WO2020013707A1

WO2020013707A1 - Device and method for retaining fish in a fish cage compartment

Info

Publication number: WO2020013707A1
Application number: PCT/NO2019/050149
Authority: WO
Inventors: Eirik GRAVDAL; Øyvind OALAND
Original assignee: Mowi ASA
Priority date: 2018-07-13
Filing date: 2019-07-11
Publication date: 2020-01-16
Also published as: NO20190874A1

Abstract

It is described a floating fish cage (1) for farming fish (2), said fish cage (1) having a lower portion (3) and an upper portion (4), the lower portion (3) comprising a submerged fish enclosure (30) and the upper portion (4) comprising a channel (40) extending from the submerged fish enclosure (30) towards a water surface (5), wherein a portion (41) of the channel (40) is separated from the submerged fish enclosure (30) by a separation device (6) comprising an inlet (60) and an outlet (61), the separation device (6) being tapered from the inlet (60) towards the outlet (61) thereby allowing fish (2) to swim in one direction (62) only through the separation device (6) from the submerged fish enclosure (30) into the portion (41) of the channel (40), wherein the separation device (6) at the outlet (61) has a free end portion enabling the fish (2) to enter the channel (40) undisturbed. (Fig. 1)

Description

DEVICE AND METHOD FOR RETAINING FISH IN A FISH CAGE COMPARTMENT

The invention relates to a fish cage for farming fish. More particularly, the invention relates to a fish cage having a submerged fish enclosure that keeps fish at a depth where expo sure to harmful

organisms is limited, and wherein a channel extends from the submerged fish enclosure to the water surface, the channel and the submerged fish enclosure being separated by a one-way port restricting fish to swim only from the submerged fish enclosure into the channel through the port.

Fish farming in seawater commonly takes place in floating cages. The cages usually con- sist of a net forming an enclosure and are kept in position by floating elements and an chors. It is well known that fish kept in cages at sea are exposed to harmful organisms and may be infected by parasites. The fish may also be exposed to toxic, planktonic algae or algal toxins in the water. Especially external crustaceous parasites such as salmon louse is a problem in the farming of salmonoids such as salmon and trout in the sea. One reason being that salmon preferably moves in the upper water layers, and so does the louse to increase their chances of finding a host.

To avoid fish being exposed to parasites it is known to submerge the enclosure to a depth where parasites are not present. Salmon is a so-called physostomous fish, meaning they have an open swim bladder with connection to the throat of the fish. To maintain gas in the swim bladder, the salmon ascend to the water surface to swallow air. One solution is disclosed in document WO201366191 wherein a submerged enclosure is connected to a channel stretching from the enclosure to the water surface. The channel allows fish to swim up to the water surface from the submerged enclosure. The channel may be cov ered by a parasite-dismissing material, ensuring the fish are not exposed to parasites as they swim through a possibly parasite-infested part of the water column. A disadvantage being that the fish are free to swim back down into the enclosure through the channel once they have been at the water surface. The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art. One object of the invention being to retain fish in the channel, and thus not allow them to freely swim back into the submerged enclosure. The object is achieved through features, which are specified in the description below and in the claims that follow.

The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

In a first aspect the invention relates more particularly to a floating fish cage for farming fish, said floating fish cage having a lower portion and an upper portion, the lower portion comprising a submerged fish enclosure and the upper portion comprising a channel ex tending from the submerged fish enclosure towards a water surface, wherein a portion of the channel is separated from the submerged fish enclosure by a separation device, such as a fyke trap, comprising an inlet and an outlet, the separation device being tapered from the inlet towards the outlet thereby allowing fish to swim in one direction only through the separation device from the submerged fish enclosure into the portion of the channel, wherein the separation device at the outlet has a free end portion enabling the fish to en ter the channel undisturbed. The effect of the invention is that fish may be retained in the portion of the channel, and thus the fish are not able to freely swim back into the sub- merged fish enclosure. It should be understood that a portion of channel may be the whole channel or a smaller portion of the channel. A further effect of the invention is that the fish may swim undisturbed through the separation device, thus avoiding that the fish undergoes any form of stress. This is vital to maintain good fish health. A fyke trap is well known within the art and is commonly used in fish pots and lobster pots. When retained in the channel, the fish may be treated with medicaments mixed into the water, so-called bath treatment. An internal volume of the channel may be considerably smaller than an internal volume of the submerged fish enclosure. Thus, the bath treatment may be carried out with less medicaments as compared to bath treatment in the entire fish cage. This way of treating the fish may also induce less stress on the fish as compared to conventional bath treatment where the internal volume of the enclosure is decreased by lacing up the net to crowd the fish.

In one embodiment, the floating fish cage may further comprise at least one conduit con figured to guide fish out of the portion of the channel. In one embodiment, the conduit may guide the fish back to the submerged fish enclosure. This embodiment of the invention has the effect that fish may return to the submerged fish enclosure in a controlled manner. The conduit may be configured to be selectively opened or closed, thereby controlling when fish is allowed to return to the submerged fish enclosure. In one embodiment, the floating fish cage may comprise several conduits for faster discharge of fish from the por tion of the channel.

In one embodiment, the floating fish cage may further comprise a second submerged fish enclosure. This embodiment of the invention has the effect that the fish retained in the portion of the channel may be returned to a separate enclosure. This enables control of what fish has been in the portion of channel and what fish has not, for example for treat ment. In one embodiment, the at least one conduit may connect the portion of the channel to said second submerged fish enclosure. In one embodiment, the second submerged fish enclosure may be a part of the same fish cage, the two enclosures being separated by a partition, such as a net or watertight material. In another embodiment, the second sub- merged fish enclosure may be separated from the fish cage, for example as a standalone fish cage.

In one embodiment, the floating fish cage may further comprise a fish registration device, wherein the fish registration device comprises at least one camera and a central pro cessing unit (CPU), the camera being configured to make images of the fish to be pro- cessed in an imaging software running on the CPU to analyse said images. This embodi ment of the invention has the effect that the fish registration unit may provide various parameters concerning the fish that are of interest to a fish farmer. Said parameters may be contributing factors for determining a welfare of the fish in the fish cage. In one embod iment, the imaging software may be configured to count the fish, estimate a size and/or weight of the fish and/or identifying louse on the fish.

The fish registration device may be arranged in the portion of the channel, adjacent the outlet of the separation device or in the submerged fish enclosure. In one embodiment, the fish cage may comprise several fish registration devices, wherein at least one is ar ranged on either side of the separation device. This embodiment of the invention has the effect that the several images may be made of the fish, for example before and after treatment. In one embodiment, the fish registration device may be arranged along the at least one conduit. In one embodiment, the floating fish cage may further comprise a fish treatment device. This embodiment of the invention has the effect that parasites on the fish may be combat ted and thus improve the health and welfare of the fish, which in turn may cause the fish to grow faster and decrease mortality. By combatting it should be understood anything that may stop parasites from harming the fish, such as killing or paralyzing the parasites, or harming their fertility. In one embodiment, the fish treatment device may combat para sites by means of light, such as infrared light or laser. In one embodiment, the fish treat ment device may combat parasites by medicaments, such as hydrogen peroxide or pyre- troids, mixed into water in a bath chamber. In one embodiment, the fish treatment device may be arranged along the at least one conduit. This embodiment of the invention has the effect that it provides a way of captur ing all the fish as they must pass through the conduit when returning to the submerged fish enclosure.

In one embodiment, the separation device may be invertible, allowing fish to swim from the portion of the channel and into the submerged fish enclosure. This embodiment of the invention has the effect that the portion of the channel may be emptied of fish efficiently if required. Inverting the separation device may for example be done by hoisting or pulling in a drawworks or line(s) connected to said device. In one embodiment, the outlet on the separation device may be opened, meaning the outlet forms a substantially similar open- ing as the inlet. This embodiment of the invention has the same effect as inverting the separation device.

In one embodiment, the separation device and a side portion of the channel may be pro vided with one of:

- a watertight, rigid material;

- a watertight cloth material; and

- a plankton-dismissing net material.

In another embodiment, the separation device and a portion of a peripheral wall of the channel may be provided with a watertight, rigid material. In a further embodiment, the separation device and a portion of a peripheral wall of the channel may be provided with a watertight cloth material. In a further embodiment, the separation device and a portion of a peripheral wall of the channel may be provided with a plankton-dismissing net material. These three embodiments of the invention have the effect that said material may bar out unwanted objects, such as parasites, plankton or algae, floating horizontally in the upper water layers from the portion of the channel. Another effect may be to entrap water in the portion of the channel, for example during bath treatment of the fish such that chemicals mixed into the water do not get washed out or diluted by the water flow in the upper water layer. The separation device may be invertible, thereby allowing fish to swim from the portion of the channel and into the submerged fish enclosure. By inverting the separation device, the channel may be emptied of fish in an efficient manner without inducing stress on the fish. Compared to conventional methods of moving fish such pumping or forced displacement by nets, inverting the separation device is less invasive and gentler on the fish. In one embodiment, a lower portion of the channel extends into the submerged fish enclo sure. By extending the channel into the submerged fish enclosure, the length of the chan nel increases and may thus hold more fish. Conventionally, the channel stretches from an upper edge of the submerged fish enclosure to the water surface. The depth at which the upper edge of submerged fish enclosure is located is determined by the depth at which lice do not go to. By extending the channel past, i.e. deeper than, the upper edge of the submerged fish enclosure the separation device may also be located deeper, and thus the portion of the channel holding fish increases.

In one embodiment, the side portion of the lower portion of the channel extending into the submerged fish enclosure is provided with multiple horizontally orientated separation de- vices. Having multiple separation devices enables more fish to enter the channel in a giv en period. Having horizontally orientated separation devices enables the fish to swim through the separation device horizontally, which is a more natural direction for the fish to swim in. This may result in more fish entering the channel as compared to having a verti cally orientated separation device. In a second aspect the invention relates more particularly to a method of retaining fish in a portion of a channel in a floating fish cage, wherein the method comprises the steps of:

- providing the floating fish cage;

- providing fish in the submerged fish enclosure;

- keeping the fish in the submerged fish enclosure such that the fish may swim through the separation device; and

- retaining the fish in the portion of the channel.

The method has the effect of providing a simple and robust way of separating fish from a submerged fish enclosure and into a channel and retaining the fish in the channel. In one embodiment, fish feed may be provided in the portion of the channel. In one embodiment, the channel may be supplied with water creating a vertical current. These two embodi ments of the invention have the effect of luring more fish, especially salmon, to swim through the separation device. The water supplied to the channel may be collected from a depth where there are no parasites or plankton.

In one embodiment, the method may further comprise the step of:

- covering the separation device and a peripheral wall of the portion of the channel by a watertight material.

This embodiment of the invention has the effect of barring parasites and plankton from the portion of the channel.

In one embodiment, the method may further comprise the step of:

- adding a medicament to the water inside the portion of the channel.

This embodiment of the invention has the effect that the fish may be bath treated while retained inside the portion of the channel. One advantage being that the water volume inside the portion of the channel may be considerably smaller than in a conventional net cage with its net raised and with a skirt around the side wall and a cloth under the net cage. A second advantage being that the job of raising the net is avoided. A third ad vantage being that at least parts of the medicaments added to the water in the portion of the channel may be retrieved after use for recycling. In the following is described examples of preferred embodiments illustrated in the accom panying drawings, wherein:

Figure 1 shows a floating fish cage according to one embodiment of the invention; Figure 2 shows, in a larger scale than figure 1 , a channel according to the invention; Figure 3 shows, in a larger scale than figure 2, a separation device according to the invention;

Figure 4 shows, in a smaller scale than figure 1 , a fish cage with a second sub

merged fish enclosure according to an alternative embodiment of the inven tion;

Figure 5 shows a fish cage with a second submerged fish enclosure according to a further alternative embodiment of the invention; Figure 6 shows a channel according to an alternative embodiment of the invention; and

Figure 7 shows a channel according to a further alternative embodiment of the in vention. The figures are schematic, and the different parts are drawn to different scales, which not necessarily correspond to their actual scale relative to each other. Details that are not considered relevant to the illustrate what is new with the invention may have been exclud ed from the figures.

In the figures, the reference numeral 1 indicates a floating fish cage 1 , henceforth denoted cage 1 , according to one embodiment of the invention. A lower portion 3 of the cage 1 comprises a submerged fish enclosure 30, henceforth denoted enclosure 30. The enclo sure 30 may be formed from a net, a cloth or a stiff material. An upper portion 4 of the cage 1 comprises a channel 40 extending from the enclosure 30 to a water surface 5. The channel 40 forms a connection between the enclosure 30 and the water surface 5 such that fish 2 may swim up to swallow air.

The channel 40 is connected to a ceiling 301 on the enclosure 30. The ceiling 301 keeps fish 2 from swimming up towards the water surface 5 in other places than via the channel 40. The ceiling 301 is arranged at a depth where toxic algae and/or parasites are limited, and preferably not present. The channel 40 is suspended in a first floatation means 400 at the water surface 5. The first floatation means 400 is shown comprising a pipe forming a circle. In one embodiment (not shown), the first floatation means 400 may comprise sev eral concentric pipes 80, 81 provided with grating on top to form a walkway. The enclo sure 30 is suspended in a second floatation means 8 at the water surface 5. The second floatation device 8 forms a circle and comprises two concentric pipes connected by evenly distributed brackets 82. The second floatation means 8 may be provided with grating (not shown) between the two pipes 80, 81 , thus forming a walkway around the fish cage 1.

A separation device 6 separates a portion 41 of the channel 40 from the enclosure 30.

The separation device 6 is tapered from an inlet 60 to an outlet 61 , see figure 3. It should be understood that figure 3 depicts only one embodiment of the separation device 6 and that it may look different for other embodiments. The shape of the separation device 6 is such that it is easy for fish 2 to swim in one direction 62 (arrows), but not the opposite way once the fish 2 have passed the outlet 61 , similar to a conventional fyke trap. In one em- bodiment (not shown), the separation device 6 may be inverted such that the fish 2 may swim from the portion 41 of the channel 40 into the enclosure 30.

The end portion of the separation device 6 at the outlet 61 is a free end portion. I.e. the end portion is not connected to any other means such as a pump or a registration device. This enables the fish 2 to swim through the separation device 6 and into the channel 40 undisturbed.

Figure 2 shows a detail of the cage 1 wherein a conduit 7 is arranged between the portion 41 of the channel 40 and the enclosure 30. The conduit 7 enables return of fish 2 back to the enclosure 30. The conduit 7 may be configured for selective opening and closing such as to control the return of fish 2. Figure 2 depicts one conduit 7, however, in another em bodiment, such as in figure 4, the fish cage 1 may comprise several conduits 7. The con duit 7 may also be arranged through the separation device 6 (not shown). This has the advantage of not introducing any potential“leakage” points in the fish cage. A leakage point meaning a point where fish 2 might escape from the fish cage in case of damage or malfunction in the conduit 7.

Figure 2 further shows a registration unit 9 arranged on the conduit 7. It should be under stood that the registration unit 9 may be arranged in a different location in another embod iment. This particular registration unit 9 is configured to register, depicted by wireless sig nal 90, various parameters of the fish 2 as they pass through the conduit 7. The various parameters may for example be length, weight, colour or number of lice on the skin of the fish. The data generated by the registration unit 9 may be transmitted to a central pro cessing unit (CPU) 10 via cable 1 1 or wirelessly 12. The data may be processed by dedi cated software running on the CPU 10, before being transmitted to an operator (not shown), either directly or via a remote server such as a cloud storage (not shown). The CPU 10 may also transmit raw data for later processing. Transmittal may be done wire lessly 12, or via cable (not shown).

Figure 2 also shows a treatment device 13 arranged along the conduit 7. The type of treatment carried out by the treatment device 13 may vary. The treatment device 13 de picted in the figure may be configured for bath treatment. The treatment device 13 is pro- vided with a bath chamber (not shown). The fish 2 enter the treatment device 13 on their way through the conduit 7, and when in the treatment device 13 the fish 2 are showered or bathed with a water-medicament mixture, or the fish may be treated mechanically. Figure 4 shows the fish cage 1 comprising a second submerged fish enclosure 31 , hence forth denoted second enclosure 31. Figure 4 shows the second enclosure 31 arranged in a dedicated fish cage 1’. An alternative embodiment is depicted in figure 5, wherein the second enclosure 31 is arranged in a dedicated portion of the same cage 1 . Fish 2 from the portion 41 of the channel 40 is routed to the second enclosure 31 via a dedicated con duit 7’. One advantage of returning fish 2 to the second enclosure 31 is that it is easy to keep control of what fish 2 that has been in the portion 41 of the channel 40, and what fish 2 that has not. This may be advantageous during for example bath treatment to ensure the same fish 2 are not treated several times. Figure 4 further shows a conduit 7 leading back to the enclosure 30. The conduit 7 may for example be employed to adjust a number of fish 2 in the portion 41 of the channel 40 before treatment. In one embodiment (not shown), the separation device 6 is closable to control the number of the fish 2 in the portion 41 of the channel 40.

Figure 5 shows the two enclosures 30, 31 being separated by a partition 32. The partition 32 may be made from a watertight material to avoid the fish 2 in the two enclosures 30, 31 affecting each other, for example by transferring parasites, plankton and/or algae through the partition 32.

Figure 6 shows the channel 40 extending into the enclosure 30. The separation device 6 is arranged below the ceiling 301 , resulting in a larger portion 41 of the channel 40 being available for retaining fish 2. It should be noted that the location of the separation device 6 within the channel 40 may vary for different embodiments of the invention.

Figure 7 shows the channel 40 extending into the enclosure 30 and two separation devic es 6 arranged on a side portion 42 of the channel 40. It should be noted that the number of separation devices 6 may vary for another embodiment. This embodiment of the inven- tion has the advantage of the separation devices 6 being arranged horizontally, which is a more natural swimming direction for fish 2. This may result in more fish 2 entering the por tion 41 of the channel 40.

Claims

C l a i m s

A floating fish cage (1 ) for farming fish

(2), said fish cage (1 ) having a lower por tion (3) and an upper portion (4), the lower portion

(3) comprising a submerged fish enclosure (30) and the upper portion

(4) comprising a channel (40) extending from the submerged fish enclosure (30) towards a water surface

(5),

c h a r a c t e r i s e d i n that a portion (41 ) of the channel (40) is separated from the submerged fish enclosure (30) by a separation device (6), such as a fyke trap, comprising an inlet (60) and an outlet (61 ), the separation device (6) being tapered from the inlet (60) towards the outlet (61 ) thereby allow ing fish (2) to swim in one direction (62) only through the separation device (6) from the submerged fish enclosure (30) into the portion (41 ) of the channel (40), wherein the separation device

(6) at the outlet (61 ) has a free end portion ena bling the fish (2) to enter the channel (40) undisturbed.

The floating fish cage (1 ) according to claim 1 , further comprising at least one conduit (7) configured to guide fish (2) out of the portion (41 ) of the channel (40).

The floating fish cage (1 ) according to claim 1 or 2, further comprising a second submerged fish enclosure (31 ).

The floating fish cage (1 ) according to any of the preceding claims, further com prising a fish registration device (9), wherein the fish registration device (9) com prises at least one camera and a central processing unit (CPU) (10), the camera being configured to make images of the fish (2) to be processed in an imaging software running on the CPU (10) to analyse said images.

The floating fish cage (1 ) according to claim 4, wherein the fish registration unit (9) is arranged along the conduit (7).

The floating fish cage (1 ) according to any of the preceding claims, further com prising a fish treatment device (13).

The floating fish cage (1 ) according to claim 6, wherein the fish treatment device (13) is arranged along the conduit

(7).

8. The floating fish cage (1 ) according to any of the preceding claims, wherein the separation device (6) is invertible, allowing fish (2) to swim from the portion (41 ) of the channel (40) and into the submerged fish enclosure (30).

9. The floating fish cage (1 ) according to any of the preceding claims, wherein the separation device (6) and a side portion (42) of the channel (40) is provided with one of:

- a watertight, rigid material;

- a watertight cloth material; and

- a plankton-dismissing net material.

10. The floating fish cage (1 ) according to any of the preceding claims, wherein the separation device (6) is invertible, thereby allowing fish (2) to swim from the por tion (41 ) of the channel (40) and into the submerged fish enclosure (30).

1 1 . The floating fish cage (1 ) according to any of the preceding claims, wherein a lower portion of the channel (40) extends into the submerged fish enclosure (30).

12. The floating fish cage (1 ) according to claim 1 1 , wherein the side portion (42) of the lower portion of the channel (40) extending into the submerged fish enclosure is provided with multiple horizontally orientated separation devices (6).

13. A method of retaining fish (2) in a portion (41) of a channel (40) in a floating fish cage (1 ) according to claim 1 , wherein the method comprises the steps of:

- providing the floating fish cage (1 );

- providing fish (2) in the submerged fish enclosure (30);

- keeping the fish (2) in the submerged fish enclosure (30) such that the fish (2) may swim through the separation device (6) and directly into the portion (41 ) of the channel (40); and

- retaining the fish (2) in the portion (41 ) of the channel (40).