A crowding net cage assembly, a fish farm with a net cage assembly and a method of crowding fish

Abstract

The net cage assembly comprises a stationary net wall (8, fig 3) and a movable, vertical crowding net wall (5, fig 2). A crowding net cage 2 is located between the stationary vertical removable net wa

Description

Technical Field [0001 ] The present invention relates to a crowding net cage for a semisubmersible fish farm, a semi-submersible fish farm with a crowding net cage and a method of crowding fish in a semi-submersible fish farm with a crowding net cage.

[0002] When crowding fish, in particular offshore, it is a problem if the crowding takes place close to the sea surface as waves and the overall motion of the sea will severely affect both the fish and the crowding structures. The fish may both be harmed against the mechanical structures and may be seasick, thus reducing fish welfare overall. Background Art

[0003] A method of crowding fish in a semi-submersible fish farm is shown in EP3086635B1. Two closable fixed bulkheads and a sliding bulkhead extends in a radial direction from a central column to a circumference. The sliding bulkhead is rotatable about the central column. A bottom that can be elevated is provided between the two closable fixed bulkheads. Summary of invention

[0004] According to a first aspect of the present invention, it is provided a crowding net cage assembly for a fish farm with a fish residence volume, a stationary vertical removable net wall at a net wall location and a movable, vertical crowding net wall. A crowding net cage includes a top wall, side walls and end walls. The crowding net cage is movable vertically between a position above the fish residence volume and a position below a sea surface at a depth substantially unaffected by waves. The crowding net cage is located between the stationary vertical removable net wall at the net wall location, and the movable, vertical crowding net wall. A horizontal closing element is adapted to selectively close a bottom the crowding net cage. A movable, vertical crowding net cage bulkhead is located in an inside of the crowding net cage and at least one fish exit channel extends from the crowding net cage. The crowding net cage assembly may further include a horizontal crowding bulkhead movable vertically between a resting position adjacent a bottom of the fish residence volume and a position above the bottom of the fish residence volume, and the crowding net cage may be movable vertically to a position abutting and on top of the crowding bulkhead when the crowding bulkhead is in the position above the bottom of the fish residence volume.

[0005] The horizontal closing element may include a horizontal bottom sheet adapted to selectively cover the bottom the crowding net cage.

[0006] The crowding net cage assembly may further include a powered first bottom sheet drum in attachment with a first end of the bottom sheet and a powered second bottom sheet drum, in attachment with a second end of the bottom sheet, whereby the bottom sheet is adapted to be pulled between the first bottom sheet drum and the second bottom sheet drum.

[0007] The first bottom sheet drum may be attachment to the first end of the bottom sheet with ropes or wires.

[0008] The horizontal bottom sheet may surround a portion of the crowding net cage, whereby the horizontal bottom sheet is movable around the crowding net cage between a position with the horizontal bottom sheet covering the bottom the crowding net cage, and a position where horizontal bottom sheet at least partly cover the top wall.

[0009] The horizontal bottom sheet may form a part of an endless loop surrounding the crowding net cage, wherein the endless loop further includes an open portion, whereby the endless loop is movable around the crowding net cage between the position with the horizontal bottom sheet covering the bottom the crowding net cage, and a position with the open portion located at the bottom the crowding net cage.

[0010] The crowding net cage assembly may further include a horizontal final crowding bulkhead movable vertically between an upper position adjacent the top wall of the crowding net cage and a lower position above and adjacent the at least one fish exit channel.

[0011] The crowding net cage may include a rectangular, covered box framework forming the top wall, the side walls, a first end wall and a second end wall and the bottom. The top wall, the side walls, and the end walls may be covered by a net or mesh.

[0012] The movable, vertical crowding net cage bulkhead may be movable along the sidewalls between the first end wall and a position proximate the second end wall.

[0013] The crowding net cage assembly may furthermore include horizontal bulkhead guides along the side walls for guiding the vertical crowding cage bulkhead.

[0014] The invention furthermore concerns a semi-submersible fish farm with a crowding net cage assembly as described above. The fish farm includes a lower horizontal ring-shaped portion with a lower horizontal internal frame and an upper horizontal ring-shaped portion with an upper horizontal internal frame forming an outer periphery of the fish farm. Peripheral, vertical columns extend between the lower horizontal ring-shaped portion and the upper horizontal ring-shaped portion. Two central vertical columns extend between the lower horizontal internal frame and the upper horizontal internal frame, whereby the two central vertical columns, a portion of the lower horizontal internal frame, a portion of the upper horizontal internal frame and two of the peripheral vertical columns form a rectangular box shaped frame, whereby the net cage assembly is adapted to be located inside the rectangular box-shaped frame. The stationary vertical removable bulkhead and the movable, vertical crowding bulkhead are adapted to cover sides of the rectangular box-shaped frame.

[0015] The net cage may be adapted to be lifted and lowered inside the rectangular box-shaped frame by synchronized lifting winches located at corners of the rectangular box-shaped frame. The synchronized lifting winches may be adapted to lift and lower the horizontal crowding bulkhead.

[0016] Furthermore, the invention concerns a method of crowding fish with the crowding net cage assembly as described above. The method includes providing the stationary vertical removable net wall at the net wall location, moving the movable, vertical crowding net wall towards the stationary vertical removable net wall at a first crowding step, moving the crowding net cage vertically from the position above the fish residence volume and to the position below a sea surface at a depth substantially unaffected by waves in a second crowding step, closing the bottom of the net cage with the horizontal closing element, connecting the at least one fish exit channel to an exit outlet pipe, and moving the vertical crowding cage bulkhead towards the at least one fish exit channel while pumping fish out of the exit outlet pipe in a fourth crowding step.

[0017] The crowding net cage assembly may furthermore include a horizontal crowding bulkhead movable vertically between a resting position adjacent a bottom of the fish residence volume and a position above the bottom of fish residence volume, and the method may then further include moving the horizontal crowding bulkhead vertically from the position adjacent the bottom of the fish residence volume to the position above the bottom of the fish residence volume in a second crowding step ahead of moving the crowding net cage vertically to a position abutting and on top of the crowding bulkhead.

[0018] Alternatively, may the step of moving the horizontal crowding bulkhead vertically from the position adjacent the bottom of the fish residence volume to the position above the bottom of the fish residence volume be performed after or simultaneously with the step of moving the crowding net cage vertically to a position abutting and on top of the crowding bulkhead.

[0019] The crowding net cage assembly may further include a horizontal final crowding bulkhead movable vertically between an upper position adjacent the top wall of the crowding net cage and a lower position above and adjacent the at least one fish exit channel, and the method may then further include moving the horizontal final crowding bulkhead from the upper position adjacent the top wall of the crowding net cage and to the lower position above and adjacent the at least one fish exit channel in a fifth crowding step. Short description of the drawings: Fig. 1 is a perspective view of a fish farm with a net cage assembly of the invention; Fig. 2 is a perspective view of a fish farm of fig. 1 showing further details of the net cage assembly of fig. 1; Fig. 3 is a perspective view of a section of the fish farm showing further details of the net cage assembly of the invention; Fig. 4 is a perspective view of a net cage with a rectangular box frame being a part of the net cage assembly of the invention; and Fig. 5 is a perspective view a detail of a connection for pumping fish between the net cage and the fish farm; Fig. 6 and 7 is a perspective view of a net cage with an alternative embodiment of a bottom sheet in two positions; and Fig. 8 corresponds to fig. 2, showing further details. Detailed description of an embodiment of the invention with reference to the drawings:

[0020] Fig. 1 shows semi-submersible, offshore, fish farm, fish pen or fish breeding facility 1. The farm 1 is designed as a semi-submersible structure with a framework 4 and a ballasting system (not shown) that are typical for semisubmersible platforms. Semi-submersible structures / platforms are well known from the offshore industry and are typically used in connection with the production of oil and gas. Semi-submersible structures / platforms are also used for fish farming to some extent. [0021 ] Semi-submersible fish farms include some elements that distinguish them from ordinary floating fish farms, such as a ballasting system that ensures stability, balance and the right depth. Semi submersibles typically have a relatively low volume in the transition between water and air to reduce the influence of waves.

[0022] A net or mesh (not shown) extends between the elements of the framework 4 to prevent the fish from escaping while allowing water to flow through.

[0023] A crowding net cage 2 of the invention is shown in an upper position for storage. The net cage 2 is used to increase the concentration offish and to pump the fish to a different location such as onto a fish carrying bilge well vessel.

[0024] The framework 4 includes an upper 22 and a lower horizontal ring-shaped portion 21. In the context of this application will “ring-shaped” include both a circular ring and a ring with straight portions resembling a running track, typically with short straight sides (compared to a running rack). The shown horizontal ring-shaped portions 21,22 are polygonal and thus include straight sections. The ring-shaped portions 21,22 have a rectangular cross section.

[0025] Peripheral, vertical columns 23 extend between the ring-shaped portions to form the framework. Horizontal stiffeners 24 extend across the horizontal ringshaped portions 21,22 to improve the structural integrity and to facilitate installation of the various required components.

[0026] Two central, vertical, columns 25 held by the horizontal stiffeners form support for guides for the net cage 2 of the net cage assembly of the invention. The net cage 2 is designed to move vertically up and down along guides held by four vertical columns 23, 25.

[0027] The peripheral vertical columns 23 and the lower horizontal ring-shaped portion 21 may form ballast tanks for ensuring the desired buoyancy and balance.

[0028] A helicopter platform 3 is located on top of the fish farm for transport purposes.

[0029] Several utilities structures are located on top of the framework 4. The utilities structures may include a storage building for aquaculture feeds, a building for accommodation, a structure for the ballasting system, etc..

[0030] Fig. 2 shows the fish farm 1 in more detail, omitting some parts for clarity. Fig. 2 shows the polygonal shape and the rectangular cross-section of the horizontal ring-shaped portions 21,22.

[0031] The fish farm 1 includes the fish residence chamber 15 surrounded by the mesh / net (not shown) holding the fish. An upper and a lower circumferential net wall guide 17 runs along an upper and a lower periphery of the fish farm 1 and guides a vertical crowding net wall 5 with a net providing a barrier for the fish supported by a frame. The vertical crowding 5 is pivotally supported at an inner portion and is allowed to turn about the pivot point and along the circumferential net wall guides 17. The vertical net wall 5 includes a frame and a net structure that is designed to selectively cover the frame when the vertical crowding net wall 5 is used. A stationary, vertical, removable, net wall is selectively located at the crowding net location 20 when crowding takes place. A horizontal crowding bulkhead 6 covers a rectangular bottom area below the cage 2. The rectangular bottom area has a shape and dimensions conforming to the cage 2.

[0032] An upper horizontal square frame 27 and a lower horizontal square frame 26 are secured to the upper horizontal ring-shaped portion 22 and the lower horizontal ring-shaped portion 21 respectively. Vertical columns 23, 25 extend between the corners of the horizontal square frames 27, 26, whereby a rectangular box-shaped frame is defined. The net cage 2 is controlled to move down and up inside this box-shaped frame. The side walls (in “radial” direction) of the box-shaped frame are covered with nets or tarpaulins during the crowding operation. The nets or tarpaulins are removable and are removed during normal operation of the fish farm.

[0033] A driving mechanism (not shown) is provided to drive the vertical crowding net wall 5 along the circumferential net wall guides and the crowding net wall 5 can move all the way around the tubular framework until the motion ends at a position adjacent the net cage 2. The net cage 2 is in an upper storage position above the sea level.

[0034] Fig. 3 shows the rectangular box-shaped frame with the net cage assembly 30 with the net cage 2 and the horizontal cage crowding bulkhead 6 in greater detail. The net cage 2 has been lowered by a wire at each comer by synchronized winches 7 and is in a lower position. The top of the net cage is at a position below the sea level at a depth substantially unaffected by waves. The horizontal cage crowding bulkhead 6 is movably provided inside the rectangular box-shaped frame and is shown in its lower position. A bottom sheet forming a floor in the net cage 2 is open, thus allowing fish to enter the net cage. The ‘radial” vertical net covers the side of the rectangular box-shaped frame (to the right on the figure. Not shown). An exit channel coupling cross bar 37 is fixed between the two vertical columns 23 and hold the exit pipes and the exit channel couplings. The stationary vertical removable net wall 8 is schematically indicated at an upper portion next to the net cage and extends all the way down to the bottom of the fish farm.

[0035] The horizontal cage crowding bulkhead 6 allows all the fish in the entire volume between the net walls to be removed without having to press the fish far down with the net cage. Pressing fish downwards is considered to reduce the welfare of salmonoids and is generally avoided.

[0036] Fig 4 is a perspective view of the net cage 2 of figs. 1 -3. The net cage 2 includes a rectangular box frame 36 with a first side wall 32, a second side wall 33, a first end wall 34, a second end wall 35 and a net cage top wall 31. The walls are rectangular and hold nets or mesh with a mech size allowing flow of water while preventing the fish from escaping. The net cage is adapted to be lowered inside the rectangular box-shaped frame as discussed above and includes a removable floor cover / bottom sheet 13 that is moved by a bottom sheet mechanism shifting the bottom sheet between the position covering the net cage bottom and the position away from the net cage bottom to selectively allow fish inside the net cage and to trap fish inside the net cage 2. The bottom sheet mechanism is shown with a first bottom sheet drum 11 and a second bottom sheet drum 12. The drums are driven to pull the bottom sheet over or away from the bottom of the net cage 2. A vertical crowding cage bulkhead 14 is shown in an intermediate position between a first end wall 34 and a second end wall 35. The initial position of the bulkhead 14 before the crowding begins is adjacent the left / second (inner) wall 35 of the net cage 2. The bulkhead 14 is movable between second end wall 35 and almost all the way to the right / first (outer) end wall 34 along horizontal bulkhead guides 16. Wires (not shown) are typically used to pull the bulkhead 14 between the various positions. The bottom sheet 13 provides a smooth bottom surface along the bottom of the net cage 2 and ensures that fish not get caught / jammed in a gap between a bottom edge of the vertical bulkhead 14 and the bottom sheet 13.

[0037] In an embodiment (fig. 8) is the horizontal cage crowding bulkhead omitted and the net cage 2 is lowered as far down as desired before the net cage is closed with the bottom sheet 13 forming a horizontal closing element. The desired amount offish may then be removed from the net cage, leaving some fish below the net cage.

[0038] A horizontal cage crowding bulkhead 10 is movable in a vertical direction to crowd fish at a last stage of the crowding to prevent fish from getting caught between the bulkhead 14 and the outer / first end wall 34 of the net cage 2.

[0039] Two fish exit channels 9 are located at the outer and lower end of the net cage 2 for allowing fish to be pumped out of the net cage.

[0040] Fig. 5 is a perspective view a detail of the outer and lower end of the net cage 2 with the fish exit channel 9. An exit outlet pipe 19 for connection with a fish transport channel (not shown) is fixed to the fish farm 1 with an exit channel coupling cross bar 37 and forms an exit channel coupling 18 connecting the fish exit channels 9 and the exit outlet pipe 19. The coupling between the fish exit channel 9 and the exit outlet pipe 19 automatically provides a connection when the net cage is lowered onto the coupling. [0041 ] A method of removing fish from the fish farm 1 involves the steps of: installing a net to provide a first vertical, radial wall of the rectangular box-shaped frame; installing a net on the vertical crowding net wall 5; moving the vertical crowding net wall 5 towards the rectangular box-shaped frame until the vertical crowding net wall 5 is adjacent the rectangular boxshaped frame to provide a second vertical, radial wall of the rectangular boxshaped frame and the desired amount offish is trapped; lifting the farm horizontal crowding bulkhead 6 from the bottom of the rectangular box-shaped frame; lowering the net cage 2 onto the farm horizontal crowding bulkhead 6 to a position where the top of the net cage is submerged and substantially unaffected by wave action to trap the fish inside the net cage 2; move the bottom sheet 13 to seal the bottom of the net cage 2; pump fish through the fish exit channels 9 and the exit outlet pipes 19; continue pumping fish while moving the vertical crowding cage bulkhead 14 towards the outer / first end wall 34 of the net cage 2 until the crowding cage bulkhead 14 is close to the first end wall 34 of the net cage but without trapping fish; continue pumping fish while lowering the horizontal final crowding bulkhead 10 until the desired amount offish has been pumped out.

[0042] The bottom sheet 13 may be rolled up, the nets may be removed from the vertical crowding net wall 5 and the frame wall, the bulkhead may return to its inner position, the farm horizontal crowding bulkhead 6 may return to the bottom, and the net cage may be lifted out of the water to its storage position above the sea level.

[0043] Figs. 6 and 7 show an alternative embodiment of the net cage 2, where the first and second bottom sheet drums for the bottom sheet 13 are substituted with winches 38 pulling the bottom sheet 13 between a position on top of the net cage 2, partly covering the top wall 31 of the net cage 2 and the end wall 34 (fig. 6), and a position covering the bottom of the net cage 2 (fig. 7). The embodiment of figs. 6 and 7 omits rolling the bottom sheet onto drums, but rather pulls the bottom sheet 13 between the bottom of the net cage 2 and a position away from the bottom. The rectangular box frame 36, the horizontal bulkhead guides 16, the first end wall 34, the second end wall 35 and the top wall 31 corresponds to the embodiment of fig. 4.

[0044] Fig. 8 corresponds to fig. 2, omitting the farm horizontal crowding bulkhead and show the lower horizontal square frame 26 and the stationary vertical removable net wall 8 on the stationary, vertical net wall location 20. The movable vertical crowding net wall 5 is shown in two different locations and moves along the upper and lower circumferential bulkhead guides 17. The net cage 2 is located in its resting position on top of the upper horizontal square frame 27. The net cage 2 may move all the way to the bottom of the fish farm, omitting the movable horizontal bulkhead.

[0045] This disclosure relies on the terms “horizontal” and “vertical” and other terms relating to an absolute orientation for simplicity and to facilitate the description of the invention. This orientation assumes a horizontal and straight orientation that will be the typical orientation during operation of the fish farm. A skilled person will however understand that this may be deviated from during manufacturing and real-life operation, and the present invention is also intended to cover such situations.

[0046] It should also be mentioned that the different embodiments of the mechanism for moving the bottom sheet may be used in both the situation with and without a movable horizontal crowding bulkhead. In fig. 8 is the horizontal bulkhead omitted but fig. 8 is also relevant for the embodiment with a movable horizontal bulkhead.

[0047] 1 Fish farm 20 Stationary, vertical net wall location 2 Cage 21 Lower horizontal ring-shaped portion 3 Helicopter platform 22 Upper horizontal ring-shaped portion 4 Tubular framework 23 Peripheral, vertical columns 5 Movable vertical crowding net wall 24 Horizontal stiffeners 6 Farm horizontal crowding bulkhead 25 Central vertical columns 7 Synchronized cage lifting winches 26 Lower horizontal square frame 8 Stationary vertical removable net wall 27 Upper horizontal square frame 9 Fish exit channels 28 Residence chamber bottom 10 Horizontal final crowding bulkhead 29 11 First bottom sheet drum 30 Crowding net cage assembly 12 Second bottom sheet drum 31 Net cage top wall 13 Bottom sheet 32 First side wall 14 Vertical crowding cage bulkhead 33 Second side wall 15 Fish residence volume 34 First end wall 16 Horizontal bulkhead guides 35 Second end wall 17 Circumferential bulkhead guides 36 Rectangular box frame 18 Exit channel coupling 37 Exit channel coupling cross bar 19 Exit outlet pipe 38 Bottom sheet winch 20 Crowding net location 09 05 25

Claims

1. A crowding net cage assembly (30) for a fish farm with a fish residence volume, a stationary vertical removable net wall (8) at a net wall location (20), and a movable, vertical crowding net wall (5) comprising:a crowding net cage (2) with a top wall (31), side walls (32, 33) and end walls (34, 35), wherein the crowding net cage (2) is movable vertically between a position above the fish residence volume (15) and a position below a sea surface substantially unaffected by waves;wherein the crowding net cage (2) is located between the stationary vertical removable net wall (8) at the net wall location (20), and the movable, vertical crowding net wall (5);a horizontal closing element adapted to selectively close a bottom the crowding net cage (2);a movable, vertical crowding net cage bulkhead (14) in an inside of the crowding net cage (2); andat least one fish exit channel (9) from the crowding net cage (2).

2. The crowding net cage assembly (30) of claim 1, further including:a horizontal crowding bulkhead (6) movable vertically between a resting position adjacent a bottom of the fish residence volume (15) and a position above the bottom of the fish residence volume (15); andwherein the crowding net cage (2) is movable vertically to a position abutting and on top of the crowding bulkhead (6) when the crowding bulkhead (6) is in the position above the bottom of the fish residence volume (15).

3. The crowding net cage assembly (30) of claim 1, wherein the horizontal closing element includes a horizontal bottom sheet (13) adapted to selectively cover the bottom the crowding net cage (2).

4. The crowding net cage assembly (30) of claim 3, further including:a first bottom sheet drum (11) in attachment with a first end of the bottom sheet (13);a second bottom sheet drum (12), in attachment with a second end of the bottom09 05 25sheet (13), whereby the bottom sheet is adapted to be pulled between the first bottom sheet drum (11) and the second bottom sheet drum (12).

5. The crowding net cage assembly (30) of claim 4, wherein the first bottom sheet drum (11) is attachment to the first end of the bottom sheet (13) with ropes or wires.

6. The crowding net cage assembly (30) of claim 3, wherein the horizontal bottom sheet (13) surround a portion of the crowding net cage (2), whereby the horizontal bottom sheet (13) is movable around the crowding net cage (2) between a position with the horizontal bottom sheet (13) covering the bottom the crowding net cage (2), and a position where horizontal bottom sheet (13) at least partly cover the top wall (31).

7. The crowding net cage assembly (30) of claim 6, wherein the horizontal bottom sheet (13) forms a part of an endless loop surrounding the crowding net cage (2), wherein the endless loop further includes an open portion, whereby the endless loop is movable around the crowding net cage (2) between the position with the horizontal bottom sheet (13) covering the bottom the crowding net cage (2), and a position with the open portion located at the bottom the crowding net cage (2).

8. The crowding net cage assembly (30) of any of the preceding claims, further including a horizontal final crowding bulkhead (10) movable vertically between an upper position adjacent the top wall of the crowding net cage (2) and a lower position above and adjacent the at least one fish exit channel (9).

9. The crowding net cage assembly (30) of any of the preceding claims, wherein the crowding net cage (2) includes a rectangular, covered box framework forming the top wall, the side walls, a first end wall and a second end wall and the bottom; and wherein the top wall, the side walls, and the end walls are covered by a net or mesh.09 05 2510. The crowding net cage assembly (30), of claim 1, wherein the movable, vertical crowding net cage bulkhead (14) is movable along the sidewalls between the first end wall and a position proximate the second end wall.

11. The crowding net cage assembly (30), of claim 10, further including horizontal bulkhead guides (16) along the side walls for guiding the vertical crowding cage bulkhead (14).

12. A semi-submersible fish farm (1) with a crowding net cage assembly (30) of one of the claims 1-10, comprising:a lower horizontal ring-shaped portion (21) with a lower horizontal internal frame (26) and an upper horizontal ring-shaped portion (22) with an upper horizontal internal frame (27) forming an outer periphery of the fish farm (1);peripheral vertical columns (23) extending between the lower horizontal ring-shaped portion (21) and the upper horizontal ring-shaped portion (22);two central vertical columns (25) between the lower horizontal internal frame (26) and the upper horizontal internal frame (27), whereby the two central vertical columns (25), a portion of the lower horizontal internal frame (26), a portion of the upper horizontal internal frame (27) and two of the peripheral vertical columns (23) form a rectangular box shaped frame;wherein the net cage assembly is adapted to be located inside the rectangular boxshaped frame; andwherein the stationary vertical removable net wall and the movable, vertical crowding net wall (5) are adapted to cover sides of the rectangular box-shaped frame.

13. The semi-submersible fish farm (1) of claim 12, wherein the net cage (2) is adapted to be lifted and lowered inside the rectangular box-shaped frame by synchronized lifting winches (7) located at comers of the rectangular box-shaped frame.09 05 2514. The semi-submersible fish farm (1) of claim 12 or 13, wherein the crowding net cage assembly (30) further includes a horizontal crowding bulkhead (6) movable vertically between a resting position adjacent a bottom of the fish residence volume (15) and a position above the bottom of the fish residence volume (15), and wherein the horizontal crowding bulkhead (6) is adapted to be lifted and lowered inside the rectangular box-shaped frame by synchronized lifting winches located at corners of the rectangular box-shaped frame15. A method of crowding fish with the crowding net cage assembly (30) of one of the claims 1-11 comprising:Providing the stationary vertical removable net wall (8) at the net wall location (20); moving the movable, vertical crowding net wall (5) towards the stationary vertical removable net wall (8) at a first crowding step;moving the crowding net cage (2) vertically from the position above the fish residence volume (15) and to the position below a sea surface substantially unaffected by waves in a second crowding step;closing the bottom of the net cage (2) with the horizontal closing element;connecting the at least one fish exit channel (9) to an exit outlet pipe (19); andmoving the vertical crowding cage bulkhead (14) towards the at least one fish exit channel (9) while pumping fish out of the exit outlet pipe (19) in a fourth crowding step.

16. The method of crowding fish of claim 15, wherein the crowding net cage assembly (30) furthermore includes a horizontal crowding bulkhead (6) movable vertically between a resting position adjacent a bottom of the fish residence volume (15) and a position above the bottom offish residence volume (15), the method further including:moving the horizontal crowding bulkhead (6) vertically from the position adjacent the bottom of the fish residence volume (15) to the position above the bottom of the fishresidence volume (15) in a second crowding step in addition to moving the crowding net cage (2) vertically to a position abutting and on top of the crowding bulkhead (6).

17. The method of crowding fish of one of claims 15, 16, wherein the crowding net cage assembly (30) furthermore includes a horizontal final crowding bulkhead (10) movable vertically between an upper position adjacent the top wall of the crowding net cage (2) and a lower position above and adjacent the at least one fish exit channel (9), the method further including:moving the horizontal final crowding bulkhead (10) from the upper position adjacent the top wall of the crowding net cage (2) and to the lower position above and adjacent the at least one fish exit channel (9) in a fifth crowding step.

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