Floating, liftable and movable sorting cage for sorting organisms from aquaculture cages

Abstract

A floating sorting cage 1 for sorting organisms from an aquaculture cage, having a floating unit 6 with at least three lifting points 7, with the floating unit 6 extending at least partially around an

Description

Technical field The invention relates to breeding of organisms in a cage in a body of water. More specifically, the invention relates to a floating sorting cage for extracting unwanted fish from a fish cage Background Today, the aquaculture industry uses an ordinary handheld fish net (also called ‘fish landing net’) to remove fish from aquaculture cages / fish cages that do not meet welfare requirements from fish cages (injured fish, sick fish, etc.). The sick or injured fish commonly pulls out of a school of fish in the center of the fish cage and is usually found along the net wall in the fish cage. An operator uses a handheld net to catch the fish that do not meet the welfare requirements, lifts them out of the cage and bring them back to a work boat by walking along the walkway on the fish cage. Often there are a lot of fish that must be removed from the fish cage. The workboat must be accessible during fish handling for receiving the unwanted fish This entails large workload on the operators walking back and forth on the walkway with a handheld fish net. Low efficiency due to a lot of walking and restricting the freedom of the work boat to do other tasks. There is also a risk of escape as the fish can jump out of the handheld net and into the sea. Sick and injured fish in the fish cage represents increased risk of diseases developing among healthy fish. Removing sick and injured fish from the fish cage reduces biological risks dramatically. The aquaculture industry needs an efficient way to remove fish or organisms not meeting the welfare standards from the fish cage. Summary of invention In a first aspect of the invention a moveable floating sorting cage for sorting out organisms from an aquaculture cage is described. The sorting cage includes a floating unit and at least three lifting points distributed around the floating unit. The floating unit extends at least partially around an upward-facing entrance opening for throwing sorted organisms from the aquaculture cage into the sorting cage, and a main net fixed to the floating unit wherein the main net comprises a discharge opening at a lower end of the main net. The sorting cage further comprises closing means to open and close the discharge opening. The main net may comprise an upper net shaped like a frustum of a cone and a more cylindrical lower net shaped like a cylinder or a frustum of a cone with a smaller angle between sides of the frustum and a vertical direction as compared to the upper net. The sorting cage may comprise a weight unit positioned in a lower half of the main net to keep the sorting cage taut. The weight unit may comprise a lead rope. The sorting cage may comprise a support ring in the lower half of the main net to keep the sorting cage taut. The closing means may comprise a closing rope which closes the discharge opening. The sorting cage may comprise a directional net attached to the main net at the discharge opening to dampen the fall of the sorted organisms and to provide increased directionality to the stream of fish. The sorting cage may comprise a lifting line attached to each of the at least three lifting points wherein all the lifting lines are connected to a lifting eye. The lifting eye may be connected to a lifting eye line (10) which is connected to a towing line, which in turn is connected to the floating unit. The floating ring may comprise a stiffening structure, which can keep the sorting cage extended when the sorting cage is lifted by the lifting eye. Short description of drawings To help understanding the invention the following drawings are supplied. The same reference number in different drawings refer to the same feature. Fig. 1 shows an embodiment of a sorting cage. Fig. 2 shows an embodiment of a sorting cage comprising an upper and lower net with a directional net attached to the discharge opening. Fig. 3a and b shows a rectangular and triangular embodiment of a floating unit. Fig. 4a and b shows a cylindrical and conical embodiment of a main net respectively. Detailed description In this text, we describe a sorting cage as if it was floating in water. That is, with a floating ring at the top and a discharge opening at the bottom. The sorting cage is intended to be dragged around the outer wall of a fish cage by an operator to select unwanted organisms or fish that should not be there for one reason or another, usually sick or injured fish. The operator can remove the selected organism / fish with e.g. a handheld fish net and drop the selected fish into the sorting cage and then continue along the edge of the fish cage until a full round is completed or the sorting cage is full and the sorting cage is brought to an emptying point. In most cases this would be a work boat having a crane and a fish tank or some kind of container for storing the fish until the fish is sent for destruction or further processing. As seen in fig. 1 the sorting cage 1 for sorting out organisms from a cage comprises a floating unit 6 around an upward-facing entrance opening 18 for throwing sorted organisms from the fish cage into the sorting cage 1. The floating unit 6 does not have to be round, but can have different shapes such as triangular, rectangular as seen in fig. 3a and b, also shapes like round or oval are possible. The sorting cage 1 further comprises a main net 3 fixed to the floating ring 2, where the main net 5 comprises a discharge opening 19 at a lower end of the main net 5 as indicated in fig. 2. The main net 5 can have many shapes such as cylindrical as seen in fig. 4a, rectangular as seen in fig. 3a, triangular as seen in fig. 3b, frustoconical as seen in fig. 1 or 4b, or the main net can have other shapes. However, the shape of the main net must fit the floating ring 2. The sorting cage includes closing means 5 to open and close a discharge opening 19 as indicated in all of the figures. The discharge opening 19 must be able to be closed to keep the organisms / fish in the sorting cage 1 during sorting and lifting of the sorting cage 1 and the closing means 2 must be able to open the discharge opening 19 when the sorting cage is lifted up and located above the point where the organisms / fish should be discharged. This will typically be a fish container or fish tank on board a work boat. In one embodiment, the discharge opening 19 is a round opening with a plurality of closing eyes 17 around the edge where a closing rope 15 passes through the closing eyes 17 to close and open the discharge opening 19 by tightening the rope and tying it, and by loosening the rope and letting the rope out respectively. That is, the closing rope 15 closes and opens the discharge opening 19. As seen in fig. 1, the sorting cage 1 includes at least three lifting points 7 distributed around the floating ring to enable a lift where the weight is distributed among the lifting points. The lifting points 7 can comprise lifting rings 7 in which further lifting means can be attached. Fig. 2 shows an embodiment of the main net comprise an upper net 12 shaped like a frustum of a cone and a cylindrical lower net 13 which is more cylindrical in shape. This puts less pressure on the organism / fish at the bottom of the net if it is only to be transported and not slaughtered and also makes the release of the fish more controllable with respect to damage and directionality because not all of the fish is released and dropped at the same time. The lower net 13 may also be formed as a frustum with a smaller angle with a vertical line compared to the upper net 12. In an embodiment, the sorting cage comprises a support ring 20 in the lower half of the main net 3 to keep the sorting cage taut. This prevents the fish from becoming entangled in the net. In an advantageous embodiment, the support ring 20 is fixed between the upper net 7 and the lower net 8. The support ring can also be made of metal and thus form the weight unit 3. In an embodiment, the sorting cage comprises a directional net 14 which is attached to the main net 5 at the discharge opening 4 to dampen the fall of the sorted organisms when the discharge opening is opened and also improve directionality of the released stream of fish discharged from the sorting cage 1. The directional net 14 can be a cylindrical fine-mesh net which is attached to the discharge opening 19 and extends a distance downwards. The shape of the sorting cage 1 in fig. 2 reduces splatter from the discharge operation because of a more controlled release of the fish, thus reducing contaminated water or fish touching the deck or equipment. In an embodiment, the sorting cage comprises a lifting line 8 for each of the at least three lifting points 7 and are all connected to a lifting eye 9 which can lift the entire sorting cage 1 when it is filled with organisms / fish. In a standard salmon fish cage that is used along the Norwegian coast today, 10-30 fish will typically be picked out each day, which must either be treated or killed / destroyed. This volume should be able to be accommodated in the sorting cage 1 to achieve maximum efficiency gain. A floating ring 2 with a diameter of between 0.8 and 1.5 meters and a main net 5 with a depth of 1-2 meters will produce a sorting cage 1 that can be easily handled by one operator and that has enough volume to pick out all the fish that should be taken out in one round around the fish cage perimeter. The sorting cage 1 should also be manageable by one operator when it is fully loaded in the fish cage and must be towed towards lifting equipment. In an embodiment, shown in fig. 2, where gentle treatment of fish to be processed and / or moved is also taken into account, the sorting cage may include a floating ring of approx. 1.2 meters in diameter and a frustoconical upper net 7 with a depth of 0.9 meters and where the lower diameter is 0.8 meters. The sorting cage may further comprise a lower net 8 which is cylindrically shaped with a diameter of 0.8 meters and a depth of 0.4 meters. The sorting cage may comprise a fine-mesh directional net 14 attached below the discharge opening 19 extending a distance below the discharge opening 19, for instance 30-50 cm below the discharge opening. For the operator to be able to tow the sorting cage with him, the floating unit 6 is connected to a towing device 11, for example a towing line 11 as seen in fig. 1. The towing device makes it easy to tow the sorting cage 1 along the perimeter of the fish cage when walking on the walkway of the fish cage. Also, the lifting eye 9 should be attached to the towing rope, by means of a lifting eye rope 10 as seen in fig. 1. This configuration will make it possible for the operator to pull the lifting eye 9 in order to hook the lifting eye on a lifting device. In order to increase stability and reduce discomfort for the fish (if not slaughtered), the floating ring 2 in one embodiment comprises a stiffening structure 17 (visible in fig. 4b) that can hold the sorting cage 1 extended when the sorting cage is lifted by the lifting eye 13. The sorting cage can be operated by one operator. The method for use comprises catching selected fish / organisms with a handheld net, or other catching means. The operator then put the content of the handheld net into the sorting cage and proceed along the walkway or along the perimeter of the fish cage / aquaculture cage to find more fish / organisms that needs to be removed from the cage while dragging the sorting cage 1 behind him / her. When the sorting cage is full or a round of the aquaculture cage has been completed the sorting cage can be lifted out of the cage using a crane. The sorting cage with contents may then be placed in a vessel for euthanasia with anesthetic liquid or be emptied into another vessel for destruction. The process can be repeated if necessary. The sorting cage can be used without the workboat being at the aquaculture cage. The sorting cage containing the selected fish can be attached to the handrail or suitable features while waiting for the work boat to arrive. This results in greater flexibility and efficient utilization of the work boat and crew on site. Thus, the sorting cage will reduce the physical strain on the crew. The floating net 1 will reduce the risk of escape since the net is lifted out of the cage by the workboat and a safety net is used between the cage and the workboat. References 1 Sorting cage 2 Closing means 3 Lead rope I Weight unit 4 Strengthening line 5 Main net 6 Floating unit / Floating ring 7 Lifting point I Lifting ring 8 Lifting line 9 Lifting eye 10 Lifting eye rope 11 Towing line 12 Upper net 13 Lower net 14 Directional net 15 Closing rope 16 Closing eyes 17 Stiffening structure 18 Entrance opening 19 Discharge opening 20 Support ring

Claims

1. A floating sorting cage (1) for sorting out organisms from an aquaculture cage includes:a floating unit (2),at least three lifting points (7) distributed around the floating unit (2),wherein the floating unit (2) extends at least partially around an upward-facing entrance opening (18) for throwing sorted organisms from the aquaculture cage into the sorting cage (1),a main net (5) fixed to the floating unit (2) wherein the main net (5) comprises a discharge opening (19) at a lower end of the main net (5), andclosing means (2) to open and close the discharge opening (19).

2. A sorting cage (1) according to claim 1, wherein the main net (5) comprises an upper net (12) shaped like a frustum of a cone and a more cylindrical lower net (13) shaped like a cylinder or a frustum of a cone with a smaller angle between sides of the frustum and a vertical direction.

3. A sorting cage according to claim 1 or 2, wherein a weight unit (3) is positioned in a lower half of the main net (5) to keep the sorting cage (1) taut.

4. A sorting cage according to claim 3, wherein the weight unit (3) comprises a lead rope (3).

5. A sorting cage according to any one of the preceding claims comprising a support ring (20) in the lower half of the main net (5) to keep the sorting cage taut.

6. A sorting cage according to any of the preceding claims, where the closing means (2) comprise a closing rope (15) which closes the discharge opening (19).

7. A sorting cage according to any one of the preceding claims, wherein a directional net (14) is attached to the main net (5) at the discharge opening (19) to dampen the fall of the sorted organisms.

8. A sorting cage according to any of the preceding claims, wherein a lifting line (8) is attached to each of the at least three lifting points (7) and is all connected to a lifting eye (9).

9. A sorting cage according to claim 8, wherein the lifting eye (9) is connected to a lifting eye line (10) which is connected to a towing line (11), which in turn is connected to the floating unit.

10. A sorting cage according to claim 8 or 9, wherein the floating ring (2) comprises a stiffening structure (17), which can keep the sorting cage (1) extended when the sorting cage is lifted by the lifting eye (9).

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