NO348035B1

NO348035B1 - A system for supplying and extracting water from a closed or semi-closed cage for fish farming

Info

Publication number: NO348035B1
Application number: NO20221265A
Authority: NO
Inventors: Frank Øren
Original assignee: Smir As
Priority date: 2022-11-24
Filing date: 2022-11-24
Publication date: 2024-07-01
Also published as: NO20221265A1

Description

A system for supplying and extracting water from a closed or semi-closed cage for fish farming

Field of the invention

The present invention relates to a system for supplying and extracting water from a closed or semi-closed or semi-closed cage for fish farming.

Background of the invention

Closed cages in fish farming utilizing rotational motion to ensure exchange of fresh water through the cage is known. Closed cages comprise impermeable walls and bottoms and the closed cages is continuously supplied with water by pumping from the surroundings of the cage or from a depth below the cage, pumping water requires a high amount of energy. The closed cage typically has an opening in the bottom or in the wall for outlet of water. The increased water column presses water out through the opening in the bottom of the cage. In order to ensure a rotational motion of the water masses in the closed cages, the water is supplied tangential along the wall of the cage. The energy consumption puts a limitation to the amount of water that can be pumped into the cage. The more water that is pumped into the cage, the more energy is required to pump.

NO175341 describes a method for supply of water to a closed fish cage, wherein the water is pumped through a supply pipe from the deep by means of a pump. The water is entering the fish cage in a horizontal tangential direction to initiate a rotational motion of the masses of water. The water level is regulated by regulating the rotational speed of the water, for example by splitting the incoming water in one or more directions. The water is led through the fish cage towards an outlet in a bottom portion of the fish cage.

Thus, there is a need for a system to overcome these problems mentioned above.

Additional related prior art:

CN111066715A discloses a circulating water aquaculture system adopting vortex type sewage collection.

NO20171340A1 relates to a breeding facility comprising a fish tank, an outlet pot arranged in a bottom of the fish tank, where the outlet pot has a recess which forms a fluid channel and a outlet arranged at a downstream end of the fluid channel.

NO20211497A1 relates to a fish farm for fish farming including a closed unit attached to a floating collar through an immersion adjustment system for locating the closed unit below the water surface and in the water column. The invention also relates to supply and discharge of water to/from the closed unit.

WO2021225450A1 relates to an outlet basin for a closed or semi-closed aquaculture pen where the main water outlet is separate from the system for collection of sludge and from the system for handling of dead fish

Summary of the invention

A main object of the present invention is to provide efficient water exchange in a cage for fish farming.

Another object of the present invention is to reduce the energy consumption needed for water exchange.

A further object of the present invention is to provide efficient removal of sludge and/or faeces.

Yet another object of the present invention is to provide control of the speed of the water entering the cage.

Another object of the present invention is to provide control of the direction of the water entering the cage.

Another object of the present invention is to provide efficient emptying of a closed or semi-closed cage from biomasses.

A further object of the present invention is to provide a controllable water quality.

Another object of the present invention is to avoid or at least limit lice in the cage.

Yet another object of the present invention is to provide a double redundancy of the water exchange in the cage.

According to an aspect of the invention, there is provided a system for supplying and extracting water from a closed or semi-closed cage for fish farming, the system comprising

− a closed or semi-closed cage connected to a floating body/collar, wherein the closed or semi-closed cage comprises a wall and a bottom forming a reservoir for containing water and biomasses, wherein the bottom comprises a centrally arranged opening and wherein the wall and the bottom are made of an impermeable material,

− an inlet for water arranged in the wall at or below a water level inside the closed or semi-closed cage

− at least one supply pipe for supplying water into the reservoir wherein the at least one supply pipe is connected to the inlet for water,

− a net or grid arranged in the opening configured to prevent biomasses from but allowing faces or other unwanted organic elements to escape from the closed or semi-closed cage

− a propeller arranged downstream the net or grid for rotation of the water and extracting/drawing water out of the reservoir

− wherein the at least one supply pipe comprises a supply pipe inlet immersed in water, ensuring a fluid connection between the water surrounding the closed or semi-closed cage and the water in the closed or semi-closed cage.

In embodiments, the water supplied through the inlet for water into the closed or semi-closed cage is directed in a direction ensuring a rotation of the water masses in the direction of revolution of the propeller.

In embodiments, the inlet of the supply pipe is arranged at a water depth at least at the dept of the propeller or deeper.

In embodiments, the inlet of the supply pipe is arranged at a water depth free from lice.

In embodiments, an outlet portion is arranged projecting down from the centrally arranged opening, enclosing the propeller.

In embodiments, the outlet portion is made of a permeable or impermeable material.

In embodiments, the supply pipe is telescopic for regulating the depth position of the inlet of the supply pipe.

In embodiments, the inlet comprises a guiding means for regulating the direction of the flow of water and/or for regulating the volume of incoming water.

In embodiments, the guiding means is valve disc or fins.

In embodiments, the cage comprises an upper bottom arranged inside the closed or semi-closed cage.

In embodiments, the outer circumference of the upper bottom has an outer diameter corresponding to the diameter of the wall of the closed or semi-closed cage.

In embodiments, the upper bottom is made of a permeable material.

In embodiments, the upper bottom is a net.

In embodiments, the upper bottom is made of an impermeable material having a centrally arranged area of a permeable material.

In embodiments, the upper bottom is arranged to be lifted or lowered within the closed or semi-closed cage, enabling lifting biomasses to a higher level of the cage for pumping into another cage, to a fish carrier, etc.

In embodiments, the upper bottom is anchored in a ring arranged at the outer circumference of the upper bottom.

In embodiments, the ring is filled with water.

In embodiments, the ring is anchored in a plurality of slits arranged in the wall.

In embodiments, wherein the plurality of slits are equally distributed around an axial axis of the wall.

In embodiments, the ring is suspended from a top portion of the closed or semiclosed cage, by means of one of ropes, wires, chains, etc.

In embodiments, the upper bottom is lifted or lowered by means of a winch.

In embodiments, the system comprises a control system for controlling the guiding means and revolutions per minute of the propeller.

In embodiments, the control system receives operational data from sensors arranged in the system.

In embodiments, the sensors are arranged in the inlet for water, in the opening at the bottom of the cage and/or at the walls of the cage.

The present invention relates to a system for supplying and extracting water from a closed or semi-closed cage. The cage comprises a water inlet arranged at or below the water level inside the closed or semi-closed cage and a water supply pipe, wherein the supply pipe is connected to the water inlet. The supply pipe having a pipe portion extending vertically or at least upwards inclining up from a depth of the sea water surrounding the cage and further bending to a horizontally extending pipe portion connecting to the water inlet of the closed or semi-closed cage. The water column in the supply pipe forms a continuous fluid connection with the water inside the closed or semi-closed cage. The water inlet comprises guiding means for guiding the incoming water in a desired direction.

A propeller is arranged below the opening or in the outlet portion at the bottom of the closed or semi-closed cage. The propeller draws water out of a water filled closed or semi-closed cage and lowers the water level inside the cage. The propeller creates a suction of water downwards the cage and out of an opening arranged at the bottom of the cage. The propeller thus initiating a continuous flow of water from a depth of the sea, through a water intake of the supply pipe, up through the supply pipe, out of the water inlet, into the cage and out of the opening at the bottom of the cage, ensuring a continuous exchange of water in the cage. The propeller ensures that the water is constantly being drawn out of the cage for a continuous flow of water through the cage, where water is constantly being supplied to and extracted from the closed or semi-closed cage. The propeller can increase and decrease the rate of pulling the water out of the cage by regulating the revolutions per minute, RPM, of the propeller. The propeller is driven by means of a motor or other suitable means for rotation. A constant supply and exchange of water in the closed or semi-closed cage is ensured.

An increased efficiency of the water exchange can be achieved by rotating the water masses in the cage. Rotating water masses has a downwards directed force pressing the water masses downwards and out of the opening of the cage. Rotating water masses can be achieved by directional control of the incoming water flowing from water inlets at a top portion of the cage. The direction and volume of the incoming water can be regulated by means of the guiding means regulating the direction and/or the volume of the water flowing out of the water inlets. The guiding means being a valve disc, fins or flaps etc. arranged in the water inlets and can be regulated to direct the flow of water from the walls of the cage to the center of the cage and/or by reducing or increasing the volume of the water entering the cage. For maximum rotational speed, the flow of water is directed along the walls of the cage at maximum volume of the water entering the cage.

The incoming water is configured to rotate the water masses in the same rotational direction as the propeller. The propeller requires energy to rotate. In a start-up phase, more energy is required than in an operational phase. As the water masses achieve a rotational motion, the propeller will almost be self-propelled, with only a little effort from a means for rotating the propeller. In an initiating start-up phase, when the reservoir is filled up with sea water, the propeller is used to initiate the elevation of sea water up through the supply pipe effect and thus having the water masses in the reservoir to rotate. When the masses of water have reached a required or desired rotational speed, the propeller can decrease its rotational speed and be driven/rotated by the rotating water masses. Further, rotating water masses are creating a downwards directed vortex, pressing water down towards the opening at the bottom and the cage and pressing onto the propeller to rotate. The required amount of energy to drive the propeller is thus reduced.. The rotational speed of the water masses is maintained, increased and decreased by regulating the direction and/or volume of incoming water to the cage together with regulation of the RPM of the propeller. The rotational speed should be regulated for living fish to maintain a certain level in the cage, but for faces or other unwanted organic elements to be drawn out of the cage.

The incoming water has a density corresponding to the density of the depth being elevated up from, the water transported and supplied into the cage will seek back and down to the depth having that density. This is further adding to a downward directed water current pressing on the propeller to rotate. Further decreasing energy consumption.

It is known that sea water from deeper water has better water quality with regards to e.g. temperature and salinity and below a certain depth there is no sea lice. The water intake of the supply pipes should preferably be below the depth of the propeller, and more preferably at a depth having the optimum water quality in regards to temperature, salinity, absence of sea lice etc. The supply pipes of the present invention are preferably telescopic to regulate to optimum sea depth.

In embodiments, the system comprises a filter in the inlet of water into the cage to filter out undesirable elements in the water.

In embodiments, additives can be added at the inlet of water to improve the water quality or to treat sick or infected fish.

The rotational speed, the amount of oxygen in the water, the RPM of the propeller etc. can be manually or automatically regulated. Automatically regulation is operated by means of a control system receiving operational data from sensors arranged at e.g. the inlet, the outlet, the walls of the cage, the center of the cage, etc. or manually regulated.

Different biomasses, ranging from e.g. smolt to large salmons, requires different operational conditions. For example, smolt is having a smaller total biomass, e.g.20 tons, and tolerates only lower speed than large salmon having larger total biomass, e.g. 500 tons, tolerating higher speeds.

In case of failure of the propeller, where the rotation of the propeller comes to a stop, the system comprises a back-up system ensuring water supply to the closed or semi-closed cage, Gas, e.g. pressurized air, forming gas bubbles at the water intake of the supply pipes, the bubbles expanding and ascending upwards providing an upwards motion or flow of the sea water, lifting the water up and into the cage maintaining the water exchange and rotation of the water mases in the cage.

Description of the figures

Embodiments of the present invention will now be described, by way of example only, with reference to the following figures, wherein:

Figure 1 shows schematically a cross sectional view of a system of prior art.

Figure 2 shows schematically a cross sectional view an embodiment of a system for supplying and extracting water from a closed or semi-closed cage fish for farming according to the present invention.

Figure 3 shows schematically a cross sectional view of another embodiment of a system 10 for supplying and extracting water from a closed or semi-closed cage for fish farming according to the present invention.

Figure 4 shows schematically a top view of the system for supplying and extracting water from a closed or semi-closed cage fish for fish farming according to the present invention.

Figure 5 and 6 shows schematically a cross sectional view of the system with the upper bottom lifted approximately up to the sea surface.

Figure 7 shows schematically an operation where the biomasses are being gathered and pumped or transported out of the cage into a fish carrier located outside the cage.

Description of preferred embodiments of the invention

The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to a system for supplying and extracting water from a closed or semi-closed cage of the system.

Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures, or characteristics may be combined in any suitable manner in one or more

embodiments.

Figure 1 shows schematically a cross sectional view of a closed or semi-closed cage 110 of prior art. The cage 110 is circular and consists of an upper approximately cylindrical wall 111 connected to a floating body 120 and a bottom 112. Sea water is pumped into the cage 110 from the deep through a supply pipe 130. The water is supplied in a horizontal tangential direction, so that the volume of water in the cage 100 is set in rotation. The level of water in the cage 100 is controlled by regulating the speed of the rotating motion of water, by dispersing the ingoing current of water in one or more direction by means of guiding means or the volume of the incoming water. The water is conducted out through an outlet portion 114 centrally arranged in the bottom for outlet of sea water and organic waste. A net or a grill is arranged at the outlet portion 114 preventing fish from escaping the cage and death fish from disappearing unintentionally. Further the net is connected to a hose through which organic waste such as dead fish, excrements, feed residues etc. are conducted to the surface my means of a pump.

Figure 2 shows schematically a cross sectional view an embodiment of a system 100 for supplying and extracting water from a closed or semi-closed cage for fish farming according to the present invention. The system 100 comprises a closed or semiclosed cage 110 comprising a wall 111 and a bottom 112 forming a reservoir 113 for sea water and biomasses such as fish. The closed or semi-closed cage 110 is connected to a floating body/collar 120 (not shown) at an upper portion of the wall 111. The wall 111 is cylindrically shaped, having a substantially semi-circular, semioval, square or rectangular circumference. The bottom 112 can be flat or the bottom is conically shaped, possibly as a frustrum pointing in a downward direction towards the sea surface. The bottom 112 comprises a centrally arranged opening 114 having an outlet portion 115 extending down from the opening 114. A propeller 140 for drawing water masses out of the cage 110 is arranged in the outlet portion 115. The opening 114 comprises a grid or a net 116, preventing large elements, such as fish, to come in contact with the propeller, allowing faces or other unwanted organic elements.

Figure 3 shows schematically a cross sectional view of another embodiment of a system 100 for supplying and extracting water from a closed or semi-closed cage for fish farming according to the present invention. The system 100 comprises a closed or semi-closed cage 110 comprising a wall 111 and a bottom 112 forming a reservoir 113 for sea water and biomasses such as fish. The cage 110 is connected to a floating body/collar 120 (not shown) at an upper portion of the wall 111. The wall 111 is cylindrically shaped, having a substantially semi-circular, semi-oval, square or rectangular circumference. The bottom 112 can be flat or the bottom 112 is conically shaped, possibly as a frustrum pointing in a downward direction towards the sea surface. The bottom 122 comprises a centrally arranged opening 114 having an outlet portion 115 extending down from the opening 114. A propeller 140 for drawing water masses out of the cage 110 is arranged in the outlet portion 115. The opening 114 comprises a grid or a net 116 preventing large elements, such as fish, to come in contact with the propeller, allowing faces or other unwanted organic elements.

In figure 2 and 3, at least one inlet opening 160 (not shown in figure 2) for water is arranged in the upper portion of the wall 111. The at least one inlet opening 160 for water is arranged to create a rotation or a maelstrom of the masses of water in the reservoir 113. The at least one inlet opening 160 is preferably arranged for the incoming water to enter the reservoir 113 along the walls 111 of the cage 110. The at least one inlet opening 160 preferably comprises guiding means (not shown) for regulating the direction and/or the volume of the water out of the inlet opening 160.

The propeller 140 of figure 2 and figure 3 is configured to rotate in the same direction as the rotation or maelstrom of the water masses in the reservoir 113 arising from the direction of the incoming water. The propeller 140 is rotating by a means for rotating (141) the propeller 140, e.g. a motor or other suitable means for rotating (not shown) The propeller needs energy to start up the rotation, as the water masses are in rotational motion, the propeller will almost be self-propelled, with little effort from a means for rotating the propeller 140. In an initiating start-up phase, when the reservoir 113 first has been filled up with sea water, the propeller 140 is creating a suction drawing water out of the reservoir but can also be used to help initiate the water masses in the reservoir 113 to rotate. When the masses of water have reached a required or desired rotational speed, the propeller 140 can reduce its rotational speed and more or less be driven/rotated by the rotating water masses, reducing the amount of energy requireed to drive the propeller 140. The rotation of the water masses is maintained by regulating the direction and/or volume of incoming water to the cage 110 possibly together with a rotation of the propeller 140 by means of the motor or means for rotation.

Further for figure 2 and figure 3, the incoming water is elevated up from the deep through inlets of supply pipes 130 (not shown in figure 2), each supply pipe 130 extends vertically or at least upwards inclining from a water depth and connects to an inlet for water 160, wherein the inlet for water at or below the water level inside the cage. The vertical or at least upwards inclining part of the supply pipe 130 is preferably a telescopic, adjustable to extend or shorten the length of the supply pipe 130 to different sea depths. Wherein the depth is at least the depth of the propeller or deeper. The incoming water has a density corresponding to the density of the depth it is elevated up from, and when transported a higher depth (closer to the sea surface), the water will seek back and down to the depth having that density. This will cause a water current downwards, pressing on the propeller 140 to rotate, further decreasing the energy requirement to drive the propeller 140. The rotating water masses, together with faeces and other unwanted material are having a downward directed and vertical motion pressing, the water masses, faeces and other unwanted material down and out of the opening 114 and preferably the outlet portion 115. The faeces and other unwanted material are preferably deposit down into a tank or reservoir 170 arranged below the opening 114 or the outlet portion 115, the water masses is released out into the sea. The tank or reservoir 170 is preferably suspended down from the opening 114 or outlet portion 115, preferably by suspensions means 180, such as ropes, wires, chains or the like 180. The system 100 preferably comprises an upper bottom 150, arranged inside the closed or semiclosed cage 110 above the bottom 112 of the closed or semi-closed cage 110. The upper bottom 150 is arranged to be lifted or lowered within the closed or semi-closed cage 110. Figure 2 shows the upper bottom 150 in the lowest position, when the cage is in normal operating state, the upper bottom 150 seen as a more or less an offset shape of the bottom 112. The upper bottom 150 is made of an impermeable material with a centrally arranged perforated area/area of permeable material allowing water masses, faeces or other unwanted material to pass through to the opening 114 of the bottom of the 112 of the closed or semi-closed cage 110 but keeping the biomasses in the reservoir 113. Alternatively, the upper bottom 150 is made of a permeable material allowing water masses, faeces or other unwanted material to pass through, but keeping the biomasses in the reservoir 113. The upper bottom 150 is anchored in a ring 151 and can be lifted up towards and above the sea surface by means of a winch or other suitable means for lifting the upper bottom 150.

At least one inlet opening 160 (not shown in figure 2) for water is arranged in the upper portion of the wall 111. The at least one inlet opening 160 for water 160 is arranged to create a rotation or a maelstrom of the masses of water in the reservoir113, preferably the at least one inlet opening 160 is arranged for the incoming water to enter the reservoir 113 along the walls 111 of the cage 110. The at least one inlet opening 160 preferably comprises guiding means (not shown) for regulating the direction and/or the volume of the water out of the inlet opening 160.

Further for figure 2 and 3, the system 100 comprises an upper bottom 150, arranged inside the closed or semi-closed cage 110 above the bottom 112 of the closed or semi-closed cage 110. The upper bottom 150 is arranged to be lifted or lowered within the closed or semi-closed cage 110. Figure 2 and figure 3 shows the upper bottom 150 in the lowest position, when the cage is in normal operating state, the upper bottom 150 seen as a more or less an offset shape of the bottom 112. The upper bottom 150 is made of an impermeable material with a centrally arranged perforated area/area of permeable material allowing water masses, faeces or other unwanted material to pass through to the opening 114 of the bottom of the 112 of the closed or semi-closed cage 110 but keeping the biomasses in the reservoir 113. Alternatively, the upper bottom 150 is made of a permeable material allowing water masses, faeces or other unwanted material to pass through, but keeping the biomasses in the reservoir 113. The upper bottom 150 is anchored in a ring 151 and can be lifted up towards and above the sea surface by means of a winch or other suitable means for lifting the upper bottom 150.

A collector pipe 200 (see figure 2) for collecting dead or living fish can be immersed into the cage 110 along the wall 111 and bottom 112 of the cage. The pipe 200 is preferably telescopic and thus extendable. The dead or living fish can be pumped up above the sea surface through the collector pipe 200 and received by a fish carrier or other suitable operating vessels.

In figure 3, two supply pipes 130 for supplying deep water is shown entering the closed or semi-closed cage 110. The vertical supply pipes 131 is shown to be telescopic and adjustable to extend or shorten the length of the vertical inlet supply 131 to different sea depths.

Figure 3 further shows a net 190 suspended from and arranged below the closed or semi-closed cage 110. The net 190 is suspended by means of ropes, wires, chains or the like. Faeces and other unwanted material are preferably deposit down into the net 190. The net 190 can be replaced by a tank or reservoir 170 as described above of figure 2.

Figure 4 shows schematically a top view of the system 100 for supplying and extracting water from a closed or semi-closed cage fish for fish farming according to the present invention. One possible embodiment of the horizontal supply pipes 132 is shown, wherein the horizontal supply pipes 132 is arranged for the inlet to be substantially tangentially to the circumference of an inner surface of the wall 111 of the cage 110. The incoming water arriving the closed or semi-closed cage 110 along the walls 111 of the cage. Figure 4 shows four inlets for water 160 and four corresponding horizontal supply pipes 132, each horizontal supply pipe 132 is connected to an inlet 160 for water into the reservoir 113. The system 100 is not limited to four inlets for water 160 with corresponding four horizontal supply pipes 132, it can be one, two, three or more. The propeller 140 is shown centrally arranged. The incoming water and the propeller are shown having an equal rotational direction, in figure 4 shown counter-clockwise. The inlet 160 and the horizontal supply pipes 132 may be arranged in an opposite direction providing a clockwise rotational direction of the incoming water and thus the propeller is configured to rotate in the same clockwise rotational direction.

Figure 5 and 6 shows schematically a cross sectional view of the cage 110 with the upper bottom 150 lifted approximately up to the sea surface. For simplicity is features shown in figure 3 and 4 not shown. The upper bottom 150 is typically lifted for emptying the system 100 from biomasses. The biomasses are gradually lifted upwards and eventually forced and gathered into a smaller area/volume and ready to be pumped or transported out of the cage.

Figure 7 shows schematically an operation where the biomasses are being gathered and pumped or transported out of the cage into a fish carrier 300 located outside the cage 100. An operating vessel 400 also located outside the cage 100 assists the operation.

Table 1

Claims

1. A system (100) for supplying and extracting water from a closed or semiclosed cage (110) for fish farming, the system comprising

− a closed or semi-closed cage (110) connected to a floating body/collar, wherein the closed or semi-closed cage (110) comprises a wall (111) and a bottom (112) forming a reservoir (113) for containing water and biomasses, wherein the bottom comprises a centrally arranged opening (114) and wherein the wall (111) and the bottom (112) are made of an impermeable material,

− an inlet for water (160) arranged in the wall (111) at or below a water level inside the closed or semi-closed cage (110), for supplying water into the closed or semi-closed cage (110),

− at least one supply pipe (130) for supplying water into the reservoir (113) wherein the at least one supply pipe (130) is connected to the inlet for water (160),

− a net or grid (116) arranged in the opening (114) configured to prevent biomasses from but allowing faces or other unwanted organic elements to escape from the closed or semi-closed cage (110),

− a propeller (140) arranged downstream the net or grid (116) for rotation of the water and extracting/drawing water out of the reservoir (113),

− wherein the at least one supply pipe (130) comprises a supply pipe inlet (131) immersed in water, ensuring a fluid connection between the water surrounding the closed or semi-closed cage and the water in the closed or semi-closed cage (110).

2. The system (100) according to claim 1, wherein the water supplied through the inlet for water (160) into the closed or semi-closed cage (110) is directed in a direction ensuring a rotation of the water masses in the direction of revolution of the propeller (140).

3. The system (100) according to claim 1 or 2, wherein the inlet (131) of the supply pipe (130) is arranged at a water depth at least at the dept of the propeller (140) or deeper.

4. The system (100) according to claim 1 or 2, wherein the inlet (131) of the supply pipe (130) is arranged at a water depth free from lice.

5. The system (100) according to any of the preceding claims, wherein an outlet portion (115) is arranged projecting down from the centrally arranged opening (114), enclosing the propeller (140).

6. The system (100) according to claim 5, wherein the outlet portion (115) is made of a permeable or impermeable material.

7. The system (100) according to any preceding claims, wherein the supply pipe (130) is telescopic for regulating the depth of the inlet (131) of the supply pipe (130).

8. The system according to any preceding claims, wherein the inlet (160) comprises a guiding means for regulating the direction of the flow of water and/or for regulating the volume of incoming water.

9. The system according to claim 8, wherein the guiding means is valve disc or fins.

10. The system according to any preceding claims, wherein the cage (110) comprises an upper bottom (150) arranged inside the closed or semi-closed or semiclosed cage (110).

11. The system according to claim 10, wherein the outer circumference of the upper bottom (150) has an outer diameter corresponding to the diameter of the wall (111) of the closed or semi-closed cage (110).

12. The system according to claims 10 or 11, wherein the upper bottom (150) is made of a permeable material.

13. The system according to claims 10 or 11, wherein the upper bottom (150) is a net.

14 The system according to claims 10 or 11, wherein the upper bottom (150) is made of an impermeable material having a centrally arranged area of a permeable material.

15. The system according to one of the claims 10-14, wherein the upper bottom (150) is arranged to be lifted or lowered within the closed or semi-closed cage (110) enabling lifting biomasses to a higher level of the cage for pumping into another cage, to a fish carrier, etc.

16. The system according to one of the claims 10-15, wherein the upper bottom (150) is anchored to a ring (151) arranged to the outer circumference of the upper bottom (150).

17. The system according to claim 16, wherein the ring (151) is filled with water.

18. The system according to claim 16 or 17, wherein the ring (151) is anchored in a plurality of slits arranged in the wall (111) equally distributed around the axial axis of the wall (111).

19. The system according to claim 18, wherein the slits extend along the whole height of the wall (111).

20. The system according to one of the claims 16-19, wherein the ring (151) is suspended from a top portion of the closed or semi-closed cage (110) by means of one of ropes, wires, chains, etc.

21. The system according to one of the claims 10-20, wherein the upper bottom (150) is lifted or lowered by means of a winch.

22. The system according to any preceding claim, wherein the system (100) comprises a control system for controlling the guiding means and revolutions per minute of the propeller (140).

23. The system according to claim 22, wherein the control system receives operational data from sensors arranged in the system.

24. The system according to claim 23, wherein the sensors are arranged in the inlet for water (160), in the opening (114) at the bottom (112) of the cage (110) and/or at the walls (111) of the cage (110).