NO20191304A1 - Device and method for collection of fish - Google Patents

Description

DEVICE AND METHOD FOR COLLECTION OF FISH

Field of the invention

The present invention relates to a method and a device for separating nonswimming, weak, or dead fish from actively swimming fish after transfer to a sea cage through a release inlet, wherein the device comprises a conical collection plate with a downwards oriented cone; the collection plate further comprises an outlet in the cone; and a suction pipe connected to the outlet.

Furthermore, the present invention relates to a use of said device for separating non-swimming, weak or dead fish from actively swimming fish after the fish was transported, handled and/or treated.

Background of the invention

Handling, treatments such as vaccination, different forms of disease treatments and prophylaxis, grading of fish, and transport of fish are typical procedures in today’s aquaculture production of e.g. of the Atlantic salmon Salmo salar.

Due to an increase in ectoparasitic sea lice infections, in particular of Lepeophtheirus salmonis infecting the Atlantic salmon Salmo salar, delousing treatments have become common operations in the production cycle of salmon. Delousing techniques may comprise mechanical delousing by mechanical removing the lice attached to the fish skin, chemical treatment, fresh water exposure, warm water exposure, ultrasound treatment and combinations thereof.

Most commonly, lice-infected fish will be removed from a sea based net cage where they are cultivated by pumping them up to a barge where they are exposed to a delousing treatment and eventually pumped back into the same or a different net cage deployed in the sea. Depending on the treatment, some of the fish in each batch, in particular weak or sick fish, may not survive the handling or treatment. Others may be significantly weakened, with no or very little active swimming activity after treatment and will eventually die. Due to efficiency in the process, these dead or affected fish will in many cases be pumped to the net cage after treatment with the other fish and released there.

After release, the dead fish or weakened/harmed/sick fish that do not actively swim, will sink down to the bottom of the cage, where they can be collected and sucked up. As a typical sea cage may have a depth of 35 meter or more, the sinking of these fish may take considerable time. During the sinking these fish are typically spread in the whole cage area and bottom area and their collection is difficult.

Furthermore, the non-swimming fish may be transported to the cage walls with the water current with the risk of entanglement in the net walls. Dead fish in the cage over longer periods may represent a problem for the fish welfare and health as well as the water quality and may affect the fish quality.

Furthermore, it is desirable to slaughter/put to death harmed, sick and weakened fish quickly and thus to reduce the time of potential suffering to a minimum.

Thus, it is an objective of the present invention to solve one or more of the problems described above. In particular, the present inventions aims at solving the problem to remove/sort out dead and weakened fish efficiently during or right after release of a fish batch into a fish cage.

The objects are obtained by a device and a method as further defined by the independent claim, while preferred embodiments, variants, or alternatives are defined by the dependent claims.

Summary of the invention

Thus in a first aspect, the present invention relates to a device for separating non-swimming, weak, or dead fish from actively swimming fish after transfer to a sea cage through a release inlet. The device comprises

- a conical collection plate with a downwards oriented cone; the collection plate further comprises an outlet in the cone;

- a suction pipe connected to the outlet. The device further comprises suspension elements whereby the collection plate is suspendable in an upper part of the cage below the release inlet for fish.

The advantage of this arrangement is that dead and non-swimming, weakened or sick fish will typically sink down on the collection plate and will not be spread in the whole cage. The conical shape with a suction pipe in the center of the cone allows that fish are collected and concentrated in the cone and can be pumped up. Thereby their retaining time in the cage can considerably be shortened, as they can be quickly collected and removed from the cage for further handling. This is beneficial for fish welfare, quality, and health and reduces unnecessary suffering of the weakened fish. Moreover, the pumping distance of fish is considerable reduced compared to when pumped up from the bottom of the net cage.

In a preferred embodiment, the device further comprises a guiding tube vertically arranged between the release inlet and the collection plate, whereby - a gap is left between the lower end of the tube and the collection plate and/or - the tube is provided with at least one aperture

suitable for actively swimming fish to leave the tube.

The guiding tube is open at the bottom and has an opening for the release inlet for fish in the top of the tube, alternatively at a side of the tube in the upper region of the tube. The guiding tube is thus typically shaped as a skirt, which is opened at the top and at the bottom such that the fish can be released into the guiding tube at the top and leave the tube at the bottom or in the bottom area. The guiding tube is arranged above the collection plate leaving a gap between the lower end of the guiding tube and the collection plate, which is large enough that actively swimming fish can swim out to spread to other areas of the cage. Alternatively or in addition to a gap, the tube can have one or more apertures, where the actively swimming fish can swim out of the tube. The guiding tube has the advantage that dead and weak fish will be guided down to the collection plate and are not spread in the whole cage e.g. by tidal currents passing through the open net system of a cage. Thus, the collection of dead or weak fish is improved and a spreading of the fish by current is avoided while actively swimming fish can easily leave this part of the cage and enter the other parts of the cage.

Preferably, the at least one aperture is arranged in the lower part of the tube. Also preferred is a tube where the at least one aperture is an axial slit. This slit can be a vertical or horizontal slit along parts or the whole tube.

Preferably, the device further comprises a floating element arrangeable in the water surface above the collection plate wherein the suspension means are used for suspending of the collection plate and/or the guiding tube from the floating element.

The advantage of this arrangement is that the used elements (floating element, collection plate and/or guiding tube) are not integrated with other parts and installations of the net cage. Thus, they can be easily deployed during a fish release operation and can be removed when no longer needed. Thereby, additional permanent equipment in the cage is avoided and the risk of interference with other installations in the cage is reduced.

The diameter of the collection plate is preferably larger than the diameter of the guiding tube. It is an advantage if the collection plate is larger in its horizontal extension than the tube arranged above to avoid that sinking fish sideways pass the plate when sinking downwards without being collected. Taking into account some current, the size of the plate in relation to the tube should be chosen to have a low risk of sinking fish passing the plate on the side.

The floating element can be a floating collar, preferably a ring-formed floating collar. A floating collar has the advantage that it is open at the top such that the release inlet can be arranged above or inserted through the open center part of the collar.

It is further preferred that the guiding tube extends 3-7 meter downwards from the water surface. The guiding tube can be made of a material selected from net with apertures, a woven or non-woven fabric, tarpaulin or a combination thereof. If made of a net, a small mesh size is an advantage, as this will reduce the current and the risk of entanglement of the sinking fish with the net.

The diameter of the tube is preferably in the range of 3-7 meters. The diameter of the collection plate at least resembles the diameter of the tube but is preferably larger than the tube. These dimensions are preferred as they allow an easy and effective handling, deployment and removal, as well as that they are suitable for a typical release operation in open sea cages. However, larger or smaller dimensions can be used as well.

In another preferred embodiment, the collection plate is arranged at least 1 meter below the lower end of the guiding tube. A preferred distance between tube and plate is between 1 and 3 meters.

In a further aspect, the present invention relates to a method for separating non-swimming, weak or dead fish from actively swimming fish after transfer to a sea cage through a release inlet, the method using a device according to any of the preceding paragraphs. The method comprises the following steps

- suspending the collection plate horizontally in the upper part of the cage below the release inlet for fish,

- releasing of fish from the release inlet,

- collecting non-swimming, weak or dead fish on the collection plate

- pumping out collected fish through the outlet and suction pipe.

In yet a further aspect the present invention relates to a use of a device according to any preceding paragraphs for separating non-swimming, weak or dead fish from actively swimming fish after the fish was transported, handled and/or treated. Particularly preferred is a use after a delousing treatment of salmonids.

The advantage of this method and the device according to the present invention is that fish can be collected already in the upper water layers and do not need to sink the whole distance down to the bottom. They can be collected in a concentrated way and sucked up more or less instantly after release from the inlet release pipe. Thus, the pumping distance is short and less energy consuming. In addition, the retention time in the cage is short and therefor beneficial for fish welfare and quality. The present invention makes use of the differences in swimming activity between sick/weak fish, and healthy fish. Healthy fish will swim out of the tube, while dead, sick, and weak fish are often immobile and will sink down.

Description of the diagram(s)

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

Figure 1 shows schematically a cross section of the device for sorting out dead and weak/sick fish according to the present invention when deployed in a net cage.

Figure 2 shows a schematically top view of a device of figure 1 when deployed in a cage.

Description of preferred embodiments of the invention

The following description of the exemplary embodiment refers to the accompanying drawing. 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 sea based fish net pen cage as typically used in salmon production in the sea. It should be appreciated, however, that the referenced device and method are also applicable and suitable for use in respect to other types of cages such as e.g. enclosed cages without free water exchange through a net.

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.

In the description relative terms such as below, above, under, top, bottom, horizontally, vertically, side, downwards, upwards, etc. are all related to the device when in deployed stage and arranged in the cage for use. Furthermore, in the following description, certain elements and parts may only be exemplified and described for one side of the device. Even though only exemplified for one side, it is to be understood that the features may correspondently also apply for the opposite side of the device.

By “upper part of the net cage” is meant that the device is arranged a distance above the bottom of the net cage and not on or close to the bottom of the cage. Preferably, this will be close to the water surface, e.g. in the upper 5-15 meters in the water column, more preferred about 3-12 meters from the water surface.

By horizontally suspension of a conical collection plate is meant that the plate in its main extension is oriented horizontally in the water column. The center of the cone is thereby pointing downwards to the bottom of the cage.

Figure 1 shows in a cross sectional view a net cage 2 for farming of fish and a device 1 according to the present invention, whereby the device 1 is suspended in the upper part of the net cage 2. The shown dimensions of elements in figure 1 in relation to each other may differ in reality e.g. the size of the net pen and the device 1 in relation to each other.

The shown device 1 comprises a conical collection plate 10 having an outlet 12. The outlet is connected to a suction pipe 14 for pumping up dead or nonswimming fish 5 sunken and collected in the cone of the collection plate 10, whereby the lowest point of the plate in suspended stage is the center of the cone, which is pointing down towards the bottom of the net cage. The outlet 12 for fish into the suction pipe 14 is typically arranged at the lowest point of the cone. The suction pipe 14 is connected to a pump system, e.g. a mammoth pump, for pumping up the collected fish for further handling/slaughtering/destruction (not shown). Pump systems for lifting up dead fish are well known to the skilled person and are therefore not described in more detail.

The collection plate 10 is suspended from a floating element 20 by means of suspension elements 16. The suspension elements 16 may be ropes, wires, chains, or the like. The collection plate 10 is preferably arranged about 5-15 meters below the water surface 7 in a typical net cage having a total depth of about 35 meters from the water surface 7. More preferred the plate 10 is arranged about 4 -10 meters below the water surface.

The collection plate 10 can be made of a material suitable to be installed in water such as a composite material, fibre glass, carbon, metal or a combination thereof. The collection plate 10 can be circular in its circumferential shape but may also have other shapes such as rectangular, orthogonal, hexagonal, ellipsoid, oval etc. A preferred circular collection plate 10 has a diameter of 5-10 meters, more preferred between 3-7 meters.

Preferably, the collection plate 10 is made of a rigid material. The collection plate 10 can also be made of a flexible material such as a mesh, a woven or nonwoven fabric or tarpaulin. Preferably, such flexible material is combined with suitable reinforcement elements for a better form and shape stability.

The collection plate 10 should have an inherent negative buoyancy or have attached or integrated one or more weights for the same purpose. It is kept in its position by means of the suspensions elements 16 and the floating element 20 at the water surface 7.

The floating element 20 can be in form of a float. Typically, the float has a central opening for release of fish to the cage through a release inlet 4. In a preferred embodiment, the floating element 20 is a floating collar. Preferably, the floating collar is in form of a ring allowing to release the fish in the center of the ring. Typically, the collar can be a composite tube e.g. made of PVC. The collar tube can be filled with air or with a suitable lightweight material such as polystyrene / expanded polyester providing positive buoyancy. It can be sewed, welded, extruded or the like. The positive buoyancy should be dimensioned to support at least the weight of the suspended equipment from the floating element.

The floating collar is preferably made of a non-ridged, flexible material. One advantage of this is a facilitated handling, transport, cleaning, and storage compared to a rigid floating element. Preferably, the collar can be compressed when not in use for storage and transport purposes.

In an alternative embodiment (not shown) the collection plate 10 can be directly suspended by the suspension elements from suitable members of the net cage such as from a floating ring 8 arranged at the water surface in the circumference of the net cage 2.

In the shown embodiment, the device 1 further comprises a guiding tube 30, deployed from the floating element 20 and extending a distance downwards in the water column. The guiding tube 30 is centrally arranged above the collection plate 10 such that sinking fish released through the guiding tube 30 are guided downwards through the tube 30 onto the plate 10 for collection.

The guiding tube 30 can be circular in shape and is typically in form of a skirt, which is open at the top 34 and bottom 32. The guiding tube 30 can typically be made of a flexible material such as a mesh netting, woven or non-woven fabric or tarpaulin. In case of a net, the mesh size should preferably be fine meshed to reduce the water current through the skirt and to avoid the risk of entanglement of fish in the net.

Preferably, the guiding tube 30 is suspended by the same suspension elements 16 as the collection plate 10. Thereby, the weight of the collection plate 10 contributes to keep the guiding tube 30 in a downwards stretched stage.

Alternatively, the guiding tube 30 and the collection plate 10 can be suspended by non-common, individual suspension elements. In this case, the guiding tube is provided with weights to keep it in stretched stage. The use of weights in combination with skirts used in aquaculture, such as lice skirts, are well known to the skilled person and will therefore not be described in detail.

The guiding tube 30 has typically a length of about 5 to 10 meters, preferably 3 to 7 meters. The diameter of the tube 30 may be equal or preferably smaller than the diameter of the collection plate 10. Thereby, sinking fish 5 are directed onto the plate 10 and the risk that they miss the plate 10 in its periphery is reduced.

The skilled person would understand that also other dimensions for the tube and plate could be used. Thus, the dimensions of the tube 30 and plate 10 applied may be varied and adapted according to a particular cage size, number of fish to be inserted and the water current at a location. As long as the diameter resembles or covers at least the diameter of the tube walls or is preferably larger than the tube, an effective collection of sinking fish is achieved.

The distance between the collection plate and guiding tube may be varied with the current at a given location. In case of a high water current, it is preferred that the distance between the collection plate 10 and the lower end 32 of the tube 30 is reduced to avoid sinking fish to pass the plate 10 at its outer edge 11. At low water current, the distance can be higher, since the fish will sink more or less straight downwards. Said distance can be adjusted by means of the suspension means 16 for the tube 30 and/or plate 10. The successful collection of fish can be monitored by use of a suitable sensor such as one or more cameras monitoring the collection of fish on the plate during the release as well as optionally cameras for monitoring the swimming pattern of the active swimming fish. Said cameras e.g. a fish eye camera or other suitable sensors for monitoring (e.g. ultrasound, laser) sending signals to an operator/receiver, may be integrated in the device, attached to the device or suspended together with the device. The operator can then make the necessary adjustments manually. Alternatively, the device may be adjusted in an automated way. The collected fish may additionally be counted by a suitable fish counter during or after the pumping e.g. on board of a fish carrier.

The guiding tube 30 may also have an inlet opening for sideways introduction of released fish on the tube’s side under the water surface (not shown).

There is a gap between the lower end 32 of the tube 30 and the upper end/edge 11 of the collection plate 10 indicated by the arrow “A” in figure 1. This gap is necessary to allow swimming fish 6 to leave the area of the tube 30 and the gap area between the tube 30 and the collection plate 10 in order to enter other parts of the cage 2. This gap is typically about 1-3 meters in height and extends around parts or the whole circumference of the tube 30.

In another, not shown embodiment, the tube 30 may extend wholly or in parts down to the collection plate 20. If extending down to the collection plate, the tube 30 will be provided with large apertures in its lower part where through actively swimming fish 6 can leave the tube 30.

Figure 2 shows an embodiment of the present invention in a top view. The floating collar 20 is in the shown embodiment moored to elements of the surrounding net cage 2 such as the net cage floating ring 8 by four suitable mooring means 18 such as ropes, chains, or wires. In the shown embodiment of figure 2, the device 1 is moored in the periphery of the circular cage. A release inlet 4 from a boat or float 3 is arranged to release fish into the device 1. Also shown is one end of the suction pipe 14 whereby dead/sunken fish can be pumped up to a barge or fish carrier 15 from the collection plate 10. The float/barge 3 for release and barge/float 15 to collect fish after pumping them up from the collection plate, may be the same float or barge.

Preferably, the floating element 20 in form of a collar, is provided in a ring form having flexibility that allows that the circumferential shape of said collar can be altered depending on the use. In a preferred embodiment, the shape of the flexible collar after deployment can be altered by means of the mooring means 18 extending to the surrounding cage 2. This has the advantage that the collar with the attached elements can be easily moved and that the collar, as well as the optionally flexible tube suspended from the collar, can be adjusted in shape after suspension in the fish cage 2 depending on where and how the fish is released into the cage 2. For example, if fish are quickly released in high numbers through a large channel or pipe as release inlet 4, the collar and tube 30 may be adjusted in shape such as to a more oval form giving space to fish and to avoid that fish collide with the collar or tube by providing more space right in front of the release inlet 4. The flexibility in shapes and forms of the tube/collar affords a collection plate, which is large enough to ascertain that sinking fish do not accidentally pass the plate on its outer edge 11 if the collar and tube are e.g. moored to be oval in circumference.

The adjustability of the collar and tube shape by mooring means 18 allows a more flexible application of the device compared to a rigid system. However, also a rigid system of different shapes maybe used depending on the desired application and mode of release.

The above-described device allows an efficient separation of active swimming fish 6 from weak, immobile, or dead fish 5. A method for separating out nonswimming or dead fish 5 from actively swimming fish 6 after transfer to a sea cage 2 comprises a device 1 as disclosed with a conical collection plate with an outlet in the cone of the plate and a suction pipe connected to the outlet, the plate being horizontally suspended in the upper water layers of the sea cage 2. The method typically comprises the following steps

- suspending the collection plate 10 horizontally in the upper part of the cage 2 below an release inlet for fish, the collection plate covering a section of the cage 2 area, - releasing of fish from the release inlet 4,

- collecting non-swimming, sinking fish 5 on the collection plate,

- sucking out collected fish 5 through the outlet 12 and suction pipe 14.

In a preferred method, the device further comprises a guiding tube 30 for guiding downwards the sinking fish on the collection plate 10.

The device and method can e.g. be used after a delousing treatment of fish in a fish carrier/barge. Such treated fish will typically be transferred back to the cage 2 after the treatment. By means of the present invention, weak, sick and dead fish can be sorted out and removed directly after the release.

The described device is flexible and removable when not in use. The device according to the present invention is easy to suspend and to remove from the cage to avoid unnecessary equipment in the cage 2. This can e.g. be done by a common crane, either installed on a fish carrier or on site on the fish cage/farm, the crane arm lifting up the device when not in use and setting it out when needed. The device is not as such integrated with the net cage and thus easy to install and to remove.

Claims (1)

1. Patent claims

   1. Device (1) for separating non-swimming, weak, or dead fish from actively swimming fish after transfer to a sea cage (2) through a release inlet (4), wherein the device (1) comprises

   - a conical collection plate (10) with a downwards oriented cone; the collection plate further comprises an outlet (12) in the cone;

   - a suction pipe (14) connected to the outlet (12),

   characterized in that the device (1) further comprises suspension elements (16) whereby the collection plate (10) is suspendable in an upper part of the cage (2) below the release inlet (4) for fish.

   2. Device (1) according to claim 1, wherein the device (1) further comprises a guiding tube (30) vertically arrangeable between the release inlet (4) and the collection plate (20), whereby

   - a gap is left between the lower end of the tube and the collection plate (20) and/or - the tube is provided with at least one aperture

   suitable for actively swimming fish to leave the tube.

   3. Device according to claim 2, wherein the at least one aperture is arranged in the lower part of the tube.

   4. Device according to claim 2 or 3, wherein the at least one aperture is an axial slit.

   5. Device (1) according any of the preceding claims, wherein the device (1) further comprises a floating element (20) arrangeable in the water surface above the collection plate (10) wherein the suspension means (16) are used for suspending of the collection plate (20) and/or the guiding tube (30) from the floating element (20).

   6. Device (1) according to claim 3, wherein the diameter of the collection plate (10) is larger than the diameter of the guiding tube (30).

   7. Device (1) according to any of the preceding claims, wherein the floating element (20) is a floating collar, preferably a ring-formed flexible or rigid floating collar.

   8. Device (1) according to any of the preceding claims, wherein the guiding tube (30) is made of a material selected from the group consisting of a net, a woven or non-woven fabric, tarpaulin, or a combination thereof.

   10. Device (1) according to any of the preceding claims, wherein the collection plate (10) is arranged at least 1 meter below the lower end of the guiding tube (30).

   11. Method for separating non-swimming, weak or dead fish from actively swimming fish after transfer to a sea cage (2) through a release inlet (4), the method using a device according to any of the claims 1-10 characterized by the following steps

   - suspending the collection plate (10) horizontally in the upper part of the cage (2) below the release inlet (4) for fish,

   - releasing of fish from the release inlet (4),

   - collecting non-swimming, weak or dead fish on the collection plate (10)

   - pumping out collected fish through the outlet (12) and suction pipe (14).

   12. Use of a device according to any of the claims 1-10 for separating nonswimming, weak or dead fish from actively swimming fish after the fish was transported, handled and/or treated and released to a fish cage (2).

   13. Use according to claim 12, wherein the treatment is delousing.