WO2017168110A1

WO2017168110A1 - Fishing drag for catching seabed dwelling marine animals

Info

Publication number: WO2017168110A1
Application number: PCT/GB2016/000073
Authority: WO
Inventors: Richard Gidney
Original assignee: Deeside Marine Ltd
Current assignee: Deeside Marine Ltd
Priority date: 2016-04-01
Filing date: 2016-04-01
Publication date: 2017-10-05
Anticipated expiration: 2018-10-01

Abstract

A drag (31, 131, 231, 331, 411) for harvesting seabed dwelling marine animals such as scallops, sea urchins and sea cucumbers. The drag (31, 131, 231, 331, 411) has a towing bar assembly (33, 133, 233, 333) connectable to a vessel via a warp, a drag frame with a front portion (39, 139, 239, 339) attached to the towing bar assembly (33, 133, 233, 333) and a rear portion (41, 141, 241, 341) which is attachable to a container (62, 162, 262, 362). The drag frame has a first side member (45, 145, 245, 345) and a second side member (47, 147, 247, 347), each having a lower seabed engaging surface (49, 149, 249, 349) and a sweeper (51, 151, 251, 351) comprising a resilient element having a fixed end which is operatively connected to the first side member (45, 145, 245, 345) and to the second side member (47, 147, 247, 347) and a free end (57, 157, 257, 357) which extends to a position planar with or extending beyond the lower seabed engaging surfaces (49, 149, 249, 349) of the first (45, 145, 245, 345) and second sides (47, 147, 247, 347) so as to sweep across the seabed, in use.

Description

Fishing Drag for Catching Seabed Dwelling Marine Animals

Introduction The present invention relates to a fishing drag and in particular to a frame for a fishing drag for harvesting seabed dwelling marine animals such as molluscs, sea urchins and sea cucumbers.

Background to the Invention

Dragging or dredging is used for harvesting bivalve molluscs such as oysters, clams and scallops and other animals such as sea urchins and sea cucumbers. A drag or dredge is a metal framed basket attached to a set of connected iron rings and/or wire netting called a belly or chain belly. The lower edge of the frame has a raking bar, with or without teeth or swords depending upon the species of mollusc that is being caught. In use, the catch is lifted off the seabed or out of the sea by the raking (or teeth) bar and passes back into a basket or bag known as a belly. Depending on the size of the boat and the depth of water fished the dredge may comprise a number of separate dredges or 'bags' or a single large dredge.

Scallop is a common name that is primarily applied to any one of numerous species of saltwater clams or marine bivalve molluscs in the taxonomic family Pectinidae, the scallops. However, the common name "scallop" is also sometimes applied to species in other closely related families within the superfamily Pectinoidea. Scallops inhabit all the oceans of the world. Most species live in relatively shallow waters from the low tide line to 100 meters, while others prefer much deeper water. Scallops can be found living within, upon, or under either rocks, coral, rubble, sea grass, kelp, sand, or mud. Most adult specimens are either byssally attached or cemented to a substrate, while others are free swimmers. In Europe there are two main types of Scallop that are fished commercially. Pecten Maximus or King Scallop burrows into the sediments on the seabed with their flat valve uppermost. Aequipecten Operculari or Queen Scallop is smaller in size than the King Scallop and inhabit the sea bed.

Placopecten magellanicus, the Atlantic Sea Scallop is a commercially important pectinid bivalve mollusc native to the western Atlantic Ocean. The shell has a classic form, with smooth shell and edges, unlike Pecten maximus (common name the "great scallop" or "king scallop") which has flutes and scalloped edges. It ranges in size from around 80 mm to 170 mm in diameter. It is found on the continental shelf of the northwest Atlantic from the north shore of the Gulf of St. Lawrence south to Cape Hatteras, North Carolina.

The Atlantic Sea Scallop is typically found at depths ranging from 18-110 m, but may also Occur in waters as shallow as 2 m in estuaries and bays along the Maine coast and in Canada. In southern areas, scallops are primarily found at depths between 45 and 75 m, and are less common in shallower water (25-45 m) due to higher sea temperatures. Although sea scallops are not common at depths greater than about 110 m, some populations have been found as deep as 384 m, and deep-water populations at 170- 180 m have been reported in the Gulf of Maine. Sea scallops often occur in

aggregations called beds. Beds may be sporadic (perhaps lasting for a few years) or essentially permanent (e.g., commercial beds supporting the Georges Bank fishery). Adult Atlantic Sea Scallops are generally found on firm sand, gravel, shells, and rock.

In the North Atlantic fishery along the East Coast of North America, the New Bedford drag is the most commonly used drag. One version of this equipment is described in a paper by Ronald Smolowitz dated 2006 entitled "Sea Scallop Harvest Gear:

Engineering for Sustainability" available at

http://coonamessettfarmfoundation.ora.Dreviewdns.com/wp-content/uploads/Smolowitz- 2006.pdf Figure 1 A is a perspective view and figure 1 B a side view of the New Bedford drag described in the above referenced document. The Drag 1 has a frame 3, the bottom of which consists of a rectangular steel cutting bar 5 which rests on steel-plated shoes 7. Attached to the top of the frame is a forward-angled depressor plate 9 that keeps the dredge on the sea bed when being towed. At the bottom of the frame 3, fastened to the shoes 7, is the sweep chain 11. The lower portion of the collecting net 13 (called the chain bag) is attached to the sweep chain 11. Also attached to the sweep chain 11 are two triangular sections called 'diamonds'. The chain bag and 'diamonds'

are all fabricated out of welded steel rings and links. The top of the collecting bag 13 consists of a twine top 15, followed by a linked ring section called the apron 17. To the aft end of the net is attached a club stick 19 and dump chain 21 which holds the bag's shape and facilitates dumping.

Vessels usually fish towing two drags at the same time from hanging blocks suspended in gallows frames on each side of the vessel. Tow duration depends on bottom type and scallop density but most tows are between 30-50 minutes long. Typically, the gear is towed at 4-5 knots using a 3:1 scope (warp length to water depth). Drag size as defined by frame width, within the offshore fleet is mostly around 4-5 m wide. There are several objectives in seeking to improve the efficiency of the scallop fishing process. These include:

reducing the fuel used by the vessel when dragging; reducing bi-catch; reducing the catch of small and immature scallops; reducing the effect of snagging the drag on objects which are embedded on the seabed such as rocks; and reducing damage to the sea bed.

PCT/GB2009/002022 describes a dredge frame which has been designed to catch King scallops. As stated above, King scallops are found in European coastal waters and in contrast to the Atlantic Sea Scallop, King scallops burrow into the sea bed.

PCT/GB2009/002022 describes a dredge frame with resiliently mounted teeth which are positioned to penetrate the sea bed so as to dig out the King Scallops. In addition, the resiliently mounted teeth spring backwards when they encounter a fixed object such as a seabed rock.

In most cases, North Atlantic Scallops are fished in beds where they are numerous. One advantage of the New Bedford Drag design is that the cutting bar, in effect sweeps up all of the scallops in the area through which the Drag is pulled.

King scallops are buried and found in lower concentrations than North Atlantic Scallops and therefore there is little or no expectation amongst those skilled in the art that the above described King Scallop Dredge would operate successfully for the efficient collection of North Atlantic Sea Scallops. The expectation amongst those skilled in the art is that too many of the scallops would be left on the sea bed.

Summary of the Invention

In accordance with a first aspect of the invention there is provided a drag for harvesting seabed dwelling marine animals, the drag comprising:

a towing bar assembly connectable to a vessel via a warp;

a drag frame having a front portion attached to the towing bar assembly and a rear portion which is attachable to a mollusc collection receptacle;

the drag frame having a first side member and a second side member, each having a lower seabed engaging surface; and

a sweeper comprising a resilient element having a fixed end which is operatively connected to the first side member and to the second side member and a free end which extends to a position planar with or extending beyond the lower seabed engaging surfaces of the first and second sides so as to sweep across the seabed, in use.

Preferably, the towing bar is connected to the first side member and to the second side member.

Preferably, the front portion is connectable to the upper part of a collecting net. Preferably, a rail extends around an upper part of the front portion and is connectable to the upper part of a collecting net. Preferably, the rear portion comprises a connector for attaching the lower part of the open end of a collecting net.

Preferably, the first side is a solid panel. Optionally, the second side is a solid panel.

Advantageously, when the first and/or second sides are continuous plates, they act to funnel water through the drag which assists with the collection of molluscs and the separation of molluscs from heavier and denser objects such as stones.

Preferably, the first side is a frame.

Optionally, the second side is a frame. Preferably, the rear portion comprises connectors for attaching the lower part of an open end of the collecting net.

Preferably, the sweeper fixed end is connected to a support member which is connected to the first side and the second side of the drag frame.

Preferably, the free end of the sweeper allows the sweeper to resiliently bend/deform when it encounters an embedded object on in its path on the sea bed.

For example, it the sweeper encounters a stone or rock that will not move, resilient deformation will allow the drag frame to pass over the stone or rock. Optionally, the sweeper extends from the fixed end perpendicular to the direction of travel in use.

Optionally, the sweeper extends from the fixed end at around 120° to the direction of travel in use.

Preferably, the amount by which the sweeper extends beyond the lower seabed engaging surfaces of the first and second sides is adjustable. Preferably, the amount by which the sweeper extends beyond the lower seabed engaging surfaces of the first and second sides by moving the fixed end of the sweeper.

More preferably by altering the position at which the support member is connected to the first and second sides.

Optionally, the sweeper comprises a continuous sheet or panel of resilient material. Preferably, the panel has an ultimate elongation of between 12 and 23 N/mm². Preferably, the panel has a tear resistance of at least 7 N/mm. Preferably, the panel has an ultimate elongation of up to 10% Optionally, the sweeper is made from a laminated rubber/canvas material.

Optionally, the panel comprises a 5 ply rubber/canvas material.

Other suitable materials may be used.

Optionally, the sweeper comprises a plurality of spring mounted teeth mounted between the first side member and the second side member. Preferably, the teeth are evenly spaced between the first side member and the second side member.

Preferably, the springs are configured to allow the teeth to move longitudinally and transversely with respect to the direction of travel.

Preferably, the spring is a coil spring mounted on the support member to allow transverse and longitudinal movement. Advantageously, transverse movement of the teeth allows them to narrow the effective distance between the teeth and to assist in sweeping up molluscs from the seabed.

Preferably, the seabed engaging portion of the first and second side members comprises one or more wheel.

Optionally, the seabed engaging portion of the frame further comprises one or more track.

Preferably, the track is moveable.

Optionally the track is flexible.

Brief Description of the Drawings

The present invention will now be described with reference to the accompanying drawings in which:

Figure 1 A is a perspective view and figure 1 B a side view of the New Bedford drag;

Figure 2A is a perspective view of a first embodiment of the present invention, Figure 2B is a front view of a first embodiment of the present invention and Figure 2C is a side view of a first embodiment of the present invention; Figure 3A is a perspective view of a second embodiment of the present invention, Figure 3B is a front view of a second embodiment of the present invention and Figure 3C is a side view of a second embodiment of the present invention;

Figure 4A is a perspective view of a third embodiment of the present invention, Figure 4B is a front view of a third embodiment of the present invention and Figure 4C is a side view of a third embodiment of the present invention; Figure 5A is a perspective view of a fourth embodiment of the present invention, Figure 5B is a front view of a fourth embodiment of the present invention and Figure 5C is a side view of a fourth embodiment of the present invention; and

Figure 6 is a schematic diagram showing four drags in accordance with the present invention connected to a tow bar.

Detailed Description of the Drawings Figures 2A to 2C show a first embodiment of the present invention. Figure 2A is a perspective view of a first embodiment of the present invention, Figure 2B is a front view of the first embodiment of the present invention and Figure 2C is a side view of the first embodiment of the present invention. The figures show a drag 31 with a tow bar assembly 33 which has a connecting hole 35 which allows the drag 31 to be connected directly to a trawler via a warp or by means of the arrangement shown below with reference to figure 6. Support means extend from the connector 35 to the front portion of the drag 39 to which they are fixedly connected in this embodiment of the present invention. The rear portion of the drag 41 has a bar from which a number of coaxial connecting rings project. The connecting rings 43 are positioned to accept a pole (not shown) which can be inserted through the rings 43 to attach the lower portion of the catch collecting net to the rear portion 41 of the drag 31. The drag has two sides, the first side 45 and the second side 47. Both sides have a seabed engaging surface 49 which comprises a skid 49. In use, much of the weight of the drag is supported by the skids 49. The sweeper 51 comprises a flat panel of resilient, pliable material which is secured to a bar 55 at its fixed end. In this

embodiment of the invention, the sweeper extends down vertically from the fixed end. The free end of the sweeper extends down to a position planar with or extending slightly beyond the skids. The sweeper is securely attached to the Drag 31 at bar 55 and its resilience will allow it to move back and forth when it encounters objects on the sea bed. In addition, the resilience and pliability of the sweeper 51 across its width means it can flex across the width of the Drag 31. In this embodiment of the present invention the sweeper is made from rubber however, other materials having the appropriate physical properties may be used. In use, a collecting bag 62 having a heavy chain lower portion 63 and a lightweight twine upper portion 65 (shown partially in Fig 2C) is attached to the Drag 31 and the Drag 31 is connected to a fishing vessel in a standard way and is positioned on the sea bed. The vessel moves along the surface of the sea and pulls the Drag 31 along the sea bed. The free end 57 of the sweeper 51 which is positioned either level the skids 49 or protruding slightly beyond the skids 49 sweeps along the sea bed and collects molluscs that are sitting on the sea bed. The molluscs accumulate on the front surface of the sweeper and the direction of movement of the vessel causes the molluscs to be swept into the collecting bag. As and when the sweeper 51 encounters an embedded object such as a rock at one position across its width, the resilience of the sweeper allows it to bend and pass over the rock and return to its normal, flat panel shape. In addition, movement of the vessel and the use of solid side panels 45, increases the flow of water through the drag which assists with moving the molluscs into the collecting bag 62. A gap is present between the sweeper bar 55 and the bar to which the rings are connected through which denser objects such as stones without entering the collecting bag 62. Figures 3A to 3C show a second embodiment of the present invention. Figure 3A is a perspective view of a second embodiment of the present invention, Figure 3B is a front view of the second embodiment of the present invention and Figure 3C is a side view of the second embodiment of the present invention. The figures show a drag 131 with a tow bar assembly 133 which has a connecting hole 135 which allows the drag 131 to be connected directly to a trawler via a warp or by means of the arrangement shown below with reference to figure 6. Support means extend from the connector 135 to the front portion of the drag 139 to which they are fixedly connected in this embodiment of the present invention. The rear portion of the drag 141 has a bar from which a number of coaxial connecting rings project. The connecting rings 143 are positioned to accept a pole (not shown) which can be inserted through the rings 143 to attach the lower portion of the catch collecting net to the rear portion 141 of the drag 131.

The drag has two sides, the first side 145 and the second side 147. Both sides have a seabed engaging surface 149 which comprises a skid 149. In use, much of the weight of the drag is supported by the skids 149. The sweeper 151 comprises a flat panel of resilient, pliable material which is secured to a bar 155 at its fixed end. In this embodiment of the invention, the sweeper is angled towards the direction of travel of the Drag 131 , in use; this may assist in efficiently removing the molluscs from the sea bed and in moving them into the collecting bag. The free end of the sweeper extends down to a position planar with or extending slightly beyond the skids. The sweeper is securely attached to the Drag 31 at bar 155 and its resilience will allow it to move back and forth when it encounters objects on the sea bed. In addition, the resilience and pliability of the sweeper 151 across its width means it can flex across the width of the Drag 131. In this embodiment of the present invention the sweeper is made from rubber however, other materials having the appropriate physical properties may be used.

In use, a collecting bag 162 having a heavy chain lower portion 163 and a lightweight twine upper portion 165 (shown partially in Fig 3C) is attached to the Drag 131 and the Drag 131 is connected to a fishing vessel in a standard way and is positioned on the sea bed. The vessel moves along the surface of the sea and pulls the Drag 131 along the sea bed. The free end 157 of the sweeper151 which is positioned either level the skids 149 or protruding slightly beyond the skids 149 sweeps along the sea bed and collects molluscs that are sitting on the sea bed. The molluscs accumulate on the front surface of the sweeper and the direction of movement of the vessel causes the molluscs to be swept into the collecting bag. As and when the sweeper 151 encounters an embedded object such as a rock at one position across its width, the resilience of the sweeper allows it to bend and pass over the rock and return to its normal, flat panel shape. In addition, movement of the vessel and the use of solid side panels 45, increases the flow of water through the drag which assists with moving the molluscs into the collecting bag 162. A gap is present between the sweeper bar 155 and the bar to which the rings are connected through which denser objects such as stones without entering the collecting bag 162. In the above examples, the sweeper comprises a 5 ply rubber/canvas panel having three rubber layers separated by two canvas layers and the following physical properties

Description Unit Specs

Panel thickness mm 15

Top cover mm 6 + 0.3

Bottom cover mm 2 + 0.2

Belt weight kg/m2 — 18.91

Full panel elongation

At 10 % reference load % Max.2.5

At breaking % Min. 10

Figures 4A to 4C show a third embodiment of the present invention. Figure 4A is a perspective view of a third embodiment of the present invention, Figure 4B is a front view of the third embodiment of the present invention and Figure 4C is a side view of the third embodiment of the present invention. The figures show a drag 231 with a tow bar assembly 233 which has a connecting hole 235 which allows the drag 231 to be connected directly to a trawler via a warp or by means of the arrangement shown below with reference to figure 6. Support means extend from the connector 235 to the front portion of the drag 239 to which they are fixedly connected in this embodiment of the present invention. The rear portion of the drag 241 has a bar from which a number of coaxial connecting rings project. The connecting rings 243 are positioned to accept a pole (not shown) which can be inserted through the rings 243 to attach the lower portion of the catch collecting net to the rear portion 241 of the drag 231.

The drag has two sides, the first side 245 and the second side 247. Both sides have a seabed engaging surface 249 which comprises a skid 249. In use, much of the weight of the drag is supported by the skids 249.

In this embodiment of the present invention, the sweeper 251 comprises a set of teeth or tines 267 each of which is mounted on a bar 263 by means of coil springs 265 which are wrapped around the bar 263. The tines extend vertically downwards from the bar such that their free ends 257 are positioned at or slightly beyond the position of the skids when on the sea bed.

The sweeper is securely attached to the Drag 231 at bar 263 and its resilience will allow the tines 267 to move back and forth when they encounter objects on the sea bed. In addition, the spring 265 allows the tines 267 to move in a transverse direction 269 which further assists with the process of catching molluscs.

In use, a collecting bag 262 having a heavy chain lower portion 263 and a lightweight twine upper portion 265 (shown partially in Fig 3C) is attached to the Drag 231 and the Drag 231 is connected to a fishing vessel in a standard way and is positioned on the sea bed. The vessel moves along the surface of the sea and pulls the Drag 231 along the sea bed. The free ends 257 of the tines 267 are positioned either level the skids 249 or protruding slightly beyond the skids 249 sweeps along the sea bed and collects molluscs that are sitting on the sea bed. The molluscs accumulate on the tines 267 and the direction of movement of the vessel causes the molluscs to be swept into the collecting bag. The transverse movement of the tines assists in preventing the molluscs from passing through the gaps between the tines 267. As and when a tine 267 encounters an embedded object such as a rock, the resilience of the tine 267 allows it to bend and pass over the rock and return to its normal, flat panel shape. In addition, movement of the vessel increases the flow of water through the Drag 231 which assists with moving the molluscs into the collecting bag 262. A gap is present between the sweeper bar 255 and the bar to which the rings are connected through which denser objects such as stones without entering the collecting bag 262. Figures 5A to 5C show a fourth embodiment of the present invention. Figure 5A is a perspective view of a third embodiment of the present invention, Figure 5B is a front view of the third embodiment of the present invention and Figure 5C is a side view of the third embodiment of the present invention. The figures show a drag 331 with a tow bar assembly 333 which has a connecting hole 335 which allows the drag 331 to be connected directly to a trawler via a warp or by means of the arrangement shown below with reference to figure 6. Support means extend from the connector 335 to the front portion of the drag 339 to which they are fixedly connected in this embodiment of the present invention. The rear portion of the drag 341 has a bar from which a number of coaxial connecting rings project. The connecting rings 343 are positioned to accept a pole (not shown) which can be inserted through the rings 343 to attach the lower portion of the catch collecting net to the rear portion 341 of the drag 331.

The drag has two sides, the first side 345 and the second side 347. Both sides have a seabed engaging surface 349 which comprises a skid 349. In use, much of the weight of the drag is supported by the skids 349.

In this embodiment of the present invention, the sweeper 351 comprises a set of teeth or tines 367 each of which is mounted on a bar 263 by means of coil springs 265 which are wrapped around the bar 263. The tines extend downwards from the bar towards and are angled towards the direction of movement of the Drag 331 , in use, such that their free ends 357 are positioned at or slightly beyond the position of the skids when on the sea bed. The angle of the tines may assist in efficiently removing the molluscs from the sea bed and in moving them into the collecting bag.

The sweeper is securely attached to the Drag 331 at bar 363 and its resilience will allow the tines 367 to move back and forth when they encounter objects on the sea bed. In addition, the spring 365 allows the tines 367 to move in a transverse direction 369 which further assists with the process of catching molluscs.

In use, a collecting bag 362 having a heavy chain lower portion 363 and a lightweight twine upper portion 365 (shown partially in Fig 3C) is attached to the Drag 331 and the Drag 331 is connected to a fishing vessel in a standard way and is positioned on the sea bed. The vessel moves along the surface of the sea and pulls the Drag 331 along the sea bed. The free ends 357 of the tines 367 are positioned either level the skids 349 or protruding slightly beyond the skids 349 sweeps along the sea bed and collects molluscs that are sitting on the sea bed. The molluscs accumulate on the tines 367 and the direction of movement of the vessel causes the molluscs to be swept into the collecting bag. The transverse movement of the tines assists in preventing the molluscs from passing through the gaps between the tines 367. As and when a tine 367 encounters an embedded object such as a rock, the resilience of the tine 367 allows it to bend and pass over the rock and return to its normal, flat panel shape. In addition, movement of the vessel increases the flow of water through the Drag 331 which assists with moving the molluscs into the collecting bag 362. A gap is present between the sweeper bar 355 and the bar to which the rings are connected through which denser objects such as stones without entering the collecting bag 362.

Other resilient sweepers may be used which function in an equivalent manner to those disclosed herein.

Figure 6 shows the features of a typical dredge set up. The drags 411 are connected to the trawler via the trawl warp 403 which connects to a towing triangle 417. Four chain bridles 415 extend from the towing triangle 417 and are connected to a tow bar 419 which has a pair of bobbin wheels 421. The tow bar couples the chain bridles 415 to drags 411. One advantage of this arrangement is that a number of smaller Drags on a Tow bar are better able to cope with local undulations which may be found on the sea bed. With a larger single Drag such as the New Bedford design, the whole drag will always be at the highest point on the sea bed over which it is being pulled.

Consequently, molluscs may not be caught from areas of the sea bed below that point.

The present invention provides an improved Drag for collecting sea bed dwelling molluscs such as the Queen Scallop, the North Atlantic Sea Scallop, other types of Scallop, Sea Urchins and Sea Cucumbers.

In addition, the process of sweeping the sea bed with a resilient sweeper causes less damage to the sea bed and reduces the power required to pull the Drag along the sea bed.

Improvements and modifications may be incorporated herein without deviating from the scope of the invention.

Claims

1. A drag for harvesting seabed dwelling marine animals, the drag comprising: a towing bar assembly connectable to a vessel via a warp;

a drag frame having a front portion attached to the towing bar assembly and a rear portion which is attachable to a collection receptacle;

2. A drag as claimed in claiml wherein, the towing bar is connected to the first side member and to the second side member.

3. A drag as claimed in claim 1 or claim 2 wherein, the front portion is connectable to the upper part of a collecting net. 4. A drag as claimed in any preceding claim wherein, a rail extends around an upper part of the front portion and is connectable to the upper part of a collecting net.

5. A drag as claimed in any preceding claim wherein, the rear portion comprises a connector for attaching the lower part of the open end of a collecting net.

6. A drag as claimed in any preceding claim wherein, the first side is a continuous panel.

7. A drag as claimed in any preceding claim wherein, the second side is a continuous panel. 8 A drag as claimed inclaim 6 or 7 wherein the continuous panels act to funnel water through the drag which assists with the collection of molluscs and the separation of molluscs from heavier and denser objects such as stones. 9. A drag as claimed in any preceding claim wherein, the rear portion comprises connectors for attaching the lower part of an open end of the collecting net. 0. A drag as claimed in any preceding claim wherein, the sweeper fixed end is connected to a support member which is connected to the first side and the second side of the drag frame.

11. A drag as claimed in any preceding claim wherein, the free end of the sweeper allows the sweeper to resiliently bend/deform when it encounters an embedded object on in its path on the sea bed.

12. A drag as claimed in any preceding claim wherein, the sweeper extends from the fixed end perpendicular to the direction of travel in use.

13. A drag as claimed in any of claims 1 to 11 wherein, the sweeper extends from the fixed end at around 120° to the direction of travel in use.

14. A drag as claimed in any preceding claim wherein, the amount by which the sweeper extends beyond the lower seabed engaging surfaces of the first and second sides is adjustable.

15. A drag as claimed in any preceding claim wherein, the amount by which the sweeper extends beyond the lower seabed engaging surfaces of the first and second sides by moving the fixed end of the sweeper.

16. A drag as claimed in any preceding claim wherein, the sweeper comprises a continuous sheet or panel of resilient material.

17. A drag as claimed in any preceding claim wherein, the sweeper has an ultimate elongation of between 12 and 23 N/mm².

18. A drag as claimed in any preceding claim wherein, the sweeper has an ultimate elongation of up to 20% 19. A drag as claimed in any preceding claim wherein, the sweeper is made from a laminated rubber/canvas material.

20. A drag as claimed in any preceding claim wherein, the sweeper comprises a 5 ply rubber/canvas material.

21. A drag as claimed in claims 1 to 15 wherein, the sweeper comprises a plurality of spring mounted teeth mounted between the first side member and the second side member. 22. A drag as claimed in claim 21 wherein, the teeth are evenly spaced between the first side member and the second side member.

23. A drag as claimed in claim 21 or claim 22 wherein, the springs are configured to allow the teeth to move longitudinally and transversely with respect to the direction of travel.

24. A drag as claimed in claims 21 to 23 wherein, the spring is a coil spring mounted on the support member to allow transverse and longitudinal movement.

25. A drag as claimed in claim 24 wherein, transverse movement of the teeth allows them to narrow the effective distance between the teeth and to assist in sweeping up molluscs from the seabed. 26. A drag as claimed in any preceding claim wherein, the seabed engaging portion of the first and second side members comprises one or more wheel.

27. A drag as claimed in claims 1 to 25 wherein, the seabed engaging portion of the frame further comprises one or more track.