AU2017202948A1

AU2017202948A1 - Apparatus and method for gathering shellfish

Info

Publication number: AU2017202948A1
Application number: AU2017202948A
Authority: AU
Inventors: Lee P. Lim
Original assignee: Hotrocks Ltd
Current assignee: Hotrocks Ltd
Priority date: 2017-03-02
Filing date: 2017-05-03
Publication date: 2018-09-20

Abstract

The invention relates to an apparatus and method for gathering shellfish. Some existing apparatus and methods for gathering shellfish comprise the use of a fishing dredge, the frame of which digs into and is dragged through sand so that shellfish are dislodged and caught in a dredge net. It is a problem that use of a dredge may damage some shellfish when the frame cracks their shells during dredging, may damage a seabed ecosystem, and may catch some undersize shellfish. The invention aims to provide an apparatus and method for gathering shellfish where the apparatus is pulled along the seabed rather than through the sand and where shellfish are gathered when they move out of the sand rather than by a dredge scooping through the sand. The apparatus for gathering shellfish comprises a frame with a trailing net. The frame supports a fan. In use the apparatus is attached to a boat and pulled along the seabed. The activated fan creates a flow of water that disrupts seabed sand causing any buried shellfish to move out of the sand and into the net as the apparatus is pulled along. Undersize shellfish may pass through apertures in the frame and the net may also be sized to allow undersize shellfish to pass through the net. I-C- L

Description

Title

Apparatus and method for gathering shellfish.

Field of Invention

This invention relates to an apparatus and method for gathering shellfish, for example for gathering scallops or clams.

Background

It is known to gather shellfish using a fishing dredge. Typically the dredge comprises a metal frame with a trailing net attached. The dredge is attached to a boat, for example by a chain, is placed on a seabed and as the boat moves forward the frame digs into and is dragged through sand. The shellfish are dislodged and caught in the net.

It is a problem that some shellfish are damaged by the dredge when the frame cracks or crushes their shells during dredging, and dredging may cause damage to a seabed ecosystem generally. It is also a problem that some undersize shellfish are caught in the net. It is an object of a preferred embodiment of the present invention to go at least some way towards addressing these problems. While this object applies to the preferred embodiment, it should be understood that the object of the invention per se is not so limited and is simply to provide a useful choice. Any objects and advantages of the preferred embodiment should not be seen as limitations on claims that do not mention them.

The term “comprising” and derivatives thereof, eg “comprises”, if and when used herein in relation to a combination of features should not be taken as excluding the possibility that the combination may have further unspecified features. For example, a statement that an arrangement “comprises” certain parts does not mean that it cannot also, optionally, have additional parts.

Summary of Invention

According to one aspect of the invention there is provided apparatus for gathering shellfish comprising: • shellfish containment means; and • sand agitation means; the apparatus formed such that when in use apparatus can be moved along sand under a body of water while the agitation means causes a fluid to disrupt the sand and dislodge shellfish so that they are retained in the containment means.

Optionally the agitation means comprises a fan.

Optionally the agitation means comprises a pump.

Optionally the fluid comprises water immediately adjacent to the sand.

Optionally the fluid comprises a gas, for example pressurised air.

Optionally the containment means comprises a net.

Optionally the containment means comprises a cage.

Optionally the apparatus comprises a frame that supports the agitation means.

Optionally the net or cage is to the rear of the frame.

Optionally the shellfish comprise scallops.

Optionally the agitation means is such that it causes the scallops to swim upwards so that they are retained in the containment means.

Optionally the shellfish comprise clams.

Optionally the apparatus comprises a frame supporting a fan and a net, the fan being directed downwards, and the net being at a rearwards positon with respect to the rest of the apparatus.

According to a further aspect of the invention there is provided a method of gathering shellfish comprising: • moving apparatus along sand under a body of water, the apparatus comprising shellfish containment means and sand agitation means; • causing the agitation means to disrupt sand such that shellfish are exposed and move upwards; • capturing the shellfish in the containment means by reason of forward movement of the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

Some preferred forms of the invention will now be described by way of example and with reference to the accompanying drawings, of which:

Figure 1 is a perspective view of a fishing aid; and

Figure 2 is an alternative perspective view of the aid.

Detailed Description

Referring to figures 1 and 2, the aid 1 is for use in gathering scallops, surf clams or other shellfish. It has a frame 2 supporting a fan 3 and a trailing net 8 (shown in figure 2). The frame 2 is approximately 2-3 metres in length, approximately 1-1.5 metres in width, and approximately 0.5-1 metre in height and is comprised of stainless steel but could be formed from any other suitable material.

The frame 2 has a projecting prow 4, a steel plate 5 that wraps a short way under a base of the frame 2, and barred walls that create a series of apertures 6. The apertures 6 are about 100 to 150 mm in length and are sized to permit undersize shellfish to pass through. The base of the frame 2 defines an open space 7.

The fan 3 is designed to operate in depths of up to 20 metres, and is sufficiently powerful to stir up seabed sand in use. In other embodiments of the invention the fan may be substituted with a fluid pump or some other way of disrupting the sand, and/or the net 8 may be substituted by a cage or some other arrangement for holding the shellfish.

Referring to figure 2, the fan 3 is attached to the frame 2 at a preferred angle of about 45 degrees with respect to the base. In preferred embodiments the aid may incorporate a facility for adjusting the angle, for example between about 25 degrees and 70 degrees. A method using the apparatus of the present invention involves the aid 1 being dragged along the surface of the seabed, with buried shellfish being dislodged and caught through agitation of the sand by the action of the fan 3 rather than by scooping through the sand. As such, the invention aims to mitigate the risk of damaging the shellfish and/or the seabed.

In the preferred form of the present invention the aid 1 is readied for use by attaching a line, for example a chain or rope (not shown), to the prow 4 at one end and to a boat (not shown) at the other end. For stability there may be additional support lines attached between each front side of the frame 2 and the line. The net 8 is fixed to the rear 2a of the frame.

In use the boat is positioned at sea beyond the surf line in an area where the seabed is relatively flat and sandy and at a depth of up to about 15 metres. The fan 3 is activated and the frame 2, with net 8 and line attached, is lowered over the side of the boat so that it settles on the seabed.

The boat then travels in one direction so that the slack on the line is taken up and the aid 1 is pulled along the seabed at a speed of about 4 knots. The curved front of the frame 2 and the steel plate 5 assist in keeping the aid 1 running relatively smoothly along the seabed and in preventing it from substantially digging into the sand as some prior art fishing dredges do.

The movement of the fan 3 creates a flow of water that disrupts the seabed sand causing any buried shellfish to move out of the sand and into the open space 7 of the frame 2. In the case of scallops, the flow of water dislodges each scallop which will "swim” away from the disrupted sand by compressing the valves of its shell to force water backwards past the shell hinge, propelling the scallop up into the open space 7. A buried clam or other shellfish that does not “swim” will be dislodged by the flow of water and will be moved into the open space 7 by the flow of water.

As the aid 1 is pulled by the boat the shellfish that were buried pass through the open space 7 into the net 8. Smaller shellfish may pass out the sides of the aid 1 as the apertures 6 are sized to allow them to. Larger shellfish will not fit through the apertures 6 and will tend to pass into the net 8. In the preferred embodiment, the net apertures are also sized to allow shellfish below a certain size to pass through while trapping larger shellfish.

After the boat has pulled the aid 1 for a predetermined distance or amount of time, it will stop and the aid 1 will be pulled into the boat by hand or winch. Any shellfish caught in the net 8 are measured and those of legal size are kept. Any undersize shellfish are returned to the sea. The method can then be repeated.

The apparatus and method of the invention may also be used on a lakebed or riverbed depending on the variety of shellfish being gathered.

While some preferred forms of the invention have been described by way of example it should be appreciated that modifications and improvements can occur without departing from the scope of the appended claims.

Claims

Claims

1. Apparatus for gathering shellfish, comprising: • shellfish containment means; and • sand agitation means; the apparatus formed such that when in use the apparatus can be moved along sand under a body of water while the agitation means causes a fluid to disrupt the sand and dislodge shellfish so that they are retained in the containment means.
2. Apparatus for gathering shellfish according to claim 1, wherein the agitation means comprises a fan.
3. Apparatus for gathering shellfish according to claim 1, wherein the agitation means comprises a pump.
4. Apparatus for gathering shellfish according to claim 1,2 or 3, wherein the fluid comprises water immediately adjacent to the sand.
5. Apparatus for gathering shellfish according to any one of claims 1, 2 or 3, wherein the fluid comprises a gas.
6. Apparatus for gathering shellfish according to claim 5, wherein the gas comprises pressurised air.
7. Apparatus for gathering shellfish according to any one of the preceding claims, wherein the containment means comprises a net.
8. Apparatus for gathering shellfish according to any one of claims 1 -6, wherein the containment means comprises a cage.
9. Apparatus for gathering shellfish according to any one of the preceding claims, comprising a frame that supports the agitation means.
10. Apparatus for gathering shellfish according to any one of claims 7-9, wherein the net or cage, as the case may be, is to the rear of the frame.
11. Apparatus for gathering shellfish according to any one of the preceding claims, wherein the shellfish comprise scallops.
12. Apparatus according to claim 11, wherein the agitation means is such that it causes the scallops to swim upwards so that they are retained in the containment means.
13. Apparatus for gathering shellfish according to any one of claims 1-10, wherein the shellfish comprise clams.
14. Apparatus for gathering shellfish according to claim 1, comprising a frame supporting a fan and a net, the frame having a projecting prow, a curved steel plate that wraps a short way under a base of the frame, and barred walls that create a series of apertures sized to permit undersize shellfish to pass through, the fan being directed downwards, and the net being at a rearwards positon with respect to the rest of the apparatus, the net being sized to permit undersize shellfish to pass through.
15. Apparatus for gathering shellfish according to claim 1, substantially as herein described.
16. A method of gathering shellfish comprising: • moving apparatus according to claim 1 along sand under a body of water; • causing the agitation means to disrupt sand such that shellfish are exposed and move upwards; • capturing the shellfish in the containment means by reason of forward movement of the apparatus.
17. A method of gathering shellfish according to claim 16, wherein the agitation means comprises a fan.
18. A method of gathering shellfish according to claim 16, wherein the agitation means comprises a pump.
19. A method of gathering shellfish according to claim 16, 17 or 18, wherein the fluid comprises water immediately adjacent to the sand.
20. A method of gathering shellfish according to any one of claims 16, 17 or 18, wherein the fluid comprises a gas.
21. A method of gathering shellfish according to any one of claims 16-20, wherein the containment means comprises a net.
22. A method of gathering shellfish according to any one of claims 16-20, wherein the containment means comprises a cage.
23. A method of gathering shellfish according to any one of claims 16-22, wherein the apparatus comprises a frame that supports the agitation means.
24. A method of gathering shellfish according to any one of claims 21-23, wherein the net or cage, as the case may be, is to the rear of the frame.
25. A method of gathering shellfish according to any one of claims 16-24, wherein the shellfish comprise scallops.
26. A method of gathering shellfish according to claim 25, wherein the sand disruption caused by the agitation means causes the scallops to swim upwards so that they are retained in the containment means.
27. A method of gathering shellfish according to any one of claims 16-24, wherein the shellfish comprise clams.
28. A method of gathering shellfish substantially herein described with reference to the accompanying drawings.