled out and rounded up in the second cylinder- section segment.

One or a plurality of planar roof sections 544, 546, e.g. made of netting and having a shape of a circular sector, may be arranged rotatably about the axis A to allow the roof section(s) to be positioned above the second cylinder-sector segment to prevent fish from leaping out from the second cylinder-section segment during a round-up operation.

Since the nets 536a, 536b are stored above the free surface, growth will not accumulate on the nets when they are not in use.

In the embodiment disclosed above, the fish pen apparatus 520 has two net equipped arms 534a, 534b. It is understood, however, that the fish pen apparatus may have more than two such arms, thus allowing the fish pen enclosure to be subdivided into more than two cylinder- section segments.

Fig. 4 shows another embodiment of a fish pen system 610 according to the invention. The fish pen system 610 comprises six fish pen enclosure 612 of the type previously disclosed. The fish pen system 610 also comprises an elongated gangway structure 614 along which the fish pen enclosures 612 are arranged. The fish pen system 610 further comprises an endless enclosure 616 forming an endless tunnel running in a closed loop along and on top of the gangway structure 614.

As in the previous embodiment, a water circulation system (not shown) is configured to circulate a body of water through the endless enclosure 616 at a controlled flow rate, and at least one fish station of a type previously discussed (not shown) is arranged in the endless enclosure 616 to interact with fish present in the body of water circulating through the endless enclosure.

The endless enclosure 616 runs along the gangway structure 614 such that it passes all six fish pen enclosures 612. Two transfer conduits 618a, 618b extend between each fish pen enclosure 612 and the endless enclosure 616 allowing fish to be transferred between the fish pen enclosure 612 and the endless enclosure 616 in the same way as has a previously been disclosed in relation to Figs. 1 and 2, i.e. using the above-discussed fish pen apparatus 500.

In the present embodiment the endless enclosure 616 serves all six fish pen enclosures 612 and, consequently, the fish station or stations (not show) in the endless enclosure 616 can be used to interact with fish transferred from any one of the six fish pen enclosures 612. Also, this configuration allows fish to be transferred in to the endless conduit 614 from one fish pen enclosure and subsequently transferred out to another, thus allowing to be transferred between different fish pen enclosures in the system.

The embodiment disclosed in Fig. 4 illustrates that one endless enclosure can serve a plurality of fish pen enclosures. Flowever, generally it is envisioned that any number of endless enclosures forming tunnels can serve any number of fish pen enclosures. Also, the embodiment disclosed in Fig. 4 illustrates that, within the concept of the invention, the shape of the endless enclosure is not restricted to any particular shape as long as it forms an endless tunnel.

Although the endless enclosures are positioned higher than the fish pen enclosures in the embodiments disclosed, it is to be understood that it is equally possible, within the concept of the invention, to position the endless enclosure at or even below the surface of the reservoir of water in the fish pen enclosure.

In the preceding description, various aspects of the invention have been described with reference to the illustrative embodiment. For purposes of explanation, specific numbers, systems and configurations were set forth in order to provide a thorough understanding of the apparatus and its workings. However, this description is not intended to be construed in a limiting sense. Various modifications and variations of the illustrative embodiments are possible within the scope of the invention as defined by the following claims.