GB2568501A

GB2568501A - Aquaculture system for cultivating aquatic organisms

Info

Publication number: GB2568501A
Application number: GB1719045.5A
Authority: GB
Inventors: Anders Brimsholm Bjøm; Haugland Eirik
Original assignee: Samba As
Current assignee: Samba As
Priority date: 2017-11-17
Filing date: 2017-11-17
Publication date: 2019-05-22
Also published as: GB201719045D0

Abstract

An aquaculture system for farming aquatic organisms comprising a cylindrical cage 1 with a longitudinal axel 20 arranged horizontally in water, and a floating structure 7 supporting the axel at both ends. The cage may be rotatable and in use, half of the cylinder surface may be exposed to air to make inspection, service and cleaning easier. The cylinder may comprise an internal rotating bulkhead 10 and/or a sensor frame 15 for measurement of biomass and size distribution of the fish. There may be an external waterproof cylindrical shell 3 which can be rotated so that the cage can be converted into a closed tank.

Description

Title: Aquaculture system for cultivating aquatic organisms

Field of invention

The present invention relates to an aquaculture system for cultivating aquatic organisms in water.

Background of the invention

A number of different marine installations are known and used for breeding of fish. Fish farming is a large and important industry in many countries and it is so both from an economic perspective as well as for the supply of healthy food to a growing world population. In the North Sea areas, the breeding of salmon is especially important.

The fish farms can be located in protected areas near the shore, at sea off the shores or in tanks on land. In the case of salmon farms in the sea, the activity is known to cause increase in the sea lice population which seriously affects the health and quality of the salmon. Furthermore, the growth in the sea lice population causes similar problems for the wild salmon and sea trout.

Another issue regarding fish farms at sea is breaking of the net cages normally used as a barrier. Holes may be caused by dogfish attacks or other external influences. Breakages or holes lead to escape of fish and subsequent mixing with wild salmon which is considered a serious threat to wild salmon stocks. Nets must be inspected, normally by divers or underwater vehicles and they have to be cleaned for marine algae on a regular basis. To minimise cleaning, the nets are normally impregnated with environmentally unfriendly substances.

Use of medicine, the feeding of fish as well as spill of faeces leak to the environment and constitute a biological load and contamination of the environment.

The most common fish farms at sea consist of cylindrical net cages with a floating member such as a float collar at the top, flexible sidewalls attached to the floating collar and a bottom attached to the sidewalls. The water volume is hence completely closed for fish if the net is 100% intact (depending on the size of the fish versus net mask size). Protection from above - i.e. birds - is often achieved with a net suspended over the fish cage.

Patent publication number W02015/099540 /1/ relates to a semi-submersible, cylindrical net cage including two closable fixed bulkheads and a sliding bulkhead extending in a radial direction from a central column to a circumference, the sliding bulkhead being rotatable about the central column. A bottom that can be elevated is provided between the two closable bulkheads. The cylinder axis is vertical.

Many patents and patent applications describe closed tanks either at sea or on land. Patent document NO160752/US4711199 /2/ describes tanks covered with a non-rigid material. They are lowered into the water and each tank has at least one inlet and one outlet for water. Patent document US4798168 /3/ describes a cylindrical tank made of non-rigid material with a conical bottom where water is supplied tangentially at the surface and exits from the centre of the cylinder. The cylinder axis is vertical.

Also submerged tanks made of rigid materials are known. Patent document NO166511/EP0347489 /4/ describes a semi submerged platform with cylindrical tanks with conical lower parts. Patent document NO165783/US4909186 /5/ describes a hull shaped container for fish. Patent document W02010/016769 /6/ shows a tank in a water proof and partly rigid material. Patent document W02010/099590 /7/ shows a system that employs an array of floating closed-containment tanks composed of panels made of waterproof fiberglass laminate materials and internal buoyant foambased materials.

Ocean Farming AS and Nordlaks Oppdrett AS are both developing systems for offshore based fish farming. Ocean Farming has a circular stiff steel construction anchored at 8 points around the circumference. The area crossing the sea surface has been made small so as to limit the wave forces on the construction. Nordlaks has a hull-shaped solution anchored at the bow so that the direction of the construction depends on wind, current and waves.

«Aquatraz» from Seafarming Systems AS is a concept based on a semi-closed tank in steel and built on ship-hull principles.

AkvaDesign AS is developing their closed tank for deployment in the sea. It consists of solid wall containment, depth-adjustable water intake, solids filtration and removal system and oxygen supply system.

Marine Harvest AS is developing their «Egget» which is an egg-shaped, rigid material closed tank for use in the sea. Sea water from 30 m depth is pumped into the tank which is completely closed and where the light conditions can be controlled.

Marine Harvest AS has also proposed the Beck-Cage - a horizontal cylindrical cage with butt ends, capable of being lowered entirely below the sea surface. The cage can be rotated about the horizontal axis such that the net can be exposed to air and dry if the cylinder is at the sea surface. It can also be lowered below the lice-zone using axially mounted flexible air chambers.

Circumferentially mounted flexible air chambers are used to rotate the cage. The concept is based upon the Beck Fish-Cage developed for use in the open ocean and described in patent DE 10 2008 057 515 /8/ and DE 10 2010 032 673 /9/.

Summary of the invention

The present invention thus relates to an aquaculture system for cultivating aquatic organisms in water, comprising a cylindrical cage with a longitudinal axle arranged substantially horizontal in said water, a floating structure wherein the longitudinal axle is suspended at both end portions by the floating structure.

In a preferred embodiment is the longitudinal axle rotatable suspended by the floating structure.

In a preferred embodiment comprises the system a shell arranged external to the cage.

In a preferred embodiment is the longitudinal axle near the water surface so that about half the cage is above water surface.

In a preferred embodiment is the cylindrical cage arranged to be rotated from 0 to 180 degrees in each direction.

In a preferred embodiment comprises the cage side wall and end walls made of water penetrable material, such as a net material.

In a preferred embodiment comprises the cage side wall and end walls made of water impenetrable material.

In a preferred embodiment are portions of the side wall and end walls are made of water impenetrable material, and portions of the side wall and end walls are made of water impenetrable material.

In a preferred embodiment is an internal bulkhead attached to the longitudinal axle along its entire length and with a width almost equal to the cylinder inner radius of the cage.

In a preferred embodiment is the bulkhead arranged to be rotated about the longitudinal axle.

In a preferred embodiment is the cylinder side wall composed by flat panels and where these panels can be removed.

In a preferred embodiment is at least one panel hinged and can be opened.

In a preferred embodiment will the rotation of the bulkhead in combination with an open panel section force the aquatic organisms into internal tubes connected to the cage and into the floating structure.

In a preferred embodiment is the external shell water impermeable.

In a preferred embodiment is said external shell covering 180 degrees or more of the cage and can be rotated to convert the cage to a closed cage.

In a preferred embodiment is said external shell arranged to serve as a collector of spills from the cage.

In a preferred embodiment is the external shell made of a flexible material, such as tarpaulin, arranged to be expanded during use and collapsed when not in use.

In a preferred embodiment comprises said system a sensor frame that can be rotated about the longitudinal axle.

In a preferred embodiment is the sensor frame supplied with acoustic transducers adapted to detect echo density, echo strength and transmission attenuation and use these parameters to calculate fish density, fish size distribution and biomass.

In a preferred embodiment is the sensor frame supplied with optical transducers to detect optical attenuation as a function of depth and use this parameter to estimate water turbidity.

In a preferred embodiment comprises the system inclinometers mounted on the cage wall used to detect angular orientation of the cage with respect to the water surface.

In a preferred embodiment are the inclinometer outputs used to control the orientation of the cylindrical cage (1) about the axis.

In a preferred embodiment are the inclinometers accelerometers with at least two axes oriented to extract orientation of the cylindrical cage.

In a preferred embodiment are the outputs from the accelerometer filtered with high-pass filter and low-pass filter so that it yields both orientation and vibration and shock.

In a preferred embodiment is the cage wall made of a net material, and the net material comprises sensors to detect net integrity.

In a preferred embodiment is the net material spun with electrically conductive or optically conductive fibres used to detect net integrity.

In a preferred embodiment is each panel monitored separately for net integrity.

In a preferred embodiment leads breakage of the net to an automatic rotation of the cylinder.

Detailed description of the invention

In the following description, the numbers in parenthesis refer to reference numbers in the figures.

Figure 1 3D overview.

Figure 2 Cross section showing 2 cylinders, floating structure and a live-haul vessel. Includes cross sections with bulkhead, sensor frame and external shell.

Figure 3 One cylinder configured as a closed tank and during operation of the rotational bulkhead. Illustrates how the fish enclosure is controlled by rotation of the bulkhead. The top drawing includes the channel inside the floating structure.

Figure 4 Details of the sensor frame and the rotational bulkhead along with acoustic transducers and bulkhead actuator.

Figure 5 Details of the mechanism for rotation of the cylinder and the bulkhead.

Figure 6 Details of the mechanism for rotation of the shell.

Figure 7 Instrumentation block diagram.

Reference numbers and components:

1. Cylinder/cage

2. Cylinder/cage side wall

3. Panel

4. Hinged panel

5. Cylinder/cage end walls

6. Internal tube/channel

7. Floating structure

8. Rotation control and locking mechanism

9. Hinged panel section

10. Bulkhead partition

11. Bulkhead partition actuator

12. External shell. A: 180 degrees, B: 90 degrees.

13. External shell rotation control and locking mechanism

14. Inclinometer

15. Sensor frame

16. Transmit/receive acoustic transducers

17. Receive transducers

18. Cylinder instrumentation

19. Live-hauling boat

20. Cylinder/cage axis

21. Net integrity sensor

The key properties of the invention are;

a) The risk of escaping fish is reduced to a minimum,

b) It is an environmentally friendly solution,

c) Operation and maintenance of the fish farm is cost effective and safe.

The present invention comprises a cage (1) formed as a horizontal cylinder with side wall (2) and end walls (5) consisting of nets and where some of or part of the walls may consist of materials that water cannot penetrate - rigid materials or non-rigid materials. The term cylinder is used interchangeably with the term cage. The sidewalls may be split in plane sections (panels) (3) covering for example 30 degree sectors - i.e. 12 panels of the same size. The cylinder axis is horizontal or near horizontal and the entire cylinder can be rotated an angle a in a controlled way about the cylinder axis. With the axis at the water surface, any part of the walls can be above or below water depending on the angle of the before mentioned angular rotation. The walls can therefore be dried or washed, which means that there is no need for impregnation. It is environmentally friendly while net cleaning and maintenance can be carried out effectively and where environmentally unfriendly substances need not be used.

The cages (1) are via a longitudinal axle (20) mounted to a floating structure (7) that serves as structural elements and as walkways for personnel.

The rotational angle a may be +/-180 degrees so that the use of slip-rings for electrical power or signals is not required.

External to the cylinder (1), there may be a partial cylinder (12) made of a waterproof rigid shell or tarpaulin shell, so that it constitutes a 180-degree sector. The external shell may be rotated so that the submerged part of the cylinder becomes a closed tank. This is especially convenient during feeding so that food spills can be collected and used for example in a bioreactor. If the closed tank approach is not required, the partial cylinder can constitute a smaller sector than 180 degrees, for example 90 degrees, and it will still collect food spills, but without hindering water exchange.

In an alternative configuration, the external shell may be split in several sections that can be connected so they together cover larger angular sections. Sections may be made by tarpaulin and be collapsed or expanded in the circumferential direction so that they take up minimum space when not in operation.

Hinged sections (4) of the sidewalls will allow for access to the cage for use during loading of fish to live-hauling boats.

In case a more rounded shape is convenient, for example to encourage a particular swimming pattern, the above-mentioned design could be modified to a cigar shaped enclosure - i.e. with rounded ends.

Rotational control of the net cylinder (1) may be via gears at the end of the cylinder axis with a hydraulic motor (13). In severe weather conditions, the cylinder may be locked to the frame using a locking device. The net cylinder (1) is symmetric, so the net rotational static moment about the cylinder axis is zero. The dynamic movement during rotation depends on the speed of rotation and the friction. Wind, current and waves will contribute to the moment, but this may be minimized by orienting the cylinder axis in the same direction as prevailing currents and/or winds.

Rotational control of the shell (12) may be via gears at the circumference (13). In severe weather conditions, the shell (12) may be locked to the frame using a locking device. The control of the shell will be designed to handle the maximum moment generated by the partial cylinder in its most inconvenient position.

During normal operation of the cylinder, the external shell is in a side position that does not obstruct water flow and hence supply of oxygen. If the partial cylinder covers 180 degrees and the system operates as a closed tank, external supply of oxygen is required. This can be achieved via nozzles integrated in the shell structure (12).

Feeding of fish will be solved with a commercially available feeder mounted inside the cylinder.

The invention also includes a rotational bulkhead partition (10). The bulkhead can be rotated from one side to force the fish to stay in a confined volume enclosed by the cylinder walls, the sea surface and the bulkhead. In combination with channels or internal tubes in the floating structure (7), this will force the fish into specially designed live-hauling boats, lice-removal-tanks etc.

The above-mentioned panels design (3) is advantageous with respect to servicing and repair. If the net is damaged, the entire panel may be replaced. If access to the cylinder is required, some panels can be hinged (4) and opened.

A preferred embodiment of the present invention includes a sensor and control system to control the rotational position of the cylinder.

Rotational position may be detected with inclinometers (14), for example as 3 axis accelerometers working in DC-coupled mode. The accelerometer may serve as shock and/or vibration detectors able to detect ship collisions, predator attacks etc. and also to detect the rotational position of the cylinder. Shocks can be detected by high pass filtering of the signals and rotational position can be detected by low pass filtering of the same signals followed by trigonometric evaluation of the two acceleration components perpendicular to the cylinder axis. Several sensors may be used along the cross-sectional circumference so that at least one is always above water, wireless signal transmission may thus be used, for example Bluetooth 5.0 in a meshed configuration.

Communication over electrical cables may also be used. Power may be battery based or cable based. Use of batteries will yield a cost effective and easy-to-service system.

Environmental sensors for measurement of current, temperature and oxygen are preferably used either inside the cylinder, outside the cylinder or both.

A sensor frame (16) may be included, attached to the cylinder axis so that it can be rotated. The sensor frame may include acoustic transducers, and optical sensors may also be attached and used to monitor optical attenuation for the estimation of algae in the water. As the sensor frame can be rotated, attenuation and thus the turbidity can be measured as a function of water depth.

Transmit and receive transducers constitute two systems for estimation of biomass. Transmit/receive transducers (16) can be used to measure pulse-echo statistics for size and biomass estimation and receive transducers (17) can be used to measure the amount of acoustic absorption for biomass estimation when transducers (16) transmit.

Acoustic target strength, hence the return pulse amplitudes, depends on the size of the fish bladder which is related to its length. In addition, there is a weak dependency of frequency /10/:

TS = 19.1 loglO L - 0.9 loglO F - 62.0 which is for the dorsal aspect. At side aspect, the values are between 1 and 8 dB higher, depending on frequency. TS is the Target Strength in dB, L is length in cm and f is the acoustic frequency in kHz. The formula is valid for fish with swim bladders where 0.7 < L/λ < 90, where λ is the wavelength in cm. For a frequency of 100 kHz, this corresponds to L between 1 cm and 135 cm. Several pulse-echo sequences in a well-defined cross section of the cage will yield statistics on the size distribution of the fish. A well-defined cross-sectional sector can be established with a sensor frame (15) that can be rotated to a defined position.

By using transmit transducers (projectors) (16) on one side of the frame (15) and receivers (17) on the opposite side, the attenuation due to the fish can be measured. From Newall et. al. /11/ we learn that —ASPL /dB\ ttfish. ~ 4.34 (JextinctN ( )

Where ASPL is the change in the received sound pressure level, x is the average distance in m, N is the fish number density N per meter cubed and σ is the extinction cross section due to both scattering and absorption. Newall et.al. propose to use the size of the fish as the extinction cross section if the source is far off resonance. The system can thus be used to determine fish density from the pulse-echo method (echo count) and fish size from the pulse-echo method (amplitude representing the air bladder) and the tomography method (attenuation).

The cylinder can be rotated so that the net can easily be inspected for holes and thereby reduce the probability for fish escape. Inspection can be carried out at regular intervals as part of a maintenance and inspection regime. Alternatively, a sensor (21) can be used to detect holes in the net and generate an alarm that leads to a rotation - either automatically or manually as a result of an alarm notification to personnel or a computer system. The submerged part will then be exposed and can be inspected and repaired. The sensor (21) can consist of electrical wires or optical fibres spun into the net and connected to suitable electronics. The sensor (21) will then be a simple break/no break detection as a broken optical fibre will not transmit light and a broken electrical wire will change conductivity abruptly. The cylinder will be rotated when a breakage is detected and the entire surface can be inspected visually and any holes repaired. The sensor wire will be repaired at the same time. It is therefore not necessary to know the exact location of the hole, unlike a conventional cage where the net is submerged at all times - requiring the exact location of the hole in order to be able to carry out repair which in turn makes the sensor system as well as the repair process very complex and expensive.

In the case of a panel (3) based design, each panel can be equipped with a net integrity sensor (21) and the panels can be individually connected to a cylinder data acquisition node that transmits data to the overall control system, either wireless (for example Bluetooth 5.0) or via cables. If wireless communication is used, there should be several wireless transmitters, preferably 3, in order to ensure that one antenna is above water at all times. The panel-to-cylinder-node cables should be equipped with underwater connectors with contacts for serial digital communication for example RS232, RS485 or I2C.

Each cylinder may be equipped with sensors for structural monitoring in addition to the net integrity sensors. Typical sensors would be strain gauge sensors for measurement of structural forces and torque in critical locations.

The cylinder data acquisition node may furthermore include these sensors:

Panel presence sensor,

Inclinometer,

Temperature sensor,

Oxygen sensor,

Fish density, size and biomass sensors,

Vibration and shock sensor,

Sensor for the status of rotational lock,

Structural monitoring sensors.

This way, each cylinder has its data acquisition system and covers all panels, which now become «smart panels» (18). The data acquisition system may be connected to the Internet Cloud in an loT (Internet of Things) scheme.

The cylinder may have any size, but is preferable from 20 to 60 m long and with a diameter of 30 to 70 m.

Preferred embodiment

A presently preferred embodiment is shown on figure 1, with 6 cylinders/cages, each 30 m long and 55 m diameter. The cylinder surface is composed of 12 x 6 panels, each covering an angular section of 30 degrees and 5 m length. At least one panel is hinged. The panels contain nets that include electrical wires for net integrity monitoring and the net size is such that one broken thread is too small for a fish to escape, hence it is single fault tolerant.

External to the net cylinder is the external shell made of tarpaulin and which covers 180 degrees so that the underwater compartment can be completely closed. The underwater compartment contains supply of oxygen by nozzles integrated in the external shell.

The floating platform that surrounds the cylinders serves as walkways and is wide enough for a forklift to operate.

Each underwater compartment contains sensors as shown in figure 9. The acoustic sensor system for biomass, fish density and fish size estimation, have piezoelectric transducers and operates at 100 kHz.

Power to the cylinder sensor nodes are battery based and data transmission is wireless Bluetooth 5.0 in a mesh configuration and the central data system is connected to the Internet and remotely accessible.

In normal operation, the cylinders are not clamped and on receipt of a net integrity alarm, rotation 180 degrees will be done in 2 minutes and an alarm will be sent via Internet and via SMS to operating personnel.

References

1. WO 2015/099540 Al. A submersible, cylindrical net cage, closable bulkheads for a net cage and a bottom for the net cage that can be elevated. Hammersnes, T.K. and Hammersnes, A.K.

2. US 4711199 (A). Device for breeding fish and shellfish. Nyman, Lars-Erik.

3. US 4798168. Arrangement for farming of fish, shellfish and other marine beings. Vadseth, R., Vadseth, A.

4. NO 166511/EP 0347489. Offshore fishfarm for breeding and keeping of fishes and suchlike aquatic animals. Langlie, C.

5. NO 165783/US 4909186. Fish cage for cultivating fish. Nakamune Hideo, Hirose Haruki.

6. WO 2010/015769. Fishfarming pen. H0ie, J.

7. WO 2010/099590. Solid wall closed containment aquaculture system. Buchanan, R., White, T.

8. DE 10 2008 057 515. System, Technologie, Function und Verfaren von mobile und versenkbaren Fischkafigen fOr das offene Meer. Beck, S.

9. DE 10 2010 032 673. System, Technologie, Function und Verfaren von mobile und versenkbaren

Fischkafigen fOr das offene Meer. Beck, S.

10. Urick, R.J. Principles of Underwater Sound. 3rd edition, Peninsula Publishing, 1983. pp. 316-317.

11. Newhall, E., Lin, Y-T, Grothues, T.M., Lynch, J.F., Gawarkiewicz, G.G. A method of observing acoustic scattering and absorption by fish schools using autonomous underwater vehicles. IEEE

Jornal of Oceanic Engineering, Vol. 42, Issue 1, 2017.

Claims

1. Aquaculture system for cultivating aquatic organisms in water, comprising a cylindrical cage (1) with a longitudinal axle (20) arranged substantially horizontal in said water, a floating structure (7) wherein the longitudinal axle (20) is suspended at both end portions by the floating structure (7).

2. Aquaculture system according to claim 1, wherein the longitudinal axle (20) is rotatable suspended by the floating structure (7).

3. Aquaculture system according to claiml, wherein the system comprises a shell (12) arranged external to the cage (1).

4. Aquaculture system according to claim 1, characterized in that the longitudinal axle (20) is near the water surface so that about half the cage (1) is above water surface.

5. Aquaculture system according to claim 2, characterized in that the cylindrical cage (1) is arranged to be rotated from 0 to 180 degrees in each direction.

6. Aquaculture system according to claim 1, wherein the cage (1) comprises side wall (2) and end walls (5) made of water penetrable material, such as a net material.

7. Aquaculture system according to claim 1, wherein the cage (1) comprises side wall (2) and end walls (5) made of water impenetrable material.

8. Aquaculture system according to claim 6 and 7, wherein portions of the side wall (2) and end walls (5) are made of water impenetrable material, and portions of the side wall (2) and end walls (5) are made of water impenetrable material.

9. Aquaculture system according to claim 1, characterized in that an internal bulkhead (10) is attached to the longitudinal axle (20) along its entire length and with a width almost equal to the cylinder inner radius of the cage (1).

10. Aquaculture system according to claim 8, wherein the bulkhead (10) is arranged to be rotated about the longitudinal axle (20).

11. Aquaculture system according to claim 1, characterized in that the cylinder side wall (2) is composed by flat panels (3) and where these panels (3) can be removed.

12. Aquaculture system according to claim 7, characterized in that at least one panel (3) is hinged and can be opened (9).

13. Aquaculture system according to claim 6 and 7, characterized in that the rotation of the bulkhead (10) in combination with an open panel section (3) will force the aquatic organisms into internal tubes (6) connected to the cage (1) and into the floating structure (7).

14. Aquaculture system according to claim 1, wherein the external shell (12) is water impermeable.

15. Aquaculture system according to claim 14, characterized in that said external shell (12) is covering 180 degrees or more of the cage (1) and can be rotated to convert the cage (1) to a closed cage (1).

16. Aquaculture system according to claim 14, characterized in that said external shell (12) is arranged to serve as a collector of spills from the cage (1).

17. Aquaculture system according to claim 3, characterized in that at said external shell (12) is made of a flexible material, such as tarpaulin, arranged to be expanded during use and collapsed when not in use.

18. Aquaculture system according to claim 1, characterized in that said system comprises a sensor frame (15) that can be rotated about the longitudinal axle (20).

19. Aquaculture system according to claim 18, wherein the sensor frame (15) is supplied with acoustic transducers adapted to detect echo density, echo strength and transmission attenuation and use these parameters to calculate fish density, fish size distribution and biomass.

20. Aquaculture system according to claim 18, wherein the sensor frame (15) is supplied with optical transducers to detect optical attenuation as a function of depth and use this parameter to estimate water turbidity.

21. Aquaculture system according to claim 1, characterized in that the system comprises inclinometers (14) mounted on the cage (1) wall (2) used to detect angular orientation of the cage (1) with respect to the water surface.

22. Aquaculture system according to claim 21, characterized in that the inclinometer (14) outputs are used to control the orientation of the cylindrical cage (1) about the axis.

23. Aquaculture system according to claims 21 or 22, characterized in that the inclinometers (14) are accelerometers with at least two axes oriented to extract orientation of the cylindrical cage (1).

24. Aquaculture system according to claim 15, characterized in that the outputs from the accelerometer are filtered with high-pass filter and low-pass filter so that it yields both orientation and vibration and shock.

25. Aquaculture system according to claim 1, characterized in that the cage wall (2) is made of a net material, and the net material comprises sensors (21) to detect net integrity.

26. Aquaculture system according to claim25, wherein the net material is spun with electrically conductive or optically conductive fibres used to detect net integrity.

27. Aquaculture system according to claims 11 and 26, characterized in that each panel (3) is monitored separately for net integrity.

28. Aquaculture system according to claims 11 and 26, characterized in that breakage of the net leads to an automatic rotation of the cylinder.