WO2002028169A2

WO2002028169A2 - A sorting device for sorting marine species in a fishing trawl

Info

Publication number: WO2002028169A2
Application number: PCT/IS2001/000019
Authority: WO
Inventors: Edgar Gudmundsson
Original assignee: MARSEL EHF
Current assignee: MARSEL EHF
Priority date: 2000-10-04
Filing date: 2001-10-04
Publication date: 2002-04-11
Anticipated expiration: 2003-04-04
Also published as: NO20031493L; EP1324653A2; AU2001290223A1; IS6768A; NO20031493D0; WO2002028169A3

Abstract

The present invention relates to a device for sorting fish and similar marine species during the catch in a fishing trawl. More specifically the invention relates to a device comprising a sorting grid that allows species of certain predetermined sizes to enter through openings into sorting bags of the fishing trawl. The device is to be attached to the fishing trawl and to be used submerged in water, during the catch.

Description

A SORTING DEVICE FOR SORTING MARINE SPECIES IN A FISHING TRAWL

Field of the Invention

The present invention relates to a device for sorting fish and similar marine species during the catch in a fishing trawl.

Description of the Prior Art

Devices for sorting fish during the catch exist. In general, the devices comprise sorting grids, typically made from steel. During the. catch, the fish is forced to enter through one of more openings in the grid, whereby the fish ends in a bag respective of the size of the fish or whereby the fish escapes from the bag e.g. in order to preserve the population of species threatened with extinction.

Usually the sorting grid is made from a number of steel bars arranged side by side in a frame, the frame being inserted into the fishing net in a side of the net and parallel to the net.

In order to preserve the population of certain marine species, it is often desired to sort out both specimens that are very small and specimens that are very large, such as the spawning females. Presently it is possible to select sort out fish under a certain size to escape from the net or to sort out fish over a certain size to escape from the net. It is however not possible to select both fish under a certain size and fish over a certain size to escape the net.

As a fish is forced through the rough steel bar grid, it easily happens that it blocks the grid or that it is injured either by the pressure from the grid or from the frictional resistance between the grid and the fish. This is an undesired effect, resulting in a lower quality of the catch. As the fish is taken onboard the ship in one big net or maybe partitioned into a few bags of the net, it usually happens that a large part of the fish is killed or even destroyed by the pressure of several hundred kilos of fish being lifted onboard in one big bag. Furthermore it happens that small fish escaping through the openings of the grid doesn't survive injuries from the pressure against the rough steel bars of the grid. This is obviously in contrast to the objects of sorting out small species of the catch.

Description of the Invention

It is an object of the present invention to provide a method and a system that will allow for sorting fish and other marine species in the net during the catch and without destroying the fish. It is also an object of the invention to enable marine species of selected sizes - small or large - to be sorted out of the net or to be partitioned into different areas of the net depending upon their size.

Accordingly the present invention relates to a sorting device for sorting marine species in a fishing trawl, said device comprising:

■ a supporting means with an inlet and at least a first and a second outlet,

■ a passage extending in a flow direction from the inlet towards the outlets, and

^■ at least one roller, the roller being rotationally arranged transverse to the flow direction of the passage, so as to provide at least a first and a second opening through the passage, the first and the second opening having different cross sectional areas so as to restrict the passage of marine species depending upon their size,

wherein the first opening is connected to the first outlet and the second opening is connected to the second outlet.

In one embodiment the first outlet is connected to a first collecting bag of the fishing trawl and wherein the second outlet is connected to a second collecting bag of the fishing trawl. The rollers may be arranged in a unit, which can be a rectangular frame. The frame can be composed of subunits, for allowing an displacement in the (x,y,z) direction. In one preferred embodiment the frame is simply the fishing net and wherein the roller units may be fasten directly to the fishing net. Accordingly, the flexibility of the roller unit is of importance. In another embodiment the supporting means is a frame with any shape such as a box shape.

The frame could either be made from sheet metal or from bars e.g. metal bars or bars of a composite material. Preferably the box is shaped as a hollow frame with sides e.g. made from a net, so that the weight of the box is as low as possible. The passage is then provided counted from the towing direction, from the front end of the box to the rear end of the box, through a tunnel as defined between the four sides made from a net. The roller is provided across the passage so that marine species passing through the passage are forced to pass on one of the sides of the roller and thereby ends up in different areas of a fishing net placed after the sorting device, again counted in the towing direction. As an alternative more rollers are arranged so that the marine species are forced to pass either between the sides of the frame and one of the rollers or between two adjacent rollers. The distance between the rollers being relative to the desired sorting sizes.

The first outlet could be connected to a first collecting bag of the fishing trawl and the second outlet could be connected to a second collecting bag of the fishing trawl. As an alternative one of either the first of the second outlets could be connected to a passage out of the fishing net so as to let the fish out of the net.

According to a preferred embodiment of the invention the rollers are arranged in units. Each of the units may have a plurality of openings for sorting the marine species. As an example the units could be placed adjacent in the flow direction. The first unit could be adapted for sorting out all the small fish, letting the medium size fish into one passage through one outlet and the large fish into another passage through another outlet. An adjacent unit could then sort the large fish and let the very large - the spawning fish - out of the net and sort the remaining fish into different size categories. More units could then again sort the categories into more sub categories. Each of the final categories of sizes of fish could finally be taken onboard the fishing board in different bags of the fishing net. This is an advantage since the fish is then pre-sorted already during the catch, which eases the work to be done onboard the ship and the risk of destroying the fish in one big net is reduced.

Preferably the rollers are provided as hollow tubes with surfaces having an open structure so as to allow water to pass through the surfaces. As an example the rollers could be provided as rolls of steel net or as tubular rubber roam rolls. The outer surface of the rollers may be coated with a low frictional coating in order to reduce the frictional resistance between the rollers and the marine species or the rollers could be polished so as to provide a smooth surface.

The rollers are able to rotate as a fish goes through the gab between two adjacent rolls. However the rollers could even be provided with means for causing a forced rotation of the rollers. As an example, water turbine wheels with turbine vanes could be attached to one or more of the rollers for rotating the rollers when the water flows across or through the device. The turbine vanes could be comprised in the surfaces of the rollers. As an example the surface of the rollers could comprise a grid pattern made from vanes, arranged peripherally around the outer surface of the rollers. The stream of see passing through the rollers could also cause the rotation of the rollers. To prevent that marine species block the entrance between the rollers, it is important that the rotational speed of the rollers, if the rollers have the same radius, is the same. This can be achieved by providing the rollers with for example a sprocket wheel and a chain or similar means for transferring the rotation to the adjacent roller. This could also simultaneously be used as a supporting means for the roller unit frame to hold the subunits mentioned above together. This would be done by transferring the rotational speed from a first roller to a first and a second adjacent roller crosswise, so that on one end of the roller unit frame the transferring is from the first roller to the first adjacent roller on one side of the frame and from the first roller to the second adjacent roller on the other side of the frame. The rotation could also be effected by power driven means connected to at least one of the rollers. Such means could be electrically driven motors, hydraulically driven motors or the like. As an example, power driven means could be connected to one of the rollers and the rollers could then be interconnected by means for transferring rotation from one roller to another, e.g. by means of chains or gear wheels. Control means could be adapted so that the rotation speed of the rollers is adjustable, e.g. via a cable from the boat down to the bottom of the ocean.

According to a preferred embodiment of the invention the rollers could be provided with a circular cross sectional shape. The distance between the rollers and the radial size of the rollers would in that case determine the cross sectional area of the openings. By means of rollers with adjustable radial size the cross sectional area of the openings can be adjusted. By making the rollers from a flexible grid, the radial size of the rollers can be changed by twisting the rolls, e.g. by rotating the one end of a roll with another speed than the other end of the roll until the desired radial size and thus the desired cross sectional area has been reached. Preferably the device is provided with means for remotely operating the means changing the radial size of the rollers.

Peripheral equipment such as cameras for inspecting the sorting process or sensors for measuring the rotational speed of the rollers or the amount of fish in each of the bags may be attached to the frame.

Detailed description of the invention A preferred embodiment of the invention will now be described in details with reference to the drawing in which:

Fig. 1 shows a sorting device according to the present invention,

Fig. 2 shows the sorting device mounted in a fishing trawl being towed after a fishing boat, Fig. 3 shows a sorting device with a number of fish being sorted,

Fig. 4 shows another type of sorting device according to the present invention,

Fig. 5 shows cross sectional view of the sorting device from Fig. 4,

Fig. 6 shows a roller with turbine vanes and a chain wheel,

Fig. 7 and 8 shows roller units where the radius of the roller units can be varied,

Fig. 9 one turbine blade attached to a rotation axis and a cylindrical shaped housing,

Fig. 10 shows how the present invention can be used for fishing marine species such as shrimps and fish simultaneously,

Fig. 11a and 11 b shows one embodiment of how the radius of the roller can be varied,

Fig. 12a and 12b shows a flexible roller units,

Fig. 13 shows one embodiment of a cross-section of a roller, and

Fig. 14a-14c shows how small marine species can be sorted out from larger marine species.

Referring to Fig. 1 the sorting device has a frame 1 to be mounted in the opening of a fishing trawl. The frame has an inlet 2 and a number of outlets 3,4,5 defined by roller units 6,7,8 arranged across the passages from the inlet to the outlets. The frame is however not the essential feature in this embodiment. The roller units could as well be fasten directly to a fishing net. The frame has a lower surface provided with smoothly rounded corners 9, so that the frame easily slides over the seabed when being towed after a fishing boat. A plurality of rollers is arranged in the roller units. The distance between the rollers and the radial size of the rollers are selected to that fish or similar marine species of different size can pass through the openings between the rollers. Accordingly, the roller unit acts as a conveying means for the larger species and as a selector for the smaller species.

The frame of the sorting device could preferably be made from either steel or from a composite material such as carbon fibre reinforced epoxy it may even be made from pure plastic materials, or the roller units could simply be fastened directly to the fishing net. The rollers could be made from a flexible or resilient material such as rubber or from a rubber coated hard material. Preferably the rollers are made as a tubular grid, e.g. made from wire netting, so that seawater easily passes through the rollers. The outer surface of the roller could be coated with a low frictional coating such as Teflon. The rollers could also be made from a spongy material or be coated with a material such as foam rubber.

The rollers are attached to the frame through bearings so that they easily rotate. The rotation could be effected either by the water passing through or around the rollers as the frame is being pulled over the seabed or by one or more wheels attached to the frame and rolling over the seabed. It could also be effected by power driven means such as encapsulated electrically driven motors, hydraulically driven motors etc. It is important that the speed of the rollers is either the same or the growing increasingly with the conveying direction. This prevents that the marine species stick between the rollers. The speed of the rollers could also be adjustable.

Fig. 2 shows a situation where the sorting device, mounted in a fishing trawl, is being towed after a fishing boat 10. A large fishing net in front of the sorting device is in the front end stretched widely open between a number of rolling weights and a number of floating balloons. The sorting device may either be pulled directly by wires attached to the boat or it may be pulled by the net whereto it is attached. As indicated in Fig. 2 the sorting device

Fig. 3 shows a side view of the sorting device with fish being sorted. As it can be seen, the sorting device offers the possibility of sequentially sorting of the fish. As an example the small fish may be sorted out of the net in the first step, the large fish (spawning fish) may be sorted out in the next step and the remaining fish may be sorted into different bags of the net, in the last step. Due to the resiliency and rotation of the rollers, the pressure does not destroy the fish.

Figure 4 and 5 shows another embodiment of the roller, with a inlet 69, a first 70 and a second 73 guiding means for guiding the marine species that enters through the first roller unit toward the second roller unit and a first 71 and a second outlet 71.

Referring to Fig. 6 the rollers may be provided with sprocket wheels 14 for transferring the rotation between each of the rollers in a unit or even between more units, e.g. by means of chains or by directly engagement between the teeth of gears of two adjacent rollers. The turbine wheel 15 is adapted for effecting rotation of the rollers 17 as seawater flows across the turbine vanes 16.

Figure 7 shows another embodiment of the roller, wherein the roller comprises a rotation axis 18 and a cylindrical shaped housing 19 surrounding the rotation axis. Turbine blades are attached to the rotation axis 18 and the cylindrical shaped housing 19, the rotation axis and the cylindrical shaped housing defining a rotation axis of the roller. By varying the angular position of the rotation axis 18 in relation to the cylindrical shaped housing 19 the radius of the roller can be changed through a radial movement of the turbine blade 20 and therefore the radius 28 of the roller. In another embodiment the radius can be changed either by varying the rotation speed of the rotation axis or the cylindrical shaped housing until the roller has reached the desired diameter. Figure 8 shows a roller where the radius has been increased. Accordingly, by varying the radius, the size of the fish to be sorted can be controlled due to a change in distance between neighbouring rollers. In another embodiment each roller is divided into more than one rollers, wherein within the same roller the radius can be different due to a different due to a different angular position of the rotation axis 18 with respect to the cylindrical shaped housing 19.

Fig. 9 shows one turbine blade 20 with a first 22 and a second 21 fastening plate for attaching with the rotation axis 18 and the cylindrical shaped housing 19, which is also provided with a fastening plate. A bridge member 25 connects the first fastening plate 22 with the fastening plate on the rotation axis 24, while the second fastening plate 21 is attached directly to the fastening plate on the outer cylinder 23. All attachments are provided with a hinge or a similar means for allowing a rotation between the attachments. As the angular position between the rotation axis 18 and the cylindrical shaped housing 19 is changed the radius of the roller changes and therefore the angles α1 30 and β1 29 between the bridge member 25 and the first fastening plate 22 and the fastening plate on the rotation axis 24, and the angle γ 31 between the second fastening plate 21 and the fastening plate on the outer cylinder. This can be achieved in different ways.

One way of achieving this is if the angular position of the inner cylinder in relation to the outer cylinder is changed. The radial size may thus be adjusted by angular movement of one of the cylinders in relation to the other, for example by adjusting the angular position of the rotation axis 18. When the desired radial size has been reached, the two cylinders mutual angular position is locked so that the radial size of the roller stays fixed.

Another way is by changing the rotational speed of the rollers by varying the perpendicular force exerted by the see on the turbine blades. Varying the speed of the means that pulls the sorting device, i.e. typically a ship can for example vary this force. In another embodiment, the turbine blades are in a fixed position and therefore the radius as shown in Fig. 13 and Fig. 14c.

Fig. 10 shows one embodiment of the present invention, where marine species such as shrimps and fish 35 are being fished simultaneously. The first unit of rollers 37 is provided with an opening that let the shrimps into first area 38 while the remaining fish is displaced by the first unit rollers towards the third unit of rollers 42a, b. In the first area 38, two second units 39a, 39b are provided to select out all the small shrimps, which is subsequently released. This can be achieved by either changing the radius of the rollers in the units 39a and 39b so that the interval between the rollers is smaller compared to the first unit of rollers 37, or simply by applying more rollers per unit length compared to the first set of rollers 37, if we assume that the radius of each individual roller is the same. Accordingly, the remaining shrimp that are to large to enter between the rollers in 39a and 39b is collected into a collecting bag 40.

A similar procedure is applied on the fish that is too large to enter the first area 38. The small fish is selected out by the third unit of rollers 42a, 42b and released, while the remaining fish is collected into a collecting bag, which is kept separate from the shrimp collecting bag 40.

In one preferred embodiment the radius of the rollers can be changed as already mentioned. It is however essential that the circular symmetry of the roller is conserved. One solution to this is shown in Fig. 11a and 11b, where the turbine blade is provided with a thin rod with a circular shape 34 extending from the turbine blade to a plate 35 positioned parallel to the rotation axis at a radial distance close to the radial distance of the roller with a fixed interval. This interval corresponds at least to the height of the rod, and therefore allows an entrance of rods from nearby turbine blade. By combining a plurality of such turbine blades together a roller with variable diameter is formed as Fig. 11a shows. Fig. 12a and 12b show another preferred embodiment of roller units, which are flexible and divided into a plurality of units 50. Shown is a front view and a cross sectional view of the roller unit. The units are connected in such a way 56 that allows an displacement in (x,y,z) direction. The rotation between each of the rollers is transferred by means of for example chains or means that can transfer the rotation between two adjacent rollers 52. What is essential in this embodiment is that the transferring between two adjacent rollers is crosswise which can be understood from the cross sectional view of Fig. 12a. The transferring between two rollers is shown 52, by for example providing the rollers with sprocket wheels for transferring the rotation between each of the rollers in a unit or even between more units. However, the connection between the rollers shown in the cross-view 52 to the adjacent roller is provided on the other cross section of Fig. 12a (not shown). Accordingly, such arrangement both supports the roller unit with the plurality of rollers and also provides the roller unit 55 flexibility, which can be important when the roller unit is attached directly to a fishing-net. Figure 12b shows a displaced roller unit 55 round the angle alpha 53 and the angle beta 54.

In this embodiment the radius of the rollers can either be fixed or can be varied and the rotation of the rollers is provided through the see flow.

Figure 14a-14b shows a still another embodiment of two roller units fixed in a frame. This frame could also be a fishing net, wherein the first 59 and the second 60 roller unit is attached directly to the fishing net. In this embodiment the radius of the rollers is fixed (see Fig. 14c) and the pulling force from the ships insures the rotation of the rollers. As shown in Fig. 14b, the small fish enters through the first 59 and the second roller unit 60, and is released through the openings 61 , 62 and 65. Adjacent and under the first and the second roller units is a hindrance 63, 64 to sort out the small fish through said openings. The remaining fish that is larger then that corresponds to the interval between two rollers enters a fishing or collecting bag. This procedure could also be repeated again for further sorting.

Claims

1. A sorting device for sorting marine species in a fishing trawl, said device comprising:

^■ a supporting means with an inlet and at least a first and a second outlet,

^■ a passage extending in a direction of flow from the inlet towards the outlets, and

^■ at least one roller, the roller being rotationally arranged transverse to the flow direction through the passage, so as to provide at least a first and a second opening through the passage, the first and the second opening having different cross sectional areas so as to restrict the passage of marine species depending upon their size,

2. A sorting device according to claim 1 , wherein the first outlet is connected to a first collecting means of the fishing trawl and wherein the second outlet is connected to a second collecting means of the fishing trawl.

3. A sorting device according to claim 1 , wherein the rollers are arranged in units.

4. A sorting device according to claim 3, wherein the unit is a frame being flexible that allows an displacement in (x,y,z) direction.

5. A sorting device according to claim 1 , wherein the supporting means is fishing net.

6. A sorting device according to claim 1 , wherein the supporting means is a structural supporting frame.

7. A sorting device according to any of the preceding claims, wherein each unit is connected to respective outlets.

8. A sorting device according to any of the preceding claims, wherein the outlets are connected to respective collecting bags of the fishing trawl.

9. A sorting device according to any of the preceding claims, wherein more units of rollers are arranged subsequently in the flow direction and wherein each unit of rollers relate to a set of cross sectional areas of the pluralities of openings.

10. A sorting device according to any of the preceding claims, wherein the rollers are provided as hollow tubes with surfaces having an open structure so as to allow water to pass through the surfaces.

11. A sorting device according to any of the preceding claims, wherein the rollers are provided with means for causing a rotation of the rollers.

12. A sorting device according to any of the preceding claims, wherein the rollers are interconnected by means for transferring rotation from one roller to another.

13. A sorting device according to claim 12, wherein the transferring of rotation of a first roller to the two adjacent rollers is crosswise, so that on one end of the three rollers the transferring is from the first roller to a first adjacent roller and from the first roller to the second adjacent roller.

14. A sorting device according to any of the preceding claims, wherein the rollers have a fixed radius.

15. A sorting device according to any of the preceding claims, wherein the radius of the rollers is adjustable.

16. A sorting device according to claim 15, further comprising means for remotely operating the means for adjusting the radial size.

17. A sorting device according to any of the preceding claims, wherein the rotation speed of the rollers is the same.

18. A sorting device according to any of the preceding claims, wherein the means for causing a rotation comprises a water turbine wheel with turbine vanes, the rotation of the turbine wheel being caused by water flowing through/across the device.

19. A sorting device according to claim 18, wherein the turbine vanes are comprised in the surfaces of the rollers.

20. A sorting device according to claim 18 or 19, wherein the means for causing a rotation comprises power driven means connected to at least one of the rollers.

21. A sorting device according to any of the preceding claims, further comprising means for controlling the rotational speed of the rollers.

22. A sorting device according to any of the preceding claims, wherein the rollers are provided with a circular cross sectional shape having a radial size, the radial size influencing the cross sectional area(s) of the opening(s).

23. A sorting device according to any of the preceding claims, wherein the surfaces of the rollers are provided radially deformable by twisting the rollers.

24. A sorting device according to any of the preceding claims, wherein the rollers are coated with a smooth coating so as to reduce frictional resistance between the rollers and the marine species to be sorted.