NL2024190B1

NL2024190B1 - Bottom trawling device and method for bottom trawling

Info

Publication number: NL2024190B1
Application number: NL2024190A
Authority: NL
Inventors: De Bruin Edwin; Caljouw Johannes; Caljouw Hendrik
Original assignee: Marine Systems B V; V O F Zeevisserijbedrijf J Caljouw En Zn
Priority date: 2019-11-08
Filing date: 2019-11-08
Publication date: 2021-07-20

Abstract

A B S T R A C T The invention relates to a bottom trawling device and a method for trawling in a trawling direction along a sea floor, wherein the bottom trawling device comprises a leading element and one or more shafts trailing said leading element 5 in the trawling direction, wherein each shaft defines a shaft axis, wherein the bottom trawling device comprises, for each shaft, at least one brush member that is mounted to the respective shaft and that is rotatable about the shaft axis of the respective shaft.

Description

P137598NL00 Bottom trawling device and method for bottom trawling

BACKGROUND The invention relates to a bottom trawling device and a method for bottom trawling.

A known bottom trawling device comprise an electrified pulse trawl with electrodes that emit short electric pulses to disturb demersal fish, such as flatfish, which are then caught in the net of the pulse trawl.

SUMMARY OF THE INVENTION A disadvantage of the known electrified pulse trawl is that its electric field not only disturbs the demersal fish, but also stuns all fish in the vicinity of the pulse trawl. Consequently, this fishing method has been prohibited in many jurisdictions already.

Currently, one of the alternatives is Lo use conventional bottom trawling devices fitted with tickler chains or chain mats which churn up the ground to disturb the demersal fish. However, the tickler chains or chain mats are relatively heavy. This increases fuel consumption of the fishing boats and causes considerably more damage to the seabed and sea life than the electrified pulse trawl. Hence, the conventional bottom trawling devices are not a reasonable alternative for the electrified pulse trawl.

It is an object of the present invention to provide a bottom trawling device and a method for bottom trawling,

wherein the negative impact of the use of said bottom trawling device on the seabed and/or sea life can be reduced.

According to a first aspect, the invention provides a bottom trawling device for trawling in a trawling direction along a sea floor, wherein the bottom trawling device comprises a leading element and one or more shafts trailing said leading element in the trawling direction, wherein each shaft defines a shaft axis, wherein the bottom trawling device comprises, for each shaft, at least one brush member that is mounted to the respective shaft and that is rotatable about the shaft axis of the respective shaft.

The at least one brush member can be used to brush along and/or churn into the soil of the seabed and thereby provide an incentive for the demersal fish to leave their hiding place and swim into a net arranged directly above and/or downstream of the brush member. The at least one brush member can be relatively light weight. Hence, the overall weight of the bottom trawling device can be reduced significantly compared to conventional tickler chains or chain mats. This significantly decreases the fuel consumption of the fishing boats and can reduce damage to the seabed. Moreover, the bristles of the brushes only brush along the fish and are therefore less likely to harm to the smaller fish, allowing them to escape through the mazes in the net.

Hence, the amount of bycatch can be reduced as well.

In one preferred embodiment the one or more shafts are or comprise a plurality of shafts, wherein each shaft of the plurality of shafts is spaced apart from the shaft axis of an adjacent shaft of the plurality of shafts. By using multiple shafts, each fitted with at least one brush member, the soil can be brushed and/or churned into more effectively and/or a greater area of the seabed can be reached.

Preferably, the plurality of shafts extend mutually parallel. The brush members can thus be arranged side-by-side in a parallel manner.

In another preferred embodiment said at least one brush member is a cylindrical brush extending concentrically about the respective shaft. The cylindrical brush can be used to effectively brush in a circumferential direction about the shaft axis of the respective shaft, thereby disturbing the demersal fish.

Additionally or alternatively, said at least one brush member is a spiral brush. The spiraling arrangement of the bristles on the spiral brush can aid to the rotation of the spiral brush about the shaft axis of the respective shaft when the spiral brush is pulled through the water and/or the ground of the seabed. The spiraling arrangement can also prevent that fish get stuck in the brush member.

In another embodiment said at least one brush member is freely rotatable with respect to the respective shaft. The brush member may for example rotate passively as a result of water flowing relative to the bottom trawling device or the interaction between the bristles and the soil as the brush member is pulled along the seabed. If the brush members are not driven by a drive mechanism, the overall weight of the bottom trawling device can be reduced.

Alternatively, said at least one brush member is fixed to the respective shaft and 1s arranged to rotate together with the respective shaft. The shaft may thus be used as a means for transferring and/or transmitting a rotary motion onto the brush member.

In another embodiment the bottom trawling device further comprises a drive mechanism for driving the rotation of the at least one brush member about the shaft axis of the respective shaft. Hence, the brush members are not arranged to rotate freely. Instead, they are operationally coupled to a drive mechanism for receiving a driving input.

In one embodiment thereof the drive mechanism comprises, for each shaft, a motor for rotating the respective shaft about the shaft axis of the respective shaft. Hence, the bottom trawling device has a dedicated motor for each shaft. Each brush member can thus be individually driven.

In an alternative embodiment thereof the one or more shafts are a plurality of shafts, wherein the drive mechanism comprises a motor common to two or more shafts of the plurality of shafts and a transmission for connecting the motor to each shaft of the two or more shafts for rotating each shaft about the shaft axis of the respective shaft. Using a common motor eliminates the need for individual motors.

Moreover, two or more shafts, preferably all shafts, can be driven simultaneously and/or in a synchronized manner.

Additionally or alternatively, water flows relative to the bottom trawling device when during the trawling, wherein the drive mechanism comprises at least one hydrodynamic drive member that is arranged for converting the flow of water in a rotation that aids the driving of the rotation of the at least one brush member about the shaft axis of the respective shaft. The hydrodynamic drive member may at least partially drive the rotation of the brush member. In that way, the hydrodynamic drive member may reduce amount of driving force that is supplied by the motor{s}. Moreover, if at least a part of the driving force is supplied by the hydrodynamic drive member, the motor (s) may be smaller and/or may not be necessary at all, thereby further reducing the overall weight of the bottom trawling device.

Preferably, the at least one hydrodynamic drive member is coupled to at least one shaft of the one or more shafts for aiding the rotation of said at least one shaft about the shaft axis of said at least one shaft. Hence, the hydrodynamic drive member can be spaced apart from the brush member, i.e. in a more convenient location for the hydrodynamic conversion.

Alternatively, the at least one hydrodynamic drive member is coupled to the at least one brush member for aiding the rotation of said at least one brush member about the shaft axis of the respective shaft. Hence, the hydrodynamic drive member can drive the brush member directly.

Preferably, the at least one hydrodynamic drive member of the previously discussed embodiments is a rotor, preferably a propeller or an impeller. A rotor is an effective hydrodynamic drive member for converting a linear flow of water into a rotary motion.

In another embodiment the one or more shafts extend in the trawling direction. The at least one brush member can thus be arranged in line or parallel to the trawling direction 5 and can have a predominantly sideways or lateral brushing action.

In another embodiment the one or more shafts are a plurality of shafts, wherein the bottom trawling device further comprises a spacer element between each pair of adjacent shafts of the plurality of shafts to space the adjacent shafts of said pair apart in the lateral direction. The spacing between the shafts can thus be kept constant. More in particular, interference and/or collisions between the brush members can be prevented.

In an alternative embodiment the one or more shafts extend in a lateral direction transverse or perpendicular to the trawling direction. The at least one brush member can thus be arranged sideways or transverse to the trawling direction and can have a predominantly forward or rearward brushing action with respect to the trawling direction.

In another embodiment the one or more shafts are a plurality of shafts, wherein the at least one brush member is offset in position on the respective shaft along the shaft axis of the respective shaft with respect to a position of the at least one brush member on an adjacent one of the plurality of shafts.

In another embodiment the leading element is a leading beam, wherein said leading beam extends in a lateral direction perpendicular to the trawling direction. The leading beam can extend across the width of the bottom trawling device and act as a base for the one or more shafts. The leading beam is also typically the beam to which the mouth of the net is attached, as described in the embodiment hereafter.

In another embodiment the bottom trawling device further comprises a net with a mouth and a cod end, wherein the mouth of the net is attached to the leading element and the cod end trails the leading element in the trawling direction. The one ore more shafts can thus be placed in trailing position behind the leading beam extending at least partially into and/or partially overlapping with the mouth of the net.

Preferably, the at least one brush member is in a position on the respective shaft upstream of the mouth of the net. As mentioned earlier, the brush member can thus be used to brush along and/or into the soil of the seabed to provide the demersal fish with an incentive to leave their hiding place and swim into the net directly above and/or downstream of the brush members.

More preferably, the net comprises a footrope, wherein the bottom trawling device further comprises a trailing element that connects the one or more shafts to the footrope at a side of the at least one brush member opposite to the leading element. The footrope can thus be securely held in place directly downstream of the one or more shafts so that the mouth of the net is held open in the vertical direction for receiving the fish that are delivered to the net by the brush members.

Most preferably, the trailing element is a trailing beam, wherein said trailing beam extends in a lateral direction perpendicular to the trawling direction. The trailing beam, like the spacing members, can hold the plurality of shafts in position and/or provide some additional rigidity or structure to the bottom trawling device as whole. Moreover, the trailing beam can be parallel or substantially parallel to the leading beam.

In another embodiment the one or more shafts are flexible. Hence, the one or more shafts can rest securely on the seabed under the influence of gravity as the bottom trawling device is pulled along in the trawling direction and follow irregularities in the seabed.

According to a second aspect, the invention provides a method for trawling in a trawling direction along a sea floor with the bottom trawling device according to any one of the aforementioned embodiments, wherein the method comprises rotating said at least one brush member about the shaft axis of the respective shaft.

The method relates to the practical implementation of the bottom trawling device according to the previously discussed embodiments and thus has the same technical advantages, which will not be repeated hereafter.

In one embodiment said at least one brush member is at least partially driven in rotation by a motor.

Additionally or alternatively, said at least one brush member is at least partially driven in rotation by a hydrodynamic drive member.

The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects and featvres described in the attached dependent claims, can be made subject of divisional patent applications.

BRIEF DESCRIPTION QF THE DRAWINGS The invention will be elucidated on the basis of an exemplary embodiment shown in the attached schematic drawings, in which: figure 1 shows an isometric view of a bottom trawling device according to a first embodiment of the invention; figure 2A shows a top view of the bottom trawling device according to figure 1; figure ZB shows a top view of a detail of the bottom trawling device according to the circle II-B in figure 24; figure 3 shows a side view of the bottom trawling device according to figure 1; figure 4 shows a rear view of the bottom trawling device according to figure 1;

figure 5 shows a top view of an alternative bottom trawling device according to a second embodiment of the invention; figure 6 shows a top view of a further alternative bottom trawling device according to a third embodiment of the invention; figure 7 shows a top view of a further alternative bottom trawling device according to a fourth embodiment of the invention; figure 8 shows a top view of a further alternative bottom trawling device according to a fifth embodiment of the invention; and figure 9 shows a top view of a further alternative bottom trawling device according to a sixth embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTICN Figures 1-4 shows a trawling device 1, in particular a bottom trawling device, for trawling along the bottom of the sea, the sea floor or the seabed B. A trawling device 1 is a type of fishing gear that 1s used by commercial fisheries to catch fish F, in particular demersal fish such as flat fish. The trawling device 1 is submerged onto the seabed and subsequently pulled, dragged or towed along the seabed and/or through the soil by one or more fishing boats. The soil is churned up as the trawling device 1 passes, causing the fish to leave their hiding place.

As shown in figure 1, the trawling device 1 comprises one or more pulling members 2, also known as a trawl warp, for connecting the trawling device 1 to a fishing boat {not shown). The trawling device 1 is arranged to be pulled along the seabed in a trawling direction T. The trawling device 1 further comprises a leading element 3 and a net 4 attached to the leading element 3. The net 4 comprises a mouth 40 that is held open by the leading element 3 in a horizontal direction and a closed cod end 41 for catching the fish F that swim into the mouth 40. The net 4 has mazes with a predefined size such that bycatch can escape from the net 4. The mouth 40 of the net 4 is defined by a headline 42 that 1s attached directly to the leading element 3 and a footrope 43 that is pulled over the seabed B.

In this exemplary embodiment, the leading element 3 comprises a leading beam 30 that extends in a lateral direction L transverse or perpendicular to the trawling direction T and side boards 31, 32, also known as shoes, on opposite sides of said leading beam 30 in the lateral direction L.

The headline 42 is attached directly to the side boards 31, 32. The trawling device 1 according to the present invention further comprises a plurality of shafts 5 trailing said leading element 3 in the trawling direction T.

Each shaft 5 defines a shaft axis S that is spaced apart from the shaft axis S of an adjacent shaft 5 of the plurality of shafts 5, i.e. horizontally or in the lateral direction L.

Preferably, as shown in figure 3, the plurality of shafts 5 are flexible, such that the plurality of shafts 5 can rest securely on the seabed B under the influence of gravity as the trawling device 1 is pulled along in the trawling direction T.

As best seen in figure 2A, the trawling device 1 comprises, for each shaft 5 or per shaft 5 of the plurality of shafts 5, a brush member 6 that is mounted to the respective shaft 5. The brush member 6 is rotatable about the shaft axis S of the respective shaft 5. In this exemplary embodiment, the brush member 6 is freely rotatable with respect to the shaft 5. Hence, there is no drive component connected to the brush member 6. The brush member 6 may be driven by the flow of water that passes the trawling device l as a result of the motion of said trawling device 1 in the trawling direction T, or by the relative movement between the trawling device 1 and the soil of the seabed B through which the brush member 6 is pulled during trawling.

As illustrated with the alternative embodiments in figures 5-8, which will be discussed hereafter, the brush member 6 may alternatively be driven in rotation.

One of the brush members 6 is shown in more detail in figure 2B.

In this exemplary embodiment, the brush member 6 is a cylindrical brush.

As such, the brush member © comprises a central hub 60 and a plurality of bristles 61 distributed about the central hub 60 and protruding outwards from said central hub 60, preferably in a radial or substantially radial direction.

The brush member 6 as shown in figure 2B is straight cylindrical, meaning that the diameter of the cylindrical brush is constant.

Alternatively, the diameter of the cylindrical brush may vary.

The cylindrical brush may for example have a tapering or conical shape in a certain direction to dig deeper or less deep into the soil of the seabed B.

In this particular example, the brush member 6 is a spiral brush, meaning that the bristles 61 are arranged in individual rows that extend helically about the central hub 60 at a certain pitch.

Preferably, the pitch is less than half the circumference of the brush member 6 along the length of the brush member 6. The bristles 61 are resiliently flexible.

Preferably, the bristles 61 are made from or comprise a synthetic or plastic material.

In the exemplary embodiment as shown in figure 2A, the brush members 6 are all located at the same position along the respective shafts 5. Alternatively, the positions of the brush members 6 may be offset with respect to each other, i.e. such that the plurality of shafts 5 can be placed closer together without the brush members 6 colliding with each other.

Hence, more shafts 5 can be fitted in the same space.

Although only one brush member 6 is shown per shaft 5, it will be clear that more than one brush member 6 may be fitted to the same shaft 5, one behind the other, within the scope of this invention.

Similarly, the brush member 6 as shown may be divided into several brush sections (not shown) with different characteristics.

It is further noted that when a shaft 5 is not fitted with any brush member 6, it is not considered part of the plurality of shafts 5 in the context of the present invention.

As best seen in figure 2A, the trawling device 1 further comprises a spacer element 7 between each pair of adjacent shafts 5 of the plurality of shafts 5. The spacer element 7 comprises two bushing 70 which are fitted around the adjacent shafts 5 of the pair and a relatively rigid link 71 extending between and interconnecting the bushings 70. One of the bushings 70 of the spacer element 7 may also form one of the bushings 70 of an adjacent spacer element 7. Each spacer element 7 spaces the two shafts 5 of the respective pair of adjacent shafts 5 apart in the lateral direction L.

The spacing between the shafts 5 can thus be kept constant.

More in particular, interference and/or collisions between the brush members 6 can be prevented.

As further shown in figure 2A, the trawling device 1 comprises a trailing element 8 that connects the plurality of shafts 5 to the footrope 43 at a side of the brush member 6 opposite to the leading element 3. The leading element 3 is thus located upstream of the brush members 6 considered in the trawling direction T.

The trailing element 8 thus keeps the mouth 40 of the net 4 open in the horizontal direction.

Moreover, the trailing element 8 trails the leading element 3 in a position vertically below the position where the headline 42 is attached to the side boards 31, 32, thereby ensuring that the mouth 40 of the net 4 remains open in a vertical direction as well.

Like the leading beam 30, the trailing element 8 is or comprises a trailing beam 80 extending in the lateral direction L.

As a result, the trailing beam 40 can be parallel or substantially parallel to the leading beam 30, in particular with a plurality of shafts 5 of equal length extending therein between.

As shown in figures 1-4, the brush members 6 of the aforementioned trawling device 1 can be used in a method for trawling to brush along and/or into the soil of the seabed B.

The bristles 61 of the brush members 6 provide an incentive for the demersal fish F to leave their hiding place and swim into the net 4 that is arranged directly above and/or downstream of the brush members 6. The brush members 6 have the technical advantage over the conventional tickler chains and chain mats that they can be relatively light weight.

Hence, the overall weight of the trawling device 1 can be reduced significantly.

This significantly decreases the fuel consumption of the fishing boats and can reduce damage to the seabed B.

Moreover, the bristles 61 of the brush members 6 only brush along the fish and are therefore less likely to harm to the smaller fish, allowing them to escape through the mazes in the net 4. Hence, the amount of bycatch can be reduced as well.

Figure 5 shows an alternative trawling device 101 according to a second embodiment of the invention, that differs from the previously discussed trawling device 1 in that the alternative trawling device 101 comprises a drive mechanism 109 for actively driving the rotation of the brush member 6 about the shaft axis S of the respective shaft 5. In other words, the brush members 6 are not arranged to rotate freely.

Instead, they are operationally coupled to a drive mechanism 109 for receiving a driving input.

In the embodiment as shown in figure 5, the drive mechanism 109 comprises, for each shaft 5, a motor 190 for rotating the respective shaft 5 about the shaft axis S of the respective shaft 5. In other words, the trawling device 1 has a dedicated motor 190 for each shaft 5. The brush member 6 is fixed to the respective shaft and is arranged to rotate together with the respective shaft 5. The rotation of the shaft 5 can thus be transferred or transmitted directly onto the brush member 6. Because of the individual motors 190, each brush member 6 can thus be individually driven.

The brush members 6 may be driven at the same rotational speed, or at different rotational speeds.

When the shaft 5 is used as a drive member, the shaft 5 needs to be rotatable about the respective shaft axis S with respect to the leading element 3 and the trailing element 8. The shaft 5 may for example be received and/or fitted in rotation bearings at the leading element 3 and the trailing element 8. Alternatively, the shaft 5 may be fitted inside a sleeve or duct (not shown), wherein the sleeve or duct is fixed to the leading element 3 and the trailing element 8 and the shaft 5 is rotatable within the sleeve or duct. The sleeve or duct will have to be interrupted at the position of the brush member 6 to connect the internal shaft 5 to the external brush member 6.

Figure 6 shows a further alternative trawling device 201 according to a third embodiment of the invention. The further alternative trawling device 201, like the aforementioned alternative trawling device 101, has a drive mechanism 209 for rotating the shafts 5. However, instead of having individual, dedicated motors, the drive mechanism 209 of the further alternative trawling device 201 features a single motor 290 common to two or more shafts 5 and a transmission 291 for connecting the motor 290 to each shaft 5 of the two or more shafts 5. Hence, the single motor 290 can be used for rotating each shaft 5 about the shaft axis S of the respective shaft 5. Using a common motor 290 eliminates the need for individual motors, which can reduce the overall weight and/or complexity of the further alternative trawling device 201. Moreover, the two or more shafts 5 can be driven simultaneously and/or in a synchronized manner. In the embodiment as shown, all shafts 5 are driven by the same common motor 290. Alternatively, two or more motors may be provided that each drive a group of two or more shafts 5. Figure 7 shows a further alternative trawling device 301 according to a fourth embodiment of the invention, in which the drive mechanism 309 utilizes a hydrodynamic principle to drive the rotation of the shafts 5, or at least partially aid in said rotation in addition to the previously described driving by the individual motors or the single motor. As shown in figure 7, the drive mechanism 309 of the further alternative trawling device 301 comprises, for each shaft 5, a hydrodynamic drive member 390. The hydrodynamic drive member 390 is coupled or fixed to the respective shaft and preferably rotates together with the respective shaft

5. The hydrodynamic drive members 390 are positioned 5 such that a water flow W is directed through said hydrodynamic drive members 390 in a direction opposite to the trawling direction T when the further alternative trawling device 301 is pulled, dragged or towed through the water in said trawling direction T. In this particular example, the hydrodynamic drive members 390 are located upstream of the leading element 3 so the flow of water W can flow towards the hydrodynamic drive members 390 uninterruptedly. Alternatively, the hydrodynamic drive members 390 may be located downstream of the leading element 3, i.e. somewhere along the length of the plurality of shafts 5.

The hydrodynamic drive member 390 is arranged for converting the flow of water W in a rotation that directly drives and/or at least partially aids the driving of the rotation of the respective shaft 5 about the shaft axis S of the respective shaft 5. The hydrodynamic drive member 390 may reduce amount of driving force that is supplied by the previously described motor(s}. Moreover, if at least a part of the driving force is supplied by the hydrodynamic drive member 390, the motor(s) may be smaller and/or may not be necessary at all, thereby further reducing the overall weight of the further alternative trawling device 301.

In the exemplary embodiment as shown in figure 7, the hydrodynamic drive members 390 are rotors, specifically propellers, for converting the linear flow of water W into a rotation of the plurality of shafts 5. Alternatively, an impeller or another suitable hydrodynamic body may be used.

It will be clear to one skilled in the art that more than one hydrodynamic drive member 390 may be provided for each shaft 5 to further aid to the driving of the rotation of the respective shaft 5. Alternatively, a single hydrodynamic drive member 390 may be used with a suitable transmission to drive two or more shafts 5 of the plurality of shafts 5 simultaneously.

Figure 8 shows a further alternative trawling device 401 according to a fifth embodiment of the invention, in which the drive mechanism 409 utilizes a similar hydrodynamic principle as in the aforementioned embodiment. However, instead of using the hydrodynamic drive members to drive the plurality of shafts 5, the drive mechanism 409 of the final alternative trawling device 401 comprises hydrodynamic drive members 490 which are directly coupled to the brush members 6 on the plurality of shafts 5 for directly driving said brush members 6 in rotation.

Figure 9 shows a final alternative trawling device 501 according to a sixth embodiment of the invention which differs from the previously discussed trawling devices 1, 101, 201, 301, 401 in that the plurality of shafts 505 extend in the lateral direction L transverse or perpendicular to the trawling direction T. The plurality of shafts 505 may be mounted in a trailing frame 580 that trails the leading element 3 in the trawling direction T and that comprises a trailing beam 580 similar to the previously discussed trailing beam and two side beams 581, 582 on opposite sides in the lateral direction L for carrying the opposite ends of the plurality of shafts 505. In that case, the drive mechanism 509 with one or more motor(s) 590 and/or hydrodynamic drive members for driving the plurality of shafts 505 may be located at one or both sides of the trailing frame 508, i.e. at the side beams 581, 582. Each shaft 505 may be fitted with one or more of the brush members 6 strategically placed to churn up the soil of the seabed 9 directly upstream of the mouth 40 of the net 4. Preferably, the shafts 505 are fitted with a relatively wide single brush member or with more than one brush member 6 to span a considerable portion of the width of the mouth 40 in the lateral direction L.

As shown in figure 9, the position of the brush members 6 on the plurality of shafts 505 may be offset in the direction of the shaft axes S, i.e. in the lateral direction L, to more effectively churn up the soil of the seabed B.

Alternatively, the embodiment as shown in figure 9 may be equally effective with only one of the shafts 505 fitted with one wide brush member 6 or a plurality of smaller brush members 6.

It 1s to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the scope of the present invention.

LIST OF REFERENCE NUMERALS 1 trawling device 2 pulling member 3 leading element 30 leading beam 31 side board 32 side board 4 net 40 mouth 41 cod end 42 headline 43 footrope 5 shaft 6 brush member 60 central hub 61 bristle 7 spacer element 70 bushing 71 link 8 trailing element 30 trailing beam 101 alternative trawling device 109 drive mechanism 190 motor

201 further alternative trawling device 209 drive mechanism 290 motor 291 transmission

301 further alternative trawling device 309 drive mechanism 390 hydrodynamic drive member 401 further alternative trawling device 409 drive mechanism

490 hydrodynamic drive member 501 further alternative trawling device 505 shaft 508 trailing frame 580 trailing beam

581 first side beam 582 second side beam 509 drive mechanism 590 motor B seabed

F fish L lateral direction S shaft axis T trawling direction W flow of water

Claims

CONCLUSIONS

A bottom trawl device (1, 101, 201, 301, 401, 501) for trawling in a trawl direction (T) along a seabed (B), wherein the bottom trawl device (1, 101, 201, 301, 401, 501) is a leading element (3) and one or more shafts (5, 505) trailing behind the leading element (3) in the track direction (T), each shaft (5, 505) defining an shaft axis (S), wherein the bottom trawl device (1, 191, 201, 301, 401, 501) comprises, for each shaft (5, 505), at least one brush member (6) which is mounted on the respective shaft (5, 505) and which is rotatable about the shaft axis (S) of the respective shaft (5, 505).

The bottom trawl device of claim 1, wherein the one or more shafts is a plurality of shafts, each axis of the plurality of shafts being spaced from the shaft axis of an adjacent shaft of the plurality of shafts.

Bottom trawl device according to claim 2, wherein the plurality of shafts extend parallel to one another.

Bottom trawl device according to any one of the preceding claims, wherein the at least one brush part is a cylindrical brush extending concentrically around the respective axis.

Bottom trawl device according to any one of the preceding claims, wherein the at least one brush part is a spiral brush.

Bottom trawl device as claimed in any of the foregoing claims, wherein the at least one brush part is freely rotatable relative to the respective shaft.

Bottom trawl device according to any one of claims 1-5, wherein the at least one brush part is fixed to the respective shaft and is arranged to rotate together with the respective shaft.

Bottom trawl device according to any one of the preceding claims, wherein the bottom trawl device further comprises a drive mechanism for driving the rotation of the at least one brush part about the shaft axis of the respective shaft.

A bottom trawl device according to claim 3, wherein the drive mechanism comprises, for each shaft, a motor for rotating the respective shaft about the shaft axis of the respective shaft.

The bottom trawl device of claim 8, wherein the one or more shafts is a plurality of shafts, the drive mechanism comprising a motor common to two or more shafts of the plurality of shafts and a transmission for connecting the motor of each shaft of the two or more shafts for rotating each shaft about the shaft axis of the respective shaft.

A bottom trawl device according to any one of claims 3-10, wherein water flows relative to the bottom trawl device during trawling, the drive mechanism comprising at least one hydrodynamic drive member adapted to convert the water flow into a rotation that assists in driving the rotation of the at least one brush part around the shaft axis of the respective shaft.

The bottom trawl device of claim 11, wherein the at least one hydrodynamic drive member is coupled to at least one shaft of the one or more shafts to aid rotation of the at least one shaft about the shaft axis of the at least one shaft.

A bottom trawl arrangement according to claim 11, wherein the at least one hydrodynamic drive member is coupled to the at least one brush member to aid rotation of the at least one brush member about the shaft axis of the respective shaft.

Bottom trawl device according to any one of claims 11-13, wherein the at least one hydrodynamic drive part is a rotor, preferably a propeller or an impeller.

15. Bottom trawl device as claimed in any of the foregoing claims, wherein the one or more shafts project in the trawling direction.

The bottom trawl arrangement of claim 15, wherein the one or more axes is a plurality of axes, the bottom trawl arrangement further comprising a spacer element between each pair of adjacent axes of the plurality of axes so as to allow adjacent axes of the pair in a lateral direction perpendicular to to keep track of direction apart.

17. Bottom trawl device according to any one of claims 1-14, wherein the one or more axes extend in a lateral direction transverse or perpendicular to the trawling direction.

A bottom trawl device according to any one of the preceding claims, wherein the one or more shafts is a plurality of shafts, wherein the at least one brush part is offset in position on the respective shaft along the shaft axis of the respective shaft with respect to a position of the at least one brush member on an adjacent axis of the plurality of axes.

A bottom trawl device according to any one of the preceding claims, wherein the leading element is a leading beam, the leading beam extending in a lateral direction perpendicular to the trawling direction.

A bottom trawl device according to any one of the preceding claims, wherein the bottom trawl device further comprises a net having a mouth and a catch end, the mouth of the net being attached to the leading end and the catch end trailing with respect to the leading element in the trawl direction.

A bottom trawl device according to claim 20, wherein the at least one brush member is in a position on the respective axis upstream of the mouth of the net.

A bottom trawl device according to claim 20 or 21, wherein the net comprises a ground line, the bottom trawl device further comprising a trailing element connecting the one or more shafts to the ground line on a side of the at least one brush part opposite to the leading element.

23. Bottom trawl device according to claim 22, wherein the trailing element is a trailing beam, the trailing beam extending in a lateral direction perpendicular to the trawl direction.

24. Bottom trawl device according to any one of the preceding claims, wherein the one or more shafts are flexible.

A method of trawling in a trawling direction (TY) along a seabed (B) with the bottom trawl device (1, 101, 201, 301, 401, 501) according to any one of the preceding claims, wherein the method comprises rotating the at least one brush part (6) around the shaft axis (S) of the respective shaft (5, 505).

The method of claim 25, wherein the at least one brush member is at least partially driven in rotation by the motor.

A method according to claims 25 or 26, wherein the at least one brush member is at least partially driven in rotation by a hydrodynamic drive member.

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